Method and system for reducing the time for connecting a mobile to a cellular base station

• US 5,640,675 A
• Filed: 01/04/1996
• Issued: 06/17/1997
• Est. Priority Date: 01/05/1995
• Status: Expired due to Term

• Current Assignee: Alcatel Mobile Phones
• Original Assignee: Alcatel Mobile Phones
• Inventors: Pinault, Francis, Jouin, Christophe
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Kincaid, Lester G.
• Application Number:
  US08/582,961
• Time in Patent Office: 530 Days
• Field of Search: 455/33.1, 455/33.4, 455/34.1, 455/54.1, 455/54.2, 455/56.1, 455/62, 455/67.1, 455/161.1, 455/161.2, 455/161.3, 455/186.1, 455/166.1, 455/166.2, 379/58, 379/59
• US Class Current: 455/434
• CPC Class Codes: H04W 48/16 Discovering, processing access restriction or access information
• CPC Class Codes: H04W 48/18 Selecting a network or a communication service

Abstract

Periodically, when a mobile is in its normal mode of operation, a first list of control frequencies transmitted by respective base stations of the geographical area in which the mobile is located is stored in a SIM card and a second list of control frequencies and associated respective maximal second receive levels measured by the mobile is stored in RAM. In response to being switched on, the mobile measures a first receive level for each of the control frequencies defined in the network and a comparator compares the first and second receive levels for each of the control frequencies of the second list, to assess movement of the mobile. To synchronize to a given network constituting a subnetwork of the radio communication network, the mobile uses the control frequencies defined in the radio communication network or the control frequencies from the first list, respectively, according to whether the mobile has moved or not.

Claims

1. A method for reducing the duration of a phase for connecting a mobile to a base station of a given network constituting a subnetwork of a radio communication network, said method comprising the steps of:

(a1) storing a first list of control frequencies transmitted by respective base stations of a geographical area in which the mobile is located, and

(b1) measuring, by the mobile during the connection phase, a respective first receive level for each of the control frequencies defined in said radio communication network,

(a2) storing a second list of control frequencies and second receive levels respectively associated with said control frequencies of said second list and measured by said mobile, said second levels corresponding to maximal power levels received by said mobile,

(b2) during said connection phase, comparing said first and second receive levels for each of said control frequencies from said second list,

synchronizing said mobile to said control frequency from said first list having the highest first receive level if for each of said control frequencies of said second list said first and second receive levels are substantially identical, and

synchronizing said mobile to each of the control frequencies defined in said radio communication network, in decreasing first receive level order, until said mobile receives data conveyed by one of all said control frequencies defined in said radio communication network which identifies said one control frequency as being generated by a base station of said given network, if for at least one of said control frequencies from said second list said first and second receive levels are significantly different.

2. The method according to claim 1 wherein said first list of control frequencies transmitted by respective base stations of a geographical area in which said mobile is located is transmitted periodically by said given network and received by said mobile when it is connected to a base station of that given network.

3. The method according to claim 1 wherein said first list is stored in a memory of a removable medium that can be plugged into said mobile.

4. The method according to claim 1 wherein said second list is stored in a random access memory included in said mobile and powered even when said mobile is switched off.

5. A mobile for implementing a method for reducing the duration of a phase for connecting said mobile to a base station of a given network constituting subnetwork of a radio communication method, said method comprising the steps of storing a first list of control frequencies transmitted by respective base stations of a geographical area in which the mobile is located, measuring a respective first receive level for each of the control frequencies defined in said radio communication network, storing a second list of control frequencies and receive second levels respectively associated with said control frequencies of said second list and measured by said mobile, said second levels corresponding to maximal power levels received by said mobile, comparing said first and second receive levels during said connection phase for each of said control frequencies from said second list, and synchronizing said mobile to a control frequency based on the results of said comparison, said mobile comprising:

a transmit/receive processing subsystem for measuring respective receive levels for received control frequencies and a memory for storing respective first receive levels of said control frequencies defined in said radio communication network,

a comparator for comparing said first and second receive levels for each of said control frequencies from said second list, said respective second receive levels for said control frequencies from said second list being stored in a non-volatile memory of said mobile, and

means in said subsystem for;

synchronizing said mobile to the control frequency from said first list that is associated with the highest first receive level if for each of said control frequencies from said second list said first and second receive levels are substantially identical, and

synchronizing said mobile to each of said control frequencies defined in said radio communication network, in decreasing first receive level order, until said mobile receives data conveyed by one of all said control frequencies defined in said radio communication network which identifies said one control frequency as being that generated by a base station of said given network if, for at least one of said control frequencies from said second list, said first and second receive levels are significantly different.

6. A method for reducing the duration of a phase for connecting a mobile to a base station of a given network constituting a subnetwork of a radio communication network, said method comprising the steps of:

measuring, by said mobile during said connection phase, a respective first receive level for each of the control frequencies defined in said radio communication network,

storing a list of control frequencies each associated with a respective second receive level measured by said mobile and a respective synchronization code, said second levels corresponding to maximal power levels received by said mobile,

during said connection phase, comparing said first and second receive levels for each of said control frequencies from said list,

synchronizing said mobile to the control frequency from the list with the highest receive level, based on the synchronization code associated with the control frequency from said list having the highest receive level, if for each of said control frequencies from said list said first and second receive levels are substantially identical, and

synchronizing said mobile to each of all the control frequencies defined in said radio communication network, in decreasing first receive level order, until said mobile receives data conveyed by one of all said control frequencies defined in said radio communication network that identifies said one control frequency as being generated by a base station of said given network, if, for at least one of said control frequencies from said list, said first and second receive levels are significantly different.

7. The method according to claim 6 wherein said synchronization code comprises a base station identification code.

8. The method according to claim 6 wherein said list is stored in a random access memory included in said mobile and which is powered even when said mobile is switched off.