摘要
无线局域网是未来通信的重要组成部分,以IEEE802.11系列标准为代表的无线局域网作为无线接入的一种可选方式得到了广大用户和接入网运营商的青睐,且己得到了很大的发展。另一方面,对下一代无线局域网的核心技术的研究已成为无线通信技术领域的热点,并为广泛的专家、学者所关注。以空时编码为关键技术的MIMO(Multiple-Input Multiple-Output)与OFDM(Orthogonal FrequencyDivision Multiplexing)的结合被认为是下一代无线移动通信的必然选择。
本文主要是对采用OFDM技术的IEEE802.11a物理系统进行研究,并将MIMO技术和一种高性能的信道编码(多重级联奇偶校验码)技术融入802.11a系统中,以使系统具有更高的可靠性和更大的可行性。研究工作主要分为三部分,第一部分以IEEE802.11a标准为背景,研究OFDM的几个关键技术,包括同步技术、信道估计及降低峰均比技术。根据802.11a协议标准进行参数设定,搭建物理层仿真平台,进行性能仿真;第二部分研究了一种以奇偶校验码为子码的多维Turbo分组码(简称多重级联奇偶校验码),并用三重串联奇偶校验码(3-SC-SPC)取代卷积码,构建新的基于IEEE802.11a标准的OFDM系统;第三部分研究了分层空时码(LSTC)、空时网格码(STTC)和空时分组码(STBC)三类空时编码技术,并研究了基于空时编码技术MIMO-OFDM系统,最后构建基于IEEE802.11a标准的MIMO-OFDM系统。
通过仿真得到以下有益结论:(1)多重级联奇偶校验码来说,在相同的译码条件下,其串并混三种编码结构性能有一定差异,其中串行多重级联奇偶校验码能够获得比卷积码明显好的性能。因此在实际应用中,编译码相当简单的串行多重级联奇偶校验码可以考虑取代业已成熟的卷积码。(2)基于IEEE802.11a标准构建的新的OFDM和MIMO-OFDM系统,在性能上比原802.11a系统具有很大改善。
WLAN (Wireless Local Area Network) is an important part of future mobile communications systems. As a choice of wireless access technology, WLAN taking the IEEE 802.11 series as the representative is popular in lots of customers and merchants who deal in access network, and gets a large development. On the other hand, the research on the core techniques of the next generation WLAN is becoming one of the hotspots in communications market, which extensive expert and scholar pay attention to. And it's to be the inevitable choice for the next generation wireless mobile communications, that is the combination of MIMO(Multiple-Input Multiple-Output) taking space-time coding as its key technique and OFDM (Orthogonal Frequency Division Multiplexing) .
This thesis mainly investigates the physical system of IEEE802.11a which adopts OFDM . MIMO technique and a kind of high performance channel codes (Multiple single parity check codes) apply to 802.11a system, in order to realize possibility systems with higher credibility and greater possibility. This paper mainly presents three parts. The first part, taking IEEE 802.11a as background, is focused on the research of several key techniques of OFDM, including synchronization, channel estimation and reducing peak-to average power ratio. The parameter and physical layer simulator are designed based on 802.11a,then carry out the performance simulation; The second part studies one special multiple concatenated Turbo block codes which employ single parity check codes as their component codes (also be called multiple single parity check codes). Using three series single parity check codes(3-SC-SPC) to replace convolution codes , set up a new OFDM system based on IEEE 802.11a ; The last part pays more attention to space-time code including LSTC, STTC and STBC, and does research on MIMO-OFDM based on space-time coding, then sets up a new MIMO-OFDM system based on IEEE 802.11a.
We attain main conclusions on the following two aspects: (1) multiple single parity check codes with different coding structures have different but regular performance variation, performance of series coding structure is distinctly better than convolution coding. Therefore, it's considered that using series single parity check coding with simple encoding structure to replace already mature convolution code.(2)The two new systems, OFDM and MIMO-OFDM systems setting up based on IEEE 802.11a, have more improvement than the original 802.11a system on performance.
引文
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