An advanced channel access scheme for integrated multimediaservices with various bit rates in CDMA networks

For efficient code sharing among users, a wireless medium access control (MAC) protocol for CDMA networks is proposed, which supports connection-oriented, as well as connectionless, services and provides the various bit rates needed for the integrated multimedia services. The proposed MAC protocol allows mobile terminals to use multiple slots and spreading codes based on contention and reservation. Optimum frequency resources are allocated to the connection-oriented and connectionless services with various bit rates. Waiting and response times in the first contention are reduced, and the overall mean delay time is typically minimized in the case of connectionless bulky traffic     

Busy tone contention protocol: a new high‐throughput and energy‐efficient wireless local area network medium access control protocol using busy tone

Design of an efficient wireless medium access control (MAC) protocol is a challenging task due to the time‐varying characteristics of wireless communication channel and different delay requirements in diverse applications. To support variable number of active stations and varying network load conditions, random access MAC protocols are employed. Existing wireless local area network (WLAN) protocol (IEEE 802.11) is found to be inefficient at high data rates because of the overhead associated with the contention resolution mechanism employed. The new amendments of IEEE 802.11 that support multimedia traffic (IEEE 802.11e) are at the expense of reduced data traffic network efficiency. In this paper, we propose a random access MAC protocol called busy tone contention protocol (BTCP) that uses out‐of‐band signals for contention resolution in WLANs. A few variants of this protocol are also proposed to meet the challenges in WLAN environments and application requirements. The proposed BTCP isolate multimedia traffics from background data transmissions and gives high throughput irrespective of the number of contending stations in the network. As a result, in BTCP, admission control of multimedia flows becomes simple and well defined. Studies of the protocol, both analytically and through simulations under various network conditions, have shown to give better performance in comparison with the IEEE 802.11 distributed coordination function. Copyright © 2011 John Wiley & Sons, Ltd.     

车用自组网媒体访问控制机制改进

为提升车用自组网传输音频、视频的服务质量,对基于IEEE802.11p的车用无线接入技术MAC机制进行改进,提出竞争窗口自适应EDCA机制。仿真实验表明,竞争窗口自适应EDCA机制有效地降低了车用自组网中音频、视频流的传输时延、时延抖动和丢包率,保证了车用自组网传输VoIP、视频会议、音视频流媒体等多媒体业务的服务质量。     

Performance evaluation of candidate MAC protocols for LMCS/LMDSnetworks

Broadband wireless access (BWA) offers attractive features such as ease and speed of deployment, fast realization of revenues, and low infrastructure cost. This paper focuses on medium access control (MAC) alternatives that can find application in an LMDS/LMCS network capable of supporting multimedia traffic. Multifrequency demand assignment TDMA-based schemes appear (at the moment) to be a suitable choice in this context. The selected protocol should be dynamically capable of providing multirate capabilities and quality-of-service guarantees. An obvious candidate for the aforementioned purpose is the LMDS-specific MAC proposal in the DAVIC 1.2 recommendation. For purposes of comparison, we also examine the evolving IEEE 802.14 MAC convergence protocol and MCNS (multimedia cable network system) DOCSIS (ITU J-112) MAC standard that are intended to support similar applications and services in an HFC (hybrid fiber coax) environment. The three protocols are examined under noiseless and noisy channel conditions. Previous results on LMDS channel characteristics are summarized and used for modeling noisy channel conditions. The candidate protocols are compared in terms of mean access delay, throughput, and collision multiplicity statistics, when contention of users is involved. The effect of dynamic slot allocation on the performance of the candidate protocols is also examined     

Arbitration Interframe Space‐controlled Medium Access Control: a medium access control protocol guaranteeing absolute priority in wireless local area networks

