EP1240769A2

EP1240769A2 - Time synchronization in a cellular network device

Info

Publication number: EP1240769A2
Application number: EP00988233A
Authority: EP
Inventors: Murtuza Chhatriwala; Christine Park; Clarence Wong; Jason B. Kenagy; Weining Ruan
Original assignee: Qualcomm Inc
Current assignee: Qualcomm Inc
Priority date: 1999-12-21
Filing date: 2000-12-20
Publication date: 2002-09-18
Also published as: JP2004501523A; WO2001047220A2; WO2001047220A3; CN1460354A; AU2446201A; KR20020065586A

Abstract

A method and system (28c-28f) are provided to synchronize a digital communications device (27) with a mobile phone network system time. Previous reference times, associated with the device, are updated to the system time when the device is activated and the updated time is presented to a system user (28c). The updated time may also be used to automatically update the time associated with time-sensitive data files stored in the device's memory (28e). Finally, the user is permitted to set the system time to any desired time using a manual operation mode (28d).

Description

TIME SYNCHRONIZATION IN A CELLULAR NETWORK

DEVICE

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to the field of wireless communications. More particularly, the present invention relates to a novel system that automatically provides synchronization time to a digital device configured to receive data transmitted across a wireless communications network.

Description of the Related Art

With the integration of mobile telephones and personal digital assistants

(PDAs), it has become important to synchronize the operation, and thus the timing, between these two devices. PDAs come in a variety of forms and are essentially pocket computers. Recent technological advances have increased their processing capability, functionality, and storage capacity, so that they rival many lap-top computers. Users increasingly rely on these devices to supplement or replace many activities reserved for their much larger personal computers.

Moreover, the proliferation of mobile phones and an exponentially- increasing reliance on the Internet has accelerated the integration and interoperability of these devices. Now that mobile phones and PDAs exist in one integrated package, it is critical that the operability, as well as the time reference for these devices, be automated and synchronized. That is, a person using a mobile phone needs the ability to be automatically presented with a standardized time reference, based on their time zone reference, and be able to update or synchronize the operation of their PDA in accordance with the time zone reference. The component that makes such an accomplishment possible is the mobile phone system.

Mobile phones have become an integral component of the telecommunications industry. The most advanced and most widely used form of mobile communications is the cellular network system 1, as illustrated in FIG. 1. A cellular network is defined as a mobile communications system, which divides its coverage area into contiguous geographic areas referred to as cell grids 11, 13, 15. Each ^rid services a specific geographic region within the network, includes one base station (BS) 5, 7, 9. BSs consist of, among other components, a processor, a receiver, and a transmitter (not shown) and function like a repeater, receiving calls from users and passing the received calls to other users within the grid or passing the calls to a land line. A mobile switching center (MSC) 3 controls the operation the BSs 5, 7, 9 and provides the wireless cellular network with an interface to the public switched telephone network (PSTN) 4. Thus, each grid within the network is capable of separately handling a large number of individual users 15, 17 19, 21, but is somewhat limited in the number of users based upon its call handling capacity. As a user travels from one cell to another, the processing of that user's phone call is transitioned to the nearest BS, such as the example of user 19.

While positioned within cell 11, all calls placed or received by user 19, will be processed by BS 5. As long as user 19 remains within the geographic boundaries of cell 11 as indicated at position A, the processing of his phone call will remain at BS 5. However, as user 19 travels and approaches the boundary of cell Imposition B), the processing of his phone call will be transitioned to the next nearest BS. In the present example, the nearest BS becomes BS 7 of the new cell 13, as user 19 travels in the direction from B to C. These cell to cell handoffs are what provide cellular networks with increased traffic handling traffic capacity since the total system capacity is divided between a number of different BSs.

