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The integration of different wireless networks to provide seamless and continuous network access services is a major issue in beyond-third-generation (B3G) networks. To avoid modifying the existing protocols in the network nodes, the application-level approach is proposed for heterogeneous network integration. In the application-level integration, a mobility gateway (MG) is introduced to serve as an agent through which users can use different kinds of mobile devices through different kinds of networks to access Internet applications. There are two major tasks in an MG, including content format translation and data tunneling for handoff users. When the service area of an MG is larger, the MG must handle the content format translation for more users, and the computation overhead of an MG increases significantly. On the other hand, when the service area of an MG shrinks, a served user more likely hands off between different MGs, and more network resources are consumed to tunnel the data for handoff users. In this paper, an analytical model is proposed, and simulation experiments are conducted to study how to properly plan the service area of an MG so that better system performance can be achieved. Index Terms--Analytical model, application-level integration, content format translation, mobility gateway (MG), tunneling.

We consider the problem of resource allocation for data transfer between the base station and the users within a cell of a wireless telecommunication network with infinite data queues for each user. The aim is to study the tradeoff between the conflicting objectives of maximizing the system throughput and the quality of service (QoS) to an individual user. Using a policy improvement approach based on Markov decision processes, we develop an intuitive and easy-to-implement index policy. We also demonstrate its superior performance over the existing proportional fair metric algorithm through simulation experiments. Index Terms--Data communication, index policies, Markov decision processes (MDPs), resource allocation, scheduling.

In this paper, we propose a novel distributed interleaved random space-time code (IR-STC) designed for multisource cooperation (MSC) employing various relaying techniques, namely, amplify-forward, decode-forward, soft decode-forward, and differential decode-forward. We introduce a two-phase communication regime for our IR-STC-aided MSC and propose a novel structured embedded (SE) random interleaver-generation method. We also characterize the achievable performance of our proposed IR-STC design in conjunction with various relaying techniques communicating over different intersource Nakagami-m fading channels. Index Terms--Cooperative communications, interleaver division multiplexing, relaying, space-time coding.

The iterative exchange of extrinsic information between the K-best sphere detector (SD) and the channel decoder is appealing since it is capable of achieving a near maximum a posteriori (MAP) performance at a moderate complexity. However, the computational complexity imposed by the K-best SD significantly increases when using a large value of K for the sake of maintaining a near-MAP performance in a high-throughput uplink spatial-division multiple access (SDMA) orthogonal frequency-division multiplexing (OFDM) system supporting a large number of users and/or a high number of bits/symbol. This problem is further aggravated when the number of users/mobile stations (MSs) U exceeds that of the receive antennas N at the base station (BS), namely, in the challenging scenario of rank-deficient systems. We demonstrate that the iterative decoding convergence of this two-stage system may be improved by incorporating a unity rate code (URC) having an infinite impulse response, which improves the efficiency of the extrinsic information exchange. Although this results in a slightly more complex three-stage system architecture, it allows us to use a low-complexity SD having a significantly reduced candidate list size [N.sub.cand]. Alternatively, a reduced signal-to-noise ratio (SNR) is required. For example, given a target bit error ratio (BER) of [10.sup.-5] and [N.sub.cand] : 32 for the SD, the three-stage receiver is capable of achieving a performance gain of 2.5 dB over its two-stage counterpart in a rank-deficient SDMA/OFDM 4-quadratic-amplitude modulation (4-QAM) system supporting U = 8 cochannel users and employing N = 4 receive antennas at the BS, namely, in an (8 x 4) system. For the sake of further enhancing the three-stage concatenated receiver, the proposed iterative center-shifting SD scheme and the irregular convolutional codes (IrCCs) are intrinsically amalgamated, which leads to an additional performance gain of 2 dB. Index Terms--Irregular convolutional coding, SDMA-OFDM, spatial division multiple access, sphere decoding, three-stage concatenated coding.

Traditional routing protocols designed for multihop wireless networks, e.g., the mobile ad hoc network (MANET), select a route with the smallest hop count. The end-to-end through-put in the route may not be the maximum when the network has multiple link data rates, as a small hop number implies a large geographic distance (link distance) for each hop. Due to the radio signal attenuation, this results in a low SNR at the receiving node and, consequently, a low available link data rate. Reducing the link distance by using routes with more hop counts can increase the link data rate. However, this may not necessarily improve the end-to-end throughput because more nodes have to be included in the routes. In this paper, we first investigate and analyze the impact of link distance on end-to-end throughput in multirate multihop wireless networks. Analysis and simulation results show that changing the link distance affects the network throughput. To achieve a high network throughput, a proper link distance requirement has to be set for each hop, depending on different parameters such as load density. Based on this finding, we then propose a crossing-layer adaptive searching range (ASR) routing algorithm. ASR can be integrated into existing routing protocols. According to the local network load density, ASR can help improve the network performance by adjusting the link distance in the routes. Index Terms--Crossing-layer protocol, data rate control, link adaptation, multihop wireless networks, network capacity.

