Receiver, transmitter, communication system, and method of communication

• US 20030123530A1
• Filed: 12/27/2002
• Published: 07/03/2003
• Est. Priority Date: 12/28/2001
• Status: Active Grant

• Current Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Original Assignee: NTT Docomo Incorporated (Nippon Telegraph and Telephone Corporation)
• Inventors: Abeta, Sadayuki, Maeda, Noriyuki, Sawahashi, Mamoru, Atarashi, Hiroyuki
• Granted Patent: US 7,092,431 B2
• Time in Patent Office: Days
• US Class Current: 375/148
• CPC Class Codes: H04B 7/0842 Weighted combining

Abstract

A receiver, comprising a plurality of antennas configured to receive signals that are obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels, the data symbol being transmitted over a plurality of sub-carriers having different frequencies; a spreading code multiplier configured to multiply reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals; a weight controller configured to adjust antenna weights by which a reception signal received by each antenna is to be multiplied, and sub-carrier weights by which a reception signal received over each sub-carrier is to be multiplied; a weight multiplier configured to multiply the reception signals by the antenna weights and the sub-carrier weights adjusted by the weight controller; and a combining unit configured to combine the reception signals multiplied by the antenna weights and the sub-carrier weights at the weight multiplier among the antennas and over spreading code duration of the spreading codes.

Claims

1. A receiver, comprising:

a plurality of antennas configured to receive signals that are obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels, the data symbol being transmitted over a plurality of sub-carriers having different frequencies;

a spreading code multiplier configured to multiply reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals;

a weight controller configured to adjust antenna weights by which a reception signal received by each antenna is to be multiplied, and sub-carrier weights by which a reception signal received over each sub-carrier is to be multiplied;

a weight multiplier configured to multiply the reception signals by the antenna weights and the sub-carrier weights adjusted by the weight controller; and

a combining unit configured to combine the reception signals multiplied by the antenna weights and the sub-carrier weights at the weight multiplier among the antennas and over spreading code duration of the spreading codes.

2. The receiver according to claim 1, wherein the weight controller adjusts the antenna weights and the sub-carrier weights such that the spreading codes for the plurality of data channels are orthogonal to each other.

3. The receiver according to claim 1, wherein the weight controller adjusts the antenna weights and the sub-carrier weights such that the spreading codes for the plurality of data channels are orthogonal to each other and a great signal to noise power ratio is achieved as possible.

4. The receiver according to claim 1, wherein

the weight controller adjusts the antenna weights and the sub-carrier weights to determine the antenna weights and the sub-carrier weights separately;

the weight multiplier comprises an antenna weight multiplier configured to multiply a reception signal of each of the antennas by the antenna weights, and a sub-carrier weight multiplier configured to multiply a reception signal on each of the sub-carriers by the sub-carrier weights; and

the combining unit comprises an antenna signal combining unit configured to combine the reception signals multiplied by the antenna weights among the antennas, and a symbol combining unit configured to combine the reception signals multiplied by the sub-carrier weights over the spreading code duration.

5. The receiver according to claim 1, wherein

the weight controller adjusts the antenna weights and the sub-carrier weights to determine collective weights by which the reception signals are to be collectively multiplied;

the weight multiplier multiplies a reception signal on each of the sub-carriers of each of the antennas by the collective weight; and

the combining unit collectively combines the reception signals multiplied by the collective weight among the antennas over the spreading code duration.

6. The receiver according to claim 1, further comprising a judging unit configured to control an order of multiplying a reception signal on each of the sub-carriers that has been multiplied using the spreading codes by the sub-carrier weights, combining the reception signal on each of the sub-carriers over the spreading code duration, multiplying a reception signal of each of the antennas by the antenna weights, and combining the reception signal of each of the antennas among the antennas,

wherein the weight multiplier and the combining unit perform despreading and antenna diversity combining under a control of the judging unit.

7. The receiver according to claim 6, further comprising a measuring unit configured to measure a condition of the reception signals received by the plurality of antennas,

wherein the judging unit controls an order in which the despreading and the antenna diversity combining are performed based on the condition of the reception signals measured by the measuring unit.

8. The receiver according to claim 4, wherein

the sub-carrier weight multiplier multiplies the reception signal on each of the sub-carriers that has been multiplied using the spreading codes by the sub-carrier weights after the antenna weight multiplier multiplies the reception signal of each of the antennas by the antenna weights and the antenna signal combining unit performs antenna diversity combining by combining the reception signals among the antennas;

and the symbol combining unit performs despreading by combining the reception signals, which have been multiplied by the sub-carrier weights over the spreading code duration after the antenna diversity combining is performed.

9. The receiver according to claim 8, wherein:

the antenna weight multiplier multiplies the reception signal of each of the antennas by the antenna weights before the reception signals are demultiplexed into the reception signal on each of the sub-carriers; and

the antenna signal combining unit combines the reception signals multiplied by the antenna weights among the antennas before the reception signals are demultiplexed into the reception signal on each of the sub-carriers.

