Fair data scheduling in OFDM wireless networks based on maximizing utility

This paper proposes a joint layer scheme for fair downlink data scheduling in multiuser OFDM wireless networks. Based on the optimization model formulated as the maximization of total utility function with respect to the mean waiting time of user queue,we present an algorithm with low complexity for dynamic subcarrier allocation (DSA). The decision for subcarrier allocation was made according to delay utility function obtained by the algorithm that instantaneously estimated both channel condition and queue length using an exponentially weighted low-pass time window and pilot signals respectively. The complexity of algorithm was reduced by varying the length of the time window to make use of time diversity,which provided higher throughput ratio. Simulation results demonstrate that compared with the conventional approach,the proposed scheme achieves better performance and can significantly improve fairness among users,with very limited delay performance degradation by using a decreasing concave utility function when the traffic load increases.     

IEEE 802.16系统中针对AMR语音编码器的上行VoIP调度

针对IEEE 802.16系统中基于自适应多速率(AMR)语音编码器的IP语音(VoIP)业务,提出了一个新的上行调度算法。该算法在用户的语音静默期,向信道质量指示(CQI)信道发送特殊的码分多址(CDMA)码来申请带宽。然后从系统容量、吞吐量、时延和系统信令开销方面分析了所提策略的性能,并且做了仿真实验。从理论分析和仿真结果可以看出：新算法可以比传统算法增加系统容量和吞吐量,减少平均访问时延。     

一种基于多信道的接收节点优先的MAC算法

为了提高无线传感器网络的吞吐量并减小延迟,提出了一种基于多信道的接收节点优先的MAC算法（MCS-MAC）.在信道选择阶段,以接收节点为中心,由接收节点选择数据信道,发送节点转换到数据信道上与接收节点通信.如果接收节点不在控制信道上,邻居节点会主动发送NCTS包通知发送节点,并告知接收节点所在的信道,发送节点转换到数据信道进行通信,有效地利用了多信道,提高了网络吞吐量.在数据传输阶段,允许一次传送多个数据包,有效地减少了信道转换次数,减少了传输延迟.仿真结果表明,在较高负载的网络环境下,与经典S-MAC、MMAC协议相比,MCS-MAC明显提高网络吞吐量,同时减少了包的平均传输延迟.     

Cross-layer adaptive cooperative TDMA protocol for multi-hop wireless networks

Aiming at signal fading in the Rayleigh channel and channel waste or overload caused by the sudden traffic transmission in multi-hop wireless networks, a cross-layer adaptive cooperative time division multiple access protocol(CAC-TDMA) for multi-hop wireless networks is proposed. By taking advantage of the routing layer characteristics that periodically update topology, nodes can get the channel outage probability and position, determine whether they are cooperative relays themselves by no additional consultations overhead, which can decrease the waiting delay and increase channel utilization. To make a numerical analysis of the throughput, packet drop rate and delay of CAC-TDMA, a Markov chain analysis models of CAC-TDMA is constructed. Numerical and simulation results show that the proposed protocol can guarantee better performance than the conventional TDMA, that is, the maximum increase of throughput is 36％ and the maximum decrease of delay is 40％.     

Design and analysis of MAC protocol for wireless ATM network

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Cross-layer optimization and design based on QoS guarantees in the relay system

In order to improve the throughput and guarantee the quality-of-service (QoS) for a relay system, a cross-layer design scheme which combines adaptive modulation and coding (AMC) at the physical layer with cooperative hybrid automatic repeat request (CHARQ) at the link layer is proposed over the Nakagami-m fading channel. Firstly, the system packet loss rate (PLR) is described and analyzed through the state transition diagram. Then, the queuing delay is derived using the queuing theory. Moreover, a cross-layer model for maximizing system throughput is presented under the constraints of PLR, queuing delay and transmission delay. Numerical results show that the cross-layer design scheme combining CHARQ with AMC can achieve the optimal throughput, the smallest PLR and the shortest queuing delay and transmission delay.     

