Telecommunications system

• US 5,208,812 A
• Filed: 11/26/1990
• Issued: 05/04/1993
• Est. Priority Date: 01/27/1989
• Status: Expired due to Fees

• Current Assignee: Shaye Communications Ltd (AT&T, Inc.), British Telecommunications PLC (BT Group PLC), Ferranti Creditphone Limited, GEC Plessey Telecommunications Limited, Kc, Lucent Technologies Wireless Limited Capital House (Nokia Corporation), Orbitel Mobile Communications Ltd., Phonepoint Limited The Quadrangle, Mercury Communications Ltd. (Siemens AG)
• Original Assignee: Shaye Communications Ltd (AT&T, Inc.), British Telecommunications PLC (BT Group PLC), Ferranti Creditphone Limited, GEC Plessey Telecommunications Limited, Orbitel Mobile Communications Ltd., Phonepoint Limited, Mercury Communications Ltd. (Siemens AG), STC PLC (f/k/a Standard Telephones and Cables)
• Inventors: Jones, Emlyn, Dudek, Michael T., Proctor, Peter N., Goodings, Rupert, Odhams, David C.
• Primary Examiner(s): Kuntz, Curtis
• Assistant Examiner(s): GHEBRETINSAE, TEMESGHEN
• Application Number:
  US07/573,308
• Time in Patent Office: 890 Days
• Field of Search: 370/29, 370/105.4, 370/100.1, 370/29, 375/116
• US Class Current: 370/280
• CPC Class Codes: H04J 3/0602 Systems characterised by the synchronising information used
• CPC Class Codes: H04J 3/0652 Synchronisation among time division multiple access [TDMA] nodes, e.g. time triggered protocol [TTP] bus network with centralized control in which slots are of a TDMA packet structure H04L12/4035
• CPC Class Codes: H04L 7/041 using special codes as synchronising signal
• CPC Class Codes: H04M 1/72505 Radio link set-up procedures
• CPC Class Codes: H04M 1/733 with a plurality of base stations connected to a plurality of lines for selection in cordless PBX H04W84/16

Abstract

A communication procedure suitable for a cordless telephone system involves time division duplex radio communication between a handset 11 and a base station 3 using alternating bursts of transmission over a single radio channel. Once a radio link has been set up, initial transmissions carry a synchronization logical channel S and a signalling logical channel D multiple together, bu the link may switch to bursts carrying a communications logical channel B for the speech data and the signalling logical channel D. Bursts synchronization is achieved by the asynchronous detection of words in a synchronization channel S. These words have bit patterns reducing the probability of incorrect asynchronous detection thereof. If one part ceases to receive handset signals from the other, it transmits a special signal to inform the other part. This enables both parts to detect the failure of a link at substantially the same time, so that their actions to reestablish the link are synchronized.

Claims

1. A telecommunication system comprising:

a device of a first type and a plurality of devices of a second type, said device of the first type comprising communication means for conducting time-division two-way communication with any one of said devices of the second type over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the devices is completed before transmission of the next of said alternating bursts by the other of the devices is begun, and each of said devices of the second type comprising communication means for conducting said time-division two-way communication with the device of the first type;

the device of the first type comprising means for providing said bursts such that at least some of the bursts contain a first synchronisation pattern or one of a group of first synchronization patterns, and detecting means for asynchronously detecting a second synchronisation pattern or one of a group of second synchronisation patterns in a received burst to enable it to determine timing information about said received burst, each device of the second type comprising means for producing said bursts such that at least some of the bursts contain said second synchronisation pattern or one of said group of second synchronisation patterns, and detecting means for asynchronously detecting said first synchronisation pattern for one of said group of first synchronisation patterns in a received burst to enable it to determine timing information about said received burst, said first synchronization pattern or patterns being different from said second synchronization pattern or patterns, said detecting means in the plurality of devices of the second type not responding to reception of the second synchronisation pattern or patterns, whereby each of said plurality of devices of the second type does not respond to reception of transmissions or any other device of the second type.

