Dispatch trunked radio system

• US 4,692,945 A
• Filed: 11/19/1986
• Issued: 09/08/1987
• Est. Priority Date: 12/31/1984
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Zdunek, Kenneth J.
• Primary Examiner(s): NG, JIN FAY
• Application Number:
  US06/933,367
• Time in Patent Office: 293 Days
• Field of Search: 455/15, 455/17, 455/31, 455/34, 455/38, 455/53, 455/54, 455/56, 455/62, 371/39, 371/45, 370/82, 370/94, 370/95, 370/110.1, 379/63
• US Class Current: 455/17
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• 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

The present invention contemplates an improved dispatch trunked radio system which provides for individual subscriber to subscriber communication as well other enhanced trunking features. An expanded "dual-word" signalling protocol provides an improvement over prior "single word" signalling protocols by increasing the versatility of commands which may be communicated between the components of the trunked radio system. The "dual-word" signalling protocol of the present invention remains compatible with prior "single-word" subscriber units.

Claims

1. An improved dispatch trunked radio system having variable length messages, said system comprising:

(a) a plurality of subscriber units which are capable of generating inbound signalling information and of receiving outbound signalling information in accordance with a signalling scheme, said signalling scheme comprising, in part, inbound messages including;

(i) a first inbound data word of a predetermined bit length organized in fields, wherein a first fixed field portion represents a requesting subscriber unit'"'"'s unique identification code, and a second fixed field which comprises a call type field representing system control codes wherein at least one of said system control codes comprises an instruction to search for a second subsequent data word or to decode said first inbound signalling word as a single word message; and

(ii) an optional second inbound data word of a predetermined bit length organized in fields, wherein a first fixed field portion represents a target subscriber unit'"'"'s unique identification code, or a system feature code depending on the contents of the call type field of said first inbound signalling word, and a second fixed field represents a desired call type; and

(b) central control unit means for decoding said first inbound data word and said optional second inbound data word and for generating outbound signalling information in accordance with said signalling scheme, wherein said outbound signalling information includes transmission of channel grants to said subscriber units based on a predetermined control algorithm, wherein said channel grants include at least;

(i) a first outbound data word of a predetermined bit length organized in fields, said data word having a fixed prefix field corresponding to a target subscriber unit I.D., an individual bit portion, and a status field; and

(ii) a second outbound data word of a predetermined bit length organized in fields, having a first fixed field, an individual bit field and a second channel status field, said second channel status field containing information for interpreting the contents of said fixed prefix field and said first fixed field of said outbound data words.

2. The apparatus as recited in claim 1 wherein said optional second inbound data word must be received within a predetermined time of the receipt of said first inbound data word.

3. The apparatus as recited in claim 1 wherein said inbound messages are sent in predetermined time slots.

4. The apparatus as recited in claim 1 wherein said outbound channel grants contain a preamble having a sync signal.

5. The apparatus as recited in claim 1 wherein said first and second inbound data words are decoded separately, one word at a time.

6. The apparatus as recited in claim 1 wherein the receipt of two first inbound data words in a sequence causes the first inbound data word received to be discarded.

7. The apparatus as recited in claim 1 wherein each of said first and second inbound data words further contain error correction codes which ensure said first and second inbound data words were received in consecutive time slots.

8. A method of controlling a dispatched trunked communication system having a plurality of subscriber units, a plurality of trunked repeaters and a fixed end central controller coupled to said trunked repeaters wherein said subscriber units communicate with said trunked repeaters under the control of said fixed end central controller, said method comprising the steps of:

(a) a subscriber unit requesting service by transmitting a voice channel request in the form of an inbound dual signalling word to the fixed end central controller on a predetermined inbound control channel through said trunked repeaters;

(b) receiving with said subscriber unit a voice channel grant in the form of a dual word outbound signalling word on an outbound control channel said dual word outbound signalling word generated by said fixed end central controller and transmitted by said trunked repeaters;

(c) receiving with said subscriber unit a high speed hand shake on an outbound assigned voice channel from the fixed end central controller, wherein the high speed hand shake contains identification code of the requesting subscriber unit;

