Wireless LANs
Protocols, Security & Deployment
By Anand R. Prasad
December 2003
Delft University Press
ISBN: 90-407-2436-9
200 pages, Illustrated, 6 ½" x 9 ½"
$69.50 Paper Original
This is a Ph.D. dissertation. This thesis presents a broad range of work done in the field of Wireless Local Area Networks (WLANs). It proposes several novel schemes of which performance are analyzed. The thesis first proposes an Automatic Repeat reQuest (ARQ) scheme named as Selective Repeat / Multi-Copy (SR/MC). The purpose of the proposed SR/MC ARQ scheme is to transmit Internet Protocol (IP) packets efficiently in WLANs.
At first the proposed scheme fragments an IP packet and transmits the fragments in Selective Repeat (SR) mode until the last fragment is transmitted after that, if erroneous fragments are still left, it goes in Multi Copy (MC) mode. In MC mode multiple copies of erroneous fragments are transmitted cyclically. A numerical performance analysis of the proposed SR/MC ARQ scheme is done and all its parameters are optimized. Using the simulation results of the Physical layer the optimized values are then used to study the performance of the scheme in terms of throughput both in an Additive White Gaussian Noise (AWGN) channel and a flat Rayleigh fading channel. The numerical results show that the proposed SR/MC ARQ scheme gives an improvement of 8 dB when compared to the Selective Repeat + Stutter Scheme 2 (SR + ST 2) scheme, under flat Rayleigh fading channel using BCH(63,51,2) for the throughput of 0.9. The measurement results also show similar performance. The proposed SR/MC ARQ scheme was implemented and applied for patent by the author; it was used for Wireless Network Interface Card (WNIC), a proprietary WLAN, of Uniden Corporation, Tokyo, Japan.
Next a novel Medium Access Control (MAC) protocol, named as Channel Sharing Protocol (CSP), is proposed. The proposed CSP uses tokens in the wireless medium to give fair access of the medium to a large number of users. The scheme uses a p-persistence algorithm to avoid collision. Simulations were performed to optimize the different parameters of the proposed CSP and to study its performance. A numerical study was also done for performance evaluation. There is a difference between the numerical and simulation results due to the assumptions made during the numerical performance evaluation. Both the numerical and the simulation results show that the proposed CSP outperforms the Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) MAC protocol of the IEEE 802.11 WLANs. A detailed design of the proposed CSP for implementation in WNIC was done and it was applied for patent by the author.
Information Technology
Return to Coronet Books main page