Cordless telephone communication system link re-establishment protocol

• US 5,280,541 A
• Filed: 10/24/1991
• Issued: 01/18/1994
• Est. Priority Date: 10/24/1991
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Wadin, Craig P., Marko, Paul D., Patsiokas, Stelios J.
• Primary Examiner(s): Ng, Jin F.
• Assistant Examiner(s): Bost, Dwayne D.
• Application Number:
  US07/782,022
• Time in Patent Office: 817 Days
• Field of Search: 379/58-61, 379/63, 455/33.1, 455/33.2, 455/34.1, 455/34.2, 455/51.1, 455/54.1, 455/62, 370/29, 370/100.1, 370/104.1, 370/105.1
• US Class Current: 455/462
• CPC Class Codes: H04L 7/10 Arrangements for initial synchronisation
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04M 1/72505 Radio link set-up procedures

Abstract

A method for re-establishing a communication link that has been lost between a portable unit (406) and a fixed unit or base station (402) provides for a way of quickly re-establishing the lost communication link, on the previously used RF channel. The method is begun by transmitting a link re-establishment code word (900) using MUX 1 after determining that synchronization has been lost (502) for a predetermined period of time (504). This is followed by automatically switching the portable unit (406) from MUX 1 to MUX 3 communication protocol. Followed by re-establishing communication (re-establish synchronization) between the portable (406) and base station (402) in MUX 3 and switching the two communication devices (402 and 406) back to MUX 1 after the communication link has been re-established. The same steps can be followed by base site (402) if it had been the first to detect loss of the communication link.

Claims

1. A method for re-establishing a communication link on a previously established RF communication channel between first and second communication devices after the communications between the first and second communication devices has been interrupted in a cordless telephone communication system which allocates one RF communication channel from among a plurality of RF communication channels, the first and second communication devices communicating with each other utilizing a first communication protocol and a second linking communication protocol, comprising the steps of:

(a) determining at the first communication device that communication with the second communication device has been interrupted by failing to receive select information during a first predetermined period of time established by a first timer;

(b) transmitting a link re-establishment code word from the first communication device to the second communication device after the first predetermined period of time has elapsed, and prior to a second timer elapsing, the second timer commencing upon the first timer elapsing;

(c) switching the first communication device from the first communication protocol to the second linking communication protocol before the expiration of the second timer;

(d) commencing a third timer after the second timer has elapsed, the third timer being long enough to provide that the second communication device has also switched to the second linking communication protocol before the third timer elapses;

(e) re-establishing communications between the first and second communication devices using the second linking communication protocol before the third timer elapses; and

(f) switching the two communication devices back to the first communication protocol once the communication link has been re-established.

2. The method for re-establishing a communication link of claim 1, wherein the first communication device is a base station and the second communication device is a portable telephone device.

3. The method for re-establishing a communication link of claim 1, wherein the first communication device is a portable telephone device and the second communication device is a base station.

4. A method for re-establishing a communication link as defined in claim 1, wherein step (a) comprises the steps of:

(a1) commencing the first timer after the reception of a code word or synchronization word;

(a2) determining if another code word or synchronization word has been received before the expiration of the first timer; and

(a3) resetting the first timer if another code word or synchronization word is received before the expiration of the first timer.

5. A method for re-establishing a communication link as defined in claim 4, comprising the further steps of:

(g) determining at the second communication device that communication with the first communication device has been interrupted by failing to receive predetermined information at the second communication device during a first period of time established by a first timer located in the second communication device;

(h) transmitting a link re-establishment code word from the second communication device to the first communication device after the first timer located on the second communication device has elapsed and prior to a second timer located on the second communication device elapsing, the second timer located on the second communication device commencing its timer sequence upon the first timer located on the second communication device elapsing; and

(i) switching the second communication device from the first communication protocol to the second linking communication protocol before the expiration of the second timer sequence.

