Mobile Ad-hoc and Sensor Networks

In this paper, we propose an overlapping communication protocol using improved time-slot leasing in the Bluetooth WPANS. One or many slave-master-slave communications usually exist in a piconet of the Bluetooth network. A fatal communication bottleneck is incurred in the master node if many slave-master-slave communications are required at the same time. To alleviate the problem, an overlapping communication scheme is presented to allow slave node directly and simultaneously communicates with another slave node to replace with the original slave-master-slave communication works in a piconet. This overlapping communication scheme is based on the improved time-slot leasing scheme. The key contribution of our improved time-slot leasing scheme additionally offers the overlapping communication capability and we developed an overlapping communication protocol in a Bluetooth WPANs. Finally, simulation results demonstrate that our developed communication protocol achieves the performance improvements on bandwidth utilization, transmission delay time, network congestion, and energy consumption.

The IEEE 802.15.3 WPAN(Wireless Personal Area Network) has been designed to provide a very high-speed short-range transmission capability with QoS provisions. Its unidirectional channel allocations for the guaranteed time slots, however, often result in a poor throughput when a higher layer protocol such as TCP requires a full-duplex transmission channel. In this paper we propose a mechanism, called

TCP transfer mode

, that provides the bidirectional transmission capability between TCP sender and receiver for the channel time allocations(CTAs) of the high-rate WPAN. As our scheme does not require additional control messages nor additional CTAs, the throughput of a TCP connection on the high-rate WPAN can be greatly improved. Our simulation results show that the proposed scheme outperforms any possible ways of TCP transmission according to the current standard of the WPAN.

A novel architecture and multi-hop protocol to support intervehicular communication is proposed. The protocol uses ‘latency’ as a metric to find routes. We introduce the concept of a Routing Server (RS), which tries and keeps up-to-date information about the state of the network, i.e. the network topology, and the latency associated at each node averaged over a short time. Route discovery is now carried out by sending a Route Request packet directly to the RS, rather than flooding the network. We call this model ‘Server Supported Routing (SSR)’. A simulation study is carried and the performance of SSR compared with Dynamic Source Routing (DSR) protocol. It is found that SSR performs better than DSR over longer hops, faster rate of topology change, and high offered load in the network. The study also reveals that DSR is much more sensitive to changes in the network than SSR.

Sensor networks, consisting of sensor devices equipped with energy-limited batteries, have been widely used for surveillance and monitoring environments. Data collected by the sensor devices needs to be extracted and aggregated for a wide variety of purposes. Due to the serious energy constraint imposed on such a network, it is a great challenge to perform aggregate queries efficiently. This paper considers the aggregate query evaluation in a sensor network database with the objective to prolong the network lifetime. We first propose an algorithm by introducing a node capability concept that balances the residual energy and the energy consumption at each node so that the network lifetime is prolonged. We then present an improved algorithm to reduce the total network energy consumption for a query by allowing group aggregation. We finally evaluate the performance of the two proposed algorithms against the existing algorithms through simulations. The experimental results show that the proposed algorithms outperform the existing algorithms significantly in terms of the network lifetime.

Nodes in wireless sensor networks have very limited storage capacity, computing ability and battery power. Node failure and communication link disconnection occur frequently, which means weak services of the network layer. Sensing data is inaccurate which often has errors. Focusing on inaccuracy of the observation data and power limitation of sensors, this paper proposes a sampling frequency control algorithm and a data compression algorithm. Based on features of the sensing data, these two algorithms are combines together. First, it adjusts the sampling frequency on sensing data dynamically. When the sampling frequency cannot be controlled, data compression algorithm is adopted to reduce the amount of transmitted data to save energy of sensors. Experiments and analysis show that the proposed sampling control algorithm and the data compression algorithm can decrease sampling times, reduce the amount of transmitted data and save energy of sensors.

This paper proposes the concept of information exposure for a point and for a path based on estimation theory. The information exposure of a point is defined as the probability that the absolute value of estimation error is less than some threshold; and the information exposure for a path is the average information exposure of all points along the path. The higher the information exposure, the higher the confidence level that some information of a target is exposed and the better the target is monitored. An approximation algorithm is proposed to solve the problem of finding the worst (best) information exposure path in wireless sensor networks, and its performance is evaluated via simulations. Furthermore, a heuristic for adaptive sensor deployment is proposed to increase the information exposure of the worst information exposure path.

Security issues are always difficult to deal with in mobile ad hoc networks. People have seldom studied the costs of those secure schemes respectively and for some secure methods designed and adopted before-time, their effects are often investigated one by one. In fact, when facing certain attacks different methods would response individually and it would result in some waste of resource, which may be worthless from the viewpoint of whole network. Making use of the cost management idea, we analyze the costs of secure methods in mobile ad hoc networks and introduce a secure framework. Under the framework not only the network systems own tasks can be finished in time but also the whole network’s security costs can be decreased. We discuss the process of security costs computation at each mobile node and in certain nodes groups. We then exemplify the DoS attacks and costs computation among defense methods. The results show that more secure environment can be achieved based on the framework in mobile ad hoc networks.

In 2003, Lin et al. proposed an improvement on the OSPA (optimal strong-password authentication) scheme to make the scheme withstand the stolen-verifier attack, using smart card. However, Ku et al. showed that Lin et al.’s scheme is vulnerable to the replay and the denial of service attack. In 2004, Chen et al. proposed a secure SAS-like password authentication schemes. Their schemes can protect a system against replay and denial-of-service attacks. In this paper, we propose two efficient and secure password authentication schemes which are able to withstand replay and denial-of-service attacks. The proposed schemes are more efficient than Chen et al.’s schemes in computation costs. Moreover, the proposed schemes can be implemented on most of target low-power devices such as smart cards and low-power Personal Digital Assistants in wireless networks.

Existing techniques for IP address autoconfiguration in mobile ad hoc networks (MANETs) do not address security issues. In this paper, we first describe some of the existing IP address autoconfiguration schemes, and discuss their security shortcomings. We then provide solutions to these security issues based on the use of trust models. A specific trust model is also proposed for use in improving the security of existing IP address autoconfiguration schemes.

Anycast allows a group of nodes to be identified with an anycast address so that data packets destined for that anycast address can be delivered to one member of the group. An approach to anycast routing in mobile ad hoc networks is presented in the paper. The approach is based on the Ad Hoc On-demand Distance Verctor Routing Protocol (AODV) and is named AODVA Anycast Routing Protocol (AODVA). AODVA extends AODV’s basic routing mechanisms such as on-demand discovery and destination sequence numbers for anycast routing. Additional mechanisms are introduced to maintain routes for anycast addresses so that no routing loops will occur. Simulations show that AODVA achieves high packet delivery ratios and low delivery delay for data packets destined for anycast addresses.

Energy efficiency is of vital importance for wireless ad hoc networks (WANETs). In order to keep the nodes active as long as possible, it is essential to maximize the lifetime of a given multicast tree. However, hop count is generally an important metric for WANETs, and any efficient routing protocol should have low hop count. The problem of generating the optimized energy efficient routing protocol for WANETs is NP-hard. Any workable heuristic solution is, therefore, highly desirable in this case. To take into account the tradeoff between the lifetime and the hop count in routing of multicast tree in WANETs, this paper defines a new metric termed energy efficiency metric (EEM) function. Theoretical analyses show that it is efficient to fully characterize the energy efficiency of WANETs. A distributed routing algorithm called Maximum Lifetime and Minimum Hop-count (MLMH) is then proposed with the aim that extends the lifetime while minimizes the maximal hop count of a source-based multicast tree in WANETs. Simulation results give sound evidence that our algorithm achieves a balance between the hop count and the lifetime of the multicast tree successfully.

In this paper, we propose a Multicast Routing Protocol termed ZBMRP (Zone Based Multicast Routing Protocol) for Mobile Ad Hoc Networks (MANETs). ZBMRP applies on-demand procedures to dynamically establish mesh-based multicast routing zones along the path from the multicast source node to the multicast receivers. Control packet flooding is employed inside multicast zones, thus multicast overhead is vastly reduced, and good scalability can be achieved. It will also be easier to secure multicast routing. ZBMRP fits well for MANETs where bandwidth is limited, topology changes frequently, power is constrained and security problem is serious. Simulation results are presented to support our claim.

The main goal of wireless sensor networks is to collect information from the target environment through a large number of micro sensor nodes. However, the constrained resource on each senor node brings great challenges to the information processing procedure in sensor networks. An overview and some open issues of the intelligent information processing approaches in wireless sensor networks are given in this paper to meet these challenges, which include in-network data aggregation and data compression algorithms, distributed database storage and query strategies, and multi-sensor data fusion rules. The advantages and disadvantages of every approach are also discussed.

Wireless sensor networks promise a new paradigm for gathering data via collaboration among sensors spreading over a large geometrical region. Many real-time applications impose stringent delay requirements and ask for time-efficient schedules of data aggregations in which sensed data at sensors are combined at intermediate sensors along the way towards the data sink. The

Minimum Data Aggregation Time

(MDAT) problem is to find the schedule that routes data appropriately and has the shortest time for all requested data to be aggregated to the data sink.