Next-generation wireless networks will integrate multiple wireless access technologies to provide seamless mobility to mobile users with high-speed wireless connectivity. This will give rise to a heterogeneous wireless access environment where network selection becomes crucial for load balancing to avoid network congestion and performance degradation. We study the dynamics of network selection in a heterogeneous wireless network using the theory of evolutionary games. The competition among groups of users in different service areas to share the limited amount of bandwidth in the available wireless access networks is formulated as a dynamic evolutionary game, and the evolutionary equilibrium is considered to be the solution to this game. We present two algorithms, namely, population evolution and reinforcement-learning algorithms for network selection. Although the network-selection algorithm based on population evolution can reach the evolutionary equilibrium faster, it requires a centralized controller to gather, process, and broadcast information about the users in the corresponding service area. In contrast, with reinforcement learning, a user can gradually learn (by interacting with the service provider) and adapt the decision on network selection to reach evolutionary equilibrium without any interaction with other users. Performance of the dynamic evolutionary game-based network-selection algorithms is empirically investigated. The accuracy of the numerical results obtained from the game model is evaluated by using simulations. Index Terms--Evolutionary equilibrium, evolutionary game theory, heterogeneous wireless access networks, Nash equilibrium, network selection, replicator dynamics.

In this paper, we extend the results of our previous work, which mainly focuses on homogeneous services, and discuss the heterogeneous scenario. A cross-layer design is proposed for IEEE 802.16/WiMAX networks, in which three modules are added: 1) an M-gated scheduler; 2) an admission controller; and 3) a parameter controller. The parameter setting for the M-gated scheduler is based on performance analysis and different services' features, whereas the admission controller policy is deployed on the theoretical results. Using the probability-generating function, a queuing model is developed for the system under the proposed cross-layer design. In the queuing model, the 'wireless' feature that the capacity of the channel randomly varies with time is considered. Simulations validate the theoretical results and demonstrate the performance of the proposed cross-layer scheme. For real-time services, the proposed scheme can achieve the goal of users' quality-of-service (QoS) demand in most cases and saves more surplus bandwidth for the best effort (BE) service. For BE, the proposed scheme can make a good tradeoff between bandwidth utilization and the left bandwidth for BE. Index Terms--Cross layer, gated service, heterogeneous, scheduling, wireless networks.

Cross-layer optimization solutions have been proposed in recent years to improve the performance of wireless users that operate in a time-varying, error-prone network environment. However, these solutions often rely on centralized cross-layer optimization solutions that violate the layered network architecture of the protocol stack by requiring layers to provide access to their internal protocol parameters to other layers. This paper presents a new systematic framework for cross-layer optimization, which allows each layer to make autonomous decisions to maximize the wireless user's utility by optimally determining what information should be exchanged among layers. Hence, this cross-layer framework preserves the current layered network architecture. Since the user interacts with the wireless environment at various layers of the protocol stack, the cross-layer optimization problem is solved in a layered fashion such that each layer adapts its own protocol parameters and exchanges information (messages) with other layers that cooperatively maximize the performance of the wireless user. Based on the proposed layered framework, we also design a message-exchange mechanism that determines the optimal cross-layer transmission strategies, given the user's experienced environment dynamics. Index Terms--Autonomous decision making, cross-layer optimization, environmental dynamics, information exchange, layered dynamic programming (DP) operator.

Vehicular ad hoc networks (VANETs) allow vehicle-to-vehicle communication and, in particular, vehicle-generated announcements. Provided that the trustworthiness of such announcements can be guaranteed, they can greatly increase the safety of driving. A new system for vehicle-generated announcements is presented that is secure against external and internal attackers attempting to send fake messages. Internal attacks are thwarted by using an endorsement mechanism based on threshold signatures. Our system outperforms previous proposals in message length and computational cost. Three different privacy-preserving variants of the system are also described to ensure that vehicles volunteering to generate and/or endorse trustworthy announcements do not have to sacrifice their privacy. Index Terms--Privacy, protocol design, secret sharing, security, threshold signatures, vehicular communications.

Cooperative communications significantly improve the performance of wireless networks with the help of relay nodes, whereas multiuser diversity (MUD) is a kind of diversity inherent in multiuser systems. In this paper, we present a framework to analyze the performance of MUD in the multiuser two-hop cooperative relay networks (TCRNs). Based on this framework, we derive tight closed-form expressions of outage probability and symbol error probability (SEP) for the amplify-and-forward (AF), fixed decode-and-forward (DF), and selective DF protocols with MUD. Both the theoretical analysis and simulations show that in multiuser TCRNs, MUD orders of 2K, K, and 2K can be achieved for AF, fixed DF, and selective DF, respectively (where K is the number of users). Index Terms--Amplify-and-forward (AF), cooperative communications, decode-and-forward (DF), multiuser diversity (MUD), outage probability, relay systems, symbol error probability (SEP).

