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With the rapid growth of the Internet as well as the increasing demand for broadband services, access networks have been receiving growing investments in recent years. This has led to a massive network deployment with the goal of eliminating the ba- width bottleneck between end-users and the network core. Today many diverse te- nologies are being used to provide broadband access to end users. The architecture and performance of the access segment (local loop, wired and wireless access n- works, and even home networks) are getting increasing attention for ensuring quality of service of diverse broadband applications. Moreover, most access lines will no longer terminate on a single device, thus leading to the necessity of having a home network designed for applications that transcend simple Internet access sharing among multiple personal computers and enable multimedia support. Therefore, the access network and its home portion have become a hot investment pool from both a fin- cial as well as a research perspective. The aim of the annual International Conference on Access Networks (AccessNets) is to provide a forum that brings together scientists and researchers from academia as well as managers and engineers from the industry and government organizations to meet and exchange ideas and recent work on all aspects of access networks and how they integrate with their in-home counterparts. After Athens in 2006, Ottawa in 2007, and Las Vegas in 2008, this year AccessNets moved to Asia for the first time.




Session 1: PON

Hybrid Dynamic Bandwidth and Wavelength Allocation Algorithm to Support Multi-Service Level Profiles in a WDM-EPON

A novel bandwidth assignment algorithm in WDM Ethernet Passive Optical Networks, called DyWaS-SLA, is proposed not only to provide service differentiation but also to offer subscriber differentiation. Simulation results show that DyWaS-SLA outperforms other bandwidth allocation algorithms in WDM-EPONs as it makes fairer bandwidth distribution than those methods. Consequently, it always insures a guaranteed bandwidth for every priority subscriber. Furthermore, DyWaS-SLA obtains lower mean packet delay and packet loss rate for the highest priority subscribers when compared with other bandwidth distribution schemes in WDM-EPONs.
Noemí Merayo, Rubén González, Ignacio de Miguel, Tamara Jiménez, Ramón J. Durán, Patricia Fernández, Rubén M. Lorenzo, Juan C. Aguado, Evaristo J. Abril

Utility Max-Min Fair Resource Allocation for Diversified Applications in EPON

In EPONs, differentiated services enable higher quality of service (QoS) for some queues over others. However, owing to the coarse granularity of DiffServ, DiffServ in EPONs can hardly facilitate any particular QoS profile. This paper investigates an application-oriented bandwidth allocation scheme to ensure fairness among queues with diversified QoS requirements. We first define application utilities to quantify users’ quality of experience (QoE) as a function of network layer QoS metrics. We then formulate the fair resource allocation issue into a max-min utility problem, which is quasi-concave over queues’ delayed traffic and dropped traffic. We further employ the bisection method to obtain the optimal solution of the quasi-concave maximization problem. The optimal value can be achieved by proper bandwidth allocation and queue management schemes in EPONs.
Jingjing Zhang, Nirwan Ansari

Session 2: WIFI and WiMAX

Fairness Enhancement for 802.11 MAC

Location dependency and its associated exposed receiver problem create the most severe unfairness scenario of the CSMA/CA protocol. An analytical model is built up to study the success probabilities of RTS reception and RTS/CTS handshake of the typical disadvantaged link under the exposed receiver scenario. Derived from the analytical insights, we propose a receiver assistance feature (RcvAssist) for the CSMA/CA protocol which not only significantly enhances the fairness of disadvantaged links suffering from exposed receiver problem, but also increases the overall throughput without introducing other side effects, such as aggregating the hidden terminal problem.
Caishi Huang, Chin-Tau Lea, Albert Kai-Sun Wong

SWIM: A Scheduler for Unsolicited Grant Service (UGS) in IEEE 802.16e Mobile WiMAX Networks