Cellular system service providers are limited in the amount of the frequency spectrum that can be devoted to cellular communications. Therefore, as the number of cellular users has increased, the cellular industry has been forced to explore different alternatives to increasing capacity beyond increasing the available frequency spectrum. Among these alternatives is the Code Division Multiple Access (CDMA) technology. CDMA is a digital radio- frequency (RF) channelization technique defined in the Telecommunications Industry Association/Electronics Industries Association Interim Standard-95 (TIA/EIA IS-95), entitled "MOBILE STATION-BS COMPATIBILITY STANDARD FOR DUAL-MODE WIDEBAND SPREAD SPECTRUM CELLULAR SYSTEM", published in July 1993 and herein incorporated by reference. Wireless communication systems employing this technology assign a unique code to communication signals and spread these communication signals across a common (wideband) spread spectrum bandwidth. As long as the receiving apparatus in a CDMA system has the correct code, it can successfully detect and select its communication signal from the other signals concurrently transmitted over the same frequency band. The use of CDMA produces an increase in system traffic capacity, improves overall call quality and noise reduction, and provides a reliable transport mechanism for data service traffic. An important component of the CMDA system that makes the aforementioned time synchronization possible, is the CDMA system time.

In CDMA digital systems, all BS transmissions are time synchronized based upon a common CDMA system time. CDMA system time is referenced to the Greenwich Mean Time (GMT) time scale. The CDMA system time is used to synchronize the timing of all network signals and operations. While mobile phones currently process signals that are encoded with the system time, currently this time is not presented to the user in any meaningful or usable manner.

What is therefore needed is a system that provides the CDMA system time in order to synchronize the operations and timing between a PDA and a mobile phone. If provided, a system or method using this time could inform the user of the current time, within the accuracy of the GMT time standard. Additionally, such a system or method could provide the user with a number of referenced time choices, for example time referenced to different time zones, to choose from. The user would then set their mobile phone to a local time in accordance with the time zone selected from the provided options. In systems where the mobile phone and the PDA are integrated into a single unit, this same system time could be used, for example, to update files, appointments, calendars, or other time specific data in the PDA.

SUMMARY

The present invention addresses the needs identified above by providing a system, apparatus, and method that recognizes a mobile phone's network system time and provides this time to a user. According to the present invention, an apparatus including a portable digital device is provided. The portable device is associated with a previous local time and adapted to receive a time-encoded signal transmitted across a cellular network, which represents a network system time. The device receives the signal when the device is activated. The apparatus also includes a deriving mechanism for deriving the system time from the received signal and a converter for converting the system time to a current local time. Finally, the apparatus includes an updating mechanism for updating the previous local time to the current local time and a conveying mechanism for conveying the current local time to a user. BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and, together with the general description given above and the detailed description of the embodiments given below, serve to explain the principles of the invention. FIG. 1 is a chart illustrating a basic structure of a cellular network. FIG. 2 illustrates a single cellular phone receiving transmission of a pilot signal from a BS.

FIG. 3 is an illustration of a typical mobile phone FIG. 4 is an illustration of a PDA.

FIG. 5 illustrates a mobile phone and a PDA integrated into a single device and exemplary user modes. FIG. 5B illustrates a block diagram of the integrated device of FIG. 5.

FIG. 6A is a flow chart of an embodiment an automatic mode of the present invention.

FIG. 6B is a flow chart of an embodiment of the data base update mode of the present invention. FIG. 6C is a flow chart of an embodiment of the manual mode of operation.

FIG. 7 shows the integrated device of FIG. 4 displaying an appointment list.

FIG. 8 is an illustration of typical time zone options presented to a user.

DETAILED DESCRIPTION

As stated above, FIG. 1 illustrates a typical cellular network configuration. In such a configuration, when user 19 first activates his mobile phone, the phone transmits a series of signals, which serve to broadcast to the cellular network 1, a request to receive or transmit a call. Also transmitted is the mobile phone's identification and the location of the caller. The signal is received by each BS that is close enough to receive the signal, based upon the signal's strength. At the same time, the BS(s) 5, 7, 9 continuously transmit a beacon signal, referred to as a pilot signal, which serves to notify potential users that the system is available and ready for use. Once the user's transmitted signal is received by the BS(s) 5, 7, 9 and the information contained in the signal is authenticated, the mobile phone is allowed to receive and process the pilot signal from the nearest BS. The mobile phone measures the signal strength of the incoming calls and, generally the BS transmitting the strongest signal is determined by the mobile phone to be the closest BS.

