Adaptive power control based on a rake receiver configuration in wideband CDMA cellular systems (WCDMA) and methods of operation

• US 6,621,808 B1
• Filed: 10/07/1999
• Issued: 09/16/2003
• Est. Priority Date: 08/13/1999
• Status: Expired due to Term

• Current Assignee: Wistron Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Sadri, Ali S.
• Primary Examiner(s): Trost, William
• Assistant Examiner(s): Le, Danh C.
• Application Number:
  US09/413,935
• Time in Patent Office: 1,440 Days
• Field of Search: 370/335, 370/318, 370/468, 370/320, 455/422, 455/63, 455/69, 455/522, 455/273, 455/576, 375/144, 375/148, 375/150
• US Class Current: 370/335
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04W 52/24 using SIR [Signal to Interference Ratio] or other wireless path parameters
• CPC Class Codes: H04W 52/26 using transmission rate or quality of service QoS [Quality of Service]

Abstract

A WCDMA system includes a Base Station (BS) or forward transmitter and a pilot channel that transmits control signals between a Mobile Station (MS) and BS to reconfigure their transmitter/receiver according to the prediction of the channel power and channel power probability density function separated into three distinct equal probable regions. Data signals are encoded using a one-half Viterbi encoder and interleaved. The interleaved data bits are modulated using Quadrature Phase Shift Keying (QPSK) modulation. The QPSK data is multiplexed with the pilot channel and spread by an appropriate code in an OFDM transmitter modified by a long code. Output of the transmitter may be provided to two diverse antennas for reliable communications to the receiver. Data may be received at two diverse antennas. The outputs are provided to match filters coupled to a coherent rake receiver and a channel prediction system. The future attenuation of the channel coefficients and power are determined by the prediction system for several milliseconds. The power levels of each finger in the Rake receiver can be predicted and the strongest ones used in determining the optimum transmitter power or rate control for operating the system transmitters and receivers based on computing a long range power prediction of each finger of a rake receiver.

Claims

1. A Wide-band Code Division Multiple Access (“

WCDMA”

) system comprising a base station and a mobile station;

a channel including a baseband signal having a variable transmission rate and including a pilot channel coupling the base station and the mobile station;

means responsive to the baseband signal for predicting future power attenuation on the channels based on computing a long range power prediction of each finger of a rake receiver; and

means responsive to the channel prediction means to signal both the transmitter and receiver over the pilot channel to reconfigure the transmission rate according to the predicted power attenuation.

2. The system of claim 1 further comprising means establishing a power threshold in the channel.

3. The system of claim 2 further comprising means for increasing the transmission rate when the predicted channel power goes above the threshold.

4. The system of claim 2 further comprising means for decreasing the transmission rate when the predicted channel power falls below the threshold.

5. The system of claim 1 further comprising:

means for estimating or predicting channel coefficients at each rake finger F(1) . . . F(N); and

means for performing maximal power ratio combining by multiplying each finger F with its conjugate C.

6. The system of claim 1 further comprising:

means for choosing the fingers with the highest energy and performing maximal ratio combining on the selected fingers.

7. In a wide band code division multiple access (“

WBCDMA”

) system comprising a base station transmitter and receiver, a mobile station transmitter and receiver, dual channel each including a baseband signal having a variable transmission rate and a pilot channel coupling the base station and the mobile station, a method for improved throughput, channel capacity and transmit power control of the system, comprising the steps of;

predicting future power attenuation on the channels based on computing a long range power prediction of each finger of a rake receiver; and

signaling both the transmitter and receiver over the pilot channel to reconfigure the transmission rate according to the predicted power attenuation.

8. The method of claim 7 further comprising the step of:

establishing a power threshold in the channels.

9. The method of claim 7 further comprising the step of:

estimating or predicting channel coefficients at each rake finger F(1) . . . F(N); and

performing maximal power ratio combining by multiplying each finger F with its conjugate C.

10. The method of claim 7 further comprising the step of:

choosing the fingers with the highest energy and performing maximal ratio combining on the selected fingers.

11. The method of claim 8 further comprising the step of:

increasing the transmission rate when the predicted channel power goes above the threshold.

12. The method of claim 11 further comprising the step of:

decreasing the transmission rate when the predicted channel power falls below the threshold.