Method of controlling communications in a cellular radiotelephone system

• US 4,984,290 A
• Filed: 08/04/1988
• Issued: 01/08/1991
• Est. Priority Date: 08/04/1988
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Puhl, Larry, Levine, Stephen N.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): FAILE, ANDREW I
• Application Number:
  US07/228,071
• Time in Patent Office: 887 Days
• Field of Search: 370/76, 370/110.1, 379/59, 379/60, 379/63, 455/33, 455/34, 455/38, 455/54, 455/56, 375/114-116
• US Class Current: 455/436
• CPC Class Codes: H04W 48/10 using broadcasted information
• CPC Class Codes: H04W 76/10 Connection setup

Abstract

A cellular system employs a subaudible signalling control protocol. The protocol includes transmitting supervisory related signals between the radiotelephone and one of the cell sites at a first subaudible digital bit rate, and transmitting data messages between the radiotelephone and said one of the cell sites at a second subaudible digital bit rate. Additionally, the system employs specific protocols involving alert, hand-off and call disconnect which accommodate the subaudible signalling, yet provide significant integrity and reliability advantages over previously known protocols.

Claims

1. A method of controlling communicating between a radiotelephone and one of a plurality of cell sites in a cellular-type radiotelephone communication system, comprising the steps of:

providing a plurality of digital signals identifiable with a uniquely identified cell;

transmitting the digital signals between the radiotelephone and the uniquely identified cell at a first subaudible bit rate; and

transmitting data messages between the radiotelephone and the uniquely identified cell at a second subaudible digital bit rate.

2. A method of controlling communications between a radiotelephone and one of a plurality of cello sites in a cellular-type radiotelephone communication system comprising the steps of:

providing a plurality of digital supervisory vectors, each vector representing identification of a unique cell site;

transmitting said vectors between the radiotelephone and one of the cell sites at a first subaudible digital bit rate; and

transmitting data messages between the radiotelephone and said one of the cell sites at a second subaudible digital bit rate.

3. The method according to claim 2, wherein the digital supervisory vectors are each of a predetermined bit length, wherein any cyclic shift of one of said vectors is at least a minimum Hamming distance from any other vector and cyclic shifts thereof.

4. The method according to claim 2, wherein the step of transmitting digital supervisory vectors is preceded by the step of providing a minimum Hamming distance between all cyclic shifts of a digital supervisory vector.

5. The method according to claim 2, wherein the step of transmitting digital supervisory sequences is preceded by the step of providing a minimum Hamming distance between any two of the following:

all signal supervisory vector, all cyclic shift of a supervisory vector all logical inverses of all digital supervisory vectors, and all cyclic shifts thereof.

6. The method according to claim 2, wherein the data messages are transmitted in Manchester coded words and wherein the step of transmitting digital supervisory vectors is preceded by the step of providing a minimum distance from any cyclic shift of each digital supervisory vector and its inverse to any Manchester coded word.

7. The method, according to claim 2, wherein the plurality of digital supervisory vectors are composed of a repetition of a single digital supervisory vector or cyclic shift thereof, wherein each vector and any cyclic shift thereof represents identification of a unique cell site.

13. The method according to claim 2 further comprising the steps of

providing at least one digital synchronization sequence for synchronizing communication between the radiotelephone and one of the cell sites;

and

transmitting the digital synchronization sequence between the radiotelephone and the cell site at the first subaudible digital bit rate.

8. A method of controlling communications between a radiotelephone and one of a plurality of cell sites in a cellular-type radiotelephone communication system, comprising the steps of:

providing a plurality of digital supervisory vectors, each vector and any cyclic shift thereof representing identification of a unique cell site, wherein each sequence is of a predetermined bit length and is of a minimum cross distance from any other vector;

providing a minimum auto distance for all digital supervisory vectors;

providing a minimum Hamming distance between all cyclic shifts of any digital supervisory vector and any inverse thereof;

transmitting said vectors between the radiotelephone and one of the cell sites at a first subaudible digital bit rate for distinguishing between cell sites; and

transmitting data messages between the radiotelephone and said one of the cell sites at a second subaudible digital bit rate.

