An OFDM-TDMA/SA MAC Protocol with QoS Constraints for Broadband Wireless LANs

Orthogonal frequency division multiplexing (OFDM) is an important technique to support high speed transmission of broadband traffic in wireless networks, especially broadband wireless local area networks (LANs). Based on OFDM, a new multiple access scheme, called OFDM-TDMA with subcarrier allocation (OFDM-TDMA/SA), is proposed in this paper. It provides more flexibility in resource allocation than other multiple access schemes such as OFDM-TDMA, OFDM-frequency division multiple access (OFDM-FDMA), and orthogonal frequency division multiple access (OFDMA). With OFDM-TDMA/SA, a medium access control (MAC) is designed for broadband wireless LANs. It optimizes bit allocation in subcarriers so that maximum bits are transmitted in each OFDM symbol under a frequency selective fading environment. The OFDM-TDMA/SA MAC protocol also supports three classes of traffic such as guaranteed, controlled-load, and best effort services. Based on the optimum subcarrier bit-allocation algorithm and considering heterogeneous QoS constraints of multimedia traffic, a hierarchical scheduling scheme is proposed to determine the subcarriers and time slots in which a mobile terminal can transmit packets. In such a way, the OFDM-TDMA/SA MAC protocol significantly increases system throughput in a frequency selective fading environment and guarantees QoS of multimedia traffic. Computer simulation is carried out to evaluate the performance of the OFDM-TDMA/SA MAC protocol. Results show that the new MAC protocol outperforms other MAC protocols for OFDM-based wireless LANs. This work was supported by the State of Georgia Yamacraw Project (E21-105).     

Energy efficient TDMA-based MAC protocol associated with GAF for wireless sensor networks

The design of media access control (MAC) protocol for wireless sensor networks (WSNs) with the idea of cross layer attracts more and more attention. People can improve the MAC protocol by obtaining certain information regarding the network layer and physical layer. This article synthesizes and optimizes certain cross-layer protocols which have existed. On the basis of the routing, topology information in the network layer, and transmission power information in the physical layer, the time slot assignment algorithm has been improved in the MAC layer. By using geographical adaptive fidelity algorithm (GAF) to divide the grids, controlling of transmission power and scheduling the work/sleep duty cycle for sensor nodes, a new MAC protocol has been proposed to decrease energy consumption and enlarge the lifetime of WSNs. Simulation results show that the MAC protocol functions well.     

ETPS-MAC: Energy Traffic Priority Scheduling-based QoS-aware MAC protocol for hierarchical WSNs

The evolution of the wireless sensor network (WSN) in recent years has reached its greatest heights and applications are increasing day by day, one such application is Smart Monitoring Systems (SMSs) which is in vision of implementation in every urban and rural areas. The implementation of WSN architecture in SMS needs an intelligent scheduling mechanism that efficiently handles the dynamic traffic load without sacrificing the energy efficiency of network. This paper presents a centralized TDMA scheduling based medium access control (MAC) protocol, called Energy Traffic Priority Scheduling MAC (ETPS-MAC) that accommodates variable traffic load while maintaining Quality-of-Service (QoS) assurance in hierarchical WSNs. The ETPS-MAC protocol employs priority scheduling algorithm which considers two factors for assigning priority, the energy factor and the traffic load factor to avoid packet buffering and maintains minimum data packet delay in case of high traffic load. Moreover, a novel rank-based clustering mechanism in FPS-QMAC protocol prolongs the network lifetime by minimizing the distance between the cluster head (CH) and the base station (BS). Both analytical and simulation models demonstrate the superiority of the ETPS-MAC protocol in terms of energy consumption, transmission delay, data throughput and message complexity when compared with the existing TDMA based MAC protocols.     

