Paging system using LPC speech encoding with an adaptive bit rate

• US 4,701,943 A
• Filed: 11/12/1986
• Issued: 10/20/1987
• Est. Priority Date: 12/31/1985
• 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:
  US06/930,072
• Time in Patent Office: 342 Days
• Field of Search: 179/2 EC, 179/2 E, 179/2 EB, 179/18 BE, 340/311.1, 340/825.44, 340/825.48, 370/84
• 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 signalling 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 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 said paging system at any particular time and producing an output signal related to said system loading;

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

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

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

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

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

(a) inputting voice signals comprising paging messages;

(b) periodically measuring whether the paging system loading has increased or decreased since the last period;

(c) generating a variable signal which indicates a system load value;

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

(e) combining said LPC encoded digital voice signals with paging signalling information to generated a composite paging signal; and

(f) transmitting said composite paging signal.