Medium access control protocols for multimedia traffic in wireless networks

Abstract

This article presents a survey on medium access control protocols for multimedia traffic in wireless networks. A basic o v e r v i e w o f MAC p r o t o c o l concepts i s presented, a n d a f r a m e w o r k i s d e v e l o p e d o n w h i c h t o b a s e q u a l i t a t i v e comparisons. The M A C protocols covered in this article include third-generation TDMA and C D M A schemes intended for use in a single-hop wireless system. The operation of each protocol i s explained, and its advantages and disadvantages are presented. Finally, a qualitative comparative outline of the discussed protocols is provided, based on multimedia traffic requirements.ne of the driving forces of the next generation of wireless communication and computing networks is the promise of high-speed multimedia services. Third-generation systems, such as the International Mobile Telecommunication System (IMT-2000) network (formerly known as the Future Public Land Mobile Telecommunication System, FPLMTS) and the Universal Mobile Telecommunication System (UMTS), promise to provide multimedia services to mobile and fixed users via wireless access to the global telecommunications infrastructure [l, 21. The IMT-2000 is a universal, multifunction, globally compatible digital mobile radio system that plans to integrate all traffic types and all wireless systems under a common set of formats. The standards for IMT-2000 Available bit rate (ABR) traffic (non-time-critical data) Unspecified bit rate (UBR) traffic (file transfer, system backup, e-mail) In a wireless system consisting of a number of mobile terminals that transmit traffic of any type on a shared medium to a centralized base station, a procedure must be invoked to distribute packet transmission among all users. This procedure is known as a medium access control (MAC) protocol. MAC protocols are often classified according to their method of resource sharing, as well as their multiple access technology [4]. The resource sharing methods include dedicated assignment, random access, and demand-based assignment. Dedicated channels assign each user a predetermined and fixed allocation of resources, regardless of the user's need to transmit. Dedicated assignment schemes are appropriate for continuous traffic, but can be wasteful for bursty traffic. On the other hand, random access channels allow all users to contend for the channel by transmitting as soon as packets are available to send. Random access is suitable for bursty data traffic, but is not desirable for delay-sensitive traffic. Demand-based assignment schemes assign resources according to requests, or reservations, submitted by users. Once the requests are transmitted (using either dedicated or random access channels) and processed, users can be assigned resources according to the results. Demand-based channels are useful for variablerate traffic and the hybrid conditions of multimedia traffic. However, the additional overhead and delay caused by the reservation process can degrade performance.In addition to the resource shar...

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