FIG. 2 depicts transmission of a pilot signal by a BS. Specifically, pilot signals 29 are transmitted from all of the BSs of a CDMA cellular system and are identical to one another except for the phase of the signal. A portion of the information contained in the pilot signal 29 is the CDMA system time 29a. As addressed earlier, the CDMA system time 29a is based upon the GMT time standard. Present cellular systems use this system time for system operation, billing, etc. The use of CDMA system time is transparent to the user of an exemplary device, such as device 23.

FIGs. 3 and 4 illustrate a typical mobile phone 23 and PDA 25, respectively. A user of a PDA device does not have access to an external time source. The PDA 25 has an internal clock which is set by the user and does not change unless modified by the user. The PDA 25 may contain information such as calendars and schedules which are time dependent and must be manually updated by the user. More recent devices, such as the device 27 of FIG. 5, integrate both the mobile phone 23 and the PDA 25 into a single unit, such as, for example, the Qualcomm Corporation's pdQ series. The integrated device 27 of FIG. 5 includes a PDA portion 27a and a mobile phone portion 27b. This integrated device 27 may provide a user with the benefit of automatic real-time time displays based upon CDMA, or other similar system wide time scales, in order to facilitate seamless functionality between mobile 23 phone and the PDA device 25. FIG. 5 also illustrates several exemplary modes of operations of integrated device 27. FIG. 5B illustrates a block diagram of the integrated device 27.

FIG. 6A depicts an exemplary embodiment of the present invention implemented in an automatic operational mode 28c of integrated device 27, as shown in FIG. 5. As indicated in block B40a, a user of integrated device 27 must first activate the device. When activated, pilot signal 29 may be received, as indicated in block B40a, by a processor of the mobile phone (not shown).

After receiving the pilot signal and activating the integrated device 27, the system time is derived using a deriving mechanism 27c and as indicated in block B40b. Because additional information is encoded in the pilot signal, the system time may be derived by extracting and separating the time information from the other informational components of the signal.

After deriving the system time, a converter 27d converts the system time to a local time as indicated in block B40c. The local time includes the system time converted to the use r's correct local time, i.e. the user's local time zone 40c. This conversion is done in accordance with the GMT reference time and using a time zone offset. For example, for a user in Illinois, the CDMA system time 29a is 6 hours behind GMT, see e.g. 31 of FIG. 8. Similarly, a user in Australia is 11 hours ahead of GMT. Thus, in order for the system to convey the correct local time, the CDMA system time 29a is converted to the local time zone by using these previously mentioned offsets.

Upon converting system time to local time, local time is conveyed to the user in block B40e via a conveying mechanism 27i. The conveying of local time may include, for example, displaying the local time at a fixed portion of the user interface display of the integrated device 27. Upon conveying the local time, the automatic mode of operation 28c of the integrated device 27 terminates in block B40i.

FIG. 6B describes a database mode of operation 28e of integrated device 27, as shown in FIG. 5. This mode provides the user with an ability to manage the data stored in the PDA portion 27a of the integrated device 27. This feature is important because the user may have time dependant information 25b, such as appointments, and /or calendars (shown in FIG. 7), stored in the PDA portion 27a of the integrated device 27. As shown in FIG. 6B, blocks B42a, B42b, and B42c, are similar to blocks

B40a, B40b, and B40c of the automatic mode of operation, depicted in FIG. 6A. As such, upon converting the system time to local time, a comparator 27e compares a previous system time, stored in a memory block B42h, with a previous time, as indicated by block B42d. This previous time is updated, using an updating mechanism 27f to the current local time if the comparison of block B42d indicates that the previous time is different from the current local time of block B42e. This comparison is necessary because the user may have traveled to a time zone different than the zone the user was in the last time the phone was activated. The user may have thus entered time sensitive data into the PDA portion of the integrated device 27a which may be incorrect in the new time zone. As such, the comparison in block B42d determines whether or not the previous time is different from the current local time.