In this paper we study the MDAT problem with uniform transmission range of all sensors. We assume that, in each time round, data sent by a sensor reaches exactly all sensors within its transmission range, and a sensor receives data if it is the only data that reaches the sensor in this time round. We first prove that this problem is NP-hard even when all sensors are deployed a grid and data on all sensors are required to be aggregated to the data sink. We then design a (Δ–1)-approximation algorithm for MDAT problem, where Δ equals the maximum number of sensors within the transmission range of any sensor. We also simulate the proposed algorithm and compare it with the existing algorithm. The obtained results show that our algorithm has much better performance in practice than the theoretically proved guarantee and outperforms other algorithm.

In mobile wireless sensor networks, sensors move in the monitored area at any direction and at any speed. Unlike many other networking hosts, sensor nodes do not have global addresses. Very often they are identified by using a location-based addressing scheme. Therefore, it is important to have the knowledge of the sensor location indicating where the data came from. In this paper, we design three mobility-pattern based localization update algorithms. Specifically, we divide sensor movements into three states,

Pause

,

Linear

, and

Random

. Each state adopts different localization update algorithms. Analytical and simulation results are provided to study the localization cost and location accuracy of the proposed localization-update algorithm in different mobility patterns. The analysis to these results indicates that the localization cost is minimized and the location accuracy is improved.

Time synchronization is a critical topic in wireless sensor networks for its wide applications, such as data fusion, TDMA scheduling and cooperated sleeping, etc. In this paper, we present an accurate time synchronization (ATS) algorithm using linear least square for sensor networks. Unlike the previous protocols, all nodes aren’t synchronized to some reference nodes or sink node, but to a virtual clock. Moreover, each pair of the nodes are synchronized each other. The main advantage of ATS is simple and accurate. The variance of the synchronized drift error is no more than D

s

*

δ

/ 2

β

2

, where D

s

is the depth of the network,

δ

is the maximal variance of the link delay and

β

is the sampling interval. The experiments show the high precision compared with the previous algorithms.

Mobile ad hoc networks can be formed by a group of wireless nodes without requiring the use of any preexisting infrastructure. Therefore nodes of such networks can not assume which services exist and where they are hosted. A service discovery protocol that provides automatic discovery of desired services is particularly important to save user from the trouble of configuration and quick access to services. Recently, a service discovery protocol that uses broadcast and introduces the cache function has been proposed. There was a problem of the number of messages increasing with the increase in the number of clients which performs a service discovery request, and becoming the cause of congestion. In this paper, we propose a new service discovery protocol for mobile ad hoc networks, which is characterized by service provision groups and their dynamic reconfiguration for the purpose of reducing the number of control messages, and a simulation study is presented to show the effect of the proposed protocol.

The growing advance in wireless communications and electronics makes the development of low-cost and low-power sensors possible. These sensors are usually small in size and are able to communicate with other sensors in short distances wirelessly. A sensor network consists of a number of sensors which cooperates with one another to accomplish some tasks. In this paper, we address the problem of resource inventory applications, which means a class of applications involving population calculation of a specific species or object type. To reduce energy consumption, each sensor only reports the number of sensed objects to the server, and the server will estimate the object number according to the received reports of all sensors. To address this problem, we design in this paper a population estimation algorithm, called algorithm Estimation, to estimate the object numbers. Several experiments are conducted to measure the performance of algorithm Estimation. The experimental results show that algorithm Estimation is able to obtain closer approximations of object numbers than prior algorithms.

Broadcast data dissemination is well-suited for mobile wireless environments, where bandwidth is scarce, and mutual interference must be minimized. However, broadcasting monopolizes the medium, precluding clients from performing any other communication. We address this problem in two ways. First, we segment the server broadcast, with intervening periods of silence, during which the wireless devices may communicate. Second, we reduce the average access delay for clients using a novel cooperative caching scheme. Our scheme is fully decentralized, and uses information available locally at the client. Our results show that our model prevents the server from monopolizing the medium, and that our caching strategy reduces client access delays significantly.

Broadcasting in short-range wireless ad hoc networks is a key issue. Currently, these networks can be formed not only by computer hosts with full PC functionalities, but also by small communicating objects. Hence energy-efficiency becomes a big challenge for broadcasting protocols. To design an energy-efficient broadcasting protocol, an energy model should be defined to evaluate protocols performances. Nevertheless, all the performance evaluations are based on a one-to-one energy model without taking into account the wireless multicast advantage: such a model is not able to describe correctly the energy consumption in a broadcast. In this paper, we propose to use a more realistic one-to-all energy model to quantify the broadcast cost. By applying this model to the main broadcasting protocols, we will discuss how a range adjustment technique takes effect. We will also show that in a broadcast, a range adjustment provides a trade-off between the number of rebroadcasts and the number of nodes touched by each rebroadcast. It is through this trade-off that a broadcasting protocol can achieve energy-efficiency.

Based on existing reliable broadcast protocols in MANETs, we propose a novel reliable broadcast protocol that uses clustering technique and gossip methodology. We combine local retransmission and gossip mechanisms to provide reliability in MANETs. The proposed protocol can dynamically change system parameters for reliable broadcast communication in order to improve the adaptability in the rapidly changing network environment. In our proposed protocol, the adaptive gossip probability is explored to make the protocol insensitive to changing environment. In sparse or boundary areas, a large gossip probability is adopted in order to improve the reliability; while in dense or inner areas, a small gossip probability is used to alleviate the contention and collision. Theoretical analysis shows that the proposed protocol has high delivery ratio and low end-to-end delay for broadcasting.

There are three approaches to disseminate queries into the sensor network, which are the multi-hop unicast, full flood and geocast. Since the energy is very limited resource of the sensor network, query optimizer must select an optimal approach consuming minimum energy to disseminate the query into the sensor network. As the selection relies on energy consumption estimation, the accuracy of the energy consumption estimation is very critical for query processing in sensor network. In this paper, a general energy consumption estimation model is proposed. Compared with other models, our model takes both routing protocol and MAC protocol into consideration. In experiments we compared our energy model’s estimation for the multi-hop unicast, full flood and geocast with simulation results. Results showed that our model’s accuracy is very high.

With the goal to make the wireless sensor network nodes small in size, light in weight, cheap in cost, as well as low in power consumption, projects have been carried out to study the hardware and software co-design and to develop sensor node SOC technology. We have proposed a general “sensor node on a chip” approach, namely EasiSOC, with two typical SOC architectures for different application areas. The first architecture of sensor node supports basic functionalities which performs relatively simple tasks with fixed routines. The second architecture of sensor node favors complex functionalities and advanced jobs. Current research progresses on the development of the first SOC structures are also introduced.

The performance of wireless sensor networks depends largely on the deployment of sensor nodes as well as their lifetime mainly determined by the energy consumption. Most current attention, however, has been paid to energy-efficient deployment. With the goal of facilitating further evolution of wireless sensor networks, recently proposed deployment schemes for wireless sensor networks are surveyed. The focus is on coverage and connectivity, which are regarded as the most important respects of network performance and energy-efficiency. Depending on the application and different actions in the network, coverage issues are classified into static and dynamic ones, while connectivity issues into pure connectivity and routing algorithm based connectivity. An overview of each of these areas is presented, and the performance of existing methodologies is discussed. In order to spark new interests and developments in this field, some crucial open issues are pointed out.

The mobility of sink and stimulus brings a huge challenge to WSN. It wishes that the location update packets be continuously transmitted through the sensor network to keep the data path between the sink and the source node sensing the stimulus. Unfortunately, frequent location update packets would not only result in excessive energy consumption of sensor node with highly energy constraint, but also increase the communication collision in wireless propagation. In this paper we propose a novel Geographical Cellular-like Architecture (GCA) for WSN, which can efficiently manage the mobility of both sink and stimulus. GCA proactively builds a cellular-like structure assisted by the geographical location of each node, where each cell includes a header and several members. The header acts as the role of base station in cellular network, receiving the information from sink and forwarding the data report; the members just take charge of watch-ing the target. Meanwhile, the hierarchical design of GCA can also save energy remarkably. The performance of GCA is evaluated through analysis and the simulation in ns2, which demonstrates that GCA is an efficient solution to mobility in WSN.

Application reconfiguration provides a powerful mechanism to adapt component-based distributed applications for changed environmental conditions. In this paper, we propose an effective environment adaptive application reconfiguration (EAAR) mechanism based on the feedback-loop concept of the control theory. Based on this mechanism, a pull-based paradigm is introduced to represent the sensing-judging-acting process in sensor networks. We utilize rule-based knowledge to analyze the change of environment, thus perform self-adaptive application reconfiguration efficiently. To demonstrate how EAAR mechanism works, we simulated a scenario of reconfiguring applications in sensor networks.

Mobile Ad Hoc networks (MANET) are composed of a group of wireless mobile nodes that can communicate with each other. Different from normal networks, MANET is easy to be attacked. The attacking to the protocol can paralyze the network, so the security of routing protocol is an important part of the Ad Hoc networks security. This paper proposes a secure on-demand routing protocol SDSR. It uses digital signature and node monitoring to ensure security. It can protect route information from many kinds of attacks, and has good network performance as well.

