Abstract:
Methods and apparatus are described which increase the probability and/or frequency that devices with comparatively faster clocks in a network than other devices in the network will transmit beacon signals are described. As a result, devices with faster clocks will tend to drive system synchronization to convergence faster than if all devices transmitted beacons at the same rate, thus facilitating more reliable maintenance of system synchronization since the devices with faster clocks will tend to transmit more frequently.

Description:
FIELD 
       [0001]    Various embodiments are directed to wireless communication device synchronization in a network and more specifically, to methods and apparatus for efficiently performing distributed synchronization, e.g., in an ad-hoc network. 
       BACKGROUND 
       [0002]    Wireless devices, e.g., portable devices, often use relatively inexpensive, and thus often somewhat inaccurate, clocks to maintain their understanding of time. As a result of differences between crystal oscillators in different devices, the internal clocks of different devices may drift causing devices in a network to lose synchronization over time unless measures are taken to maintain synchronization between the different devices. 
         [0003]    In at least some systems devices transmit beacon signals including information, in the form of a time stamp, indicating the transmitting device&#39;s understanding of the current time. Devices in the network receiving the time indicated in the beacon signal can compare the indicated time to the time indicated by their internal clock. 
         [0004]    In some systems, devices which receive a beacon signal indicating a time which is ahead of the time indicated by the device&#39;s internal clock will change the device&#39;s internal time to match that of the time indicated in the beacon signal. From multiple beacon signals received from the same device over time, it is possible to obtain an understanding of how fast the transmitting device&#39;s clock is, relative the internal clock of the device receiving the beacon signals. 
         [0005]    In some systems devices adjust their clocks if the time indicated in a beacon signal is ahead of the internal time at which the device detects receipt of the beacon signal, but not if the time indicated in the beacon signal is behind the time indicated by the device&#39;s internal clock. In such systems beacon signals from devices having relatively slow clocks will result in fewer timing adjustments being made than beacon signals from devices having faster clocks. Accordingly, the beacon signals transmitted by the devices having slower clocks are less likely than the beacon signals from the devices having faster clocks to facilitate achieving and/or maintaining timing synchronization. 
         [0006]    Generally in systems which use beacon signals, the relative clock rates of different devices are not taken into consideration when determining if or how frequently a device should transmit beacon signals. It should be appreciated that it would be desirable if methods and/or apparatus could be developed which would increase the probability and/or frequency of devices with faster clocks transmitting beacon signals including timing information used for synchronization purposes and/or decrease the probability and/or frequency of devices with comparatively slow clocks transmitting beacon signals. 
       SUMMARY 
       [0007]    Methods and apparatus which increase the probability and/or frequency that devices with comparatively faster clocks in a network will transmit beacon signals are described. As a result, devices with faster clocks will tend to drive system synchronization to faster convergence and facilitate more reliable maintenance of system synchronization since the devices with faster clocks will tend to transmit synchronization signals, e.g., beacon signals, more frequently than other devices. 
         [0008]    In various embodiments, a wireless communications device selects an initial backoff time value for a beacon slot to control the likelihood that the wireless communications device will transmit a beacon signal during the beacon slot. In some embodiments, the exemplary method increases the likelihood that a wireless communications device which transmitted a beacon signal in a beacon slot and did not adjust its clock timing based on a received beacon signal from another device during the beacon slot will transmit a beacon signal during the next successive beacon slot. 
         [0009]    The coverage range of the devices may be, and in some embodiments is, taken into consideration in determining whether or not a device should transmit a beacon signal in a beacon slot. If a device receives a strong beacon signal the received beacon signal is likely to have a similar coverage range to that which may be achieved by device transmission. In some embodiments, the intended beacon transmission is cancelled based on the characteristics of the received beacon signal satisfying certain criteria. In some embodiments, the criteria used for cancellation of an intended beacon signal include a time indication criteria and a received power level criteria. In some embodiments cancellation criteria include a requirement that the time indicated in the received beacon signal be greater than the time indicated by the clock of the communications device which received the beacon signal and that the power level of the received beacon signal exceed a threshold used to determine that the device which transmitted the received beacon is very close to the device which received the beacon. If the cancellation criteria are satisfied a beacon transmission is cancelled, and the beacon signal is not sent. Cancellation differs from a simple pause of counting down a backoff count which may occur due to the results of a carrier sensing operation but does not result in cancellation of the beacon transmission. 
         [0010]    In some embodiments, a wireless communications device reduces a current backoff time value in response to a detected beacon signal satisfying certain criteria, other than a sensed carrier being unoccupied for a period of time, to increase the likelihood that the wireless communications device will transmit its intended beacon signal during the current beacon slot. In some embodiments, the criteria used for reducing a current backoff time value in response to a detected beacon signal include a time indication critera, e.g., the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device which received the beacon signal. 
         [0011]    An exemplary method of operating a communications device, in accordance with some embodiments, comprises: determining a backoff time used in controlling transmission of a first beacon signal in a first beacon slot; monitoring to detect receipt of a beacon signal during said backoff time; and in response to said monitoring detecting receipt of a beacon signal performing one of: altering said determined backoff time or canceling transmission of the beacon signal. An exemplary communications device, in accordance with some embodiments, comprises: at least one processor configured to: determine a backoff time used in controlling transmission of a first beacon signal in a first beacon slot; monitor to detect receipt of a beacon signal during said backoff time; and perform one of: altering said determined backoff time or canceling transmission of the beacon signal, in response to said monitoring detecting receipt of a beacon signal. The exemplary communications device further comprises memory coupled to said at least one processor. 
         [0012]    While various embodiments have been discussed in the summary above, it should be appreciated that not necessarily all embodiments include the same features and some of the features described above are not necessary but can be desirable in some embodiments. Numerous additional features, embodiments and benefits of various embodiments are discussed in the detailed description which follows. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]      FIG. 1  is a drawing of an exemplary communications system in accordance with an exemplary embodiment. 
           [0014]      FIG. 2A  is a first part of a flowchart of an exemplary method of operating a communications device in accordance with various exemplary embodiments. 
           [0015]      FIG. 2B  is a second part of a flowchart of an exemplary method of operating a communications device in accordance with various exemplary embodiments. 
           [0016]      FIG. 2C  is a third part of a flowchart of an exemplary method of operating a communications device in accordance with various exemplary embodiments. 
           [0017]      FIG. 3  is a drawing of an exemplary communications device, e.g., a peer to peer wireless communications device, in accordance with an exemplary embodiment. 
           [0018]      FIG. 4A  is a first part of an assembly of modules which can, and in some embodiments is, used in the exemplary wireless communications device illustrated in  FIG. 3 . 