Most of the IEEE 802.16e Mobile WiMAX scheduling proposals for real-time traffic using Unsolicited Grant Service (UGS) focus on the throughput and guaranteed latency. The delay jitter and the effect of burst overhead have not yet been investigated. This paper introduces a new technique called Swapping Min- Max (SWIM) for UGS scheduling that not only meets the delay constraint with optimal throughput, but also minimizes the delay jitter and burst overhead.
Chakchai So-In, Raj Jain, Abdel-Karim Al Tamimi

Influence of Technical Improvements on the Business Case for a Mobile WiMAX Network

From a technical point of view, Mobile WiMAX may offer an appropriate solution for delivering broadband wireless access. Two remaining questions, however, are whether the rollout of a WiMAX network is economically feasible or not, and how technical improvements like MIMO, beamforming and turbo-coding can influence the business case. In this paper different technical scenarios for a Mobile WiMAX rollout are defined and evaluated from an economic as well as a technical perspective. To obtain realistic figures, we have defined a business case for a Mobile WiMAX rollout in Belgium, a country with a high wired broadband penetration. Further, we give an indication about the feasibility of a Mobile WiMAX network related to the population density. Finally, as the introduction of a new technology involves a lot of uncertainties, a detailed sensitivity analysis on both the economic and technical input parameters is performed to determine the most influencing parameters.
Bart Lannoo, Jeffrey De Bruyne, Wout Joseph, Jan Van Ooteghem, Emmeric Tanghe, Didier Colle, Luc Martens, Mario Pickavet, Piet Demeester

Session 3: 4G Wireless Networks

Optimizing Energy and Modulation Selection in Multi-Resolution Modulation For Wireless Video Broadcast/Multicast

Emerging technologies in Broadband Wireless Access (BWA) networks and video coding have enabled high-quality wireless video broadcast/multicast services in metropolitan areas. Joint source-channel coded wireless transmission, especially using hierarchical/superposition coded modulation at the channel, is recognized as an effective and scalable approach to increase the system scalability while tackling the multi-user channel diversity problem. The power allocation and modulation selection problem, however, is subject to a high computational complexity due to the nonlinear formulation and huge solution space. This paper introduces a dynamic programming framework with conditioned parsing, which significantly reduces the search space. The optimized result is further verified with experiments using real video content. The proposed approach effectively serves as a generalized and practical optimization framework that can gauge and optimize a scalable wireless video broadcast/multicast based on multi-resolution modulation in any BWA network.
James She, Pin-Han Ho, Basem Shihada

System Evaluation of PMI Feedback Schemes for MU-MIMO Pairing

A Best Companion Cluster (BCC) user terminal (UE) feedback scheme for Multi-User Multi-Input-Multi-Output (MU-MIMO) pairing is proposed in this paper. With this scheme, one UE should feedback both a preferred Precoding Matrix Index (PMI) and a cluster index with least interference to it. The system level simulation results show that this scheme can make a reasonable tradeoff between feedback overhead and throughput, especially when the system load is not so heavy.
Yinggang Du, Jianfei Tong, Jing Zhang, Sheng Liu

Session 4: FIWI

On Mitigating Packet Reordering in FiWi Networks

In an integrated fiber and wireless (FiWi) access network, multi-path routing may be applied in the wireless subnetwork to improve throughput. Due to different delays along multiple paths, packets may arrive out of order, which may cause TCP performance degradation. Although the effect of packet reordering due to multi-path routing has been well studied, remedy solutions are either to schedule packets at the source node to proactively reduce the chance of packet reordering, or to modify TCP protocol. Resequencing packets arrived out-of-order has only been considered at the end systems which can cause long delay as packets must be buffered until there is no sequence gap. As all traffic in a FiWi network is sent to the Optical Line Terminal (OLT), the OLT serves as a convergence node which naturally makes it possible to resequence packets at the OLT before they are sent to the Internet. However, the challenge is that OLT must re-sequence packets effectively with a very small delay to avoid a performance hit. In this paper, we propose a scheduling algorithm at the OLT to resequence packets while providing fairness. Simulation results validate that our packet scheduling algorithm is effective in improving the performance of TCP flows. Since resequencing is conducted in the access network which has a much fewer number of flows compared with those at routers, our proposed work provides a scalable solution to mitigate the side-effect of packet reordering caused by multi-path routing.
Shiliang Li, Jianping Wang, Chunming Qiao, Bei Hua

