DL Power Control in WCDMA

[s.sunilpal123]

Hello friends.

Another question I can't answer...Pls help me decode this.

WCDMA is CDMA technology. Consider Downlink. All the users' data is sent on same carrier. Users within same cell are differentiated by their OVSF codes. Now when we talk of power control in DL, we say that a UE-one nearer to nodeB is entitled to less power from the nodeB than a UE-two which is at the cell edge.

What I fail to understand is how is this nodeB power for the UEone is being decreased...What parameter is controlled to reduce this power for the UEone? As it is CDMA, one cannot reduce the nodeB power as then all users' received power will decrease. How is this 'individual' node B power to a particular UE decreased? Is it just varying the amplitude of the input signal, or of the carrier during modulation or during channel coding or during spreading?

[jan74]

Hello friends.

Another question I can't answer...Pls help me decode this.

WCDMA is CDMA technology. Consider Downlink. All the users' data is sent on same carrier. Users within same cell are differentiated by their OVSF codes. Now when we talk of power control in DL, we say that a UE-one nearer to nodeB is entitled to less power from the nodeB than a UE-two which is at the cell edge.

What I fail to understand is how is this nodeB power for the UEone is being decreased...What parameter is controlled to reduce this power for the UEone? As it is CDMA, one cannot reduce the nodeB power as then all users' received power will decrease. How is this 'individual' node B power to a particular UE decreased? Is it just varying the amplitude of the input signal, or of the carrier during modulation or during channel coding or during spreading?

You see it is not really CDMA..... There are some channels which are Common Access Channels and most of these do not actually use Power Control, such as FACH, or CPICH etc. The Channels used to transfer data(DCH) are power controlled but they are dedicated to a given UE. Therefore the Node B know what TX Power to allow for a given user based on measurements he has sent.

[s.sunilpal123]

Does the nodeB then reduce the signal power before channel coding, spreading and modulation steps or during one of these steps?

[hesh]

Does the nodeB then reduce the signal power before channel coding, spreading and modulation steps or during one of these steps?

here is the answer "channel coding.spreading and modulation" takes place to encode the data, and this data is mapped on PDCH channel...

Power control is done for this channel only (DCH for specific UE)

Hope this will help