The demand for multimedia services, such as voice over Internet Protocol, video on demand, information dissemination, and ?le sharing, is increasing explosively in wireless local area networks. These multimedia services require a certain level of QoS. Thus, it is important to provide QoS for multimedia applications. IEEE 802.11e tries to meet the QoS requirement of multimedia services by using Enhanced Distributed Channel Access. This gives more weights to high‐priority tra?c than low‐priority tra?c in accessing the wireless channel. However, Enhanced Distributed Channel Access suffers from many problems such as low aggregate throughput, high collision rates, and ineffective QoS differentiation among priority classes. In this paper, we propose a new medium access scheme, the Arbitration Interframe Space‐controlled Medium Access Control (AC‐MAC), that guarantees absolute priority in 802.11 wireless networks. In AC‐MAC, the AIFS and contention window values are controlled, so that a higher‐priority tra?c can preferentially access and effectively utilize the channel. Extensive simulations show that AC‐MAC can perfectly provide absolute priority and good throughput performance regardless of the number of contending nodes. In the simulation of voice over Internet Protocol service, AC‐MAC provides effective QoS differentiation among services and also meets the high level of QoS requirements. AC‐MAC also adapts quickly in a dynamic environment and provides good fairness among the nodes belonging to the same priority class. Copyright © 2011 John Wiley & Sons, Ltd.     

A Cross-Layer Approach for WLAN Voice Capacity Planning

This paper presents an analytical approach to determining the maximum number of on/off voice flows that can be supported over a wireless local area network (WLAN), under a quality of service (QoS) constraint the authors consider multiclass distributed coordination function (DCF) based medium access control (MAC) that can provision service differentiation via contention window (CW) differentiation. Each on/off voice flow specifies a stochastic delay bound at the network layer as the QoS requirement. The downlink voice flows are multiplexed at the access point (AP) to alleviate the MAC congestion, where the AP is assigned a smaller CW compared to that of the mobile nodes to guarantee the aggregate downlink throughput. There are six-fold contributions in this paper: 1) a nonsaturated multiclass DCF model is developed; 2) a cross-layer framework is proposed, which integrates the network-layer queueing analysis with the multiclass DCF MAC modeling; 3) the channel busyness ratio control is included in the framework to guarantee the analysis accuracy; 4) the framework is exploited for statistical multiplexing gain analysis, network capacity planning, contention window optimization, and voice traffic rate design; 5) a head-of-line outage dropping (HOD) scheme is integrated with the AP traffic multiplexing to further improve the MAC channel utilization; 6) performance of the proposed cross-layer analysis and the associated applications are validated by extensive computer simulations.     

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.     

MAC Layer Admission Control and Priority Re-allocation for Handling QoS Guarantees in Non-cooperative Wireless LANs

Providing QoS guarantee with appropriate service differentiation in IEEE 802.11 wireless LANs is quite desirable. However, users may be selfish and thus rigorously try to maximize their performance by demanding high services even though the network has already saturated. On the other hand, user misbehaviors such as misuse of priority and over-rate transmission pose further harm to performance of existing flows. These application layer non-cooperation makes successful resource allocation very challenging with existing contention based CSMA/CA channel access. In this paper, we propose a MAC layer coordinated QoS framework of admission control and priority re-allocation for quality of services of real-time applications in wireless LANs. Our focus is on priority based MAC schedulers where each user can set its flow priority in order to receive appropriate level of services. With channel condition information such as available bandwidth and mean delay exchanged among neighboring stations, users can enforce admission control based on the perceived channel status and may re-allocate their priorities to accommodate existing flows as desired. User misbehaviors are identified by estimating the flow transmitting rate and matching priority setting, or even punished by assigning appropriate low priorities. Extensive simulations results show that the proposed framework can effectively coordinate wireless users on keeping reserved transmission rate, using appropriate MAC priority, and allocating sufficient resource. Ming Li received his B.S. and M.S. in Engineering from Shanghai Jiao Tong University, China, in 1995 and 1998, respectively. He is currently a Ph.D. candidate in department of Computer Science, University of Texas at Dallas, where he received M.S. degree in Computer Science in Dec. 2001. His research interest includes QoS schemes for mobile ad-hoc networks and multimedia over wireless networks. B. Prabhakaran is with the faculty of Computer Science Department, University of Texas at Dallas. He has been working in the area of multimedia systems: animation & multimedia databases, authoring & presentation, resource management, and scalable web-based multimedia presentation servers. Dr. Prabhakaran received the prestigious National Science Foundation (NSF) CAREER Award in 2003 for his proposal on Animation Databases. He has published several research papers in various refereed conferences and journals in this area. He has served as guest-editor (special issue on Multimedia Authoring and Presentation) for ACM Multimedia Systems journal. He is also serving on the editorial board of Multimedia Tools and Applications journal, Kluwer Academic Publishers. He has also served as program committee member on several multimedia conferences and workshops. B. Prabhakaran has served as a visiting research faculty with the Department of Computer Science, University of Maryland, College Park. He also served as a faculty in the Department of Computer Science, National University of Singapore as well as in the Indian Institute of Technology, Madras, India.     