           [0019]      FIG. 4B  is a second part of an assembly of modules which can, and in some embodiments is, used in the exemplary wireless communications device illustrated in  FIG. 3 . 
           [0020]      FIG. 4C  is a third part of an assembly of modules which can, and in some embodiments is, used in the exemplary wireless communications device illustrated in  FIG. 3 . 
           [0021]      FIG. 5  illustrates an example of exemplary peer to peer wireless terminal determining a backoff time, used to control transmission of a beacon signal, based on information corresponding to received beacon signals from a prior beacon slot in accordance with an exemplary embodiment. 
           [0022]      FIG. 6  illustrates another example of an exemplary peer to peer wireless terminal determining a backoff time, used to control transmission of a beacon signal, based on information corresponding to received beacon signals from a prior beacon slot in accordance with an exemplary embodiment. 
           [0023]      FIG. 7  illustrates an example of an exemplary peer to peer wireless terminal determining a backoff time, used to control transmission of a beacon signal, based on whether or not the wireless terminal transmitted a beacon in an immediately preceding beacon slot in accordance with an exemplary embodiment. 
           [0024]      FIG. 8  illustrates another example of an exemplary peer to peer wireless terminal determining a backoff time, used to control transmission of a beacon signal, based on whether or not the wireless terminal transmitted a beacon in an immediately preceding beacon slot in accordance with an exemplary embodiment. 
           [0025]      FIG. 9  illustrates an exemplary peer to peer wireless terminal reducing its current value of its backoff time value in response to detecting a beacon signal from another wireless terminal with characteristics that satisfies particular criteria in accordance with an exemplary embodiment. 
           [0026]      FIG. 10  illustrates an exemplary peer to peer wireless terminal cancelling an intended beacon signal transmission in response to detecting a beacon signal from another wireless terminal with characteristics that satisfies particular criteria in accordance with an exemplary embodiment. 
           [0027]      FIG. 11  illustrates an exemplary peer to peer wireless terminal transmitting an intended beacon signal transmission in response to detecting that its backoff timer has expired within the current beacon slot in accordance with an exemplary embodiment. 
           [0028]      FIG. 12  illustrates an exemplary peer to peer wireless terminal cancelling an intended beacon signal transmission in response to detecting that the current beacon slot has expired in accordance with an exemplary embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]      FIG. 1  is a drawing of an exemplary communications system  100  in accordance with an exemplary embodiment. Exemplary communications system  100  includes a peer to peer network  102 , e.g., an ad-hoc peer to peer network. Peer to peer network includes a plurality of peer to peer wireless terminals (peer to peer wireless terminal  1   104 , peer to peer wireless terminal  2   106 , peer to peer wireless terminal  3   108 , . . . , peer to peer wireless terminal N−1  110 , peer to peer wireless terminal N  112 . 
         [0030]    At least some of the peer to peer wireless terminals ( 104 ,  106 ,  108 , . . . ,  110 ,  112 ) are mobile devices that implement peer to peer communications, e.g., direct device to device communications. The peer to peer wireless terminals may move throughout system  100  and form multiple local peer to peer networks which may be disconnected from one another and/or overlap with one another. 
         [0031]    In various embodiments, timing synchronization of the network  102  is performed in a decentralized manner. Wireless communications devices ( 104 ,  106 ,  108 , . . . ,  110 ,  112 ) transmit beacon signals including time stamps communicating the transmitting device&#39;s notion of time. In some embodiments time stamps are in microseconds. The network tends to synchronize to the device with the fastest clock in the network. A device intending to transmit a beacon signal in a beacon slot determines a backoff time value, used for controlling transmission of the intended beacon signal. The determined backoff time value is, in some embodiments, an initial setting for a backoff timer which counts down during the beacon slot under certain predetermined conditions, e.g., the device is not sensing a received signal above a first power threshold or a decodable signal. The determined backoff time, in some embodiments, is a function of statistical information corresponding to previously received beacon signals and/or whether or not the device transmitted a beacon signal in a preceding beacon slot and/or whether or not the wireless communications device adjusted its clock in the prior beacon slot based on received beacon signals from other wireless communications devices. 
         [0032]    In accordance with a feature of various embodiments, the current backoff time is altered, e.g., reduced, in a current beacon slot in response to a received beacon signal from another device meeting certain predetermined criteria. Decreasing the backoff time increases the likelihood that the intended beacon will be transmitted during the beacon slot. In accordance with a feature of various embodiments, the intended beacon transmission is cancelled for the current beacon slot in response to a received beacon signal meeting certain predetermined criteria. 
         [0033]    A wireless communications device, e.g., peer to peer wireless terminal  104 , monitors to detect beacon signals from other devices during its backoff time, e.g., before its backoff timer has expired. The wireless communications device performs one of altering the determined backoff time or canceling transmission of the intended beacon in response to a detected beacon signal having certain characteristics. For example, the wireless communications device reduces the backoff time value in response to determining that the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device receiving the beacon signal. In this example, the wireless communications device has determined that it has a faster clock than the device which transmitted the beacon signal and wireless communications device would like to increase its likelihood that it transmits a beacon signal in the current beacon slot. As another example, the wireless communications device cancels the intended beacon transmission if the power of the received beacon exceeds a second power level threshold and the time indicated in the received beacon signal is greater than the time indicated by the clock of the transmitting device. In this example, a very strong received beacon signal from a device with a faster clock has been detected. The very strong received beacon signal indicates the device which transmitted the beacon signal is closely located to the device which received the beacon signal, and since it is desirable to synchronize the network to the faster clock there is no point in transmitting the intended beacon signal since the receiving signal has updated its timing to match the faster clock and the transmitted beacon would be redundant resulting in a waste of battery power and air link resources. 
         [0034]    In various embodiments, the network  102  synchronizes with respect to the clock of wireless communications device having the fastest clock. In one aspect of some embodiments, an intended beacon signal which would be substantially redundant is cancelled based on a characteristic of received beacon signal received during the time slot of the intended transmission. In another aspect of some embodiments, a likelihood of transmission of an intended beacon signal transmission during a beacon slot is increased based on a characteristic of a received beacon signal received during the beacon slot, e.g., the backoff time is reduced in response to the received beacon signal satisfying predetermined criteria. 
         [0035]      FIG. 2 , comprising the combination of  FIG. 2A ,  FIG. 2B  and  FIG. 2C  is a flowchart  200  of an exemplary method of operating a communications device in accordance with various exemplary embodiments. Operation of the exemplary method starts in step  202 , where the communications device is powered on and initialized and proceeds to step  204 . In step  204 , the communications device determines if a majority of time stamps, received prior to a first beacon slot, included in received beacon signals indicated an earlier time than a time indicated by the clock of the communications device at the time of receipt of the beacon signals. Operation proceeds from step  204  to step  206 . 
