โพรโทคอลการควบคุมการเข้าถึงตัวกลางแบบใหม่บนพื้นฐานของวิธีที่มีการแข่งขันและไม่มีการแข่งขันสำหรับบริการแบบมัลติมีเดียในระบบการสื่อสารไร้สาย / อัครพล ธนสรวิศ = A new media access control protocol based on contention-free and contention-based schemes for multimedia services in wireless communication system / Akkarapol Thanasorravit
This thesis presents the design of an effective Media Access Control (MAC) protocol based on contention-free and contention-based schemes for supporting multimedia services in wireless communications. Channel bandwidth is efficiently assigned to each terminal according to the Quality of Services (QoS) required by each traffic type. In this thesis, the protocol design problem is divided into various design aspects as follows. First, each terminal that wishes to transmit a packet has to request for channel reservation on a random basis. Next, once the reservation attempts are successful, the terminal will then wait for the assignment of the information slot for its data transmission. The key aspect of this problem is how to find an appropriate scheduling mechanism to serve each successful terminal. In addition, the frame structure is another important issue that requires careful consideration as it greatly affects the system performance. Appropriate frame structure can help minimize the collision among terminals and result in high efficiency of channel utilization. Four distinct techniques have been proposed for solving the problems described above. They are as follows: 1) technique that reduces the number of requests in the system, namely multiple assignment, periodic assignment, the combination between multiple assignment and periodic assignment, piggybacking (PGBK), and queue 2) technique that avoids collision due to frequently simultaneous in the same request slot by selecting proper access probability with both fixed and dynamic schemes and distributing the request slots over each frame 3) technique that assigns the channel to the mobile terminals at base station, namely priority assignment by group of operation and group of traffic, generation time schedule (GTS) 4) technique that changes and adjusts the frame structure according to the traffic conditions. All these proposed schemes have been designed in such a way that they can operate independently so that the protocol designer can combine and apply simultaneously several schemes into a single system. However, the designer must understand deeply into the advantages and disadvantages of each scheme. As a result, this study aims to provide a full and comprehensive investigation of these schemes in various traffic characteristics. These findings can be used as a guideline to analyze and predict the characteristics and performance of new MAC protocols that currently exist or may emerge in the future. Finally, we have put together some of these schemes to form a new Media Access Control protocol that offers very desirable performance, i.e. 99% throughput, low delay performance, high stability and QoS guaranted.
