基于IEEE802.11硬件的TDMA协议设计与实现

发布时间：2018-01-14 18:26

本文关键词：基于IEEE802.11硬件的TDMA协议设计与实现　出处：《武汉大学》2017年硕士论文　论文类型：学位论文

【摘要】：伴随着物联网、"互联网+"的蓬勃发展,一批新兴产业由此运应而生。在极大地改变了我们生活的同时,也对原有的技术提出了挑战,网络通信技术首当其冲。物联网应用场景广泛使用近距离无线通信技术,此类技术的链路层多基于IEEE802.11和IEEE802.15.4协议。Wi-Fi设备是一种典型的基于IEEE802.11协议的典型产品,具有传输速率高,相对于其它近距离无线通信技术距离远的优点,在民用领域被广泛使用。但是其链路层侦听、退避、重传机制决定了该机制的实时性无法得到保证,而实时性是物联网的一个关键性技术指标。IEEE802.15.4协议保证数据的高可靠性传输,缺点是最高传输速率仅有250kbps,在数据通信量较少的工业控制领域中应用较多。TDMA协议中,数据的发送仅受时钟控制,节点之间不会同时发送数据而相互碰撞,是解决Wi-Fi实时性不足问题的主要手段。本文选择在IEEE802.11硬件平台上设计并实现TDMA协议,以满足多种协议、设备共存的混合网络中高速率、高实时性通信的需求。另一方面,网络中大部分数据对实时性需求并不高,为同时满足实时和非实时数据的发送需求,同时充分利用硬件性能,本文设计了一种新的传输调度机制。这种调度机制能够根据当前时隙类型,选择不同的数据传输方式。本文主要工作如下:(1)研究了 IEEE802.11协议MAC层的CSMA/CA机制,分析了其造成传输时延不确定性的因素,结合TDMA协议的设计需求,在开源网卡驱动中对该问题予以修复。在此基础上,设计了 IEEE802.11硬件平台的TDMA协议,分析了其时钟同步、时隙调度、时隙大小设置等原理和方法。将修改好的协议,编译进Linux操作系统内核并移植到开发板中,在实验室环境中验证了 TDMA协议的正确性,并测试了其传输时延、可靠性等性能指标。实验结果表明,新协议在保证95%传输可靠性的同时能保证短帧中有95.4%,长帧中的89.97%能在2ms内发送完成,传输时延远低于原有的IEEE802.11 协议。(2)针对混合网络中不同类型的数据有不同的传输要求这一问题,本文在上述TDMA协议的基础上设计一种新的时隙调度机制,既能保证实时性数据的及时传输,又能兼顾采用CSMA/CA机制完成非实时数据帧的高速率传输。实验表明,该系统能及时有效地根据时隙类型完成发送机制的切换。
[Abstract]:With the rapid development of the Internet of things and the Internet of things, a number of new industries have emerged. It has greatly changed our lives, but also challenged the original technology. The network communication technology bears the brunt. The Internet of things application scene widely uses the close-range wireless communication technology. The link layer of this kind of technology is mostly based on IEEE802.11 and IEEE802.15.4 protocol. Wi-Fi device is a typical product based on IEEE802.11 protocol. With the advantages of high transmission rate and long distance compared with other short distance wireless communication technology, it is widely used in civil field, but its link layer interception, Backoff. Retransmission mechanism determines that the real-time performance of the mechanism can not be guaranteed, and real-time is a key technical index of the Internet of things. IEEE 802.15.4 protocol ensures the high reliability of data transmission. The disadvantage is that the highest transmission rate is only 250 kbps. in the field of industrial control with less data traffic, the transmission of data is only controlled by clock in the application of .TDMA protocol. Nodes do not collide with each other by sending data at the same time. This paper chooses to design and implement TDMA protocol on IEEE802.11 hardware platform to satisfy various protocols. On the other hand, most of the data in the network do not have a high demand for real-time, which is to meet the needs of both real-time and non-real-time data transmission. At the same time, taking full advantage of the hardware performance, this paper designs a new transmission scheduling mechanism, which can be based on the current slot type. The main work of this paper is as follows: 1) the CSMA/CA mechanism of MAC layer of IEEE802.11 protocol is studied. This paper analyzes the factors that cause the uncertainty of transmission delay, and according to the design requirements of TDMA protocol, fixes the problem in the open source network card driver. The TDMA protocol of IEEE802.11 hardware platform is designed, and the principles and methods of clock synchronization, slot scheduling and slot size setting are analyzed. It is compiled into the kernel of Linux operating system and transplanted to the development board. The correctness of the TDMA protocol is verified in the laboratory environment and its transmission delay is tested. The experimental results show that the new protocol can guarantee the reliability of 95% transmission at the same time that there are 95.4 in the short frame, 89.97% of the long frame can be transmitted within 2 Ms. The transmission delay is much lower than the original IEEE802.11 protocol. Based on the above TDMA protocol, this paper designs a new slot scheduling mechanism, which can ensure the timely transmission of real-time data. The high rate transmission of non-real-time data frames can be realized by using CSMA/CA mechanism. The experiments show that the system can switch the transmission mechanism according to the slot type in time and effectively.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN929.532

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