Abstract:
A method, system, and medium are provided for controlling power usage in a wireless telecommunications network, the method comprising transmitting a pilot signal to a mobile station over a wireless channel, receiving a response that includes a signal-to-interference-and-noise associated with said pilot signal, determining an instantaneous channel rate to be used for a subsequent data transmission to said mobile station based at least on said signal-to-interference-and-noise, selecting a transmit power level for said data transmission; and transmitting data to said mobile station at said channel rate and said power level.

Description:
SUMMARY 
     Embodiments of the invention are defined by the claims below, not this summary. A high-level overview of various aspects of the invention are provided here for that reason, to provide an overview of the disclosure, and to introduce a selection of concepts that are further described below in the detailed-description section. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used as an aid in isolation to determine the scope of the claimed subject matter. 
     At a high level, ways of controlling power usage in a wireless telecommunications network are provided. In one aspect, a wireless telecommunications base transceiver station performs a method of controlling power usage in a wireless telecommunications network. In one embodiment of this method, the transmit power for the base transceiver station is minimized consistent with maintaining acceptable forward error rates. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Illustrative embodiments of the present invention are described in detail below with reference to the attached drawing figures, and wherein: 
         FIG. 1  depicts a block diagram of an exemplary system in accordance with one embodiment of the present invention; 
         FIG. 2  depicts an illustrative data flow diagram that shows data flowing in accordance with one embodiment of the present invention; 
         FIG. 3  depicts an illustrative data flow diagram showing the effects of a wireless packet drop in the case that the BTS has a full transmit queue; 
         FIG. 4  depicts an illustrative data flow diagram showing the effects of a wireless packet drop in the case that the BTS has an empty transmit queue; 
         FIGS. 5A-5H  depict transmit queues with various amounts of data in them and various transmit power level thresholds; and 
         FIG. 6  depicts a flow diagram of an exemplary method in accordance with one embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The subject matter of embodiments of the present invention is described with specificity herein to meet statutory requirements. But the description itself is not intended to necessarily limit the scope of claims. Rather, the claimed subject matter might be embodied in other ways to include different steps or combinations of steps similar to the ones described in this document, in conjunction with other present or future technologies. Terms should not be interpreted as implying any particular order among or between various steps herein disclosed unless and except when the order of individual steps is explicitly described. 
     Throughout this disclosure, several acronyms and shorthand notations are used to aid the understanding of certain concepts pertaining to the associated system and services. These acronyms and shorthand notations are intended to help provide an easy methodology of communicating the ideas expressed herein and are not meant to limit the scope of the present invention. The following is a list of these acronyms: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 BTS 
                 Base Transceiver Station 
               
               
                   
                 CDMA  
                 Code Division Multiple Access 
               
               
                   
                 EVDO 
                 EVolution-Data Optimized 
               
               
                   
                 FER 
                 Frame Error Rate 
               
               
                   
                 GSM 
                 Global System for Mobile (Groupe Spécial Mobile) 
               
               
                   
                 HSDPA 
                 High-Speed Downlink Packet Access 
               
               
                   
                 IP 
                 Internet Protocol 
               
               
                   
                 LTE 
                 Long-Term Evolution 
               
               
                   
                 SINR 
                 Signal-to-Interference-and-Noise Ratio 
               
               
                   
                 TCP 
                 Transmission Control Protocol 
               
               
                   
                   
               
             
          
         
       