10. The receiver according to claim 4, wherein

the antenna weight multiplier multiplies the reception signal of each of the antennas by the antenna weights after despreading in which the spreading code multiplier multiplies the reception signals using the spreading codes for the data channels corresponding to the reception signals, the sub-carrier weight multiplier multiplies the reception signal on each of the sub-carriers by the sub-carrier weights, and the symbol combining unit combines the reception signals multiplied by the sub-carrier weights over the spreading code duration;

and

the antenna signal combining unit performs antenna diversity combining by combining the reception signals multiplied by the antenna weights among the antennas after the despreading is performed.

11. The receiver according to claim 10, wherein the weight controller determines the antenna weights based on the reception signal which has been combined by the symbol combining unit over the spreading code duration.

12. The receiver according to claim 1, further comprising a propagation path state estimator configured to estimate a propagation path state in which transmitted signals have been propagated, wherein the weight controller adjusts the antenna weights and the sub-carrier weights based on an estimated value of the propagation path state estimated by the propagation path state estimator.

13. The receiver according to claim 1, further comprising an interference state estimating unit configured to estimate an interference state between the reception signals, wherein the weight controller adjusts the antenna weights and the sub-carrier weights based on an estimated value of the interference state estimated by the interference state estimating unit.

14. The receiver according to claim 1, further comprising a reception quality measuring unit configured to measure a reception quality of data symbols recovered from the reception signals, wherein the weight controller adjusts the antenna weights and the sub-carrier weights based on a measured value of the reception quality measured by the reception quality measuring unit.

15. The receiver according to claim 1, further comprising an adding unit configured to add the reception signal on each of the sub-carriers and averaging them in a direction of a frequency or a direction of a time axis.

16. A transmitter, comprising:

a divider configured to divide a data symbol transmitted over a plurality of data channels into a plurality of data symbols;

a symbol copier configured to copy the plurality of data symbols divided by the divider in a quantity equal to a number of spreading code duration of spreading codes corresponding to the data channels over which the data symbols are transmitted;

a spreading code multiplier configured to multiply the data symbols copied by the symbol copier using the spreading codes corresponding to the data channels over which the data symbols are transmitted to provide data signals;

a spreading unit configured to spread the data signals multiplied using the spreading codes at the spreading code multiplier over a plurality of sub-carriers having different frequencies for transmitting the data signals; and

a guard interval inserting unit configured to insert a guard interval in each of the data signals spread over the plurality of sub-carriers by the spreading unit to prevent interference between the data signals.

17. The transmitter according to claim 16, further comprising a pilot symbol inserting unit configured to insert a pilot symbol into the data symbols, an amplitude and phase of the pilot symbol being known to a receiver that receives the data signals.

18. The transmitter according to claim 17, wherein the pilot symbol inserting unit comprises:

a propagation path variation estimating pilot symbol inserting unit configured to insert the pilot symbol for estimating a propagation path variation used by the receiver for estimating a propagation path variation of the data signals into the data symbols; and

a weight updating pilot symbol inserting unit configured to insert the pilot symbol for updating a weight used by the receiver for estimating an error between data signals after despreading received by the receiver and the data signals transmitted by the transmitter into the data symbols.

19. A communication system, comprising:

a transmitter configured to transmit signals obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels using a plurality of sub-carriers having different frequencies; and

a receiver comprising a plurality of antennas configured to receive the signals transmitted by the transmitter, a spreading code multiplier configured to multiply reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals, a weight controller configured to adjust antenna weights by which the signal received by each antenna is multiplied, and sub-carrier weights by which a signal received over each sub-carrier is multiplied, a weight multiplier configured to multiply the reception signals by the antenna weights and the sub-carrier weights adjusted by the weight controller; and

a combining unit configured to combine the reception signals multiplied by the antenna weight and the sub-carrier weight at the weight multiplier among the antennas and over spreading code duration of the spreading codes.

20. A method of communication, comprising receiving signals obtained by multiplying a plurality of data symbols transmitted over a plurality of data channels using spreading codes for each of the data channels and transmitted over a plurality of sub-carriers having different frequencies by a plurality of antennas of a receiver;

multiplying reception signals received by the plurality of antennas using spreading codes for the data channels corresponding to the reception signals at the receiver;

adjusting an antenna weights by which a signal received by each antenna is to be multiplied and a sub-carrier weights by which a signal received over each sub-carrier is to be multiplied;

multiplying the reception signals by the antenna weights and the sub-carrier weights adjusted by the adjusting step; and

combining the reception signals multiplied by the antenna weights and the sub-carrier weight among the antennas and over spreading code duration of the spreading codes.

21. The method of communication according to claim 20, wherein the receiver adjusts the antenna weights and the sub-carrier weights such that the spreading codes for the plurality of data channels are orthogonal to each other in adjusting the antenna weights and the sub-carrier weights.

22. The method of communication according to claim 20, wherein the receiver adjusts the antenna weights and the sub-carrier weights such that the spreading codes for the plurality of data channels are orthogonal to each other and such that a great signal to noise power ratio is achieved as possible in adjusting the antenna weights and sub-carrier weights.

