Method and system for implementing outer loop power control in discontinuous transmission mode using explicit signalling

• US 6,590,874 B1
• Filed: 09/30/1999
• Issued: 07/08/2003
• Est. Priority Date: 09/30/1999
• Status: Expired due to Term

• Current Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Chheda, Ashvin, Paranchych, David, Wang, Yiping
• Primary Examiner(s): Bost, Dwayne
• Assistant Examiner(s): CONTEE, JOY KIMBERLY
• Application Number:
  US09/410,208
• Time in Patent Office: 1,377 Days
• Field of Search: 370/335, 370/342, 370/329, 370/328, 370/331, 370/332, 370/252, 370/320, 370/317, 370/318, 370/511, 455/522, 455/226.2, 455/226.3, 455/69
• US Class Current: 370/318
• CPC Class Codes: H04B 7/2637 for logical channel control
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/282 taking into account the speed of the mobile
• CPC Class Codes: H04W 52/283 Power depending on the position of the mobile
• CPC Class Codes: H04W 52/288 taking into account the usage mode, e.g. hands-free, data transmission, telephone
• CPC Class Codes: H04W 52/44 in connection with interruption of transmission

Abstract

A signalling method for controlling unnecessary power increases and call drop during discontinuous transmission (DTX) mode of a frame-based transmission system. The signalling method comprises the steps of (1) detecting, at a receiver end of the transmission system a status of a transmitted frame indicating one of two possible transmission modes including (a) when a gating-off of the traffic channel occurs, and (b) when no gating-off of traffic occurs and normal traffic is being transmitted, and (2) controlling a change in the receiver target bit energy to noise spectrum density ratio Eb/No in response to the detection step so that a receiver target Eb/No is increased only when the detecting step does not indicate a gating-off of traffic has occurred.

Claims

1. A method for controlling unnecessary power increases and call drop during discontinuous transmission (DTX) mode of a frame-based transmission system, said method comprising:

identifying one or more of a plurality of power control bits per frame as a DTX indicator recognized by a transmission protocol and logic within said system;

determining when traffic is to be gated-off in a transmission;

setting said DTX indicator to a first value, which indicates to a receiving unit when traffic in said frame is gated off, wherein the DTX indicator indicates normal traffic transmission when said DTX indicator is set to a second, different value; and

transmitting said transmission with said DTX indicator to said receiving unit;

receiving said DTX indicator at said receiving unit of said transmission system, said DTX indicator being included within a received frame and indicating whether the received frame was transmitted with normal traffic or without traffic due to a gating-off of traffic at a source unit prior to transmission of said frame; and

controlling a change in the target bit energy to noise spectrum density ratio (Eb/No) of subsequent transmissions over said transmission system based on information obtained from the reading of said DTX indicator, wherein Eb/No is not increased when said DTX indicator indicates a gating-off of traffic has occurred.

2. The method of claim 1, further comprising the steps of:

analyzing said one or more bits at said receiver; and

modifying a target Eb/No according to power control operation for normal traffic transmission when said one or more bit indicates a normal frame is being transmitted.

3. The method of claim 2, further comprising the steps of:

when said indicates that a gating-off of traffic has occurred, decoding said frame to determine whether or not there is normal traffic within the frame to reduce a possibility of error in said analyzing step;

modifying a target (Eb/No) according to power control operation for normal traffic transmission when said frame is decoded correctly;

maintaining a current target Eb/No when gating-off of normal traffic has been verified by said decoding step.

4. The method of claim 3, further including the step of:

initiating an operation to decode said frame as a normal traffic frame;

when the frame is decoded as a normal traffic frame, asserting normal power control for a subsequent transmission to a target; and

when the frame is not detected as a normal traffic frame, performing one of several power control operations from among maintaining a current target SNR and implementing an outer loop power control mechanism for receipt of a frame in which traffic has been gated-off.

5. The method of claim 1, wherein said reading step detects both on a forward and a backward transmission path.

6. The method of claim 5, wherein said reading step detects said indicator from within one of a dedicated control channel (DCCH) and a suppemenal channel (SCH).

7. The method of claim 1, wherein said identifying step includes the step of implementing a time diversity transmission to enhance reliability of said signal, wherein said time diversity transmission utilizes a first and a second bit at different time locations within said frame, and wherein the first and second bits are coherently combined to determine if the traffic has been gated off.

8. The method for claim 1, said method comprising:

reading said DTX indicator from within a frame of a received transmission, wherein said indicator includes a bit that has one of two possible values including a first value indicating that the transmission includes normal traffic and a second value indicating that normal traffic has been gated off within the transmission;

when said bit is set to said first value, modifying a power level of the target signal-to-noise ratio (SNR) according to normal traffic transmission power control mode; and

when said bit is set to said second value, modifying a power level of the target SNR according to an operating mode where normal traffic is not being transmitted within a transmission.