Adaptive BU Association and Resource Allocation in Integrated PON-WiMAX Networks

This paper addresses the issue of base station user association and resources allocation (BUA-RA) in OFDM-TDMA-based broadband wireless access (BWA) networks under PON-WiMAX integration. With the powerful coordination capability at the optical line terminal (OLT), a key technology of inter-cell collaborative transmission (CT) is incorporated in the integrated network architecture, which is so called cooperative PON-WiMAX network (CPWN). To achieve an efficient integration and inter-cell CT in the CPWNs, BUA-RA is critical to the Quality of Service (QoS) provisioning for each user. In order to minimize the network resource usage, we provide three new BUARA schemes, which can be adaptively applied according to the network loads and wireless users’ moving speeds. Simulations are conducted to verify the proposed BUA-RA schemes by comparing with those without CT technology and to demonstrate the efficiency of the proposed mathematical formulations and linearization approach.
Ming Gong, Bin Lin, Pin-Han Ho, Patrick Hung

Session 5: Broadband Access Networks

A Future Access Network Architecture for Providing Personalized Context-Aware Services with Sensors

We propose a future access network architecture that can provide advanced context-aware services by securely delivering diverse kinds of dynamically changing sensor information about specific localities or private individuals. The architecture features individual and group management of peer-to-peer-based secure connections established between terminals and servers. It implements multiaccess functions that enable terminals to deliver sensor information to multiple different application servers and multi-service functions that enable the terminals to receive information-provision services from those servers.
Masugi Inoue, Masaaki Ohnishi, Hiroaki Morino, Tohru Sanefuji

Session 6: Cognitive Radios

How to Optimally Schedule Cooperative Spectrum Sensing in Cognitive Radio Networks

In cognitive radio (CR) networks, secondary users can be coordinated to perform spectrum sensing so as to detect primary user activities more accurately. However, in a dynamic spectrum environment, more sensing cooperations may induce every secondary user to sense more channels, thus decreasing their transmission time. In this paper, we study this tradeoff by using the theory of partially observable Markov decision process (POMDP). This formulation leads to an optimal sensing scheduling policy that determines which secondary users sense which channels with what miss detection probability and false alarm probability. A myopic policy with lower complexity yet comparable performance is also proposed. Numerical and simulation results are provided to illustrate that our design can utilize the spectrum more efficiently for cognitive radio users.
Ke Lang, Yuan Wu, Danny H. K. Tsang

Efficient Spectrum Sharing in Cognitive Radio Networks with Implicit Power Control

Cognitive radio technology solves the spectrum under- utilization problem by enabling the secondary users access the spectrum holes opportunistically. How to efficiently share the spectrum holes among the secondary users, therefore, is of interest. Previous studies on spectrum sharing either do not consider interference constraints or assume the links being unidirectional. For simplicity the power control is usually not jointly considered when modeling the spectrum sharing in most of the previous studies. In this paper, we present a cross-layer design by modeling the spectrum sharing and power control with the interference constraints. A binary integer linear programming (BILP) problem is formulated to determine which link will be established, which channel will be assigned to each established link and which power level each established link will use for transmission. Different from the previous work, we assume links being bidirectional because we believe the link level acknowledgements in an ad-hoc network are a must. Moreover, we propose an implicit power control approach, where the power level for each link is predefined and implicitly embedded in the formulation, which makes the problem formulation very simple. Numerical results show that the power control helps to reduce the interference and therefore significantly (up to 56.3% in the simulated scenario) improves the total spectrum utilization.
Miao Ma, Danny H. K. Tsang

