Transceiver and associated method for surviving fades

• US 5,930,268 A
• Filed: 12/20/1996
• Issued: 07/27/1999
• Est. Priority Date: 12/20/1996
• Status: Expired due to Term

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Arens, John William, Ryan, Kathleen Helen, Kurby, Christopher Neil
• Primary Examiner(s): VU, HUY DUY
• Application Number:
  US08/771,597
• Time in Patent Office: 949 Days
• Field of Search: 370/503, 370/504, 370/505, 370/506, 370/507, 370/508, 370/509, 370/510, 370/511, 370/512, 370/513, 370/514, 370/515, 370/516, 370/517, 370/518, 370/519, 370/520, 370/350 , 370/321, 370/337, 370/347, 370/442, 370/311, 375/354, 375/356, 375/357, 375/358, 375/362, 375/365, 375/368, 340/825.14, 455/502, 455/504, 455/505, 455/506, 455/511, 455/515, 455/517, 455/526, 455/67.1, 455/343, 455/10, 455/67.3
• US Class Current: 370/509
• CPC Class Codes: H04B 7/18506 Communications with or from aircraft, i.e. aeronautical mobile service
• CPC Class Codes: H04B 7/2125 Synchronisation
• CPC Class Codes: H04B 7/2681 Synchronisation of a mobile station with one base station
• CPC Class Codes: H04W 56/003 Arrangements to increase tolerance to errors in transmission or reception timing

Abstract

A time-framed communications transceiver maintains synchronization through fade conditions by resetting a counter (640) whenever new synchronization parameters are stored in a memory (630) based on bursts detected by a receiver (610) and a burst synchronizer (620). A transmitter (690) transmits bursts based upon the synchronization parameters in the memory (630) when the time counter (640) has not exceeded a predetermined period of time. The receiver (610) re-establishes the synchronization parameters in the memory (630) when the time counter exceeds another, longer predetermined period of time before transmission by the transmitter (690).

Claims

1. A method of maintaining synchronization through fade conditions in a time-framed communications system, the method comprising the steps of:

(a) intermittently operating a receiver of a time-framed communications transceiver to receive received bursts;

(b) checking if the received bursts are detectable;

(c) if one of the received bursts checked in step (b) is detectable, extracting synchronization parameters from the received burst, storing the synchronization parameters in memory and resetting a counter;

(d) if a received burst is undetectable, determining if the counter has not exceeded a predetermined short time period and determining if previous synchronization parameters were stored in step (c) in the memory;

(e) if both of the determinations in step (d) are affirmative, in transmitter of the time-framed communications transceiver, transmitting a transmit burst to a remote station based on the stored synchronization parameters; and

(f) if the received burst is undetectable for a predetermined long time period, operating the receiver to receive a received burst from another channel of the system having frames with a longer synchronization portion than a present channel, extracting synchronization information from a detectable received burst to re-establish synchronization parameters, and transmitting the transmit burst to the remote station based on the re-established synchronization parameters.

2. A method according to claim 1, wherein the predetermined short time period is a length of time an intolerable amount of variation in frequency and of variation in frame arrival time would cause loss of synchronization of the transmitter of the time-framed communications transceiver with a receiver of the remote station.

3. A method according to claim 2, wherein the predetermined short time period is approximately 1.8 seconds.

4. A method according to claim 1, wherein the predetermined long time period is a length of time an intolerable amount of variation in frame arrival time and of variation in frequency would cause loss of synchronization with a transmitter of the remote station.

5. A method according to claim 4, wherein the predetermined long time period is approximately 8 seconds.

6. A method according to claim 1, wherein the receiver of the time-framed communications transceiver is more tolerant to drift in the synchronization parameters than the transmitter of the time-framed communications transceiver.

7. A method according to claim 1, further comprising the step of if a received burst is undetectable, then again operating the receiver of the time-frame communications transceiver to attempt to receive a detectable received burst in order to transmit the transmit burst.

8. A method according to claim 1, wherein if the received burst is detectable, then extracting synchronization parameters from the received burst and transmitting the transmit burst to the remote station based on the extracted synchronization parameters.

9. A method according to claim 1, wherein the received burst is received on a traffic channel and the transmit burst is transmitted on the traffic channel.

10. A method according to claim 1, wherein the transmitter of the time-framed communications transceiver is synchronized to a receiver of the remote station using the synchronization parameters received from the remote station by the time-framed communications transceiver.

11. A method according to claim 1, wherein the transmit burst maintains synchronization of the transmitter of the time-frame communications transceiver with a receiver of the remote station to avoid dropping of a call.

12. A method according to claim 1, wherein the synchronization parameters comprise both transmitter frequency and frame timing parameters.

13. A time-framed communications transceiver apparatus for maintaining synchronization through fade conditions in a time-framed communications system, the apparatus comprising:

a receiver for receiving bursts and checking if received bursts are detectable;

a memory for storing synchronization parameters;

a counter for counting after detection of a received burst;

a burst synchronizer operatively coupled to the receiver, the memory and the counter to extract synchronization parameters from the received burst, store the synchronization parameters in the memory and reset the counter when a received burst is detectable;

a transmitter operatively coupled to the burst synchronizer, the memory and the counter to transmit a transmit burst to a remote station based on the stored synchronization parameters both if the counter has not exceeded a predetermined short time period and if previous synchronization parameters were stored in the memory when a received burst is undetectable;

wherein after a burst is undetectable for a predetermined long time period, the receiver receives a received burst from another channel of the system having frames with a longer synchronization portion than a present channel and the burst synchronizer extracts synchronization information from a detectable received burst to re-establish synchronization parameters; and

wherein the transmitter transmits the transmit burst to the remote station based on the re-established synchronization parameters.

14. An apparatus according to claim 13, wherein the predetermined short time period is a length of time an intolerable amount of variation in frequency and of variation in frame arrival time would cause loss of synchronization of a receiver of the remote station.

15. An apparatus according to claim 13, wherein the predetermined long time period is a length of time an intolerable amount of variation in frame arrival time and of variation in frequency would cause loss of synchronization with a transmitter of the remote station.

16. An apparatus according to claim 13, wherein the receiver of the time-framed communications transceiver is more tolerant to drift in the synchronization parameters than the transmitter of the time-framed communications transceiver.

17. A time-framed communications transceiver apparatus for maintaining synchronization through fade conditions in a time-framed communications system, the apparatus comprising:

a receiver for receiving bursts on a traffic channel and checking if received bursts are detectable;

a memory for storing synchronization parameters;

a counter for counting after detection of a received burst;

a burst synchronizer operatively coupled to the receiver, the memory and the counter for, when a received burst is detectable, extracting synchronization parameters from the received burst, storing the synchronization parameters in the memory and resetting the counter and for, after a burst is undetectable for a first predetermined time period, receiving and detecting a burst from a broadcast channel of the system having frames with a longer synchronization portion than the traffic channel and re-extracting synchronization information therefrom to re-establish synchronization parameters; and

a transmitter, more tolerant to drift in synchronization parameters than the receiver, operatively coupled to the burst synchronizer, the memory and the counter for transmitting a transmit burst to a remote station based on a synchronization if both the counter has not exceeded a second predetermined time period and previous synchronization parameters were stored in the memory when a received burst is undetectable or if synchronization parameters have been re-established after the first predetermined time period.