Tuning radio resource in an overlay cognitive radio network for TCP: greed isn't good [Accepted from Open Call]

In this article we illustrate the performance of Transmission Control Protocol in an overlay cognitive radio network under dynamic spectrum access. We show that the performance of TCP in overlay CR networks that implement DSA to be quite different from its performance in conventional networks, which do not allow DSA. The key difference is that secondary users in an overlay CR network have to cope with a new type of loss called service interruption loss, due to the existence of primary users. We demonstrate on an NS2 simulation testbed the surprising result: Excessive radio resource usage leads to a decrease in aggregate TCP throughput. This behavior is in contrast to the behavior of TCP in conventional networks, where throughput increases monotonically with the available radio resource.     

OverMesh: network-centric computing [Accepted from Open Call]

The communications industry significantly lags behind the personal computing industry in terms of empowering the end user to innovate, as fundamental architectural shifts have yet to occur to push intelligence to the network edge. The decentralization of the telecommunication system to the edge of today's hierarchically formed networks is inevitable with the emergence of key wireless technologies and the proliferation of mobile computing devices and more prevailing usage models. This article envisions a decentralized communication system formed of wireless mesh networks and a highly virtualized, converged computing and communications node-based architecture with emergent management capabilities. We propose to embed the user inside the network to freely associate services and resources such as computing, storage, and bandwidth to rapidly advance network innovation - network-centric computing. This article proposes a novel direction and vision for network-centric computing, expands upon our research, and presents the OverMesh platform from which we have begun work to instantiate this vision. Finally, we expect this new envisioned network to coexist with today's Internet infrastructure and enable a new generation of applications and usage models     

Policy management for ENUM system enabling privacy and security [Accepted from Open Call]

ENUM (Telephone Number Mapping) is a key enabler in the convergence between IP-based networks and the traditional PSTNs that may result in additional complexity in commercial relationships and regulation of the telecommunications sector. In particular, the current ENUM may significantly increase the risk of unscrupulous use of the information managed (e.g., public user identifiers and user/service reachability). The aim of this article is to describe a new functional reference model for ENUM, and provide some new requirements that enable user privacy and security.     

Handover in multihop cellular networks [Accepted from Open Call]

This article introduces various handover scenarios in multihop cellular networks. In addition, this article presents handover schemes where relay stations are located either inside a cell or on the boundary between two adjacent cells and investigates the effects of the deployment position of relay stations to handover performance. The simulation results show that multihop cellular networks for both deployment scenarios can achieve 90 percent throughput increase over single-hop cellular networks. The results also show that the overall throughput of the multihop cellular networks with relay stations inside a cell is higher than for those with relay stations on the boundary between two adjacent cells, whereas the opposite is observed for the throughput of cell-boundary users. The intercell handover latency in multihop cellular networks is increased by 20 ~ 56 percent compared with that in singlehop cellular networks because of the increased number of handovers and signaling overhead. However, by deploying relay stations on the boundary between two adjacent cells, the service-interruption time caused by inter-cell handover is reduced by 80 percent compared with that of single-hop cellular networks.     

Recent advances in amplify-and-forward two-hop relaying [Accepted from Open Call]

In this article we review an important class of wireless cooperation protocols known as amplify-and-forward relaying. One or more low-complexity relay nodes assist the communication between sources and destinations without having to decode the signal. This makes AF relaying transparent to modulation and coding of the source/destination communication protocol. It is therefore a highly flexible technology that also qualifies for application in heterogeneous networks comprising many nodes of different complexity or even standards. Recently, two-way relaying was introduced, which is readily combined with AF relaying. It is a spectrally efficient protocol that allows for bidirectional communication between sources and destinations. In order to investigate the potential of wireless AF relaying, we introduce three distributed network scenarios that differ in the amount of cooperation between nodes. New challenges arise in those networks, and we discuss approaches to overcome them. For the most general case of a completely distributed system, we present coherent relaying solutions that offer a distributed spatial multiplexing gain even for single-antenna nodes. Based on real-world experiments, we validate the feasibility of all schemes in our laboratory.     

Securing wireless implantable devices for healthcare: ideas and challenges [Accepted from Open Call]

Implantable devices hold great potential for pervasive healthcare, enabling the identification, monitoring, and treatment of patients regardless of their location. To realize this goal, these devices must be able to communicate wirelessly with external devices. However, wireless communication presents many vulnerabilities: an attacker can eavesdrop on transmitted information, use implanted devices to track patients, or spoof an implanted device. An attacker even has the potential to cause direct physical harm to a patient, either by forcibly removing an implanted device from the patient or by maliciously sending commands that affect the operation of an implanted device. Addressing these security threats is crucial for implantable devices due to their permanent nature, but it is difficult because of the severe resource constraints facing such devices. This article details the threats that face wireless implantable devices, surveys the work addressing these threats, and identifies open issues for future research.     

