A Novel Media Access Control Using Multiple Queues for Voice over IP in Ad Hoc Networks--D2VTS Algorithm--

Masakatsu OGAWA  Takeshi HATTORI  

IEICE TRANSACTIONS on Communications   Vol.E85-B   No.10   pp.2136-2144
Publication Date: 2002/10/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Mobile Multimedia Communications)
ad hoc network,  IEEE 802.11,  packet scheduling,  VoIP,  QoS,  

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Recently, demand for multimedia service applicable with wireless ad hoc networks is increasing. Many protocols which support QoS (Quality of Service) defined by ITU H.323 are suitable for the system with a central coordinator (ex. access point), and are not applied to ad hoc networks. Since each mobile station sends a packet randomly in a wireless network, it is necessary to avoid a packet collision which results in the decrement of the channel throughput. IEEE 802.11 is a standard for wireless LANs. The basic access mechanism in its media access control (MAC) protocol is the distributed coordination function (DCF) based on carrier sense multiple access with collision avoidance (CSMA/CA). However, this mechanism does not have QoS control, and packet collision may occur frequently with the increase of the number of mobile stations. In this paper, the two queues, voice over IP (VoIP) queue and DATA queue, are set in each mobile station, and we propose a novel MAC protocol using multiple queues for QoS. Our scheme consists of carrier sensing, packet scheduling and collision avoidance, and improves the contention window in DCF. We use two kinds of packet scheduling. One is the scheduling in a mobile station, and the other is the scheduling among mobile stations. We called the proposed scheduling among mobile stations D2VTS (Distributed Double Virtual Time Scheduling). Simulations are conducted to analyze the proposed scheme. The simulation results show that our scheme is able to carry multimedia traffic with a higher performance compared with the conventional DCF.