METHODS AND DEVICES FOR UPLINK TRANSMIT DIVERSITY

• US 20110176593A1
• Filed: 01/20/2011
• Published: 07/21/2011
• Est. Priority Date: 01/20/2010
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Bergman, Johan, HULTELL, Johan
• Granted Patent: US 8,730,922 B2
• Time in Patent Office: Days
• US Class Current: 375/224
• CPC Class Codes: H04B 7/022 Site diversity; Macro-diversity using two or more spaced independent antennas H04B7/04
• CPC Class Codes: H04B 7/0404 the mobile station comprising multiple antennas, e.g. to provide uplink diversity
• CPC Class Codes: H04B 7/0602 using antenna switching H04B7/0686 takes precedence; antenna beam directivity switching H01Q3/24
• CPC Class Codes: H04B 7/0617 for beam forming
• CPC Class Codes: H04B 7/0623 Auxiliary parameters, e.g. power control [PCB] or not acknowledged commands [NACK], used as feedback information
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme

Abstract

Methods and devices are described for use in a wireless communications system supporting uplink transmit diversity. If it is detected that a user equipment is currently in one of a predetermined set of situations, a set of restrictions associated with the detected situation is applied when the user equipment changes pre-coding weights. The set of restrictions limits how much the pre-coding weights can be changed. A user equipment in soft handover may also be restricted to only consider feedback information from a serving base station when selecting pre-coding weights. Thus it is possible to ensure that pre-coding weights are carefully selected in situations where there is a high risk for detrimental interference and/or inferior uplink/downlink performance. A network node may be configured to detect such a situation and notify the user equipment of any restrictions to be applied on the pre-coding weight selection.

Claims

1. A method for uplink transmit diversity in a user equipment of a wireless communications system, the method comprising

performing uplink transmission using a first set of pre-coding weights;

selecting an updated set of pre-coding weights for continuing the uplink transmission, wherein the selection of the updated set of pre-coding weights includes;

detecting if the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, applying a set of restrictions associated with the detected situation when selecting the updated set of pre-coding weights, wherein the set of restrictions limits an amount of change between pre-coding weights of the updated set of pre-coding weights and previous pre-coding weights applied for the uplink transmission; and

performing uplink transmission using the selected updated set of pre-coding weights.

2. The method according to claim 1, wherein the set of restrictions specifies a maximum allowed relative phase change between the pre-coding weights of the updated set of pre-coding weights and the pre-coding weights of the first set of pre-coding weights.

3. The method according to claim 1, wherein the set of restrictions specifies a maximum relative pre-coding weight phase change during a time interval.

4. The method according to claim 1, wherein the user equipment is applying switched antenna diversity for the uplink transmission and wherein the set of restrictions specifies that the user equipment is restricted from switching antenna for the uplink transmission.

5. The method according to claim 1, wherein the predetermined set of situations includes at least one or a combination of the following situations:

a situation where a serving grant of the user equipment exceeds a predetermined threshold value,

a situation where the user equipment is in a soft handover state, and

a situation where the user equipment is in a soft handover state and has received an overload indication from a non-serving cell.

6. The method according to claim 1, wherein said detection of the user equipment being in one of the predetermined set of situations includes receiving a message from a network node indicating that one of the predetermined set of situations has been detected, and wherein the set of restrictions is applied when selecting the updated set of pre-coding weights in response to the reception of the message from the network node.

7. A user equipment for use in a wireless communications system supporting uplink transmit diversity, the user equipment comprising a plurality of antennas for uplink and downlink transmission, wherein the user equipment is configured to:

perform uplink transmission using a first set of pre-coding weights;

select an updated set of pre-coding weights for continuing the uplink transmission, wherein the user equipment is configured to select the updated set of pre-coding weights by;

detecting if the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, applying a set of restrictions associated with the detected situation when selecting the updated set of pre-coding weights, wherein the set of restrictions limits an amount of change between pre-coding weights of the updated set of pre-coding weights and previous pre-coding weights applied for the uplink transmission; and

perform uplink transmission using the selected updated set of pre-coding weights.

