Rapid synchronization for communication systems

• US 6,041,088 A
• Filed: 06/10/1998
• Issued: 03/21/2000
• Est. Priority Date: 10/23/1996
• Status: Expired due to Term

• Current Assignee: Tamiras Per Pte Ltd LLC (Intellectual Ventures LLC)
• Original Assignee: SiCOM, Inc. (Renesas Electronics Corporation)
• Inventors: McCallister, Ronald D.
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): JIANG, LENNY R
• Application Number:
  US09/095,357
• Time in Patent Office: 650 Days
• Field of Search: 375/354, 375/358, 375/356, 370/324, 370/350, 455/502, 455/71, 455/62, 455/69
• US Class Current: 375/358
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase
• CPC Class Codes: H04W 84/14 WLL [Wireless Local Loop]; RLL [Radio Local Loop]
• CPC Class Codes: H04W 92/10 between terminal device and access point, i.e. wireless air interface

Abstract

Different subscriber units (14) transmit different burst signals to a base station (12) on a common frequency to which a base station demodulator (64) is already synchronized. The base station (12) transmits constant values α and η, where α is multiplied by a base station reference frequency to achieve a base station transmitting frequency, and η is multiplied by the reference frequency to achieve the base station (12) receiving frequency. A subscriber unit (14) synchronizes to the base station transmitting frequency. As a result of the synchronization process, the subscriber unit (14) determines a value μ, which, when multiplied by a subscriber unit reference frequency, achieves the subscriber unit synchronization frequency. The subscriber unit then determines a value γ, which is proportional to η and β and inversely proportional to α. The subscriber unit reference frequency is multiplied by γ to achieve the frequency at which the subscriber unit (14) transmits.

Claims

1. A method for rapid frequency synchronization of a reverse channel signal to a base station receiving frequency which is proportional to η

times a base station reference frequency, where η

is a first value, said method comprising the steps of;

transmitting a forward channel signal from a base station, said forward channel signal exhibiting a base station transmitting frequency which is proportional to α

times said base station reference frequency, where α

is a second value;

calculating, at said subscriber unit, a frequency multiplicand which is proportional to η and

inversely proportional to α

;

generating a subscriber unit transmitting frequency in response to said frequency multiplicand; and

transmitting said reverse channel signal from said subscriber unit, said reverse channel signal exhibiting said subscriber unit transmitting frequency.

2. A method as claimed in claim 1 additionally comprising the steps of:

configuring said forward channel signal to convey frequency adjustment data which are responsive to said base station receiving frequency and to said base station transmitting frequency; and

extracting said frequency adjustment data from said forward channel signal prior to said calculating step.

3. A method is claimed in claim 1 wherein:

said forward channel transmitting step continuously transmits said forward channel signal for a first predetermined duration; and

said reverse channel transmitting step continuously transmits said reverse channel signal for a second predetermined duration, said second predetermined duration being shorter than said first predetermined duration.

4. A method as claimed in claim 1 wherein a subscriber unit receiving frequency and said subscriber unit transmitting frequency are each responsive to a subscriber unit reference frequency.

5. A method as claimed in claim 4 additionally comprising the step of synchronizing said subscriber unit receiving frequency to said base station transmitting frequency.

6. A method as claimed in claim 4 wherein:

said subscriber unit receiving frequency is proportional to β

times said subscriber unit reference frequency, where β

is a third value; and

said calculating step comprises the step of making said multiplicand proportional to β

.

7. A method as claimed in claim 6 wherein said generating step comprises the step of multiplying (68) said subscriber unit reference frequency by said multiplicand.

8. A method as claimed in claim 7 wherein said multiplying step comprises the steps of:

synthesizing a first signal at a first frequency determined in response to a first portion of said multiplicand, said first frequency being adjustable in first frequency steps over a first frequency adjustment range; and

producing a second signal at a second frequency determined in response to said frequency of said first signal and a second portion of said multiplicand, said second frequency being adjustable in second frequency steps which are larger than said first frequency steps over a second frequency adjustment range which is larger than said first frequency adjustment range.

9. A method as claimed in claim 8 wherein:

said synthesizing step is performed in digital components; and

said producing step is performed in analog components.

