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In April 1995, WINLAB (the Wireless Infonnation Network Lab­ oratory at Rutgers University) hosted the Fifth WINLAB Workshop on Third Generation Wireless Infonnation Networks. This workshop brings together a select group of experts interested in the future of Personal Communications, Mobile Computing and other services supported by wireless communications. As a sequel to Kluwer books on previous WINLAB workshops,l this volume assembles written versions of presentations of the Fifth Workshop. The last few years have been exciting for the field of wireless communications. The second generation systems that have absorbed our attention during those years are becoming commercial realities. Everyone is looking forward to PCS, especially in light of the recent auctions. We see an explosion of technical alternatives for meeting the demand for wireless communications. We also have applications in search of the best technologies rather than the reverse. The papers included provide new insights into many of the issues needing resolution for the successful introduction of the new services by the end of the decade. The authors represent views from both industry and universities from a number of nations. They are grouped into four main categories: Architecture, Radio Resource Management, Access, and Mobile Data, Mobile Networks.




1. Issues in Wireless Access Broadband Networks

In this paper, we discuss the effect of wireless link characteristics and mobility in wireless access broadband networks, and how major differences between wireline and wireless transmission links introduce a new networking paradigm with difficult and interesting challenges. We show that these differences have a direct impact on the packet-level quality-of-service defined by the packet loss, delay and jitter statistics. Moreover, we examine a number of alternatives such as forward error correction, antenna diversity and retransmission schemes to combat the time varying nature and high bit error rate of the wireless link, as well as how much and in what way these schemes can improve the packet-level quality-of-service. We also show that routing, call admission control, and capacity allocation functions of wireless access broadband networks need to take mobility into account. These functions can be invoked in a reactive manner at every hand-off event, or they can be invoked in a pro-active manner at the call setup time instead of being invoked at every hand-off event. In addition, we discuss the trade-offs between these two call control schemes, and show that each of these schemes is associated with a major cost. To find a balance between the cost of these two call control schemes, we use a connection tree as a basis for routing, call admission control, and resource allocation in wireless access broadband networks.
Mahmoud Naghshineh, Mischa Schwartz, Anthony S. Acampora

2. An ATM Based PCS/Cellular Architecture

Motivated by the market drivers and technology trends, we have created a vision of a new infrastructure for cellular/PCS services. This infrastructure will allow faster introduction of new services while maintaining low cost. The key elements of the proposed architecture are: the separation of the information transport functions from the processing and database functions; ATM connectivity between the Radio Port (air interface termination point) and the PSTN; flexible distribution of functional modules around an ATM based local or metropolitan area network; concepts of ‘user process’ and ‘home call manager’ to support sophisticated services and roaming users more effectively; new and faster hand-off mechanisms; new ATM Adaptation Layer (AAL); use of standardized OAM procedures in ATM network; ease in providing integrated services and common access to wireless and wired line services. The paper gives an overview of the proposed architecture and describes key aspects in some detail. Besides the authors, the architecture team includes: John Baldwin, Subra Dravida, Tom Laporta, Sanjiv Nanda, Phil Treventi, and Malathi Veeraraghavan.
Bharat T. Doshi, Anil Sawkar

3. A distributed, Mobile Wireless Infrastructure for multimedia Applications

A distributed, mobile network infrastructure for wireless multimedia applications is presented. This network is not constrained by a fixed backbone network as conventional cellular systems are. By using a clustering algorithm, nodes are organized into clusters. The access scheme relies on both time/code division inside a cluster and code separation across clusters. Clustering enhances the spatial reuse of time slots and codes. A TDMA structure provides bandwidth guarantee for real time traffic. Using different codes for different clusters by appropriate power control algorithms can increase the channel capacity. A fast reservation virtual circuit scheme allows us to extend the bandwidth guarantee also to mobile environments. Simulation experiments evaluate the performance of the proposed scheme.
Mario Gerla, Jack Tzu-Chieh Tsai, Nicholas Bambos, Shou C. Chen

