An 802.11e HCCA scheduler with an end-to-end quality aware territory method

• Published in: Computer communications Vol. 32; no. 11; pp. 1281 - 1297
• Main Authors: Navarro-Ortiz, Jorge, Ameigeiras, Pablo, Ramos-Munoz, Juan J., Lopez-Soler, Juan M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 03-07-2009
• Subjects: HCCA; Quality of Experience; Resource allocation; Scheduler; HCCA; Quality of Experience; 802.11e; Scheduler; Resource allocation
• ISSN: 0140-3664; 1873-703X
• DOI: 10.1016/j.comcom.2008.12.014

In this paper we present a solution for the IEEE 802.11e HCCA (
Hybrid coordination function Controlled Channel Access) mechanism which aims both at supporting strict real-time traffic requirements and, simultaneously, at handling TCP applications efficiently. Our proposal combines a packet scheduler and a dynamic resource allocation algorithm. The scheduling discipline is based on the
Monolithic Shaper-Scheduler, which is a modification of a
General Processor Sharing (GPS) related scheduler. It supports minimum-bandwidth and delay guarantees and, at the same time, it achieves the optimal latency of all the GPS-related schedulers. In addition, our innovative resource allocation procedure, called the
territory method, aims at prioritizing real time services and at improving the performance of TCP applications. For this purpose, it splits the wireless channel capacity (in terms of transmission opportunities) into different territories for the different types of traffic, taking into account the end-to-end network dynamics. In order to give support to the desired applications, we consider the following traffic classes:
conversational,
streaming,
interactive and
best-effort. The so called territories shrink or expand depending on the current quality experienced by the corresponding traffic class. We evaluated the performance of our solution through extensive simulations in a heterogeneous
wired-cum-wireless scenario under different traffic conditions. Additionally, we compare our proposal to other HCCA scheduling algorithms, the HCCA reference scheduler and
Fair Hybrid Coordination Function (FHCF). The results show that the combination of the MSS and the territory method obtains higher system capacity for VoIP traffic (up to 32 users) in the simulated scenario, compared to FHCF and the HCCA reference scheduler (13 users). In addition, the MSS with the territory method also improves the throughput of TCP sources (one FTP application achieves between 6.1 Mbps without VoIP traffic and 2.1 Mbps with 20 VoIP users) compared to the reference scheduler (at most 388 kbps) and FHCF (with a maximum FTP throughput of 4.8 Mbps).