Patent Publication Number: US-2013246835-A1

Title: Sleep clock slew compensation

Description:
RELATED APPLICATION AND PRIORITY CLAIM 
     This application is related to and claims priority from U.S. Provisional Patent Application Ser. No. 61/532,009, filed Sep. 7, 2011, for “DYNAMIC SLEEP TIMELINE AND SEARCH PARAMETERS TO AVOID SYSTEM LOSSES DUE TO LARGE SLEEP CLOCK SLEWS,” which is incorporated herein by reference as if fully set forth below and for all applicable purposes. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to wireless communication systems. More specifically, the present disclosure relates to systems and methods for sleep clock slew compensation. 
     BACKGROUND 
     Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, data and so on. These systems may be multiple-access systems capable of supporting simultaneous communication of multiple mobile devices with one or more base stations. 
     Mobile devices are typically battery operated. It is desirable to maximize the battery life of mobile devices. One way to maximize battery life is to shut off components within the mobile device during periods when those components are not needed/used. By shutting off these components, battery power is conserved without reducing the overall user experience of the mobile device. One example of a component that is shut off is the clock generator. Instead of using the clock generator, a simpler sleep clock may be used. The sleep clock may not have the same accuracy as the clock generator but the sleep clock may use considerably less power than the clock generator. 
     By using a sleep clock, the battery life of mobile devices may be extended. However, using a sleep clock may have drawbacks. For example, since a sleep clock is typically less accurate than a clock generator, the sleep clock may become desynchronized from the clock signal of the network (referred to as clock slew). Clock slew may result in the mobile device losing connection with the network. Benefits may be realized by improvements to mobile devices that use sleep clocks. 
     SUMMARY OF SOME EXAMPLE EMBODIMENTS 
     A method for compensating for sleep clock slew is described. The method includes operating in a discontinuous receive mode. A measured sleep clock slew is determined. Discontinuous receive mode parameters are adjusted based on the measured sleep clock slew. Discontinuous receive mode wake-up procedures are performed. 
     The discontinuous receive mode parameters may include a sleep time for discontinuous receive mode. The discontinuous receive mode parameters may also include a search time for discontinuous receive mode. It may be determined whether the measured sleep clock slew is greater than a sleep clock slew high threshold. 
     The sleep clock slew high threshold may be a search time divided by four. If it is determined that the measured sleep clock slew is not greater than the sleep clock slew high threshold, it may be determined whether the measured sleep clock slew is less than a sleep clock slew low threshold. The sleep clock slew low threshold may be a search time divided by eight. 
     If it is determined that the measured sleep clock slew is less than the sleep clock slew low threshold, it may be determined whether there is a need to increase a sleep time. If it is determined that there is a need to increase the sleep time, adjusting discontinuous receive mode parameters may include increasing the sleep time. The sleep time may be increased by a factor of two. 
     If it is determined that there is not a need to increase the sleep time, it may be determined whether there is a need to decrease a search time. If there is a need to decrease the search time, adjusting discontinuous receive mode parameters may include decreasing the search time. The search time may be decreased by a factor of two. 
     If it is determined that the measured sleep clock slew is greater than the sleep clock slew high threshold, it may be determined whether increasing the search time for all reacquire search dispatches is possible. If it is determined that increasing the search time for all reacquire search dispatches is possible, adjusting discontinuous receive mode parameters may include increasing the search time. The search time may be increased by a factor of two. 
     If it is determined that increasing the search time for all reacquire search dispatches is not possible, it may be determined whether decreasing the sleep time is possible. If it is determined that increasing the sleep time is possible, adjusting discontinuous receive mode parameters may include increasing the sleep time. The sleep time may be increased by a factor of two. If it is determined that increasing the sleep time is not possible, a slow clock frequency estimate may be performed. The method may be performed by a wireless communication device. 
