Development and Performance Evaluation of an MAC Protocol for MC-CDMA Wireless LANs with QoS Support
Authors: Orfanos, Georgios
Department of Communication Networks (ComNets), Faculty 6, RWTH Aachen University
: Gabi Reimann
Ph. D. Dissertation Aachen University, ABMT 52, p. 228, ISBN:3-86130-931-9,Wissenschaftsverlag Mainz, 2006.
Publication Date: , 2006
On page(s):228
ISBN: 3-86130-931-9
Abstract The Institute of Electrical and Electronics Engineers, Inc. (IEEE) standards 802.11a,e are currently established as worldwide standards for Wireless Lo¬cal Area Networks (WLANs). Applying Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA), the Distributed Coordination Function (DCF) and Enhanced Distributed Coordination Function (EDCF) protocols deploy minimum complexity in Medium Access Control (MAC), while the use of Orthogonal Frequency Division Multiplex (OFDM) in Physical layer (PHY), promises high data rates of up to 54 Mbit/sec. The system throughput at MAC layer is though reduced both, from the overhead and in so called hot spot scenarios by the high number of collisions which limit the system's performance and consequently its Quality of Service (QoS) achievements. A possible improvement, is the application of a new multiple access method, namely Multi-Carrier Code Division Multiple Access (MC-CDMA). MC-CDMA is a novel, high capacity, multicarrier modulation scheme, which is developing to a key radio transmission technology for future WLANs. Besides the fact that its Bit Error Rate (BER) performance (in fully loaded indoor communication systems) is due to the spreading gain better than that of Orthogonal Frequency Division Multiple Access (OFDMA), when low or no mobility scenarios are considered, MC-CDMA can reduce the probability of collisions, due to its inherent characteristic of operating parallel, from spreading sequences distinguished, channels in the same frequency channel. Thus the system throughput enhances and the delay reduces. The system throughput profits further as spreading improves the ratio of frame length to guard intervals, thus implicitly reducing the overhead. This thesis provides an overview of the MC-CDMA technique, and a performance evaluation in real multiuser transmission channel conditions. Further, the MC-CDMA is applied in the PHY of the IEEE 802.11a system. Accordingly, the needed modifications to the MAC protocol are done. In this respect, a new DCF for the MAC protocol is presented and evaluated, optimized for the multi channel structure of a MC-CDMA network, called Coded-Distributed Coordination Function (C-DCF), which achieves high efficiency. However in adhoc Code Division Multiplex Access (CDMA) networl near-far effects can block a receiver due to high interference. These effects occur when a receiving station is closer to an interferer than to its corresponding transmitter. Accordingly, the receiver cannot detect the intended signal out of the received one and the data transmission fails. Therefore the distributed, WLAN, MAC protocol presented in this thesis is enhanced by adaptation algorithms, which mitigate the effects of the near-far problem, and allow WLANs to improve significantly their performance and achieve high efficiency even under heavy multiuser interference, as is typical for ad- hoc operation.
Author Keywords
DownloadBibtex
@PHDTHESIS{DISS_ORFANOS_2006,
AUTHOR = {Orfanos, G.},
TITLE = {Development and Performance Evaluation of an MAC Protocol for MC-CDMA
Wireless LANs with QoS Support},
YEAR = {2006},
VOLUME = {52},
PAGES = {228},
PUBLISHER = {Wissenschaftsverlag Mainz},
ADDRESS = {Aachen, Germany},
SCHOOL = {Aachen University},
SERIES = {ABMT},
EDITION = {1},
AFFILIATION = {Department of Communication Networks (ComNets), Faculty 6, RWTH Aachen University},
ISBN = {3-86130-931-9},
URL = {https://www.comnets.rwth-aachen.de}
}
Signature in CN-Library = {A85}