無線都會網路之下行邊界偵測和載波頻率飄移同步設計

Abstract

IEEE802.16e 標準是為了增加IEEE802.16-2004移動性而提出的修正規格。正交多頻多工存取(OFDMA)技術被使用來支援多重存取的目的。在此論文中，我們將專注於討論運用在時速高達120公里多重天線系統下的同步問題。以相關性(correlation)為基礎的演算法利用前置碼(preamble)的特性被應用在符號邊界及載波頻率飄移的同步估測。透過量化(quantization)的方法，乘法器的數量可以被大幅度減少成只使用加法器。此外，我們提出乒乓(ping-pong)演算法來增加整數載波頻率同步估計的準確性。使用龍捲風式的記憶體存取法，節省了28%的記憶體使用。而修正有號數的計算過程成無號數的運算，則節省了28%的面積及22%的功率消耗。設計結果顯示整體相較於原架構將達到節省56%面積及64%的功率消耗。整個同步電路一共使用82017個邏輯閘數量(gate count)及12.5mW的功率。

IEEE 802.16e standard is an amendment to IEEE 802.16-2004 for supporting mobility of WMAN. For the purpose of multiple access, Orthogonal Frequency Division Multiple Access (OFDMA) modulation scheme, is adopted. In this thesis, we focus on the synchronization problems of WMAN system which supports high mobility up to 120 km/hr and multiple transmitting antennas environment. The correlation based algorithms which use the characteristic of preamble are used for symbol timing synchronization and carrier frequency synchronization. By using quantization scheme, the use of multipliers can be substantially reduced and simplified to only adders. Moreover, a ping-pong algorithm for integer carrier frequency offset synchronization is proposed to increase the accuracy of estimation. By using the twister memory access operation, 26% memory cost is saved. Furthermore, a modified architecture of calculation process from signed to unsigned reduces 28% area and 22% power cost. Design results show that total 56 % area reduction and 64% power saving are achieved than the original architecture. The overall synchronization block uses 82017 gates count with power consumption of 12.5 mW.