     An apparatus configured for compensating for sleep clock slew is also described. The apparatus includes a processor, memory in electronic communication with the processor, and instructions stored in the memory. The instructions are executable by the processor to operate in a discontinuous receive mode. The instructions are also executable by the processor to determine a measured sleep clock slew. The instructions are further executable by the processor to adjust discontinuous receive mode parameters based on the measured sleep clock slew. The instructions are also executable by the processor to perform discontinuous receive mode wake-up procedures. 
     A wireless device configured for compensating for sleep clock slew is described. The wireless device includes means for operating in a discontinuous receive mode. The wireless device also includes means for determining a measured sleep clock slew. The wireless device further includes means for adjusting discontinuous receive mode parameters based on the measured sleep clock slew. The wireless device also includes means for performing discontinuous receive mode wake-up procedures. 
     A computer-program product configured for compensating for sleep clock slew is also described. The computer-program product includes a non-transitory computer-readable medium having instructions thereon. The instructions include code for causing a wireless device to operate in a discontinuous receive mode. The instructions also include code for causing the wireless device to determine a measured sleep clock slew. The instructions further include code for causing the wireless device to adjust discontinuous receive mode parameters based on the measured sleep clock slew. The instructions also include code for causing the wireless device to perform discontinuous receive mode wake-up procedures. 
     Other aspects, features, and embodiments of the present invention will become apparent to those of ordinary skill in the art, upon reviewing the following description of specific, exemplary embodiments of the present invention in conjunction with the accompanying figures. While features of the present invention may be discussed relative to certain embodiments and figures below, all embodiments of the present invention can include one or more of the advantageous features discussed herein. In other words, while one or more embodiments may be discussed as having certain advantageous features, one or more of such features may also be used in accordance with the various embodiments of the invention discussed herein. In similar fashion, while exemplary embodiments may be discussed below as device, system, or method embodiments, it should be understood that such exemplary embodiments can be implemented in various devices, systems, and methods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a wireless communication system with multiple wireless devices; 
         FIG. 2  is a flow diagram of a method of compensating for sleep clock slew in DRX mode; 
         FIG. 3  is a flow diagram of another method of compensating for sleep clock slew in DRX mode; 
         FIG. 4  shows a timing diagram of DRX wake-up procedures for a wireless communication device when the search time is increased; 
         FIG. 5  shows a timing diagram of DRX wake-up procedures for a wireless communication device when the sleep time is decreased; 
         FIG. 6  shows a timing diagram of DRX wake-up procedures for a wireless communication device when the sleep time is increased; 
         FIG. 7  shows a timing diagram of DRX wake-up procedures for a wireless communication device when the search time is decreased; 
         FIG. 8  is a flow diagram of yet another method of compensating for sleep clock slew in DRX mode; and 
         FIG. 9  illustrates certain components that may be included within a wireless communication device. 
     
    
    
     DETAILED DESCRIPTION OF ALTERNATIVE &amp; EXEMPLARY EMBODIMENTS 
       FIG. 1  shows a wireless communication system  100  with multiple wireless devices. Wireless communication systems  100  are widely deployed to provide various types of communication content such as voice, data and so on. In embodiments of the present invention, a wireless device may be a base station or a wireless communication device. 
     A base station  102  is a station that communicates with one or more wireless communication devices  104 . A base station  102  may also be referred to as, and may include some or all of the functionality of, an access point, a broadcast transmitter, a NodeB, an evolved NodeB, etc. The term “base station” will be used herein. Each base station  102  provides communication coverage for a particular geographic area. A base station  102  may provide communication coverage for one or more wireless communication devices  104 . The term “cell” can refer to a base station  102  and/or its coverage area depending on the context in which the term is used. 
     Communications in a wireless system (e.g., a multiple-access system) may be achieved through transmissions over a wireless link. Such a communication link may be established via a single-input and single-output (SISO), multiple-input and single-output (MISO) or a multiple-input and multiple-output (MIMO) system. A MIMO system includes transmitter(s) and receiver(s) equipped, respectively, with multiple (N T ) transmit antennas and multiple (N R ) receive antennas for data transmission. SISO and MISO systems are particular instances of a MIMO system. The MIMO system can provide improved performance (e.g., higher throughput, greater capacity or improved reliability) if the additional dimensionalities created by the multiple transmit and receive antennas are utilized. 