A short-term fair MAC protocol for WLANs

Designing a medium access control (MAC) protocol that simultaneously provides high throughput and allows individual users to share limited spectrum resources fairly, especially in the short-term time horizon, is a challenging problem for wireless LANs. In this paper, we propose an efficient cooperative MAC protocol with very simple state information that considers only collisions, like the standard IEEE 802.11 MAC protocol. However, contrary to the IEEE 802.11 MAC, the cooperative MAC gives collided users priority to access the channel by assigning them shorter backoff counters and interframe-spaces than users who did not participate in the collision event. In other words, collided users are the only ones allowed to transmit in the following contention period. For the cooperative MAC protocol, we utilize an analytical throughput model to obtain the optimal parameter settings. Simulation results show that the cooperative MAC provides significant improvement in short-term fairness and access delay, while still providing high network throughput.     

A TDMA MAC protocol for multiservice wireless ad hoc networks

Quality of Service (QoS) provision in wireless ad hoc networks requires the support of efficient MAC protocols and Radio Resource Management strategies to efficiently handle the access process and to achieve a high resource reuse. In this context, we present in this paper a MAC proposal capable of providing resource reservation and service differentiation in the medium access level as a basis for guaranteeing end‐to‐end QoS support in higher levels. We propose a TDMA MAC structure based on a frame subdivision consisting of a broadcast control phase and a data phase. We have designed an adaptive strategy to share the resources between both control and data services and a resource reservation strategy for data services that solves the problems stemmed from the contention for the medium, also adding a service differentiation mechanism based on priorities. In addition, we evaluate the impact of a realistic propagation channel considering multipath fading and users interference on the performance of this scheme. In this scenario, we propose modifications to guarantee the reliability and efficiency of both broadcast control and data services, including power control techniques. Copyright © 2009 John Wiley & Sons, Ltd.     

A Multichannel QoS MAC with Dynamic Transmit Opportunity for VANets

One of the most challenging issues facing vehicular networks lies in the design of an efficient MAC protocol due to the mobile nature of nodes and the interference associated with the dynamic environment. Moreover delay constraints for safety applications add complexity and latency requirements to the design. Existing MAC protocols overcome some challenges however don’t provide an integrated solution. Hence, the merit if this work lies in designing an efficient MAC protocol that incorporates various VANet’s challenges in a complete end-to-end solution. In this work, we propose an efficient Multichannel QoS Cognitive MAC (MQOG). MQOG assesses the quality of channel prior to transmission employing dynamic channel allocation and negotiation algorithms to achieve significant increase in channel reliability, throughput and delay constraints while simultaneously addressing Quality of Service. The uniqueness of MQOG lies in making use of the free unlicensed bands. The proposed protocols were implemented in OMNET++ 4.1, and extensive experiments demonstrated a faster and more efficient reception of safety messages compared to existing VANet MAC Protocols. Finally, improvements in delay, packet delivery ratios and throughput were captured.     

