QoS aware transmission control scheme for multihop WiMAX network

• Published in: International journal of communication systems Vol. 27; no. 10; pp. 1766 - 1782
• Main Authors: Ismael, Fath Elrahman, Syed Yusof, Sharifah K., Abbas, Mazlan, Abdul Latiff, N.M., Fisal, Norsheila
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.10.2014
• Subjects: IEEE 802. 16j; QoS; RTO smoothing; TCP performance
• ISSN: 1074-5351; 1099-1131
• DOI: 10.1002/dac.2434

SUMMARY The IEEE 802.16j Mobile Multihop Relay (MMR) WiMAX network allows the number of hops between the end user and the base station to be more than two hops. It supports non‐real‐time Polling Service, which considers the minimum reserved rate and the maximum sustained rate as a QoS requirements. The reliability of sending the data over MMR WiMAX is achieved by using Transmission Control Protocol (TCP) in transport layer and automatic repeat request in the link layer. However, the use of automatic repeat request in the link layer makes the round trip time fluctuate rapidly, which increases the possibility of retransmission timeout (RTO) expiration. TCP performance degrades because of frequent timeout, and hence the QoS transmission rates cannot be satisfied. Therefore, this paper presents an RTO smoothing scheme and QoS aware transmission control to enhance the performance of data transmission over MMR WiMAX networks. The RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold and maximum congestion window are adjusted to satisfy the required QoS and it provides transmission rate fairness for the users at different hops. The results showed that, the proposed schemes reduce the timeout, and improve the utilization of the allocated resources and TCP throughput. Copyright © 2012 John Wiley & Sons, Ltd. This paper presents retransmission timeout (RTO) smoothing scheme and QoS‐aware transmission control to enhance the performance of data transmission over mobile multihop relay WiMAX network. RTO smoothing scheme aims to reduce the frequent timeout occurrences. The slow start threshold (ssthresh) and maximum congestion window (CWNDmax) are adjusted to satisfy the required QoS and provide transmission rate fairness for the users at different hops. The proposed schemes reduce the timeout and improve the utilization of the allocated resources and Transmission Control Protocol throughput significantly.