3. A system according to claim 1 wherein said time-division two-way communication may be performed by any one of a plurality of devices of the first type, and detecting means in the plurality of devices of the first type do not respond to reception of the first synchronisation pattern or patterns, whereby each of the plurality of devices of the first type does not respond to transmissions by any other device of the first type.

4. A system according to claim 1 or claim 3 wherein the burst producing means of each said device of one type transmits a predetermined synchronisation pattern while attempting to initiate communication by said radio signals with a device of the other type, and subsequently transmits a different predetermined synchronisation pattern after said communication has been initiated.

2. A method of telecommunication comprising the steps of:

establishing time-division two-way communication over a radio channel between a device of a first type, acting at a given time as one of a receiver and a transmitter, and any one of a plurality of devices of a second type, acting at said given time as the other of said receiver and transmitter, by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the devices is completed before transmission of the next of said alternating bursts by the other of the device is begun;

producing said bursts such that at least some of the bursts contain a synchronisation pattern;

asynchronously detecting said synchronisation pattern by the receiver to enable it to determine timing information about the received bursts, the device of the first type transmitting a first synchronisation pattern or one of a group of first synchronisation patterns and the devices of the second type transmitting a second synchronisation pattern or one of a group of second synchronisation patterns, the first synchronisation pattern or patterns being different from the second synchronisation pattern or patterns; and

preventing the plurality of devices of the second type from responding to reception of the second synchronisation pattern or patterns, whereby each of said plurality of devices of the second type does not respond to reception of transmissions by any other device of the second type.

22. A method according to claim 2, wherein said time-division two-way communication may be performed by any one of a plurality of devices of the first type, and the plurality of devices of the first type do not respond to reception of the first synchronisation pattern or patterns, whereby each of the plurality of devices of the first type does not respond to transmissions by any other device of the first type.

23. A method according to claim 2 or claim 22, wherein the step of providing said bursts of a particular format includes a said device of one type transmitting a predetermined synchronisation pattern while attempting to initiating communication by said radio signals with a device of the other type, and subsequently transmitting a different predetermined synchronisation pattern after said communication has been initiated.

5. A telecommunication system comprising:

first and second devices having communication means for providing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next burst by the other of the first and second devices is begun;

means for producing bursts such that at least some of the bursts transmitted by a said device are bursts of a particular format and contain a synchronisation pattern of L bits of data and also bits of variable data;

means for asynchronously detecting said synchronisation pattern by the receiver to enable it to determined the timing information about the transmitted bursts of said particular format;

means in the receiving device which determines the synchronisation pattern to be present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

the arrangement of bits in each said burst of said particular format being such that in any consecutive string of L bits of data in the burst, there are less than L-K bits of variable data.

7. A system according to claim 5 wherein the arrangement of bits in each said burst of said particular format is such that in any consecutive string of L bits of data in the burst of said particular format, there are no more than L-K-6 bits of variable data.

6. A method of telecommunication in which first and second devices communicate with each other, comprising the steps of:

performing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

producing said bursts such that at least bursts of a particular format transmitted by a said device contain a synchronisation pattern of L bits of data and also bits of variable data;

asynchronously detecting said synchronisation pattern by the receiver to enable it to determine timing information about the transmitted bursts of said particular format;

determining in the receiver that the synchronisation pattern is present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

arranging the bits in each said burst of said particular format such that in any consecutive string of L bits of data in the burst of said particular format, there are less than L-K bits of variable data.

24. A method according to claim 6, wherein the arrangement of bits in each said burst of said particular format is such that in any consecutive string of L bits of data in the burst of said particular format, there are no more than L-K-6 bits of variable data.

8. A telecommunication system comprising:

first and second devices having communication means for providing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

means for producing bursts including alternating bursts, such that at least some of the bursts produced by said means for producing bursts are bursts of a particular format of digital data and comprise a first portion having a repeating pattern of fixed value and variable bits and a second portion comprising an L-bit synchronisation pattern;

means for asynchronously detecting said synchronisation pattern by the receiving device to enable it to determine timing information about the bursts of said particular format; and

means in the receiving device which determines the synchronisation pattern to be present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer;

the L-bit synchronisation pattern and the repeating pattern of fixed value and variable bits being such that a string of L successive bits of the repeating pattern, starting at any position in a repeat of the pattern, matches less than L-K bits of the synchronisation pattern even if it is assumed that every variable bit in the string provides a match.