         [0036]    In step  206 , the communications device determines a backoff time used in controlling transmission of a first beacon signal in a first beacon slot. In some embodiments, step  206  includes one or more of steps  208  and  210 . In step  208  the communications device increases a probability that a short backoff time will be determined when it is determined that the majority of time stamps included in received beacon signals indicated an earlier time that the time indicated by the clock of the communications device at the time of receipt of the beacon signals as compared to the probability when it is not determined that the majority of time stamps included in received beacon signals indicated an earlier time than the time indicated by the clock of the communications device at the time of receipt of the beacon signals. In step  210  the communications device increases a probability that a short backoff time will be determined when said communications device transmitted a beacon signal in a beacon slot immediately preceding the first beacon slot. In some embodiments, the increase in probability of step  210  is further dependent upon the condition that the wireless communications device has not adjusted its timing in the beacon slot immediately preceding the first beacon slot based on received beacon signals from other devices. 
         [0037]    Operation proceeds from step  206  via connecting nodes (A  212 , B 214 , and C  216 ) to steps ( 218 ,  240 , and  248 ), respectively. In step  218  the communications device monitors to detect receipt of a beacon signal during said backoff time. Step  218  includes step  220  in which the communications device checks if the communications device has detected receipt of a beacon signal. If the communications device has detected receipt of a beacon signal, then operation proceeds from step  220  to step  222  in response to the detected beacon signal; operation also proceeds from the output of step  220  to the input of step  220  to check if another beacon signal is detected at a later point in time. If the communications device has not detected receipt of a beacon signal, then operation proceeds from the output of step  220  to the input of step  220  to check a beacon signal is detected at a later point during the monitoring. One iteration of step  222  is performed for each detected beacon signal during the monitoring of step  218 . 
         [0038]    In step  222  the communications device performs one of altering said determined backoff time or canceling transmission of the first beacon signal in response to detecting a beacon signal with characteristics satisfying one or more predetermined criteria. Step  222  includes steps  224 ,  226 ,  228 ,  230 ,  232 ,  234 ,  236 ,  237  and  238 . In step  224  the communications device compares a time indicated in a received beacon signal to a time indicated at the time of receipt of said beacon signal by a clock of said communications device. Operation proceeds from step  224  to step  226 . In step  226 , if the comparison of step  224  indicates that the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device, then operation proceeds from step  226  to step  228 , in which the communications device sets the backoff time to a reduced value, e.g., changes the current backoff time value to a reduced value. In some embodiments, the reduction of the backoff time value in step  228  is by an amount which is a function of the time difference between the time indicated in the received beacon and the time indicated by the clock of the communications device at the time the beacon was received. In some such embodiments, the larger the difference, the larger the reduction in the backoff time. In some embodiments, the reduction of the backoff time value in step  228  is by a predetermined amount. It should be appreciated that the changes, e.g., reductions, in the backoff time value in step  228  are performed independent of any internal clock changes made for synchronization purposes. However, if the comparison of step  224  does not indicate that the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device, then operation proceeds from step  226  to step  230 . 
         [0039]    In step  230  the communications device tests if the comparison of step  230  indicates that the time indicated in the received beacon signal is greater than the time indicated by the clock of the communications device. If the comparison indicates that the time indicated in the received beacon signal is greater than the time indicated by the clock of the communications device then operation proceeds from step  230  to step  232  in which the communications device updates the time indicated by the clock of the communications device to match the time indicated in the received beacon signal. Operation proceeds from step  232  to step  234 . In step  232  the communications device compares the power level of the received beacon signal to a second power level threshold. In various embodiments, the second power level threshold is greater than the first power level threshold. If the power of the received beacon signal exceeds a second power level threshold, then operation proceeds from step  234  to step  236 ; otherwise operation proceeds from step  234  to step  237 . In step  236 , the communications device cancels the transmission of the first beacon signal. Returning to step  237 , in step  237  the communications device alters the backoff time, e.g., sets the backoff time to a reduced value, if the power of the received beacon signal is less than the second power level threshold. Operation proceeds from step  237  to step  238 . 
         [0040]    Returning to step  230 , if the comparison of step  224  does not indicate that the time indicated in the received beacon signal is greater than the time indicated by the clock of the communications device then operation proceeds from step  230  to step  238 . In step  238  the communications device is controlled to not perform a cancellation of the transmission of the first beacon signal in response to the received beacon signal. 
         [0041]    Returning to step  240 , in step  240  the communications device checks as to whether or not a signal which exceeds a first power threshold or is decodable by the communications device is being received. If the check of step  240  indicates that a signal which exceeds a first power threshold or is decodable by the communications device is being received, then operation proceeds from step  240  to step  242 , in which the communications device suspends, e.g., stop for a period of time, reduction of said backoff time during receipt of a signal which exceeds the first power level or is decodable by the communications device. This suspension, e.g., stop for a period of time, is in contrast to cancellation as is performed in step  236  and step  260 . However, if the check of step  240  does not indicate that a signal which exceeds a first power threshold or is decodable by the communications device is being received, then operation proceeds from step  240  to step  244 , in which the communications device reduces a backoff time at a predetermined rate during said first beacon slot during time when a signal which exceeds a first power threshold or is decodable by the communications device is being received. In some embodiments, the first power threshold is a carrier sensing threshold level. Operation proceeds from step  242  or step  244  to step  240  via connecting node D  246 . 
         [0042]    Returning to step  248 , in step  248  the communications device monitors to detect if the backoff timer has expired within the first beacon slot. Step  248  includes step  250  and step  252 . In step  250  the communications device checks if the backoff timer has expired. If the backoff timer has expired, then the operation proceeds from step  250  to step  254 . However, if the backoff timer has not expired then operation proceeds from step  250  to step  252 . In step  252  the communications device checks if the first beacon slot has ended. If the first beacon slot has ended, operation proceeds from step  252  to step  260 ; otherwise, operation proceeds from step  252  to step  250 , where the communications device again checks as to whether the backoff timer has expired. Returning to step  260 , in step  260  the communications device cancels transmission of the first beacon signal. Returning to step  254 , in step  254  the communications device checks as to whether or not the intended transmission of the first beacons signal has already been cancelled. If the intended transmission of the first beacon has already been cancelled, e.g., in step  236 , then operation proceeds from step  254  to step  256  where the wireless communications device is controlled to refrain from transmitting the first beacon signal even though the backoff timer has expired and the first beacon slot has not yet ended. However, if the intended transmission of the first beacon signal has not been previously canceled then operation proceeds from step  254  to step  258 , in which the communications device transmits the first beacon signal. 