This paper presents an analytical model of IEEE 802.11e enhanced distributed channel access (EDCA) with a virtual collision handler (VCH). The proposed analytical model provides different access categories (ACs) for supporting the quality of service (QoS) of differentiated services by using different contention window (CW) sizes and arbitration interframe space (AIFS) values in EDCA. The proposed model considers a network of stations, each of which has multiple queues and a VCH for different ACs. Based on the proposed model, we analyze the throughput and delay performance of the EDCA with four different ACs and investigate the effect of the VCH by considering two VCH schemes. The analytical and simulation results show that the proposed analytical model is very accurate for various CW sizes and AIFS values. Index Terms--Enhanced distributed channel access (EDCA), IEEE 802.11e, virtual collision handler (VCH).

In this paper, a code set for an 8.25-Mb/s data rate is proposed for the Institute of Electrical and Electronics Engineers 802.11b system, which can act as a better fallback option than a 5.5-Mb/s data rate when an 11-Mb/s data rate is not sustainable in a large delay-spread channel environment. We present a systematic procedure for the design of the code set. The proposed code set works at significantly higher path loss when compared to an 11-Mb/s data rate in moderate to large delay-spread channel environment. We also discuss the resource requirement for including the proposed data rate in the existing 802.11b transceiver and note that the additional hardware is minimal. Since the current Wireless Fidelity chipsets are enabled with the 802.11g option, we investigated the performance of the proposed data rate and the 6and 9-Mb/s data rates provided by 802.11g, and the results show that the 8.25-Mb/s data rate is a reliable fallback option compared to the 9-Mb/s rate when the 11-Mb/s data rate is not sustainable. The 8.25-Mb/s data rate is shown to work at 1.7 dB higher path loss when compared to the 9-Mb/s rate in a frequently occurring moderate delay-spread channel. Index Terms--Complementary code set, differential phase-shift keying (DPSK), fast Walsh transform, spread spectrum based wireless local area network (WLAN) system, 802.11 big WLAN.

Performance modeling of processor occupancy in a cluster of nodes handling subscriber profile query and update in a code division multiple access (CDMA) mobile switching center (MSC) is presented. The performance models are simple to use and provide accurate predictions.

Emergence of new systems outside the realm of 3rd Generation Partnership Project (3GPP) and ever increasing demands of higher capacities and data rates has motivated the crucial long term evolution of third generation (3G) system towards the new Universal Mobile Telecommunication System (UMTS) terrestrial radio access (UTRA) air interface. The system requirements, design considerations and an outline of the future evolved UTRA air interface are presented.

The bioheat equation is used to solve for the temperature rise of the various tissues including the brain for three anatomical models with 1-mm resolution for exposure to cellular telephones at 835 and 1900 MHz for radiated power levels allowed under the previous and the newly relaxed IEEE RF Safety Standards and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) Standard. It is shown that the temperature increase for parts of brain in excess of 1.3 [degrees]C will result for the radiated power levels allowed under the relaxed RF Safety Standard accepted by the IEEE. This temperature increase is up to 2.5 x and 7.0 x higher than that for the radiated powers allowed for the ICNIRP and the previous IEEE safety guidelines, respectively. Index Terms--Anatomic model of the head, cellular telephones, safety standards, temperature increase in brain.

Due to the powerful error correcting performance, turbo codes have been adopted in many wireless communication standards such as W-CDMA and CDMA2000. Although several low-power techniques have been proposed, power consumption is still a major issue to be solved in practical implementations. Since turbo decoding is classified as a memory-intensive algorithm, reducing memory accesses is crucial to achieve a low power design. To reduce the number of memory accesses for maximum a posteriori (MAP) decoding, this paper proposes an approximate reverse calculation method that can be implemented with simple arithmetic operations such as addition and comparison. Simulation results show that the proposed method applied to the W-CDMA standard reduces the access rate of the backward metric memory by 87% without degrading error-correcting performance. A prototype log-MAP decoder based on the proposed reverse calculation achieves 29 % power reduction compared to a conventional decoder that does not use the reverse calculation. Index Terms--Low power design, maximum a posteriori (MAP) algorithm, memory optimization, reverse calculation, turbo codes, turbo decoding.

A novel error-resilience tool for JPEG 2000 is proposed, based on the concept of ternary arithmetic coders employing a forbidden symbol. The proposed decoder extends the JPEG 2000 capabilities in error-prone scenarios, without violating the standard syntax, and extensive simulations on video sequences show that the proposed decoders largely outperform the standard in terms of PSNR and visual quality.

The IEEE (Institute for Electrical and Electronics Engineers) 802.16 family of standards is developed to achieve wide area, cellular, high data rate transmission for non-line-of-sight terminals. Various system architectures for handling handovers in an 802.16e system based on the capabilities of the current draft standard (802.16e D8) are described.