Evolving networks of wireless sensing nodes have many attractive applications. Localization, that is to determine the locations of sensor nodes, is a key enabler for many applications of sensor networks. As sensor networks move closer to extensive deployments, security becomes a major concern, resulting in a new demand for secure localization and location proving systems. In this paper, we propose a secure localization system based on a secure hop algorithm. A location verification system that allows the base station to verify the locations of sensor nodes is also presented. It prevents a node from falsifying reported location information. The evaluation of the secure localization system shows that the proposed scheme performs well under a range of scenarios tested and is resilient against an attacker creating incorrect location information in other nodes.

Mobile ad hoc network (MANET) has been generally regarded as an ideal network model for group communications because of its specialty of instant establishment. However, the security of MANET is still a challenge issue. Although there are some existing security schemes such as ARAN (Athenticated Routing for Ad hoc Networks) protocol that makes use of cryptographic certificate to provide end-to-end authentication during routing phases, the overhead of security computation is still a serious hurdle for real application. In this paper, we propose a comparatively efficient scheme to perform ARAN protocol, based on AODV, by using one-time signature in place of conventional signature, aiming at achieving the same level of security but improved efficiency.

Ad-hoc networks are characterized by open medium dynamic topology distributed cooperation and constrained capability. These characteristics set more challenges for security. If the routing protocol is attacked, the whole network would have been paralyzed. As a result, routing security is the most important factor in the security of the entire network. However, few of current routing protocols have the consideration about the security problems. The potential insecure factors in the AODV protocol are analyzed. Furthermore, a security routing protocol based on the credence model is proposed, which can react quickly when detecting some malicious behaviors in the network and effectively protect the network from kinds of attacks.

Undirected double-loop networks

G

(

n

; ±

s

1

, ±

s

2

), where

n

is the number of its nodes,

s

1

and

s

2

are its steps, 1 ≤ 

s

1

 < 

s

2

 < 

n

/ 2 and gcd(

n

,

s

1

,

s

2

)=1, are important interconnection networks. In this paper, by using the four parameters of the L-shape tile and a solution (x̄,ȳ) of a congruence equation

s

1

x

 + 

s

2

y

 ≡ 1 (

mod

n

), we give a constant time optimal routing algorithm for

G

(

n

; ±

s

1

, ±

s

2

).

Using directional antennas in wireless ad hoc networks is an attractive issue due to its potential advantages such as spatial reuse, low power consumption and low chance of interference. To acquire these advantages, we propose a new routing scheme called DAPOS (Directional Antenna based Path Optimization Scheme). The proposed scheme enables us to acquire an efficient path by considering the characteristics of directional antennas, resulting a routing performance improvement. DAPOS focuses on shortening the length of routing path gradually by considering the higher gain of directional antennas at a receiver side. Simulation results show that DAPOS significantly reduces the number of hops in route, thereby it improves the overall network performance.

As the need for a solution to support mobile network is consistently increasing, NEtwork MObility (NEMO) Basic Support protocol is proposed by using a bi-directional tunnel between a Mobile Router (MR) and its Home Agent (HA). However, the multiple levels of MR-HA tunnels in nested mobile networks lead to significant suboptimal routing, called pinball routing. In this paper we propose a Route Optimization (RO) scheme based on improved Prefix Delegation in order to pass ingress filtering. In an effort to provide the RO based on the improved procedure, it performs an address translation mechanism and a registration procedure to inform other nodes of an optimal path. The proposed scheme supports nested mobile networks without requiring additional tunneling, thus reducing packet overhead and latency with regard to the NEMO basic solution. We evaluate the proposed scheme with previous schemes by analytical models. According to the results, our newly proposed scheme shows 20% and 50% of performance improvements for the worst case and the best case, respectively.

Internetworking mobile ad-hoc networks (MANETs) with the Internet has been a hot issue for many years. However, most researches have been concentrated on the use of MANETs as the access networks for the Internet. This paper introduces another use of MANETs: backup or load-balancing transit networks for the Internet. To achieve this goal, a scalable, stable, low-overhead, QoS-support ad-hoc routing architecture with the address auto-configuration is required. Moreover, how an Internet gateway selects an external route via MANETs to another autonomous system (AS) also needs to be solved. In this paper, BGP-GCR+, a combination of the border gateway protocol (BGP), the gravitational cluster routing (GCR), and the passive/weak IPv6-based address stateless auto-configuration, is developed towards the standards to achieve the required functions.

In current routing protocols in ad hoc networks, a source node unnecessarily re-discovers the whole path when just one node moves, even if the rest of path needs not to be re-arranged. The time for re-discovery of the whole path may often take too long and affects the network efficiency adversely. In this paper, a local repair scheme has been proposed, where the source node recovers the route breakage caused by a shifting of node with an aid of adjacent node instead of re-routing the whole path. Adjacent nodes are under operation in adaptive promiscuous mode. Consequently, the proposed scheme has advantages in shortening the recovery time of the route breakage and in minimizing the energy consumption under promiscuous mode. The ns-2.27 simulator has been utilized for the evaluation of the proposed scheme.

Sensor networks consisting of nodes with limited battery power and wireless communications is among the fastest growing technologies. There are many challenges in implementation of such systems: energy dissipation and data gathering being one of them. Gathering sensed information in an energy efficient manner is critical to operate the sensor network for a long period of time. While cluster-based data collection is efficient at energy and bandwidth, it’s difficult to ensure balanced energy depletion on all cluster-members after a longtime run. In this paper we propose a new distributed cluster-based data gathering algorithm using PSO to optimize clustering process. The election of cluster-heads need synthetically consider the state information including location and energy reserved about candidates and their neighbors. Our preliminary simulation results show that the proposed algorithm balances the energy dissipation over the whole network thus prolongs the network lifetime.

Microsensor nodes, charged with battery power and capable of wireless communications, are distributed around to survey the environments and send the needed data to the base station periodically. The limited energy resources are consumed in both communication and computation – especially in communication. To reduce such power consumption, this paper presents a new data gathering scheme based on the hypercube topology for microsensor networks. By gathering data from all nodes to the base station through the communication tree in the constructed hypercube, the new scheme is able to shorten communication delay by parallel transmissions and to replace dead nodes through reconfiguration. Simulation results show that compared with other data gathering schemes, the proposed hypercube-based scheme brings up favorable results, including reduced transmission delay, balanced energy loads, satisfying system scalability and as a result prolonged system lifetime. To complete our investigation, the distributed approach for constructing a hypercube and a binary tree for data gathering are also proposed.

Data gathering is a very important functionality in sensor networks. Most of current data gathering researches have been emphasized on issues such as energy efficiency and network lifetime maximization; and the technique of data aggregation is usually used to reduce the number of radio transmissions. However, there are many emerging sensor network applications with different requirements and constraints. Rather, they are time critical, i.e., delivering sensed information of each individual sensor node back to a central base station quickly becomes most important. In this paper, we consider collision-free delay efficient data gathering problem in sensor networks, assuming that no data aggregation happens in intermediate nodes. We formally formulate this problem and propose optimal and near-optimal algorithms for different topologies. Particularly, in general topology, we present two approximation algorithms with performance ratio of 2 and 1+1/(

k

+1), respectively.

This paper proposes a localized recursive estimation scheme for parameter estimation in wireless sensor networks. Given any parameter occurred at some location and time, a number of sensors recursively estimates the parameter by using their local measurements of the parameter that is attenuated with the distance between a sensor and the target location and corrupted by noises. Compared with centralized estimation schemes that transmit all measurements to a sink (or a fusion center), the recursive scheme needs only to transmit the final estimate to a sink. When a sink is faraway from the sensors and multihop communications have to be used, using localized recursive estimation can help to reduce energy consumption and reduce network traffic load. Furthermore, the most efficient sequence of sensors for estimation is defined and the necessary condition for such a sequence is determined. Some numerical examples are also provided. By using some typical industrial sensor parameter values, it is shown that recursive scheme consumes much less energy when the sink is three hops or more faraway from the local sensors.

Recently, Radio Frequency IDentification(RFID) technology has come to maturity such that numerous applications in many industries have been devised and implemented in the real world. In the conventional RFID application, the reader is located at some place without motion, periodically polling the nearby RFID tags. However, the emerging

Mobile RFID

technology [1]provides the user with the mobile RFID reader function by installing it into the portable wireless device like cellular phone or PDA so that he can access the spontaneous RFID-attached object information by approaching the device to RFID tag and triggering the information acquisition operation. Since the information service is immediately offered at any time and place, the whole service domain of mobile RFID is broader than that of conventional RFID. Currently, many commercial applications and their service senarios are developed and standardized in the mobile RFID Forum [1].

In this paper, we propose a new concept called as

mobile USN (Ubiquitous Senser Network)

, the next-generation version of the newly emerging ubiquitous technologies like mobile RFID and NFC(Near Field Communication) [2]. The effective working range of mobile RFID(NFC) is limited within 1

m

(10

cm

) from the mobile(NFC) phone. This problem can be relieved by adopting RF transmission chip like CC2420 ZigBee RF Tranceiver [3] into the phone. By this upgrade, the effective working range is enlarged to 30-100

m

so as to invite much more diverse ubiquitous services into realization.

