认知无线电网络MAC层协议研究

认知网络按照一定的准则划分为若干个簇,簇内共享一条信道用于交换控制信息,这种以分簇的方式实现按区域共享信道是认知无线电MAC层频谱共享问题的解决方法之一.为了使分簇结构更加有效的工作,本文提出了一种针对分簇结构的MAC层协议.在该协议中,信道接入时间被划分成一系列的超级帧,超级帧的各个时段均对应簇节点的具体操作,以此支撑簇结构稳健地应对主用户行为.仿真结果表明,本文提出的MAC协议在中高网络负载情况下能获得较高的网络吞吐量以及较低的传输时延.     

基于智能天线并具有QoS保障的Ad hoc网络MAC协议*

基于智能天线技术的发展,提出一种基于智能天线并具有QoS保障的MAC协议。该协议首先把信道划分为数据信道与控制信道,节点通过业务的优先级与时延来发送预报突发竞争信以保证QoS质量,随后按照RTS/CTS握手机制预约节点进行数据传输,又采用发送Busy Tones来防止聋节点和隐藏终端的问题,大大提高了网络容量与性能。通过分析与仿真,并且与IEEE 802.11协议以及DMAC协议比较,证明QTDMAC协议在吞吐量以及实时业务时延上都有很大的优越性。     

认知无线电网络分布式多信道MAC协议*

在认知无线电网络中,MAC协议用于信道感知、选择和接入控制。以单网卡多信道MAC（MMAC）协议为基础,依据IEEE 802.22标准定义的静默期管理的两阶段感知策略,提出一种认知无线电网络分布式多信道MAC（CR-MMAC）协议。将两阶段感知机制和分布式协商融入MMAC协议,利用空闲频谱进行数据传输,并在MMAC协议ATIM窗的数据信道协商阶段引入预约机制,以避免选择同一信道的认知节点对在后续数据传输阶段再利用CSMA/CA造成的竞争碰撞。仿真对比分析表明,CR-MMAC协议能提高网络吞吐量、降低通信时     

基于接收端信号的水声网络MAC协议

水声网络的信道具有数据速率低以及传播时延长的特点,如果采用握手机制减少数据冲突,将降低信道利用率和网络的吞吐量。提出了一种基于接收节点发送短信号告知邻居节点其接收状态的水声网络MAC协议,即当接收节点接收数据时,向邻居节点发送短信号通知其当前时刻不要发送数据,解决了隐藏终端和暴露终端的问题,并提高了网络吞吐量;除此之外,使用短信号还能够降低能量损耗。仿真结果表明该协议能够实现上述目的。     

一种基于认知无线电的自组网多信道MAC协议

针对节点具有多个可用信道的自组网的信道资源利用率问题,提出了一种基于认知无线电的MAC接入协议,协议根据网络中节点的邻居关系,通过认知推理对两跳邻居范围内的不同网络节点分配不同的驻留信道,驻留信道的选择考虑了避免信道干扰和冲突,每个节点只需要两部半双工收发信机就能够实现在多个信道上高效的数据收发.仿真结果表明,协议在网络总吞吐量、端到端时延等方面具有优良的性能,能很好地适用于节点密集的应用场合.     

一种基于认知无线电的自组网多信道MAC协议

针对节点具有多个可用信道的自组网的信道资源利用率问题,提出了一种基于认知无线电的MAC接入协议.协议根据网络中节点的邻居关系,通过认知推理对两跳邻居范围内的不同网络节点分配不同的驻留信道.驻留信道的选择考虑了避免信道干扰和冲突,每个节点只需要两部半双工收发信机就能够实现在多个信道上高效的数据收发,同时只需很少的控制信息开销.仿真结果表明,协议在网络总吞吐量、端到端时延等方面具有优良的性能,能很好地适用于节点密集的应用场合.     