         [0043]    Flowchart  200  of  FIG. 2  illustrates exemplary execution of a set of steps corresponding to one beacon slot. In general, the exemplary method of flowchart  200  is repeated for a plurality of beacons slots, e.g., a plurality of successive beacon slots with the first beacon slot identified in the flowchart corresponding to a different beacon slot for each iteration of the flowchart. 
         [0044]      FIG. 3  is a drawing of an exemplary communications device  300 , e.g., a peer to peer mobile node, in accordance with an exemplary embodiment. Exemplary communications device  300  is, e.g., one of the peer to peer wireless communications devices (peer to peer wireless terminal  1   104 , peer to peer wireless terminal  2   106 , peer to peer wireless terminal  3   108 , . . . , peer to peer wireless terminal N−1  110 , peer to peer wireless terminal N  112 ) system  100  of  FIG. 1 . Exemplary wireless communications device  300  may, and sometimes does, implement a method in accordance with flowchart  200  of  FIG. 2 . 
         [0045]    Communications device  300  includes a processor  302  and memory  304  coupled together via a bus  309  over which the various elements ( 302 ,  304 ) may interchange data and information. Communications device  300  further includes an input module  306  and an output module  308  which may be coupled to processor  302  as shown. However, in some embodiments, the input module  306  and output module  308  are located internal to the processor  302 . Input module  306  can receive input signals. Input module  306  can, and in some embodiments does, include a wireless receiver and/or a wired or optical input interface for receiving input. Output module  308  may include, and in some embodiments does include, a wireless transmitter and/or a wired or optical output interface for transmitting output. In some embodiments, memory  304  includes routines  311  and data/information  313 . Communications device  300  also includes a clock and/or clock module  307  coupled to processor  302 . In some embodiments, the clock and/or clock module  307  are located internal to processor  302 . 
         [0046]    In some embodiments, processor  302  is configured to: determine a backoff time used in controlling transmission of a first beacon signal in a first beacon slot; monitor to detect receipt of a beacon signal during said backoff time; and perform one of: altering said determined backoff time or canceling transmission of the beacon signal, in response to said monitoring detecting receipt of a beacon signal. In some such embodiments, processor  302  is configured to: compare a time indicated in a received beacon signal to a time indicated at the time of receipt of said received beacon signal by a clock of said communications device, if said monitoring detects receipt of a beacon signal; and set the backoff time to a reduced value, when said comparing indicates that the time indicated in the received beacon signal is less than the time indicated by the clock of said communications device. 
         [0047]    In various embodiments, processor  302  is further configured to: transmit the first beacon signal if said backoff time expires during said first beacon slot; and cancel transmission of said first beacon signal if said backoff time does not expire within said first beacon slot. In various embodiments, processor  302  is further configured to: reduce the backoff time at a predetermined rate during said first beacon slot during time when a signal, which exceeds a first power level threshold or is decodable by the communications device, is not being received; and suspend reduction of said backoff time during receipt of a signal which exceeds the first power level threshold or is decodable by the communications device. 
         [0048]    In some embodiments, processor  302  is further configured to: compare a time indicated in a received beacon signal to a time indicated at the time of receipt of said received beacon signal by a clock of said communications device, if said monitoring detects receipt of a beacon signal. In some such embodiments processor  302  is further configured to: update the time indicated by the clock of the communications device to match the time indicated in the received beacon signal when said comparing indicates that the time indicated in the received beacon signal is greater than the time indicated by the clock of said communications device; and cancel transmission of the first beacon signal if the power of the received beacon signal exceeds a second power level threshold. In some such embodiments, processor  302  is further configured to alter, e.g., reduce, the backoff time if the power of the received beacon signal is less than the second threshold. 
         [0049]    In various embodiments processor  302  is further configured to: determine if a majority of time stamps, received prior to said first beacon slot, included in received beacon signals indicated an earlier time than a time indicated by the clock of the communications device at the time of receipt of the beacon signals; and increase a probability that a short backoff time will be determined as compared to the probability when it is not determined that the majority of time stamps included in received beacon signals indicated an earlier time than the time indicated by the clock of the communications device at the time of receipt of the beacon signals, if it is determined that the majority of time stamps included in received beacon signals indicated an earlier time than the time indicated by the clock of the communications device at the time of receipt of the beacon signals, as part of being configured to determine a backoff time. In some embodiments, processor  302  is configured to increase a probability that a short backoff time will be determined when said communications device transmitted a beacon signal in a beacon slot immediately preceding said first beacon slot, as part of being configured to determine a backoff time. 
         [0050]      FIG. 4  is an assembly of modules  400  which can, and in some embodiments is, used in the exemplary communications device  300  illustrated in  FIG. 3 . The modules in the assembly  400  can be implemented in hardware within the processor  302  of  FIG. 3 , e.g., as individual circuits. Alternatively, the modules may be implemented in software and stored in the memory  304  of wireless communications device  300  shown in  FIG. 3 . In some such embodiments, the assembly of modules  400  is included in routines  311  of memory  304  of device  300  of  FIG. 3 . While shown in the  FIG. 3  embodiment as a single processor, e.g., computer, it should be appreciated that the processor  302  may be implemented as one or more processors, e.g., computers. When implemented in software the modules include code, which when executed by the processor, configure the processor, e.g., computer,  302  to implement the function corresponding to the module. In some embodiments, processor  302  is configured to implement each of the modules of the assembly of modules  400 . In embodiments where the assembly of modules  400  is stored in the memory  304 , the memory  304  is a computer program product comprising a computer readable medium, e.g., a non-transitory computer readable medium, comprising code, e.g., individual code for each module, for causing at least one computer, e.g., processor  302 , to implement the functions to which the modules correspond. 
         [0051]    Completely hardware based or completely software based modules may be used. However, it should be appreciated that any combination of software and hardware (e.g., circuit implemented) modules may be used to implement the functions. As should be appreciated, the modules illustrated in  FIG. 4  control and/or configure the communications device  300  or elements therein such as the processor  302 , to perform the functions of the corresponding steps illustrated and/or described in the method of flowchart  200  of  FIG. 2 . 