4. Issues in Developing Functional Model(S) for Future Mobile Communication Networks

For several years, effort have been devoted in standardization fora to develop network architecture(s) for third generation mobile communication systems. Based on the three-stage methodology defined in ITU-T Recommendation 1.130 [1], mobile and Intelligent Network experts within ITU and ETSI are currently working on the functional modelling of respectively FPLMTS (Future Public Land Mobile Telecommunication Systems) and UMTS (Universal Mobile Telecommunication System). One of the major issues in deriving functional model(s) for future mobile communication systems concerns the harmonization of mobility features with the Intelligent Network (IN) principles. The support of mobility service features requires the analysis of how radio related control functions could impact on the development of future IN capability sets (CS-2 and CS-3). This paper addresses some of the issues related to the modelling of the radio access subnetwork and its interactions with IN functionalities.
Elisabeth Bui, Alain Charbonnier, Jean-Christian Benard-Dende

5. Mobility Support in a Wireless ATM Network

This paper presents an architecture for mobility support in a wireless ATM network scenario. We first introduce a TDMA based wireless ATM system where a datalink control protocol is used to convert the wireless channel into an ATM like multi-service transport. Afterwards, a mobility support architecture is proposed to facilitate terminal mobility in an ATM network environment. We separate the end-to-end VC into static segments and dynamic segments. In the process of mobile migration, the dynamic segment is reconfigured by the mobility support network switches and base stations. We also present a method for smooth handoff and cell resequencing by transferring the wireless datalink state information between base stations. For signaling support in a mobile ATM network, enhancements of current Q.2931 protocol are proposed.
R. Yuan, S. Biswas, D. Raychaudhuri

6. Adaptive Paging Algorithms for Cellular Systems

Adaptive algorithms which optimize the paging activity in a Cellular Mobile Telephone System are presented. They are analyzed within the context of North American Cellular Systems serving EIA/TIA 553 and IS 54 Rev B standard compliant mobiles. The basic approach is to page the cells in the system in two steps. First, page only those cells the mobile is most likely to be in (paging zone), and if no page response is received from them, then page the rest of the system also. A fixed interval registration scheme is used for tracking the location of the mobiles in the system. Every time a mobile registers, the cell it registered from is recorded in the VLR. When a mobile needs to be paged, the paging zone is selected based on the cell that it had last registered from (last known cell). In this paper, a novel method of computing the optimal paging zones is presented. The Mobile Switching Center (MSC) continuously collects page response data in the Location Accuracy Matrix (LAM). LAM keeps count of precisely how many page responses are received from each cell in the system. Using the LAM data, we compute the mean probability of locating the mobile in any cell of the system at the time of paging, given its last known cell. We present algorithms that use these probabilities to compute the optimal paging zones. Variations of the two step paging algorithm such as multiple step paging, repage of the paging zone, zone only paging and paging during overload are also presented. We prove that the algorithms presented are optimal and illustrate through examples the reduction in paging activity and the trade offs involved in each case. In a typical cellular environment, a 75–80% page reduction over system wide paging is obtained. The algorithms presented could be used to design a self engineering MSC that can automatically generate optimal paging zones.
Seshu Madhavapeddy, Kalyan Basu, Allison Roberts

Radio Resource Management

7. Distributed Measurement-Based Dynamic Channel Assignment for Wireless Personal Communications

The diverse environments for the emerging wireless personal communications could render the centralized prediction-based channel assignment methodology, conventionally employed in cellular radio networks, impractical. The distributed measurement-based approach seems to be a practical solution. In this paper, we study and compare several different distributed measurement-based algorithms for dynamic channel assignment (DCA). Their performance is also compared with that of a centralized prediction-based algorithm. It is found that a simple aggressive algorithm without using a threshold (LIA—Least Interference Algorithm) performs the best.
Matthew M.-L. Cheng, Justin C.-I. Chuang