23. The method of communication according to claim 20, wherein the receiver adjusts the antenna weights and the sub-carrier weights to determine the antenna weights and the sub-carrier weights separately;

multiplies a reception signal of each of the antennas by the antenna weights, and combines the reception signals among the antennas; and

multiplies a reception signal on each of the sub-carriers by the sub-carrier weights, and combines the reception signals over the spreading code duration.

24. The method of communication according to claim 20, wherein

the receiver adjusts the antenna weights and the sub-carrier weights to determine a collective weight by which the reception signals are to be collectively multiplied;

multiplies a reception signal on each of the sub-carriers of each of the antennas by the collective weights; and

collectively combines the reception signals multiplied by the collective weight among the antennas over the spreading code duration.

25. The method of communication according to claim 20, wherein

the receiver controls an order of multiplying a reception signal on each of the sub-carriers that has been multiplied using the spreading code by the sub-carrier weight, combining the reception signal on each of the sub-carriers over the spreading code duration, multiplying a reception signal on each of the antennas by the antenna weight, and combining the reception signal of each of the antennas among the antennas;

and

performs despreading and antenna diversity under a control.

26. The method of communication according to claim 25, wherein the receiver measures a condition of the reception signals received by the plurality of antennas, and controls an order in which the despreading and the antenna diversity combining are performed based on the condition of the reception signals.

27. The method of communication according to claim 23, wherein the receiver multiplies the reception signal on each of the sub-carriers that has been multiplied using the spreading code by the sub-carrier weights;

and

performs despreading by combining reception signals, which have been multiplied by the sub-carrier weights over the spreading code duration, after multiplies the reception signal on each of the sub-carriers by the antenna weights and performs antenna diversity combining by combining the reception signals which have been multiplied by the antenna weights among the antennas.

28. The method of communication according to claim 27, wherein the receiver multiplies the reception signal of each of the antennas by the antenna weights before the reception signals are demultiplexed into the reception signal on each of the sub-carriers;

and

combines the reception signals multiplied by the antenna weights among the antennas before the reception signals are demultiplexed into a reception signal on each of the sub-carriers.

29. The method of communication according to claim 23, wherein the receiver multiplies the reception signal of each of the antennas by the antenna weights;

and

performs antenna diversity combining by combining the reception signals multiplied by the antenna weights among the antennas, after performs despreading by multiplying the reception signals using the spreading codes for the data channels corresponding to the reception signals, multiplying the reception signal on each of the sub-carriers by the sub-carrier weights, and combining the reception signals multiplied by the sub-carrier weights over the spreading code duration.

30. The method of communication according to claim 29, wherein the receiver determines the antenna weights based on the reception signal, which has been combined over the spreading code duration.

31. The method of communication according to claim 27, wherein the receiver determines whether to maintain a state of the reception signals multiplied by the antenna weights or to adjust the state of the reception signals multiplied by the antenna weights again, based on the antenna weights by which the reception signals are multiplied, and adjusts the sub-carrier weights based on a result of determination.

32. The method of communication according to claim 27, wherein the receiver determines the antenna weights by using an equal gain combining method and determines the sub-carrier weights by using a minimum mean square error combining method or an equal gain combining method.

33. The method of communication according to claim 29, wherein the receiver determines whether to maintain a state of the reception signals multiplied by the sub-carrier weights or to adjust the state of the reception signals multiplied by the sub-carrier weights again, based on the sub-carrier weight by which the reception signals are multiplied, and adjusts the antenna weights based on a result of determination.

34. The method of communication according to claim 29, wherein the receiver determines the sub-carrier weights by using a minimum mean square error combining method and determines the antenna weights by using an equal gain combining method.

35. The method of communication according to claim 20, wherein the receiver estimates a propagation path state in which a transmitted signals have been propagated, and adjusts the antenna weights and the sub-carrier weights based on an estimated value of the propagation path state estimated.

36. The method of communication according to claim 35, wherein the receiver compares a threshold value of the propagation path state to be used as a criterion for an adjustment of the antenna weights and the sub-carrier weights with the estimated value of the propagation path state, and adjusts the antenna weights and the sub-carrier weight based on a result of comparison.

37. The method of communication according to claim 20, wherein the receiver estimates an interference state of the reception signals and adjusts the antenna weights and the sub-carrier weights based on an estimated value of the interference state.

38. The method of communication according to claim 37, wherein the receiver compares a threshold value for difference of the interference state between the antennas to be used as a criterion for an adjustment of the antenna weights and the sub-carrier weight with difference of the estimated value of the interference state between the antennas, and adjusts the antenna weight and the sub-carrier weight based on a result of comparison.

39. The method of communication according to claim 20, wherein the receiver measures a reception quality of data symbols recovered from the reception signals, and adjusts the antenna weights and the sub-carrier weights based on a measured value of the reception quality.

40. The method of communication according to claim 39, wherein the receiver compares a threshold value of a variation of the reception quality to be used as a criterion for an adjustment of the antenna weight and the sub-carrier weight with a variation of the measured value of the reception quality, and adjusts the antenna weight and the sub-carrier weights based on a result of comparison.