9. A method for controlling communications between a radiotelephone and one of a plurality of cell sites in a cellular-type radiotelephone communication system, comprising the steps of:

providing a plurality of digital supervisory vectors, each vector representing identification of a unique single cell site;

transmitting supervisory related signals, including said digital supervisory vectors, between the radiotelephone and one of the cell sites at a first subaudible digital bit rate;

providing at least one synchronization word which has a maximum sync-cross distance and a minimum sync-cross distance for all said digital supervisory vectors; and

transmitting data messages and said at least one synchronization word between the radiotelephone and said one of the cell sites at a second subaudible digital bit rate.

10. For use in a cellular communication system between a radiotelephone and one of a plurality of cell sites, a method for setting up a radiotelephone call between a radiotelephone and a cell site in response to a page from a cell site, comprising the steps of:

(alert)

providing a digital supervisory sequences to represent the identification of a cell site;

transmitting said digital supervisory vector from said cell site at a first subaudible digital bit rate;

identifying and verifying said transmitted digital supervisory sequence at the radiotelephone;

transmitting said digital supervisory vector at least once from the radiotelephone;

receiving and validating said transmitted digital supervisory vector from the radiotelephone at the cell site;

transmitting at least one data message to the radiotelephone from the cell site at a second subaudible digital bit rate;

in response to the reception of an alert data message from the cell site, indicating to the radiotelephone user that an alert message has been received and transmitting said digital supervisory vector inverted from the radiotelephone;

in response to the reception of the digital supervisory vector inverted, transmitting the digital supervisory vector non-inverted from the cell site;

in response to an off-hook condition at the radiotelephone, transmitting said digital supervisory vector non-inverted from the radiotelephone; and

in response to the reception of said digital supervisory vector non-inverted from the radiotelephone, connecting the call to the radiotelephone.

11. For use in a cellular communication system between a radiotelephone and one of a plurality of cell sites, a method for handing-off a radiotelephone call from an originating cell site to a target cell site, comprising the steps of:

transmitting a digital supervisory vector from the target cell site;

terminating the transmission of the digital supervisory vector from the originating cell site and transmitting a hand-off data message from the originating cell site;

at the radiotelephone, receiving digital supervisory vector from the target cell site;

at the radiotelephone, transmitting the digital supervisory vector inverted to the target cell site to indicate that a hand-off has been successfully performed;

receiving and validating the digital supervisory sequence inverted from the radiotelephone at the target cell site;

at the originating cell site, terminating communication from the originating cell site to the radiotelephone; and

transmitting the digital supervisory vector non-inverted from the radiotelephone to the target cell site while the call is continued at the target cell site.

12. For use in a cellular communication system between a radiotelephone and one of a plurality of cell sites, a method for releasing a radiotelephone call between a radiotelephone and a cell site, comprising the steps of:

providing a first subaudible digital bit rate for the communication of supervisory related signals between the radiotelephone and the cell site;

providing a second subaudible digital bit rate for communicating data messages between the radiotelephone and the cell site;

from the radiotelephone, transmitting a disconnect data message at the second subaudible digital bit rate to the cell site;

from the cell site, transmitting a query data message at the second subaudible digital bit rate to the radiotelephone and including therein a cell site code word that is unique to the cell site;

in response to the reception of the query data message, transmitting a data message from the radiotelephone to the cell site containing said code word;

in response to the failure to receive the query data message within a predetermined time interval, retransmitting the disconnect data message to the cell site;

in response to the reception of a data message with a correct code word from the radiotelephone, disconnecting the call; and

in response to the reception of a data message with an incorrect code word from the radiotelephone, maintaining the call.