Quality-of-service in ad hoc carrier sense multiple access wirelessnetworks

Carrier sense multiple access (CSMA) is one of the most pervasive medium access control (MAC) schemes in ad hoc, wireless networks. However, CSMA and its current variants do not provide quality-of-service (QoS) guarantees for real-time traffic support. This paper presents and studies black-burst (BB) contention, which is a distributed MAC scheme that provides QoS real-time access to ad hoc CSMA wireless networks. With this scheme, real-time nodes contend for access to the channel with pulses of energy-so called BBs-the durations of which are a function of the delay incurred by the nodes until the channel became idle. It is shown that real-time packets are not subject to collisions and that they have access priority over data packets. When operated in an ad hoc wireless LAN, BB contention further guarantees bounded and typically very small real-time delays. The performance of the network can approach that attained under ideal time division multiplexing (TDM) via a distributed algorithm that groups real-time packet transmissions into chains. A general analysis of BB contention is given, contemplating several modes of operation. The analysis provides conditions for the scheme to be stable. Its results are complemented with simulations that evaluate the performance of an ad hoc wireless LAN with a mixed population of data and real-time nodes     

QoS-, Queue-and Channel-Aware Packet Scheduling for Multimedia Services in Multiuser SDMA/TDMA Wireless Systems

With the growing demand for wireless multimedia services and continuing emergence of new multimedia applications, it is necessary for the network to provide various levels of quality of service (QoS) while maximizing the utilization of channel resources. This paper presents an adaptive queuing model and a novel cross-layer packet scheduling algorithm for providing differentiated QoS and effective channel utilization in a space-division-multiple-access/time-division-multiple-access (SDMA/TDMA) system. At the medium access control (MAC) layer, we take into consideration the heterogeneous and bursty nature of multimedia traffic and provide for QoS requirements. At the physical (PHY) layer, we exploit the randomness of the physical channel by incorporating opportunistic scheduling and adopting adaptive modulation and coding (AMC). Performance results obtained by simulations show that by employing the proposed queuing model and packet scheduling algorithm, the system is able to provide for diverse QoS and achieve high throughput.     

Multiple preemptive EDCA for emergency medium access control in distributed WLANs

The increasingly use of wireless local area networks (WLANs) in public safety and emergency network services demands for a strict quality of service (QoS) guarantee especially a large number of users report an emergency for immediate channel access. Unfortunately, the traditional IEEE 802.11e-based enhanced distributed channel access (EDCA) does not support a strict QoS guarantee for life saving emergency traffic under high loads. Previous studies have attempted to enhance the performance of EDCA called the Channel Preemtive EDCA (CP-EDCA) which is a promising idea to support emergency traffic in WLANs. However, CP-EDCA supports a single emergency traffic only (i.e. no emergency service differentiation) with high delays for increased traffic loads. To overcome this problem, we propose a class of EDCA protocol called Multiple Preemption EDCA (MP-EDCA) as a candidate to support multiple emergency traffics under high loads. Each MP-EDCA node can support up to four emergency traffics (life, health, property and environment) with different priorities in addition to support background (non-emergency) traffic. The proposed protocol privileged the high priority life-saving emergency traffic to preempt the services of low priority ones without much starvation in the network to maintain a strict QoS guarantee. The paper evaluates the performance of MP-EDCA through an extensive analysis of simulation outcome. The results obtained show that MP-EDCA outperforms CP-EDCA in achieving lower medium access control and emergency node delays.     

A cross-layer scheme for medium access control with QoS guaranteeing for Ad hoc networks

1 Introduction medium access control (MAC) protocols play a crucial role in determining the performance of Ad hoc networks. However, the design of MAC protocols for Ad hoc networks has traditionally been separated from that of the physical layer. In most …     

A Service Differentiated MAC Protocol for OFDM/TDMA Wireless Systems

1IntroductionAkey goal to achievein next generation wireless net-works is to develop an efficient method to allocate thescarce bandwidth resources among users of differenttypes of traffic in a wireless multi media network. Theentityincharge of performingthat taskisthe MACpro-tocol , which must be able to support various classes oftraffic while guaranteeing their required Quality of Ser-vice (QoS) .Ref .[1] proposes a MACprotocol for ultrahigh-speed radio access system. The new protocol isb…     