         [0052]    Assembly of modules  400 , comprising the combination of Part A  401 , Part B  403  and Part C  405 , includes a module for determining if a majority of time stamps received prior to a first beacon slot, included in received beacon signals indicated an earlier time by the clock of the communications device at the time of receipt of the beacon signals  404 , a module for determining a backoff time used in controlling transmission of a first beacon signal in a first beacon slot  406 , a module for monitoring to detect receipt of a beacon signal during said backoff time  418 , and a module for performing one of altering said determined backoff time or cancelling transmission of the first beacon signal in response to said monitoring detecting receipt of a beacon signal  422 . Module  406  includes a module for increasing a probability that a short backoff time will be determined when it is determined that the majority of time stamps included in received beacon signals indicated an earlier time than the time indicated by the clock of the communications device at the time of receipt of the beacon signals as compared to the probability when it is not determined that the majority of time stamps indicated in receive beacon signals indicated an earlier time than the time indicated by the clock of the communications device at the time of receipt of the beacon signals  408  and a module for increasing the probability that short backoff time will be determined when said communications device transmitted a beacon signal in a beacon slot immediately preceding the first beacon slot  410 . 
         [0053]    Module  410  includes a module for receiving beacons signals  419 , a module for determining if receipt of a beacon signal was detected  420  and a module for controlling operation as a function of whether or not receipt of a beacon signal was detected  421 . Module  422  includes a module for comparing a time indicated in a received beacon signal to a time indicated at the time of receipt of said received beacon signal by a clock of said communications device if said monitoring detects receipt of a beacon signal  424 , a module for controlling operation as a function of whether or not the comparison indicates that the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device  426 , a module for setting the backoff time to a reduced value when said comparing indicates that the time indicated in the received beacon signal is less than the time indicated by the clock of the communications device  428 , a module for controlling operation as a function of whether or not the comparison indicates that the time indicated in the received beacon signal is greater than the time indicated by the clock of the communications device  430 , a module for updating time indicated by the clock of the communications device to match the time indicated in the received beacon signal when said comparing indicates that the time in the received beacon signal is greater than the time indicated by the clock of said communications device  432 , a module for comparing the power of the received beacon signal to a second power threshold level  434 , a module for controlling operation as a function of whether or not the power of the received beacon signal exceeds a second power threshold  435 , a module for canceling transmission of the first beacon signal if the power of the received beacon signal exceeds a second power level threshold  436 , a module for altering the backoff time, e.g., setting the backoff time to a reduced value, if the power of the received beacon signal is less than the second power level threshold  437 , and a module for controlling operation to not cancel transmission of the first beacon signal in response to the received beacon signal  438 . 
         [0054]    Assembly of modules  400  further includes a module for determining if a signal which exceeds a first power level threshold or is decodable is being received  440 , a mdoue for controlling operation as a function of the determination of a signal which exceeds a first power threshold or is decodable is being received  441 , a module suspending reduction of said backoff time during receipt of a signal which exceeds the first power level threshold or is decodable by the communications device  442  and a module for reducing the backoff time at a predetermined rate during said first beacon slot during time when a signal which exceeds a first power threshold or is decodable by the communications device is not being received  444 . Assembly of modules  400  further includes a module for monitoring to detect if a backoff timer has expired with the first beacon slot,  448 , a module for determining if the intended transmission of the first beacon signal has already been cancelled  454 , a module for controlling operation as a function of the determination if the intended transmission of the first beacon signal has already been cancelled  455 , a module for controlling the communications device to refrain from transmitting the first beacon signal  456 , a module for transmitting the first beacon signal if said backoff time expires during said first beacon slot  458  and a module for canceling transmission of the first beacon signal if the backoff time does not expire within said first beacon slot  460 . Module  448  includes a module for determining if the backoff timer has expired  450 , a module for controlling operation as a function of the determination if the backoff timer has expired  451 , a module for determining if the first beacon slot has ended  452 , and a module for controlling operation as a function of the determination if the first beacon slot has ended  453 . 
         [0055]      FIGS. 5-12  illustrates several examples to which illustrate various features and/or aspects of some embodiments. Drawing  500  of  FIG. 5  illustrates an exemplary peer to peer wireless terminal A  504  determining a backoff time, used to control transmission of a beacon signal, based on information corresponding to received beacon signals from a prior beacon slot in accordance with an exemplary embodiment. Drawing  502  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). Wireless terminals ( 502 ,  504 ,  506 ,  508 ,  510 ,  512 ,  514 ) are, e.g., any of the peer to peer wireless terminal of system  100  of  FIG. 1  and/or a wireless communications device implementing a method in accordance with flowchart  200  of  FIG. 2  and/or a wireless communications device implemented in accordance with device  300  of  FIG. 3  and/or including the assembly of modules  400  of  FIG. 4 . 
         [0056]    WT B  506  generates and transmits beacon signal  516  including time stamp TS B1    518 . WT A receives beacon signal  516  and determines that TS B1  indicates an earlier time than the time indicated by the clock of WT A at the time of receipt of beacon signal  516  communicating time stamp TS B1    518 , as indicated by box  520 . 
         [0057]    WT C  508  generates and transmits beacon signal  522  including time stamp TS C1    524 . WT A receives beacon signal  522  and determines that TS C1  indicates an earlier time than the time indicated by the clock of WT A at the time of receipt of beacon signal  522  communicating time stamp TS C1    524 , as indicated by box  526 . 
         [0058]    WT D  510  generates and transmits beacon signal  528  including time stamp TS D1    530 . WT A receives beacon signal  528  and determines that TS D1  indicates a later time than the time indicated by the clock of WT A at the time of receipt of beacon signal  528  communicating time stamp TS D1    530 , as indicated by box  532 . 
         [0059]    WT F  514  generates and transmits beacon signal  534  including time stamp TS F1    536 . WT A receives beacon signal  534  and determines that TS F1  indicates an earlier time than the time indicated by the clock of WT A at the time of receipt of beacon signal  534  communicating time stamp TS F1    536 , as indicated by box  538 . 
         [0060]    WT A  504  determines that a majority of time stamps received in beacon signals, e.g., 3 out of 4 in this example, indicate an earlier time than a time indicated by the clock of WT A at the time of receipt of the beacon signals, as indicated by box  540 . In response to the determination of step  540 , wireless terminal A  504  increases a probability that a short backoff time will be determined, as indicated by box  542 . Wireless terminal A  504  determines a backoff time to be used for a subsequent beacon slot using the probability adjustment of box  542 , as indicated in box  544 . 
         [0061]    Drawing  550  of  FIG. 5  illustrates an exemplary subsequent beacon slot  552 , a range of backoff time values that may be selected for the initial backoff time value  554  and an exemplary determined initial backoff time value  556  corresponding to the determination of step  544 . 