10. A method as claimed in claim 1 wherein said generating step generates a baud clock signal oscillating at said subscriber unit transmitting frequency.

11. A method as claimed in claim 1 wherein said generating step generates a carrier signal oscillating at said subscriber unit transmitting frequency.

12. A method as claimed in claim 1 wherein:

said base station receiving frequency is a carrier frequency, said base station transmitting frequency is a carrier frequency, said base station reference frequency is a carrier reference frequency, said frequency multiplicand is a carrier frequency multiplicand, and said subscriber unit transmitting frequency is a carrier frequency;

a base station receiving baud frequency is proportional to η

'"'"' times a base station baud reference frequency, where η

'"'"' is a third value;

a base station transmitting baud frequency is proportional to α

'"'"' times said base station baud reference frequency, where α

'"'"' is a fourth value;

said forward channel signal exhibits said base station transmitting carrier frequency and said base station transmitting baud frequency;

said method additionally comprises the step of calculating, at said subscriber unit, a baud frequency multiplicand which is proportional to η

'"'"' and inversely proportional to α

'"'"';

said method additionally comprises the step of generating a subscriber unit transmitting baud frequency in response to said baud frequency multiplicand; and

said reverse channel signal exhibits said subscriber unit transmitting carrier frequency and said subscriber unit transmitting baud frequency.

13. A method as claimed in claim 1 wherein said base station and said subscriber unit are substantially stationary relative to each other.

14. A method as claimed in claim 1 wherein:

said subscriber unit is one of a plurality of subscriber units;

each of said plurality of subscriber units performs said calculating, generating and transmitting steps;

said calculating step performed at each of said plurality of subscriber units calculates frequency multiplicands which are different for each of said plurality of subscriber units; and

said generating step performed in each of said plurality of subscriber units generates substantially equal subscriber unit transmitting frequencies.

15. In an RF digital communication system in which a base station rapidly synchronizes a reverse channel signal to a base station receiving frequency that is proportional to η

(eta) times a base station reference frequency, where η

is a first value, and in which said base station transmits a forward channel signal that exhibits a base station transmitting frequency which is proportional to α

(alpha) times said base station reference frequency, where α

is a second value, an RF digital communication subscriber unit comprising;

a demodulator configured to synchronize a subscriber unit receiving frequency to said base station transmitting frequency and generate error data which are responsive to both said subscriber unit receiving frequency and a subscriber unit reference frequency;

a controller coupled to said demodulator, said controller being configured to calculate a frequency multiplicand which is proportional to η

, inversely proportional to α

, and responsive to said error data;

a frequency multiplier circuit coupled to said controller to multiply said subscriber unit reference frequency by said frequency multiplicand; and

an RF circuit coupled to said frequency multiplier circuit and configured to generate said reverse channel signal, said reverse channel signal exhibiting said subscriber unit transmitting frequency.

16. An RF digital communication subscriber unit as claimed in claim 15 wherein:

said base station is configured so that said forward channel signal conveys frequency adjustment data which are responsive to said base station receiving frequency and to said base station transmitting frequency; and

said controller is configured so that said frequency multiplicand is responsive to said frequency adjustment data.

17. An RF digital communication subscriber unit as claimed in claim 15 wherein:

said subscriber unit receiving frequency is proportional to β

(beta) times said subscriber unit reference frequency, where β

is a third value;

said third value β

equals β

_c (beta-coarse) plus β

_f (beta-fine), where β

_f is a fourth value that is characterized by said error data and where β

_c is a fifth value;

said subscriber unit additionally comprises a second frequency multiplier circuit in which said subscriber unit receiving frequency is multiplied by β

_c, said second frequency multiplier circuit being coupled to said demodulator; and

said controller is configured so that said frequency multiplicand is additionally proportional to β

.

18. An RF digital communication subscriber unit as claimed in claim 15 wherein said frequency multiplier circuit comprises:

a digital frequency synthesizer configured to synthesize a first signal at a first frequency determined in response to a first portion of said frequency multiplicand, said first frequency being adjustable in first frequency steps over a first frequency adjustment range; and

an analog frequency synthesizer configured to produce a second signal at a second frequency determined in response to said frequency of said first signal and a second portion of said multiplicand, said second frequency being adjustable in second frequency steps which are larger than said first frequency steps over a second frequency adjustment range which is larger than said first frequency adjustment range.