8. Distributed Radio Resource Allocation in Highway Microcellular Systems

In this paper Distributed Radio Resource Allocation (DRRA) is investigated for highway microcellular systems. An algorithm, which combines the assignments of base station, channel and transmitter power, is proposed. The resource allocations are based on filtered measurements which are compared to fixed system thresholds. The performance of the proposed Threshold and Timer Algorithm (TTA) is evaluated in a model which includes user mobility as well as time-varying propagation conditions. The simulation results for the TTA scheme show that almost all channels can be used simultaneously in every cell, while still providing the sufficient communication quality. It is also demonstrated that the TTA algorithm outperforms a reference system using a Fixed Channel Assignment (FCA) strategy with a factor of 3.
Michael Andersin, Magnus Frodigh, Kai-Erik Sunell

9. Handover Performance: Propagation and Traffic Issues

Efficient handoff is very important for cellular mobile communication systems because the number of handoffs increases with the smaller cell sizes needed for high capacity systems. Propagation, traffic, switching and processing are all important issues in assessing handoff performance, and most of the past performance studies have focussed on only one of these issues.
In this paper, we discuss various issues related to handoff performance and the interdependency of these issues by carrying out investigations on a combined platform. In particular, we consider handover strategies, signal strength prediction schemes, handover priority schemes and handoff priority level assignment schemes. It is shown that individually optimised solutions will not provide the optimum solution in the combined system, and the need for investigations in an integrated environment is emphasised.
Gamini Senarath, David Everitt

10. A Simple Analysis of CDMA Soft Handoff Gain and its Effect on the Cell’s Coverage Area

This paper presents an analysis of soft handoff and its effect on the coverage area of a CDMA system. The analysis is based on the determination of outage probabilities around the system’s coverage area, incorporating in part the effects of CDMA reverse link power control and soft handoff gains. We obtain the probability of service at the edge of the cell and hence the area reliability of the CDMA system. We also examine the dependence of the service probability and the area reliability on the soft handoff area and the required fade margin. A CDMA network planning tool based on the soft handoff analyses has been used to calculate the average outage probability (area reliability) on a site-by-site basis. It is observed that the outage probability is underestimated if the analysis is entirely conditioned on soft handoff. It is shown that the soft handoff gain is dependent on the percentage of median area in handoff and on the probability of handoff. The soft handoff gain over hard handoff is around 4 dB for about 40% – 50% median area in soft handoff.
Pulin R. Patel, Usman S. Goni, Eric Miller, Paul P. S. Carter

11. An Algorithm for Capacity Allocation in Cellular Spread Spectrum Networks with Nonuniform Traffic Loadings

We propose an algorithm that enables each user in a mobile spread spectrum radio network to select a cell site and a transmitter power level for the uplink communication. From the point of view of a user, the algorithm allocates enough bandwidth to satisfy the user’s bit rate requirement. From the point of view of the network, the algorithm allocates capacity to spatial regions. If a region becomes congested then the network automatically adjusts cell boundaries to accommodate this extra traffic. We compare the capacity under this algorithm with that in which users always select the strongest cell site. In the case of a single traffic hotspot, the capacity of the congested region is shown to be almost three times greater under the proposed algorithm.
Stephen Hanly

12. Uplink Power Control for CDMA Cellular Systems

In cellular wireless communication systems, transmitted power is regulated to provide each user an acceptable connection by limiting the interference caused by other users. Several models have been considered including: (1) fixed base station assignment where the assignment of users to base stations is fixed, (2) minimum power assignment where a user is iteratively assigned to the base station at which its signal to interference ratio is highest, and (3) diversity reception where a users signal is combined from several or perhaps all base stations.
This work unifies results found for these systems by identifying common properties of the interference constraints that permit a general proof of the convergence of iterative power control methods. In particular, the uplink power control problem can be reduced to finding a vector p of users’ transmitter powers satisfying p I(p) where the jth constraint p j I j (p) describes the interference that user j must overcome to achieve an acceptable connection.
For a class of functions I(p), called standard interference functions, it is shown that if p I(p) has a feasible solution, then the iteration p ( t + 1) = I(p(t)) converges to a unique fixed point p * such that p * p for any feasible power vector p. Totally asynchronous convergence of the iteration p(t +1) = I(p( t )) is also demonstrated. In addition, it is verified that a number of extensions, including minimum and maximum transmitter power constraints, can be described by standard interference functions.
Roy D. Yates