         [0062]    Drawing  600  of  FIG. 6  illustrates an exemplary peer to peer wireless terminal A  504  determining a backoff time, used to control transmission of a beacon signal, based on information corresponding to received beacon signals from a prior beacon slot in accordance with an exemplary embodiment. Drawing  602  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0063]    WT B  506  generates and transmits beacon signal  616  including time stamp TS B1    618 . WT A receives beacon signal  616  and determines that TS B1  indicates a later time than the time indicated by the clock of WT A at the time of receipt of beacon signal  616  communicating time stamp TS B1    618 , as indicated by box  620 . 
         [0064]    WT C  508  generates and transmits beacon signal  622  including time stamp TS C1    624 . WT A receives beacon signal  622  and determines that TS C1  indicates a later time than the time indicated by the clock of WT A at the time of receipt of beacon signal  622  communicating time stamp TS C1    624 , as indicated by box  626 . 
         [0065]    WT D  510  generates and transmits beacon signal  628  including time stamp TS D1    630 . WT A receives beacon signal  628  and determines that TS D1  indicates an earlier time than the time indicated by the clock of WT A at the time of receipt of beacon signal  628  communicating time stamp TS D1    630 , as indicated by box  632 . 
         [0066]    WT F  514  generates and transmits beacon signal  634  including time stamp TS F1    636 . WT A receives beacon signal  634  and determines that TS F1  indicates a later time than the time indicated by the clock of WT A at the time of receipt of beacon signal  634  communicating time stamp TS F1    636 , as indicated by box  638 . 
         [0067]    WT A  504  determines that a majority of time stamps received in beacon signals, e.g., 3 out of 4 in this example, do not indicate an earlier time than a time indicated by the clock of WT A at the time of receipt of the beacon signals, as indicated by box  640 . In response to the determination of step  640 , wireless terminal A  504  decreases a probability that a short backoff time will be determined, as indicated by box  642 . Wireless terminal A  504  determines a backoff time to be used for a subsequent beacon slot using the probability adjustment indicated in step  642 , as indicated in box  644 . 
         [0068]    Drawing  650  of  FIG. 6  illustrates an exemplary subsequent beacon slot  552 , a range of backoff time values that may be selected for the initial backoff time value  554  and an exemplary determined initial backoff time value  656  corresponding to the determination of step  644 . 
         [0069]      FIG. 5  and  FIG. 6  may correspond to different examples, e.g., different iterations, of executing steps  204  and  206  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0070]    Drawing  700  of  FIG. 7  illustrates an exemplary peer to peer wireless terminal A  504  determining a backoff time, used to control transmission of a beacon signal, based on whether or not WT A  504  transmitted a beacon in an immediately preceding beacon slot in accordance with an exemplary embodiment. Drawing  702  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0071]    WT B  506  generates and transmits beacon signal  716  including time stamp TS B1    718 . WT A  504  generates and transmits beacon signal  722  including time stamp TS A1    724 , as indicated by block  720 . WT A  504  stores information indicating that it has transmitted a beacon signal during this beacon slot, as indicated by block  726 . WT D  510  generates and transmits beacon signal  728  including time stamp TS D1    730 . WT A  504  increases a probability that a short backoff time will be determined for the immediate subsequent beacon slot in response to WT A having transmitted a beacon signal, as indicated by block  732 . Wireless terminal A  504  determines a backoff time to use as an initial backoff time value for an immediate subsequent beacon slot based on increase in probability of step  732 , as indicated in block  734 . 
         [0072]    Drawing  750  of  FIG. 7  illustrates an exemplary immediate subsequent beacon slot  752 , a range of backoff time values that may be selected for the initial backoff time value  754  and an exemplary determined initial backoff time value  756  corresponding to the determination of step  734 . 
         [0073]    Drawing  800  of  FIG. 8  illustrates an exemplary peer to peer wireless terminal A  504  determining a backoff time, used to control transmission of a beacon signal, based on whether or not WT A  504  transmitted a beacon in an immediately preceding beacon slot in accordance with an exemplary embodiment. Drawing  802  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0074]    WT B  506  generates and transmits beacon signal  816  including time stamp TS B1    818 . WT D  510  generates and transmits beacon signal  820  including time stamp TS D1    822 . WT A  504  detects that the beacon slot has ended and WT A  504  has not transmitted a beacon signal, as indicated by block  828 . WT A  504  stores information indicating that it has not transmitted a beacon signal during the beacon slot, as indicated by block  830 . WT A  504  increases a probability that a long backoff time will be determined for the immediate subsequent beacon slot in response to WT A not having transmitted a beacon signal, as indicated by block  832 . Wireless terminal A  504  determines a backoff time to use as an initial backoff time value for an immediate subsequent beacon slot based on probability adjustment of step  832 , as indicated in block  834 . 
         [0075]    Drawing  850  of  FIG. 8  illustrates an exemplary immediate subsequent beacon slot  752 , a range of backoff time values that may be selected for the initial backoff time value  754  and an exemplary determined initial backoff time value  856  corresponding to the determination of step  834 . 
         [0076]      FIG. 7  and  FIG. 8  may correspond to different examples, e.g., different iterations, of executing steps  206  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0077]    Drawing  900  of  FIG. 9  illustrates an exemplary peer to peer wireless terminal A  504  reducing its current value of its backoff time value in response to detecting a beacon signal from another wireless terminal with characteristics that satisfies particular criteria in accordance with an exemplary embodiment. Drawing  900  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0078]    WT B  506  generates and transmits beacon signal  902  including time stamp TS B1    904 . WT A  504  detects receipt of beacon signal  902  from WT B  506 , as indicated by block  906 . WT A  504  compares the indicated time in the received beacon from WT B, e.g., the time indicated in time stamp TS B1    904 , to a time indicated at the time of receipt of beacon signal  902  by the clock of WT A  504 , as indicated by block  908 . In this example, WT A  504  determines that the comparison indicates that the time indicated in the received beacon signal is less than the time indicated by the clock of WT A  504 , as indicated by block  910 . WT A  504  sets the current value of its backoff time value to a reduced value in response to the determination of step  910 , as indicated in block  912 . 
         [0079]      FIG. 9  may correspond to an example of executing steps  218 ,  220 ,  222 ,  224 ,  226  and  228  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0080]    Drawing  1000  of  FIG. 10  illustrates an exemplary peer to peer wireless terminal A  504  cancelling an intended beacon signal transmission in response to detecting a beacon signal from another wireless terminal with characteristics that satisfies particular criteria in accordance with an exemplary embodiment. Drawing  1000  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0081]    WT F  514  generates and transmits beacon signal  1002  including time stamp TS F1    1004 . WT A  504  detects receipt of beacon signal  1002  from WT F  514 , as indicated by block  1006 . WT A  504  compares the indicated time in the received beacon from WT F, e.g., the time indicated in time stamp TS F1    1004 , to a time indicated at the time of receipt of beacon signal  902  by the clock of WT A  504 , as indicated by block  1008 . In this example, WT A  504  determines that the comparison indicates that the time indicated in the received beacon signal is greater than the time indicated by the clock of WT A  504 , as indicated by block  1010 . WT A  504  updates the time indicated by the clock of WT A to match the time indicated by the received beacons signal, as indicated by block  1012 . Thus WT A synchronizes to the faster clock of WT F. 
