Synchronisation of mobile equipment in time division duplex cdma system

• US 20050053048A1
• Filed: 10/16/2001
• Published: 03/10/2005
• 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
• Granted Patent: US 7,710,940 B2
• Time in Patent Office: Days
• 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. 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) being mutually synchronised, each base station (11) having a synchronisation channel transmit timing offset within a synchronisation time slot (20), the method comprising the step of synchronising the mobile equipment (12) by matching a synchronisation code in the synchronisation time slot (20),

characterised in that the method comprises the steps of:

scanning a base radio signal (13) during at least one frame (15) for detecting a signal portion with predetermined characteristics, one of the characteristics being received signal strength, the characteristics excluding the synchronization code as such;

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

starting the synchronisation step of the mobile equipment (12) using the timing information.

2. Method according to claim 1, in which the signal portion is the received power of the base station signal (13) as received by the mobile equipment (12), such as the received signal strength indicator (RSSI).

3. Method according to claim 2, in which the method comprises the further steps of

making a list of all RSSI peaks (23) and associated time of occurrence in the at least one frame (15), the RSSI peaks (23) having a time period of less then a predetermined number of chips, e.g. 300, and an amplitude step of more than a predetermined value, e.g. 3 dB;

selecting the highest peak (23) of the list and starting a first synchronisation search just before occurrence of the highest peak.

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

5. Method according to claim 1, in which the signal portion is the guard period (19) of the base station signal (13).

6. Method according to claim 5, in which the method comprises the further steps of

deriving timing information from the guard period (19);

and

calculating from the guard period timing information timing information associated with the synchronisation slot (20).

7. Method according to claim 6, in which the method comprises the further step of selecting a channel associated with the strongest synchronisation match.

8. Method according to claim 1, in which the method comprises the further step of controlling a timing oscillator (8) of the mobile equipment (12) using the derived timing information.

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

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

11. Mobile equipment for use in a CDMA system, the mobile equipment comprising processing means (7), memory means (6) and transceiver means (9) for receiving and transmitting CDMA signals, the memory means (6) and transceiver means (9) being connected to the processing means (7), and the processing means (7) being arranged to perform the steps of claim 1.

12. Software program product which is loadable on equipment (12) having processing means (7), the software program comprising instructions to allow the processing means to execute the steps of the method according to claim 1 through 10.

13. Data carrier comprising the software program product according to claim 12.

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