Instantaneous joint transmit power control and link adaptation for RTS/CTS based channel access

• US 20020172186A1
• Filed: 04/08/2002
• Published: 11/21/2002
• Est. Priority Date: 04/09/2001
• Status: Abandoned Application

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Larsson, Peter
• Application Number:
  US10/117,128
• Publication Number:
  US 20020172186A1
• Time in Patent Office: Days
• US Class Current: 370/349
• CPC Class Codes: H04W 28/18 Negotiating wireless communication parameters
• CPC Class Codes: H04W 28/26 Resource reservation
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 52/16 Deriving transmission power values from another channel
• CPC Class Codes: H04W 52/243 taking into account interferences
• CPC Class Codes: H04W 52/46 in multi hop networks, e.g. wireless relay networks
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 52/54 Signalisation aspects of the TPC commands, e.g. frame structure
• CPC Class Codes: H04W 74/0816 with collision avoidance

Abstract

A method for closed loop link adjustment based on a Request To Send-Clear To Send (RTS-CTS) channel access scheme includes the following steps. Designating a station as an originating station. Transmitting a RTS frame with predetermined transmit power from an originating station, prior to an intended DATA transmission, sounding the channel such that reception characteristics can be evaluated at a designated receiving station. Transmitting, in response to the originating station, a CTS frame with a predetermined transmit power from the receiving station with directives of link adjustments. Transmitting a DATA frame from the originating station to the receiving station frame complying with link adjustment directives to the extent of the originating stations capabilities. And, transmitting an acknowledge (ACK) frame in response to the originating stations from the receiving station indicating result of DATA frame reception.

Claims

1. A method for closed loop link adjustment based on a Request To Send-Clear To Send (RTS-CTS) channel access scheme comprising the steps of:

designating a station as an originating station;

transmitting a RTS frame with predetermined transmit power from an originating station, prior to an intended DATA transmission, sounding the channel such that reception characteristics can be evaluated at a designated receiving station;

transmitting, in response to the originating station, a CTS frame with a predetermined transmit power from the receiving station, the CTS frame comprising link adjustment directives;

transmitting a DATA frame from the originating station to the receiving station, based on the link adjustment directives and the originating station'"'"'s capabilities;

transmitting an acknowledge (ACK) frame in response to the originating stations from the receiving station indicating a result of DATA frame reception at the receiving station.

2. The method of claim 1, wherein the link adjustment indicates a change in transmit power.

3. The method of claim 2, wherein the link adjustment is relative to the transmit power used for the RTS frame.

4. The method of claim 1, wherein the link adjustment comprises link adaptation of forward error correction and signal constellations.

5. The method of claim 1, wherein the link adjustment comprises a change in transmit power and link adaptation of forward error correction and signal constellations.

6. The method of claim 1, comprising:

the originating station evaluating reception characteristics of the CTS frame;

the originating station conveys link adjustment information in a successive DATA frame; and

the receiving station transmits a corresponding ACK frame in accordance with the link adjustment information in the successive DATA frame.

7. The method of claim 1, wherein link adjustment is performed continuously on successive and consecutive ACK and DATA frames when multiple fragments of DATA are transmitted.

8. A method for open loop group transmit power control in a wireless system, comprising:

transmitting a frame conveying transmit power information for the frame to any proximate station;

a proximate station receiving the frame and determining the path gain based on measured signal strength of the received frame and on the transmit power information conveyed in the received frame;

selecting path gains originating from a group of stations;

determining a transmit power required to reach any of the selected path gains;

selecting the minimum of a) the highest transmit power and b) allowed transmit power, wherein the allowed transmit power is determined by regulatory requirements and station transmit power capabilities; and

assigning the selected transmit power to Clear To Send (CTS) messages.

9. The method of claim 8, wherein the wireless system comprises an infrastructure-less system or Independent Basic Service Set (IBSS) and the frame is a 802.11 BEACON frame.