19. An RF digital communication subscriber unit as claimed in claim 15 wherein said frequency multiplier circuit generates a baud clock signal oscillating at said subscriber unit transmitting frequency.

20. An RF digital communication subscriber unit as claimed in claim 15 wherein said frequency multiplier circuit generates a carrier signal oscillating at said subscriber unit transmitting frequency.

21. An RF digital communication subscriber unit as claimed in claim 15 wherein:

said base station receiving frequency is a carrier frequency, said base station transmitting frequency is a carrier frequency, said base station reference frequency is a carrier reference frequency, said frequency multiplicand is a carrier frequency multiplicand, and said subscriber unit transmitting frequency is a carrier frequency;

a base station receiving baud frequency is proportional to η

'"'"' times a base station baud reference frequency, where η

'"'"' is a third value;

a base station transmitting baud frequency is proportional to α

'"'"' times said base station baud reference frequency, where α

'"'"' is a fourth value;

said forward channel signal exhibits said base station transmitting carrier frequency and said base station transmitting baud frequency;

said controller is additionally configured to calculate a baud frequency multiplicand which is proportional to η

'"'"' and inversely proportional to α

'"'"';

said subscriber unit additionally comprises a second frequency multiplier circuit coupled to said controller and said RF circuit to multiply said subscriber unit reference frequency by said baud frequency multiplicand; and

said RF circuit is configured so that said reverse channel signal exhibits said subscriber unit transmitting carrier frequency and said subscriber unit transmitting baud frequency.

22. A method for rapid synchronization of a subscriber unit transmitting frequency to a base station receiving frequency which is proportional to η

times a base station reference frequency, where η

is a first value, said method comprising the steps of;

causing said base station receiving frequency and a base station transmitting frequency to be responsive to a base station reference frequency, said base station transmitting frequency being proportional to α

times said base station reference frequency, where α

is a second value;

causing a subscriber unit receiving frequency and said subscriber unit transmitting frequency to be responsive to a subscriber unit reference frequency, said subscriber unit receiving frequency being proportional to β

times said subscriber unit reference frequency, where β

is a third value;

synchronizing said subscriber unit receiving frequency to said base station transmitting frequency;

calculating, at said subscriber unit, a radio frequency multiplier which is proportional to η and

to β and

inversely proportional to α

; and

generating said subscriber unit transmitting frequency in response to said radio frequency multiplier and said subscriber unit reference frequency.

23. An RF digital communication system comprising:

a base station having an oscillator which establishes a base station reference frequency, a receiver configured to receive a reverse channel signal at a base station receiving frequency which is proportional to η

(eta) times said base station reference frequency, a transmitter configured to transmit a forward channel signal exhibiting a base station transmitting frequency which is proportional to α

(alpha) times said base station reference frequency, said forward channel signal conveying frequency adjustment data which are responsive to said base station receiving frequency and to said base station transmitting frequency;

a first subscriber unit configured to extract said frequency adjustment data from said forward channel signal, to calculate a first frequency multiplicand which is proportional to η and

inversely proportional to α

, to generate a subscriber unit transmitting frequency in response to said first frequency multiplicand, and to transmit a first portion of said reverse channel signal at substantially said subscriber unit transmitting frequency; and

a second subscriber unit configured to extract said frequency adjustment data from said forward channel signal, to calculate a second frequency multiplicand which is proportional to η and

inversely proportional to α

, to generate substantially said subscriber unit transmitting frequency in response to said second frequency multiplicand, and to transmit a second portion of said reverse channel signal at substantially said subscriber unit transmitting frequency.

24. An RF digital communication system as claimed in claim 23 wherein:

said first subscriber unit includes a first oscillator oscillating at a first subscriber unit reference frequency;

said second subscriber unit includes a second oscillator oscillating at a second subscriber unit reference frequency, said second subscriber unit reference frequency differing from said first subscriber unit reference frequency; and

said first and second multiplicands differing from one another to compensate for differences between said first and second subscriber unit reference frequencies.