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).     

基于机器学习的移动自组网MAC协议研究综述

MAC协议设计是移动自组网的一项重要关键技术,主要通过有效的多节点协商机制,实现各节点对空间、时间、频率等有限资源的合理共享,完成各节点的随机接入和资源分配功能。随机接入和资源分配问题通常可用最优化和马尔科夫决策问题表述,机器学习可成为提升移动自组网MAC协议性能的有力手段之一。该综述在分析机器学习和移动自组网MAC协议特点基础上,结合现有研究成果,介绍了基于机器学习的关键技术原理和仿真性能,展望了未来研究方向。现有研究成果表明,基于机器学习的MAC协议设计性能改善显著。     

宽带GEO卫星网络媒体接入控制协议

宽带地球同步轨道（GEO）卫星通信网络中对媒体接入控制协议设计的目的就是在保障用户服务质量的同时提高系统资源利用率。概述了宽带GEO卫星网络的特点,总结了影响媒体接入控制协议性能的主要因素,重点对两种多址接入方案进行分析：基于混合式自适应分配机制的媒体接入控制协议和基于地面请求策略的动态分配多址接入协议。结果表明,提高网络性能的最佳方法是将有效的地面请求策略与合理的资源分配方式相结合。最后,对下一步的研究方向提出了建议。     

一种高效低时延的宽带电力线通信网多跳MAC协议

针对IEEE1901.1宽带电力线通信媒体接入控制(Medium Access Control,MAC)协议涉及到信标时隙利用不充分和控制开销过大等问题,提出了一种高效低时延的宽带电力线通信网多跳MAC协议(Efficient and Low Delay Multi-hop MAC,ELDM-MAC).采用基于节点层级号的信标时隙分配机制,根据邻居表和时隙分配信息计算能够提前进入到载波监听多路访问时隙(Carrier Sense Multiple Access,CSMA)的时间,减少了信标时隙的浪费,提高了信道利用率;同时采用基于拓扑信息的信标帧高效广播机制,删除不大于自身层级号的节点和大于且在两跳范围内的非子孙节点的时隙分配信息,降低了网络控制开销.仿真结果表明,ELDM-MAC协议在信道利用率、平均时延和控制开销等方面都优于IEEE1901.1 MAC协议,更适用于宽带电力线通信网络的实际应用场景.     

North American agreements on ISDN

The work of the North American Integrated Services Digital Network Users Forum (NIUF) is presented, and its relationship to the Accredited Standards Committee T1 and other standards bodies is discussed. The role of the NIUF within the ISDN arena is evident when considering the Federal Information Processing Standard (FIPS) for ISDN and the Transcontinental ISDN Project (TRIP), both of which are described. The relationship of the ISDN FIPS to the Government Open System Interconnection Profile (GOSIP) and the military standard on ISDN are also discussed. A comparison of NIUF agreements/ISDN standards and the Bellcore NI-1 specifications is presented     

The role of satellite communication in the ISDN era

Satellite communications can play an important role in provisioning the next-generation telecommunications services and networks, provided that the protocols specifying these services and networks are satellite-compatible. After a brief discussion of narrowband circuit and packet mode integrated service digital network (ISDN) services, the paper focuses on emerging standards in frame relay, broadband ISDN (BISDN) and universal personal telecommunications (UPT). The specific parameters and procedures of frame relay and BISDN protocols which are affected by a satellite delay are identified, and congestion and resource management functions for frame relay and BISDN are discussed in detail. Specific ground functions and possible on-board functions are identified as potential candidates for implementation via neural network technology. Finally, the implication of UPT standards on satellite networks is discussed.     

基于WSN的能量高效MAC协议研究

介质访问控制(medium access control,MAC)协议能效性直接影响着无线传感器网络的寿命.在阐述能量消耗分布及造成无效功耗原因的基础上,分析了MAC协议的性能评价指标和分类方法;重点围绕能量高效,比较研究了当前一些重要的MAC协议,结果表明不存在满足所有要求的协议,仅仅是在各性能间优化折中;最后展望了无线传感器网络MAC协议进一步的研究趋势.     

ISDN in North America

The North American ISDN Users' Forum (NIUF), intended to bring together the communities involved in shaping a market-driven competitive ISDN, is discussed. These communities include users, service providers, network equipment manufacturers, customer premises-equipment (CPE) manufacturers, and applications software developers. The role of the NIUF in the product development cycle, NIUF activities, and other important ISDN activities that complement the NIUF work are described. The beginning deployment of a national ISDN and a major demonstration of ISDN capability within North America are also discussed. It is argued that the budding cooperation between the NIUF, the standards bodies, the Corporation for Open Systems (COSs), and Bellcore suggests that migration toward a single set of well-defined specifications is underway     

On Channel Adaptive Multiple Access Control without Contention Queue for Wireless Multimedia Services