Then, we study energy saving issue in the data delivery from USN tag to phone. In mobile USN, USN phone is in charge of collecting the sensing and event data occuring at the nearby USN tags(that are USN version of RFID tags). However, since USN tag must be equipped with battery to support the active data acquisition, power-saving becomes the fundamental problem in achieving the commercial success of mobile USN. In particular, we introduce three asynchronous power-saving communication protocols. Finally, we study the energy efficiency and QoS aspects of three protocols.

This paper proposes an efficient authentication protocol for wireless networks based on group and non-group cellular automata (CA). Most previous protocols employed typical cryptosystems such as symmetric and asymmetric encryptions in spite of their high computation and communication cost. In addition, previous protocols are problematic in that the mobile user copies his/her anonymous ticket and shares it with friends. We propose an efficient and secure authentication protocol which provides a mobile user’s anonymity and which has a low computation cost to withstand the above weakness without employing any typical cryptosystems.

In this paper, we propose SeGrid, a secure grid infrastructure for large scale sensor networks. The basic idea relies on the availability of a low-cost public cryptsystem (e.g. Blom’s key management scheme [4]) that can be used for shared key computation between the source and the destination, as long as the public shares are known to each other. In SeGrid, each sensor resides in a grid computed from its physical location. Within a grid, one or a few number of sensors, with one of them the grid head, are active at any instant of time and all other sensors fall asleep for energy conservation. We intend to compute a shared key for two grids instead of two nodes, such that the grid heads can securely communicate with each other. The public shares of a grid are stored at designated locations based on our public share management protocol such that the closer two grids, the shorter distance to obtain each other’s public shares. We instantiate SeGrid based on Blom’s key management scheme [4] to illustrate the computation of a grid key. To our best knowledge, this is the first work that simultaneously considers both key management and network lifetime extension, which explores along the dimension of network density.

Systems that track sensed data trigger alerts based on the evaluation of some condition. In the presence of loss data a conservative condition may not generate a necessary alert and an aggressive condition may generate an alert that could have never happened. We observe that some lost values can be predicted and suggest new classes of conditions that provide more accurate alerts. We motivate the use of such conditions, provide a method for comparing two condition systems, and investigate the systems’ properties in both replicated and non replicated architectures. In addition, we propose a weak completeness property, discuss its merit and show a motivation for its use. Our main result shows that a triggering algorithm, used in one of our condition systems, strictly dominates another algorithm for conservative system, yet, both algorithms satisfy the same set of properties; thus, with some simple observations, we have a strong evidence for its optimality.

Distributed Denial-of-Service (DDoS) attacks seriously threat the servers in the Internet. Most of current research is focused on the detection and prevention methods at the victim side or the source side. However, defense at the innocent side, whose IP is used as the spoofed IP by the attacker, is always ignored. In this paper, a novel method at the innocent side has been proposed. Our detection scheme gives accurate detection results using little storage and computation resource. From the result of experiments, the approach presented in this paper yields accurate DDoS.

The capacity of wireless ad hoc networks has been widely studied since the pioneer works by Gupta and Kumar [3], and Grossglauser and Tse [4]. Various asymptotic results on capacity and capacity-delay tradeoffs have been obtained, whereas most of those investigated the asymptotic performance in large networks and addressed the delay caused by node mobility. In this paper the tradeoff between throughput capacity and average transmission delay of arbitrary scale wireless ad hoc networks is investigated. We consider a network with

N

nodes randomly distributed in a disk area of radius

R

. A new criterion of

transmission concurrency

is introduced to describe the concurrent transmitting capability of the network. And by using a constructive scheme, where a balanced scheduling strategy and a minimal length route selection mechanism are proposed, an analytical expression of the relationship between the throughput capacity

T

and the average transmission delay

D

is derived. A case study is also provided to give numerical results.

The stations that use a shared medium like IEEE 802.11 wireless LAN have transmission opportunities by contention in the contention period. If there are collisions in the contention period, a medium access control protocol may solve collisions by using a backoff algorithm. The backoff algorithm is an important part of the medium access control protocol, but a legacy backoff method used in IEEE 802.11 standard is not efficiently adjusted depending on the load condition and priorities. In this paper, we propose a new load-based dynamic backoff algorithm to improve throughput of medium and to reduce the number of collisions. The proposed backoff algorithm can increase network utilization about 20% than that of the binary exponential backoff algorithm.

This paper discusses an efficient implementation of the multiplexing protocol H.223, which is an important part of 3G-324M protocol stack required for 3G mobile multimedia communications. Our implementation of the protocol aims to support the multi-point video conferencing with the capability of transmitting/receiving multiple video/audio streams simultaneously. Conference managements such as admission and audio channel scheduling are also discussed. As a result, the implementation improves efficiency and makes the conference more convenient to set up and operate. Our prototype system is stable and its performance is satisfactory.

For IEEE 802.11 DCF, Backoff Timers of all stations in the wireless LAN are decreased by the same step if the state of channel is idle, and are paused and resumed at the same time. In this paper, we defined this as the “synchronization” feature of 802.11 DCF. The synchronization feature makes the packet collision probability of 802.11 DCF high. To break up the synchronization, this paper proposes a novel asynchronous backoff algorithm for 802.11 DCF, named

asyn

-DCF. A Markov model is built to analyze the performance of

asyn

-DCF. The simulation results indicate that

asyn

-DCF can decrease the packet collision probability significantly and utilize the channel more efficiently comparing to 802.11 DCF.

In the area of wireless mobile communication, minimizing energy consumption as well as maximizing data throughput in medium access control (MAC) layer is a very important research issue. The Distributed Coordination Function (DCF) of IEEE 802.11 provides the power saving mechanism (PSM) that allows nodes to remain silent in ‘doze mode’ for reducing energy consumption. However, IEEE 802.11 PSM is known to cause unnecessary energy consumption due to the problems of an overhearing, a back-off time delay and possible packet collisions. To overcome these problems, we present a new MAC protocol called ‘Slotted-PSM’ for IEEE 802.11 WLANs. In our proposed scheme, the Beyond-ATIM window is divided into a number of time slots, and any node that participates in communication wakes up in its slot times only and other nodes can enter to doze mode during the slot times. Slotted-PSM can reduce unnecessary energy consumption and idle listening problem in the Beyond-ATIM window.

A fundamental issue impacting the performance of mobile ad hoc networks is the wireless interference among neighboring nodes. In this paper, we derive an interference aware metric NAVC based on the information collected from the IEEE 802.11 Medium Access Control (MAC) layer. We then propose a novel Dynamic Interference Aware Routing protocol (DIAR) building on NAVC and AODV [3]. Both mathematical analysis and experimental study indicate that NAVC can effectively predict available bandwidth and delay. Simulation results indicate that the overall system performance can be improved by DIAR compared to AODV.

In this paper, a distributed power allocation scheme for wireless links in Rayleigh fast fading environments is proposed. An optimization model is formulated to minimize total transmit powers with constraint conditions that outage probability of each link should be satisfied. A closed-form near optimal solution to the model is presented based on the exploration of power ratio factor at the boundary of system capacity. In terms of the scheme, each link can determine its power ratio factor independently. The inequity problem of the power allocation algorithms in incremental fashion is avoided. Meanwhile the scheme is in low computational complexity due to closed-form solution and it is more time-saving than those schemes in iterative manner. By performance evaluation, we verify our analysis on the optimization model and validate a better result of our scheme in comparison with the counterpart. That is, a larger system capacity is admissible by our method.

We consider a typical wireless data access scenario: a number of mobile clients are interested in a set of data items kept at a common server. A client sends a request to inform the server of its desired data item while the server replies in the common broadcast channel. To study the energy consumption characteristics in such a scenario, we first define a power aware utility function. Based on the utility function, we propose a novel wireless data access scheme, which is a non-cooperative game—

wireless data access (WDA) game

. Although it does not rely on client caching (without-cache), our theoretical analysis shows that it is not always necessary for clients to send requests to the server. Simulation results confirm that our proposed scheme, compared with a simple always-request one, increases both the utility and lifetime of

every client

while reducing the number of requests sent, at the cost of slightly larger average query delay.

In this paper, a distributed power allocation scheme for wireless ad hoc networks in shadowing fading environments is proposed. Considering fluctuated SINR during the reception of long packets, especially in multimedia communications, outage probability is introduced as a QoS parameter. An optimization model is formulated to minimize total transmit powers with constraint conditions that outage probability requirement of each link is satisfied. We explore a near-optimal closed-form solution by exploration of power ratio factor at system capacity. The power allocation scheme is based on the solution. In the scheme, power ratio factor of each link can be determined independently. The inequity problem of the power allocation algorithms in incremental fashion is avoided. Meanwhile the scheme is more time-saving than those schemes in iterative manner. The scheme can be implemented on a time scale longer than that of shadowing fading. Thus network overload is alleviated. By numerical example, we verify a better performance of our power allocation scheme than its counterpart.

