宽带无线局域网MAC协议研究
发布时间：2018-10-23 11:39
【摘要】：随着无线局域网络(WLAN)应用的不断推广,WLAN在物理层技术及频谱利用方面也得到了快速的发展。WLAN的媒质访问控制(MAC)协议决定了网络系统中各节点共享接入信道的具体实现方式,并从根本上决定着WLAN的性能。现有IEEE 802.11系列的MAC主要采用了基于CSMA/CA协议的分布式协调功能(DCF)以实现媒体的共享接入。然而,伴随OFDM调制技术在物理层的应用而带来的物理层速率的增加,CSMA/CA的吞吐量性能却随之下降。另外,在长时延及相干时间较大的无线信道环境下,CSMA/CA已经不再适应用,此时,时隙ALOHA协议成为一种新的选择。时隙ALOHA及其改进协议由于简单而在认知无线网络、射频识别(FRID)的标签识别、卫星通信及新的无线网络技术研究等方面得到了广泛应用。为提高信道利用率,保证时隙ALOHA的稳定性及获得最大系统吞吐量方面展开了大量相关研究。本文针对传统MAC随机信道接入机制CSMA/CA在宽带WLAN环境下存在的问题,考虑以时隙ALOHA作为这类应用的信道接入控制协议,并对时隙ALOHA协议的性能及稳定性控制开展了一些具有创新意义的工作。本文的创新点如下:1.与现有文献主要考虑采用帧汇聚方式来达到提高宽带WLAN环境下DCF吞吐量性能不同,提出采用基于时隙的信道控制协议作为宽带WLAN环境下的MAC协议。针对高速物理信道环境下,每个OFDM符号能携带更多的数据信息,以Bianchi的二维维Markov模型为基础,研究了OFDM携带比特数、OFDM符号持续时间及数据分组长度对信道利用率的影响。数值分析及仿真结果表明,当物理层速率超过100Mbps,数据分组长度小于1000字节时,无论采用RTS/CTS模式还是Basic模式,也无论系统的节点数如何,信道的有效吞吐量均小于0.35,低于时隙ALOHA协议的吞吐量。当物理层速率到达600Mbps时,每个OFDM符号携带信息达到2400bit,基于RTS/CTS模式的CSMA/CA协议的信道吞吐量率小于0.16,而Basic模式的信道吞吐量也不足25%。考虑采用时分多址作为宽带无线局域网络的MAC层协议,提出了集中调度与完全自由竞争两种应用场景下MAC设计方案。2.提出了长时延宽带WLAN的MAC设计方案。现有WLAN主要应用于终端节点近距离范围内无线接入网络的场景,而本文研究了长距离范围内WLAN的应用问题,在此场景下无线信号传输时延增大。针对长时延无线信道网络应用环境,受信道特性的影响OFDM符号时间较大,CSMA/CA性能较低,确定采用OFDM符号为单位的时隙ALOHA作为信道控制协议。提出在集中式网络环境中采用竞争加预约的时隙ALOHA协议;而分布式无线网络环境下采用时隙ALOHA的信道控制算法。并进一步分析了时隙ALOHA的稳定性。3.提出了p坚持控制算法(pPCA),并将二进制指数回退算法(BEBA)应用到时隙ALOHA系统中。现有时隙ALOHA控制算法的研究均基于节点传输后能够立即获得信道状态信息的假设条件,但实现上这种假设往往是不成立的。本文首先分析了基于传统假设的伪贝叶斯控制(PBCA)经典控制算法的性能。其次,针对节点只能检测到信道空闲状态的应用环境,提出了以时间帧为更新单位的p坚持控制算法。系统通过统计某时间窗口内空闲时隙的概率,估计出系统节点数n,然后调整节点的发送概率为1/n,以获得系统最大稳定吞吐量。并考虑到二进制指数回退算法在CSMA/CA中的应用,提出将该算法应用到时隙ALOHA中,通过二维Markov模型获得系统稳定吞吐量的数学表达式。仿真结果表明,三种控制算法均能获得接近理论最大值的系统稳定吞吐量。最后对三种控制算法在调整过程中的吞吐量,达到稳定最大吞吐量的时间及算法复杂度三个方面进行了比较。仿真结果显示,当节点数较小,PBCA在平均吞吐量和调节时间上都优于BEB算法和pPCA算法;当节点数较大时,三种算法的平均吞吐量基本一致,但pPCA调节时间较长;在算法复杂度方面,PBCA最优。4.提出了快速自适应(FA)时隙ALOHA稳定控制算法。针对伪贝叶斯控制算法及p坚持控制算法中,当节点数目突然发生急骤变化时,稳定调节时间较长的问题,提出依据信道状态的游程长度先进行快速调整,将系统实际节点数与估计节点数之比调整到0.5~2的范围内,然后再采用pPCA或PBCA进行调整。仿真结果表明,自适应控制算法能很好的适应节点急骤变化的应用场景。
[Abstract]:With the continuous popularization of wireless local area network (WLAN) applications, WLAN has developed rapidly in physical layer technology and spectrum utilization. The medium access control (MAC) protocol of WLAN determines the specific implementation mode of the shared access channel of each node in the network system, and decides the performance of WLAN fundamentally. The MAC of IEEE 802. 11 series mainly adopts the distributed coordination function (DCF) based on CSMA/ CA protocol to realize the shared access of the media. However, the throughput performance of CSMA/ CA decreases with the increase of the physical layer rate resulting from the application of the OFDM modulation technique in the physical layer. In addition, CSMA/ CA is no longer suitable for long time delay and large coherence time, at which time slot ALOHA protocol becomes a new choice. The time slot ALOHA and its improved protocols have been widely used in cognitive radio network, radio frequency identification (FRID) tag identification, satellite communication and new wireless network technology research. In order to improve the channel utilization rate, the stability of slotted ALOHA and the maximum system throughput have been studied. Aiming at the existing problems of CSMA/ CA in the broadband WLAN environment, this paper considers the channel access control protocol which takes the time slot ALOHA as the class application, and carries out some innovative work on the performance and stability control of the slotted ALOHA protocol. The innovation points in this paper are as follows: 1. Compared with the existing literatures, we mainly consider adopting the frame convergence method to improve the DCF throughput performance in the broadband WLAN environment, and propose a channel control protocol based on time slot as the MAC protocol in the broadband WLAN environment. For high-speed physical channel environment, each OFDM symbol can carry more data information, based on Bianchi's two-dimensional Markov model, the effect of OFDM carrying bit number, OFDM symbol duration and data packet length on channel utilization rate is studied. Numerical analysis and simulation results show that when the physical layer rate exceeds 100Mbps, the data packet length is less than 1000 bytes, whether the RTS/ CTS mode or the basic mode is adopted, regardless of the number of nodes in the system, the effective throughput of the channel is less than 0. 