         [0082]    WT A  504  compares the power of the received beacon from WT A to a second power level threshold, as indicated in block  1014 . In this example, WT A determines that the comparison indicates the power of the received beacon signal exceeds the second power level threshold, as indicated by block  1016 . In response to the determination that the comparison indicates that the power level of the received beacon signals exceeds the second power level threshold, WT A cancels the intended beacon signal transmission from WT A during this current beacon slot, as indicated by block  1018 . 
         [0083]      FIG. 10  may correspond to an example of executing steps  218 ,  220 ,  222 ,  224 ,  226 ,  230 ,  232 ,  234  and  236  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0084]    Drawing  1100  of  FIG. 11  illustrates an exemplary peer to peer wireless terminal A  504  transmitting an intended beacon signal transmission in response to detecting that its backoff timer has expired within the current beacon slot in accordance with an exemplary embodiment. Drawing  1100  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0085]    WT A  504  detects that its backoff timer has expired, e.g., its backoff time value has counted down to a value of zero, and the beacon slot has not yet ended and the intended beacon transmission from WT A has not been cancelled, as indicated by block  1102 . WT A  504  generates and transmits beacon signal  1106  communicating time stamp TS A1    1108 . The transmitted beacon signal  1106  may be received and processed by the other wireless terminals in the network ( 506 ,  508 ,  510 ,  512 ,  514 ) which may also be implementing a method in accordance with flowchart  200  of  FIG. 2 . 
         [0086]      FIG. 11  may correspond to an example of executing steps  248 ,  250 ,  252 ,  254 , and  258  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0087]    Drawing  1200  of  FIG. 12  illustrates an exemplary peer to peer wireless terminal A  504  cancelling an intended beacon signal transmission in response to detecting that the current beacon slot has expired in accordance with an exemplary embodiment. Drawing  1200  illustrates an exemplary peer to peer network, e.g., an ad hoc peer to peer network, including a plurality of peer to peer wireless terminals (peer to peer wireless terminal A  504 , peer to peer wireless terminal B  506 , peer to peer wireless terminal C  508 , peer to peer wireless terminal D  510 , peer to peer wireless terminal E  512 , peer to peer wireless terminal F  514 ). 
         [0088]    WT A  504  detects that the current beacon slot has ended and its backoff timer has not expired, as indicated by block  1202 . WT A cancels transmission of its intended beacon signal in response to the beacon slot ending, as indicated in block  1204 . The current backoff time value of WT is not carried over to the next beacon slot in this embodiment, as indicated by block  1206 . 
         [0089]      FIG. 12  may correspond to an example of executing steps  248 ,  250 ,  252 , and  260  of flowchart  200  where exemplary peer to peer wireless terminal A  504  is implementing the method of flowchart  200  of  FIG. 2 . 
         [0090]    Various features and/or aspects of some, but not necessarily all embodiments, will be further discussed. In various embodiments distributed synchronization is achieved without infrastructure, e.g., without a base station or central control node. Various embodiments are well suited for use in social WiFi applications for achieving synchronization between devices. Various benefits over existing approaches to synchronization include, e.g., power savings and/or collision avoidance between discovery messages. Some embodiments offer improvements over a current 802.11 synchronization protocol. Some deficiencies of current 802.11 synchronization protocol include slow dissemination of clock in the presence of multi-hop and no way to measure clock rates. 
         [0091]    In some exemplary embodiments there can be, and sometimes are, multiple winners per beacon election, e.g., multiple wireless communications device may transmit their beacon used for timing synchronization during the same beacon slot. Various exemplary methods and apparatus are directed to determining the winners, e.g., determining whether a particular wireless communications device transmits its beacon signal during a particular beacon slot, e.g., based on the characteristics of received beacon signals from other devices. In various embodiments, priority to beacon transmission is given to a previous winner to facilitate clock skew estimation. For example, in some embodiments the exemplary method increases the probability that a wireless communications device which has transmitted a beacon in a first beacon slot will transmit a beacon in a second beacon slot, where the first beacon slot is the beacon slot immediately preceding the second beacon slot. Successive beacon signal transmission from the same wireless communications device during two successive beacon slots facilitates clock skew estimation by the other devices receiving the two beacon signals. 
         [0092]    In various embodiments, the feature of allowing multiple winners per beacon slot facilitates faster dissemination of timing synchronization over an approach where one beacon is allowed to transmit in a beacon slot. Thus in various embodiments, multiple wireless communications devices may, and sometimes do, transmit a beacon in the same beacon slot even if they detect a beacon from another device. 
         [0093]    In some embodiments, a wireless communications device is a client station (STA). In some embodiments, for a beacon slot, each client station (STA) initially selects a backoff used in controlling transmission of beacon signal during the beacon slot, e.g., a pseudo-random backoff. Consider the operations of an individual STA. In some embodiments, if the STA receives a beacon before the timer expires, the STA performs one of: (i) cancelling transmission of its intended beacon, (ii) keeping the back-off as it is, or (iii) reducing its current back-off value, depending upon characteristics of the received beacon signal. The STA cancels the intended beacon transmission if the T(beacon)&gt;T(STA) and the beacon power of the received beacon is greater than a threshold, where T(beacon) is a time indicated in the received beacon and T(STA) is a time indicated at the time of receipt of the received beacon by a clock of the STA receiving the beacon. The STA keeps the back off as is if the T(beacon)&gt;T(STA) and the beacon power is less than the threshold. The STA reduces the back off if the T(beacon)&lt;T(STA), since in this case the STA is faster than the beacon. In this situation it is desirable that the STA be able to transmit its beacon in the current beacon slot and by reducing the current backoff time value of the STA, the probability that the STA will transmit its beacon in the current beacon slot is increased. In some embodiments, the amount of the reduction in the backoff is a function of the time difference between T(beacon) and T(STA), e.g., the larger the time difference the higher the amount of reduction in the current backoff time value of STA in response to the detected beacon. Step  222  of flowchart  200  of Figure illustrates an exemplary method that is used by a wireless communications device, e.g., a STA, in some embodiments, to respond to a detected beacon signal. 
