Browse Prior Art Database

CONFERENCE CALL SYSTEM FOR DUPLEX RADIOS WITHOUT THE NEED FOR BASE

IP.com Disclosure Number: IPCOM000007579D
Original Publication Date: 1996-May-01
Included in the Prior Art Database: 2002-Apr-08
Document File: 3 page(s) / 126K

Publishing Venue

Motorola

Related People

Fuad Mokhtar: AUTHOR [+2]

Abstract

This paper describes a system or algorithm that can be implemented on duplex radios to perform on the air teleconferencing in a very effective and spec- trum efficient way. This system will also solve most problems encountered by conventional simplex and duplex radios during conference call.

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MOTOROLA Technical Developments

CONFERENCE CALL SYSTEM FOR DUPLEX RADIOS WITHOUT THE NEED FOR BASE

by Fuad Mokhtar and Pek Bing Teo

ABSTRACT

  This paper describes a system or algorithm that can be implemented on duplex radios to perform on the air teleconferencing in a very effective and spec- trum efficient way. This system will also solve most problems encountered by conventional simplex and duplex radios during conference call.

 tion exchange. -During normal operation, a person on the air can be interrupted at any time.
-Does not require a base station or repeater. All radios are identical and all ofthem serve as repeat- ers among themselves.
-No matter how big the group is, only two chan- nels are required, i.e. the main channel and inter- rupt channel.
-Whoever is on the air can be interrupted by any single person, it is an ideal atmosphere for effec- tive discussion or conference.

PROBLEMS ENCOUNTERED BY THE CONVENTIONAL TWO WAY RADIO:

THEORY OF OPERATION

I) Simplex radio:- -Only one person can talk at one time. -Conversation exchange is done at a very slow rate due to precautidn to avoid conflict carrier. -Unable to interrupt the ongoing transmissions, where sometime it is a must especially during an emergency.

II) Duplex radio:- -Requires a base station. -In the case ofa conference call it requires as many channels as the number of the operating radios plus one monitor channel; not practical for a big group of people.
-Because everybody can talk at the same time, the possibility is there that the conversation gets out of control and the monitor channel get overloaded with people voices.
--In the talkaround mode, the conversation is lim- ited to only two people. No conference ability.

  This system applies to all duplex radios (time, l?equency, code multiplexing, etc.). Channel may refer to tiequency channel, time divided channel, etc.

  Two channels are required; main channel and interrupt channel. The radio must be capable of transmitting at the main channel and receiving at the interrupt channel at the same time and also the reverse (i.e. transmit at interrupt channel and re- ceive at the main channel at the same time). See Figure 1.

  When there is no transmitting activity, all radios are monitoring at main channel (Ch. 1). The first radio (first party) going on the air will first check to see if the main channel (Ch. 1) is busy. If it is not it will transmit on the main channel (Ch. 1) and its receiver will switch to monitor the interrupt channel (Ch. 2), while the rest of the radio is still monitoring the main channel (Ch. l), listening to the first...