Dynamical effects of time delays and time delay compensation inpower controlled DS-CDMA

摘要

Transmission power control is essential in systems of thenthird-generation (3G) in order to optimize the bandwidth utilization,nwhich is critical when variable data rates are used. One remainingnproblem is oscillations in the output powers, due to round-trip delaysnin the power control loops together with the power up-down commandndevice. The oscillations are naturally quantified using discretentime-describing functions, which are introduced and applied. Morenimportantly, time delay compensation (TDC) is proposed to mitigate thenoscillations. When employing TDC, the power control algorithm exhibitsngreater stability, which is important from a network perspective.nSimulations illustrate the oscillations and the benefits of TDC.nMoreover, the fading tracking capability is improved, and thus, lessnfading margin is needed. The results apply not only to wideband codendivision multiple access (WCDMA), but to other direct-sequence (DS) CDMAnsystems power controlled in a similar manner as well