8. The user equipment according to claim 7, wherein the set of restrictions specifies a maximum allowed relative phase change between the pre-coding weights of the updated set of pre-coding weights and the pre-coding weights of the first set of pre-coding weights.

9. The user equipment according to claim 7, wherein the set of restrictions specifies a maximum relative pre-coding weight phase change during a time interval.

10. The user equipment according to claim 7, wherein the user equipment is configured to apply switched antenna diversity for the uplink transmission and wherein the set of restrictions specifies that the user equipment is restricted from switching antenna for the uplink transmission.

11. The user equipment according to claim 7, wherein the predetermined set of situations includes at least one or a combination of the following situations:

a situation where a serving grant of the user equipment exceeds a predetermined threshold value,

a situation where the user equipment is in a soft handover state, and

a situation where the user equipment is in a soft handover state and has received an overload indication from a non-serving cell.

12. The user equipment according to claim 7, wherein the user equipment is configured to detect that the user equipment is in one of the predetermined set of situations by receiving a message from a network node indicating that one of the predetermined set of situations has been detected, and wherein the user equipment is configured to apply the set of restrictions when selecting the updated set of pre-coding weights in response to the reception of the message from the network node.

13. A method in a network node of a wireless communications system for supporting uplink transmit diversity in a user equipment of the wireless communications system, the method comprising

detecting if the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, sending a message to the user equipment to notify the user equipment to apply a set of restrictions associated with the detected situation when selecting an updated set of pre-coding weights for uplink transmission, wherein the set of restrictions limits an amount of change between pre-coding weights of the updated set of pre-coding weights and previous pre-coding weights applied for the uplink transmission.

14. The method according to claim 13, wherein the network node is a base station and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where the base station has issued a scheduled grant for the user equipment that exceeds a predetermined first threshold value,

a situation where the base station detects that the user equipment use an Enhanced Dedicated Channel—

Transport Format Combination Identifier that exceeds a predetermined second threshold value,

a situation where the base station has issued a scheduled grant for the user equipment that exceeds a predetermined third threshold value and the user equipment has reported a total Enhanced Dedicated Channel buffer status value to the base station that exceeds a predetermined fourth threshold value,

a situation where the base station detects that an uplink power headroom reported by the user equipment exceeds a predetermined fifth threshold value,

a situation where the base station detects that a channel quality information value reported by the user equipment is below a predetermined sixth threshold value, and a situation where an estimate of the inter-cell interference exceeds a predetermined seventh threshold value.

15. The method according to claim 13, wherein the network node is a radio network controller and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where it is detected that a new neighboring base station is entering a reporting range for the user equipment,

a situation where it is detected that a neighboring base station is leaving a reporting range for the user equipment,

a situation where the user equipment is to be configured in a soft handover state,

a situation where it is detected that a filtered transmit power of the user equipment exceeds a predetermined eighth threshold value for the user equipment, and

a situation where it is detected that the filtered transmit power of the user equipment is below a predetermined ninth threshold value for the user equipment.

16. A network node for use in a wireless communications system supporting uplink transmit diversity, wherein the network node is configured to detect if a user equipment of the wireless communication system is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, send a message to the user equipment to notify the user equipment to apply a set of restrictions associated with the detected situation when selecting an updated set of pre-coding weights for uplink transmission, wherein the set of restrictions limits an amount of change between pre-coding weights of the updated set of pre-coding weights and previous pre-coding weights applied for the uplink transmission.

