Method of estimating a channel, and a radio system

• US 20030198201A1
• Filed: 12/27/2002
• Published: 10/23/2003
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Tiirola, Esa, Ylitalo, Juha, Kiiski, Matti
• Granted Patent: US 7,203,246 B2
• Time in Patent Office: Days
• US Class Current: 370/329
• CPC Class Codes: H04B 7/005 Control of transmission; Equalising
• CPC Class Codes: H04B 7/0408 using two or more beams, i.e. beam diversity
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0619 using feedback from receiving side feedback signaling for adaptive modulation/coding H04L1/0001
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals

Abstract

The invention relates to a method of estimating a downlink channel in a radio system, and to a radio system. The method comprises transmitting a common pilot signal and a user-specific pilot signal, of which channel estimates are formed. A channel estimate for the user-specific channel that has transmitted the user-specific pilot signal is formed of said channel estimates by selecting an appropriate scaling factor. The quality of the user-specific channel estimation and thus also the performance of the radio system are improved by means of the invention.

Claims

1. A method of estimating a downlink channel in a radio system, the method comprising the steps of:

transmitting a common pilot signal from the network part;

transmitting from the network part a user-specific pilot signal in a user-specific channel;

receiving the common pilot signal in user equipment;

receiving the user-specific pilot signal in user equipment;

generating an impulse response of the common pilot signal;

generating an impulse response of the user-specific pilot signal,

the method comprising a further step of;

generating an impulse response of a user-specific channel, based on the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal.

2. A method according to claim 1, wherein the user-specific pilot signal is transmitted by using a user-specific radiation pattern.

3. A method according to claim 1, wherein the common pilot signal is transmitted cell-specifically.

4. A method according to claim 1, wherein the common pilot signal is transmitted antenna-beam-specifically.

5. A method according to claim 1, wherein the user-specific pilot signal is transmitted by using adaptive transmission.

6. A method according to claim 1, wherein the common pilot signal is received in the user equipment by using at least two antenna elements.

7. A method according to claim 1, wherein a phase factor is generated between the common pilot signal and the pilot signal of the user-specific channel;

and

an impulse response of the user-specific channel is generated, based on the generated phase factor.

8. A method according to claim 1, wherein a quality variable of the impulse response of the common pilot signal is generated;

a quality variable of the impulse response of the user-specific pilot signal is generated; and

an impulse response of the user-specific channel is generated, based on the generated quality variables.

9. A method according to claim 1, wherein a phase factor is generated between the common pilot signal and the pilot signal of the user-specific channel;

and

an impulse response of the user-specific channel is generated as a weighted average of the impulse response of the common pilot signal and the user-specific pilot signal, where the weighting is based on the generated phase factor.

10. A method according to claim 1, wherein a quality variable of the impulse response of the common pilot signal is generated;

a quality variable of the impulse response of the user-specific pilot signal is generated; and

an impulse response of the user-specific channel is generated as a weighted average of the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal, the weighting being based on the generated quality variables.

11. A method according to claim 1, wherein in the network part a phase factor is generated between the common pilot signal and the user-specific pilot signal;

the phase factor is signalled to the user equipment; and

in the user equipment an impulse response of the user-specific channel is generated, based on the generated phase factor.

12. A method according to claim 1, wherein in the network part a signal of the user equipment is received;

in the network part a phase factor is generated between the common pilot signal and the pilot signal of the user-specific channel, based on the received signal;

the phase factor is signalled from the network part to the user equipment; and

in the user equipment an impulse response of the user-specific channel is generated, based on the generated phase factor.

13. A method according to claim 1, wherein position information on the user equipment is generated in the network part;

in the network part a phase factor is generated between the common pilot signal and the pilot signal of the user-specific channel, based on the generated position information;

the phase factor is signalled from the network part to the user equipment; and

in the user equipment an impulse response of the user-specific channel is generated, based on the generated phase factor.

14. A method according to claim 1, wherein in the user equipment a phase factor is generated between the common pilot signal and the user-specific pilot signal;

and

in the user equipment an impulse response of the user-specific channel is generated, based on the generated phase factor.

