Synchronous two-phase rate and power control in WLANs

• US 8,134,958 B2
• Filed: 08/26/2008
• Issued: 03/13/2012
• Est. Priority Date: 10/08/2007
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Laboratories America Inc (NEC Corporation)
• Inventors: Kokku, Ravindranath, Ramachandran, Kishore
• Primary Examiner(s): GREY, CHRISTOPHER P
• Application Number:
  US12/198,535
• Publication Number:
  US 20090092088A1
• Time in Patent Office: 1,295 Days
• Field of Search: 370/328, 370/329, 370/330, 370/341, 370/503, 455/13.4, 455/127.1, 455/230, 455/231, 455/232.1, 455/502, 455/522
• US Class Current: 370/328
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 52/146 Uplink power control
• CPC Class Codes: H04W 52/36 with a discrete range or set of values, e.g. step size, ramping or offsets
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment

Abstract

A method for operation of a node operating in a wireless network comprising the steps of during an initial phase, setting transmission power and data transmission rate to initial settings and transmitting the initial settings to the wireless network in order to initiate communication with said wireless network during a reference phase once communication with the wireless network is established by the initial phase, transmitting at maximum power while performing a rate adaptation and at least one variable estimation and during an operational phase, transmitting at a power level that is optimal for transmission based on information obtained from the reference phase.

Claims

1. A method for operation of a node operating in a wireless network comprising the steps of:

in a synchronized manner with all other nodes in said wireless network, periodically alternating between a reference phase and an operational phase;

during the reference phase, once communication with the wireless network is established by the initial phase, transmitting at maximum power while performing a rate adaptation and variable estimation to infer said wireless network'"'"'s interference characteristics at both sender and receiver;

interference at the sender being estimated using an average transmission time ETT and interference at the receiver being estimated using a utility of medium reservation RTSUtil, with a determination of ETT being related to ETT*phi2+TT*(1−

phi2), with TT being a current transmission time and phi2 being a configurable constant;

RTSUtil being set to 1 if pRTS<

(pTotal+α

) otherwise RTSUtil being set to 0, with pRTS being packet loss rate with medium reservation, pTotal being total packet loss rate, with or without medium reservation, and α

being a configurable constant; and

during the operational phase, transmitting at a power level that is optimal for transmission based on information obtained from the reference phase.

2. The method of claim 1, further comprising the step of, during the reference phase:

estimating an optimal data transmission rate achievable at maximum transmit power and maintaining an average transmission rate used in the reference phase based on RateR being related to RateR*phi1+R*(1−

phi1), with RateR being an average rate used in the reference phase, R being a current instantaneous rate being used in the reference phase and phi1 being a configurable constant;

estimating potential receiver side interference using utility of medium reservation in the reference phase RTSUtilR;

RTSUtilR being 1 if pRTSRef<

(pTotalRef+α

) in the last X out of Y rate adaptation intervals otherwise RTSUtilR being 0, with pRTSRef being a packet loss rate with medium reservation in the reference phase, pTotalRef being a total packet loss rate, with or without medium reservation, in the reference phase and α

being a configurable constant;

estimating potential sender-side interference using expected transmission time of a packet from the transmitter to the receiver based on ETTR being related to ETTR*phi2+TT*(1−

phi2) with ETTR being an average transmission time in the reference phase, TT being a current transmission time in the reference phase and phi2 being a configurable constant; and

communicating information responsive to said RateR, RTSUtilR, and ETTR to the operational phase.

3. The method of claim 1, further comprises the steps of, during the operational phase:

performing rate adaptation and maintaining the average transmission rate used in the operational phase based on RateO being related to RateO*β

+R*(1−

β

), with RateO being an average rate used in the operational phase, R being a current instantaneous rate used in the operational phase and β

being a configurable constant; and

estimating variables for detecting the problems of undesirable rate adaptation by comparing RateR and RateO, receiver side interference by comparing RTSUtilR and RTSUtilO, and channel access asymmetry by comparing ETTR and ETTO introduced by power control; and

operating at a transmission power level optimal for avoiding problems of undesirable rate adaptation, receiver side interference and channel access asymmetry based on reference information generated during the reference phase.