13. A Distributed Power Control Algorithm for Bursty Transmissions on Cellular, Spread Spectrum Wireless Networks

We propose a distributed algorithm for power control in cellular, wideband networks for bursty traffic sources, such as data and speech with silence detection. The algorithm adapts power at mobiles on the basis of only local measurements of the mean and variance of the interference. The first part of the paper introduces a probabilistic quality of service specification and gives an asymptotic framework for estimating orders of magnitudes of the quantities which affect it. The second part gives the algorithm and the condition for its convergence at a geometric rate. The condition is not burdensome.
Debasis Mitra, John A. Morrison

14. Soft Admission in Cellular PCS with Constrained Power

In this paper we study the mobile admission control problem in a cellular PCS network where transmitter powers are constrained and controlled by a Distributed Constrained Power Control (DCPC) algorithm. Receivers are subject to non-negligible noise (due to restricted power levels), and the DCPC attempts to bring each receiver’s CIR above a given target. A newly arrived mobile requires a new communication link, i.e., a cell (base station) and a channel. To guarantee a certain degree of link quality, as well as low outage and blocking probabilities, admission control must be carefully exercised. The outage and the blocking probabilities are closely related to the two following types of admission errors: Type I error, where a new mobile is erroneously accepted and results an outage; Type II error, where a new mobile is erroneously rejected, while it could be supported along with the other active mobiles. This results in blocking. In this paper we consider two classes of distributed mobile admission controls. One is a Non-Interactive Admission Control (N-IAC), where admission decisions are instantaneously made based on the system state. The algorithms in this class are subject to errors of type I and II. The other is an Interactive Admission Control (IAC), under which the new mobile is permitted to interact with one or more potential channels before a decision is made. In this class, we derive a Soft and Safe (SAS) admission algorithm, which accepts a new mobile if and only if the active mobiles and the new one, can be supported at their target CIRs. That is, an algorithm which is type I and II error free. Moreover, during the interactive process, the CIRs of all active links are kept above their target CIRs, at any moment of time. Also, a Fast SAS algorithm which is only type I error free, is evaluated and proposed for practical implementation.
M. Andersin, Z. Rosberg, J. Zander


15. Performance Analysis of Capture-Division Packetized Access (CDPA) for Cellular Systems

Recently, a new method for achieving spectrum reuse in cellular systems, called Capture-Division Packetized Access (CDPA), has been introduced. The method is based on packet switching and uses a single frequency in all cells, allowing each transmitter to access the full bandwidth. Practically, the CDPA’s way of operation can be seen as an S-ALOHA scheme among different cells in which the Mobile Stations belonging to the same cell transmit using a collision-free mechanism, which is easily obtained due to the very short intra-cell propagation delay. Parallel transmission in different cells is achieved through the “capture” capability. Packets that are not captured are almost immediately retransmitted, thus assuring that packets are eventually correctly received. In this paper we analyze the capacity of the system in which two frequencies are used for the communications to and from the base stations. Analytical evaluations show that, although uplink and downlink channels behave differently, CDPA may provide larger capacity than classic systems based on “a priori” bandwidth subdivision, as the FDMA with a seven cell frequency reuse pattern or CDMA.
Flaminio Borgonovo, Luigi Fratta, Michele Zorzi

16. A Novel Radio Channel Control Method for Improved Multiple Access Schemes

This paper considers a recursive method for individual users to decide retransmission probability to improve channel utilisation for a grouped slotted Aloha system in Delayed First Transmission model, in which all the users are divided into two groups according to the signal power. Assume that the total channel traffic can be formulated as a Poisson stream with the mean Ki (i = 1,2) and each user has a counter to update the backlog in each group according to a quadruple feedback transmitted during the current slot from the base station. This information is immediately available to each user in both groups. The optimal channel utilisation which maximises the total channel throughput can be obtained if the individual user re-transmits a packet with the probability \( {p_{{k,i}}} = \frac{{{K_i}}}{{{S_{{k,i}}}}} \). The simulation shows that the total throughput of 0.521 is obtained with 0.328 for a higher power group and 0.193 for the lower power group.
Q. Cao, M. K. Gurcan

