Multipath fading effects on integrated video, voice and data transmisson in hybrid-code BPSK-DS/CDMA systems
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). In our proposed hybrid-code DS/CDMA system common codes are used only for mobile stations (MS) with VBR services if the instantaneous required bandwidth exceeds the available channel bandwidth. A self-control mechanism is applied to guarantee bit-asynchronism between the bits spread by the same code. 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.
multipath fading variable bit rate (vbr) common code direct-sequence code-division multiple access (ds/cdma) quasiorthogonal codes gold code hybrid code asynchronous ds/cdma broadband services markov chain gsm propagation models