4. The method of claim 3, wherein the step of estimating variables, further comprises the steps of:

estimating an optimal data transmission rate achievable at optimal transmit power during operation,

estimating potential receiver side interference using utility of medium reservation in the operational phase (RTSUtilO);

RTSUtilO being 1 if pRTSOpr<

(pTotalOpr+γ

) in the last X out of Y rate adaptation intervals otherwise RTSUtilO being 0, with pRTSOpr being a packet loss rate with medium reservation in the operational phase, pTotalOpr being a total packet loss rate, with or without medium reservation, in the operational phase, and γ

being a configurable constant; and

estimating potential sender-side interference using expected transmission time of a packet from the transmitter to the receiver based on ETTO being related to ETTO*ε

+TT*(1−

ε

) with ETTO being an average transmission time in the operational phase, TT being a current transmission time in the operational phase, and ε

being a configurable constant.

5. A non-transitory computer readable medium having stored thereon a plurality of program instructions, the plurality of program instructions including instructions which, when executed by a processor, cause the processor to perform the steps of a method for operation of a node operating in a wireless network comprising:

in a synchronized manner with all other nodes in said wireless network, periodically alternating between a reference phase and an operational phase;

during the reference phase, once communication with the wireless network is established by the initial phase, transmitting at maximum power while performing a rate adaptation and variable estimation to infer said wireless network'"'"'s interference characteristics at both sender and receiver;

interference at the sender being estimated using an average transmission time ETT and interference at the receiver being estimated using a utility of medium reservation RTSUtil), with a determination of ETT being related to ETT=ETT*phi2+TT*(1−

phi2), with TT being a current transmission time and phi2 being a configurable constant;

RTSUtil being set to 1 if pRTS<

(pTotal+α

) otherwise RTSUtil being set to 0, with pRTS being packet loss rate with medium reservation, pTotal being total packet loss rate, with or without medium reservation, and α

being a configurable constant; and

during the operational phase, transmitting at a power level that is optimal for transmission based on information obtained from the reference phase.

6. The non-transitory computer readable medium of claim 5, further comprising program instructions which cause the processor to perform the steps of, during the reference phase:

estimating an optimal data transmission rate achievable at maximum transmit power and maintaining an average transmission rate used in the reference phase based on RateR being related to RateR*phi1+R*(1−

phi1), with RateR being an average rate used in the reference phase, R being a current instantaneous rate being used in the reference phase and phi1 being a configurable constant;

estimating potential receiver side interference using utility of medium reservation in the reference phase RTSUtilR;

RTSUtilR being 1 if pRTSRef<

(pTotalRef+α

) in the last X out of Y rate adaptation intervals otherwise RTSUtilR being 0, with pRTSRef being a packet loss rate with medium reservation in the reference phase, pTotalRef being a total packet loss rate, with or without medium reservation, in the reference phase and α

being a configurable constant;

estimating potential sender-side interference using expected transmission time of a packet from the transmitter to the receiver based on ETTR being related to ETTR*phi2+TT*(1−

phi2), with ETTR being an average transmission time in the reference phase, TT being a current transmission time in the reference phase and phi2 being a configurable constant; and

communicating information responsive to said RateR, RTSUtilR, and ETTR to the operational phase.

7. The non-transitory computer readable medium of claim 5, further comprises program instructions which cause the processor to perform the steps of, during the operational phase:

performing rate adaptation and maintaining the average transmission rate used in the operational phase based on RateO being related to RateO*β

+R*(1−

β

), with RateO being an average rate used in the operational phase, R being a current instantaneous rate used in the operational phase and β

being a configurable constant; and

estimating variables for detecting the problems of undesirable rate adaptation by comparing RateR and RateO, receiver side interference by comparing RTSUtilR and RTSUtilO, and channel access asymmetry by comparing ETTR and ETTO introduced by power control; and

operating at a transmission power level optimal for avoiding problems of undesirable rate adaptation, receiver side interference and channel access asymmetry based on reference information generated during the reference phase.

8. The non-transitory computer readable medium of claim 7, wherein the program instructions causing the processor to estimate variables further comprises program instructions which cause the processor to perform the steps of:

estimating an optimal data transmission rate achievable at optimal transmit power during operation,

estimating potential receiver side interference using utility of medium reservation in the operational phase (RTSUtilO);

RTSUtilO being 1 if pRTSOpr<

(pTotalOpr+γ

) in the last X out of Y rate adaptation intervals otherwise RTSUtilO being 0, with pRTSOpr being a packet loss rate with medium reservation in the operational phase, pTotalOpr being a total packet loss rate, with or without medium reservation, in the operational phase, and γ

being a configurable constant; and

estimating potential sender-side interference using expected transmission time of a packet from the transmitter to the receiver based on ETTO being related to ETTO*ε

+TT*(1−

ε

) with ETTO being an average transmission time in the operational phase, TT being a current transmission time in the operational phase, and ε

being a configurable constant.