Methods and systems for synchronization with multiple frequency offsets and known timing relationships

• US 6,308,076 B1
• Filed: 03/23/1999
• Issued: 10/23/2001
• Est. Priority Date: 03/23/1999
• Status: Expired due to Term

• Current Assignee: Optis Wireless Technology, LLC (Brevet Capital)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Hoirup, Carsten, Palmer, Amie Pendleton
• Primary Examiner(s): Maung, Nay
• Assistant Examiner(s): CONTEE, JOY KIMBERLY
• Application Number:
  US09/275,060
• Time in Patent Office: 945 Days
• Field of Search: 455/13.1, 455/13.2, 455/12.1, 455/403, 455/500, 455/502, 370/324, 370/357, 370/503, 370/321, 375/344, 375/366, 375/354, 375/362, 375/358
• US Class Current: 455/502
• CPC Class Codes: H04B 7/2125 Synchronisation

Abstract

Methods and systems are provided which store frequency settings before switching frequencies, for example, before assignment to the traffic channel when switching between a ground station and another mobile station), thus, making it possible to recall the previous frequency setting and then only perform a second pass of the synchronization process or no synchronization at all. By storing the frequency setting, either as an offset to a given frequency or as an absolute frequency for each system to be monitored, the stored frequency setting can be re-used when subsequently monitoring a system.

Claims

1. A method of rapidly synchronizing a wireless device, utilizing a single reference frequency, to at least two received signals, the method comprising the steps of:

determining a time varying phase offset between a first received signal from a first source device and the single reference frequency so as to provide a first received signal phase offset;

determining a time varying phase offset between a second received signal from a second source device and the single reference frequency so as to provide a second received signal phase offset;

synchronizing to the first received signal utilizing the first received signal phase offset by applying the first phase offset to the single reference frequency; and

synchronizing to the second received signal by applying the second phase offset to the single reference frequency.

2. A method according to claim 1, further comprising the steps of:

storing the first received signal phase offset;

storing the second received signal phase offset; and

switching between synchronization to the first received signal and synchronization to the second received signal by selectively applying one of the stored first received signal phase offset and the stored second received signal phase offset to the reference frequency.

3. A method according to claim 1, wherein the reference frequency corresponds to a frequency of the first received signal and wherein the step of determining a phase offset between the first received signal and the reference frequency comprises setting the first received signal phase offset to zero.

4. A method according to claim 1, further comprising the step of synchronizing a local oscillator of the wireless device to a reference frequency transmitted by a third device so as to provide the single reference frequency.

5. A method according to claim 4, wherein the first device and the third device are co-located such that Doppler shift of the reference frequency transmitted by the third device and Doppler shift of the first received signal are substantially the same.

6. A method according to claim 1, further comprising the step of selectively synchronizing a local oscillator of the wireless device to a more stable of a reference frequency transmitted by the first device and a reference frequency transmitted by the second device so as to provide the single reference frequency.

7. A method according to claim 1, wherein the steps of determining a time varying phase offset between a first received signal from a first source device and the single reference frequency so as to provide a first received signal phase offset, determining a time varying phase offset between a second received signal from a second source device and the single reference frequency so as to provide a second received signal phase offset, synchronizing to the first received signal utilizing the stored first received signal phase offset by applying the first phase offset to the single reference frequency and synchronizing to the second received signal by applying the second phase offset to the single reference frequency, comprise:

determining a frequency difference between a first received signal from a first source device and the single reference frequency so as to provide a first received frequency offset;

determining a frequency difference between a second received signal from a second source device and the single reference frequency so as to provide a second received frequency offset;

synchronizing to the first received signal utilizing the stored first received frequency offset by applying a predefined phase ramp associated with the first received frequency offset to the single reference frequency; and

synchronizing to the second received signal by applying a predefined phase ramp associated with the second frequency offset to the single reference frequency.

8. A wireless device which utilizes a single reference frequency to synchronize to at least two received signals, comprising:

means for determining a time varying phase offset between a first received signal from a first source device and the single reference frequency so as to provide a first received signal phase offset;

means for determining a time varying phase offset between a second received signal from a second source device and the single reference frequency so as to provide a second received signal phase offset;

means for synchronizing to the first received signal utilizing the first received signal phase offset by applying the first phase offset to the single reference frequency; and

means for synchronizing to the second received signal by applying the second phase offset to the single reference frequency.

9. A wireless device according to claim 8, further comprising:

means for storing the first received signal phase offset;

means for storing the second received signal phase offset; and

means for switching between synchronization to the first received signal and synchronization to the second received signal by selectively applying one of the stored first received signal phase offset and the stored second received signal phase offset to the reference frequency.

10. A wireless device according to claim 8, wherein the reference frequency corresponds to a frequency of the first received signal and wherein the means for determining a time varying phase offset between the first received signal and the reference frequency to provide a first received signal phase offset comprises means for setting the first received signal phase offset to zero.

11. A wireless device according to claim 8, further comprising means for synchronizing a local oscillator of the wireless device to a reference frequency transmitted by a third device so as to provide the single reference frequency.

12. A wireless device according to claim 9, wherein the first device and the third device are co-located such that Doppler shift of the reference frequency transmitted by the third device and Doppler shift of the first received signal are substantially the same.

13. A wireless device according to claim 8, further comprising means for selectively synchronizing a local oscillator of the wireless device to a more stable of a reference frequency transmitted by the first device and a reference frequency transmitted by the second device so as to provide the single reference frequency.

14. A wireless device according to claim 8, wherein the means for determining a time varying phase offset between a first received signal from a first source device and the single reference frequency so as to provide a first received signal phase offset, means for determining a time varying phase offset between a second received signal from a second source device and the single reference frequency so as to provide a second received signal phase offset, means for synchronizing to the first received signal utilizing the stored first received signal phase offset by applying the first phase offset to the single reference frequency and means for synchronizing to the second received signal by applying the second phase offset to the single reference frequency, comprise:

means for determining a frequency difference between a first received signal from a first source device and the single reference frequency so as to provide a first received frequency offset;

means for determining a frequency difference between a second received signal from a second source device and the single reference frequency so as to provide a second received frequency offset;

means for synchronizing to the first received signal utilizing the stored first received frequency offset by applying a predefined phase ramp associated with the first received frequency offset to the single reference frequency; and

means for synchronizing to the second received signal by applying a predefined phase ramp associated with the second frequency offset to the single reference frequency.