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AUDIO STATUS MESSAGING FOR TRUNKED RADIO SYSTEMS

IP.com Disclosure Number: IPCOM000007530D
Original Publication Date: 1995-Nov-01
Included in the Prior Art Database: 2002-Apr-03
Document File: 5 page(s) / 203K

Publishing Venue

Motorola

Related People

Gary John Aitkenhead: AUTHOR

Abstract

A trunked radio system, as shown in Figure I, consists of a trunking system controller (TSC), a control channel base station, a number of tralIic chan- nel base stations and a number of subscriber radio units. Trunked radio systems allow status messages to be sent between radios using signalling packets on the control channel. These status messages are defined by a number of code values which corre- spond to text messages stored in the memory of the radio. When a radio receives a status call, it uses the code value to reference the particular text message in its memory which is then displayed for the user.

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MOTOROLA Technical Developments

8

AUDIO STATUS MESSAGING FOR TRUNKED RADIO SYSTEMS

by Gary John Aitkenhead

PRIOR ART

  A trunked radio system, as shown in Figure I, consists of a trunking system controller (TSC), a control channel base station, a number of tralIic chan- nel base stations and a number of subscriber radio units. Trunked radio systems allow status messages to be sent between radios using signalling packets on the control channel. These status messages are defined by a number of code values which corre- spond to text messages stored in the memory of the radio. When a radio receives a status call, it uses the code value to reference the particular text message in its memory which is then displayed for the user.

  The MPT1327 control channel signalling sequence for radio A sending a status message to radio B is shown in Figure 2. Radio A sends an RQQ (request to send status) packet to the TSC which in turn sends AHYQ (send status) to radio B. Radio B acknowledges receipt of the AHYQ by sending an ACK (acknowledgement) packet back to the TSC. The TSC concludes the transaction by sending an ACK packet to radio A, indicating that the message was successfully received by radio B.

  Figure 3 shows the content of the RQQ packet used in the status message transaction. An RQQ packet comprises the prefix of the calling radio (radio A, in this case) and the identities of the calling (IDENT 2) and called (IDENT 1) radios. (MPT1327 addresses consist of a prefix and a unique identity to specify each radio in the system. Calls are usually between radios with a common prefix so the packet need only contain one prelix.) The status field con- sists of 5 bits allowing up to 32 different status mes- sages to be defined. The message type defines this as an RQQ packet and the parity field is for error detec- tion. The AHYQ packet has exactly the same for- mat as the RQQ packet except the prefix is that of the called radio (radio B, in this case).

When radio B receives the status message, it

decodes the 5-bit status field and displays a text mes- sage corresponding to its content. The radio has a programmable memory (look-up table) which stores text messages corresponding to each of the possible status values which can be decoded. This implies that the text relating to each status number must be pre-programmed in all of the radios making up a fleet so that they all attach the same meaning to each of the possible status values.

  Many radios have an LCD or LED alphanumeric display. This display is usually no larger than a sin- gle line of 15 characters (some radios may have two lines). Therefore status messages are short consisting only ofone or two words. Also displayed is the iden- tity of the radio which sent the status message, and often the display alternates between this and the tex- tual message.

SUMMARY OF THE INVENTION

  Ofien, it is desirable to connect a fixed subscriber radio to a private telephone exchange (PABX) as shown in Figure 4. This...