Synchronizing a telecommunications connection in a mobile communications system

• US 6,144,656 A
• Filed: 04/14/1997
• Issued: 11/07/2000
• Est. Priority Date: 08/14/1995
• Status: Expired due to Term

• Current Assignee: Cassidian Finland OY
• Original Assignee: Nokia Telecommunications Oy (Nokia Corporation)
• Inventors: Schroderus, Osmo, Kinnunen, Kimmo
• Primary Examiner(s): Ngo, Ricky
• Assistant Examiner(s): NGUYEN, STEVEN H D
• Application Number:
  US08/817,951
• Time in Patent Office: 1,303 Days
• Field of Search: 370/311, 370/318, 370/319, 370/345, 370/347, 370/350, 370/336, 370/337, 455/38.3, 455/11.1, 455/574, 455/343, 455/553, 455/434, 455/515, 455/455, 455/509, 375/354, 375/362, 375/364, 375/369
• US Class Current: 370/347
• CPC Class Codes: H04B 7/2681 Synchronisation of a mobile station with one base station
• CPC Class Codes: H04W 52/0216 using a pre-established activity schedule, e.g. traffic indication frame
• CPC Class Codes: H04W 56/00 Synchronisation arrangements
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A method for synchronizing a telecommunications connection in a mobile communications system including a database, at least one base station communicating with mobile stations on system channels which include control channels and traffic channels. Mobile stations communicate with other mobile stations using the base station and the system channels or communicate directly using a direct mode channel. Time slots and frame structures of the system channels are synchronized with time slots and frame structures of the direct mode channels.

Claims

1. A method for synchronizing a telecommunications connection in a mobile communications system having

at least one base station communicating with mobile stations on time division multiple access system channels including of control channels and traffic channels whose uplink and downlink frequencies are divided into frames, a part of which may be defined dynamnically, by determining an energy economy mode start frame and length of an energy economy cycle, for a mobile station in the database as energy economy mode sleeping frames, during which the mobile station is not prepared to receive transmissions on downlink frequencies,

at least a first mobile station communicating on a direct mode channel divided into frames and predisposed to operate in a dual watch mode both on a control channel of the mobile communications system and on the direct mode channel which comprises pre-emption frames, by which the mobile stations communicating on the direct mode channel request transmission turns for themselves, the method comprising:

communicating from the at least first mobile station operating on the direct mode channel to the at least one base station a wish of the at least first mobile station to operate in the dual watch mode and to operate in an energy economy mode on the control channel of the mobile communications system;

checking from the database (i) whether the energy economy mode start frame has been determined for the direct mode channel and (ii) the length of the energy economy cycle if the energy economy mode start frame has been determined for the direct mode channel, the checking from the database in response to a registration message associated with the at least first mobile station;

determining and storing in the database the energy economy mode start frame and the length of the energy economy cycle wherein each of a number of pre-emption frames coincides with a corresponding number of sleeping frames of the energy economy mode, determining and storing if the energy economy mode start frame has not been determined for the direct mode channel;

transmitting to the at least first mobile station information on a desired control channel of the at least one base station and timing information related to the desired control channel, and transmitting a command to switch to the energy economy mode, the command containing information on the energy economy mode start frame and the length of the energy economy cycle; and

the at least first mobile station switching to the dual watch mode and to the energy economy mode, to communicate either on the direct mode channel or the control channel so that the at least first mobile station can listen to the control channel between transmission time-slots of the direct mode channel while communicating on the direct mode channel, the at least first mobile station switching in response to the information on the desired control channel, the timing information related to the desired control channel, the information on the energy economy mode start frame, and the length of the energy economy cycle.

2. A method as claimed in claim 1, further comprising:

communicating from a second mobile station operating on the direct mode channel to the at least one base station a wish of the second mobile station to operate in the dual watch mode and in the energy economy mode on the control channel of the mobile communications system;

checking from said database (i) whether an energy economy mode start frame has been determined for the direct mode channel and (ii) the length of an energy economy cycle if the energy economy mode start frame has been determined for the direct mode channel, the checking from the database in response to a registration message associated with the second mobile station;

transmitting to the second mobile station information on a desired control channel of the at least one base station and timing information related to the desired control channel, and transmitting a command to switch to the energy economy mode, the command containing information on the energy economy mode start frame and the length of the energy economy cycle, transmitting to the second mobile station if the energy economy mode start frame has been determined for the direct mode channel; and

the second mobile station switching to the dual watch mode and to the energy economy mode, to communicate either on the direct mode channel or the control channel so that the second mobile station can listen to the control channel between the transmission time-slots of the direct mode channel while communicating on the direct mode channel, the second mobile station switching in response to the information on the desired control channel, the timing information related to the desired control channel, the information on the energy economy mode start frame, and the length of the energy economy cycle.

3. A method as claimed in claim 1 or 2, characterized by carrying out the communicating by sending a registering message to the at least one base station on a system channel of the mobile communications system.

4. A method as claimed in claim 1 or 2, characterized by the mobile station activating the energy economy mode after registering to the system by sending a separate energy economy request message.

5. A method as claimed in claim 3, characterized by:

the registering message containing an identifier of the direct mode channel on which the mobile station is operating; and

checking from the database of the mobile communications system whether the energy economy mode start frame and the length of the energy economy cycle have been determined for the direct mode channel, the checking from the database in response to the identifier contained in the registering message.

6. A method as claimed in claim 5, characterized by utilizing the identifier of the direct mode channel contained in the registering message upon checking from the database whether the energy economy start frame and the length of the energy economy cycle have been determined for the direct mode channel, and upon storing the energy economy mode start frame and the length of the energy economy cycle in the database.

7. A method as claimed in claim 1, characterized by determining the energy economy mode start frame and the length of the energy economy cycle specifically for each base station.

8. A method as claimed in claim 1, characterized by determining specifically for each base station a same energy economy mode start frame and a same length of the energy economy cycle for all the dual watch mobile stations communicating via the base station.

9. A method as claimed in claim 1 or 2, characterized by communicating to the mobile station operating on the direct mode channel an event label of the energy economy mode, by means of which label all the mobile stations in the dual watch mode on the direct mode channel may be forced to switch or to end the energy economy mode.

10. A mobile communications system comprising:

a database;

at least one base station communicating with mobile stations in the mobile communications system on time division multiple access system channels of the mobile communications system including control channels and traffic channels having uplink and downlink frequencies divided into frames, part of which may be determined dynamically by determining an energy economy mode start frame and the length of an energy economy cycle, for a mobile station in the database as energy economy mode sleeping frames, during which the mobile station is not prepared to receive transmissions on the downlink frequencies;

at least a first mobile station communicating on a direct mode channel divided into frames, the at least first mobile station being predisposed to operate in a dual watch mode both on a control channel of the mobile communications system and on the direct mode channel which comprises pre-emption frames, by which the mobile stations communicating on the direct mode channel request transmission turns for themselves, the mobile communications system comprising;

means responsive to a registration message transmitted by the at least first mobile station for determining and storing in the database such an energy economy mode start frame and such a length of the energy economy cycle that each of a number of pre-emption frames co-incides with a corresponding number of sleeping frames of the energy economy mode; and

means for transmitting information on a desired control channel of the at least one base station and timing information related to it, and information on the energy economy mode start frame and the length of the energy economy cycle to the at least first mobile station, wherein the means responsive to the registration message and the means for transmitting the information permit mobile stations communicating on the direct mode channel to request transmission turns.