This paper proposes an on demand source routing protocol with multiple disjoint paths for ad hoc networks to support soft bandwidth constrained QoS requirement, which is termed as the Active Multipath QoS Routing (AMQR) protocol. A distributed route discovery algorithm is proposed to find multiple disjoint paths with associated path stability and network resource information. In addition, an actively dynamic route maintenance algorithm based on periodic state update combined with gratuitous QoS_ACK replies is introduced to refresh network topology and resource information, which helps the source dynamically adjust the traffic load on the desired route for data dispersion. Simulation results compared with DSR show that AMQR provides excellent end-to-end QoS.

Future mobile Ad hoc networks (MANETs) are expected to be based on all-IP architecture and be capable of carrying multitude real-time multimedia applications such as voice, video and data. It is very necessary for MANETs to have an optimal routing and quality of service (QoS) mechanism to support diverse applications. Providing multipath routing is beneficial to avoid traffic congestion and frequent breaks in communication due to mobility in MANETs. Differentiated Services (DiffServ) can be used to classify network traffic into different priority levels and apply priority scheduling and queuing management mechanisms to obtain QoS guarantees. Dynamically distributed traffic control can effectively take advantage of multiple routing paths to avoid congestion and decrease delay. In this paper, we propose an optimal QoS mechanism: Integrating Multipath routing, DiffServ and distributed Traffic control in mobile ad hoc networks (IMDT). Simulation results show that IMDT achieves better performance in terms of packet delivery ratio and average delay.

It is essential to design QoS supported MAC mechanism for supporting QoS in WLAN. In [1], we have proposed a new backkoff algorithm, named RWBO+BEB, to decrease the packet collision probability significantly. In this paper, we explore how to make RWBO+BEB support service differentiation in WLAN, and propose a novel proportional service differentiation algorithm, named

p

-RWBO, to allocate the wireless bandwidth according to the bandwidth ratio of each station. The basic idea of

p

-RWBO is that different priority stations use different walking probability,

p

w

, which is a key parameter in RWBO+BEB. An analytical model is proposed to analyze how to choose

p

w

according to the bandwidth ratios of stations. The simulation results indicate that

p

-RWBO can allocate the wireless bandwidth according to the bandwidth ratio of each station.

Ultra wide band (UWB) technology will be applied in the high rate wireless personal area networks (WPANs) for its high rate, low power, and innate immunity to multipath fading. In this paper, a power aware multi-hop packet relay MAC protocol in UWB based WPANs is proposed and a power aware path status factor (PAPSF), which is derived from SINR and power resource condition of each device, is used to select a suitable relay node. Compared with relaying by piconet coordinator (PNC), which is easily chosen by other ad hoc routing protocol, the new scheme can achieve higher throughput, decrease the time required for transmitting high power signal and we can easily distribute the battery power consumption from PNC to other devices in the piconet to prevent the PNC device using up its battery too fast and finally avoid PNC handover too frequently.

Design of medium access control (MAC) in wireless sensor networks (WSNs) poses several key factors such as energy conservation and latency. This paper proposes a new MAC protocol referred to as TEEMAC which reduces energy consumption by making the idle nodes sleep to reduce idle listening. TEEMAC is a cluster-based MAC protocol where each cluster is dynamically formed based on cluster-head. Numerical analysis is provided and it shows that the proposed MAC protocol outperforms other existing MAC protocols in terms of energy consumption.

This paper proposes TDMA-EC, a novel energy-conserving and collision-free media access control protocol based on TDMA principle. Through assigning separate time slots for neighboring nodes and resolving the “hidden terminal” problem, TDMA-EC performs well with collision avoidance and achieves better energy-efficient performance compared to contention-based protocols. Meanwhile, TDMA-EC schedules receiving and transmitting periods according to node’s position in the spanning tree of network, which also guarantees end-to-end latency with less jitter. Simulation results show that TDMA-EC achieves both energy conservation and lower latency compared to SMAC and DMAC.

Wireless Sensors Networks (WSNs) represent a new generation of embedded systems, which deploy wireless ad hoc communication mechanisms to route a sensory data from the originator sensor node to the base station. One of the most important issues in wireless sensor networks is to support real-time QoS, which is fundamentally a challenging problem. In this paper, we introduce EDBP scheduling algorithm for sensor network along with a MAC protocol based on the dynamic priority assignment EDBP. Two different platforms based experiment projects are designed to test our proposal.

In this paper we view the scheduling problem in Bluetooth as a bin packing problem (BPP) with

k

-preview items. We analytically demonstrate that even though the

First Fit Decreasing

with

k

-preview Items (

FFD-k

I) algorithm has the same asymptotic worst case performance ratio as the Look Ahead Round Robin (LARR) algorithm, it achieves a competitive asymptotic average case performance ratio which is superior to LARR and Round Robin (RR). We present both worst case and average case results. Extensive simulation results show that in a Bluetooth piconet, the

FFD-k

I algorithm achieves significantly better throughput and channel utilization performances over LARR and RR.

Multihop wireless networks in which each node is equipped with multiple wireless NICs can utilize multiple wireless channels to improve performance. But how to assign wireless channels to interfaces to avoid collisions extremely while the network keeps a good topology is a problem not well solved for such a multi-NIC multihop wireless network. We reexamine the general requirements of this problem and propose an algorithm to solve it effectively and efficiently. We regard it as a particular edge coloring problem, and introduce a step of topology simplification to degrade the complexity of the problem. Novel policies are proposed to select edges, group edges and color edges. Some results demonstrate the effectiveness of our algorithms and performance gains of network by channel assignment.

Wireless ad hoc networks face many challenges in routing, power management, and basic connectivity. The ability to predict the future communication connectivity between two or more autonomous wireless nodes is greatly beneficial to wireless ad hoc networks. Existing research has looked into using predicted node movement as a means to improve connectivity. While past research has focused on assuming wireless signals propagate in clear free loss space, our previous research has focused on using signal loss maps to improve predictions. This paper presents novel testing of predicting connectivity based on our previous concept designs. We test the performance of predicting future node connectivity by analysing various test cases and detailing results produced using custom simulator tools we have created.

Simulation is the most important and widely used method in the research of Mobile Ad hoc NETworks (MANET). The topology of MANET and the mobility of mobile nodes are the key factors that have impact on the performance of protocols. However, most of the existing works are based on random movement, and the fact that the network topology is highly related to the environment of MANET is overlooked. In this paper, we propose a novel Environment-Aware Mobility (EAM) model which models a more realistic movement of mobile nodes. Environment objects such as Route and Hotspot, etc are introduced to represent the environment components by Scalable Vector Graphics (SVG). This model is considered to be a complex model with a combination of existing conventional mobility models and network environments. The results show that the intrinsic characteristics and properties of the environments have a significant influence on the performance of MANET protocols.

Many routing protocols have been designed for Ad Hoc networks. However, most of these kinds of protocols are not able to react fast enough to maintain routing. In the paper, we propose a new protocol that repairs the broken route by using information provided by nodes overhearing the main route communication. When links go down, our protocol intelligently replaces these failed links or nodes with backup ones that are adjacent to the main route. Experimental results show that our protocol finds a backup route around 50% of cases and achieve better (or as good) in term of the packet delivery rate than the major Ad Hoc routing protocols, but with much less overhead.

Reactive routing protocols for ad hoc networks typically flood the network with request packets, but only discover one route from the network flood. Multipath routing protocols have been proposed to increase the efficiency of request flooding by discovering several routes from one request flood. A novel routing protocol, Path From Loop Recovery (PFLR), is proposed which recovers additional link-disjoint routes from topological loops. PFLR operates as a sub-layer beneath either a single or multipath reactive route discovery protocol. Simulation studies have revealed that the PFLR protocol is at its most efficient when recovering additional paths from small topological loops.

With the increased demand for high data rate wireless communication and the emergence of various wireless technologies, several integrated heterogeneous wireless systems, such as Multihop Cellular Network (MCN) and integrated Cellular and Ad hoc Relaying (iCAR) system, have been proposed recently. In this paper, we address the location management issue which is critical for the performance of heterogenous networks. We define a new performance metric called

Quality of Coverage (QoC)

. Using the iCAR system as an example, we compare various placement strategies in terms of their QoC values, and provide three rules of thumb as the guidelines for the placement of the ad hoc relay stations in iCAR. This QoC concept can be adopted in general, in deciding the optimum node locations (which need not be specialized ad hoc relay stations) for relaying traffic.

A surveillance application requires sufficient coverage of the protected region while minimizing the energy consumption and extending the lifetime of sensor networks. This can be achieved by putting redundant sensor nodes to sleep. In this paper, we propose a precise and energy-aware coverage control protocol, named Area-based Collaborative Sleeping (ACOS). The ACOS protocol, based on the net sensing area of a sensor, controls the mode of sensors to maximize the coverage, minimize the energy consumption, and to extend the lifetime of the sensor network. The simulation shows that our protocol has better coverage of the surveillance area while waking fewer sensors than other state-of-the-art sleeping protocols.