16. The method of claim 8, wherein a default value of said indicator bit indicates transmission of normal traffic.

17. The method of claim 8, wherein said bit is a first indicator bit and said method further comprises:

providing a second indicator bit as a back-up bit to said indicator bit, wherein a time diversity transmission is established; and

combining said first and second indicator bit at a receiving unit of said transmission;

determining whether traffic has been gated off based on a resulting combination from said combining step, wherein an occurrence of an error due to reliance on said first bit is substantially reduce and a reliability of the power control method utilizing explicit signaling is substantially improved.

9. A system for controlling unnecessary power increases and call drop during discontinuous transmission (DTX) mode of a frame-based transmission system, said system comprising:

means for identifying one or more of a plurality of power control bits per frame as a DTX indicator recognized by a transmission protocol and logic within said system;

means for determining when traffic is to be gated off in a transmission; and

means for setting said DTX indicator to a first value, which indicates to a receiving unit when traffic in said frame is gated off, wherein the DTX indicator indicates normal traffic transmission when said DTX indicator is set to a second, different value;

means for receiving said DTX indicator at said receiving unit of said transmission system, said DTX indicator being included within a received frame and indicating whether the received frame was transmitted with normal traffic or without traffic due to a gating-off of traffic at a source unit prior to transmission of said frame; and

means for controlling a change in the target bit energy to noise spectrum density ratio (Eb/No) of subsequent transmissions over said transmission system based on information obtained from the reading of said indicator, wherein Eb/No is not increased when said DTX indicator indicates a gating-off of traffic has occurred.

10. The system of claim 9, further comprising:

means for analyzing said one or more bit at said receiving unit; and

means for modifying a target Eb/No according to power control operation for normal traffic transmission when said one or more bit indicates a normal frame is being transmitted.

11. The system of claim 10, further comprising:

means, when said indicates that a gating-off of traffic has occurred, for initiating a decoding process to determine whether or not there is normal traffic within the frame to reduce a possibility of error in said analyzing step;

modifying a target (Eb/No) according to power control operation for normal traffic transmission when said frame is decoded correctly;

maintaining a current target Eb/No when gating-off of normal traffic has been verified by said decoding process.

12. The system of claim 11, further comprising means for:

means for initiating an operation to decode said frame as a normal traffic frame;

when the frame is decoded as a normal traffic frame, means for asserting normal power control for a subsequent transmission to a target; and

when the frame is not detected as a normal traffic frame, means for performing one of several power control operations from among maintaining a current target SNR and implementing an outer loop power control mechanism for receipt of a frame in which traffic has been gated-off.

13. The system of claim 9, wherein said detecting means detects both on a forward and a backward transmission path.

14. The system of claim 13, wherein said detecting means detects said signal indicating gating-off of traffic or normal traffic on one of a dedicated control channel (DCCH) and a supplemental channel (SCH).

15. The system of claim 9, wherein said identifying means includes means for implementing a time diversity transmission to enhance reliability of said signal, wherein said time diversity transmission utilizes a first and a second bit at different time locations within said frame, and wherein the first and second bits are coherently combined to determine if the traffic has been gated off.

18. A communication unit for use within a CDMA communications system, said unit comprising:

means for providing an explicit signal within a frame of a received transmission, wherein said explicit signal includes a bit that has one of two possible values including a first value indicating that the transmission includes normal traffic and a second value indicating that normal traffic has been gated off within the transmission;

when said bit is set to said first value, means for modifying a power level of the target signal-to-noise ratio (SNR) according to normal traffic transmission power control mode; and

when said bit is set to said second value, means for modifying the power level of the target SNR according to an operating mode where normal traffic is not being transmitted within a transmission.

19. The communication unit of claim 18, wherein said bit is a first bit among a plurality of bits, said communication unit further comprising:

means for providing a second bit as a back-up bit to said first bit, wherein a time diversity transmission is established;

means for combining said first and second bits at a receiving unit of said transmission; and

means for determining whether traffic has been gated off based on a resulting combination from said combining means, wherein an occurrence of an error due to reliance on said first bit is substantially reduce and a reliability of the power control method utilizing explicit signaling is substantially improved.

20. The communication unit of claim 18, further comprising:

means for identifying one or more of a plurality of power control bits per frame as a DTX indicator recognized by a transmission protocol and logic within said system;

means for determining when traffic is to be gated off in a transmission;

means for setting said DTX indicator to a first value, which indicates to a receiving unit when traffic in said frame is gated off, wherein the DTX indicator indicates normal traffic transmission when set to a second, different value; and

means for transmitting said transmission to another communication unit.

21. The communication unit of claim 20, further comprising:

when said indicates that a gating-off of traffic has occurred, verifying that said gating off has occurred by one of a plurality of methods from among;

decoding said frame to determine whether or not there is normal traffic within the frame; and

calculating a decision variable as a ratio of said SNR of said traffic and said SNR of a power control bit(PCB) and comparing the decision variable against a pre-established threshold.

22. The communication unit of claim 22, wherein said communication unit is a mobile station.

23. The communication unit of claim 22, wherein said communication unit is a base station.