Apparatus and method for signal strength compensation of highly time-variant mobile radio channels and reception unit for mobile radio transmission
View Patent ↗A signal strength compensation unit for mobile radio receivers is connected upstream of the channel estimator and the channel equalizer and compensates for, in particular, the great, brief signal strength fluctuations within a data burst. Likewise, a method for signal strength compensation compensates for brief signal strength fluctuations within the data burst. To these ends, a signal strength average is determined from the signal strengths for the previously received data symbols. The current signal is then aligned with this signal strength average. The inventive signal strength compensation allows the bit error rate during data equalization to be significantly reduced.
1. An apparatus for signal strength compensation for a sequence of received digital signal values in a mobile radio receiver, comprising:
a signal strength determiner producing a signal strength value representing a signal strength of a current digital signal value;
a calculator calculating a signal strength average, tracked to the current digital signal value, from previous digital signal values in the sequence; and
a signal strength aligner aligning the current digital signal value with the signal strength average by using a calculation.
2. The apparatus according to claim 1 , wherein said signal strength aligner has a division unit dividing the current digital signal value by the signal strength average.
3. The apparatus according to claim 1 , wherein said signal strength aligner determines the signal strength average from respective signal strength values for the previous digital signal values in the sequence, including the signal digital strength value of the current signal.
4. The apparatus according to claim 1 , wherein said signal strength aligner determines the signal strength average from respective signal strength values for the previous signal values in the sequence without the signal strength value of the current signal value.
5. The apparatus according to claim 1 , wherein the received digital signal values are complex signals respectively including an inphase signal and a quadrature signal.
6. The apparatus according to claim 5 , wherein said signal strength aligner divides the inphase signal and the quadrature signal by the signal strength average.
7. The apparatus according to claim 5 , wherein:
the inphase signal has a magnitude;
the quadrature signal has a magnitude; and
said signal strength determiner determines the signal strength value representing the signal strength of the current digital signal value by adding the magnitude of the inphase signal and the magnitude of the quadrature signal.
8. The apparatus according to claim 5 , wherein said signal strength determiner determines the signal strength value representing the signal strength of the current digital signal value by:
squaring the inphase signal to form a squared inphase signal,
squaring the quadrature signal to form a squared quadrature signal, and
adding the squared inphase signal and the squared quadrature signal.
9. The apparatus according to claim 1 , wherein:
said calculator for calculating the signal strength average tracked to the current digital signal value includes an adder producing the signal strength average by adding a previous signal strength average multiplied by λ 1 and the signal strength value of the current digital signal value multiplied by λ 2 ; and
λ 1 +λ 2 =1.
10. The apparatus according to claim 9 , wherein said calculator for calculating the signal strength average tracked to the current signal value includes a register for storing the signal strength average, storing the respective current signal strength average, and making the respective current signal strength average available for calculating a next signal strength average.
11. The apparatus according to claim 9 , wherein:
λ 1 =1−2 −n ;
λ 2 =2 −n ; and
n is a natural number.
12. The apparatus according to claim 11 , further comprising a shift register for multiplying the digital signal strength value for the current signal value by λ 2 .
13. The apparatus according to claim 11 , further comprising an adder and a shift register for multiplying the previous signal strength average by λ 1 .
14. The apparatus according to claim 1 , wherein said signal strength aligner aligns the current signal with the signal strength average only if a variation in the signal strength within the sequence exceeds a prescribed threshold.
15. The apparatus according to claim 1 , wherein said signal strength aligner aligns the respective current digital signal values in the sequence with the respective signal strength averages for the sequence only if a maximum signal strength average for the sequence and a mean signal strength average for the sequence differ to a sufficient extent.
16. The apparatus according to claim 1 , wherein said signal strength aligner aligns the respective current digital signal values in the sequence with the respective signal strength averages for the sequence only if a quotient of a maximum signal strength average for the sequence and of a mean signal strength average for the sequence exceeds a prescribed threshold value.
17. A reception unit for mobile radio transmission, comprising:
a channel estimator ascertaining channel coefficients for modeling a transmission channel;
a channel equalizer equalizing received signals using the channel coefficients ascertained by said channel estimator; and
an apparatus for signal strength compensation according to claim 1 connected upstream of said channel estimator and said channel equalizer.
18. A method for signal strength compensation for a sequence of received digital signal values, which comprises the following steps:
a) ascertaining a signal strength value representing a signal strength of a current signal value;
b) determining a signal strength average tracked to the current signal value from previous signal values in the sequence; and
c) aligning the current signal value with the signal strength average determined in step b) by using a calculation.
19. The method according to claim 18 , which further comprises aligning the current signal value with the signal strength average determined in step b) by dividing the current signal value by the signal strength average.
20. The method according to claim 18 , wherein the signal strength average is determined from respective signal strength values for the previous signal values in the sequence, including the signal strength value for the current signal value.
21. The method according to claim 18 , which further comprises determining the signal strength average from respective signal strength values for the previous signal values in the sequence without the signal strength value for the current signal value, with step a) being able to be executed at least one of before and after step b).
22. The method according to claim 18 , wherein the received digital signal values are complex signals respectively including an inphase signal and a quadrature signal.
23. The method according to claim 22 , which further comprises aligning the current signal value with the signal strength average determined in step b) by dividing both the inphase signal and the quadrature signal by the signal strength average.
24. The method according to claim 22 , which further comprises determining the signal strength value representing the signal strength of the current signal value by adding a magnitude of the inphase signal and a magnitude of the quadrature signal.
25. The method according to claim 22 , which further comprises determining the signal strength value representing the signal strength of the current signal value by:
squaring the inphase signal to yield a squared inphase signal,
squaring the quadrature signal to yield a squared quadrature signal, and
adding the squared inphase signal and the squared quadrature signal.
26. The method according to claim 18 , which further comprises determining the signal strength average by adding a previous signal strength average multiplied by λ 1 and the signal strength value of the current signal value multiplied by λ 2 , where λ 1 +λ 2 =1.
27. The method according to claim 26 , wherein:
λ 1 =1−2 −n ;
λ 2 =2 −n ; and
n is a natural number.
28. The method according to claim 18 , which further comprises aligning the current signal value with the signal strength average determined in step b) only if a variation in the signal strength within the sequence exceeds a prescribed threshold.
29. The method according to claim 18 , which further comprises aligning respective current signal values in the sequence with the respective signal strength averages for the sequence only if a maximum signal strength average for the sequence and a mean signal strength average for the sequence differ to a sufficient extent.
30. The method according to claim 18 , which further comprises aligning respective current signals in the sequence with the respective signal strength averages for the sequence only if a quotient of a maximum signal strength average for the sequence and of a mean signal strength average for the sequence exceeds a prescribed threshold value.