(d) receiving with the fixed end central controller a high speed acknowledge signal transmitted by the subscriber units on the predetermined inbound control channel;

(e) transmitting low speed acknowledge signal from the subscriber unit to the fixed end central controller through the trunked repeater;

(f) receiving voice and a low speed subaudible hand shake with said subscriber unit, transmitted by the trunked repeaters from the fixed end central controller;

(g) simultaneously communicating a subaudible hand shake signal and a voice signal between the subscriber unit and the fixed end central controller on the assigned voice channel while communicating with said fixed end central controller;

(h) transmitting with a repeater to the subscriber unit the voice channel generated by the fixed end central controller in the form of a dual word on the outbound control channel for the duration of the requesting subscriber unit transmission;

(i) transmitting from the subscriber unit to the fixed end central controller a subaudible disconnect signal indicating end of transmission to the fixed end central controller; and

(j) transmitting with a repeater to the subscriber unit a subaudible central disconnect signal with the fixed end central controller on the outbound voice channel after receiving the end of transmission signal from the subscriber unit.

9. The apparatus as recited in claim 8 wherein said optional second data word must be received within a predetermined time of the receipt of said first data word.

10. The apparatus as recited in claim 8 wherein said inbound messages are sent in predetermined time slots.

11. The apparatus as recited in claim 8 wherein said outbound messages contain a preamble having a sync signal.

12. The apparatus as recited in claim 8 wherein said first and second words are decoded separately, one word at a time.

13. The apparatus as recited in claim 8 wherein the receipt of two first words in a sequence cause the first word received to be discarded.

14. The apparatus as recited in claim 8 wherein each of said first and second data words further contain error correction codes which ensure said first and second words were received in consecutive time slots.

15. A method of transmitting and receiving messages between a transmitter and a receiver, comprising the steps of:

in the transmitter;

(a) transmitting a first data packet having at least one dedicated field contained therein, wherein said dedicated field is comprised of coded data that is first data packet information, and wherein said dedicated field can selectively be an indication that an associated second data packet will be transmitted following transmission of said first data packet; and

(b) optionally transmitting a second data packet, wherein said second data packet includes at least one field that comprises coded data that is second data packet information, provided that said second data packet is only transmitted following transmission of a first data packet having said indication that an associated second data packet will be subsequently transmitted; and

in the receiver;

(c) decoding, if received by said receiver, said first data packet to determine its contents, such that;

(1) if said first data packet does not include said indication that an associated second data packet will be transmitted, said receiver accepts information contained in said first data packet;

(2) if said first data packet does include said indication that an associated second data packet will be transmitted, said receiver does not yet accept information contained in said first data packet; and

(d) decoding, if transmitted by said transmitter and received by said receiver, said second data packet to determine its contents, such that;

(1) if said second data packet was not preceded by reception, within a predetermined period of time, of a first data packet having an indication that an associated second data packet would be subsequently transmitted, said receiver will not accept information contained in said second data packet; and

(2) if said second data packet was preceded by reception, within a predetermined period of time, of a first data packet having an indication that an associated second data packet would be subsequently transmitted, said receiver will accept information contained in both said second data packet and in said first data packet.

16. A method of receiving at least one data packet in a receiver, wherein said data packet may be selectively comprised of:

a first data packet that includes data that is first data packet information, and wherein said first data packet can selectively include an indication that an associated second data packet will be transmitted following transmission of said first data packet; and

an optional second data packet, wherein said second data packet includes at least some data that is second data packet information;

the method comprising the steps of;

(a) receiving a data packet;

(b) decoding said data packet to determine its contents;

(c) if said data packet includes said indication that an associated second data packet will be transmitted, storing at least some information representative of said data packet in memory to await reception of said second data packet;

(d) if said data packet includes data that is first data packet information, but does not includes said indication that an associated second data packet will be transmitted, accepting information contained in said data packet; and

(e) if said data packet includes data that is second data packet information, accepting information contained in said data packet, unless reception of said data packet did not occur within a predetermined time period following reception of a first data packet that included said indication that an associated second data packet will be transmitted.