A Differential Decoding Based Baseband Processor for DSSS Wireless LAN Applications

• Main Authors: Chien-Jen Hung, 洪健仁
• Other Authors: Chen-Yi Lee
• Format: Others
• Language: en_US
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/26820117506696467595

碩士 === 國立交通大學 === 電子工程系 === 91 === Direct sequence spread spectrum (DSSS) technique is used in IEEE 802.11, 802.11b and 802.11g wireless LAN systems. Unlike the wire channel, wireless communication uses radio as its medium and has more uncertainty with it. Therefore, WLAN frame format generally contains preamble field for synchronization. We would like to use the Barker spread preamble field to eliminate non-ideal channel effects including Additive White Gaussian Noise (AWGN), carrier frequency offset (CFO), carrier phase offset (CPO), and sampling clock offset. Therefore, symbol synchronization, frequency synchronization, phase synchronization and timing synchronization algorithms based on differential decoding concept were proposed. With our algorithms, the receiver would extract all the channel parameters only with the PLCP preambles and does not need any help from the MPDU which would reduce the CCK demodulator cost where dominates the cost of the system. These algorithms would benefit the IEEE 802.11g system which has the CCK-OFDM mode, the frame consists of the Barker PLCP and OFDM MPDU. To get familiar with IEEE standards, simulation platforms were set up with Matlab mathematical software which let us have a chance to probe signals in every place inside the system and visual view of the channel effects including CFO, AWGN, clock drift and even multipath. With this platform, our algorithms could be verified. Some simulation results were shown in this thesis. Architectures of key components were discussed and gate counts of which were listed as well.