Handling Communication Interference in Wireless Systems

• US 20070280096A1
• Filed: 04/13/2005
• Published: 12/06/2007
• Est. Priority Date: 04/15/2004
• Status: Active Grant

• Current Assignee: Sparkmotion Incorporated (Quarterhill Inc. (f/k/a Wi-LAN Inc.))
• Original Assignee: Alvarion Limited
• Inventors: Yanover, Vladimir, Kaitz, Tal, Chayat, Naftali
• Granted Patent: US 7,925,295 B2
• Time in Patent Office: Days
• US Class Current: 370/201
• CPC Class Codes: H04W 52/04 TPC

Abstract

A method and devices are provided to allow reducing interferences occurring in adjacent wireless communication networks. When a subscriber device experiences interferences resulting from the operation of an adjacent wireless network, it transmits an adjustment signal which serves as a request for adjustment, to the base station operative at the adjacent wireless communication network. The adjacent base station that receives the adjustment signal retrieves adjustment information therefrom, and based on the retrieved information will determine whether it should effect a change in its transmission that would result in reducing the interferences experienced at the subscriber device sending the adjustment signal.

Claims

1. In a first wireless network comprising at least one first base station and at least one first subscriber device, wherein interferences are experienced in communications conducted between said at least one first subscriber device and said at least one first base station and wherein said interferences result from the operation of a second wireless network comprising at least one second base station and at least one second subscriber device, a method for reducing said interferences which comprises:

transmitting from said at least first subscriber device an adjustment signal;

receiving said adjustment signal at said second base station and retrieving therefrom adjustment information;

based on the adjustment information thus retrieved, determining at said second base station whether a change in its transmissions should be effected, wherein carrying out said change would result in reducing the interferences experienced at said at least first subscriber device.

2. A method according to claim 1, wherein said adjustment information comprises information which relate to the timing of expected transmissions from said first base station to said first subscriber device.

3. A method according to claim 1, further comprising a step of carrying out an adjustment in transmissions from said second base station, based on said information retrieved.

4. A method according to claim 3, wherein in said step of carrying out an adjustment comprises effecting a change in the timing of transmissions being at a frequency which is substantially the same frequency as that in which said at least first subscriber device is operative, or effecting a change in the antenna beam directing, or effecting a change in direction of nulls in the beam pattern, or effecting a change in the power of at least the transmissions being at a frequency which is substantially the same frequency as that in which said at least first subscriber device is operative, or any combination thereof.

5. A method according to claim 1, wherein in response to the information retrieved from said adjustment signal, said at least one second base station transmits to said at least one second subscriber device a signal indicating a change to be effected in transmissions from said at least one second subscriber device to said at least one second base station, wherein carrying out said change would result in reducing the interferences affecting communication between said at least one first base station and said at least one first subscriber device.

6. A method according to claim 1, wherein said step of making a decision whether a change in its transmission should be effected, is also based upon a load of traffic to be transmitted by said at least one second base station to at least one second subscriber device associated therewith.

7. A method according to claim 1, wherein in said step of transmitting said adjustment signal comprises

transmitting an adjustment signal selected from a set of orthogonal or substantially orthogonal waveforms, where said orthogonality is in the time domain, or in the frequency domain, or in the code domain, or in any combination of any of these domains.

8. A method according to claim 1, further comprising the step of distinguishing between adjustment signals received from different subscriber devices.

9. A method according to claim 8, wherein said step of distinguishing between adjustment signals received from different subscriber devices comprises a step of using non-overlapping or partially overlapping sub-sets of waveforms, wherein said sub-sets are distinct in the time domain and/or in the frequency domain or in the code domain.

10. A method according to claim 9, wherein said step of step of using non-overlapping or partially overlapping sub-sets of waveforms comprises assigning specific sub-sets by a network management entity, or by associating a sub-set with a unique base station identifier code.

11. A method according to claim 1, wherein said adjustment signal is transmitted in an OFDM scheme.

12. A method according to claim 11, wherein said OFDM scheme is derived by cyclically extending transmitted waveforms so that propagation differences between base stations are accounted for.

13. A method according to claim 12, wherein said cyclic extension is set equal to one or several OFDM symbol durations.

14. A method according to claim 1, further comprising the step of dividing DL sub-frames transmitted by said first and second base stations into essentially synchronized slots, where each DL transmission starts at a corresponding slot boundary, and where there is a one-to one correspondence between said slots and slots allocated for the transmission of said adjustment signals.

15. A method according to claim 14, wherein said division of the DL sub-frame into slots is performed in the time domain, and/or frequency domain and or code domain and/or in any other multiplexing scheme employed by the system.