As tetherless multimedia computing environments are becoming much desired, broadband wireless communication infrastructures for providing wireless multimedia services will play an important role, and thus, are expected to proliferate. However, despite much research efforts have been expended, the multiple access control of the precious bandwidth remains a challenging problem because of the existence of two common drawbacks in the state-of-the-art protocols: (1) channel condition is ignored or not exploited, and (2) inflexible or biased time slots allocation algorithms are used. Indeed, existing protocols mostly ignore the burst errors due to fading and shadowing, which are inevitable in a mobile and wireless communication environment. A few protocols take into account the burst errors but just handle the errors in a passive manner. Most of the existing protocols employ an inflexible or biased allocation algorithm such that over-provisioning may occur for a certain class of users at the expense of the poor service quality received by other users. In this paper, a new MAC protocol, called SCAMA (synergistic channel adaptive multiple access) is proposed. The proposed protocol works closely with the underlying physical layer in that through observing the channel state information (CSI) of each mobile user, the MAC protocol first segregates a set of users with good CSI from requests gathered in the request contention phase of an uplink frame. The MAC protocol then judiciously allocates information time slots to the users according to the respective traffic types, CSI, urgency, and throughput, which are collectively represented by a novel and flexible priority function. Despite that contention request queue is not used in the protocol, the SCAMA protocol is robust in that it can avoid the congestion collapse which occur in other protocols.     

无线传感网混合类MAC协议研究综述

在无线传感网( WSN)体系结构中,介质访问控制( MAC)协议负责调配网络中节点的信道接入,具有保障网络高效通信的重要作用。混合类MAC 协议综合了竞争类MAC 协议以及调度类MAC协议的特点,在融合两种机制的优点的同时克服其缺点,为无线信道资源的分配提供了更加灵活和全面的策略。首先概述了无线传感网MAC协议设计要点及分类,然后重点分析了无线传感网中经典的混合类MAC协议及国内外前沿的研究进展,并进一步归纳对比了各协议运行机制、性能及不足,得出混合类MAC协议的应用相关性及差异性的结论,最后总结了无线传感网混合类MAC协议研究现状并指出了未来的研究重点,以期为相关领域的研究人员提供参考。     

B-ISDN architecture and protocol

The authors discuss the architecture and protocol for broadband ISDN (B-ISDN) based on the CCITT standards. The discussion attempts to address the general concept of B-ISDN architecture and protocol and, whenever possible, present alternatives and the rationale for decisions in the selection of the protocol. B-ISDN is presented as a network evolution, and the impact of the asynchronous transfer mode (ATM) on the network is described. The role of virtual channel and virtual path in B-ISDN is discussed. The B-ISDN protocol structure and lower layer functions comprising the physical, ATM, and adaptation layers are presented, and the tentative trends of signaling and traffic control for the B-ISDN are delineated     

Interworking IEEE 802/FDDI LANs via the ISDN frame relay bearerservice

The author presents a generic architecture for interconnecting LANs (local area networks) through the ISDN (integrated services digital network) bearer services, particularly the frame relay bearer service. The architecture is derived from the IEEE 802.1 MAC (medium access control) bridge and ISDN frame relay standards. An algorithm for MAC/ISDN address resolution that makes minimal use of the WAN (wide area network) bandwidth (which is potentially the most expensive resource) is presented. The algorithm uses a MAC/ISDN address resolution server to resolve addresses for new stations, the resolution in all other cases (e.g. stations moving from the ISDN address to another) being fully distributed. To prevent a server failure from inhibiting communication to new stations, a backup server may be provided. A practical implementation of the architecture has been found capable of supporting full throughput at ISDN hyperchannel rates (384-1920 kb/s) for all IEEE 802.3 frame lengths. Frame relay is seen as having a number of important advantages for LAN interconnection, including the following: a large number of virtual circuits available, giving the potential for a rich interconnection architecture with single-hop connections across the ISDN; and low processing overhead enabling efficient use of ISDN channels, including ISDN hyperchannels (384-1920 kb/s)     

Enhanced Dynamic Bandwidth Allocation Algorithm in Ethernet Passive Optical Networks

As broadband access is evolving from digital subscriber lines to optical access networks, Ethernet passive optical networks (EPONs) are considered a promising solution for next generation broadband access. The point‐to‐multipoint topology of EPONs requires a time‐division multiple access MAC protocol for upstream transmission. In this paper, we propose a new enhanced dynamic bandwidth allocation algorithm with fairness called EFDBA for multiple services over EPONs. The proposed algorithm is composed of a fairness counter controller and a fairness system buffer in the optical line terminal. The EFDBA algorithm with fairness can provide increased capability and efficient resource allocation in an EPON system. In the proposed EFDBA algorithm, the optical line termination allocates bandwidth to the optical network units in proportion to the fairness weighting counter number associated with their class and queue length. The proposed algorithm provides efficient resource utilization by reducing the unused remaining bandwidth made by idle state optical network units.     