     
     Further, various technical terms are used throughout this description. An illustrative resource that fleshes out various aspects of these terms can be found in Newton&#39;s Telecom Dictionary by H. Newton, 24th Edition (2008). 
     Embodiments of the present invention may be embodied as, among other things: a method, system, or set of instructions embodied on one or more computer-readable media. Computer-readable media include both volatile and nonvolatile media, removable and nonremovable media, and contemplate media readable by a database, a switch, and various other network devices. By way of example, and not limitation, computer-readable media include media implemented in any method or technology for storing information. Examples of stored information include computer-useable instructions, data structures, program modules, and other data representations. Media examples include, but are not limited to information-delivery media, RAM, ROM, EEPROM, flash memory or other memory technology, CD-ROM, digital versatile discs (DVD), holographic media or other optical disc storage, magnetic cassettes, magnetic tape, magnetic disk storage, and other magnetic storage devices. These technologies can store data momentarily, temporarily, or permanently. 
     Turning now to  FIG. 1 , a block diagram of an exemplary system in accordance with one embodiment of the present invention is presented. A first mobile device  102  communicates with a content provider  104  via a BTS  106  and the Internet  108 . In one embodiment, mobile device  102  takes the form of a smartphone; in another embodiment, it takes the form of a laptop computer. Other embodiments are possible without departing from the scope of the claims below. Content provided by content provider  104  can take the form of web pages, email services, and other IP data services. BTS  106  communicates wirelessly with mobile device  102 , and maintains a queue  110  of data to transmit wirelessly to mobile device  102 . In one embodiment, data in queue  120  may take the form of IP packets containing TCP packets, UDP packets, or other transport-layer protocols. In another embodiment, another network-layer protocol is used; in a third embodiment, no network layer protocol is used, and the transport layer is sent directly. In one embodiment, mobile device  102  and BTS  110  communicate via CDMA; other embodiments include EVDO, GSM, HSPDA, LTE, WiFi, and WiMax. This list is intended to be illustrative rather than exhaustive and other wireless protocols are possible without departing from the scope of the claims below. 
     Similarly, a second mobile device  112  communicates with a second content provider  114  via BTS  116  and Internet  108 , and BTS  116  maintains a queue  118  of data to transmit wirelessly to mobile device  112 . Mobile device  112  may take the same form as mobile device  102 , or a different form; similarly, the type of data sent, the network, transport, and wireless protocols may be the same as those used by mobile device  102  or different. 
     The maximum rate of data communication between mobile device  102  and BTS  106  is dependent on the signal-to-interference-and-noise ratio (SINR) of the wireless channel in use, as is the maximum rate of data communication between mobile device  112  and BTS  116 . Thus, BTS  106  could increase the data rate of its communication with mobile device  102  by transmitting at increased power, thus increasing the “signal” portion of the SINR. However, increasing transmit power in the channel between mobile device  102  and BTS  106  also increases the “interference” portion of the SINR of the channel between mobile device  112  and BTS  116 . Thus the optimal data rates for the entire network occur when each BTS transmits at the minimum power necessary to achieve the necessary SINR for a given data rate. However, this power is dependent on the power of all other BTSs transmitting within interference range as well as noise from outside the system and thus cannot be determined accurately in advance. Therefore, some data packets are lost regardless of the transmit power level used; present systems attempt to minimize this loss by choosing a single, fixed transmit power level for each communication with a given mobile device, targeted at an acceptably small FER for a given data rate. 
     Turning now to  FIG. 2 , a data flow diagram showing data flowing in accordance with the present invention. BTS  202  has a queue  204  of data to transmit to mobile device  206 . BTS  202  corresponds to BTS  106 , queue  204  corresponds to queue  110 , and mobile device  206  corresponds to mobile device  102 . At step  208 , BTS  202  transmits a pilot signal  210  to mobile device  206 . In one embodiment, pilot signal  210  is transmitted at full power. At step  212 , mobile device  206 , having received pilot signal  210 , transmits a reply  214  to BTS  202  that includes the SINR associated with its reception of pilot signal  210 . 
     At step  216 , BTS  202 , having received reply  214 , determines the data rate for subsequent transmissions. In one embodiment, this data rate is chosen to be the highest data rate the reported SINR will support. A plurality of transmit power levels are then determined, and one is selected. In one embodiment, this plurality is two distinct power levels; in another embodiment, the plurality is three distinct power levels. Other numbers of power levels are possible without departing from the scope of the claims below. Each of these distinct power levels is associated with a queue length threshold  218 . In one embodiment, higher power levels are associated with shorter lengths of queue  204 ; the lowest power level associated with a threshold below the current length of queue  204  is then selected. 
