適用於IEEE802.11n通訊標準之可重組態奇異值分解引擎

Reconfigurable SVD Engine Design for IEEE 802.11n Standard

鄭庭鈞(Ting-Jyun Jheng)

指導教授 ： 吳安宇

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.01047

摘要

隨著無線區域網路應用的普及，使用者對於頻寬的需求越來越高，現存無線區域網路(WLAN)規格所能提供的傳輸速率漸漸不敷使用，而IEEE 802.11n的主要目的是制定一個新的WLAN標準以提供更高的傳輸速率，以便滿足現在及未來的頻寬需求。而此標準和其它WLAN規格最大的不同即是採用正交分頻多工(OFDM)技術以及多輸入多輸出(MIMO)技術的結合，使得傳輸速率能夠大幅的提升。
在MIMO無線通訊環境中，傳送端的每一個天線所傳送的信號會經由多個路徑傳輸，所以接收端的每一個天線除了接收到所想要的信號外，還會接收到其它傳送訊號的干擾。因此，如何有效消除天線之間的相互干擾為MIMO系統中非常重要的議題。經由消息理論(Information Theory)已證明出奇異值分解(Singular Value Decomposition, SVD)是實現MIMO系統的最佳方法。利用SVD技術，原本天線間受到相互干擾的通道環境可等效成數個完全獨立的通道傳輸，使系統擁有更高吞吐量(Throughput)、降低資料錯誤率、有效抗多路徑干擾，並且能夠有效解決通道不良狀況的問題。因此，SVD技術在MIMO系統中扮演著相當重要的角色，而IEEE 802.11n也將此技術納入在標準之中。
本作品的目標是在支援IEEE 802.11n通訊系統之下，我們提出一套完整的SVD演算法及硬體架構設計，其所具備特性如下：(1)可重組化：在IEEE 802.11n通訊標準裡，傳送端及接收端的天線數可以有所不同，傳送或接收天線數最多為4個，對於不同的通道情形常會使用不同的傳收天線配對數，一共有16種模式，所提出的可適性SVD演算法可同時支援這16種模式並且在硬體架構設計上達到可重組化的目的。 (2)快速收歛：所提出的演算法可在不失精準度的要求下來達到快速奇異值分解，可使系統達到更高的吞吐量。(3)提早結束：利用提早結束的機制來減少運算單元的閒置時間且提高其硬體使用率，降低系統延遲。 (4)資料交錯交織：在IEEE 802.11系統中有數十個以上的子頻帶，每個子頻帶有屬於自己的通道，所以每個子頻帶都需要做SVD的運算，因此所提出的SVD架構設計利用資料交錯交織技巧可同時針對16個通道作奇異值分解，以達到高硬體效益的目的。
因應上述的特性，在此論文中，一個適用於IEEE 802.11n通訊標準的可重組化之奇異值分解引擎設計被提出來，並且實作在一顆以90nm CMOS製程核心面積大小為2.17 mm2的晶片上，最高頻率可操作在100 MHz。

關鍵字

奇異值分解 ； 多輸入輸出 ； 正交分頻多工

並列摘要

With the popular application of wireless local area network (WLAN), there is an increasing demand for bandwidth by the users. Some existing WLAN specifications can not provide adequate transmission rate gradually. The main purpose of IEEE 802.11n WLAN standard is to provide a higher transmission rate to meet present and future bandwidth requirements. The difference between IEEE 802.11n and previous standards is the use of multiple input multi output (MIMO) technique combining with OFDM which causes substantially improvement of transmission rate.
In the MIMO wireless communication environment, the signal of each transmit antenna will be transmitted via multiple transmission paths, so the receiving end of each receive antenna will receive the desired signal and other interference signals. Therefore, how to effectively eliminate the interferences between each antenna is a important topic for MIMO system. Information theory has proved that MIMO system has the best performance while applying singular value decomposition (SVD). Using SVD, the interferences between transmit antennas and receive antennas will be eliminated and the MIMO channel is changed into several completely independent paths for transmission. The advantages of using SVD for communication system include the higher throughput, reducing the data error rate, effective against multi-path interference, and effectively solving the bad channel situation. Therefore, the SVD technique in MIMO systems plays an important role, and it is also included in IEEE 802.11n standard.
In the thesis, we propose a complete set of SVD algorithm and hardware architecture design, which has the characteristics as follows: 1) 16 mode reconfigurable design for different number of transmit antennas and receive antennas defined in IEEE 802.11n standard, 2) real time and fast convergence operation for all channel matrices of OFDM sub-carrier, 3) early termination scheme for improving system utilization and reducing system latency, and 4) data interleaving scheme for hundred of channel matrices
For the characteristics mentioned above, a reconfiguration SVD engine design for IEEE 802.11n standard is proposed. The design is implemented in a chip using 90nm CMOS process with core area of 2.17 mm2 and 100MHz maximum operational frequency.

並列關鍵字

singular value decomposition (SVD) ； multiple-input multi-output (MIMO) ； orthogonal frequency division multiplexing (OFDM)

參考文獻

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