35, which is lower than the throughput of the time slot ALOHA protocol. When the physical layer rate reaches 600Mbps, each OFDM symbol carries information up to 2400bit, the channel throughput rate of CSMA/ CA protocol based on RTS/ CTS mode is less than 0.016, and the channel throughput of Basic mode is less than 25%. Considering the adoption of time division multiple access (TDMA) as the MAC layer protocol of the broadband wireless local area network, the MAC design scheme in two application scenarios of centralized scheduling and full free competition is proposed. The MAC design scheme of long-delay broadband WLAN is proposed. The existing WLAN mainly applies to the scene of the wireless access network in the short range of the terminal node, and the application problem of WLAN in long-distance range is studied, and the transmission time delay of the wireless signal is increased in this scenario. Aiming at the long-delay wireless channel network application environment, the OFDM symbol time is greatly influenced by the channel characteristics, the CSMA/ CA performance is low, and the time slot ALOHA with the OFDM symbol as the unit is determined as the channel control protocol. This paper proposes a time slot ALOHA protocol which uses contention plus reservation in a centralized network environment, and a channel control algorithm with time slot ALOHA is adopted in the distributed wireless network environment. The stability of time slot ALOHA was further analyzed. The p persistence control algorithm (pPCA) is proposed and the binary exponential backoff algorithm (BEBA) is applied to the slotted ALOHA system. The existing time slot ALOHA control algorithm is based on the assumption that the channel state information can be obtained immediately after the node transmission, but this assumption is often not established. In this paper, we first analyze the performance of pseudo-Bayesian control (PBCA) classical control algorithm based on traditional hypothesis. Secondly, aiming at the application environment that the node can only detect the idle state of the channel, the p persistence control algorithm based on the time frame as the update unit is proposed. The system estimates the system node number n by counting the probability of the idle time slot in a certain time window, and then adjusts the transmission probability of the node to 1/ n to obtain the maximum stable throughput of the system. Taking into account the application of binary exponential backoff algorithm in CSMA/ CA, this paper proposes the application of the algorithm into the slot ALOHA, and obtains the mathematical expression of the system's stable throughput through the two-dimensional Markov model. The simulation results show that the three control algorithms can obtain the system stable throughput close to the theoretical maximum. Finally, the throughput of three control algorithms is compared in three aspects: the throughput of the three control algorithms during the adjustment process, the time to reach the stable maximum throughput and the complexity of the algorithm. Simulation results show that when the number of nodes is small, PBCA is better than BEB algorithm and pPCA algorithm on average throughput and adjustment time; when the number