6. A method for coordinating the re-establishment of a communication link on a previously established RF communication channel between first and second communication devices operating in a cordless telephone system having a plurality of RF communication channels, and the first and second communication devices communicating with each other utilizing a first communication protocol and a second linking communication protocol, comprising the steps of:

(a) transmitting a link re-establishment code word from both the first and second communication devices to the other of the first and second communication devices before a predetermined period of time has elapsed at each of the first and second communication devices since each of the first and second communication devices have received select information;

(b) switching the first and second communication devices from the first communication protocol to the second linking communication protocol before the expiration of the predetermined period of time at each of the first and second communication devices;

(c) commencing an existing channel timer at each of the first and second communication devices after the predetermined period of time has elapsed at each of the first and second communication devices, the existing channel timer providing a timing sequence which is long enough to provide that both the first and second communication devices have both switched to the second linking communication protocol before the existing channel timer elapses at either of the first and second communication devices;

(d) re-establishing communications between the first and second communication devices in the second linking communication protocol before the third timer elapses at either of the first and second communication devices; and

(e) switching the first and second communication devices back to the first communication protocol once the communication link has been re-established on the second communication protocol.

7. A method for coordinating the re-establishment of a communication link on a previously established RF communication channel as defined in claim 6, wherein the first communication device is a base station and the second communication device is a portable telephone device.

8. A method for coordinating the re-establishment of a communication link on a previously established RF communication channel as defined in claim 6, wherein the first communication device is a portable telephone device and the second communication device is a base station.

9. A portable telephone device for operation in a cordless telephone system which has a base station which allocates one RF communication channel from among a plurality of RF communication channels, the portable telephone device and base station communicate with each other utilizing a first communication protocol and a second linking communication protocol on an established RF communication channel, the portable telephone device comprising:

a receiver means for receiving selected information from the base station;

first timer means responsive to the receiver means for providing a first time-out signal if the if the receiver does not receive the selected information from the base station within a first predetermined period of time;

second timer means for initiating a second timer sequence in response to the first time-out signal;

transmitter means for transmitting a link re-establishment code word to the base station using the first communication protocol prior to the second timer sequence elapsing;

switching means for switching the portable telephone device from the first communication protocol to the second linking communication protocol after the re-establishment code word has been transmitted and prior to the second timer sequence elapsing;

third timer for initiating a third timer sequence upon the second timer sequence elapsing, the third timer sequence being long enough to provide that the base site has switched to the second linking communication protocol before the third timer sequence has elapsed;

re-establishment means for re-establishing communications between the portable telephone device and the base station using the second linking communication protocol before the third timer sequence elapses; and

means for automatically switching the portable telephone device back to the first communication protocol once the communications between the portable telephone and the base station have been re-established.

10. A base station for operation in a cordless telephone system, the base station allocates one RF communication channel from among a plurality of RF communication channels to a portable telephone, the portable telephone and base station communicate with each other utilizing a first communication protocol and a second linking communication protocol on the allocated RF communication channel, the base station comprising:

a receiver means for receiving selected information from the portable telephone;

first timer means responsive to the receiver means for providing a first time-out signal if the if the receiver does not receive the selected information from the portable telephone within a first predetermined period of time;

second timer means for initiating a second timer sequence in response to the first time-out signal;

transmitter means for transmitting a link re-establishment code word to the portable telephone using the first communication protocol prior to the second timer sequence elapsing;

switching means for switching the base station from the first communication protocol to the second communication protocol after the re-establishment code word has been transmitted and prior to the second timer sequence elapsing;

third timer for initiating a third timer sequence upon the second timer sequence elapsing, the third timer sequence being long enough to provide that the base site has switched to the second linking communication protocol before the third timer sequence has elapsed;

re-establishment means for re-establishing communications between the base station and the portable telephone using the second linking communication protocol before the third timer sequence elapses; and

means for automatically switching the base station back to the first communication protocol once communications between the base station and the portable telephone have been re-established.