15. A method according to claim 1, wherein in the user equipment an impulse response of the user-specific channel is generated as a weighted average of the impulse response of the common pilot signal and the impulse response of the user-specific pilot, the weighting being adjusted adaptively.

16. A method according to claim 1, wherein an impulse response of the user-specific channel is generated for each multipath component separately.

17. A method according to claim 1, wherein an impulse response h of the user-specific channel is generated with formula

h=h₂+c·

h₁·

exp(jΦ

), where

h₁ is an impulse response of the common pilot signal;

h₂ is an impulse response of the user-specific pilot signal, c is a weighting coefficient; and

exp(jΦ

) is the phase factor, where Φ

is the phase difference between the common pilot signal and the user-specific pilot signal.

18. A radio system, comprising:

a network part for forming a fixed infrastructure for the radio system;

user equipment for forming a mobile infrastructure for the radio system;

the network part comprising means for transmitting a common pilot signal;

the network part comprising means for transmitting a user-specific pilot signal in a user-specific channel;

the user equipment comprising means for generating an impulse response of the common pilot channel;

the user equipment comprising means for generating an impulse response of the user-specific pilot signal;

the user equipment further comprising;

impulse response means for generating an impulse response of the user-specific channel, based on the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal.

19. A radio system according to claim 18, wherein the network part comprises means for transmitting the user-specific pilot signal by using a user-specific radiation pattern.

20. A radio system according to claim 18, wherein the network part comprises means for transmitting the common pilot cell-specifically.

21. A radio system according to claim 18, wherein the network part comprises means for transmitting the common pilot antenna-beam-specifically.

22. A radio system according to claim 18, wherein the network part comprises means for transmitting a signal adaptively.

23. A radio system according to claim 18, wherein the network part comprises means for generating a phase factor between the common pilot signal and the user-specific pilot signal.

24. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response of the user-specific channel, based on a phase factor between the common pilot signal and the user-specific pilot signal.

25. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response of the user-specific channel as a weighted average of the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal, the weighting being based on a phase factor between the common pilot signal and the user-specific pilot signal.

26. A radio system according to claim 18, wherein the means for generating an impulse response of the common pilot channel are arranged to generate a quality variable of the impulse response of the common pilot signal;

and

means for generating an impulse response of the user-specific pilot signal are arranged to generate a quality variable of the impulse response of the user-specific pilot signal.

27. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response of the user-specific channel, based on a quality variable of the impulse response of the common pilot signal and a quality variable of the impulse response of the user-specific pilot signal.

28. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response of the user-specific channel as a weighted average of the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal, the weighting being based on a quality variable of the impulse response of the common pilot signal and a quality variable of the impulse response of the user-specific pilot signal.

29. A radio system according to claim 18, wherein the network part comprises means for signalling a phase factor between the common pilot signal and the user-specific pilot signal to the user equipment.

30. A radio system according to claim 18, wherein the network part comprises means for receiving a signal of the user equipment;

and

the network part comprises means for generating a phase factor between the common pilot signal and the user-specific pilot signal, based on the received signal.

31. A radio system according to claim 18, wherein the network part comprises means for generating position information on the user equipment;

the network part comprises means for generating a phase factor between the common pilot signal and the pilot signal of the user-specific channel, based on the generated position information.

32. A radio system according to claim 18, wherein the user equipment comprises means for generating an impulse response of each multipath component separately.

33. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response h of the user-specific channel with formula

h=h₂+c·

h₁·

exp(jΦ

), where

h₁ is an impulse response of the common pilot signal;

h₂ is an impulse response of the user-specific pilot signal,

c is a weighting coefficient; and

exp(jΦ

) is the phase factor, where Φ

is the phase difference between the common pilot signal and the user-specific pilot signal.

34. A radio system according to claim 18, wherein the impulse response means are arranged to generate an impulse response of the user-specific channel as a weighted average of the impulse response of the common pilot signal and the impulse response of the user-specific pilot signal, the weighting taking place adaptively.