     The wireless communication system  100  may utilize MIMO. A MIMO system may support both time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, uplink  108  and downlink  106  transmissions are on the same frequency region so that the reciprocity principle allows the estimation of the downlink  106  channel from the uplink  108  channel. This enables a transmitting wireless device to extract transmit beamforming gain from communications received by the transmitting wireless device. 
     The wireless communication system  100  may be a multiple-access system capable of supporting communication with multiple wireless communication devices  104  by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, wideband code division multiple access (W-CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, evolution-data optimized (EV-DO), single-carrier frequency division multiple access (SC-FDMA) systems, 3 rd  Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems and spatial division multiple access (SDMA) systems. 
     The terms “networks” and “systems” are often used interchangeably. A CDMA network may implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, etc. UTRA includes W-CDMA and Low Chip Rate (LCR) while cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may implement a radio technology such as Evolved UTRA (E-UTRA), IEEE 802.11, IEEE 802.16, IEEE 802.20, Flash-OFDMA, etc. UTRA, E-UTRA and GSM are part of Universal Mobile Telecommunication System (UMTS). Long Term Evolution (LTE) is a release of UMTS that uses E-UTRA, UTRA, E-UTRA, GSM, UMTS and Long Term Evolution (LTE) are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 is described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). 
     A wireless communication device  104  may also be referred to as, and may include some or all of the functionality of, a terminal, an access terminal, a user equipment (UE), a subscriber unit, a station, etc. A wireless communication device  104  may be a cellular phone, a personal digital assistant (PDA), a wireless device, a wireless modem, a handheld device, a laptop computer, etc. 
     A wireless communication device  104  may communicate with zero, one or multiple base stations  102  on the downlink  106  and/or uplink  108  at any given moment. The downlink  106  (or forward link) refers to the communication link from a base station  102  to a wireless communication device  104 , and the uplink  108  (or reverse link) refers to the communication link from a wireless communication device  104  to a base station  102 . 
     Global Systems for Mobile Communications (GSM) enhanced data rates for GSM evolution (EDGE) (referred to as GERAN) specifications define two modes of operation for a wireless communication device  104  in idle mode: discontinuous reception (DRX) mode and non-DRX mode. In non-DRX mode, the wireless communication device  104  may monitor all the blocks on the common control channel (CCCH) for the wireless communication device  104 . In non-DRX mode, the wireless communication device  104  may receive a new assignment message for a downlink  106  data transfer with a minimal delay. 
     In DRX mode, the wireless communication device  104  may monitor only the radio blocks on the common control channel (CCCH) that correspond to its own paging group. The paging group may be calculated by the wireless communication device  104  and the wireless communication network using the formulae defined in 3GPP TS 45.002. Thus, the wireless communication device  104  may read only one radio block corresponding to the paging index of the wireless communication device  104  every nth 51-multiframe. The parameter n may be 2, 3, 4, 5, 6, 7, 8 or 9, depending on the specific network configuration. The paging index may be calculated by a wireless communication device  104  and by the wireless communication network using the formulae defined in 3GPP TS 45.002. In DRX mode, the wireless communication device  104  may conserve battery power at the expense of a delay before the network can start a downlink  106  data transfer. 
     At best, in DRX mode the wireless communication device  104  may monitor the paging block corresponding to the paging index of the wireless communication device  104  every 470 milliseconds (ms). At worst, however, in DRX mode the wireless communication device  104  may monitor the paging block corresponding to the paging index of the wireless communication device  104  every 2118 ms. The frequency of the wireless communication device  104  monitoring the paging block may be controlled by broadcast information (assuming SPLIT paging cycle is not used). 
     In DRX mode, the power consumption of the wireless communication device  104  is dependent on the paging cycle. The paging cycle may cycle between a sleep time  112  and a search time  114 . During the sleep time  112 , the wireless communication device  104  may not search for pilot signals (e.g., on the paging channel (PCH)). Thus, during sleep time  112 , the wireless communication device  104  may conserve battery power. During search time  114 , the wireless communication device  104  may actively search for pilot signals. 