     At step  220 , one or more packets  222  are transmitted at the selected power level. This step continues until the length of queue  204  crosses a threshold such as threshold  218 . At step  224 , BTS  202  determines that the length of queue  204  has dropped below threshold  218  and chooses a new power level. In one embodiment, the lowest power level associated with a threshold below the new length of queue  204  is selected. At step  226 , one or more packets  228  are transmitted at this new power level. In one embodiment, this process of sending packets, and adjusting the transmit power level whenever the current queue length crosses a threshold such as threshold  218  is repeated until no more data remains to be sent from BTS  202  to mobile device  206 . 
     Turning now to  FIG. 3 , an illustrative data flow diagram showing the effects of a wireless packet being lost in the course of transmission from a BTS  302  with transmit queue  304  to a mobile device  306  in the case that transmit queue  304  is long is presented. BTS  302  corresponds to BTS  202 , transmit queue  304  corresponds to transmit queue  202 , and mobile device  306  corresponds to mobile device  206 . The transmission process initially proceeds as in  FIG. 2 . 
     At step  308 , however, BTS  302  transmits a packet  310 , which is not correctly received by mobile device  306 . This loss is not detected until an interval  312  has elapsed; however, since queue  304  is long, one or more packets  314  making up the remainder of the data to be transmitted can be sent at step  316  before the loss of packet  310  has been detected. After interval  312  has elapsed, the loss of packet  310  is detected and a retransmission  318  of packet  310  occurs at step  320 . During this time, the queue is non-empty and hence the BTS is able to continuously transmit packets, thereby maintaining application throughput at a high level. 
     Turning now to  FIG. 4 , an illustrative data flow diagram showing the effects of a wireless packet being lost in the course of transmission from a BTS  402  with transmit queue  404  to a mobile device  406  in the case that transmit queue  404  is empty is presented. BTS  402  corresponds to BTS  202 , transmit queue  404  corresponds to transmit queue  204 , and mobile device  406  corresponds to mobile device  206 . As before, the transmission initially proceeds as in  FIG. 2 . 
     In this case, however, instead of the first packet of the transmission (i.e., packet  310 ) being lost, the initial packets  408  of the transmission are sent successfully at step  410 , and packet  412  is unsuccessfully transmitted at step  414 . As in  FIG. 3 , this loss is not detected for an interval  416 ; however, unlike the case of  FIG. 3 , transmit queue  404  is now empty, so no packets can be sent until interval  416  has elapsed and a retransmission  418  of lost packet  412  occurs at step  420 . Hence during the interval  416 , the queue is empty, so no packets can be transmitted, and application throughput is significantly lowered. Compare this to  FIG. 3 , where a packet drop with a long queue of packets to transmit did not adversely affect application throughput. 
     From  FIGS. 3 and 4 , we can see that packet loss is considerably more costly when the transmit queue is short than when it is long. Accordingly, more effort should be expended to ensure that packets arrive in the former case than in the latter case. In a wireless telecommunications environment, this translates to increasing transmission power.  FIG. 5  depicts a series of strategies for setting a threshold queue length and corresponding transmission power.  FIG. 5A  shows a transmit queue  502  containing some quantity of data  504 . In this embodiment, the threshold  506  is set at one-half of the maximum queue length. Since the amount of data in the queue  504  is less than the threshold  506 , a higher power level is used. In one embodiment, this higher power level is maximum power. 
       FIG. 5B  depicts a transmit queue  508 , corresponding to queue  502 , with threshold  510 , corresponding to threshold  506 . In this case, however, the amount of data in the queue  512  is greater than threshold  510 , and a lower power level can be used. In one embodiment, this lower power level is the lowest power level possible such that the expected SINR will result in a FER that does not exceed a specified maximum FER. 
       FIG. 5C  shows a transmit queue  514  with a higher threshold  516  and a lower threshold  518 , and with an amount of data  520 . In this embodiment, higher threshold  516  is set at one-half of the maximum length of queue  514 , and lower threshold  518  is set at, for example, one-quarter of the maximum length of queue  514 . In this case, the amount of data  520  is below the lower threshold, so a higher power level is used. In one embodiment, this power level is maximum power. 
       FIG. 5D  shows a transmit queue  522 , corresponding to transmit queue  514 , with higher threshold  524  and lower threshold  526  corresponding to higher and lower thresholds  516  and  518  respectively. In this case, however, the amount of data  528  in queue  522  is above lower threshold  526  but below higher threshold  524 . Accordingly, an intermediate transmission power level is used. 
