Transmit power adaptation for CDMA communication systems...

Details Transmit power adaptation for CDMA communication systems... Transmit power adaptation for CDMA communication systems...

2005-03-10

2008-08-05

Ghayour, Mohammed (Department: 2611)

Pulse or digital communications

Spread spectrum

Direct sequence

C455S522000

Reexamination Certificate

active

07408975

ABSTRACT:
Transmit power adaptation for DS/CDMA systems is disclosed for a CDMA system that utilizes a successive interference cancellation receiver on fading channels. The transmission power is adapted in response to channel variations to achieve an arbitrary power profile for received signal powers at the system base station. That is, the received signal powers are distributed with some factor xi's given as:in-line-formulae description="In-line Formulae" end="lead"?SRi=SR(1)xi, (i=2, 3, . . . , Kandx1=1)in-line-formulae description="In-line Formulae" end="tail"?where K is the number of users and SR(i)is the received signal power of the user having the ithstrength, and wherein user strengths are ranked in the order of estimated channel gains. The factor xigives a measure of the disparity between the received power levels. The channel is estimated at both the transmitter and receiver. In one embodiment, the factors, xi, for distributing the signal powers are selected such that the average BER for each user is minimized. In another embodiment, the factors, xi, for distributing the signal powers are selected such that, after successive interference cancellation, an instantaneous BER for all users is equal.

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