     In embodiments of the present invention, when a wireless communication device  104  is in idle mode, the wireless communication device  104  may switch from using a normal clock to using a sleep clock  110 . The sleep clock  110  may consume less power than the normal clock. A sleep clock  110  may slew because of temperature. For example, as phones, dongles and other wireless communication devices  104  grow smaller, heat concentration can cause increases or decreases in the frequency of a sleep clock  110 , resulting in the sleep clock  110  becoming desynchronized with clocks on a base station  102 . This sleep clock  110  slew may cause the wireless communication device  104  to miss scheduled paging messages and potentially lose connection with a communication network. 
     The sleep clock  110  slew may affect both the sleep time  112  and search time  114  of the wireless communication device  104  (when the wireless communication device  104  is camped). A large sleep clock  110  slew may increase the power consumption of the wireless communication device  104  and disrupt the DRX mode. Furthermore, if a connection with a communication network is lost, the wireless communication device  104  may have to reacquire a connection with the network, resulting in further disruption to the DRX mode and a significant power consumption impact. 
     One conventional solution to large sleep clock  110  slew is using expensive sleep crystals (with slews that are more controllable due to temperature variations). However, using sleep crystals may be prohibitively expensive. Another conventional solution is to always use a smaller DRX cycle (e.g., a smaller sleep time  112  and a smaller search time  114 ). However, this may increase the power consumption of the wireless communication device  104 . In yet another conventional solution, the search time  114  may be increased. However, increasing the search time  114  has a power penalty. Furthermore, the search time  114  has a theoretical maximum, depending on the technology. For example, the search time  114  may have a maximum of 576 chips. 
     The wireless communication device  104  may include a slew compensation module  116 . The slew compensation module  116  may allow the wireless communication device  104  to compensate for a large measured sleep clock  110  slew. For example, if the measured sleep clock slew  118  is large, the slew compensation module  116  may increase the search time  114  (thereby increasing the search window size) or decrease the sleep time  112  (thereby decreasing the sleep cycle) for the next DRX wake-up. In one configuration, the slew compensation module  116  may increase the search time  114  or decrease the sleep time  112  until a point is reached where the measured sleep clock slew  118  has reduced. The slew compensation module  116  may then adjust the search time  114  and/or sleep time  112  to compensate for the reduced measured sleep clock slew  118 . 
     The slew compensation module  116  may include a measured sleep clock slew  118 . In one configuration, a controller on the wireless communication device  104  may determine the measured sleep clock slew  118  from search errors seen during a DRX mode wake-up. The measured sleep clock slew  118  may thus be only an estimate of the actual sleep clock  110  slew. 
     The slew compensation module  116  may include a sleep clock slew high threshold  120 . During a DRX mode wake-up, the slew compensation module  116  may compare the measured sleep clock slew  118  with the sleep clock slew high threshold  120 . If the measured sleep clock slew  118  is higher than the sleep clock slew high threshold  120 , the slew compensation module  116  may increase the search time  114  or decrease the sleep time  112 . In one configuration, the sleep clock slew high threshold  120  may be the search window size divided by four. For example, the sleep clock slew high threshold  120  may be the search time  114  divided by four. 
     The slew compensation module  116  may also include a sleep clock slew low threshold  122 . During a DRX mode wake-up, the slew compensation module  116  may also compare the measured sleep clock slew  118  with the sleep clock slew low threshold  122 . If the measured sleep clock slew  118  is lower than the sleep clock slew low threshold  122 , the slew compensation module  116  may decrease the search time  114  or increase the sleep time  112 . In one configuration, the sleep clock slew low threshold  122  may be the search window size divided by eight. For example, the sleep clock slew low threshold  122  may be the search time  114  divided by eight. 
