Traffic Control for Time-bounded Services over Wireless LAN

• Main Authors: Wen-Shuo Hsu, 許文碩
• Other Authors: Po-Ning Chen
• Format: Others
• Language: en_US
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/00635764047812151539

碩士 === 國立交通大學 === 電信工程系 === 87 === The growing spread of portable computers has made the wireless local area networks (WLANs) an emerging technology for today's communication industries. To support the requirements for the transmission of continuous media, multiple-service packet-switching networks must provide service guarantees to connections, including guarantees on throughput, network delays, and network delay variations. One of the demanding applications that are of research and practical interest is the time-bounded service, which requires deterministically bounded delay guarantees. In this thesis, we study the problem of conveying two-way conversational sources over guaranteed Quality-of-Service (QoS) wired network access to an PCF-enabled IEEE 802.11 wireless LAN. The traffic patterns considered is assumed to fit the telephony-type two-way conversational model, i.e., at any time instance, exactly one of the two persons (caller and callee) can generate voice data. This excludes the unlikely situations (for a normal conversation) that both persons talk at the same time, or both keep silence. The study based on such source model shall be useful when one intends to provide delay-sensitive telephony-type services over WLANs, e.g. to deploy WLANs over an historical building to provide the telephony-type services in addition to the data-type services. For the QoS guaranteed wired network side, we borrow three typical classes of source parameter-guaranteed models from Asynchronous Transfer Mode (ATM) networks: constant bit rate (CBR), variable bit rate (VBR), and available bit rate (ABR). Base on these pre-given QoS parameters, the Admission Control Criteria for standard-suggested Round-Robin-based Polling scheme (RR_Polling) and our newly proposed Eerliest-Deadline-First Polling scheme (EDF_Polling) are both derived under the premise that the down-link traffic (from the Access Point to the Wireless Station) is hard-guaranteed to satisfy them. The comparison of the schedulable regions of the RR_Polling and EDF_Polling is then followed. For those admitted traffics, we investigate the average delays of the up-link traffics for both RR_Polling and EDF_Polling schemes. Note that the up-link traffic indeed provides no QoS parameter exchanging mechanism due to IEEE 802.11, and hence, can not be hard-guaranteed in any sense. Pro-and-cons for different system factors, such as the length of contention-free period, as well as the data frame size, are also addressed.