多信道车载网中基于时分多址的MAC改进算法

车载网(VANETs)需提供时延敏感的安全应用和非安全应用的通信服务.这就使得媒体接入控制(MAC)协议既要满足安全消息的时延和可靠率,又要保证非安全消息的服务信道利用率,给MAC的设计提出了挑战.为此,提出基于时分多址的MAC改进算法(I-TDMA-MAC).I-TDMA-MAC算法在每个同步帧内给每辆车分配两个子时隙,旨在提高无碰撞信道接入率和安全消息的传递率.同时,对空闲时隙采取重分配策略,并基于最短作业优先准则(SJF)给空闲时隙设置优先级,旨在提高服务信道利用率.仿真结果表明,提出的I-TDMA-MAC算法的安全消息传递率高达99%,当车流密度到达100 vehicle/km时,服务信道利用率接近于90%.     

基于动态门限的战术数据链MAC协议

战术数据链（TDL）的作用就是在战场上能够更准确、有效和快速地传递战术情报。随着军事信息技术的发展,战场上的节点数量和传输数据呈现快速增长趋势。传统的战术数据链媒介访问控制（MAC）协议为了保证QoS,一般采用固定资源分配的多址访问算法,如TDMA,在面对大容量、高速率的需求时缺乏灵活性和有效性。为此,研究了基于统计优先级多址访问（SPMA）算法,提出了直接映射和差分趋势两种动态门限方法。仿真结果表明,动态门限比固定门限能够有效提高系统效率,更接近目标信道忙闲比设计,并且在相同负载下网络吞吐量也较固定门限高。     

Parallel relay‐assisted three‐phase MIMO space division multiple access transmission for multi‐hop throughput improvement

Multi‐hop communications equipped with parallel relay nodes is an emerging network scenario visible in environments with high node density. Conventional interference‐free medium access control (MAC) has little capability in utilizing such parallel relays because it essentially prohibits the existence of co‐channel interference and limits the feasibility of concurrent communications. This paper aims at presenting a cooperative multi‐input multi‐output (MIMO) space division multiple access (SDMA) design that uses each hop's parallel relay nodes to improve multi‐hop throughput performance. Specifically, we use MIMO and SDMA to enable concurrent transmissions (from multiple Tx nodes to single/multiple Rx nodes) and suppress simultaneous links' co‐channel interference. As a joint physical layer (MAC/PHY) solution, our design has multiple MAC modules including load balancing that uniformly splits traffic packets at parallel relay nodes and multi‐hop scheduling taking co‐channel interference into consideration. Meanwhile, our PHY layer modules include distributive channel sounding that exchanges channel information in a decentralized manner and link adaptation module estimating instantaneous link rate per time frame. Simulation results validate that compared with interference‐free MAC or existing Mitigating Interference using Multiple Antennas (MIMA‐MAC), our proposed design can improve end‐to‐end throughput by around 30% to 50%. In addition, we further discuss its application on extended multi‐hop topology. Copyright © 2012 John Wiley & Sons, Ltd.     

Terminal‐Assisted Hybrid MAC Protocol for Differentiated QoS Guarantee in TDMA‐Based Broadband Access Networks

This paper presents a terminal‐assisted frame‐based packet reservation multiple access (TAF‐PRMA) protocol, which optimizes random access control between heterogeneous traffic aiming at more efficient voice/data integrated services in dynamic reservation TDMA‐based broadband access networks. In order to achieve a differentiated quality‐of‐service (QoS) guarantee for individual service plus maximal system resource utilization, TAF‐PRMA independently controls the random access parameters such as the lengths of the access regions dedicated to respective service traffic and the corresponding permission probabilities, on a frame‐by‐frame basis. In addition, we have adopted a terminal‐assisted random access mechanism where the voice terminal readjusts a global permission probability from the central controller in order to handle the ‘fair access’ issue resulting from distributed queuing problems inherent in the access network. Our extensive simulation results indicate that TAF‐PRMA achieves significant improvements in terms of voice capacity, delay, and fairness over most of the existing medium access control (MAC) schemes for integrated services.     