The coverage problem in wireless sensor networks (WSNs) is to determine the number of active sensor nodes needed to cover the sensing area. The purpose is to extend the lifetime of the WSN by turning off redundant nodes. In this paper, we propose a mathematical model for coverage analysis of WSNs. Based on the model, given the ratio of the sensing range of a sensor node to the range of the entire deployment area, the number of the active nodes needed to reach the expected coverage can be derived. Different from most existing works, our approach does not require the knowledge about the locations of sensor nodes, thus can save considerably the cost of hardware and the energy consumption on sensor nodes needed for deriving and maintaining location information. We have also carried out an experimental study by simulations. The analytical results are very close to the simulations results. The proposed method can be widely applied to designing protocols for handling sensor deployment, topology control and other issues in WSNs.

In conventional sensor networks, the sensors often are based on omni-sensing model. However, directional sensing range and sensors are great application chances, typically in video sensor networks. Thus, the directional sensor network also demands novel solutions, especially for deployment policy and sensor’s scheduling. Toward this end, this paper evaluates the requirements of deploying directional sensors for a given coverage probability. Moreover, the paper proposes how to solve the connectivity problem for randomly deployed sensors under the directional communication model. The paper proposes a method for checking and repairing the connectivity of directional sensor networks for two typical cases. We design efficient protocols to implement our idea. A set of experiments are also performed to prove the effectivity of our solution. The results of this paper can be also used to solve the coverage problem of traditional sensor networks as a special case.

Key pre-distribution techniques for security provision of Wireless Sensor Networks (WSNs) have attracted significant interests recently. In these schemes, a relatively small number of keys are randomly chosen from a large key pool and loaded on the sensors

prior to

deployment. After being deployed, each sensor tries to find a common key shared by itself and each of its neighbors to establish a link key to protect the wireless communication between themselves. One intrinsic disadvantage of such techniques is that some neighboring sensors do not share any common key. In order to establish a link key among such neighbors, a multi-hop secure path may be used to deliver the secret. Unfortunately, the possibility of sensors being compromised on the path may render such establishment process insecure.

In this work, we propose and analyze an Incremental Redundancy Transmission (IRT) scheme that uses the powerful Maximum Distance Separable (MDS) codes to address the problem. In the IRT scheme, the encoded secret link key is transmitted through multiple multi-hop paths. To reduce the total information that needs to be transmitted, the redundant symbols of the MDS codes are transmitted only if the destination fails to decode the secret. One salient feature of the IRT scheme is the flexibility of trading transmission for lower information disclosure. Theoretical and simulation results are presented to support our claim.

Sensor network technique consists that collecting information, transfer data by sensor nodes and that control sink node. But this sensor node has limited energy power and computing capability, so it has big problem that apply traditional security technique for sensor network. Especially, Research of security technology in real time wireless sensor network is not consisting yet. So we propose about efficient key management mechanism to allow existent secret sharing mechanism and one-way hash algorithm in real time wireless sensor network environment.

In dynamic peer networks, how to promote the performance of group key management without sacrificing the desired security is a critical and difficult problem. In this paper, a secure, efficient and distributed group key management scheme is presented and its security is proved. The scheme is based on hierarchical key tree and multi-party key agreement, and has the desired properties, suck as key independence and statelessness. The related analysis shows that the ternary key tree is most applicable to group key management, and the corresponding key management scheme is efficient in the computation cost, storage cost and feasibility.

Most of mobile ad hoc network (MANET) applications are based on the group communication and, because of the insecure characteristic of the wireless channel, multicast security is especially needed in MANET. Secure delivery of multicast data can be achieved with the use of a group key for data encryption. However, for the support of dynamic group membership, the group key has to be updated for each member join/leave and, consequently, a mechanism distributing an updated group key to members is required. The two major categories of the group key distribution mechanisms proposed for wired networks are the naive and the tree-based approaches. The naive approach is based on unicast, so it is not appropriate for large group communication environment. On the other hand, the tree-based approach is scalable in terms of the group size, but requires the reliable multicast mechanism for the group key distribution. In the sense that the reliable multicast mechanism requires a large amount of computing resources from mobile nodes, the tree-based approach is not that desirable for the small-sized MANET environment. However, recent studies on the secure multicast mechanism for MANET focus on the tree-based approach. Therefore, in this paper, we propose a new key distribution protocol, called the proxy-based key management protocol (PROMPT), which is based on the naive approach and reduces the message overhead of the naive by introducing the concept of the proxy node.

The problem for dynamic IP address assignment is manifest in mobile ad hoc networks (MANETs), especially in 4G all-IP-based heterogeneous networks. In this paper, we propose a ring-based address autoconfiguration protocol to configure node addresses. This work aims at the decentralized ring-based address autoconfiguration (DRAA) protocol, which has the capability to perform low latency and whose broadcast messages are reduced to lower control overhead. In addition, we introduce the centralized ring-based address autoconfiguration (CRAA) protocol to largely diminish control overhead and to serve as an even solution for IP address resource distribution. Both of DRAA and CRAA protocols are low-latency solutions because each node independently allocates partial IP addresses and does not need to perform the duplicate addresses detection (DAD) during the node-join operation. Communication overhead is significantly lessened in that RAA (DRAA and CRAA) protocols use the logical ring, thus utilizing fewer control messages solely by means of uni-cast messages to distribute address resources and to retrieve invalid addresses. Especially, the CRAA protocol reduces larger numbers of broadcast messages during network merging. The other important contribution is that our CRAA protocol also has an even capability so that address resources can be evenly distributed in each node in networks; this accounts for the reason our solution is suitable for large-scale networks. Finally, the performance analysis illustrates performance achievements of RAA protocols.

In this paper, we propose an end-to-end route optimization scheme for nested mobile networks, which we refer to as

Dual Binding Update

(

DBU

). In general, the nested mobile networks easily suffer from a bi-directional pinball routing with hierarchically multiple mobile routers. To handle this matter, we provide a new binding update (BU) message to allow a Correspondent Node (CN) to keep an additional Care of Address (CoA). And we also allow intermediate Mobile Routers (MRs) maintain a routing table to forward packets inside the mobile network and replace a source address of the packet for reverse route optimization. We evaluate the DBU with existing schemes by analytical approaches. The results show that the DBU reduces the delay of route optimization significantly under various scenarios and also improves an average Round Trip Time (RTT) consistently for many nesting levels tested.

In order to allow truly spontaneous and infrastructureless networking, the autoconfiguration algorithm of the mobile node addresses is important in the practical usage of most MANETs. The traditional methods such as DHCP can not be extended to MANETs because MANETs may operate in a stand-alone fashion and their topologies may change rapidly and unpredictably. The diversified schemes have been proposed to solve this problem. Some of them apply Duplicate Address Detection (DAD) algorithms to autoconfigure the address for each node in a MANET. However, the multi-hop broadcast used by DAD results in high communication overhead. Therefore, a new autoconfiguration algorithm is proposed in this article, which combines the enhanced binary split idea of Dynamic Address Allocation Protocol (DAAP) and the pseudo-random algorithm to construct the interface ID of IPv6 address. The allocation process is distributed and do not rely on the multi-hop broadcast, so our algorithm can be suitable for large scale MANETs through our simulation study.

The advances of wireless communication technologies, personal locator technology, and global positioning systems enable a wide range of location-aware services. To enable the services, a number of spatiotemporal access methods have been proposed for handling timestamp and time interval queries. However, the performance of the existing methods of a single index structure quickly degrades as time progresses. To overcome the problem, we propose to employ time-based partitioning on the R-tree called time boundary-based partitioning with flattened R-tree (BPR-Tree). The proposed scheme employs a new insertion policy to reduce the height of the tree and a time grouping method in order to minimize the search time of various queries. Extensive computer simulation reveals that the proposed scheme significantly outperforms the existing schemes.

The miniaturization of the computing machinery increases needs for using mobile computing of users. In this situation, Mobile IPv6 Working Group of Internet Engineering Task Force (IETF) suggests IPSec for Mobile IPv6 security. IPSec, however, has a long latency problem of dynamic security authentication due to the key management and a large amount of calculation. We therefore apply AAA in Mobile IPv6 to solve a dynamic security authentication problem of IPSec and simultaneously use Fast Handover technique for quick mobility. And we propose a method for reducing a long latency caused by authentication of mobile node (MN) during a handover. Old and new access routers authenticated by a hash value of an MN are able to reuse existing Security Authentication (SA) for a certain time and reduce latency for new SA. As a consequence, a mobile node can provide the real time services due to the reduction of authentication latency. Also, we can trust the buffered information through the tunnel between two access routers.

In Mobile IPv6, a handover latency is an important issue. To reduce the handover latency, mipshop working group in IETF has studied the fast handover (FMIPv6) which creates and verifies a new care-of address (NCoA) in advance before a layer 2 handover resulting in reduced handover latency. Even in FMIPv6, the NCoA must be registered in a home agent (HA). This registration still creates a significant amount of delay. To reduce registration latency, we propose a tentative and early binding update (TEBU) scheme that the NCoA is registered in the HA in advance during the layer 2 handover based on FMIPv6. We use cost analysis for the performance evaluation. As a result, we found that the TEBU scheme guarantees lower handover latency than FMIPv6 as much as 21%.