       FIG. 2  is a flow diagram of a method  200  of compensating for sleep clock  110  slew in DRX mode. The method  200  may be performed by a wireless communication device  104 . The wireless communication device  104  may include a slew compensation module  116 . The wireless communication device  104  may enter  202  DRX mode. The wireless communication device  104  may determine  204  a measured sleep clock slew  118 . In one configuration, the wireless communication device  104  may determine  204  the measured sleep clock slew  118  as an estimate of the sleep clock  110  slew from search errors seen during a DRX mode wake-up. 
     The wireless communication device  104  may adjust  206  DRX mode parameters for the next DRX wake-up based on the measured sleep clock slew  118 . For example, if the measured sleep clock slew  118  is large, the wireless communication device  104  may increase the search time  114  or decrease the sleep time  112  for the next DRX wake-up (or multiple DRX wake-up cycles). As another example, if the measured sleep clock slew  118  is small, the wireless communication device  104  may decrease the search time  114  or increase the sleep time  112  for the next DRX wake-up (or multiple DRX wake-up cycles). The changes to DRX mode parameters may be applicable only for the next wake-up, since the current wake-up and search has already happened. The wireless communication device  104  may then perform  208  DRX mode wake-up procedures. 
       FIG. 3  is a flow diagram of another method  300  of compensating for sleep clock  110  slew in DRX mode. The method  300  may be performed by a wireless communication device  104 . The wireless communication device  104  may include a slew compensation module  116 . The wireless communication device  104  may operate  302  in DRX mode. The wireless communication device  104  may determine  304  whether the measured sleep clock slew  118  is greater than the sleep clock slew high threshold  120 . If the measured sleep clock slew  118  is not greater than the sleep clock slew high threshold  120 , the wireless communication device  104  may determine  306  whether the measured sleep clock slew  118  is less than the sleep clock slew low threshold  122 . 
     If the measured sleep clock slew  118  is not less than the sleep clock slew low threshold  122 , the wireless communication device  104  may perform  316  DRX wake-up procedures. If the measured sleep clock slew  118  is less than the sleep clock slew low threshold  122 , the wireless communication device  104  may determine  308  whether there is a need to increase the sleep time  112 . If there is a need to increase the sleep time  112 , the wireless communication device  104  may increase  310  the sleep time  112 . The wireless communication device  104  may then perform  316  DRX wake-up procedures. 
     In embodiments of the present invention, if there is not a need to increase the sleep time  112 , the wireless communication device  104  may determine  312  whether there is a need to decrease the search time  114 . If there is a need to decrease the search time  114 , the wireless communication device  104  may decrease  314  the search time. The wireless communication device  104  may then perform  316  DRX wake-up procedures. If there is not a need to decrease the search time  114 , the wireless communication device  104  may perform  316  DRX wake-up procedures. Typically the sleep time  112  is increased (if possible) prior to decreasing the search time  114  (if possible) because the sleep time  112  has a much larger impact on the standby current usage than the search time. 
     If the measured sleep clock slew  118  is greater than the sleep clock slew high threshold  120 , the wireless communication device  104  may determine  318  whether increasing the search time  114  for all reacquire search dispatches is possible. If increasing the search time  114  for all reacquire search dispatches is possible, the wireless communication device  104  may increase  320  the search time  114 . The wireless communication device  104  may then perform  316  DRX wake-up procedures. 
     If increasing the search time  114  for all reacquire search dispatches is not possible, the wireless communication device  104  may determine  322  whether decreasing the sleep time  112  is possible. If decreasing the sleep time  112  is not possible, the wireless communication device  104  may perform  326  a slow clock frequency estimate. The slow clock frequency estimate may be 1 second long. The wireless communication device  104  may then perform  316  DRX wake-up procedures. If decreasing the sleep time  112  is possible, the wireless communication device  104  may decrease  324  the sleep time  112 . The wireless communication device  104  may then perform  316  DRX wake-up procedures. 
       FIG. 4  shows a timing diagram of DRX wake-up procedures for a wireless communication device  104  when the search time  114  is increased. During DRX wake-up procedures, the wireless communication device  104  may sleep for a sleep time  412   a  and then search for a pilot signal  430   a - c  during a search time  414   a.  If the sleep clock  110  slew is large, the wireless communication device  104  may miss the pilot  430  during the DRX wake-up procedure. Missing the pilot  430  may cause the wireless communication device  104  to lose network connections. 