Dynamic Spectrum Sharing in Cognitive Radio Femtocell Networks

(Invited Paper)
Femtocell is envisioned as a highly promising solution to tackle the communications in the indoor environments, which has been a very challenging problem for mobile network operators. Currently, the spectrum allocated to femtocells is from the same licensed spectrum of macrocells, and the same mobile network operator. In this case, the capacity of femtocell networks may be largely limited due to the finite number of licensed spectrum bands and also the interference with other femtocells and macrocells. In this paper, we propose a radically new communications paradigm by incorporating cognitive radio in femtocell networks (COGFEM). In COGFEM, the cognitive radio enabled femtocells are able to access licensed spectrum bands not only from macrocells but also from other licensed systems (e.g. TV systems). Thus, the co-channel interference in femtocells can be greatly reduced and the network capacity can be significantly improved. We formulate a joint channel allocation and power control problem in COGFEM, and present two intelligent algorithms for efficient spectrum sharing in COGFEM. Results indicate that COGFEM is able to achieve much higher capacity than the femtocell networks which does not employ agile spectrum access.
Jie Xiang, Yan Zhang, Tor Skeie

Session 7: Cross-Layer Design & DSL Technologies

Cross-Layer Routing Method for the SCTP with Multihoming MIPv6

The multihoming is regarded as a kind of technology to provide wide-band and relaible network service. The protocol called Stream Control Transmission Protocol (SCTP) [1] can manage the multi-homed nodes to realize a highly-available data transfer capability in the Transport Layer. An SCTP node may keep a combination of the sets of the eligible source and destination transport addresses. The node can detect if a transport address is out of service by periodical messaging which is called HEARTBEAT in SCTP. If the HEARTBEAT is unacknowledged, the node will change to send data via another transport address which is with a HEARTBEAT ACK. The multi-homed mobility nodes, such as the cellphones implemented with both WiFi and 3G, are widely used in the world. Mobility Support in IPv6 (Mobile IPv6, MIPv6) [2] is a protocol to provide a mobility function in IP layer. However the SCTP is not a protocol designed for the moving nodes, such as the nodes using the Mobile IP (MIP). Also there is an enhanced SCTP called mSCTP [3] which enables the mobility at the Transport Layer. But the mSCTP is not designed for the multihoming Mobile IP. In this paper, we suggest a new cross-layer routing method to use the SCTP with the multihoming MIPv6. Our proposal is mobile node can use SCTP to select an optimized transport peer in real time.
Hongbo Shi, Tomoki Hamagami

Challenges and Solutions in Vectored DSL

VDSL2 is the latest generation of DSL technology, and aims to provide data-rates in excess of 100 Mbps to the home to enable next generation, high bandwidth services. Such high data-rates are achieved by transmitting at frequencies up to 30 MHz. Unfortunately transmitting at such high frequencies over twisted-pair leads to strong crosstalk between the lines. To address this issue crosstalk cancellation and precoding were developed, techniques known collectively as vectoring. The ITU is now finalizing the first version of the G.vector standard which specifies how vectoring should be implemented. This paper presents some of the more interesting problems that have been encountered in the development of this standard, and shows how creative solutions, which take advantage of the unique characteristics of the DSL environment, have helped develop vectoring from theory into a practical technology that will soon be ready for commercial deployment.
Raphael Cendrillon, Fang Liming, James Chou, Guozhu Long, Dong Wei

IWATA Workshop

Session 1

Analysis and Suppression of MAI in WiMAX Uplink Communication System with Multiple CFOs

Nowadays, OFDMA (Orthogonal Frequency Division Multiple Access) technique has been used in WiMAX communication system to achieve very high data rate as well as multi-user service. However, similar with other OFDM-based systems, OFDMA system is very sensitive to frequency synchronization errors, especially in the uplink communications where different users always have different CFOs (Carrier Frequency Offset). When multiple CFOs exist, the orthogonality which separates different subcarriers will be lost, and ICI (Inter Carrier Interference) as well as MAI (Multi-Access Interference) will be generated to disturb the received signals. Then, the system performance will be highly degraded. To overcome this problem, it is of great importance to do research on the suppression to the interferences caused by multiple CFOs. In this paper, we first analyze the interferences, including ICI and MAI, caused by multiple CFOs in the uplink communications of OFDMA system. Next, the suppression method based on block type pilots is proposed to overcome the interferences simultaneously. Compared with other interference suppression methods, the proposed method could directly get the interference components from inverse matrix, thus it doesn’t need to do the CFO estimation. From the simulation results, it can be seen that the multiple CFOs will make serious degradation to the system performance. But through the proposed suppression algorithm, the system performance can be significantly improved.
Xiupei Zhang, Heung-Gyoon Ryu

