Trunked radio repeater system including synchronization of a control channel and working channels

• US 5,125,102 A
• Filed: 01/03/1990
• Issued: 06/23/1992
• Est. Priority Date: 06/03/1987
• Status: Expired due to Term

• Current Assignee: Pine Valley Investments, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Dissosway, Marc A., Cooper, Gerald M., Hughes, Houston H. III, Childress, Jeffrey S.
• Primary Examiner(s): Eisenzopf, Reinhard J.
• Assistant Examiner(s): Urban, Edward
• Application Number:
  US07/464,053
• Time in Patent Office: 902 Days
• Field of Search: 455/32, 455/34, 455/38, 455/49, 455/53, 455/54, 455/56, 455/58, 455/7, 455/11, 455/17, 379/58, 379/59, 379/60, 379/63, 370/105.1, 370/105.2
• US Class Current: 455/9
• CPC Class Codes: H04L 1/1614 using bitmaps
• CPC Class Codes: H04W 84/08 Trunked mobile radio systems

Abstract

A digitally trunked radio repeater system provides substantial improvements in timeliness of channel acquisition and channel drop, and in reliability of critical control signalling. The system uses a much higher digital signalling rate than is typically found in prior art systems, and uses a control channel to convey digital channel request and assignment messages between the central site and mobile transceivers. The mobile radio transceivers transmit channel requests on the control channel (if no response is received, the mobile retries during a retry time window which increases in duration in dependence on the number of retries). The mobile transceiver switches to a working channel in response to an assignement message received on the control channel. Subaudible digital signals transmitted on the control channel and on active working channels allow late entry, shifting to higher priority calls, and other advanced functions. Message and transmission trunking capabilities are both present so as to maximize working channel usage without compromising channel access for high priority communciations. During transmission trunking, called and calling transceivers return to the control channel after each transmission (and called transceivers may be inhibited from transmitting) but grant higher priority to calls from the other transceivers being communciated with to ensure continuity over an entire conversation. Additional functions and fault tolerant features further increase the versatility and reliability of the system.

Claims

1. A method for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said method comprising the steps of:

A. sending, from a first radio unit to a control site over the control channel, request signals including

a. a string of dotting bits to establish bit sync,

b. a predetermined word sync code repeated three times, and

c. a request message of 40 bits repeated three times, each message including

i. 4 bits identifying the message type and type of requested communication,

ii. 11 bits identifying the called unit,

iii. 12 bits identifying the calling unit, and

iv. 12 bits of BCH error detection and correction data;

B. sending, from said control site to said first radio unit over said control channel, assignment signals including

a. a predetermined word sync code,

b. a pair of assignment messages, each being repeated three times and having 40 bits including

i. 4 bits identifying the message type and type of requested communication,

ii. 6 bits providing one-half the identity of the calling unit;

iii. 1 bit identifying the call as a group call or individual call,

iv. 5 bits identifying the assigned working channel,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

C. sending, from said control site over the assigned working channel, confirmation signals including

a. a predetermined word sync code, and

b. a confirmation message of 32 bits repeated three times including

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit identifying whether a group or individual call is being made,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

D. in response to receipt of said confirmation signals, sending, from said first unit over the assigned working channel, digital acknowledgement signals including

a. a relatively longer string of dotting bits, followed by

b. communications over the working channel to the called group or individual unit, and

E. in response to step D(a) and prior to step D(b), sending, from said control site over the assigned working channel, digital release signals including

a. a predetermined word sync code, and

b. two unit-keyed/unmute messages, each repeated three times and being 32 bit messages of the form

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit of filler for optional other uses,

v. 12 bits identifying the calling unit, and

vi. 12 bits of BCH error detection and correction data.

2. A method as in claim 1 further comprising the step of:

subsequent to step E, sending subaudible digital signals over said assigned working channel including new channel assignment messages which are monitored by each unit residing on that working channel for higher priority calls directed to that unit or a predefined group including such unit.

3. A method as in claim 2 further comprising the step of:

subsequent to step E, sending a channel assignment update message over said control channel from the control site to permit late entry of additional called units to the assigned working channel.

4. A method as in claim 3 further comprising the step of:

at the conclusion of communication by said first unit, the transmission from the first unit over said assigned working channel of an unkeyed message including

a. a string of dotting bits,

b. a block of 128 bits repeated four times, each data block being of the form

i. a string of dotting bits,

ii. a predetermined word sync code,

iii. four 8 bit bytes, each transmitted with triple redundancy and defining a 32 bit message having 4 bits identifying the type of message, 2 bits of filler for optional other use, 2 bits providing a frame count for use in subsequently receiving subaudible digital messages in the working channel, 12 bits identifying the calling unit and 12 bits of BCH error detection and correction data.

5. A method as in claim 3 further comprising the step of:

responsive to said unkeyed message, sending, from said control site over said assigned working channel a substantially elongated string of dotting bits, and

all units then assigned to the working channel dropping therefrom and reverting to the control channel in response to said elongated string of dotting bits on the working channel.