     After the end  426  of the DRX wake-up procedures, the wireless communication device  104  may increase  424  the search time  114  by a factor of two. The wireless communication device  104  may then begin  428  a DRX wake-up procedure. During the DRX wake-up procedure, the wireless communication device  104  may search for pilots  430  during the search time  414   b  and then sleep for the sleep time  412   b.  Because of the large sleep clock  110  slew, the wireless communication device  104  may be more likely to be searching for a pilot  430  when the pilot  430  occurs if the search time  414   b  has been increased. 
       FIG. 5  shows a timing diagram of DRX wake-up procedures for a wireless communication device  104  when the sleep time  112  is decreased. During DRX wake-up procedures, the wireless communication device  104  may sleep for a sleep time  512   a  and then search for a pilot signal  530   a - c  during a search time  514   a.  If the sleep clock  110  slew is large, the wireless communication device  104  may miss the pilot  530   a  during the DRX wake-up procedure. Missing the pilot  530   a  may cause the wireless communication device  104  to lose network connections. 
     After the end  526  of the DRX wake-up procedures, the wireless communication device  104  may decrease  524  the sleep time  112  by a factor of two. The wireless communication device  104  may then begin  528  a DRX wake-up procedure. During the DRX wake-up procedure, the wireless communication device  104  may search for pilots  530  during the search time  514   b  and then sleep for the sleep time  512   b.  Because of the large sleep clock  110  slew, the wireless communication device  104  may be more likely to be searching for a pilot  530  when the pilot  530  occurs if the sleep time  512   b  has been decreased. 
       FIG. 6  shows a timing diagram of DRX wake-up procedures for a wireless communication device  104  when the sleep time  112  is increased. During DRX wake-up procedures, the wireless communication device  104  may sleep for a sleep time  612   a  and then search for a pilot signal  630   a - c  during a search time  614   a.  If the sleep clock  110  slew is small, the wireless communication device  104  may conserve battery power by increasing the sleep time  112 . 
     After the end  626  of the DRX wake-up procedures, the wireless communication device  104  may increase  624  the sleep time  112  by a factor of two. The wireless communication device  104  may then begin  628  a DRX wake-up procedure. During the DRX wake-up procedure, the wireless communication device  104  may search for pilots  630  during the search time  614   b  and then sleep for the sleep time  612   b.  Because of the small sleep clock  110  slew, the wireless communication device  104  may be likely to be searching for a pilot  630  when the pilot  630  occurs while conserving battery power even though the sleep time  612   b  has been increased. 
       FIG. 7  shows a timing diagram of DRX wake-up procedures for a wireless communication device  104  when the search time  114  is decreased. During DRX wake-up procedures, the wireless communication device  104  may sleep for a sleep time  712   a  and then search for a pilot  730   a - c  signal during a search time  714   a.  If the sleep clock  110  slew is small, the wireless communication device  104  may conserve battery power by decreasing the search time  114 . 
     In embodiments of the present invention, after the end  726  of the DRX wake-up procedures, the wireless communication device  104  may decrease  724  the search time  114  by a factor of two. The wireless communication device  104  may then begin  728  a DRX wake-up procedure. During the DRX wake-up procedure, the wireless communication device  104  may search for pilots  730  during the search time  714   b  and then sleep for the sleep time  712   b.  Because of the small sleep clock  110  slew, the wireless communication device  104  may be likely to be searching for a pilot  730  when the pilot  730  occurs while conserving battery power even though the search time  114  has been decreased. 
       FIG. 8  is a flow diagram of yet another method  800  of compensating for sleep clock  110  slew in DRX mode. The method  800  may be performed by a wireless communication device  104 . The wireless communication device  104  may include a slew compensation module  116 . The wireless communication device  104  may operate  802  in DRX mode. The wireless communication device  104  may determine  804  whether the measured sleep clock slew  118  is greater than the search time  114  divided by four. If the measured sleep clock slew  118  is not greater than the search time  114  divided by four, the wireless communication device  104  may determine  806  whether the measured sleep clock slew  118  is less than the search time  114  divided by eight. 