Mobile users expect similar kinds of applications to static ones, including various IP multicast applications. In mobile environment, the multicast tree should face with not only the dynamic group membership problem but also the mobile node’s position change issue. In this paper, we study the stability of IP multicast tree in mobile environment. We define a stability factor and investigate how the various elements of network and mobility impact on it. It is shown that the stability factor is mainly dominated by three elements, namely the ratio of the number of mobile nodes and network size, mobility model and the mobile multicast scheme. These results can give some useful references when we design a new mobile multicast scheme in the future.

In this paper, we propose the fast handover method in mSCTP using FMIPv6. Using FMIPv6 as handover procedure in mSCTP, the performance of handover can be significantly improved. First, mSCTP can add new network address to the correspondent node quickly as FMIPv6 provides New Care of Address (CoA) without closing connection to current network. Second, mSCTP can determine when it has to change the primary IP address with the trigger from FMIPv6. This trigger indicates that the mobile node has completely joined the network of New Access Router (NAR) and confirms that the MN can receive data through the NAR. We present integrated handover procedures that maximizes the handover performance between mSCTP and FMIPv6. We implement the integration of mSCTP and FMIPv6 in our test bed and verify the operation of suggested handover procedures by analysis of the experimental result.

In this paper an analytical model is proposed to investigate and quantify the effects and interactions of node mobility, network size and traffic load on the performance of ad hoc networks using AODV in terms of cost, average end-to-end delay and throughput. The analytical results reveal that contrary to the traditional concept, performance of ad hoc networks is much more sensitive to traffic load and network size than to node mobility. The capacity of ad hoc networks relies on the collective impact of all three factors but not any one alone. Furthermore, NS-2 based simulations are carried out to verify the theoretical model.

This paper investigates the maximum throughput and minimum delay of the new IEEE 802.15.4-standard. This standard was designed as a highly reliable and low-power protocol working at a low data rate and offers a beaconed and unbeaconed version. We will give the exact formulae for a transmission between one sender and one receiver for the unbeaconed version as this one has the least overhead. Further, the influence of the different address schemes, i.e. no addresses or the use of long and short addresses, is investigated. It is shown that the maximum throughput is not higher than 163 kbps when no addresses are used and that the maximum throughput drops when the other address schemes are used. Finally, we will measure the throughput experimentally in order to validate our theoretical analysis.

The hybrid wireless network is a kind of the novel network model, where a sparse network of base stations is placed within an ad hoc network. The problem on throughput capacity of hybrid wireless networks is considered to evaluate the performance of this network model. In this paper, we propose a general framework to analyze the capacity of hybrid wireless networks in code division multiple access scheme. Subsequently, we derive the mathematical analytical expressions of the capacity of hybrid wireless network systems under some assumptions. Finally, simulation results show that the hybrid wireless network could be a tradeoff between centrally controlled networks and ad hoc networks.

There is being an on-going effort in the research community to efficiently interconnect Mobile Ad hoc Networks (MANET) to fixed ones like the Internet. Several approaches have been proposed within the MANET working group of the Internet Engineering Task Force (IETF), but there is still no clear evidence about which alternative is best suited for each mobility scenario, and how does mobility affect their performance. In this paper, we answer these questions through a simulation-based performance evaluation across mobility models. Our results show the performance trade-offs of existing proposals and the strong influence that the mobility pattern has on their behavior.

The constrained resources of sensor networks challenge researchers to design resource efficient protocols. Clustering protocols are efficient to support the aggregation queries in sensor databases. This paper presents a novel clustering protocol, named UDC ( spatially Uneven Density Clustering ), to prolong the lifetime of sensor networks. Unlike other clustering protocols, UDC forms distributed sensor nodes into spatially uneven clusters according to local network conditions. In short, clustered by UDC, the nodes nearby the central base are grouped into smaller clusters, while the distant nodes are clustered into larger groups to save resources. Our simulation results exemplify that UDC can extend the lifetime of sensor networks up to twice as long as the other clustering protocols do.

Wireless sensor networks have emerged recently as an effective way of monitoring remote or inhospitable physical environments. One of the major challenges in devising such networks is how to organize a large amount of sensor nodes without the coordination of any centralized access point. Clustering can not only conserve limited system resource, but also serve as an effective self-organization tool. In this paper, we present a distributed clustering algorithm based on adaptive backoff strategy. By adaptively adjusting the wakeup rate of the exponential distribution, a node with higher residual energy is more likely to be elected clusterhead. We also take advantage of the contention-based channel access method to ensure that clusterheads are well scattered. Simulation experiments illustrate that our algorithm is able to significantly prolong network life compared with the conventional approach.

In this paper, we propose an efficient energy-saving cluster formation algorithm (ECFA) with sleep mode. ECFA can achieve energy efficient routing with the following two properties. First, ECFA reconfigures clusters with fair cluster formations, in which all nodes in a sensor network can consume their energies evenly. In order to achieve fair cluster regions, ECFA does not require any information on the location and energy of nodes. Second, by letting nodes very close to just elected cluster head be in sleep mode, ECFA can reduce unnecessary energy consumptions. Performances of ECFA are compared with LEACH and LEACH-C in the cases of the static and mobile nodes.

Clustering schemes have been proposed to prolong the lifetime of a Wireless Sensor Networks (WSNs). It is also desired that the energy consumption be evenly dispersed throughout the network. This paper presents RECA: a Ring-structured Energy-efficient Clustering Architecture. In RECA, nodes take turns to be the cluster-head and make local decisions on the fair-share length of their duty cycle according to their remaining energy and those of the rest of the nodes within the same cluster, consequently they deplete their energy supply at approximately the same time regardless of the initial amount of energy in their battery. RECA avoids the tight synchronization problem in LEACH and our primary results show that our scheme can achieve 50% – 150% longer network lifetime than LEACH depending on the initial energy level.

This paper presents a Distributed, Efficient Clustering Approach (DECA) for ad hoc and sensor networks. DECA can provide robustness against moderate node mobility and at the same time render energy-efficiency. The identified clusterheads cover the whole network and each node in the network can determine its cluster and only one cluster. The algorithm terminates in deterministic time without iterations, and each node transmits only one message during the algorithm. We prove analytically the correctness and complexity of the algorithm, and simulation results demonstrate that DECA is energy-efficient and resilient against node mobility.

Many schemes have been proposed to enhance throughput or fairness of the original IEEE 802.11 standard, however, they either fail to consider both throughput and fairness, or to do so with complicated algorithms. In this paper, we propose a new MAC scheme that dynamically optimizes each active node’s backoff process. The key idea is to enable each node to adjust its Contention Window (

CW

) to approach the optimal one that will maximize the throughput. Meanwhile, when the network enters into steady state in saturated case, i.e., under heavy traffic load, all the nodes will maintain approximately identical

CW

s, which guarantees fair share of the channel among all nodes. Through simulation comparison with previous schemes, we show that our scheme can greatly improve the throughput no matter the network is in saturated or non-saturated case, while maintaining good fairness.

Packet data service accessing state control is an effective wireless resource control scheme for 3G systems. This paper proposed an optimal control mechanism for packet data service accessing state by taking an integrated performance function of the mean packets waiting time

W

, the mean saving in the signaling overhead

S

and the mean channel utilization

U

as target function. By introducing a specific

IBP

model to better capture the characteristics of WWW traffic over cdma2000-1x systems, a system performance model was established. By analyzing the relationships between service model parameters and the state transition control timer, this paper presents a reference for project development to set some system parameters.

The lack of an established infrastructure and the hostile nature of the wireless channel make the design of ad hoc networks a challenging task. The cross-layer design methodology, which has been strongly advocated in recent years, essentially aims to overcome the sub-optimality introduced by designing each layer in isolation. This paper explores one aspect of such optimizations, namely using multiple antennas at each node for receiving and transmitting data using directional beams. By jointly analyzing both the MAC layer parameters and choosing a suitable routing protocol afterwards, improvements over earlier published schemes are obtained. We also perform in-depth simulations to characterize the better performance of various scenarios.

Media Access Control (MAC) is one the most critical issues for wireless ad hoc networks. In a hierarchical ad hoc network, all the nodes in the same cluster share the wireless channel. The current MAC algorithms can hardly adapt to both light and heavy traffic loads, thus cannot perform well with remarkably and frequently changing traffic load in ad hoc networks in which nodes keep moving in and out of clusters. A multi-token MAC (MTM) algorithm is proposed in this paper. It is used within single cluster in hierarchical ad hoc networks. It can automatically compromise between CSMA/CA in IEEE 802.11 and the token scheduling in cluster-head-gateway switching routing (CGSR) algorithm. Simulation results show that in the ad hoc network with active nodes moving in and out of clusters, MTM gives better throughput ratio and average packet delay.

Power consumption becomes a primary issue since wireless devices are often powered by batteries. This paper presents IEE-MAC, an improved energy efficient MAC protocol designed for IEEE 802.11-Based wireless Ad Hoc networks. In IEE-MAC, every node constructs a scheduling table in the distributed way by exchanging control information in ATIM window. Every node will only wake up to transmit or receive data frames and then enter doze state following the scheduling table to conserve energy consumption. Using this mechanism, IEE-MAC can eliminate the collision, overhearing, and idle listening. Moreover, IEE-MAC can adjust the size of ATIM window adaptively according to the actual traffic load in order to reduce unnecessary energy consumption without degrading the throughput of the network. Simulation results show that our protocol attains the better energy efficiency as well as throughput than other protocols in the literature.

