在基于正交频分多址技术的宽带网络中，通过把竞争分散到多个子信道能有效改善随机接入的性能。然而多信道特性也会使传统基于Request-To-Send （RTS ）控制帧的随机接入协议面临子信道空闲、RTS传输时间延长、上行复杂的问题。针对这些问题，在本文所提出的接入方法中，用户在没有被分配到资源时通过在随机子载波上发送信号来请求传输机会，与此同时，接入点对这些信号侦听，并根据子载波忙闲状态确定哪些用户可以接入。理论分析及仿真结果表明，相比传统依靠RTS的接入方法，采用子载波侦听，系统将获得更高的吞吐量。

In the orthogonal frequency division multiple access (OFDMA)wireless broadband networks ,the efficiency of ran-dom access can be improved by distributing contention onto multiple channels .However ,due to the multichannel property ,the tradi-tional systems based on request-to-send (RTS )control frame have to encounter the idleness of subchannel ,the extension of RTS transmission time and the complex synchronization of uplink communication .To solve these problems ,in our scheme ,the users send signals on random subcarrier to request transmission opportunity .The access point senses these request signals ,and determines which user is permitted to access channel according to the busy state of the subcarriers .The theoretical analysis and simulation results both show that our scheme outperforms the traditional RTS-based schemes in term of the throughput .

如何保障不同类型的多媒体业务在通信过程中的通信服务质量(QoS),是目前接入控制技术中一项热点研究问题。通过对近十几年间相关文献的整理和分析,对支持多媒体业务的接入控制技术的研究进展进行综述,具体内容包括多媒体业务类型的设计、支持多媒体业务的接入控制协议、多信道分配策略等方面,并提出了支持多媒体业务的接入控制技术未来的研究方向。

One of the hot research spots in access control technology is how to guarantee Quality of Service(QoS) of multimedia services in the communication process. Research progresses made in access control technology for multimedia services during the past decades are reviewed based on extensive investigations, including design of multimedia services, access control technologies, and multi-channel allocation policies, et al. Interesting and promising research issues in access control technology for multimedia services are also predicted.

针对分布式无线协作网络中多中继接入信道的复杂频谱管理问题,提出了一种基于DTR协议的改进算法.该算法采取局部博弈的方式选择单个接入信道的中继节点,避免了DTR协议中随机接入带来的大量退避或碰撞时延消耗;同时,采用门限策略灵活控制接入信道的标准和中继与源节点局部交互信息的方式,取代了基站或AP选择最优中继的集中式控制,使算法适用于分布式网络,所需通信开销也远小于退避或碰撞传输所付出的代价.分析与仿真结果表明,在未明显增加网络开销的情况下,新算法在减少端到端平均传输时延和改善系统吞吐量方面比传统DTR算法具有更优异的性能.

In order to implement the complex spectrum management in multi-relay channel accesses for distributed wireless cooperative networks,an improved algorithm based on the DTR protocol is proposed,which selects the best relay node offering cooperation based on the local game,thus avoiding the large delay due to the backoff or collision caused by the random access in the DTR protocol.Moreover,in this algorithm,each source controls its standard of accessing channel with threshold scheme adaptively,and the information between relay and source nodes is locally exchanged,thus substituting the centralized control mode for the best relay selection of base station or AP and exten-ding the algorithm to distributed systems.As compared with the backoff and collision transmission in DTR protocol, the proposed algorithm results in less communication overhead.Analytical and simulated results show that the pro-posed algorithm is superior to the traditional DTR-based algorithm because it helps to reduce th

IEEE802．1ie媒体接入控制（MAC）协议不能较好地满足无线多媒体传感器网络不同类型业务节点间的公平性要求。为解决该问题，提出一种基于博弈论的无线多媒体传感器网络MAC协议。将节点间的信道竞争过程建模为非完全信息动态博弈，在不同的负载情况下，通过改变普通业务的权重提高不同业务间的公平性。仿真结果表明，该协议能在保证多媒体业务服务质量的同时，增加普通业务数据流接入信道的机率，提高整个网络的平均吞吐量。

In wireless multimedia sensor networks, IEEE802.11e Medium Access Control(MAC) protocol can not solve the fair access to channel between different services of each node. To solve this problem, this paper proposes MAC protocol for multimedia sensor network based on game theory. The main idea is that the channel contention process is modeled a dynamic game with incompletely information. Under different load conditons, the protocol improves the weight of the ordinary services and reduces the fairness between the different services. Simulation results show that this protocol can guarantee the Quality of Service(QoS) of multimedia services, make ordinary service, get more chance to access channel, and improve the average throughput of the networks.

针对当前单兵作战系统通信网络中所采用的固定分配TDMA算法不能适应大型战场环境和自组织运行需求的问题,提出一种基于消费算法和二叉树时隙分配算法的动态时隙分配TDMA算法,即C-TDMA算法,通过多组载波监听消除接入冲突,在保证延时的基础上使用消费算法控制节点分组发送量,提高信道接入公平性,同时通过二叉树时隙分配算法支持网络分布式运行。仿真结果表明,对于负载较重、传输混合业务且时延敏感的单兵作战系统网络,该算法可以消除接入冲突,提高信道吞吐率。

The static slot allocation TDMA channel access algorithms used in Integrated Individual Soldier Combat System ( IISCS ) are not adaptable to the demand of large battlefield network and autonomous operation.To solve the problem,we proposed a dynamic slot allocation TDMA access algorithm of MAC protocol,named C-TDMA,based on consumption algorithm and binary tree slot allocation algorithm .The access conflicts are eliminated in the control slot by multiple RTS/CTS.The consumption arithmetic is used to control the data flow and improve fairness access of different services on the basis of delay quality,and the binary tree slot allocation algorithm is used for distributed network environment .The simulation results indicate that real-time services can be supported by C-TDMA protocol in heavy-load and mixed-service in IISCS,which presents good performance on access efficiency .