Scaling in a receiver for coded digital data symbols

• US 8,068,532 B2
• Filed: 10/21/2005
• Issued: 11/29/2011
• Est. Priority Date: 12/20/2004
• Status: Expired due to Fees

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Jonsson, Elias, Cedergren, Andreas
• Primary Examiner(s): Payne; David C.
• Assistant Examiner(s): Hassan; Sarah
• Application Number:
  US11/721,582
• Publication Number:
  US 20080008228A1
• Time in Patent Office: 2,230 Days
• Field of Search: 375/130, 375/355, 370/476
• US Class Current: 375/147
• CPC Class Codes: G06F 7/49936 Normalisation mentioned as feature only
• CPC Class Codes: G06F 7/523 Multiplying only
• CPC Class Codes: H04B 1/712 Weighting of fingers for combining, e.g. amplitude control or phase rotation using an inner loop
• CPC Class Codes: H04B 2201/70707 Efficiency-related aspects
• CPC Class Codes: H04B 2201/709727 GRAKE type RAKE receivers
• CPC Class Codes: H04B 7/0842 Weighted combining

Abstract

Coded digital data symbols sent through a transmission channel of a communications network are received in a receiver. Estimates (y) represented by a first number (a+b) of bits are calculated, and modified estimates (y′) represented by a second number (c) of bits provided therefrom, the second number being lower than the first number. An amplitude value is calculated for each estimate (y), and an averaged amplitude value calculated for a number of amplitude values. A scaling factor (s) is calculated form the averaged amplitude value, and scaled estimates generated in dependence of die scaling factor. The scaling factor is used for a number of scaled estimates corresponding to the number of amplitude values for which the averaged amplitude value was calculated. Thus a better scaling factor is provided for most channel cases, which can still be calculated with the limited computational resources of a terminal for such networks.

Claims

1. A method of receiving coded digital data symbols sent from a transmitter through a transmission channel of a communications network, the method comprising the steps of:

calculating estimates (y) of sent data symbols, each of said estimates being represented by a first number (a+b) of bits, wherein

the data symbols are transmitted in a plurality of time slots, and

the step of calculating estimates (y) further comprises the step of multiplying for a number of channels de-spread data symbols (r) by the conjugate value of a channel estimate (ĥ

) and summing multiplying results (ĥ

* r) for said number of channels;

providing from said calculated estimates modified estimates (y′

) represented by a second number (c) of bits, said second number (c) being lower than said first number (a+b), further comprising the steps of;

calculating an amplitude value for each of said calculated estimates (y);

calculating an averaged amplitude value for a number of said amplitude values;

calculating a scaling factor (s) from said averaged amplitude value, wherein the scaling factor (s) are recalculated for each time slot specified for the communications network among the plurality of time slots; and

in response to calculating the scaling factor (s), generating scaled estimates of sent data symbols in dependence of said scaling factor (s), said scaling factor (s) being used for a number of scaled estimates corresponding to the number of amplitude values for which the averaged amplitude value was calculated, wherein

the step of generating scaled estimates further comprises the step of multiplying each multiplying result (ĥ

* r) by said scaling factor (s); and

filtering said average amplitude value with a filtered amplitude value from a previous time slot among the plurality of time slots.

2. The method according to claim 1, wherein said number of amplitude values for which the averaged amplitude value is calculated corresponds to the number of data symbols in a time slot specified for said communications network.

3. The method according to claim 1, wherein the step of generating scaled estimates comprises the step of multiplying calculated estimates (y) by said scaling factor (s).

4. The method according to claim 1, wherein the step of calculating estimates (y) further comprises the step of multiplying for a number of channels de-spread data symbols (r) by the conjugate value of a channel estimate (ĥ

) and summing multiplying results (ĥ

* r) for said number of channels, and wherein the step of generating scaled estimates further comprises the step of multiplying each channel estimate (ĥ

) or its conjugate value by said scaling factor (s).

5. The method according to claim 1, wherein the step of calculating estimates (y) further comprises the step of multiplying for a number of channels de-spread data symbols (r) by combining weights and summing multiplying re-suits for said number of channels, and wherein the step of generating scaled estimates further comprises the step of multiplying each combining weight by said scaling factor (s).

6. The method according to claim 1 wherein said amplitude value is calculated as the average of the absolute values of an in-phase component and a quadrature component of each of said calculated estimates (y).

7. The method according to claim 1 wherein the step of calculating a scaling factor (s) comprises the step of using a control algorithm selected from the group consisting of a Proportional control algorithm, a Proportional Integral control algorithm and a Proportional Integral Derivative control algorithm.

8. A receiver for receiving coded digital data symbols sent from a transmitter through a transmission channel of a communications network, the receiver being arranged to:

calculate estimates (y) of sent data symbols, each of said estimates being represented by a first number (a+b) of bits, wherein the data symbols are transmitted in a plurality of time slots, wherein

the estimates (y) of sent data symbols are calculated by multiplying for a number of channels de-spread data symbols (r) by the conjugate value of a channel estimate (ĥ

) and summing multiplying results (ĥ

* r) for said number of channels;

provide from said calculated estimates modified estimates (y′

) represented by a second number (c) of bits, said second number (c) being lower than said first number (a+b), wherein the receiver is further arranged to;

calculate an amplitude value for each of said calculated estimates (y);

calculate an averaged amplitude value for a number of said amplitude values;

calculate a scaling factor (s) from said averaged amplitude value, wherein the scaling factor (s) are recalculated for each time slot specified for the communications network among the plurality of time slots; and

generate scaled estimates of sent data symbols in dependence of said scaling factor (s), in response to the calculation of the scaling factor (s), and wherein said scaling factor (s) being used for a number of scaled estimates corresponding to the number of amplitude values for which the averaged amplitude value was calculated, wherein

the scaled estimates of sent data symbols are generated by multiplying each channel estimate (ĥ

) or its conjugate value by said scaling factor (s); and

filter said average amplitude value with a filtered amplitude value from a previous time slot among the plurality of time slots.

9. The receiver according to claim 8, wherein said number of amplitude values for which the averaged amplitude value is calculated corresponds to the number of data symbols in a time slot specified for said communications network.

10. The receiver according to claim 8 or 9, wherein the receiver is further arranged to generate scaled estimates by multiplying calculated estimates (y) by said scaling factor (s).

11. The receiver according to claim 8, being arranged to calculate estimates (y) by multiplying for a number of channels de-spread data symbols (r) by the conjugate value of a channel estimate (ĥ

) and summing multiplying results (ĥ

* r) for said number of channels, wherein the receiver is further arranged to generate scaled estimates by multiplying each multiplying result (ĥ

* r) by said scaling factor (s).

12. The receiver according to claim 8, being arranged to calculate estimates (y) by multiplying for a number of channels de-spread data symbols (r) by combining weights and summing multiplying results for said number of channels, wherein the receiver is further arranged to generate scaled estimates by multiplying each combining weight by said scaling factor (s).

13. The receiver according to claim 8 wherein the receiver is further arranged to calculate said amplitude value as the average of the absolute values of an in-phase component and a quadrature component of each of said calculated estimates (y).

14. The receiver according to claim 8 wherein the receiver is further arranged to calculate a scaling factor (s) by using a control algorithm selected from the group consisting of a Proportional control algorithm, a Proportional Integral control algorithm and a Proportional Integral Derivative control algorithm.

15. A receiver according to claim 8 wherein the receiver is a WCDMA receiver.