| dc.description.abstract | With the growing demand for multimedia services, video streams have become major traffic sources
in the Internet. However, it is challenging to transmit multimedia streams over IEEE 802.11 Wireless
Local Area Networks (WLANs) with high performance and reliability. As a solution to improve
system efficiency, a new standard, 802.11aa, is introduced to provide much more reliable
and robust transfer of video stream by introducing several new service features. In this thesis,
we analyze the performance of the Groupcast with Retries (GCR) Block ACK scheme as one of
the most important features in this standard based on Markov chain models. The properties of
groupcast service and block acknowledgement will be merged together in our model. Besides, we
take into account the memory feature of the wireless channel and extend it into multi-receivers
in accordance with the standard. In particular, the proposed model is built on fixed block size,
a type of communication technique in which the block size is kept as fixed during transmission.
Furthermore, the lost position of a packet in the block is taken into consideration for in-depth
analysis.
Numerical results show that under the groupcast with constant retry limit and fixed block size
transmission mechanism, the network throughput will be reduced with the growing number of
receiving terminals. Compared with the throughput result for the variable block size mechanism
obtained from our previous study, we found that with the increasing number of stations, the
performance of the fixed block size mechanism is much more stable with respect to the number
of stations and channel memory property. However, the variable block size transmission scheme
exhibits much better throughput performance when the number of stations is small. | no_NO |