A novel QoS‐aware MAC protocol for voice services over IEEE 802.11‐based WLANs

With the pervasive growth in the popularity of IEEE 802.11‐based wireless local area networks (WLANs) worldwide, the demand to support delay‐sensitive services such as voice has increased very rapidly. This paper provides a comprehensive survey on the medium access control (MAC) architectures and quality of service (QoS) provisioning issues for WLANs. The major challenges in providing QoS to voice services through WLAN MAC protocols are outlined and the solution approaches proposed in the literature are reviewed. To this end, a novel QoS‐aware wireless MAC protocol, called hybrid contention‐free access (H‐CFA) protocol and a call admission control technique, called traffic stream admission control (TS‐AC) algorithm, are presented. The H‐CFA protocol is based on a novel idea that combines two contention‐free wireless medium access approaches, that is, round‐robin polling and time‐division multiple access (TDMA)‐like time slot assignment, and it increases the capacity of WLANs through efficient silence suppression. The TS‐AC algorithm ensures efficient admission control for consistent delay‐bound guarantees and further maximizes the capacity through exploiting the voice characteristic that it can tolerate some level of inconsecutive packet loss. The benefits of the proposed schemes are demonstrated in the simulations results. Copyright © 2008 John Wiley & Sons, Ltd.     

QoS‐based space‐frequency prefiltering for TDD MC‐CDMA systems in slowly time‐varying channels

This work presents a space‐frequency prefiltering scheme for slowly time‐varying TDD MC‐CDMA downlink communications with multiple antennas at the base station (BS). Unlike the conventional spatially uncorrelated block fading channel model, both channel variation in each packet and spatial correlation are considered in the design. In the TDD mode, the mobile terminals (MTs) transmit training signals at the end of each uplink packet. In the following downlink packet, the BS computes the signal weights on different antennas and subcarriers for each MT in each symbol period based on the channel state predicted from the received training signals. The goal is to minimize the total required transmit power while keeping the received signal‐to‐interference‐plus‐noise ratio (SINR) as the target for each MT. Moreover, the maximum packet length for satisfying the SINR requirements has been determined. The results indicate that the total required transmit power can be reduced by a lower mobile speed or more BS antennas. As a result, the maximum packet length can be extended in virtue of the power reduction. Copyright © 2008 John Wiley & Sons, Ltd.     