OFDM系统无线资源分配综述

简要介绍OFDM系统无线资源分配的概念及研究模型,阐述了OFDM资源分配技术的国内外研究现状,并讨论分析了OFDM资源分配技术研究中存在的问题,展望了OFDM资源分配技术的研究趋势。     

Understanding interference and carrier sensing in wireless mesh networks [Accepted from Open Call]

Wireless mesh networks aim to provide high-speed Internet service without costly network infrastructure deployment and maintenance. The main obstacle in achieving high-capacity wireless mesh networks is interference between the mesh links. In this article, we analyze the carrier sensing and interference relations between two wireless links and measure the impact of these relations on link capacity on an indoor 802.11a mesh network testbed. We show that asymmetric carrier sensing and/or interference relations commonly exist in wireless mesh networks, and we study their impact on the link capacity and fair-channel access. In addition, we investigate the effect of traffic rate on link capacity in the presence of interference.     

On a MIMO-based open wireless architecture: space-time complementary coding [Accepted from Open Call]

This article proposes a MIMO-based open wireless architecture for next-generation wireless systems. The use of space-time complementary coding in the proposed OWA scheme contributes to a great improvement in system performance due to the joint spatial diversity and multiplexing advantages achieved by the STCC-MIMO scheme. The proposed STCC-MIMO-based OWA scheme offers an unified platform that integrates various attractive features, such as link adaptation, spatial diversity and multiplexing trade-off, and accurate channel estimation. The application of innovative pair-wise complementary codes and offset stacking spread spectrum in the STCC-MIMO scheme helps to boost the overall spectral efficiency due to its near interference-free operation. MIMO systems play an extremely important role in 4G wireless, and therefore it is desirable that the OWA support different MIMO configurations. This article shows that the proposed STCC-MIMO scheme offers great flexibility to implement a MIMO system suitable for different diversity and multiplexing requirements     

Opportunities and challenges in using WPAN and WLAN technologies in medical environments [Accepted from Open Call]

The present view of medical environments, where isolated networks are used for IT and medical applications, is changing toward an integrated heterogeneous network scenario that can support a wide range of applications. WPAN and WLAN technologies play a fundamental role in enabling such integrated environment that is expected to support both medical and nonmedical applications. The ultimate goal is to exploit WPAN and WLAN technologies, as well as other wireless networks, such as 3G cellular systems and satellite networks, to support highly efficient medical care delivery, anytime and anywhere. However, the life-critical nature of some medical applications imposes additional challenges that have not been considered in nonmedical scenarios. This article discusses some future scenarios where WLAN and WPAN technologies can be used to provide an integrated and ubiquitous network in medical environments, and identifies the main issues to be addressed in order to meet the QoS requirements of different medical applications when operating in integrated environment     

A new class of floating-point data formats with applications to 16-bit digital-signal processing systems [Accepted from Open Call]

Sixteen-bit, programmable, digital-signal processors suffer from inadequate dynamic range and noise performance due in part to the use of standard data formats with few bits available for numeric precision. A solution to this problem is developed that involves the use of irregular data formats. A new class of irregular floating-point formats is developed. A specific format is derived from this class that provides greater dynamic range and improved noise performance for 16-bit DSP applications. An experiment with one of the new formats is conducted and analyzed, and improved performance is verified. The importance of our work and its potential applications are discussed.     

An efficient radio resource management strategy for adaptive OFDM cellular systems

This paper presents an efficient Radio Resource Management （RRM） strategy for adaptive Orthogonal Frequency Division Multiplexing （OFDM） cellular systems. In the proposed strategy, only those users who have the same distance from their base stations can reuse a same subcarrier. This can guarantee the received Carrier-to-Interference ratio （C/I） of each subcarrier to be acceptable as required by system planning. Then by employing different modulation scheme on each subcarrier according to its received C/I, system spectral efficiency can be gracefully increased. Analytical and simulation results show that the spectral efficiency is improved by 40% without sacrificing the Bit Error Rate （BER） performance and call blocking probability and system capacity of the proposed strategy is better than conventional systems.     

一种适用于GEO卫星移动通信系统流业务的无线资源管理方法

提出了一种适用于GEO卫星移动通信系统流业务的无线资源管理方法,保障在共享信道上传输的流业务的速率和延时需求.该方法由3个功能实体组成：1）接纳控制/信道分配实体,用于接受或拒绝新的资源请求;2）分组调度实体,负责为每个连接提供所需的传输服务,满足传输速率要求;3）质量控制实体,监测目前系统为当前服务提供的QoS是否与签约QoS一致.在NS2仿真平台建立了相应的系统模型,进行了动态仿真.     