6. A system for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said system comprising:

A. means for sending, from a first radio unit to a control site over the control channel, request signals including

a. a string of dotting bits to establish bit sync,

b. a predetermined word sync code repeated three times, and

c. a request message of 40 bits repeated three times, each message including

i. 4 bits identifying the message type and type of requested communication,

ii. 11 bits identifying the called unit,

iii. 12 bits identifying the calling unit, and

iv. 12 bits of BCH error detection and correction data;

B. means for sending, from said control site to said first radio unit over said control channel, assignment signals including

a. a predetermined word sync code,

b. a pair of assignment messages, each being repeated three times and having 40 bits including

i. 4 bits identifying the message type and type of requested communication,

ii. 6 bits providing one-half the identity of the calling unit;

iii. 1 bit identifying the call as a group call or individual call,

iv. 5 bits identifying the assigned working channel,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

C. means for sending, from said control site over the assigned working channel, confirmation signals including

a. a predetermined word sync code, and

b. a confirmation message of 32 bits repeated three times including

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit identifying whether a group or individual call is being made,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

D. means operative in response to receipt of said confirmation signals, for sending, from said first unit over the assigned working channel, digital acknowledgement signals including

a. a relatively longer string of dotting bits, followed by

b. communications over the working channel to the called group or individual unit, and

E. means operative in response to said longer string of dotting bits for sending, from said control site over the assigned working channel, digital release signals including

a. a predetermined word sync code, and

b. two unit-keyed/unmute messages, each repeated three times and being 32 bit messages of the form

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit of filler for optional other uses,

v. 12 bits identifying the calling unit, and

vi. 12 bits of BCH error detection and correction data.

7. A radio unit for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said radio unit comprising:

A. means for sending, to a control site over the control channel, request signals including

a. a string of dotting bits to establish bit sync,

b. a predetermined word sync code repeated three times, and

c. a request message of 40 bits repeated three times, each message including

i. 4 bits identifying the message type and type of requested communication,

ii. 11 bits identifying the called unit,

iii. 12 bits identifying the calling unit, and

iv. 12 bits of BCH error detection and correction data;

B. means for detecting on said control channel, assignment signals including

a. a predetermined word sync code,

b. a pair of assignment messages, each being repeated three times and having 40 bits including

i. 4 bits identifying the message type and type of requested communication,

ii. 6 bits providing one-half the identity of the calling unit;

iii. 1 bit identifying the call as a group call or individual call,

iv. 5 bits identifying the assigned working channel,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

C. means for detecting on the assigned working channel, confirmation signals including

a. a predetermined word sync code, and

b. a confirmation message of 32 bits repeated three times including

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit identifying whether a group or individual call is being made,

v. 12 bits identifying the called group or individual unit, and

vi. 12 bits of BCH error detection and correction data;

D. means operative in response to receipt of said confirmation signals, for sending, over the assigned working channel, digital acknowledgement signals including

a. a relatively longer string of dotting bits, followed by

b. communications over the working channel to the called group or individual unit, and

E. means for detecting on the assigned working channel, digital release signals including

a. a predetermined word sync code, and

b. two unit-keyed/unmute messages, each repeated three times and being 32 bit messages of the form

i. 4 bits identifying the type of message,

ii. 2 bits providing a frame count for use in subsequently receiving subaudible digital messages sent over the working channel,

iii. 1 bit identifying whether trunked operation is in effect,

iv. 1 bit of filler for optional other uses,

v. 12 bits identifying the calling unit, and

vi. 12 bits of BCH error detection and correction data.

8. A method for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said method comprising the step of:

transmitting a given set of channel assignment signals over the control channel in response to a channel assignment request during a time period which is increased in duration as a function of the number of times such channel assignment request has been made.

9. Apparatus for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said apparatus comprising:

transceiver means at a central site for transmitting and receiving radio frequency signals over said control channel and over said working channels; and

means for causing transmission of a given set of channel assignment signals over the control channel in response to a channel assignment request during a time period which is increased in duration as a function of the number of times such channel assignment request has been made.

10. A method for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said method comprising the steps of:

(a) transmitting a bit synchronization signal pattern followed by a predetermined frame synchronization signal pattern over said control channel; and

(b) subsequent to said step (a), transmitting a multiple word digital message frame over said control channel, including the following steps;

(b1) transmitting a first digital message word in a first word slot within said frame; and

(b2) transmitting a second digital message word in a second word slot within said frame,

wherein each said digital message word includes;

a plurality of control bits;

plural groups of identification bits; and

error detection and correction data bits.

11. A method as in claim 10 wherein said transmitting steps (b1) and (b2) comprise transmitting the same digital message word in said first and second word slots.

12. A method as in claim 10 wherein said transmitting steps (b1) and (b2) comprise transmitting a different digital message word in said first and second word slots.

13. A method as in claim 10 wherein said transmitting steps (b1) and (b2) each comprise the following steps:

(i) transmitting a digital signal string;

(ii) inverting said digital signal string;

(iii) transmitting said inverted digital signal string; and

(iv) again transmitting said non-inverted digital signal string.