17. Successive Interference Cancellation Schemes in Multi-Rate DS/CDMA Systems

In this paper we propose successive interference cancellers (IC) for a variable data rate environment. Firstly, a successive interference cancellation (IC) scheme for M-level rectangular QAM in DS/CDMA systems is analysed. Secondly, the performance under Rayleigh fading is analysed for single modulation systems and different systems for handling multiple data rates. One alternative for handling multi-rate systems is to use mixed modulation, which imply that each user chooses modulation format according to need. Another alternative is to use parallel channels, where each user transmits over one or several synchronous channels. We show that the successive IC, for mixed modulation or parallel channel systems, has a performance close to the single BPSK user bound and, consequently, it gives a considerable increase in performance and flexibility compared to both single modulation systems and mixed modulation or parallel channel systems employing a conventional detector.
Ann-Louise Johansson, Arne Svensson

18. A New Distributed Reservation Multiple Access Scheme for the AVPAC Channel

Aeronautical Radio, Inc. has proposed DRM A (Distributed Reservation Multiple Access) for the integration of voice and data on the AVPAC (Aviation VHF Packet Communication) channel, also known internationally as VDL (VHF Data Link). DRM A offers various interesting features; yet it has some limitations. In this report, we evaluate DRM A and extend it to make it more efficient and more suitable to the AVPAC mobile environment. First, we review the PRMA(Packet Reservation Multiple Access) protocol which is related to DRMA in several ways. Then, an improved algorithm that can increase the throughput of DRMA is proposed. We also propose a handoff mechanism for this protocol. Handoffs were not considered previously in Aeronautical Radio, Inc.’s DRMA documents, which were designed only to test the correctness of the mechanism.
Sanjay Singh, Mario Gerla, Steve Friedman

19. Network Simulations for IS-95 CDMA Systems

A simulation methodology on the network planning aspects of TIA/EIA IS-95 CDMA system is presented. The forward and reverse link network performance under various cell site layouts, traffic loads and system parameter settings can be assessed using this simulation model. Effects due to reverse power control, forward power allocation, soft and softer handoff, mobile traffic distribution, and target Eb/Nt are incorporated. The effect of correlated lognormal shadowing can be applied to the radio coverage plots. From the simulation results, it is shown that soft handoff provides significant diversity gains on both forward and reverse links under lognormal shadowing. The reverse capacity loading and forward power allocation statistics of a given base station can be accurately estimated. The forward link radio coverage can be assessed from the available pilot Ec/Io plot, the soft/softer handoff state plot, and the required forward traffic power allocation plot. The reverse link radio coverage can be assessed from the required mobile transmit power plot. All these plots can be generated with and without Monte Carlo shadowing runs. If shadowing is included a specified reliability target can be set for the plots. It is found that the radio coverage is normally reverse link limited due to the lower maximum mobile transmit power. However, poor pilot Ec/Io coverage may exist in the forward link when many base stations have competing signal strengths. The forward traffic channel coverage is generally acceptable in the soft handoff region due to diversity, but may exhibit large fluctuations in regions right before soft handoff, especially for high speed mobiles. The ability to perform fast handoff state update and fast traffic power allocation is important in mitigating these fluctuations. The optimal handoff threshold should be set considering all the following factors. The threshold should be set lower in maintaining the same coverage for a higher load. As long as the coverage objective is achieved for the anticipated load, the threshold should be set higher to reduce the soft handoff probability which incurs equipment overheads. The threshold should also be set low enough to mitigate unstable forward traffic coverage right before handoff as well as providing enough reverse link soft handoff gains so that reverse capacity and coverage can be improved.
Szu-Wei Wang, Hua Mary Chion