全双工CSMA网络中的隐藏终端问题研究

同时同频全双工技术允许节点在同一频带内同时发送和接收信号,理论上可以将频带利用率提高一倍。该技术虽然可以有效缓解传统CSMA网络中的隐藏终端问题,但是全双工CSMA网络中的隐藏终端问题仍然缺少全面且深入的研究。对半双工CSMA网络中隐藏终端问题及其解决方案进行了分析,介绍了全双工CSMA网络中的4种传输模式,理论分析和实验仿真说明了全双工CSMA网络中的隐藏终端问题。最后进一步分析了一些现有的全双工媒体访问控制(Medium Access Control,MAC)协议,并提出了几个在设计全双工MAC协议时为解决隐藏终端问题而应该考虑的问题。     

基于双忙音的可调功率无线MAC协议

本文基于IEEE802.11DCF提出了两种基于双忙音信号的无线自组织网络MAC协议,即恒定功率双忙音(FPDBT)和变功率双忙音(VPDBT)MAC协议。这两种协议能基本解决无线自组织网络大干扰范围下的隐藏终端和暴露终端问题。本文对MAC协议进行了理论分析,并建立了OPNET仿真模型。通过仿真试验分析比较了IEEE802.11DCF、DBTMA、FPDBT和VPDBTMAC协议的信道传输性能。结果表明两种改进协议都能在大干扰范围下有效避免分组冲突,并显著提高信道利用率。VPDBT协议还能够对信道空间复用率和分组冲突避免的性能有较好的折衷。     

基于预约调度的无线传感器网络的MAC协议

提出了一种基于预约调度的用于无线传感器网络的MAC协议--SSMAC.该协议采用分布式竞争接入和预约调度发送,提供高能量效率的信道接入和支持QoS业务的传输,较好地解决了隐藏终端和暴露终端问题.仿真结果表明SSMAC协议在保持节能的同时,在降低媒体接入时延、提高报文投递成功率和提供QoS保障上较TRAMA协议性能有很大的提高.     

一种应用于分布式网络的新型私有多信道UWB MAC协议设计

目前,单信道MAC协议在网络负载较重时的冲突和退避,造成信道带宽浪费而使得协议效率不高.本文主要针对UWB应用在无线个域网络中的特定场景,提出了一种新的应用于分布式网络的私有多信道UWB MAC协议,既可以解决隐藏终端和暴露终端问题,又可以有效地分配信道资源,提高网络性能.     

Ad Hoc网基于负载感知的多信道MAC协议研究

对现有的多信道MAC协议进行了分类,并特别分析了基于负载感知的多信道MAC协议（LAMM）。LAMM协议能够根据网络流量动态地调整信道的分配,在网络时延和吞吐量上都有显著改善。但LAMM协议对多信道中存在的丢失接受者问题（missing Peceiver problem）无法很好地解决。针对这一问题提出了解决机制,很好地完善了LAMM协议。其中“成功退避”机制概念的提出,用来减轻由于丢失接受者问题产生的不公平现象。     

认知无线电网络双天线多信道MAC协议

在认知无线电网络中,媒体接入控制(MAC)协议的主要功能包括信道感知、选择和接入控制,其中感知时间和传输时间的长度对网络的性能有着重要的影响。在动态无线网络环境下,如何合理分配感知时间和传输时间是个挑战性问题。提出了一种双天线多信道分布式认知无线电MAC（TM-MAC）协议,不需要在传输之前对信道进行感知。节点可以在其它节点传输数据的同时对频谱资源进行检测,然后利用空闲的频谱资源通信。建立了数学模型分析在饱和网络状况下MAC协议的吞吐量。仿真分析表明TM-MAC协议能够有效提高网络的吞吐量。     

