Design and Implementation of WLAN Layer 1 and Layer 2 Core Techniques

• Main Authors: Cheng, Shau-Yu, 鄭紹余
• Other Authors: Hsu, Terng-Yin
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/39450774098228199116

博士 === 國立交通大學 === 資訊科學與工程研究所 === 99 === Recently, one of the major challenge for a IEEE 802.11 compatible receiver is to make the receiver architecture as compact as possible, i.e., efficient hardware sharing between non-cyclic prefix single-carrier block transmission (non-CP SCBT), single-input single-output (SISO) and multi-input multi-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems. Based on frequency-domain analog-to-digital conversion (FD-ADC) technology, this dissertation presents a multi-mode receiver to handle all digital signals in frequency domain. A frequency-domain (FD) symbol synchronizer adopting a symbol-rate sequential search with simple matched filter detection is presented to recover symbol timing over the frequency domain. Simulation and implementation results show that the proposed FD symbol synchronizer is robust at low single-to-noise (SNR) and low complexity for VLSI implementations. To make equalizer as compact as possible, a single-carrier frequency-domain equalization (SC-FDE) for non-CP SCBT is proposed with single-FFT architecture and sphere decoding algorithm. Thus, the equalization of IEEE 802.11b can reuse the hardware components in the MIMO-OFDM modem. Moreover, a pre-pruning scheme is designed to further reduce the complexity of MIMO detection module for MIMO transmission using spatial multiplexing. The pre-pruning scheme reduces the search space of conventional K-best algorithm by using the zero forcing (ZF) detection result and the property of multilevel structure in Nq-QAM constellation. Hence, it is very attractive for the receivers equipping with both K-best and ZF detectors. In spite the issues mentioned above in physical layer, a high rate wireless backhaul network transporting data between the access network and the wired Internet becomes essential due to the increasing of wireless high-speed Internet access. The infrastructure network becomes cost ineffective in the deployment of a high-rate wireless backhaul network due to the higher data rates requires much higher cell densities to realize in practice. Under this situation, IEEE 802.11s wireless mesh network (WMN) can provide an attractive approach for the fast and low cost deployment. This dissertation develops an IEEE 802.11s WMN and then deploys a testbed with 3-by-3 grid topology in both laboratory and field crossing three floors of the building. For the portability of mesh functions, the mesh development is a pure software extension for commercial off-the-shelf WLAN chipsets with modularized software design and without costly hardware modifications. To improve the transmission reliability of broadcast-type mesh control frames, several broadcasting strategies are evaluated based on the routing construction ratio, acceptable latency, and channel utilization in the laboratory testbed. For the WMN deployment, our observations indicate that RTS/CTS can improve throughput by up to 87.5%. Moreover, compared with the IEEE 802.11b/g, 802.11n achieves better fairness for multi-stream or multi-hop communications. The experimental observations of WMN deployment summarized in this dissertation are expected to provide guidance for the small or medium scale indoor IEEE 802.11s WMN.