Inverse multiplexing of IS95 traffic for video transmission

by Salmanian, Mazda

This thesis studies the transmission of video signals over an IS95 CDMA communication system through Rayleigh fading channels. The video encoder's (H.263cornpliant) bit rate ranges fi-om 16Kbps to 64Kbps with which the air interface (IS95) systern copes by adapting and assigning more channels to the video users dynamically. We consider up to 8 channels at 9600bps per video user. A channel in the reverse direction (mobile to the base-station) is identifid by the ESN (Electronic Serial Number) mask of the mobile; whereas a channel in the forward direction (base-station to the mobile) is identified by its Walsh code spreader. Effects of power control. slow and fast fading, and channel utilization are studied through simulation of severd scenarios involving audio and video users. Power control is required to maintain a reliable communication channel, especiaily at low mobile speeds: however it is observed that video-users do not require power control and synchronization per channel iike audio users do. The base-station manages the channels assigned to a video user as one. since their ongins are co-located. The system operates reliably in fast fading environments where the fade duration is severai rimes shorter than the interleaver's depth. It is also found that a video-user's channel utilkation is more efficient than that of an audio user. It is concluded that such system can reliably support 2 video users in the fonvard and reverse traffic channels with the presence of 6 to 8 audio interferers. Page iii