of nodes is large, the average throughput of the three algorithms is basically the same, but the pPCA adjustment time is longer; in terms of algorithm complexity, PBCA is the best. A fast adaptive (FA) slot ALOHA stabilization control algorithm is presented. aiming at the pseudo-Bayesian control algorithm and the p-persistence control algorithm, when the number of nodes suddenly changes abruptly, the problem of longer stable adjustment time is solved, and the run length according to the channel state is firstly adjusted quickly, the ratio of the actual number of nodes of the system to the number of estimated nodes is adjusted to a range of 0.5 to 2, and then the pPCA or PBCA is used for adjustment. The simulation results show that the adaptive control algorithm can adapt to the application scenarios of sudden change of nodes.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN925.93
，
本文编号：2289122
[Abstract]:With the continuous popularization of wireless local area network (WLAN) applications, WLAN has developed rapidly in physical layer technology and spectrum utilization. The medium access control (MAC) protocol of WLAN determines the specific implementation mode of the shared access channel of each node in the network system, and decides the performance of WLAN fundamentally. The MAC of IEEE 802. 11 series mainly adopts the distributed coordination function (DCF) based on CSMA/ CA protocol to realize the shared access of the media. However, the throughput performance of CSMA/ CA decreases with the increase of the physical layer rate resulting from the application of the OFDM modulation technique in the physical layer. In addition, CSMA/ CA is no longer suitable for long time delay and large coherence time, at which time slot ALOHA protocol becomes a new choice. The time slot ALOHA and its improved protocols have been widely used in cognitive radio network, radio frequency identification (FRID) tag identification, satellite communication and new wireless network technology research. In order to improve the channel utilization rate, the stability of slotted ALOHA and the maximum system throughput have been studied. Aiming at the existing problems of CSMA/ CA in the broadband WLAN environment, this paper considers the channel access control protocol which takes the time slot ALOHA as the class application, and carries out some innovative work on the performance and stability control of the slotted ALOHA protocol. The innovation points in this paper are as follows: 1. Compared with the existing literatures, we mainly consider adopting the frame convergence method to improve the DCF throughput performance in the broadband WLAN environment, and propose a channel control protocol based on time slot as the MAC protocol in the broadband WLAN environment. For high-speed physical channel environment, each OFDM symbol can carry more data information, based on Bianchi's two-dimensional Markov model, the effect of OFDM carrying bit number, OFDM symbol duration and data packet length on channel utilization rate is studied. Numerical analysis and simulation results show that when the physical layer rate exceeds 100Mbps, the data packet length is less than 1000 bytes, whether the RTS/ CTS mode or the basic mode is adopted, regardless of the number of nodes in the system, the effective throughput of the channel is less than 0. 