17. The network node according to claim 16, wherein the network node is a base station and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where the base station has issued a scheduled grant for the user equipment that exceeds a predetermined first threshold value,

a situation where the base station detects that the user equipment use an Enhanced Dedicated Channel—

Transport Format Combination Identifier that exceeds a predetermined second threshold value,

a situation where the base station has issued a scheduled grant for the user equipment that exceeds a predetermined third threshold value and the user equipment has reported a total Enhanced Dedicated Channel buffer status value to the base station that exceeds a predetermined fourth threshold value,

a situation where the base station detects that an uplink power headroom reported by the user equipment exceeds a predetermined fifth threshold value,

a situation where the base station detects that a channel quality information value reported by the user equipment is below a predetermined sixth threshold value, and a situation where an estimate of the inter-cell interference exceeds a predetermined seventh threshold value.

18. The network node according to claim 16, wherein the network node is a radio network controller and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where it is detected that a new neighboring base station is entering a reporting range for the user equipment,

a situation where it is detected that a neighboring base station is leaving a reporting range for the user equipment,

a situation where the user equipment is to be configured in a soft handover state,

a situation where it is detected that a filtered transmit power of the user equipment exceeds a predetermined eighth threshold value for the user equipment, and

a situation where it is detected that the filtered transmit power of the user equipment is below a predetermined ninth threshold value for the user equipment.

19. A method for uplink transmit diversity in a user equipment of a wireless communications system, wherein the user equipment is in a soft handover state and is in communication with a serving base station and a number of non-serving base stations the method comprising

performing uplink transmission using a first set of pre-coding weights;

receiving feedback information from the serving base station and at least one of the number of non-serving base stations;

selecting an updated set of pre-coding weights for continuing the uplink transmission based on the received feedback information, wherein the selection of the updated set of pre-coding weights includes;

detecting if the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, only considering the feedback information that has been received from the serving base station when selecting the updated set of pre-coding weights; and

performing uplink transmission using the selected updated set of pre-coding weights.

20. The method according to claim 19, wherein the predetermined set of situations includes the situation when the user equipment is in the soft handover state.

21. The method according to claim 19, wherein the predetermined set of situations includes at least one or a combination of the following situations:

a situation where a scheduled grant of the user equipment exceeds a predetermined threshold value,

a situation when a predetermined relative number of negative acknowledgement indications have been received from the serving base station,

a situation when an indication of inferior uplink coverage of a High-Speed Downlink Physical Control Channel has been detected, and

a situation when a predetermined relative number of retransmissions of packets, for which the user equipment has transmitted an acknowledgement, has been received.

22. The method according to claim 19, wherein said detection of the user equipment being in one of the predetermined set of situations includes receiving a message from a network node indicating that one of the predetermined set of situations has been detected, and wherein, in response to the reception of the message from the network node, only the feedback information that has been received from the serving base station is considered when selecting the updated set of pre-coding weights.

23. A user equipment for use in a wireless communications system supporting uplink transmit diversity, the user equipment comprising a plurality of antennas for uplink and downlink transmission, wherein the user equipment is configured to, when being in a soft handover state:

communicate with a serving base station and a number of non-serving base stations,

perform uplink transmission using a first set of pre-coding weights;

receive feedback information from the serving base station and at least one of the number of non-serving base stations;

select an updated set of pre-coding weights for continuing the uplink transmission based on the received feedback information, wherein the user equipment is configured to select of the updated set of pre-coding weights by;

detecting if the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, only considering the feedback information that has been received from the serving base station when selecting the updated set of pre-coding weights; and

perform uplink transmission using the selected updated set of pre-coding weights.

24. The user equipment according to claim 23, wherein the predetermined set of situations includes the situation when the user equipment is in the soft handover state.

25. The user equipment according to claim 23, wherein the predetermined set of situations includes at least one or a combination of the following situations:

a situation where a scheduled grant of the user equipment exceeds a predetermined threshold value,

a situation when a predetermined relative number of negative acknowledgement indications have been received from the serving base station,

a situation when an indication of inferior uplink coverage of a High Speed-Downlink Physical Control Channel has been detected, and

a situation when a predetermined relative number of retransmissions of packets, for which the user equipment has transmitted an acknowledgement, have been received.