A new MAC protocol for broadband wireless communications and its performance evaluation

This paper presents a new Time Division Multiple Access/Frequency Division Duplexing (TDMA/FDD) based Medium Access Control (MAC) protocol for broadband wireless networks, supporting Quality of Service (QoS) for real-time multimedia applications. It also gives the Call Blocking Probability (CBP), packet end-to-end delay and utilization analysis of different service classes, as they are most essential performance criterions in broadband wireless network assessment. The Connection Admission Control (CAC) mechanism in the proposed MAC efficiently organizes the bandwidth allocation for different service classes by means of a fairness based scheduling algorithm. In addition, the simulation model of the proposed MAC scheme is realized by using OPNET Modeler network simulator. The results of the analytical calculations for the CBPs are compared to those of the simulation of the proposed MAC, thus validity of the MAC protocol is proved.     

Why are ISDN standards important?

The advantages offered by the integrated services digital network (ISDN) to US Department of Defense (DoD) communications in terms of interoperability provides a framework for a discussion of ISDN standards. The standards organizations working on ISDN and network protocol standards are described, and their relationship to each other is delineated. The status of the standards being developed is discussed, and those that would be of special interest to the US DoD are examined     

A Tutorial on Cross-Layer Optimization in Wireless Networks

This tutorial paper overviews recent developments in optimization-based approaches for resource allocation problems in wireless systems. We begin by overviewing important results in the area of opportunistic (channel-aware) scheduling for cellular (single-hop) networks, where easily implementable myopic policies are shown to optimize system performance. We then describe key lessons learned and the main obstacles in extending the work to general resource allocation problems for multihop wireless networks. Towards this end, we show that a clean-slate optimization-based approach to the multihop resource allocation problem naturally results in a “loosely coupled” cross-layer solution. That is, the algorithms obtained map to different layers [transport, network, and medium access control/physical (MAC/PHY)] of the protocol stack, and are coupled through a limited amount of information being passed back and forth. It turns out that the optimal scheduling component at the MAC layer is very complex, and thus needs simpler (potentially imperfect) distributed solutions. We demonstrate how to use imperfect scheduling in the cross-layer framework and describe recently developed distributed algorithms along these lines. We conclude by describing a set of open research problems.     

A signaling protocol for complex multimedia services

The author introduces a signaling protocol for user applications that invokes multimedia services provided by the EXPANSE research prototype, a broadband ISDN testbed. A generic framework that flexibly accommodates a wide variety of services involving multiple parties with heterogeneous terminals is described. The author describes the generic services supported, introduces the EXPANSE call model, discusses syntax and message flow procedures, and relates EXPANSE signaling to the ISDN signaling control part (ISCP) and long-term broadband ISDN signaling work currently under study by CCITT     

ATM-based transport architecture for multiservices wirelesspersonal communication networks

This paper presents an ATM-based transport architecture for next-generation multiservices personal communication networks (PCN). Such “multimedia capable” integrated services wireless networks are motivated by an anticipated demand for wireless extensions to future broadband networks. An ATM compatible wireless network concept capable of supporting a mix of broadband ISDN services including constant bit-rate (CBR), variable bit-rate (VBR), and packet data transport is explored from an architectural viewpoint. The proposed system uses a hierarchical ATM switching network for interconnection of PCN microcells, each of which is serviced by high-speed, shared-access radio links based on ATM-compatible cell, relay principles. Design issues related to the physical (modulation), media access control (MAC), and data-link layers of the ATM-based radio link are discussed, and preliminary technical approaches are identified in each case. An example multiservice dynamic reservation (MDR) TDMA media access protocol is then considered in further detail, and simulation results are presented for an example voice/data scenario with a proportion of time-critical (i.e., multimedia) packet data. Time-of-expiry (TOE) based queue service disciplines are also investigated as a mechanism for improving the quality-of-service (QoS) in this scenario     

Dynamic multiuser resource allocation and adaptation for wireless systems

Driven by the increasing popularity of wireless broadband services, future wireless systems will witness a rapid growth of high-data-rate applications with very diverse quality of service requirements. To support such applications under limited radio resources and harsh wireless channel conditions, dynamic resource allocation, which achieves both higher system spectral efficiency and better QoS, has been identified as one of the most promising techniques. In particular, jointly optimizing resource allocation across adjacent and even nonadjacent layers of the protocol stack leads to dramatic improvement in overall system performance. In this article we provide an overview of recent research on dynamic resource allocation, especially for MIMO and OFDM systems. Recent work and open issues on cross-layer resource allocation and adaptation are also discussed. Through this article, we wish to show that dynamic resource allocation will become a key feature in future wireless communications systems as the subscriber population and service demands continue to expand.     

World-wide standardization of broadband ISDN

A growing market demand for high-performance voice, data, image and video networks, coupled with advances in high-speed technologies has heightened interest in broadband ISDN (BISDN) throughout the world. Network providers, equipment manufacturers and standards bodies are working jointly to accelerate the definition of BISDN interfaces in anticipation of emerging market opportunities. BISDN is being designed as the foundation upon which to implement very flexible, high-bandwidth, high-performance networks. A multiplexing concept called asynchronous transfer mode (ATM), which can offer bandwidth on demand at rates exceeding 150 Mb/s, high-speed packet switching, and an efficient protocol which adapts existing information streams into the ATM format are key attributes of the emerging BISDN network standards. This paper reviews the motivations behind BISDN, explains its key attributes and challenges and discusses possible strategies for evolving today's network toward BISDN.