On game theoretic DSA-driven MAC for cognitive radio networks

The game theoretic dynamic spectrum allocation (DSA) technique is an efficient approach to coordinate cognitive radios sharing the spectrum. However, existing game based DSA algorithms lack a platform to support the game process. On the other hand, existing medium access control (MAC) protocols for cognitive radio networks do not fully utilize the adaptability and intelligence of the cognitive radio (CR) to achieve efficient spectrum utilization, let alone fairness and QoS support. Therefore it is necessary to develop DSA-driven MAC protocols with the game theoretic DSA embedded into the MAC layer. In this paper, based on the analysis of challenges for the game theoretic DSA in realistic applications, we conclude that a unified game theoretic DSA-driven MAC framework should constitute of four integral components: (1) DSA algorithm, deriving the spectrum access strategy for data communication; (2) negotiation mechanism, coordinating players to follow the right game policy; (3) clustering algorithm, limiting the negotiation within one cluster for scalability; (4) collision avoidance mechanism, eliminating collisions among clusters. With our MAC framework, DSA-driven MAC protocols can be conveniently developed, as illustrated in the design process of a concrete QoSe-DSA-driven MAC protocol. The game theoretic DSA-driven MAC framework can fulfill merits of game theoretic DSA algorithms including high spectrum utilization, collision-free channel access for data communication, QoS and fairness support. Through simulations, the merits of the DSA-driven MAC framework are demonstrated.     

基于节点合作的Ad hoc网多信道MAC协议

针对Ad hoc网络的多信道隐藏终端问题,提出一种基于邻居节点合作通告机制的异步多信道媒介访问控制协议。该协议通过空闲邻居节点向未收到信道协商控制帧的节点发送通告广播帧,从而有效地解决了多信道隐藏终端问题。仿真结果表明,与IEEE 802.11、MMAC协议相比,该协议在提高网络平均吞吐量的同时,还能降低数据包平均延迟。     

Double sense multiple access for wireless ad hoc networks

In wireless ad hoc networks, the major quality of service (QoS) concern and challenge in the design and analysis of contention-based medium access control (MAC) protocols is to achieve good throughput and access delay performance in the presence of hidden terminals, which are defined as the terminals out of the radio coverage area of an intended transmitter but within that of the receiver. We propose and analyze in this paper a new dual-channel random access protocol, called “Double Sense Multiple Access” (DSMA), for improving QoS support in wireless ad hoc networks. By separating the transmissions of ready-to-send (RTS) and data packets into two time-slotted channels and by introducing a novel double sense mechanism, DSMA completely solves the hidden terminal problem and can guarantee the success transmission of data packets. By taking into account the most complex network scenario in which all transmitters are hidden terminals with respect to each other, key QoS metrics such as throughput, blocking probability and access delay are derived mathematically for the proposed DSMA protocol. These analytical results are verified by extensive computer simulations.     

基于FPRP的无线自组织网的MAC协议*

基于FPRP的用于同步无线自组织网的MAC协议采用分布式控制和同步竞争接入,能够支持QoS业务的传输,较好地解决了隐藏终端和暴露终端问题.仿真结果表明,该协议在吞吐率和媒体接入时延上较同步FPRP有所提高.     

Dynamic duty cycle and adaptive contention window based QoS-MAC protocol for wireless multimedia sensor networks

Rapid penetration of small, customized wireless devices and enormous growth of wireless communication technologies has already set the stage for large-scale deployment of wireless sensor networks. While the need to minimize the energy consumption has driven significant researches in wireless sensor networks, offering some precise quality of service (QoS) for multimedia transmission over sensor networks has not received significant attention. However, the emerging new applications like video surveillance, telemedicine and traffic monitoring needs transmission of wireless multimedia over sensor networks. Naturally, offering some better QoS for wireless multimedia over sensor networks raises significant challenges. The network needs to cope up with battery-constraints, while providing improved QoS (end-to-end delay and bandwidth requirement). This calls for a suitable sensory MAC protocol capable of achieving application-specific QoS. In this paper, we have proposed a new QoS-based sensory MAC protocol, which not only adapts to application-oriented QoS, but also attempts to conserve energy without violating QoS-constraints. Performance modeling, analysis and simulation results demonstrate that the proposed protocol is capable of providing lower delay and better throughput, at the cost of reasonable energy consumption, in comparison to other existing sensory MAC protocols.