An emulator framework for a new radio resource management for QoSguaranteed services in W-CDMA systems

In the context of third-generation (3G) systems a mix of services with different requirements are expected. Consequently, packet scheduling mechanisms for quality of service (QoS) guarantees will play a key role. This paper proposes a new scheduling strategy that makes consistent the target quality in the radio link with the priority level assigned to each user. The performance of such a strategy is assessed by system level simulations and, in order to gain more insight into the difficulties of this optimization problem, it is compared to other alternatives. This work is part of the Wineglass project, within the Fifth Framework Program of the European Commission (IST), where a real time demonstrator including the radio resource management tasks is being developed. Thus, an implementation approach of the proposed scheduling is also described. The implementation is based on lookup tables and this approach is validated by simulation     

A compendium of optimization techniques for green radio resource management

In recent past, along with other sectors, the telecommunication sector has grown enormously that have significant effects both on power expenditure and environmental hazards. Therefore, this paper presents the comprehensive overview about the energy efficiency and green communication. This paper summarizes the efforts that have been made in attaining green wireless communication in the perspective of radio resource management. The key interest in carrying this survey is to indicate those areas for the research that can be flourished more while attaining our goal of green wireless communication. In this article, basic concepts of energy-efficient communications are first introduced and then existing fundamental works and advanced techniques for energy efficiency are summarized, including information-theoretic analysis, OFDMA networks, MIMO techniques, relay transmission, and wireless resource allocation. Some of the important areas in energy-efficient design are also identified for future research.     

Radio resource management and protocol engineering for IEEE 802.16 [Guest Editorial]

The special section features six articles that focus on radio resource management issues in IEEE 802.16/WiMAX-based broadband wireless systems. This guest editorial discusses the major issues pertaining to the topic and summarizes the articles included in this section.     

An overview of configurable computing machines for software radio handsets

The advent of software radios has brought a paradigm shift to radio design. A multimode handset with dynamic reconfigurability has the promise of integrated services and global roaming capabilities. However, most of the work to date has been focused on software radio base stations, which do not have as tight constraints on area and power as handsets. Base station software radio technology progressed dramatically with advances in system design, adaptive modulation and coding techniques, reconfigurable hardware, A/D converters, RF design, and rapid prototyping systems, and has helped bring software radio handsets a step closer to reality. However, supporting multimode radios on a small handset still remains a design challenge. A configurable computing machine, which is an optimized FPGA with application-specific capabilities, show promise for software radio handsets in optimizing hardware implementations for heterogeneous systems. In this article contemporary CCM architectures that allow dynamic hardware reconfiguration with maximum flexibility are reviewed and assessed. This is followed by design recommendations for CCM architectures for use in software radio handsets.     

TD-SCDMA系统混合业务下的无线资源管理算法研究

给出了智能天线技术在系统级研究的理论模型，推导了采用多用户检测和自适应智能天线技术后的容量和负载评估理论模型。基于该模型，给出了一种新的接入控制算法，并为实时多媒体业务提出了一种先进的动态信道分配算法。仿真结果表明，提出的理论模型和无线资源管理算法适用于TD-SCDMA系统，能够显著提高系统性能，用于实际TD-SCDMA网络的规划优化。     

An analysis of pilot symbol assisted modulation for Rayleigh fadingchannels [mobile radio]

The author presents pilot-symbol-assisted modulation (PSAM) on a solid analytical basis, a feature missing from previous work. Closed-form expressions are presented for the bit error rate (BER) in binary-phase-shift-keying (BPSK) and in quadrature-phase-shift-keying (QPSK), for a tight upper bound on the symbol error rate in 16 quadrature-amplitude-modulation (16-QAM), and for the optimized receiver coefficients. The error rates obtained are lower than for differential detection for any combination of signal-to-noise ratio (SNR) and Doppler spread, and the performance is within 1 dB of a perfect reference system under slow-fading conditions and within 3 dB when the Doppler spread is 5% of the symbol rate     

Radio resource management for cooperative wireless communication systems with organized beam-hopping techniques [accepted from open call]

Readiness in deployment and flexibility in radio resource configuration are the main features of future wireless communication systems. A cooperative wireless communication system (CWCS) is proposed to follow the same principle, aiming at improving the overall performance of a wireless system with the support of advanced beam-hopping techniques. In this article, we propose a multiloop radio resource management mechanism for the CWCS based on the organized beam-hopping (OBH) technique. The proposed RRM mechanism enhances the robustness of the CWCS, based on the OBH technique working with fast temporal-spatial variant traffic. The results show that the system performance can be further improved by hybrid transmission and event- driven access management techniques.