Paging system using LPC speech encoding with an adaptive bit rate

• US 4,811,376 A
• Filed: 10/16/1987
• Issued: 03/07/1989
• Est. Priority Date: 11/12/1986
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Davis, Walter L., Parikh, Dakshesh D.
• Primary Examiner(s): Lev, Robert
• Application Number:
  US07/109,982
• Time in Patent Office: 508 Days
• Field of Search: 379/57, 379/63, 379/88, 370/18, 370/50, 370/95, 455/54, 340/825.44
• US Class Current: 340/7.28
• CPC Class Codes: G10L 19/06 Determination or coding of the spectral characteristics, e.g. of the short-term prediction coefficients
• CPC Class Codes: H04M 11/022 Paging systems personal calling arrangements or devices G08B3/1008; selective calling networks H04W84/022
• CPC Class Codes: H04W 88/185 Selective call encoders for paging networks, e.g. paging centre devices

Abstract

A paging system providing an LPC encoded speech output having an adaptive bit rate. The LPC bit rate is adaptively modified based on paging system airtime loading. Synthesizer circuitry in the paging receivers, together with a system signaling scheme is used to update the paging receivers as to the LPC bit rate, allows the paging receiver to decode the adaptive bit rate signal.

Claims

1. An improving paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signalling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(c) variable clock means for producing a clock signal, wherein the clock signal rate varies with the time of day;

(d) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input;

(e) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence; and

(f) modulator and transmitter means for transmitting the predefined sequence.

2. The system according to claim 1, wherein said terminal means further having means for storing and reproducing the LPC encoded voice information received from said LPC analyzer means.

3. The system according to claim 1, wherein said clock signal rate varies from 2400 to 9600 bits per second.

4. The system according to claim 1 further comprising at least one paging receiver responsive to the transmitted predetermined sequence including paging signaling information and voice information, said receiver for reproducing the transmitted voice information in response to the transmitted signaling information being decoded.

5. A method for use in a paging system having LPC speech encoder coupled to a paging terminal for generating digitally encoded voice signals for transmission to paging receivers, said method comprising the steps of:

(a) inputting voice signals comprising paging messages;

(b) generating a variable signal that varies with the time of day;

(c) converting said inputted voice signals into LPC encoded digital voice signals at a data rate controlled by said variable signal;

(d) combining said LPC encoded digital voice signals with paging signaling information to generate a composite paging signal; and

(e) transmitting said composite paging signal.

6. An improved paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) loading measurement means coupled to said telephone interface means for determining the relative loading of the paging system at any particular time and producing an output signal related to the system loading, said loading measurement means comprising,

a timer for generating a periodic reset signal at a predetermined time interval,

an airtime counter, coupled to said timer and to said telephone interface means, for measuring the elapsed air time since the last reset signal, and

loading direction indicator, responsive to said airtime counter, for indicating the direction at which the system loading is changing;

(c) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signaling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(d) variable clock means, coupled to said loading measurement means for producing a clock signal wherein the clock signal rate is based on said output signal of said loading measurement means and lower clock signal rates are produced at times of relatively higher system loading;

(e) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input;

(f) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence; and

(g) modulator and transmitter means for transmitting the predefined sequence.

7. An improved paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) loading measurement means coupled to said telephone interface means for determining the relative loading of the paging system at any particular time and producing an output signal related to the system loading;

(c) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signaling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(d) variable clock means, coupled to said loading measurement means for producing a clock signal wherein the clock signal rate is based on said output signal of said loading measurement means and lower clock signal rates are produced at times of relatively higher system loading;

(e) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input,

said terminal means further having means for storing and reproducing the LPC encoded voice information received from said LPC analyzer means;

(f) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence; and

(g) modulator and transmitter means for transmitting the predefined sequence.

8. An improved paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) loading measurement means coupled to said telephone interface means for determining the relative loading of the paging system at any particular time and producing an output signal related to the system loading;

(c) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signaling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(d) variable clock means, coupled to said loading measurement means for producing a clock signal wherein the clock signal rate is based on said output signal of said loading measurement means and lower clock signal rates are produced at times of relatively higher system loading;

(e) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input;

(f) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence, said controller means further detecting at least two consecutive periods of loading change prior to effecting the varying of said variable clock means rate; and

(g) modulator and transmitter means for transmitting the predefined sequence.

9. An improved paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) loading measurement means coupled to said telephone interface means for determining the relative loading of the paging system at any particular time and producing an output signal related to the system loading;

(c) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signaling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(d) variable clock means, coupled to said loading measurement means for producing a clock signal varying from 2400 to 9600 bits per second, the clock signal rate produced being based on said output signal of said loading measurement means and lower clock signal rates are produced at times of relatively higher system loading;

(e) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input;

(f) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence; and

(g) modulator and transmitter means for transmitting the predefined sequence.

10. An improved paging system for use with LPC encoded signals, said system comprising:

(a) telephone interface means for inputting paging requests and analog voice information;

(b) loading measurement means coupled to said telephone interface means for determining the relative loading of the paging system at any particular time and producing an output signal related to the system loading;

(c) terminal means having storage capability, said terminal means coupled to said telephone interface means for generating paging signaling information based on signals taken from said telephone interface means, and further storing and reproducing voice information received from said telephone interface means;

(d) variable clock means, coupled to said loading measurement means for producing a clock signal wherein the clock signal rate is based on said output signal of said loading measurement means and lower clock signal rates are produced at times of relatively higher system loading;

(e) LPC analyzer means having a clock input, said analyzer means coupled to said terminal means for converting the voice information to digitally encoded LPC signals at a data rate determined by said clock input;

(f) controller means coupled to said terminal means, said variable clock means and responsive to said loading measurement means for formatting the LPC encoded voice information, and the paging signaling information in a predefined sequence which includes a digital word indicating the data rate of the predefined sequence;

(g) modulator and transmitter means for transmitting the predefined sequence; and

(h) at least one paging receiver responsive to the transmitted predefined sequence including paging signaling information and voice information, said receiver for reproducing the transmitted voice information in response to the transmitted signaling information being decoded.