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spaper10 - Wireless Networks 8 355370 2002 2002 Kluwer...

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Wireless Networks 8, 355–370, 2002 2002 Kluwer Academic Publishers. Manufactured in The Netherlands. Multimedia Support for Wireless W-CDMA with Dynamic Spreading JU WANG, MEHMET ALI ELICIN and JONATHAN C.L. LIU Department of Computer, Information Science and Engineering (CISE), University of Florida, PO Box 116120, Gainesville, FL 32611, USA Abstract. The emerging multimedia communication needs more support in operating systems in order to be successful over a wireless environment. The system needs to support a seamless integration (i.e., transparent application switching) of voice, audio and conventional data (e.g., e-mails, and ftp). It should also support multiple users with a guaranteed quality. In this paper, we investigate effective protocol design with dynamic spreading factors such that various QoS based on different traffic types can be provided. Increasing spreading factors can benefit the system because it will increase the desired signal strength linearly. The measured bit error rate can be reduced 75 times with a long spreading factor. By taking advantage of this benefit, we propose some middle-ware solutions to monitor the network load and switch the spreading factors dynamically based on the current load with multimedia traffic. These middle-ware solutions are implemented in mobile and base stations and experiments are performed to measure the actual system performance. The preliminary results indicate that our proposed system can always maintain a desired quality for all the voice connections. We further extend our protocol to guarantee a balanced support among different traffic types. While the voice communication is still guaranteed to be non-interrupted, the data traffic is proved to be served with reasonable response time by our proposed system. Keywords: wide-band CDMA, Quality-of-Service, integrated multimedia communication, admission control protocol, dynamic spreading factors 1. Introduction Wireless networks make it possible for people to shop on- line anytime and anywhere. People will have instant access to information even when they are walking on the streets. In ad- dition, customers will not only have access to plain informa- tion, but the information will be supported with multimedia components like images, animations, and audio. Recent tech- nological advances are increasing multimedia capabilities in mobile devices. Cellular phones and notebooks are converg- ing into a single mini-device which is capable of both com- puting and communicating. They are becoming more com- petitive to desktop PC in terms of computing power. In the near future, most of the multimedia applications will be able to run on mobile devices. Therefore, a successful multimedia communication sys- tem needs to support a seamless integration of voice, audio and other conventional data (e.g., e-mails, and ftp). Table 1 lists the different traffic characteristics. We believe that ftp and e-mails require the highest support on the bit error rate (BER) since the accuracy of the content needs to be guaran- teed. However, there is no data rate requirement for these two
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