自适应CSI反馈的下行MU-MIMO MAC协议研究

发布时间：2018-08-19 10:38

【摘要】：近几年随着基于无线的网络服务爆炸性的增长,无线局域网中对于高速数据传输的需求变得越来越迫切。同时,无线局域网中的用户规模也相较以前有了很大增长。为了提高无线网络的性能,提高吞吐量,降低时延,提高网络资源利用率,多用户MIMO技术得到了越来越多研究者的关注。并且值得注意的是,随着无线网络逐渐渗透到人们生活的各个领域,各种新型业务层出不穷,无线网络是否可以承载足够多的业务类型也是需要考量的方面。在上述场景中,高QoS保证和更加高效的MAC协议成为提高网络性能的重要保证。针对业务类型不断增长的无线局域网,本文提出了一种多用户MIMO场景下的带有自适应CSI反馈的下行MAC协议。所提协议通过更改帧格式的方式改进传统CSMA/CA退避机制,使得协议可以更加充分的利用物理层的多天线资源,实现多包的同时收发,大幅提高吞吐量和降低时延。站点间的信道状态信息(Channel State Information)通过一种动态自适应的方式得以传递。具体来说通过一项重要指标—数据包传输成功率,通过比较它与预先设定的阈值的大小,间接的评估无线信道质量,对是否进行CSI信息的更新给出参考。同时,本文还提出了一种新型的基于整数分割的MAC层数据包选择策略,该策略在保持高QoS的前提下,同时保证了公平性。我们可以通过数据量化的方式评估该策略的公平性,同时还可以根据需要人为调整各种类型业务的传输比例。接下来,在几个合理性假设的基础上,对所提出的下行多用户MIMO MAC协议的饱和吞吐量、接入时延和AC间的传输公平性进行了数学理论分析,推导得出了采用该协议时网络饱和吞吐量、接入时延以及各AC发送失败概率的表达式。同时,本文通过一个基于MATLAB的仿真平台对提出的MIMO MAC协议进行了详尽的仿真。通过对饱和吞吐量、接入时延、MAC队列实时状态和AC间公平性等指标进行多方面的考察,分析并讨论了数据包长度、信道的时变特性、网络中用户数目等参数对网络性能的影响,证明了所提下行MAC协议在上述指标上明显优于其他同类协议。
[Abstract]:In recent years, with the explosive growth of wireless based network services, the demand for high speed data transmission in WLAN becomes more and more urgent. At the same time, the size of users in WLAN has also increased greatly compared with the past. In order to improve the performance of wireless networks, improve throughput, reduce delay, and improve the utilization of network resources, multi-user MIMO technology has been paid more and more attention by researchers. And it is worth noting that with the wireless network gradually infiltrating into every field of people's life, a variety of new services emerge in endlessly. Whether wireless network can carry enough service types is also an issue to be considered. In the above scenario, high QoS guarantee and more efficient MAC protocol become the important guarantee to improve network performance. In this paper, a downlink MAC protocol with adaptive CSI feedback in multi-user MIMO scenarios is proposed for WLAN with growing service types. The proposed protocol improves the traditional CSMA/CA Backoff mechanism by changing the frame format so that the protocol can make full use of the multi-antenna resources in the physical layer to achieve multi-packet simultaneous transceiver and significantly improve the throughput and reduce the delay. The channel state information (Channel State Information) between sites is transmitted in a dynamic adaptive way. Specifically, by comparing the data packet transmission success rate with the preset threshold, the wireless channel quality is evaluated indirectly, and the reference is given to update the CSI information. At the same time, this paper proposes a new packet selection strategy based on integer partition for MAC layer, which ensures fairness while maintaining high QoS. We can evaluate the fairness of the policy by quantization of data, and we can adjust the transmission ratio of various types of services according to the need. Then, on the basis of several reasonable assumptions, the saturation throughput, access delay and transmission fairness of the proposed downlink multiuser MIMO MAC protocol are analyzed in mathematical theory. The expressions of network saturation throughput, access delay and transmission failure probability of each AC are derived. At the same time, a simulation platform based on MATLAB is used to simulate the proposed MIMO MAC protocol in detail. Based on the investigation of saturation throughput, access delay MAC queue real-time state and inter-AC fairness, the effects of packet length, channel time-varying characteristics and number of users in the network on the network performance are analyzed and discussed. It is proved that the proposed downlink MAC protocol is superior to other similar protocols in the above indexes.
【学位授予单位】：西安电子科技大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN919.3

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