16. A method according claim 14, wherein said division of the DL sub-frame into transmission slots is carried in accordance with the type of traffic carried and the payload distribution.

17. A method according to claim 14, further comprising controlling the size of the transmission slots.

18. A method according to claim 17, wherein said transmission slots are of unequal size.

19. A method according to claim 1, wherein the step of receiving said adjustment signal at said second base station and retrieving adjustment information therefrom, comprises taking into account differences existing in propagation times between said first subscriber device and said first and second base stations, respectively.

20. A method according to claim 1, wherein said adjustment information comprises sets of contiguous or non-contiguous subcarriers occupying one or more OFDM symbols.

21. A method according to claim 20, wherein said subcarriers are modulated by pre-defined amplitude aid/or phase sequence that belongs to a pre-defined set and wherein said modulation is carried out in the frequency domain, and/or in the time domain.

22. A method according to claim 21 wherein said pre-defined set is comprised of orthogonal or nearly orthogonal sequences.

23. A method according to claim 1, further comprising a step of selecting for which subscriber device a transmission opportunity (TO) is provided for transmitting said adjustment signal.

24. A method according to claim 23, wherein said step of selecting comprises one or more of the following options:

a. at the base station, assigning a transmission opportunity for transmitting said adjustment signal, to those subscribers with low CINR, or to those subscribers to which previous DL transmissions had failed;

or

b. at the base station, assigning a transmission opportunity for transmitting said adjustment signal, to those subscribers to which a transmission opportunity were not assigned in the previous frames;

or

c. at the base station, assigning a transmission opportunity for transmitting said adjustment signal, to those subscriber devices which carry high volumes of traffic or traffic with high quality Of service requirements;

or

d. at the base station, assigning transmission opportunities to all subscriber devices provided with DL allocations.

25. A method according to claim 1, further comprising a step of making, at said at least one second subscriber device, a decision whether to transmit an adjustment signal.

26. A method according to claim 25, where said step of making a decision is based on estimating the interferences caused by that at leas t one second subscriber device to the communication held with said at least one first subscriber device.

27. A base station adapted to operate in a wireless network and comprising:

an interface operative to allow communication between said base station and a communication network associated therewith;

at least one radio transceiver operative at least one frequency and capable of transmitting communication traffic towards at least one subscriber device and receive communication traffic therefrom, and further operative to receive an adjustment signal transmitted from at least one further subscriber device associated with a different wireless network;

at least one processor adapted to;

retrieve adjustment information from said adjustment signal received;

determine whether to effect a change in transmissions from said base station and/or from any of said at least one subscriber device to enable reducing interference occurring in communications with said at least one further subscriber device, and if in the affirmative, determine the change that should be effected.

28. A base station according to claim 27, further comprising an advanced antenna system adapted to effect a change in the antenna beam-directing, in response to the determination made by said at least one processor.

29. A base station according to claim 27, further comprising a power controller to effect a change in the power of at least the transmissions being at a frequency which is substantially the same frequency as that at which said at least one subscriber device is operative, in response to the determination made by said at least one processor.

30. A base station according to claim 27, further adapted to transmit an indication signal to said at least one subscriber device in response to the information retrieved from said adjustment signal, wherein said indication signal indicates a change to be effected in transmissions from said at least one subscriber device in order to reduce interferences affecting communication between said at least one further subscriber device and a base station associated therewith.

31. A base station according to claim 27, wherein said at least one processor is further adapted to determine whether a change in said base station transmissions should be effected, based on a load of traffic to be transmitted to said at least one subscriber device.

32. A subscriber device adapted to operate in a wireless network and comprising:

an interface operative to allow communication between said subscriber device and at least one base station;

at least one radio transceiver operative at least one frequency and adapted to transmit communication traffic towards said at least one base station and receive communication traffic therefrom;

establish which of the channels carrying traffic to or from said subscriber terminal experience such interferences;

wherein said at least one radio transceiver is adapted to transmit a radio adjustment signal to be received by at least one further base station which signal characterizes the communication to and/or from said subscriber device that is subjected to interferences by communications carried between said at least one further base station and at least one further subscriber device associated therewith.

33. A subscriber terminal according to claim 32, wherein said at least one processor is further adapted to incorporate at least one marking signal indicating a frame beginning or a frame end or both.

34. A subscriber device according to claim 32, wherein said at least one processor is further adapted to determine existence of interferences caused by radio transmissions at a substantially the same or substantially adjacent frequency occurring during transmissions to or reception from said at least one base station.