       FIG. 5E  shows a transmit queue  530 , corresponding to transmit queue  514 , with higher threshold  532  and lower threshold  534  corresponding to higher and lower thresholds  516  and  518  respectively. In this case, the amount of data  536  in the queue is above higher threshold  532 , so a lower power level can be used. In one embodiment, this lower power level is the lowest power level possible such that the expected SINR will result in a FER that does not exceed a specified maximum FER. 
       FIG. 5F  shows a transmit queue  538  with a higher threshold  540  and a lower threshold  542 , and with an amount of data  544 . In this embodiment, higher threshold  540  is set at two-thirds of the maximum length of queue  538 , and lower threshold  542  is set at one-third of the maximum length of queue  538 . Contrast this policy for setting thresholds with that of  FIGS. 5C-5E . In this case, the amount of data  544  is below the lower threshold, so a higher power level is used. In one embodiment, this power level is maximum power. 
       FIG. 5G  shows a transmit queue  546 , corresponding to transmit queue  538 , with higher threshold  548  and lower threshold  550  corresponding to higher and lower thresholds  540  and  542  respectively. In this case, however, the amount of data  552  in queue  546  is above lower threshold  550  but below higher threshold  548 . Accordingly, an intermediate transmission power level is used. 
       FIG. 5H  shows a transmit queue  554 , corresponding to transmit queue  538 , with higher threshold  556  and lower threshold  558  corresponding to higher and lower thresholds  540  and  542  respectively. In this case, the amount of data  560  in the queue is above higher threshold  556 , so a lower power level can be used. In one embodiment, this lower power level is the lowest power level possible such that the expected SINR will result in a FER that does not exceed a specified maximum FER. 
     Turning now to  FIG. 6 , a flow diagram of an exemplary method in accordance with one embodiment of the present invention is presented. In one embodiment, this method is performed by a BTS such as BTS  106 . At step  602 , a pilot signal is transmitted. In one embodiment, this pilot signal is transmitted at full power. In another embodiment, this pilot signal is broadcast to all mobile devices within transmission range. 
     Each mobile device is programmed to, upon receiving this pilot signal, respond with a reply such as reply  214  containing a report of the SINR associated with receiving the pilot signal. In step  604 , this reply is received for a specific mobile device (such as mobile device  102 ) with one or more associated transmission queues (such as queue  110 ). 
     Many wireless standards include multiple possible data rates, with higher data rates requiring higher SINR to be successfully received; thus, for a reported SINR, there is a highest data rate that the reported SINR can support for a target FER. For example, EVDO can support twelve distinct data rates. Upon receiving the SINR report, an appropriate data rate is then selected in step  606 . In one embodiment, this data rate is the highest data rate that the reported SINR can support for a target FER. 
     In step  608 , the amount of data (such as data amount  504 ) in the transmit queue from which data is to be sent (such as transmit queue  502 ) is determined and compared to a threshold queue length (such as threshold  506 ). In the embodiment shown, the amount of data in the transmit queue is only compared to a single threshold queue length, but in another embodiment, it may be compared to a plurality of thresholds. 
     If the amount of data in the transmit queue is above the threshold, a packet of data (such as packet  222 ) is transmitted with a lower power level in step  610 . In one embodiment, this power level may be the lowest power level possible such that the expected SINR will result in a FER that does not exceed the target FER. 
     Otherwise, if the amount of data in the transmit queue is below the threshold, a packet of data is transmitted with a higher power level in step  612 . In one embodiment, this power level is the maximum power level. In another embodiment, this power level is the lowest power level possible such that the expected SINR will result in a FER that does not exceed a FER specified to be lower than the target FER. 
     In step  614 , it is determined whether data remains to be sent. In one embodiment, this is accomplished by examining the amount of data in the transmit queue to see if it is zero. In another embodiment, this may be accomplished by examining the state of the transport-layer connection to determine if it is closed or closing. 
     If no data remains to be sent, the connection with the mobile device is closed in step  616 . Otherwise, in the illustrated embodiment, steps  608  et seq. are repeated. In another embodiment, the process may begin again by sending another pilot signal as in step  602 . In yet another embodiment, the mobile device may send an SINR report for the packet sent in step  610  or  612 , allowing the method to repeat from step  604 . 
     Many different arrangements of the various components depicted, as well as components not shown, are possible without departing from the scope of the claims below. Embodiments of our technology have been described with the intent to be illustrative rather than restrictive. Alternative embodiments will become apparent to readers of this disclosure after and because of reading it. Alternative means of implementing the aforementioned can be completed without departing from the scope of the claims below. Certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations and are contemplated within the scope of the claims.