26. The user equipment according to claim 23, wherein the user equipment is configured to detect that the user equipment is in one of the predetermined set of situations by receiving a message from a network node indicating that one of the predetermined set of situations has been detected, and wherein the user equipment is configured to, in response to the reception of the message from the network node, only consider the feedback information that has been received from the serving base station when selecting the updated set of pre-coding weights.

27. A method in a network node of a wireless communications system for supporting uplink transmit diversity in a user equipment in a soft handover state, wherein the user equipment is receiving feedback information from a serving base station and a number of non-serving base stations, the method comprising detecting the user equipment is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, sending a message to the user equipment to notify the user equipment to only consider the feedback information that has been received from the serving base station when selecting an updated set of pre-coding weights for uplink transmission.

28. The method according to claim 27, wherein the network node is a base station and the predetermined set of situations includes at least one or a combination of the following situations:

a situation when an indication of inferior uplink coverage of a High-Speed Downlink Physical Control Channel has been detected,

a situation where the base station fails to detect a predetermined relative number of acknowledgement messages on the High-Speed Downlink Physical Control Channel corresponding to a number of packets that the base station has transmitted to the user equipment,

a situation where the base station has failed to detect a predetermined relative number of channel quality indicators in a number of time-slots where a channel quality indicator was expected from the user equipment,

a situation where a predetermined relative number of negative acknowledgement indications have been sent from the base station to the user equipment,

a situation where a difference between a measured High-Speed Downlink Physical Control Channel signal to interference ratio, SIR, at the base station and a predefined SIR target exceeds a predefined first threshold for a predefined time duration, and

a situation where a relative number of transmit power control, TPC, UP commands transmitted on a Fractional Dedicated Physical Channel exceeds a predefined second threshold.

29. The method according to claim 27, wherein the network node is a radio network controller and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where an indication that the user equipment has a weaker link towards the serving base station than towards one of the number of non-serving base stations is detected, and

a situation where a probability for downlink radio link control retransmission exceeds a predetermined third threshold.

30. A network node for use in a wireless communications system supporting uplink transmit diversity, wherein the network node is configured to detect if a user equipment, which is in a soft handover state and receives feedback information from a serving base station and a number of non-serving base stations, is currently in one of a predetermined set of situations, and

if the user equipment is detected to be in one of the predetermined set of situations, send a message to the user equipment to notify the user equipment to only consider the feedback information that has been received from the serving base station when selecting an updated set of pre-coding weights for uplink transmission.

31. The network node according to claim 30, wherein the network node is a base station and the predetermined set of situations includes at least one or a combination of the following situations:

a situation when an indication of inferior uplink coverage of a High-Speed Downlink Physical Control Channel has been detected,

a situation where the base station fails to detect a predetermined relative number of acknowledgement messages on the High-Speed Downlink Physical Control Channel corresponding to a number of packets that the base station has transmitted to the user equipment,

a situation where the base station has failed to detect a predetermined relative number of channel quality indicators in a number of time-slots where a channel quality indicator was expected from the user equipment, a situation where a predetermined relative number of negative acknowledgement indications have been sent from the base station to the user equipment, a situation where a difference between a measured High-Speed Downlink Physical Control Channel signal to interference ratio, SIR, at the base station and a predefined SIR target exceeds a predefined first threshold for a predefined time duration, and

a situation where a relative number of transmit power control, TPC, UP commands transmitted on a Fractional Dedicated Physical Channel exceeds a predefined second threshold.

32. The network node according to claim 30, wherein the network node is a radio network controller and the predetermined set of situations includes at least one or a combination of the following situations:

a situation where an indication that the user equipment has a weaker link towards the serving base station than towards one of the number of non-serving base stations is detected, and

a situation where a probability for downlink radio link control retransmission exceeds a predetermined third threshold.