Wideband ranging process for frequency acquisition

• US 6,473,420 B1
• Filed: 02/16/2001
• Issued: 10/29/2002
• Est. Priority Date: 02/16/2001
• Status: Active Grant

• Current Assignee: BWA Technology Incorporated
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Ekuhoho, Amévi Klutsé, Bourdeau, Richard
• Primary Examiner(s): Yao, Kwang Bin
• Application Number:
  US09/783,965
• Time in Patent Office: 620 Days
• Field of Search: 370/324, 370/328, 370/330, 370/343, 370/345, 370/350, 370/503, 370/516, 370/517, 370/519, 375/357, 375/358, 375/362, 375/364, 375/371
• US Class Current: 370/350
• CPC Class Codes: H04B 7/2675 Frequency synchronisation
• CPC Class Codes: H04J 3/0682 by delay compensation, e.g. by compensation of propagation delay or variations thereof, by ranging
• CPC Class Codes: H04W 56/0035 detecting errors in frequency or phase

Abstract

A system and method for synchronizing a hub radio and a remote radio by initially changing the frequency of the remote radio by a predetermined frequency offset, and then stepwise changing the frequency as a function of the tolerance of the hub radio to synchronize.

Claims

1. In a communication system having a hub radio and at least one remote radio, where the hub radio operates at a first frequency f₀ and includes a modem with a tolerance range of synchronization of ±

Δ

f₁, a method of synchronizing the remote radio with the hub radio comprising the steps of;

a) transmitting a first ranging signal from the remote radio to the hub radio;

b) receiving the ranging signal at the hub radio;

c) evaluating the ranging signal received at the hub and transmitting a synchronizing signal from the hub radio to the remote radio if the hub radio can not synchronize with the received ranging signal after a predetermined period of time;

d) receiving the synchronizing signal from the hub radio at the remote radio and adjusting the frequency of transmission of the remote radio to a predetermined frequency outside the tolerance range of the modem from f₀;

e) transmitting a ranging signal from the remote radio at the adjusted frequency to the hub radio;

f) evaluating the most recently received ranging signal at the hub radio and transmitting a synchronizing signal from the hub radio to the remote radio if the hub radio can not synchronize with the ranging signal after a predetermined period of time;

g) receiving the most recently received synchronizing signal from the hub radio at the remote radio and adjusting the frequency of transmission of the remote radio by a predetermined frequency correction;

h) transmitting a ranging signal from the remote signal at the adjusted frequency; and

i) repeating steps f)-h) until the hub radio can synchronize with the received ranging signal.

2. The method of claim 1 wherein:

the step of adjusting the frequency of transmission of the remote radio to a predetermined frequency outside the tolerance range of the modem includes lowering the transmission frequency of the remote lower than f₀, and

the step of adjusting the frequency of the remote radio by a predetermined frequency correction includes stepwise increasing of the transmission frequency of the remote.

3. The method of claim 1 wherein:

the step of adjusting the frequency of transmission of the remote radio to a predetermined frequency outside the tolerance range of the modem includes raising the transmission frequency of the remote higher than f₀, and

the step of adjusting the frequency of the remote radio by a predetermined frequency correction includes stepwise decreasing of the transmission frequency of the remote.

4. The method of claim 1 where the predetermined frequency outside of the tolerance range of the modem is offset from f₀ by approximately 400 kHz.

5. The method of claim 1 where the predetermined frequency correction is a function of the tolerance of the modem.

6. The method of claim 5 where the predetermined frequency correction is approximately equal to the tolerance of the modem.

7. The method of claim 1 where the hub and remote radio transmit utilizing Time Division Multiple Access (TDMA) point to multipoint communication.

8. A communication system having a hub radio and at least one remote radio, a method of synchronizing the hub radio and the remote radio to the same frequency, said hub radio capable of synchronizing within a predetermined frequency offset, comprising the steps of:

a. transmitting first modulated ranging data from a remote radio to the hub radio at a first frequency;

b. receiving the ranging data at the hub radio for demodulation;

c. transmitting a first synchronizing message from the hub radio to the remote radio if the hub radio is unable to demodulate the received ranging data after a predetermined period of time;

d. receiving the synchronizing message at the remote radio and adjusting the transmitting frequency of the remote radio to an initial synchronizing frequency in response thereto;

e. transmitting ranging data from the remote radio to the hub radio at the adjusted frequency; and

f. receiving the most recently received ranging data transmitted by the remote radio at the hub radio for demodulation;

g. transmitting a synchronizing message from the hub radio to the remote radio if the hub radio is unable to demodulate the ranging data after a predetermined period of time;

h. receiving the most recently received synchronizing message at the remote radio and adjusting the transmitting frequency of the remote radio as a function of the predetermined frequency offset;

i. transmitting ranging data from the remote radio to the hub radio at the adjusted frequency; and

J. repeating steps f-i until the hub radio successfully demodulates the ranging data.

9. The method of claim 8 wherein:

the step of adjusting the frequency of transmission of the remote radio to an initial synchronizing frequency includes lowering the transmission frequency of the remote lower than f₀, and

the step of adjusting the frequency of the remote radio as a function of the predetermined frequency offset includes stepwise increasing the transmission frequency of the remote.

10. The method of claim 8 wherein:

the step adjusting the frequency of transmission of the remote radio to an initial synchronizing frequency includes raising the transmission frequency of the remote higher than f₀, and

the step of adjusting the frequency of the remote radio as a function of the predetermined frequency offset includes stepwise decreasing the transmission frequency of the remote.

11. The method of claim 8 where the initial synchronizing frequency is offset from f₀ by approximately 400 kHz.

12. The method of claim 8 where the hub and remote radio transmit utilizing using Time Division Multiple Access (TDMA) point to multipoint communication.

13. In a communication system using Time Division Multiple Access (TDMA) having a hub radio and at least one remote radio, where the hub radio is capable of synchronizing with the remote radio within a predetermined frequency offset and where the hub radio synchronizes with the remote radio by providing frequency feedback to the remote radio, the improvement comprising wherein the hub radio causes the remote radio to change transmitting frequency of the remote radio as a function of the predetermined frequency offset.

14. In a communication system using Time Division Multiple Access (TDMA) having a hub radio and at least one remote radio, where the hub radio is capable of synchronizing with the remote radio within a predetermined frequency offset and within a predetermined period of time, the improvement comprising wherein the transmitting frequency of the remote radio is stepwise changed as a function of the predetermined frequency offset to thereby increase the frequency range of capture of hub radio within the predetermined period of time.

15. The method of claim 14, wherein each stepped change in transmitting frequency of the remote is approximately equal to the predetermined frequency offset.

16. In a communication system using Time Division Multiple Access (TDMA) having a hub radio and at least one remote radio, where the hub radio is capable of synchronizing with the remote radio within a predetermined frequency tolerance and where the hub radio synchronizes with the remote radio by providing frequency feedback to the remote radio, the improvement comprising wherein the hub radio initially causes the remote radio to change transmitting frequency of the remote radio to a frequency outside of the predetermined frequency tolerance when the hub radio senses that the remote radio is no longer synchronized.