10. A system according to claim 8, wherein any said string of L successive bits of the said repeating pattern matches no more than L-K-2 bits of the synchronisation pattern even if it is assumed that every variable bit of the string provides a match.

16. A system according to any one of claims 5, 7, 8, 10, 11, and 13 to 15 in which K is not zero.

17. A system according to claim 16 in which K is two.

46. A system according to claim 8 wherein said bursts of said particular format are not said alternating bursts.

9. A method of telecommunication in which first and second devices communicate with each other, comprising the steps of:

performing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

producing bursts such that at least bursts of a particular format of digital data comprise a first portion having a repeating pattern of fixed value and variable bits and a second portion comprising an L-bit synchronisation pattern;

asynchronously detecting said synchronisation pattern by the receiver to enable it to determine timing information about the bursts of said particular format;

determining the synchronisation pattern to be present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

selecting the L-bit synchronisation pattern and the repeating pattern of fixed value and variable bits such that a string of L successive bits of the repeating pattern, starting at any position in a repeat of the pattern, matches less than L-K bits of the synchronisation pattern even if it is assumed that every variable bit in the string provides a match.

25. A method according to claim 9, wherein any said string of L successive bits of the said repeating pattern matches no more than L-K-2 bits of the synchronisation pattern even if it is assumed that every variable bit of the string provides a match.

11. A telecommunication system comprising:

first and second devices having communication means for providing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

means for producing bursts such that at least some are bursts of a particular format of digital data and comprise an L-bit synchronisation pattern;

means for asynchronously detecting said synchronisation pattern by the receiving device to enable it to determine timing information about the bursts of said particular format; and

means in the receiver to determine the synchronisation pattern to be present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer;

the synchronisation pattern being adjacent a portion of the burst made up of fixed value bits, and the number of matches between the synchronisation pattern and any string of L successive bits of the burst of said particular format composed only of at least a part of said portion of fixed value bits and an adjacent part of the synchronisation pattern being less than L-K.

13. A system according to claim 11, wherein said burst producing means produces a preset synchronisation pattern from among a predetermined plurality of L-bit synchronisation patterns, and the number of matches between anyone of said plurality of synchronisation patterns and any string of L successive bits of the burst composed only of any other of said plurality of synchronisation patterns or at least a part of the said portion of fixed value bits and an adjacent part of any other said synchronisation pattern is less than L-K.

14. A system according to claim 13 wherein, for at least some of the said plurality of synchronisation patterns, the said number of matches does not exceed L-K-8.

15. A system according to claim 13, wherein, for all of the said plurality of synchronisation patterns, the said number of matches does not exceed L-K-7.

42. A system according to claim 13 wherein said first device comprises a said means for producing bursts of said particular format such that a particular burst of said particular format from the first device comprises a first one of said plurality of synchronisation patterns, and said second device comprises a said means for producing bursts of said particular format such that a particular burst of said particular format from the second device comprises a second one of said plurality of synchronisation patterns.

43. A system according to claim 13 wherein said burst producing means comprises means to variably select different said preset synchronisation patterns from among said plurality of synchronisation patterns at different times.

12. A method of telecommunication in which first and second devices communicate with each other, comprising the steps of:

performing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

producing bursts such that at least bursts of a particular format of digital data comprise an L-bit synchronisation pattern;

asynchronously detecting said synchronisation pattern by a receiver to enable it to determine timing information about bursts of said particular format;

determining the receiver that the synchronisation pattern is present in the received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

arranging the burst of said particular format such that the synchronisation pattern is adjacent a portion of the burst of said particular format made up of fixed value bits, and the number matches between the synchronisation pattern and any string of L successive bits of the burst of said particular format composed only of at least a part of the said portion of fixed value bits and an adjacent part of the synchronisation pattern being less than L-K.

