Norman P. Secord

On symbol-based turbo codes for cdma2000

Turbo codes have enjoyed a great attention. Among different soft-output decoding algorithms of turbo codes only maximum a posteriori (MAP) decoding as an iterative soft-output decoder (BCJR) allows for achieving an acceptable BER performance at Eb/No levels within only 1 dB of the value corresponding to the Shannon capacity. The drawback of the MAP algorithm is the excessive memory required. Here, we investigate the so-called symbol-based turbo codes. These codes allow for a reduced required memory by 30% for the BCJR method.

Performance of closed-loop power control for a multiple-channel mobile station in the cdma2000 system

We investigate the reverse link power control of the cdma2000 system where multiple traffic channel signals of different data rates are code-multiplexed and transmitted in a multipath Rayleigh fading environment. In particular, we evaluate the performance of a closed-loop power control scheme utilizing one power control command for all traffic channels. Simulation results show that the use of one common power control command may not be optimal for all code-multiplexed channel signals of different data rates. This is largely due to the different variations in the effective bit signal-to-interference-plus-noise ratios (SINRs) for a given fading rate in a multipath fading channel. With an observation of the performance improvement by more than 1 dB, we propose to use independent power control for each channel signal.