LTE系统中一种低丢包率的实时业务调度算法

为提高LTE系统中实时业务调度算法的系统丢包率性能,且针对时延优先调度(Delay prioritized scheduler,DPS)算法随着用户数目的增多丢包率性能急剧变差、系统吞吐量也较低等问题,本文在DPS算法基础上,提出一种综合考虑用户时延信息和实时下行信道状态信息的改进算法.通过引入信道状态信息,可以有效提高系统吞吐量;通过引入用户时延信息,可以保证用户之间的公平性.仿真结果表明,该算法在保证实时业务服务质量的前提下,取得了系统吞吐量和公平性之间的良好折中,同时可以获得更低的丢包率性能.     

Improved Delay Priority Resource Scheduling with Low Packet Loss Rate for MBMS in LTE Systems

An improved delay priority resource scheduling algorithm with low packet loss rate for multimedia broadcast multicast service (MBMS) in long term evolution (LTE) systems is proposed in this paper. Real-time services in LTE systems require lower delay and packet loss rate. However, it is difficult to meet the QoS requirements of real-time services using the current MBMS resource scheduling algorithm. The proposed algorithm in this paper jointly considers user delay information and real-time channel conditions. By introducing the user delay information, the lower delay and fairness of users are guaranteed. Meanwhile, by considering the channel conditions of users, the packet loss rate can be effectively reduced, improving the system throughput. Simulation results show that under the premise of ensuring the delay requirements of real-time services, the proposed algorithm achieves a lower packet loss rate compared to other existing algorithms. Furthermore, it can achieve a good balance between system throughput and user fairness.     

Analysis of Traffic Parameter Estimation and Its Impacts on Wireless Channel

Wide band or broadband access was paid much attention with the development of radio transmission technique. The wireless access control procedure play an important role in this type of system and efficiency of control algorithm has a great impact on throughput of channel resource. Based on wide band network control model and the characteristics of radio channel, this paper proposed a channel traffic estimation method and then performed a dynamic parameter control procedure and give detail analysis on estimation error and its impact on channel throughput and delay performance. Computation and simulation of system performance show a positive solntion on system design.     

无线Mesh网络中AMC的改进

传统的自适应调制编码（AMC）是单纯根据信道状态自适应的选择速率进行传输。为更好的提高网络性能,提出了一种联合考虑物理层的信道状态和链路层缓冲区队列长度的改进AMC,使系统能够根据实时的信道状态和缓冲区队列长度的大小,选择最合适的速率进行传输。相比较传统的AMC方法,提出的改进AMC方法能更好的提高网络性能。通过对三节点的多跳网络进行建模,在功率与带宽联合分配算法下,得到满足时延要求的最大吞吐量。仿真结果表明提出的新方法可以在满足系统时延要求的前提下,提高网络吞吐量。     

一种基于模糊逻辑的跨层功率控制机制

M-LWDF算法有效提高了系统性能,但也存在控制开销和计算量大、受信道状态信息的准确性影响等问题,同时固定的发射功率有可能造成传输容量和功率浪费。文章提出一种基于模糊逻辑的跨层功率控制机制EDF FPC,根据业务时延信息和信道状态信息,利用模糊推理方法进行自适应功率调整,避免了信道状态信息的层间回馈问题,提高了功率控制的准确性和有效性,降低了运算复杂度。仿真表明,EDF FPC能有效减少业务阻塞率,提高系统吞吐量,同时能节省功率使用。     

截短RS/混合Ⅱ型ARQ在衰落信道上的性能分析

分析了截短RS/混合Ⅱ型ARQ在无线衰落信道上的分组错误率、通过效率、传输时延等特性,给出了数值仿真结果。研究发现,由于RS码具有很强的纠错能力,通过有限次的重传就可达到很低的分组错误率,同时减小了固重传而引起的传输时延。     

适用于GEO卫星通信的单层重传机制

基于GEO卫星通信信道特性,分析现有LTE重传机制适应性改造所面临的问题,提出一种单层重传机制。该机制结合卫星链路时延大、信道质量较好的特点,去掉RLC层ARQ机制设计,并利用单层重传机制的通道数与RTD的相关性,通过扩展通道数及减少最大传输次数,提高现有重传机制对GEO卫星大时延信道特性的适应性。仿真结果表明,该重传机制能确保数据可靠性传输,缓解反馈信息带来的时延问题,提高系统吞吐量。     