14. A method for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said method comprising the steps of:

(a) receiving a bit synchronization signal pattern followed by a frame synchronization signal pattern over said control channel;

(b) synchronizing with said synchronization signal patterns; and

(c) subsequent to said step (b), receiving a multiple word digital message frame over said control channel, including the following steps;

(c1) receiving a first digital message word in a first word slot within said frame in accordance with said synchronization obtained by said synchronizing step (b); and

(c2) receiving a second digital message word in a second word slot within said frame in accordance with said synchronization obtained by said synchronizing step,

wherein each said digital message word includes;

a plurality of control bits;

plural groups of identification bits; and

error detection and correction data bits.

15. A method as in claim 14 wherein said receiving steps (c1) and (c2) comprise receiving the same digital message word in said first and second word slots.

16. A method as in claim 14 wherein said receiving steps (c1) and (c2) comprise receiving different digital message words in said first and second word slots.

17. A method as in claim 14 wherein said receiving steps (c1) and (c2) each comprise the following steps:

(i) receiving a digital signal string;

(ii) receiving an inverted version of said digital signal string; and

(iii) again receiving said non-inverted digital signal string.

18. A system for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said system comprising:

means for transmitting a bit synchronization signal pattern followed by a frame synchronization signal pattern over said control channel; and

means transmitting a message frame over said control channel subsequent to said bit and frame synchronization pattern transmissions, including the following;

first transmitting means for transmitting a first digital message word in a first word slot within said frame; and

second transmitting means for transmitting a second digital message word in a second word slot within said frame,

wherein each said digital message control includes;

a plurality of control bits;

plural groups of identification bits; and

error detection and correction data bits.

19. A system as in claim 18 wherein said first and second transmitting means transmit the same digital message word in said first and second word slots.

20. A system as in claim 18 wherein said first and second transmitting means transmit different digital message words in said first and second word slots.

21. A system as in claim 18 wherein said first and second transmitting means each comprise the following:

means for transmitting a digital signal string;

means for inverting said digital signal string;

means for transmitting said inverted digital signal string; and

means for again transmitting said non-inverted digital signal string.

22. A system for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said system comprising:

first receiving means for receiving a bit synchronization signal pattern followed by a frame synchronization pattern over said control channel;

synchronizing means connected to said first receiving means for synchronizing with said received synchronization signal patterns;

first message receiving means operatively coupled to said synchronizing means for receiving a first digital message word in a first word slot within said frame in accordance with said synchronization obtained by said synchronizing means; and

second message receiving means operatively coupled to said synchronizing means for receiving a second digital message word in a second word slot within said frame in accordance with said synchronization obtained by said synchronization means,

wherein each of said digital message word includes;

a plurality of control bits;

plural groups of identification bits; and

error detection and correction data bits.

23. A system as in claim 22 wherein said first and second message receiving means comprise means for receiving the same digital message word in said first and second slots.

24. A system as in claim 22 wherein said first and second message receiving means comprise means for receiving different digital message words in said first and second word slots.

25. A system as in claim 22 wherein said first and second message receiving means each comprise the following:

means for receiving a digital signal string;

means for receiving an inverted version of said digital signal string; and

means for again receiving said non-inverted digital signal string.

26. A method for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said method comprising the steps of:

passing digital message signals between a control site and said individual radio units over said digital control channel in predetermined time slots;

passing digital signals between a control site and at least one radio unit in one of said predetermined time slots over one of said plural working channels;

loosely synchronizing the timing of said digital message signals passed over said working channel with the timing of said digital signals passed over said digital control channel by passing said digital message signals on said working and control channels within the same one of said predetermined time slots;

and

precisely synchronizing the timing of said digital message signals passed over said working channel with the timing of said digital message signals passed over said digital control channel by including bit and frame synchronization patterns over said working and control channels.

27. A method as in claim 26 wherein said digital signals are passed at substantially 9600 bps and said bit synchronization pattern is a dotting sequence of alternating ones and zeros.

28. A system for achieving reliable and prompt communication within a trunked radio repeater system having a digital control channel and plural working channels, which working channels are assigned for temporary use of individual radio units specified by digital control signals on the control channel, said system comprising:

means for passing digital message signals between a control site and said individual radio units over said digital control channel in predetermined time slots;

means for passing digital message signals between a control site and at least one radio unit in one of said predetermined time slots over one of said plural working channels;

means for loosely synchronizing the timing of said digital message signals passed over said working channel with the timing of said digital signals passed over said digital control channel by passing said digital message signals on said working and control channels within the same one of said predetermined time slots; and

means for precisely synchronizing the timing of said digital message signals passed over said working channel with the timing of said digital message signals passed over said digital control channel by including bit and frame synchronization patterns over said working and control channels.

29. A system as in claim 28 wherein said means for passing digital signals pass said digital signals at substantially 9600 bps and said bit synchronization pattern is a dotting sequence of alternating ones and zeros.