Narrow band simulcast system having low speed data distribution

• US 5,477,539 A
• Filed: 07/23/1993
• Issued: 12/19/1995
• Est. Priority Date: 07/23/1993
• Status: Expired due to Term

• Current Assignee: Pine Valley Investments, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Ericsson, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Brown, Thomas A.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): NGO, RICKY QUOC
• Application Number:
  US08/095,858
• Time in Patent Office: 879 Days
• Field of Search: 370/84, 370/32, 370/47, 370/95.2, 370/95.3, 370/100.1, 455/33.1, 455/56.1, 455/57.1, 455/51.1, 455/51.2
• US Class Current: 370/312
• CPC Class Codes: H04J 3/0629 in a network, e.g. in combination with switching or multiplexing, slip buffers
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04W 4/10 Push-to-Talk [PTT] or Push-On-Call services
• CPC Class Codes: H04W 76/45 for Push-to-Talk [PTT] or Push-to-Talk over cellular [PoC] services
• CPC Class Codes: H04W 84/08 Trunked mobile radio systems

Abstract

A "narrow band" public service trunking (PST) simulcast radio frequency transmission system having high-speed and low-speed digital data access capabilities in addition to analog voice operates in the 900 MHz frequency-range, as distinguished from a conventional "wide band" PST system that operates in the 800 MHz frequency range. In a narrow band PST simulcast system having digital access capabilities, the handling of low speed digital data must be accomplished differently than high speed data since it becomes unique to each channel. This would ordinarily require providing an additional data path for each channel, or a wider band width audio path neither of which is feasible or cost effective. Arrangements are therefore provided for the routing of low-speed data to each transmit site via the high-speed digital data channel path for each site and for holding the high-speed data resynchronization circuitry at each site at its previous latency during the transmission of low-speed data, which would otherwise cause erroneous triggering of the resynchronization circuitry.

Claims

1. In a radio frequency communications system having plural spatially separated RF transmitters all transmitting substantially the same signal at substantially the same radio frequency, said system distributing a common clocking signal to each of said plural transmitters so as to facilitate a substantially simultaneous signal transmission by said plural transmitters and also distributing message data and control signal data to each of said transmitters over a high-speed data channel from a central control point, said central control point including:

switching circuitry which controls routing of either high speed or low speed data transmitted over a single high speed data channel from said central control point to each of said RF transmitters in response to said control signal data; and

, each of said plural RF transmitters including;

a first circuit arrangement which determines, at least in part, timing of high-speed digital data signal transmissions received from said central point over a high speed data channel;

a second circuit arrangement operatively coupled to said first circuit arrangement, which suspends operation of said first circuit in response to said control signal indicating the transmission of low speed-data; and

a third circuit arrangement which provides both high-speed and low-speed data to RF power transmitting circuitry.

2. In a narrow band type public service trunked simulcast radio frequency transmission system having plural transmitter sites, at least one high-speed data channel from a central control point to each transmitter site for carrying message data and control signal data to said transmitter sites, and having high-speed data signal synchronization circuitry associated with said high-speed data channel at each site, a method for providing both high-speed and low-speed digital data over a single high speed data channel to each site, comprising the steps of:

providing low-speed digital data over said high-speed data channel for each site; and

in response to said control signal data, holding the high-speed data synchronization circuitry at each site in an inoperative suspended state during the transmission of low-speed data over said high-speed data channel, thus preventing a triggering of the synchronization circuitry upon reception of low-speed data over said high-speed data channel, so as to maintain a latency condition provided by said circuitry prior to reception of said low-speed data.