         [0094]    In various embodiments, one goal of the synchronization is to converge to the fastest clock. In some such embodiments, the exemplary method prioritizes successive transmissions from fast clocks to facilitate skew estimation. In one exemplary embodiment, a STA determines if it has a fast clock, e.g., based on the time adjustments that the STA needs to make. In some embodiments, an STA considers that it has a fast clock if the STA wins beacon election for beacon slot t and does not adjust its time, e.g., transmits a beacon in beacon slot t and does not adjust its time based on received beacons from other devices in beacon slot t. Then the STA contends in beacon slot t+1 with a short backoff time. Thus, a short backoff time is selected for the next successive beacon slot increasing the likelihood that the STA will transmit a beacon in beacon slot t+1. Step  210  of flowchart  200  of  FIG. 2  illustrates an example of this approach. In some embodiments, the STA defaults back to a standard protocol for beacon slot t+2, e.g., the increase in priority resulting in a lower backoff time for slot t+1 is not applicable to slot t+2, even if the STA has transmitted a beacon in slot t+1 and has not adjusted its timing based on received beacons from other devices in slot t+1. 
         [0095]    In various embodiments a device, e.g., a peer to peer wireless communications device in system  100  of  FIG. 1 , and/or communication device  300  of  FIG. 3 , and/or one of the wireless terminals ( 506 ,  508 ,  510   512 ,  514 ) or  FIGS. 5-12  includes a module corresponding to each of the individual steps and/or operations described with regard to any of the Figures in the present application and/or described in the detailed description of the present application. In some embodiments, the modules are implemented in hardware, e.g., in the form of circuits. Thus, in at least some embodiments the modules may, and sometimes are implemented in hardware. In other embodiments, the modules may, and sometimes are, implemented as software modules including processor executable instructions which when executed by the processor of the communications device cause the device to implement the corresponding step or operation. In still other embodiments, some or all of the modules are implemented as a combination of hardware and software. 
         [0096]    The techniques of various embodiments may be implemented using software, hardware and/or a combination of software and hardware. Various embodiments are directed to apparatus, e.g., network nodes, mobile nodes such as mobile terminals supporting peer to peer communications, access points such as base stations, and/or communications systems. Various embodiments are also directed to methods, e.g., method of controlling and/or operating network nodes, mobile nodes, access points such as base stations and/or communications systems, e.g., hosts. Various embodiments are also directed to machine, e.g., computer, readable medium, e.g., ROM, RAM, CDs, hard discs, etc., which include machine readable instructions for controlling a machine to implement one or more steps of a method. The computer readable medium is, e.g., non-transitory computer readable medium. 
         [0097]    It is understood that the specific order or hierarchy of steps in the processes disclosed is an example of exemplary approaches. Based upon design preferences, it is understood that the specific order or hierarchy of steps in the processes may be rearranged while remaining within the scope of the present disclosure. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented. 
         [0098]    In various embodiments nodes described herein are implemented using one or more modules to perform the steps corresponding to one or more methods, for example, signal processing, signal generation and/or transmission steps. Thus, in some embodiments various features are implemented using modules. Such modules may be implemented using software, hardware or a combination of software and hardware. Many of the above described methods or method steps can be implemented using machine executable instructions, such as software, included in a machine readable medium such as a memory device, e.g., RAM, floppy disk, etc. to control a machine, e.g., general purpose computer with or without additional hardware, to implement all or portions of the above described methods, e.g., in one or more nodes. Accordingly, among other things, various embodiments are directed to a machine-readable medium, e.g., a non-transitory computer readable medium, including machine executable instructions for causing a machine, e.g., processor and associated hardware, to perform one or more of the steps of the above-described method(s). Some embodiments are directed to a device, e.g., communications node, including a processor configured to implement one, multiple or all of the steps of one or more methods of the invention. 
         [0099]    In some embodiments, the processor or processors, e.g., CPUs, of one or more devices, e.g., communications nodes such as network nodes, access nodes and/or wireless terminals, are configured to perform the steps of the methods described as being performed by the communications nodes. The configuration of the processor may be achieved by using one or more modules, e.g., software modules, to control processor configuration and/or by including hardware in the processor, e.g., hardware modules, to perform the recited steps and/or control processor configuration. Accordingly, some but not all embodiments are directed to a device, e.g., communications node, with a processor which includes a module corresponding to each of the steps of the various described methods performed by the device in which the processor is included. In some but not all embodiments a device, e.g., a communications node, includes a module corresponding to each of the steps of the various described methods performed by the device in which the processor is included. The modules may be implemented using software and/or hardware. 
         [0100]    Some embodiments are directed to a computer program product comprising a computer-readable medium, e.g., a non-transitory computer-readable medium, comprising code for causing a computer, or multiple computers, to implement various functions, steps, acts and/or operations, e.g. one or more steps described above. Depending on the embodiment, the computer program product can, and sometimes does, include different code for each step to be performed. Thus, the computer program product may, and sometimes does, include code for each individual step of a method, e.g., a method of controlling a communications device or node. The code may be in the form of machine, e.g., computer, executable instructions stored on a computer-readable medium, e.g., a non-transitory computer-readable medium, such as a RAM (Random Access Memory), ROM (Read Only Memory) or other type of storage device. In addition to being directed to a computer program product, some embodiments are directed to a processor configured to implement one or more of the various functions, steps, acts and/or operations of one or more methods described above. Accordingly, some embodiments are directed to a processor, e.g., CPU, configured to implement some or all of the steps of the methods described herein. The processor may be for use in, e.g., a communications device or other device described in the present application. 
         [0101]    Various embodiments are well suited to communications systems using a peer to peer signaling protocol. Some embodiments use an Orthogonal Frequency Division Multiplexing (OFDM) based wireless peer to peer signaling protocol, e.g., WiFi signaling protocol or another OFDM based protocol. 
         [0102]    While described in the context of an OFDM system, at least some of the methods and apparatus of various embodiments are applicable to a wide range of communications systems including many non-OFDM and/or non-cellular systems. 
         [0103]    Numerous additional variations on the methods and apparatus of the various embodiments described above will be apparent to those skilled in the art in view of the above description. Such variations are to be considered within the scope. The methods and apparatus may be, and in various embodiments are, used with Code Division Multiple Access (CDMA), OFDM, and/or various other types of communications techniques which may be used to provide wireless communications links between communications devices. In some embodiments one or more communications devices are implemented as access points which establish communications links with mobile nodes using OFDM and/or CDMA and/or may provide connectivity to the internet or another network via a wired or wireless communications link. In various embodiments the mobile nodes are implemented as notebook computers, personal data assistants (PDAs), or other portable devices including receiver/transmitter circuits and logic and/or routines, for implementing the methods.