35, which is lower than the throughput of the time slot ALOHA protocol. When the physical layer rate reaches 600Mbps, each OFDM symbol carries information up to 2400bit, the channel throughput rate of CSMA/ CA protocol based on RTS/ CTS mode is less than 0.016, and the channel throughput of Basic mode is less than 25%. Considering the adoption of time division multiple access (TDMA) as the MAC layer protocol of the broadband wireless local area network, the MAC design scheme in two application scenarios of centralized scheduling and full free competition is proposed. The MAC design scheme of long-delay broadband WLAN is proposed. The existing WLAN mainly applies to the scene of the wireless access network in the short range of the terminal node, and the application problem of WLAN in long-distance range is studied, and the transmission time delay of the wireless signal is increased in this scenario. Aiming at the long-delay wireless channel network application environment, the OFDM symbol time is greatly influenced by the channel characteristics, the CSMA/ CA performance is low, and the time slot ALOHA with the OFDM symbol as the unit is determined as the channel control protocol. This paper proposes a time slot ALOHA protocol which uses contention plus reservation in a centralized network environment, and a channel control algorithm with time slot ALOHA is adopted in the distributed wireless network environment. The stability of time slot ALOHA was further analyzed. The p persistence control algorithm (pPCA) is proposed and the binary exponential backoff algorithm (BEBA) is applied to the slotted ALOHA system. The existing time slot ALOHA control algorithm is based on the assumption that the channel state information can be obtained immediately after the node transmission, but this assumption is often not established. In this paper, we first analyze the performance of pseudo-Bayesian control (PBCA) classical control algorithm based on traditional hypothesis. Secondly, aiming at the application environment that the node can only detect the idle state of the channel, the p persistence control algorithm based on the time frame as the update unit is proposed. The system estimates the system node number n by counting the probability of the idle time slot in a certain time window, and then adjusts the transmission probability of the node to 1/ n to obtain the maximum stable throughput of the system. Taking into account the application of binary exponential backoff algorithm in CSMA/ CA, this paper proposes the application of the algorithm into the slot ALOHA, and obtains the mathematical expression of the system's stable throughput through the two-dimensional Markov model. The simulation results show that the three control algorithms can obtain the system stable throughput close to the theoretical maximum. Finally, the throughput of three control algorithms is compared in three aspects: the throughput of the three control algorithms during the adjustment process, the time to reach the stable maximum throughput and the complexity of the algorithm. Simulation results show that when the number of nodes is small, PBCA is better than BEB algorithm and pPCA algorithm on average throughput and adjustment time; when the number of nodes is large, the average throughput of the three algorithms is basically the same, but the pPCA adjustment time is longer; in terms of algorithm complexity, PBCA is the best. A fast adaptive (FA) slot ALOHA stabilization control algorithm is presented. aiming at the pseudo-Bayesian control algorithm and the p-persistence control algorithm, when the number of nodes suddenly changes abruptly, the problem of longer stable adjustment time is solved, and the run length according to the channel state is firstly adjusted quickly, the ratio of the actual number of nodes of the system to the number of estimated nodes is adjusted to a range of 0.5 to 2, and then the pPCA or PBCA is used for adjustment. The simulation results show that the adaptive control algorithm can adapt to the application scenarios of sudden change of nodes.
【学位授予单位】：电子科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TN925.93
，
本文编号：2289122
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