Simulation Study of Integrated Video, Voice, and Data Transmission in Hybrid-Code DS/CDMA Systems
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A possible way to integrate variable bit rate (VBR) services into conventional synchronous direct-sequence, code-division multiple access (DS/CDMA) systems is to assign a number of unique codes (multiple codes) to a given service which can be used whenever its bit rate exceeds the available channel bandwidth. This has the disadvantage, that the number of available spreading codes is reduced. Instead, an asynchronous system can be applied by assigning a common code to all users. However, occasional bit-synchronism in an asynchronous system will cause an unacceptable bit error rate (BER). Therefore a hybrid-code DS/CDMA system is proposed, where common-codes are used only for mobile stations (MS) with VBR services. A self-control mechanism is applied to guarantee bit-asynchronism between the bits spread by the same code. In order to optimize the coding of video and voice sources, it is necessary to know the statistical characteristics of bit and packet errors. Simulation-based mobile network traffic models for integrated VBR video, interactive PCM coded speech and bulk transfer of data have been examined to obtain the BER performance of the system. Various channel models have been applied to macrocellular mobile networks. A conventional correlation receiver (single user detector: SUD) and a multi-user interference rejecting receiver are studied for the BS.
KeywordsMean Square Error Fading Channel Mobile Station Virtual Channel Spreading Code
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