FHCF: A Simple and Efficient Scheduling Scheme for IEEE 802.11e Wireless LAN

The IEEE 802.11e medium access control (MAC) layer protocol is an emerging standard to support quality of service (QoS) in 802.11 wireless networks. Some recent work shows that the 802.11e hybrid coordination function (HCF) can improve significantly the QoS support in 802.11 networks. A simple HCF referenced scheduler has been proposed in the 802.11e which takes into account the QoS requirements of flows and allocates time to stations on the basis of the mean sending rate. As we show in this paper, this HCF referenced scheduling algorithm is only efficient and works well for flows with strict constant bit rate (CBR) characteristics. However, a lot of real-time applications, such as videoconferencing, have some variations in their packet sizes, sending rates or even have variable bit rate (VBR) characteristics. In this paper we propose FHCF, a simple and efficient scheduling algorithm for 802.11e that aims to be fair for both CBR and VBR flows. FHCF uses queue length estimations to tune its time allocation to mobile stations. We present analytical model evaluations and a set of simulations results, and provide performance comparisons with the 802.11e HCF referenced scheduler. Our performance study indicates that FHCF provides good fairness while supporting bandwidth and delay requirements for a large range of network loads. Pierre Ansel received a multidisciplinary in-depth scientific training in different fields such as Pure and Applied Mathematics, Physics, Mechanics, Computer Science and Economics from the Ecole Polytechnique, Palaiseau, France. Then, he joined the Ecole Nationale Superieure des Telecommunications, Paris, France in 2005 where he went further into electronics, databases, computer network security and high speed networks. He received a multidisciplinary master of sciences degree and an additional master of sciences degree in telecommunications in 2005. He did a summer internship in 2003 in INRIA, Sophia Antipolis, France where he worked on the Quality of Service in 802.11 networks at Planete Group, France. Then in 2004, he joined France Telecom R&D, Issy-les-Moulineaux, France to work on Intranet Security issues. He designed a WiFi security supervision architecture based on WiFi Intrusion Detection Sensors. He is currently a French civil servant and belongs to the French Telecommunications Corps. Qiang Ni received the B.Eng., M.Sc. and Ph.D. degrees from Hua Zhong University of Science and Technology (HUST), Wuhan City, China in 1993, 1996 and 1999 respectively. He is currently a faculty member in the Electronic and Computer Engineering Division,School of Engineering and Design, Brunel University, West London, U.K. Between 2004 and 2005 he was a Senior Researcher at the Hamilton Institute, National University of Ireland, Maynooth. From 1999 to 2001, he was a post-doctoral research fellow in the multimedia and wireless communication laboratory, HUST, China. He visited and conducted research at the wireless and networking group of Microsoft Research Asia Lab during the year of 2000. From Sept. 2001 until may 2004, he was a research staff member at the Planète group of INRIA Sophia Antipolis France. Since 2002, he has been active as a voting member at the IEEE 802.11 wireless LAN standard working group. His current research interests include communication protocol design and performance analysis for wireless networks, cross-layer optimizations, vertical handover and mobility management in mobile wireless networks, and adaptive multimedia transmission over hybrid wired/wireless networks. He has authored /co-authored over 40 international journal/conference papers, book chapters, and standard drafts in this field. He is a member of IEEE. E-mail: Qiang.Ni@ieee.org Thierry Turletti received the M.S. (1990) and the Ph.D. (1995) degrees in computer science both from the University of Nice – Sophia Antipolis, France. He has done his PhD studies in the RODEO group at INRIA Sophia Antipolis. During the year 1995–96, he was a postdoctoral fellow in the Telemedia, Networks and Systems group at LCS, MIT. He is currently a research scientist at the Planete group at INRIA Sophia Antipolis. His research interests include multimedia applications, congestion control and wireless networking. Dr. Turletti currently serves on the Editorial Board of Wireless Communications and Mobile Computing.     

Linear and non‐linear space diversity combining algorithms over fading channels in TDMA systems

This paper investigates the performances of various adaptive algorithms for space diversity combining in time division multiple access (TDMA) digital cellular mobile radio systems. Two linear adaptive algorithms are investigated, the least mean square (LMS) and the square root Kalman (SRK) algorithm. These algorithms are based on the minimization of the mean‐square error. However, the optimal performance can only be obtained using algorithms satisfying the minimum bit error rate (BER) criterion. This criterion can be satisfied using non‐linear signal processing techniques such as artificial neural networks. An artificial neural network combiner model is developed, based on the recurrent neural network (RNN) structure, trained using the real‐time recurrent learning (RTRL) algorithm. It is shown that, for channels characterized by Rician fading, the artificial neural network combiners based on the RNN structure are able to provide significant improvements in the BER performance in comparison with the linear techniques. In particular, improvements are evident in time‐varying channels dominated by inter‐symbol interference. Copyright © 2001 John Wiley & Sons, Ltd.     

Downlink multiple access schemes for transmitted reference pulse cluster UWB systems

Transmitted reference pulse cluster (TRPC) signaling was recently proposed for low data rate ultra‐wideband communications. Compared with the conventional transmitted reference (TR), TRPC has a more compact and uniform spacing for the reference and data pulses and therefore solves the implementation problem posed by the long delay line requirement in the conventional TR. In this paper, downlink multiple access issue is further investigated for TRPC systems. According to the TRPC signaling structure, both code division multiple access (CDMA) and time division multiple access (TDMA) methods are discussed. Theoretical analysis and simulation results show that TDMA outperforms CDMA in both bit error rate performance and throughput. Copyright © 2010 John Wiley & Sons, Ltd.     

