study on Physical Layer rate mode threshold selection in IEEE 802.11a WLAN

• Main Authors: Jian-kai Chen, 陳建凱
• Other Authors: Dou Chie
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/00746388174675333094

碩士 === 雲林科技大學 === 通訊工程研究所碩士班 === 96 === Eight different rate modes are supported, in the IEEE 802.11a PHY layer and the rate mode selection is often based on the SNR threshold determined by the link adaptation. We clarifies the distinction between the target SNR and the received SNR and their relationship to fading effects in the IEEE 802.11a WLANs. Given that the target SNR is fixed, the performance of the packet error rates of different received SNR values are investigated over frequency selective fading channels. We use ETSI/BRAN channel–A mode for simulation and adopt training-sequence based channel estimation method for stationary mobile stations in slowly time-varying environments. Both an analytical upper bound and a statistical average (via simulation) of the packet error rates of individually received SNR values were obtained. We demonstrates that by lowering the target SNR values, better PER performances under the same received SNR are obtained. This observation has a significant impact on the determination of the SNR thresholds for the 802.11a link adaptation. This thesis shown that the link adaptation thresholds between two comparative rate modes should be shifted downwards with the lowering of target SNR values. Along with introducing the throughput-based approach, we propose a bivariate mode selection boundary approach to facilitate the determination of the link adaptation between two comparative rate modes. Finally, the threshold shifting of the link adaptation of 802.11a for different target SNR values over the ETSI/BRAN channel–A model is presented, apt to choose a proper rate mode to transmits over frequency selective fading channels.