Capacity of Two-Way Relay Channel

This paper investigates the capacity of a wireless two-way relay channel in which two end nodes exchange information via a relay node. The capacity is defined in the information-theoretic sense as the maximum information exchange rate between the two end nodes. We give an upper bound of the capacity by applying the cut-set theorem. We prove that this upper bound can be approached in low SNR region using “separated” multiple access for uplinks from the end nodes to the relay in which the data from the end nodes are individually decoded at the relay; and network-coding broadcast for downlinks from the relay to the end nodes in which the relay mixes the information from end nodes before forwarding. We further prove that the capacity is approachable in high SNR region using physical-layer network coding (PNC) multiple access for uplinks, and network-coding broadcast for downlinks. From our proof and observations, we conjecture that the upper bound may be achieved with PNC in all SNR regions.
Shengli Zhang, Soung Chang Liew, Hui Wang, Xiaohui Lin

Session 2

DP Matching Approach for Streaming Contents Detection Using Traffic Pattern

Since the video streaming technology has become widespread, the security of video contents has gained more importance. Our research group previously envisioned a video leakage detection method for streaming contents that makes use of traffic patterns extracted from only traffic volume information obtained from routers. However, as the background traffic increases, packet delay and jitter increase. As a consequence, the detection accuracy decreases. In this paper, we propose a new robust method, which is more resilient to increasing packet delay and jitter by improving the generation process of traffic patterns. In addition, we solve another problem induced by packet loss by using Dynamic Programming (DP) matching. Finally, we evaluate the influence of the background traffic on streaming video detection and discuss the results.
Kazumasa Matsuda, Hidehisa Nakayama, Nei Kato

A Linear Precoding Design for Multi-Antenna Multicast Broadcast Services with Limited Feedback

The provision for spectrally efficient multicast broadcast services (MBS) is one of the key functional requirements for next generation wireless communication systems. The challenge inherent to MBS is to ensure that all MBS users can be served, and one effective solution to this problem is to employ MIMO multicast transmit precoding. In previous works on MIMO multicast transmit precoding design, the authors either assumed 1) perfect transmitter-side channel state information (CSIT) or 2) special channel conditions that facilitate precoder design with imperfect CSIT. In this paper, we focus on transmit precoding design for MBS where the CSIT is obtained via limited feedback. In addition, we analyze the average minimum receive signal-noise-ratio (RxSNR) among the MBS users and study the order of growth with respect to the number of MBS users and the number of feedback bits. Finally, we propose a threshold based feedback reduction scheme and study the tradeoff between feedback cost and performance loss.
Eddy Chiu, Vincent K. N. Lau

Quantized Beamforming Technique for LTE-Advanced Uplink

Long term evolution (LTE) standard for uplink transmission is based on single carrier frequency division multiple access (SC-FDMA) to maintain low peak-to-average power ratio (PAPR), which is very valuable for the practical handset design. Recently the usage of codebook-based precoding is thoroughly discussed for the LTE-Advanced (LTE-A) uplink. Among the various precoding schemes, equal gain transmission (EGT) is proposed in this paper because it does not increase any PAPR. Especially, considering nonlinear transmit power amplifier model in uplink, EGT is superior to any other precoding schemes. Theoretical analysis of precoding schemes’ PAPR is presented under quasistatic flat fading channel, and link-level bit error rate (BER) is simulated to corroborate the anticipated results.
Young Ju Kim, Xun Li


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