If the previous time is the same as the current local time, the database mode of operation terminates in block B42i. If the previous time and the current local time are different, an alerting mechanism 27g alerts the user in block B42f. Once the user has been alerted, the user has the option of activating and associating mechanism 27h to associate/update the time-dependent information, of memory block B42h, to the current time, as indicated in block B42g. A number of different mode combinations can be produced from the database update feature, such as an automatic data update without notifying the user, or the complete de-selection of this feature entirely, as indicated in 28f . During de-selection, the time sensitive data is not updated. In an alternative implementation, the local time may be conveyed to in a manner similar to automatic operational mode's block B40e.

FIG. 6C describes a manual mode of operation of the integrated device 27. The manual mode permits a user to select, using a selector 27k, any desired time and have that time conveyed as the system time of the integrated device 27. The user, for example, may set the integrated device 27 time 5 minutes ahead of the system time or to any other desired setting. In this mode, the CDMA system time 29a is not used.

When activating the manual mode, the user activates the device in block B44a and selects the manual mode of operation as indicated in block B44b, selected for example, by choosing the manual mode of operation 28d, as indicated in FIG. 5. This selection would permit a presenting mechanism 27j to present the user with the list of time zone options 31, from which the user would merely select one of the time zones in block B44c. With a desired time zone selected, an entry mechanism would permit the user to enter the desired time in block B44d. Finally, the conveying mechanism 27i would convey the desired time to the user in block B44e and the process ends at block B44f.

From the invention thus described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.

WHAT IS CLAIMED IS:

Claims

1. A method for synchronizing time in a mobile communications device, the method comprising: receiving a time encoded signal, the signal being (i) transmitted across a cellular network and (ii) representative of a network system time; deriving the system time from the signal; converting the system time to a current local time; and conveying the current local time to a user.

2. A method for synchronizing time according to claim 1 further comprising: comparing the current local time with a previous time; updating the previous time to the current local time when the previous time and the current local time are different; alerting the user when updating the previous time; and updating data associated with the previous time to the current local time.

3. A method for synchronizing time according to claim 2, wherein the updating is automatic.

4. A method for synchronizing time according to claim 3, wherein the updating is based upon a user input.

5. A method for permitting a user to set a desired time for a mobile communications device, the method comprising: permitting a user to select a manual time entry mode; conveying to the user a number of time zone options when the manual mode is selected; and permitting the user to enter the desired time based on a selected one of the time zone options.

6. An apparatus comprising: a portable digital device associated with a previous local time and adapted to receive a time encoded signal, the signal being (i) transmitted across a cellular network and (ii) representative of a network system time, wherein the device receives the signal when the device is activated; a deriving mechanism for deriving the system time from the received signal; a converter for converting the system time to a current local time; and a conveying mechanism for conveying the current local time to a user.

7. An apparatus according to claim 6, further comprising: a memory for storing user data, the user data being associated with a previous time; a comparator for comparing the previous time with the current local time; an updating mechanism for updating the previous time to the current local time when the previous time and the current local time are different; an alerting mechanism for alerting the user when updating the previous time to the current local time; and an associating mechanism for associating the data with the current local time.

8. An apparatus for permitting a user to set a desired time for a mobile communications device, the apparatus comprising: a portable digital device adapted to receive manual time entry; a presenting mechanism for presenting a user with a number of time options related to the manual time; a selector for permitting the user to select one of the options; an entry mechanism for permitting the user to enter the time based on a selected one of the options; and a conveying mechanism for conveying the entered option as the desired time.