Dynamic Code Assignment Medium Access (DCAMA) Protocol for Wireless Integrated Services Networks

A medium access control (MAC) protocol for wireless mobile networks that supports integrated services and provides quality of service (QoS) support is presented and evaluated via simulation. A controlled random access protocol which allows all terminals to dynamically share a group of spread spectrum spreading codes is used. The protocol provides mobile terminals the access control required for efficient transfer of integrated traffic with QoS guarantees. Two service classes are provided; "best-effort" service, with priority queueing, and reserved bandwidth circuit service. The performance of the protocol is evaluated via simulation for traffic consisting of integrated voice, data and compressed video. The performance assessment measure is packet delay.     

An Adaptive Generalized Transmission Protocol for Ad Hoc Networks

Wireless networking and group communication in combination allows groups of dispersed mobile users to collaborate. This paper presents AGENT, a medium access control (MAC) protocol that unifies point-to-point and multi-point transmission services to facilitate group communication in ad hoc networks. Analysis and experiments performed in a simulated ad hoc network demonstrate that AGENT exhibits reliable and stable performance with high spatial bandwidth reuse. Moreover, variation in the proportion of point-to-point and multi-point traffic is shown to have little impact on the overall performance of AGENT. Comparison with the other tested MAC protocols reveals that the performance of AGENT is superior, achieving higher channel utilization and lower access delay.     

A Cooperative MAC Protocol for QoS Enhancement in Wireless USB Networks

Wireless USB (WUSB) is the USB technology merged with WiMedia PHY/MAC based on success of wired USB, and it can be applied to various mobile applications such as laptop, cellular phone, etc. Also, WUSB can provide the better user convenience than wired USB applications as well as be applied to the legacy USB application, since it provides high speed connection between host and devices for the compatibility with USB 2.0 specification and removes the cable among devices using the USB protocol. However the current WUSB protocol can’t prevent the QoS degradation occurred by mobile nodes with low data rate. This problem causes the critical problems in QoS provisioning to isochronous streams and mobile applications. Therefore, we propose a new cooperative MAC protocol for WUSB network with virtual MIMO (multi input multi output) link. Based on instantaneous channel state information among WUSB devices, our proposed protocol can intelligently select the transmission path with higher data rate between WUSB host and WUSB device as well as between WUSB device and WUSB device. Thus our proposed protocol can provide advanced QoS with minimum delay for real-time multimedia services.     

End-to-End Adaptive QoS Provisioning over GPRS Wireless Mobile Network

The General Packet Radio Service (GPRS) offers performance guaranteed packet data services to mobile users over wireless frequency-division duplex links with time division multiple access, and core packet data networks. This paper presents a dynamic adaptive guaranteed Quality-of-Service (QoS) provisioning scheme over GPRS wireless mobile links by proposing a guaranteed QoS media access control (GQ-MAC) protocol and an accompanying adaptive prioritized-handoff call admission control (AP-CAC) protocol to maintain GPRS QoS guarantees under the effect of mobile handoffs. The GQ-MAC protocol supports bounded channel access delay for delay-sensitive traffic, bounded packet loss probability for loss-sensitive traffic, and dynamic adaptive resource allocation for bursty traffic with peak bandwidth allocation adapted to the current queue length. The AP-CAC protocol provides dynamic adaptive prioritized admission by differentiating handoff requests with higher admission priorities over new calls via a dynamic multiple guard channels scheme, which dynamically adapts the capacity reserved for dealing with handoff requests based on the current traffic conditions in the neighboring radio cells. Integrated services (IntServ) QoS provisioning over the IP/ATM-based GPRS core network is realized over a multi-protocol label switching (MPLS) architecture, and mobility is supported over the core network via a novel mobile label-switching tree (MLST) architecture. End-to-end QoS provisioning over the GPRS wireless mobile network is realized by mapping between the IntServ and GPRS QoS requirements, and by extending the AP-CAC protocol from the wireless medium to the core network to provide a unified end-to-end admission control with dynamic adaptive admission priorities.