基于Overlay-Underlay的功率控制路由算法

对现有混合式认知无线电网络频谱共享模型进行改进, 解决了现有路由算法在干扰与时延处理方面的缺陷, 提出了一种基于Overlay-Underlay频谱共享的路由算法. 该算法以着色图为路由分析模型, 以最短路径和链路状态作为路由指标, 以最小累积干扰为信道分配指标, 优先接入空闲授权信道, 否则利用功率冗余接入, 发展了一种具有功率控制的端到端路径选择和信道分配方法. 仿真研究结果表明了该算法的有效性, 与现有路由算法相比, 提高了网络吞吐量, 降低了丢包率和端到端时延.     

A Message Transmission Protocol of a Mobile Data Communication Network

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认知无线网络中基于业务区分的多信道MAC协议

为了满足认知无线网络中认知用户的业务服务质量需求,提出了一种基于业务区分的多信道媒体接入协议(SD-MAC).根据授权用户的信道使用模型以及认知用户的业务类型,实时业务采用基于预约的接入机制,而非实时业务则通过采用基于竞争的接入算法实现信道共享.理论分析和仿真结果表明,所提出的MAC协议能够有效提高实时业务的吞吐率,保证较低的接入时延,从而有效地提升系统性能.     

基于信道反馈的协作MAC协议

在协作媒体接入控制层协议CoopMAC基础上,提出一种改进控制帧格式的协议I oopMAC. 改进后的协议能实现与IEEE 802.11 DCF协议兼容;利用中继和信宿的联合信道状态反馈信息确定站点传输方式,较好地适应信道的瞬时变化;采用新的网络分配向量NAV更新机制,减小了分组碰撞时周围站点延迟接入信道的时间. 仿真结果表明,同样条件下,I CoopMAC协议能获得比CoopMAC协议更高的吞吐量及更小的接入时延.     

异构网中多天线用户吞吐量性能分析

针对异构网络中多种网络形式互干扰问题,提出将协作多点传输技术应用于异构网络进行干扰消除。在用户终端配置多根天线的条件下,联合考虑基站间协作传输时延和信道量化误差对干扰消除的影响,利用数学理论推导这两种非理想因素导致的系统吞吐量损失,得出吞吐量损失的理论上界。仿真结果表明采用协作多点传输技术能够减小吞吐量损失,对实际系统具有指导意义。     

Nakagami-m信道衰落下的多时隙能量收集无线通信

由于无线信道存在衰落,射频能量收集（EH）器可将收集到的电磁波能量转化为用于无线通信的电源,其功率具有动态随机特性.为此,研究了Nakagami-m信道衰落下的多时隙"收集-存储-使用"能量收集方案的有效吞吐量以及"收集-使用"能量收集方案的二进制相干和非相干解调平均误比特率性能指标,推导出了精确的理论闭合公式.仿真结果表明,在Nakagami-m信道衰落的无线通信环境下,采用"收集-存储-使用"能量收集方案的无线通信存在最佳时隙数,以实现最大有效的吞吐量,而采用"收集-使用"的能量收集方案时,无线通信会使用少量时隙来平衡误码率和通信迟延.     

基于跨层设计的多判据AODV路由优化机制

针对无线Mesh网络中传统AODV协议路由判据单一从而导致路由性能较差的缺陷,提出一种多判据AODV跨层路由优化机制ACRO(AODV Cross-layer Routing Optimization).该机制基于跨层设计思想,采用最小跳数与来自物理层和MAC层的多种路由判据相互协作,考虑了传播环境和接入性能,在路由算法中定义了混合多维路由判据, 并提出多判据AODV跨层路由优化机制.理论分析和NS2仿真结果证明,这种路由优化机制提高了吞吐量,降低了网络时延和载荷,路由性能得到明显改善.