An efficient MAC protocol for multi‐channel mobile ad hoc networks based on location information

This paper considers the channel assignment problem in a multi‐channel MANET environment. We propose a scheme called GRID, by which a mobile host can easily determine which channel to use based on its current location. In fact, following the GSM style, our GRID spends no communication cost to allocate channels to mobile hosts since channel assignment is purely determined by hosts' physical locations. We show that this can improve the channel reuse ratio. We then propose a multi‐channel MAC protocol, which integrates GRID. Our protocol is characterized by the following features: (i) it follows an ‘on‐demand’ style to access the medium and thus a mobile host will occupy a channel only when necessary, (ii) the number of channels required is independent of the network topology, and (iii) no form of clock synchronization is required. On the other hand, most existing protocols assign channels to a host statically even if it has no intention to transmit [IEEE/ACM Trans. Networks 1995; 3 (4):441–449; 1993; 1 (6): 668–677; IEEE J. Selected Areas Commun. 1999; 17 (8):1345–1352], require a number of channels which is a function of the maximum connectivity [IEEE/ACM Trans. Networks 1995; 3 (4):441–449; 1993; 1 (6): 668–677; Proceedings of IEEE MILCOM'97, November 1997; IEEE J. Selected Areas Commun. 1999; 17 (8):1345–1352], or necessitate a clock synchronization among all hosts in the MANET [IEEE J. Selected Areas Commun. 1999; 17 (8):1345–1352; Proceedings of IEEE INFOCOM'99, October 1999]. Through simulations, we demonstrate the advantages of our protocol. Copyright © 2005 John Wiley & Sons, Ltd.     

低WSN服务能耗的MAC协议实现

为解决WSN服务能耗和服务质量问题,提出了一种无线传感器网络介质访问控制协议WTRP-S,分析比较了WTRP-S,WTRP和IEEE802.15.4MAC的性能,建立了节点启动调度模型。仿真结果表明:在数据业务大的网络中,该协议既能保证服务质量,在节点关闭通信模块中能够节省更多能量,使得整体能耗降低,WTRP-S适用于能量受限的无线传感器网络。     

A distributed polling service‐based MAC protocol testbed

Medium access control (MAC) protocols play a vital role in wireless networking. It is well‐known that the high control overhead of IEEE 802.11 MAC is the limiting factor on the throughput and delay performance of wireless networks. In our prior work, three polling service‐based medium access control protocols (PSMACs) are developed to amortize the high control overhead over multiple frame transmissions, thus achieving higher efficiency. Both analysis and simulations are conducted to validate the efficacy of the proposed protocols. In this paper, we extend this work by implementing the distributed version of PSMAC, i.e., PSMAC 2, on the GNU Radio and universal software radio peripheral (GNU Radio/USRP) platform. We discuss various design considerations and challenges of prototyping PSMAC 2 and carry out extensive experimental studies with the GNU Radio/USRP PSMAC testbed. Our experimental results are found to be consistent with the theoretical study reported in our prior work and validate the advantages of PSMAC under a realistic wireless channels. Copyright © 2013 John Wiley & Sons, Ltd.     

A multi‐channel cooperative clustering‐based MAC protocol for V2V communications

The Internet of vehicles (IoV) is an emerging networking technology, which can support information sharing and interactions among users, vehicles, and infrastructures. Various applications can be provided by IoVs, and they have very different quality‐of‐service (QoS) requirements. It is a great challenge to design an efficient MAC protocol to meet the different QoS demands of various applications in IoVs, because of unreliable links and high vehicle mobility. On the other hand, cooperative communication is effective in mitigating wireless channel impairments by utilizing the broadcast nature of wireless channels. In this paper, a multi‐channel cooperative clustering‐based MAC (MCC‐MAC) protocol, under the Dedicated Short Range Communication (DSRC) multi‐channel architecture, is presented to improve the transmission reliability of safety messages and provision QoS for different applications in IoVs. Further, we analyze the performance of MCC‐MAC, in terms of average transmission delay. In addition, extensive simulations with ns‐2 are conducted to demonstrate the performance of the proposed MCC‐MAC. Copyright © 2016 John Wiley & Sons, Ltd.     

