Abstract:
A method and apparatus for obtaining and maintaining accurate time. A preferred apparatus includes a dedicated timekeeping device, a time synchronization client, and an access point. The timekeeping device is adapted for counting local time. The time synchronization client is adapted to transmit a query signal for querying a time server over a network to cause the time server to provide a current server time. The access point is adapted for producing a wireless signal representative of the current server time for wireless transmission to the timekeeping device, for synchronizing the local time of the dedicated timekeeping device to the current server time.

Description:
FIELD OF INVENTION  
       [0001]     The present invention relates to a method and apparatus for obtaining and maintaining accurate time. More particularly, the invention relates to wirelessly synchronizing a dedicated timekeeping device, such as a wristwatch or household clock.  
       BACKGROUND OF THE INVENTION  
       [0002]     Timekeeping devices such as clocks and watches, including those that are quartz based, eventually drift from the correct time and often require resetting or synchronization with an accurate time source. It is inconvenient for the user to reset the time. Currently, there are radio-synchronized clocks and watches that include a radio receiver tuned to receive a wireless synchronization signal derived from an accurate remote timekeeping source.  
         [0003]     For example, an atomic clock is maintained in North America by the National Institute of Standards and Technology (“NIST”). NIST provides a time synchronization signal derived from the clock that is broadcast on a low frequency radio 60 kHz carrier for purposes of synchronizing remote clocks. Existing radio-synchronized timekeeping devices are designed to pick up this signal, and to automatically set their time to the accurate atomic clock.  
         [0004]     However, correct synchronization of a watch or clock requires good signal reception of the 60 kHz low-frequency signal, and good reception is not always possible. For example, reception can be hampered by the distance from the transmitter, the weather, the time of the day, the location of the timepiece in the building, obstacles in the reception path, interference reflection, etc., so that some areas cannot reliably receive the NIST signal, thereby preventing synchronization. Moreover, the signal may not be receivable outside continental North America. Also, the time period required to achieve correct synchronization can be undesirably long.  
         [0005]     Accordingly, there is a need for a method and apparatus for obtaining and maintaining accurate time, particularly for wirelessly synchronizing a dedicated timekeeping device, which solves the aforementioned problems and meets the aforementioned needs.  
       SUMMARY  
       [0006]     A preferred apparatus for obtaining and maintaining accurate time according to the present invention includes a dedicated timekeeping device, a time synchronization client, and an access point. The timekeeping device is adapted for counting local time. The time synchronization client is adapted to transmit a query signal for querying a time server over a network to cause the time server to provide a current server time. The access point is adapted for producing a wireless signal representative of the current server time for wireless transmission to the timekeeping device, for synchronizing the local time of the dedicated timekeeping device to the current server time.  
         [0007]     A preferred method for obtaining and maintaining accurate time according to the present invention includes querying a time server over a network to cause the time server to provide a current server time. The method further includes producing a wireless signal representative of the current server time. The method further includes transmitting the wireless signal to a dedicated timekeeping device adapted to count local time. The method still further includes synchronizing the local time of the dedicated timekeeping device to the current server time by use of the wireless signal. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  shows an exemplary apparatus for obtaining and maintaining accurate time according to the present invention.  
         [0009]      FIG. 2  shows a block diagram of a preferred embodiment of a dedicated timekeeping device portion of the apparatus of  FIG. 1  according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0010]     Referring to  FIG. 1 , an exemplary apparatus  10  for obtaining and maintaining accurate time according to the present invention is shown. The system  10  includes a timekeeping device  12  that keeps and displays time. The timekeeping device  12  establishes a wireless connection to a time server  14 , which provides accurate time information for resetting or synchronizing the timekeeping device.  
         [0011]     It should be understood throughout that the features described may be implemented by any standard means in software, hardware, or combination thereof. In the description to follow, a controller  11  ( FIG. 2 ) will be assumed for carrying out control functions in addition to the specific functions described. The controller  11  is preferably a processor that executes programs of instruction as described below, though it will be understood that any equivalent structure or structures could be used.  
         [0012]     The time server  14  obtains time information from a highly accurate time source, preferably, the atomic clock maintained by NIST. However, the time source may be any desired source of time information. The time server  14  is connected to a network  16  and transmits the time information over the network. In the preferred embodiment, the network is the Internet, and the time server is the NIST Internet Time Service (“ITS”). Updated time information can also be obtained from servers that are maintained by other timekeeping organizations without departing from the principles of the invention.  
         [0013]     The time information can be accessed from the ITS time server using various formats including the DAYTIME, TIME and NTP protocols. Alternatively, the time information can also be downloaded from the ITS web site which is located on the Internet.  
         [0014]     When queried, the time server  14  transmits time information over the network  16  to an access point  18  for access to the network  16  by the timekeeping device  12 . The access point  18  is connected to the network by a network access device  20 , which is coupled to the network. The network access device  20  can be a modem, an asymmetrical digital subscriber line (“ADSL”), or any other desired means for interconnecting the access point to the network without departing from the principles of the invention.  
