Synchronisation of mobile equipment in time division duplex CDMA system

• US 7,710,940 B2
• Filed: 10/16/2001
• Issued: 05/04/2010
• Est. Priority Date: 10/16/2001
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Van De Hee, Johan, Van Der Wal, Arnoud, Stoter, Jan
• Primary Examiner(s): Eng; George
• Assistant Examiner(s): Brandt; Christopher M
• Application Number:
  US10/492,627
• Publication Number:
  US 20050053048A1
• Time in Patent Office: 3,122 Days
• Field of Search: 370/350, 370/520, 370/503
• US Class Current: 370/350
• CPC Class Codes: H04B 1/7083 Cell search, e.g. using a three-step approach
• CPC Class Codes: H04B 2201/70702 Intercell-related aspects

Abstract

Method for synchronising mobile equipment in a CDMA system comprising a plurality of base stations (11) for communicating with the mobile equipment (12). The base stations (11) are mutually synchronised, and each base station (11) has a synchronisation channel transmit timing offset within a synchronisation time slot (20). The method comprises the step of synchronising the mobile equipment (12) by matching a synchronisation code in the synchronisation time slot (20). Also the following steps are executed by the method: scanning a base radio signal (13) during at least one frame (15) for detecting a signal portion with predetermined characteristics, such as received power peaks (23), the signal portion not being the synchronisation code; deriving timing information associated with the CDMA system from the signal portion; and starting the synchronisation step of the mobile equipment (12) using the timing information.

Claims

1. A method for synchronizing mobile equipment in a CDMA system comprising a plurality of base stations for communicating with the mobile equipment, the base stations being mutually synchronized, each base station having a synchronization channel transmit timing offset within a synchronization time slot, the method comprising the steps of:

prior to synchronizing the mobile equipment with a base station performing the following steps;

scanning a base radio signal during at least one frame to detect a signal portion with predetermined characteristics, one of the characteristics being received signal strength, the characteristics excluding a synchronization code;

deriving timing information associated with the CDMA system from the signal portion; and

starting synchronization of the mobile equipment with the base station using the timing information to perform a search to match the synchronization code in the synchronization time slot, wherein;

the signal portion is the received power of the base station signal as received by the mobile equipment;

or

the signal portion is a guard period of the base station signal.

2. The method according to claim 1, in which the method comprises the further steps of:

making a list of all received power peaks and associated time of occurrence in the at least one frame, the received power peaks having a time period of less then a predetermined number of chips, and an amplitude step of more than a predetermined value;

selecting the highest peak of the list and starting a first synchronization search just before occurrence of the highest peak.

3. The method according to claim 2, in which the method comprises the further step of selecting the strongest base station signal based on the received power information.

4. The method according to claim 1, in which the method further comprises the step of selecting the strongest base station signal based on the received power information.

5. The method according to claim 1, in which the method comprises the further steps of:

deriving timing information from the guard period; and

calculating from the timing information derived from the guard period, timing information associated with the synchronization slot.

6. The method according to claim 5, in which the method comprises the further step of selecting a channel associated with the strongest synchronization match.

7. The method according to claim 1, in which the method comprises the further step of controlling a timing oscillator of the mobile equipment using the derived timing information.

8. The method according to claim 1, in which the method comprises the further step of deriving cell parameters based on the timing information.

9. The method according to claim 1, the method being applied in a UTRA-TDD system or in a TD-SCDMA system.

10. A mobile equipment for use in a CDMA system, comprising:

a processing means;

a memory means; and

a transceiver means for receiving and transmitting CDMA signals, the memory means and the transceiver means being coupled to the processing means, the processing means prior to synchronizing with a base station further comprising;

means for scanning a base radio signal transmitted from the base station during at least one frame to detect a signal portion with predetermined characteristics, one of the characteristics being received signal strength, the characteristics excluding a synchronization code;

means for deriving timing information associated with the CDMA system from the signal portion; and

means for starting synchronization with the base station using the timing information to perform a search to match the synchronization code in a synchronization time slot, wherein;

the signal portion is the received power of the base station signal as received by the mobile equipment;

or

the signal portion is a guard period of the base station signal.

11. A computer readable medium encoded with software which is loadable on mobile equipment having processing means, the software comprising instructions to allow the processing means prior to synchronizing with a base station to:

scan a base radio signal transmitted from the base station during at least one frame to detect a signal portion with predetermined characteristics, one of the characteristics being received signal strength, the characteristics excluding a synchronization code;

derive timing information associated with the CDMA system from the signal portion; and

start synchronization with the base station using the timing information to perform a search to match the synchronization code in a synchronization time slot, wherein;

the signal portion is the received power of the base station signal as received by the mobile equipment;

the signal portion is a guard period of the base station signal.