     If the measured sleep clock slew  118  is not less than the search time  114  divided by eight, the wireless communication device  104  may perform  816  DRX wake-up procedures. If the measured sleep clock slew  118  is less than the search time  114  divided by eight, the wireless communication device  104  may determine  808  whether there is a need to increase the sleep time  112 . If there is a need to increase the sleep time  112 , the wireless communication device  104  may increase  810  the sleep time  112  by a factor of two. The wireless communication device  104  may then perform  816  DRX wake-up procedures. 
     If there is not a need to increase the sleep time  112 , the wireless communication device  104  may determine  812  whether there is a need to decrease the search time  114 . If there is a need to decrease the search time  114 , the wireless communication device  104  may decrease  814  the search time  114  by a factor of two. The wireless communication device  104  may then perform  816  DRX wake-up procedures. If there is not a need to decrease the search time  114 , the wireless communication device  104  may perform  816  DRX wake-up procedures. 
     If the measured sleep clock slew  118  is greater than the search time  114  divided by four, the wireless communication device  104  may determine  818  whether increasing the search time  114  for all reacquire search dispatches is possible. If increasing the search time  114  for all reacquire search dispatches is possible, the wireless communication device  104  may increase  820  the search time  114  by a factor of two. The wireless communication device  104  may then perform  816  DRX wake-up procedures. 
     If increasing the search time  114  for all reacquire search dispatches is not possible, the wireless communication device  104  may determine  822  whether decreasing the sleep time  112  is possible. If decreasing the sleep time  112  is not possible, in embodiments of the present invention, the wireless communication device  104  may perform  826  a slow clock frequency estimate. The slow clock frequency estimate may be 1 second long. The wireless communication device  104  may then perform  816  DRX wake-up procedures. If decreasing the sleep time  112  is possible, the wireless communication device  104  may decrease  824  the sleep time  112  by a factor of two. The wireless communication device  104  may then perform  816  DRX wake-up procedures. 
       FIG. 9  illustrates certain components that may be included within a wireless communication device  904 . The wireless communication device  904  may be an access terminal, a mobile station, a user equipment (UE), etc. The wireless communication device  904  includes a processor  903 . The processor  903  may be a general purpose single- or multi-chip microprocessor (e.g., an ARM), a special purpose microprocessor (e.g., a digital signal processor (DSP)), a microcontroller, a programmable gate array, etc. The processor  903  may be referred to as a central processing unit (CPU). Although just a single processor  903  is shown in the wireless communication device  904  of  FIG. 9 , in an alternative configuration, a combination of processors  903  (e.g., a general purpose CPU and digital signal processor (DSP)) could be used. 
     The wireless communication device  904  also includes memory  905 . The memory  905  may be any electronic component capable of storing electronic information. The memory  905  may be embodied as random access memory (RAM), read-only memory (ROM), magnetic disk storage media, optical storage media, flash memory devices in RAM, on-board memory included with the processor, EPROM memory, EEPROM memory, registers and so forth, including combinations thereof. 
     Data  907   a  and instructions  909   a  may be stored in the memory  905 . The instructions  909   a  may be executable by the processor  903  to implement the methods disclosed herein. Executing the instructions  909   a  may involve the use of the data  907   a  that is stored in the memory  905 . When the processor  903  executes the instructions  909   a,  various portions of the instructions  909   b  may be loaded onto the processor  903 , and various pieces of data  907   b  may be loaded onto the processor  903 . 
     The wireless communication device  904  may also include a transmitter  911  and a receiver  913  to allow transmission and reception of signals to and from the wireless communication device  904 . The transmitter  911  and receiver  913  may be collectively referred to as a transceiver  915 . An antenna  917  may be electrically coupled to the transceiver  915 . The wireless communication device  904  may also include (not shown) multiple transmitters, multiple receivers, multiple transceivers and/or multiple antennas. 