         [0015]     An outstanding advantage of the system  10  is that the access point  18  provides a wireless interconnection between the device  12  and the time server  14 . The access point  18  has a transmitter/receiver pair T A /R A  for wirelessly communicating with the timekeeping device  12 . The timekeeping device has a corresponding transmitter/receiver pair T D /R D  for wirelessly communicating with the access point  18 . In particular, a time query signal S 1  is sent by the transmitter T D  of the timekeeping device to the receiver R A  of the access point  18 . Reciprocally, the time information obtained from the time server  14  is sent as a signal S 2  from the transmitter T A  of the access point to the receiver R D  of the timekeeping device  12 . The signals S 1  and S 2  can be encoded with a digital signal, which can be decoded by the receivers Alternatively, the signals S 1  and S 2  can be modulated with analog signals which are converted to digital signals by the receivers. The signals can be transmitted as infrared signals, radio signals, or other types of signal modalities without departing from the principles of the invention.  
         [0016]     The access point converts the signal S 1  to a “time query signal” appropriate for transmission by the network access device  20 , which subsequently transmits the time query signal over the network  16  to the time server  14 . For example, where the network access device is a wired device, the access point converts the signal S 1  from a wireless form to a time query signal form adapted to propagate over a wire.  
         [0017]     The access point  18  may provide for short-range wireless communications with the timekeeping device  12  such as Wi-Fi/802.11b or Bluetooth, or long-range wireless communications such as WMAN 802.16a. The access point may be either a general purpose access point such as a standard WiFi access point for use with a wireless PC, or a dedicated access point specifically for the purpose of communicating with the timekeeping device  12 . When providing for long-range communications, the access point may be located a long distance away from the timekeeping device  12 , such as outside, on a telephone pole or on top of a building.  
         [0018]     The time server answers the query represented by the signal S 1  by providing updated time information and transmits the updated information as a “time information signal” over the network  16 , through the network access device  20 , to the access point  18 . The access point  18  converts the time information signal to the wireless reply signal S 2  and the transmitter T A  transmits the signal S 2  to the timekeeping device  12 , where the reply signal S 2  is received by the receiver R D . Time information can include the time of day, date and day of the week or other information relating to the time or the calendar.  
         [0019]     As shown in  FIG. 2 , the timekeeping device  12  includes a clock  22 , which keeps or “counts” local time, and a display which displays the kept local time to a user. Like the time information, the time kept by the timekeeping device  12  includes the time of day, date and day of the week or other information relating to the time or the calendar. The term “local time” is intended herein to refer to the time kept locally, i.e., by the clock  22 , which typically is the time appropriate for the area in which the timekeeping device is located, but which may in the alternative or in addition include the time for other time zones.  
         [0020]     For setting, resetting or more generally synchronizing the system  10  includes a time synchronization client  24 , a configuration settings file  26 , a protocol converter  28  and a client hardware device  30 . The time synchronization client  24  includes a software application program, hardware, or combination of hardware and software as desired, having the capability of requesting updated time information from the time server  14 . A network address of the time server is stored in the configuration settings file  26 . In the preferred embodiment, the configuration settings file stores the IP address of a time server  14  that is located on the Internet. Preferably, the IP address of the time server  14  is preprogrammed into the configuration settings file  26 . The configuration settings file also stores time information such as time zone and whether it is day-light savings time. Additional information can be stored in the configuration settings file  26  without departing from the principles of the invention.  
         [0021]     The time synchronization client  24  obtains the IP address of the time server  14  from the configuration settings file  26  so that the time synchronization client can query the time server  14 . In the preferred embodiment, the request by the time synchronization client is sent to the time server  14  using the Transmission Control Protocol/Internet Protocol (“TCP/IP protocol”), which is the protocol used by the Internet. However, other protocols can be used without departing from the principles without departing from the principles of the invention. Because the time synchronization client does not itself format requests according to the TCP/IP format, the time synchronization client  24  passes its request to the protocol converter  28 . The protocol converter includes a software application program, hardware, or a combination of hardware and software as desired, that translates the request into the TCP/IP format. The protocol converter also converts responses received from the time server from the TCP/IP format into a format understood by the time synchronization client.  
         [0022]     The protocol converter  28  interfaces directly with the client hardware device  30 . As will be appreciated by one skilled in the art, the client hardware device typically includes a chip set including an analog-to-digital converter, a digital-to-analog converter, a transceiver, and logic necessary to enable communication according to a wireless protocol.  
         [0023]     The client hardware device  30  provides for wireless communication with the access point  18 . Particularly, the device  30  includes the transmitter/receiver pair T D /R D , for transmitting the signal S 1  and receiving the signal S 2 . Preferably, the client hardware device  30  conforms to a wireless local area network (“WLAN”) standard such as Wi-Fi/802.11b or 802.11g. However, other standards may be used such as Bluetooth and wireless metropolitan area network (“WMAN”) if desired.  