10. The method of claim 8, wherein the frame comprises an indication of a minimum required receive power.

11. The method of claim 10, wherein the minimum required receive power is set relative to an indicated transmit power level.

12. The method of claim 10, wherein the required transmit power is determined based on the minimum required receive power.

13. The method of claim 8, wherein the RTS transmit power setting is determined based on input parameters related only to the destination station.

14. The method of claim 8, comprising assigning the selected transmit power to Request to Send (RTS) messages.

16. The method of claim 15, wherein the wireless system is an infrastructure system or a Basic Service Set (BSS) and wherein the transmit power request is conveyed as an information element in an IEEE 802.11 management frame.

17. The method of claim 16, wherein the management frame is a beacon, probe request or generic management frame.

18. The method of claim 15, wherein the transmit power response is conveyed as an information element in an IEEE 802.11 management frame.

19. The method of claim 18, wherein the management frame is a probe request, probe response or generic management frame.

20. The method of claim 17, wherein the RTS transmit power setting is determined based on input parameters related only to the destination station.

21. The method of claim 15, comprising assigning the selected transmit power to Request To Send (RTS) messages.

15. A method for open loop group transmit power control in a wireless system, comprising the steps of:

selecting, by a first station, at least one station within a group;

transmitting a transmit power information request from a first station to the at least one selected stations;

transmitting a transmit power response in a frame, the frame comprising transmit power information for the frame, to any proximate station from the at least one selected stations in orderly manner preventing collisions;

receiving the frame and determining the path gain based on measured signal strength of the received frame and the transmit power information in the received frame;

selecting path gains originating from the group;

determining required transmit power to reach any of the selected path gains;

selecting the minimum of a) the highest transmit power and b) allowed transmit power, wherein the allowed transmit power is determined by regulatory requirements and stations transmit power capabilities; and

assigning the selected transmit power to Clear To Send (CTS) messages.

22. A method of tiered transmit power comprising:

determining a sequence of frames that must be exchanged for successful communication;

assigning different transmit power levels to ones of the frames having different topological objectives or distance objectives.

23. The method of claim 22, wherein a transmit power setting for a frame that should be received by as many stations as possible is limited by regulatory requirements and station transmit power capabilities.

24. The method of claim 22, wherein the frame that should be received by as many stations as possible is a beacon frame.

25. The method in claim 22, wherein frames destined for a set of multiple stations are transmitted with power that is a) sufficient to reach all stations within the set and b) equal to or less than a maximum power specified by regulatory requirements.

26. The method of claim 25, wherein the frames destined for a set of multiple stations are multicast data frames.

27. The method in claim 25, wherein a frame that is destined for a single station but should be overheard by multiple stations in a set is transmitted with a power that is a) sufficient to reach all stations within the set and b) equal to or less than the a maximum power specified by regulatory requirements.

28. The method in claim 27, wherein a frame destined for a single station is transmitted with a power that is a) sufficient to reach the intended station and b) equal to or less than the a maximum power specified by regulatory requirements.

30. The method in claim 29, wherein Request To Send (RTS) and Clear To Send (CTS) frames convey transmit power information.

31. The method of claim 29, comprising:

determining a maximum allowed receive power; and

determining the maximum allowed transmit power based on the determined maximum allowed receive power.

32. The method of claim 29, wherein a station defers access and enters a back off mode when the maximum instantaneous allowed transmit power has to be exceeded.

29. A method for interference mitigation based on open loop transmit power control enabling tighter medium reuse, comprising the steps of:

conveying transmit power control information for every transmitted frame in the frame by any station transmitting;

receiving the transmitted frames and determining a path gain based on measured signal strength of the received frames and transmit power information conveyed by the received frames;

determining a maximum instantaneously allowed transmit power based on all overheard frames; and

performing at least one of a) reducing transmit power, and b) reducing transmit power in combination with adjusting link rate to ensure that the maximum instantaneously allowed transmit power is not exceeded during any transmission attempt.