     The wireless communication device  904  may include a digital signal processor (DSP)  921 . The wireless communication device  904  may also include a communications interface  923 . The communications interface  923  may allow a user to interact with the wireless communication device  904 . 
     The various components of the wireless communication device  904  may be coupled together by one or more buses  919 , which may include a power bus, a control signal bus, a status signal bus, a data bus, etc. For the sake of clarity, the various buses are illustrated in  FIG. 9  as a bus system  919 . 
     The techniques described herein may be used for various communication systems, including communication systems that are based on an orthogonal multiplexing scheme. Examples of such communication systems include Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems and so forth. An OFDMA system utilizes orthogonal frequency division multiplexing (OFDM), which is a modulation technique that partitions the overall system bandwidth into multiple orthogonal sub-carriers. These sub-carriers may also be called tones, bins, etc. With OFDM, each sub-carrier may be independently modulated with data. An SC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit on sub-carriers that are distributed across the system bandwidth, localized FDMA (LFDMA) to transmit on a block of adjacent sub-carriers, or enhanced FDMA (EFDMA) to transmit on multiple blocks of adjacent sub-carriers. In general, modulation symbols are sent in the frequency domain with OFDM and in the time domain with SC-FDMA. 
     The term “determining” encompasses a wide variety of actions and, therefore, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing and the like. 
     The phrase “based on” does not mean “based only on,” unless expressly specified otherwise. In other words, the phrase “based on” describes both “based only on” and “based at least on.” 
     The term “processor” should be interpreted broadly to encompass a general purpose processor, a central processing unit (CPU), a microprocessor, a digital signal processor (DSP), a controller, a microcontroller, a state machine, and so forth. Under some circumstances, a “processor” may refer to an application specific integrated circuit (ASIC), a programmable logic device (PLD), a field programmable gate array (FPGA), etc. The term “processor” may refer to a combination of processing devices, e.g., a combination of a digital signal processor (DSP) and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor (DSP) core, or any other such configuration. 
     The term “memory” should be interpreted broadly to encompass any electronic component capable of storing electronic information. The term memory may refer to various types of processor-readable media such as random access memory (RAM), read-only memory (ROM), non-volatile random access memory (NVRAM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable PROM (EEPROM), flash memory, magnetic or optical data storage, registers, etc. Memory is said to be in electronic communication with a processor if the processor can read information from and/or write information to the memory. Memory that is integral to a processor is in electronic communication with the processor. 
     The terms “instructions” and “code” should be interpreted broadly to include any type of computer-readable statement(s). For example, the terms “instructions” and “code” may refer to one or more programs, routines, sub-routines, functions, procedures, etc. “Instructions” and “code” may comprise a single computer-readable statement or many computer-readable statements. 
     The functions described herein may be implemented in software or firmware being executed by hardware. The functions may be stored as one or more instructions on a computer-readable medium. The terms “computer-readable medium” or “computer-program product” refers to any tangible storage medium that can be accessed by a computer or a processor. By way of example, and not limitation, a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. It should be noted that a computer-readable medium may be tangible and non-transitory. The term “computer-program product” refers to a computing device or processor in combination with code or instructions (e.g., a “program”) that may be executed, processed or computed by the computing device or processor. As used herein, the term “code” may refer to software, instructions, code or data that is/are executable by a computing device or processor. 
     The methods disclosed herein comprise one or more steps or actions for achieving the described method. The method steps and/or actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is required for proper operation of the method that is being described, the order and/or use of specific steps and/or actions may be modified without departing from the scope of the claims. 
     Further, it should be appreciated that modules and/or other appropriate means for performing the methods and techniques described herein, such as those illustrated by  FIGS. 2 ,  3  and  8 , can be downloaded and/or otherwise obtained by a device. For example, a device may be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via a storage means (e.g., random access memory (RAM), read-only memory (ROM), a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a device may obtain the various methods upon coupling or providing the storage means to the device. 
     It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes and variations may be made in the arrangement, operation and details of the systems, methods, and apparatus described herein without departing from the scope of the claims.