         [0024]     The timekeeping device  12  is dedicated to receive and display time information, and not other types of information. Preferred examples of such dedicated timekeeping devices are wrist watches and house-hold clocks. Preferably, the aforementioned time synchronization client  24 , configuration settings file  26 , protocol converter  28 , and client hardware device  30  are provided integrally with the timekeeping device  12 ; however, one or all of the synchronization client  24 , settings file  26 , converter  28 , and the transmitter portion T D  of the client hardware device  30  may be provided outside of the timekeeping device, such as at the access point  18 .  
         [0025]     The clock  22  can be battery operated, can plug into an electrical outlet, or can be powered in other ways without departing from the principles of the invention. The time display can be an analog dial, a digital display, any other kind of graphical display, a bit-mapped computer-style display or any other kind of display. The clock can be free standing, can attach to a wrist or other item, be built into another device, or attached to the wall, etc. without departing from the principles of the invention.  
         [0026]     Returning to  FIG. 1 , when the timekeeping device  12  decides to update the time, it transmits a wireless request via the access point  18  to the time server  14 . The time synchronization client  24  formulates the request and can be programmed to request time information every time a predetermined amount of time has passed. For example, the time synchronization client can be preprogrammed to request time information from the time server  14  every four hours, or once every week. Alternatively, the time keeping device  12  does not have to be preprogrammed and the times or time intervals for updating the time can be set by the user. The time synchronization client  24  receives the information regarding the IP address of the server from the configuration settings file  26 . The request is forwarded to the protocol converter  28  and formatted into the TCP/IP protocol. Next, the request is sent to the client hardware device  30 , where the request is wirelessly transmitted by the transmitter T D  to the access point  18 . As indicated above, the access point&#39;s receiver R A  receives the request and the access point&#39;s transmitter T A  transmits the request to the network access device  20 .  
         [0027]     The system  10  next awaits a reply to its request for updated time. If the system  10  receives a reply within a predetermined time, the system  10  updates the system time to that provided by the time server. For most practical purposes, it is of no concern that there is some delay in the time between sending the request and receiving an update for the time, because the delay is not very great. However, as will be appreciated by persons of ordinary skill, it is possible to account for the delay to varying degrees of precision if necessary.  
         [0028]     On the other hand, if the system  10  does not receive a reply from the time server within a predetermined period, the system  10  preferably refrains from updating the time. In addition, the system  10  may provide for one or more repeated re-tries spaced by predetermined periods.  
         [0029]     The time information received from the time server may need to be adjusted to provide a time appropriate for the local time zone in which the timekeeping device  12  is located. It should be understood that this is not essential; for example, it may be advantageous to require the user to set the hour and date while using the time server only to update the minutes and seconds, since these are most susceptible to drift. However, in most instances, adjusting the time information for the local time is desirable. This requires obtaining both the local time zone and the server time zone, i.e., the time zone for which the time information provided by the time server has been calibrated. For example, if the time server is set to provide time in Mountain Time, and the local time zone is Pacific Time, the time information may be adjusted to account for the 1 hour difference between Mountain Time and Pacific Time. A number of different strategies may be employed for providing the two time zones.  
         [0030]     One such strategy is to preprogram both time zones. According to this strategy, the timekeeping device would seek time information from a preprogrammed time server calibrated to a known time zone, and the timekeeping device would be used within a preprogrammed local time zone.  
         [0031]     Another strategy is to provide either or both time zones as a preprogrammed list of options from which the user may choose. The timekeeping device may include input devices such as a touch menu, dedicated buttons, switches, voice recognition software, etc., permitting the user to choose a desired set of preprogrammed options.  
         [0032]     Yet another strategy is to permit the user to enter either or both time zones directly using the same types of input devices. The aforementioned input devices may communicate with the processor  11 , which in turn may save input information such as time zone and standard/daylight savings indicators in the configuration settings file  26 . The processor  11  may also perform the time zone conversions. It may also be possible for the time server to perform a time zone calibration given the local time zone as a query input, in which case the time zone of the server need not be taken into account.  
         [0033]     At any time when the system  10  is not requesting and receiving time synchronization data, at least the time synchronization client  24 , configuration settings file  26 , the protocol converter  28 , and the client hardware device  30  can be powered down at the direction of the processor  11 . This feature is especially advantageous in a battery powered embodiment of the system  10 , such as a wristwatch, and is even more advantageous where updates are requested only infrequently. Preferably, the number of times the system  10  re-tries a failed request as mentioned above is balanced against the need to conserve power in battery-powered implementations.  
         [0034]     The terms and expressions that have been employed in the foregoing specification are used as terms of description and not of limitation, and are not intended to exclude equivalents of the features shown and described or portions of them. The scope of the invention is defined and limited only by the claims that follow.