Ad-hoc networks are an emerging technology with immense potential. Providing support for large-scale service and application deployment in these networks, however is crucial to make them a viable alternative. The lack of infrastructure, coupled with the time-varying characteristics of ad-hoc networks, brings about new challenges to the design and deployment of applications. This paper addresses these challenges and presents a unified, overlay-based service architecture to support large-scale service and application deployment in ad-hoc networks. We discuss the main functionalities of the architecture and describe the algorithms for object registration and discovery. Finally, the proposed architecture was evaluated using simulations and the results show that the architecture performs well under different network conditions.

Toward a new era of “Ubiquitous Networking” where people are interconnected in anywhere and at anytime via the wired and wireless Internet, we have witnessed an increasing level of impromptu interactions among human beings in recent years. One important aspect of these interactions is the

Peer-to-Peer (P2P) Networking

that is becoming a dominant traffic source in the wired Internet. In these Internet overlay networks, users are allowed to exchange information through instant messaging and file sharing. Unfortunately, most of the previous work proposed in the literature on P2P networking is designed for the traditional wired Internet, without much regard to important issues pertinent to wireless communications. In this paper, we attempt to provide some insight into P2P networking with respect to a wireless environment. We focus on P2P file sharing, already a hot application in the wired Internet, and will be equally important in the wireless counterpart. We propose a greedy server-peer selection algorithm to decide from which peer should a client download files so that the level of fairness of the whole network is increased and expected service life of the whole file sharing network is extended. We also propose a new performance metric called

Energy-Based Data Availability, EBDA,

which is an important performance metric for improving the effectiveness of a wireless P2P file sharing network.

With the advance in mobile wireless communication technology and the increasing number of mobile users, peer-to-peer computing, in both academic research and industrial development, has recently begun to extend its scope to address problems relevant to mobile devices and wireless networks. This paper is a performance study of peer-to-peer systems over mobile ad hoc networks. We show that cross-layer approach performs better than separating the overlay from the access networks with the comparison of different settings for the peer-to-peer overlay and underlying mobile ad hoc network.

It is publicly considered that the next generational Internet technology is grid computing, which supports the sharing and coordinated use of diverse resources in dynamic virtual organizations from geographically and organizationally distributed components. Grid computing characters strong computing ability and broad width information exchange[1]. Globus presented Open Grid Services Architecture (OGSA), which centered on grid services[3]. According to the characteristic of Grid-based Virtual Reality (GVR) and the development of current grid computing, this paper put forward the Orient-Grid Distributed Network Model for GVR, whose dynamic Virtual group is corresponding with the Virtual Organization in OGSA service. The GDNM is of more advantage to the distributed database consistency management, and is more convenient to the virtual group users acquiring the GVR data information, and the dynamic virtual groups in GDNM are easier and more directly to utilize the grid source and communication each other. The architecture of GVR designed in this paper is based on OGSA and web services, which is based on the OGSA. This architecture is more convenient to utilizing grid service and realizing the GVR. This paper put forward the method of virtual environment Object-oriented Dynamic Modeling (OODM) based on Problem Solving (PS), which is applied with dynamic digital terrain and dynamic object modeling. This paper presents the implementation of GVR and the interfaces of Grid Service.

Automobile manufacturers require sense data to analyse and improve the driving experience. Currently, sensors are physically wired to both data collectors and the car battery, thus the number of wires scale linearly with sensors. We design alternative power and communications subsystems to minimise these wires’ impact on the test environment.

In the microcell- or picocell-based system the frequent movements of the mobile bring about excessive traffics into the networks. A mobile location estimation mechanism can facilitate both efficient resource allocation and better QoS provisioning through handoff optimization. In this study, we propose a novel mobile tracking method based on Multi-Criteria Decision Making (MCDM), in which uncertain parameters such as PSS (Pilot Signal Strength), the distance between the mobile and the base station, the moving direction, and the previous location are used in the decision process using the aggregation function in fuzzy set theory. Through numerical results, we show that our proposed mobile tracking method provides a better performance than the conventional method using the received signal strength.

For the effective use and management of urban traffic control systems, it is necessary to collect and process traffic data and produce traffic information. Average travel speed is typically used for classifying traffic conditions of traffic signalized intersection networks. The purpose of this paper is to solve the pitfall caused by the usage of average travel speed estimated by conventional technique for the signalized intersection networks. To do this, this paper has suggested the basis of criteria for selecting the speed data to be used for final estimation of travel speed. The key point is to check the relevancy of travel time of the vehicles traveled during the same evaluation time period.

This paper proposes the static registration grouping scheme that solves the Home Location Register (HLR) bottleneck due to the terminal’s frequent registration area (RA) crossings and that distributes the registration traffic to each of the local signaling transfer point (LSTP) area. The RAs in LSTP area are grouped statically. It is to remove the signaling overhead and to mitigate the Regional STP (RSTP) bottleneck. The proposed scheme solves the HLR bottleneck due to the terminal’s frequent RA crossings to each of the LSTP area.

Mobile IPv6 (MIPv6) is one key protocol for IPv6 enabled computers and handsets providing always-on capabilities and seamless mobility between wireless and wired networks. Binding Update protocol, which has resolved the triangle routing problem in MIPv6, was fraught with vulnerabilities due to mobility. In this paper, we presented three typical lightweight unilateral authentication protocols for securing Binding Update, and compared their security features. We proposed one approach based on BAN logic, a famous formal method has been successfully used in several projects, with extended rules and definitions that are capable of specifying security properties and goals of these protocols. Finally, and the effectiveness of this approach was demonstrated. We hope these works can contribute to the ongoing design and deployment of MIPv6 and pave the way for future research in the security evaluation of MIPv6.

This paper deals with a prefetching method to enhance its prediction for context-aware services in mobile information system. This method aims to reduce the latency time to get the refreshed information appropriated to the current location of mobile users. To achieve this, our approach is to effectively limit the prefetched information into the most next location context. It makes use of the prefetching zone that reflects the user’s mobility speed and direction, and the mobile reference count that stands for the user’s visiting frequency to a given area. Then it considers the residence time, in order to further predict the prefetching candidates.

To effectively deal with video data, a semantic-based retrieval scheme that allows for processing diverse user queries and saving them on the database is required. This paper proposes a semantic-based multimedia database system that enables users to search the meaning of video data in a diverse manner. It uses both semantic and dependency weights to perform video retrieval for the environment education of infants. In the proposed system, the user searches multimedia data for environment education through entering keywords. The mobile agent then computes both semantic and dependency weights, ensuring the accuracy of data retrieved using calculated weights as annotative information of key frames. As a result of implementing and testing the prototype of the proposed system, a higher precision of approximately 96.5% was obtained.

Observational equivalence is a powerful means for formulating the security properties of cryptographic protocols. However suffering from the infinite quantifications over contexts, its proof becomes notoriously troublesome. This paper addresses the problem with a symbolic technique. We propose a symbolic bisimulation for spi calculus based on an environmental sensitive label transition system semantics, which restrict the infinite inputs of a process to only finite transitions. We also prove that the symbolic bisimulation is sound to the traditional concrete bisimulation, and furthermore is a promising means to automatically verifying the security protocols.

Induction of knowledge management system about healthcare enterprise is required. To address this issue of the lack of true knowledge management in healthcare enterprises, we propose a framework for common healthcare knowledge management. This framework is made up of two areas of applications and services, i.e. the mobile agent-based knowledge management application area and the strategic visualization, planning and coalition information service area.

It is very important for the information protection system to maintain high availability at each moment as a variety of intrusions occur continuously. The high availability of information protection system shall be primarily studied in relation to the infrastructure. The high availability on the infrastructure is assured by letting the fail over mechanism operate upon the entire structure through the structural design and the implementation of functions. The proposed method reduces the system overload rating due to trouble packets and improves the status of connection by SNMP Polling Trap and the ICMP transport factor by ping packet.

This paper proposes a fuzzy-based Prefetching method which obtains information to be referred in the near future with using the properties of mobile movement. We consider a velocity-based fuzzy model to find a pattern of movement for location-awareness service which provides the effective information about location change of mobile user or mobile computing on the context of Mobile Information Services. This procedure provides basic solutions which are optimal for a present situation with restricting the number of considered subject by defining prefetching area based on the movement length and direction.

High reliability and real-time response are required in the Main Control Processor of Radio Network Controller for mobile communication systems. In spite of its robustness some fault rates is inevitable, so the processors are duplicated for non-interrupted service and services are switched to the standby processor in case of faults. The hot-standby sharing scheme has advantages of no data loss and non-proliferation of error data in comparison with the warm-standby sharing scheme but it has difficulties with implementation due to synchronization problem. This paper proposes an expanded warm-standby sharing scheme based on a novel massage processing and error detection mechanism for improving performances.