Auto-alignment of clear voice and low speed digital data signals in a simulcast system

• US 5,842,134 A
• Filed: 09/28/1995
• Issued: 11/24/1998
• Est. Priority Date: 09/28/1995
• Status: Expired due to Fees

• Current Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Canada, Robert, Brown, Thomas A.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Bhattacharya, Sam
• Application Number:
  US08/535,932
• Time in Patent Office: 1,153 Days
• Field of Search: 455/20, 455/22, 455/33.4, 455/51.1, 455/51.2, 455/53.1, 455/56.1, 455/502, 455/503, 455/507, 455/517, 455/524, 455/67.1, 455/67.4, 455/67.6, 455/74, 370/522, 370/527, 370/528, 370/529, 375/363, 375/364
• US Class Current: 455/503
• CPC Class Codes: H04H 20/67 Common-wave systems, i.e. using separate transmitters operating on substantially the same frequency

Abstract

In a wide band radio frequency (RF) simulcast communications system analog voice signals are distributed in a digitized form over high speed data channels and processed as high speed data. A conventional Ericsson, Inc. EDACS™ simulcast communications system is improved by altering the apparatus and manner by which "clear voice" (unencrypted analog voice) is distributed from a control point and "aligned" at multiple transmitter sites for simultaneous RF broadcasting. In the improved arrangement, the EDACS™ simulcast system inherent digital data stream alignment process produces the requisite time domain alignment for the digitized "clear voice" signals without the need for costly analog audio alignment procedures and equipment.

Claims

1. In a simulcasting radio frequency (RF) communications system of the type having a central site distributing one or more channels of high speed digital data and unencrypted analog audio information to plural RF transmitter sites, wherein signals received at each said transmitter site exhibit time ambiguities with respect to signals received at another said transmitter site, and wherein said transmitter sites include a high speed digital data resynchronization circuit means for synchronizing the high speed digital data between said transmitter sites prior to simulcast transmitting, an improved method for distribution of unencrypted analog voice signals (clear voice) and/or low speed digital data for simulcast transmissions, comprising the steps of:

(a) converting unencrypted analog voice signals to digital voice signals at said central site;

(b) inserting said digital voice signals and/or low speed digital data onto one or more preexisting simulcast system high speed digital data communications channel for distribution to a plurality of simulcast transmitter sites;

(c) receiving said digital voice signals and/or low speed digital data at said plurality of simulcast transmitter sites via said high speed digital data channel; and

(d) aligning received high speed digital data communications channel information using said high speed digital data resynchronization circuit means, said digital voice signals and/or low speed digital data received via said high speed digital data channel being automatically aligned for simulcasting by said resynchronization means.

2. A method for distribution of unencrypted analog voice signals and/or low speed data as in claim 1 wherein unencrypted analog voice signals and/or low speed data are converted to a 9.6k baud digital signal for distribution via said high speed digital data channel.

3. A method for distribution of analog voice signals as in claim 2 wherein the preexisting simulcast system high speed digital data communications channel a 9.6k baud digital data communication channel.

4. A method for distribution of analog voice signals as set forth in claim 2, wherein an analog tone signal is embedded in analog voice signals and said step (a) of converting unencrypted analog voice signals incorporates converting analog voice signals along with an embedded tone signal into digital signals;

and step (c) of receiving and aligning said digital voice signal is followed by a further step of extracting said embedded tone signal from the digital voice signals.