Anas Basalamah

Rate Adaptive Reliable Multicast MAC Protocol for WLANs

IEEE 802.11b standard provides 1, 2, 5.5, 11 Mbps data rates. These data rates can be made possible by using different modulation techniques: DBPSK, DQPSK, CCK5.5 and CCK11 respectively. Rate adaptation is the process of dynamically selecting a proper modulation scheme depending on channel conditions in order to improve total throughput. Current rate adaptation protocols deal with unicast links rather than multicast. Channel conditions can be estimated by measuring the received signal strength (RSS) of a feedback message (CTS, ACK). However, IEEE 802.11 standard does not provide feedback messages for MAC layer recovery on multicast frames. This is due to collisions which may occur to simultaneous feedback messages from multicast group members. Therefore, in order to rate adapt multicast, a reliable multicast MAC protocol has to be introduced. In this paper, we propose a protocol which provides multicast reliability to WLANs and enhances its throughput by using rate adaptation. Further, we evaluate our protocol by throughput analysis and computer simulation. Simulation results suggest that our protocol performs better than a related/existing protocol in both throughput as well as reliability performances

Adaptive FEC Reliable Multicast MAC Protocol for WLAN

For end-to-end wireless multicast applications like multimedia conferencing, voice over IP and video/audio streaming applications which require reliable transmission of frames within short delivery delay, adding MAC layer H-ARQ (hybrid automatic repeat request) can enhance reliability and delivery delay. However, IEEE802.11 does not support reliable multicast due to its inability to exchange ACKs with multiple recipients. In this paper, we propose a protocol that enhances WLAN reliability performances by using adaptive FEC (forward error correction) while maintaining an optimal throughput performance.

A Rate Adaptive Multicast Protocol for Providing MAC Layer Reliability in WLANs

IEEE802.11b standard provides 1, 2, 5.5, 11 Mbps data rates. These data rates can be made possible by using different modulation techniques: DBPSK, DQPSK, CCK5.5 and CCK11 respectively. Rate adaptation is the process of dynamically selecting a proper modulation scheme depending on channel conditions in order to improve total throughput. Current rate adaptation protocols deal with unicast links rather than multicast. Measuring the received Signal Strength (RSS) of a feedback message (CTS, ACK) to estimate the receivers link condition, can be one way to do this. A receiver may send its channel condition information to the sender allowing it to adapt its data rate for the following transmission. IEEE802.11 standard however, does not provide feedback messages for MAC layer recovery on multicast frames. This is due to collisions occurring if multicast group members simultaneously initiate a feedback message. Therefore, in order to link adapt multicast, a reliable multicast MAC protocol has to be introduced. In this paper, we propose a Rate Adaptive Multicast (RAM) protocol which provides reliability to WLANs and enhances its throughput by using Rate Adaptation. Further, we evaluate our protocol by throughput analysis and computer simulation. Simulation results suggest that our protocol performs better than related/existing protocols in both throughput as well as reliability.

A Comparison of Packet-Level and Byte-Level Reliable FEC Multicast Protocols for WLANs

For wireless multicast applications like multimedia conferencing, voice over IP and video/audio streaming which require reliable transmission of packets within short delivery delay, adding forward error correction (FEC) can enhance packet error rate (PER) performance under low channel conditions, but cannot guarantee a reliable transmission. However, for applications like file transfer, distributed computing, chat and whiteboard sharing, reliability is crucial to the performance of the application. Reliable FEC or hybrid automatic repeat request (H-ARQ) can provide reliability, and can be deployed at different levels of the protocol stack. In this paper, we compare the performance of a reliable packet-level FEC protocol and a reliable byte-level FEC protocol through simulation and analytical analysis. Our result show that byte-level FEC can deliver a higher reliability performance in terms of throughput and delivery ratios.