Mobile Data, Mobile Networks

20. Cellular Wideband Mobile Data Communications

Mobile data belongs to one of the newly emerged, ever fast growing, and most imaginative wireless communication markets today, created by the synthesis between communication industry, computers, software, and information technology. It has the potential to offer the wide range of new services and applications to the world that may have profound influence over people’s changing life and work styles in the years to come. Among these, many new data services have the traffic characteristics of “bursty”, requiring uni- and/or bi-directional asymmetric data transfer. Many applications, like mobile video, remote computer access, and file loading, will definitely require high transmission rate.
Zhichun Honkasalo, Jari Hämäläinen

21. Experimental Results From Internetworking Data Applications Over Various Wireless Networks Using a Single Flexible Error Control Protocol

This paper describes results from several wireless field trials. During these trials, data applications communicated over various combinations of wireless networks including satellite, low power PCS, high power cellular, and packet data. Looking at loss of packets and higher layer blocks, our initial results indicate that channel conditions vary dramatically, even within a single network. We highlight the effect of these conditions on error control protocols. In particular we show that an efficient general wireless error control protocol needs powerful error control mechanisms and sophisticated dynamic control algorithms.
A. J. McAuley, D. S. Pinck, T. Kanai, M. Kramer, G. Ramirez, H. Tohme, L. Tong

22. Radio Link Protocols for Cellular Data

Wide-area data services over cellular networks have been standardized in the last two years. The standards were developed under the following primary constraints:
  • compatibility with existing land-line standards and systems,
  • cellular physical layer standards optimized for voice,
  • market demands for quick solutions.
In this paper we focus on radio link layer design and discuss how these constraints helped determine the protocols that have been standardized. We summarize the design, architecture and requirements for cellular circuit-mode and packet-mode data. We describe several design tradeoffs including a comparison of one level versus two level recovery mechanisms and provide performance comparisons. We also discuss the performance impact of several design choices.
Bharat T. Doshi, Richard P. Ejzak, Sanjiv Nanda

23. An Asymmetric Cost Model for Query Processing in Mobile Computing Environments

We address the issue of query processing for information services in mobile environments, using a mobile sales and inventory application example. Efficient query processing depends upon choosing one of several candidate query plans based upon a cost model which accurately reflects computation and communication costs. Unlike traditional distributed database environments, mobile environments necessitate new cost models which are asymmetric in the sense that the resources available at mobile sites are less than those at fixed sites, and communication costs vary with the direction of data transfer. In addition, communication costs may vary as the mobile moves. We design a cost model which incorporates these criteria and illustrate it via examples. As costs change dynamically, it is desirable that the query execution plan be modified dynamically to optimize the cost. Existing distributed query processing algorithms can be modified to suit the mobile environment and this paper discusses our ongoing work to do so.
Ravi Jain, Narayanan Krishnakumar

24. An Efficient Approach to Updating Replicated Databases in Wireless and Advanced Intelligent Networks

In the Personal Communication Network (PCN), and the Universal Personal Telecommunication (UPT) services and possibly other services to be offered by the Advanced Intelligent Networks (AIN), customer records for call routing and other signaling functions can be distributed and replicated at multiple sites to improve access delay and system availability. The basic question addressed in this paper is: What is the appropriate concurrency and commitment protocol for the replicated databases in the PCN and the UPT services so that updated routing and signaling data can be made available for call processing as quickly as possible? We observe that these applications can tolerate inconsistency between replicated records at various sites, because the main consequence of accessing obsolete data is call misroute. By exploiting this observation, we propose the Primary-Writer Protocol (PWP) as the concurrency control and commitment protocol for updating the replicated databases.
We analyze the fraction of calls misrouted under the PWP, and compare the PWP with two protocols: the Primary-Site Locking (PSL) and the Basic Time-Stamp (BTS) protocols. Since the PWP avoids extensive message exchanges among sites, it reduces the possibility of misroute in comparison with the PSL and BTS protocols. Our results reveal that the fraction of calls misrouted under the PWP is very small for the expected customer behavior in the PCN (wireless networks), and the UPT and other services offered by the AIN. The only operating region in which misroutes may be unacceptably high is for customers requiring a huge throughput and with high query-to-update ratios. However, this situation does not occur in practice.
Kin K. Leung


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