Ad Hoc网络中具有QoS保障的同步MAC协议

介绍了Ad Hoc网络中保障实时业务QoS要求的时间同步多址接入协议。该类协议以时分多址为基础,通过资源预留为实时业务预约固定的时隙,赋予实时业务接入信道的优先权,保证了实时业务的接入延时,延时抖动以及吞吐量等QoS指标,为Ad Hoc网络支持多媒体业务的接入奠定了基础。     

Space‐time diversity‐enhanced QoS provisioning for real‐time service over MC‐DS‐CDMA based wireless networks

In order to support the quality‐of‐service (QoS) requirements for real‐time traffic over broadband wireless networks, advanced techniques such as space‐time diversity (STD) and multicarrier direct‐sequence code division multiple access (MC‐DS‐CDMA) are implemented at the physical layer. However, the employment of such techniques evidently affects the QoS provisioning algorithms at the medium access control (MAC) layer. In this paper, we propose a space‐time infrastructure and develop a set of cross‐layer real‐time QoS‐provisioning algorithms for admission control, scheduling, and subchannel‐allocations. We analytically map the parameters characterizing the STD onto the admission‐control region guaranteeing the real‐time QoS. Our analytical analyses show that the proposed algorithms can effectively support real‐time QoS provisioning. Also presented are numerical solutions and simulation results showing that the STD can significantly improve the QoS provisioning for real‐time services over wireless networks. Copyright © 2007 John Wiley & Sons, Ltd.     

A Priority MAC Protocol to Support Real-Time Traffic in Ad Hoc Networks

Carrier sense multiple access and its variants have been widely used in mobile ad hoc networks. However, most existing access mechanisms cannot guarantee quality for real-time traffic. This paper presents a distributed medium access control protocol that provides multiple priority levels for stations to compete for the wireless channel. One common channel is assumed to be shared by all stations. Stations are assumed to be able to hear each other (i.e., the network is fully connected). The channel is accessed by stations according to their priorities, and for stations with the same priority, they send frames in a round robin manner. The channel access procedure is divided into three stages: priorities classification period, ID initialization period, and transmission period. Simulation results indicate that our protocol provides high channel utilization and bounded delays for real-time frames.     

IEEE 802.11 medium access control enhancements based on simultaneous multiple‐input multiple‐output bandwidth sharing

The demand for higher data rate has spurred the adoption of multiple‐input multiple‐output (MIMO) transmission techniques in IEEE 802.11 products. MIMO techniques provide an additional spatial dimension that can significantly increase the channel capacity. A number of multiuser MIMO system have been proposed, where the multiple antenna at the physical layer are employed for multiuser access, allowing multiple users to share the same bandwidth. As these MIMO physical layer technologies further evolve, the usable bandwidth per application increases; hence, the average service time per application decreases. However, in the IEEE 802.11 distributed coordination function‐based systems, a considerable amount of bandwidth is wasted during the medium access and coordination process. Therefore, as the usable bandwidth is enhanced using MIMO technology, the bandwidth wastage of medium access and coordination becomes a significant performance bottleneck. Hence, there is a fundamental need for bandwidth sharing schemes at the medium access control (MAC) layer where multiple connections can concurrently use the increased bandwidth provided by the physical layer MIMO technologies. In this paper, we propose the MIMO‐aware rate splitting (MRS) MAC protocol and examine its behavior under different scenarios. MRS is a distributed MAC protocol where nodes locally cooperate with one another to share bandwidth via splitting the spatial channels of MIMO systems. Simulation results of MRS protocol are obtained and compared with those of IEEE 802.11n protocol. We show that our proposed MRS scheme can significantly outperform the IEEE 802.11n in medium access delay and throughput. Copyright © 2012 John Wiley & Sons, Ltd.