26. A method according to claim 12, wherein said step of producing bursts of a particular format comprises producing a preset synchronisation pattern from among a predefined plurality of L-bit synchronisation patterns, and the number of matches between any of said plurality of synchronisation patterns and any string of L successive bits of the particular burst composed only of any other said synchronisation pattern or at least a part of the said portion of fixed value bits and an adjacent part of any other said synchronisation pattern is less than L-K.

27. A method according to claim 26, wherein, for at least some of the said plurality of synchronisation patterns, the said number of matches does not exceed L-K-8.

28. A method according to claim 26, wherein, for all of said plurality of synchronisation patterns, the said number of matches does not exceed L-K-7.

29. A method according to any one of claims 6, 9, 12, 24, 25, 26, 27 and 28, wherein K is not zero.

30. A method according to any one of claims 6, 9, 12, 24, 25, 26, 27 and 28, wherein K is two.

44. A method according to claim 26 wherein said preset synchronisation pattern comprises a first synchronisation pattern or one of a first group of synchronisation patterns when said step of producing bursts of said particular format is carried out in said first device and said preset synchronisation pattern comprises a second synchronisation pattern or one of a second group of synchronisation patterns when said step of producing burst of said particular format is carried out in said second device.

45. A method according to claim 26 wherein said preset synchronisation pattern is a different one of said plurality of synchronisation patterns on different occasions when said step of producing particular bursts is carried out.

18. A telecommunication system comprising:

first and second devices having communication means for providing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

means for producing bursts such that at least some are bursts of a particular format of digital data and comprise an L-bit synchronisation pattern;

means for asynchronously detecting said synchronisation pattern by a receiver to enable it to determine timing information about the bursts of said particular format;

the synchronisation pattern having a peak self-correlation side lobe value of not more than +2, for any amount of offset, where the self-correlation side lobe value at an amount of offset is defined as the number of matches between bits of the pattern and itself offset by the amount, minus the number of mismatches between the bits of the pattern and itself at the same amount of offset.

19. A method of telecommunication in which first and second devices communicate with each other, comprising the steps of:

performing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

producing bursts such that at least bursts of a particular format of digital data comprise an L-bit synchronisation pattern;

asynchronously detecting said synchronisation pattern by a receiver to enable it to determine timing information about the bursts of said particular format; and

arranging the synchronisation pattern to have a peak self-correlation side lobe value of not more than +2, for any amount of offset, where the self-correlation side lobe value at an amount of offset is defined as the number of matches between bits of the pattern and itself offset by the amount, minus the number of mismatches between the bits of the pattern and itself at the same amount of offset.

20. A telecommunication system comprising:

first and second devices having communication means for providing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

means for producing bursts such that at least some are bursts of a particular format of digital data and comprise a 24-bit synchronisation pattern which, when given in hexadecimal format, is one of;

BE4E50;

41B1AF;

EB1B05;

14E4FA;

0A727D;

F58D82;

A0D8D7; and

5F2728;

means for asynchronously detecting said synchronisation pattern by a receiver to enable it to determine timing information about the bursts of said particular format.

21. A method of telecommunication in which first and second devices communicate with each other, comprising the steps of:

performing time-division two-way communication between said devices over a radio channel by exchanging radio signals in alternating bursts carrying digital data, such that during the time-division two-way communication, transmission of one of said alternating bursts from one of the first and second devices is completed before transmission of the next of said alternating bursts by the other of the first and second devices is begun;

producing bursts such that at least bursts of a particular format of digital data and comprise a 24-bit synchronisation pattern when, given in hexadecimal format, is one of;

BE4E50;

41B1AF;

EB1B05;

14E4FA;

0A727D;

F58D82;

A0D8D7; and

5F2728;

asynchronously detecting said synchronisation pattern by a receiving device to enable it to determine timing information about the bursts of said particular format.

31. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

detecting means for asynchronously detecting a first synchronisation pattern or one of a group of first synchronisation patterns in a received burst to enable the telecommunication device to determine timing information about said received burst; and

means for producing said bursts such that at least some of the bursts contain a second synchronisation pattern or one of a group of second synchronisation patterns;

said first synchronisation pattern or patterns being different from said second synchronisation pattern or patterns and said detecting means not responding to said second synchronisation pattern or patterns.

32. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for producing bursts for transmission by the telecommunication device at least some of which are bursts of a type containing bits of variable data and a synchronisation pattern of L bits of data, the arrangement of bits in bursts of said type being such that any consecutive string of L bits of data in the burst contains less than L-K consecutive bits of variable data, where K is a predetermined value which is zero or a positive integer.

33. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

detecting means for asynchronously detecting a synchronisation pattern of L bits of data in a received burst to enable the telecommunication device to determine timing information about the burst; and

decoding means for decoding at least some received bursts according to a predetermined burst format;

said detecting means determining that said synchronisation pattern is present in received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

said predetermined format being such that a burst in said format contains bits of variable data and said synchronisation pattern, and in any consecutive string of L bits of data in a burst in said format there are less than L-K consecutive bits of variable data.

34. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for producing bursts for transmission by the telecommunication device including said alternating burst such that at least some of the bursts produced by said means for producing bursts are bursts of a particular format of digital data such that a burst in said particular format comprises a first portion having a repeating pattern of fixed value bits and variable bits and a second portion comprising an L bit synchronisation pattern, the L bit synchronisation pattern and the repeating pattern of fixed value bits and variable bits being such that a string of L successive bits of the repeating pattern, starting at any position in a repeat of the pattern, matches less than L-K bits of the synchronisation pattern even if it is assumed that every variable bit in the string provides a match, where K is a predetermined value which is zero or a positive integer.

47. A device according to claim 34 wherein said bursts of said particular format are not said alternating bursts.

35. A telecommunication device for establishing synchronous time-division two-way communication with another device over a radio channel by exchanging radio signals with said other device in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

detecting means for asynchronously detecting an L bit synchronisation pattern in a received burst to determine timing information about the burst, said detecting means determining that said synchronisation pattern is present in received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in a no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

decoding means for decoding at least some received bursts according to a particular format of digital data such that a burst in said particular format comprises a first portion having a repeating pattern of fixed value bits and variable bits and a second portion comprising said L bit synchronisation pattern;

the L bit synchronisation pattern and the repeating pattern of fixed value bits and variable bits being such that a string of L successive bits of the repeating pattern, starting at any position in a repeat of said pattern, matches less than L-K bits of the synchronisation pattern even if it is assumed that every variable bit in the string provides a match.

36. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for producing bursts for transmission by the telecommunication device at least some of which are bursts of a particular format of digital data such that a burst in said particular format comprises an L bit synchronisation pattern adjacent a portion of the burst made up of fixed value bits, the L bit synchronisation pattern and said fixed value bits being such that the number of matches between the synchronisation pattern and any string of L successive bits of a burst in said particular format which string is composed only of at least a part of said portion of fixed value bits and an adjacent part of the synchronisation pattern is less than L-K, where K is a predetermined value which is zero or a positive integer.

37. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

detecting means for asynchronously detecting an L bit synchronisation pattern in a received burst to determine timing information about the burst, said detecting means determining that said synchronisation pattern is present in received data when a comparison operation between the received data and a stored copy of the synchronisation pattern results in a no more than K bits of the received data failing the comparison, where K is zero or a positive integer; and

decoding means for decoding at least some received bursts according to a particular format of digital data such that a burst in said particular format comprises an L bit synchronisation pattern adjacent a portion of the burst made up of fixed value bits;

the L bit synchronisation pattern and said fixed value bits being such that the number of matches between the synchronisation pattern and any string of L successive bits of a burst in said particular format which string is composed only of at least a part of said portion of fixed value bits and an adjacent part of the synchronisation pattern is less than L-K.

38. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for producing bursts for transmission by the telecommunication device at least some of which are bursts of a particular format of digital data such that a burst in said particular format comprises an L bit synchronisation pattern having a peak self-correlation side lobe value of not more than +2 for any amount of offset, where the self-correlation side lobe value at an amount of offset is defined as a number of matches between bits of the pattern and itself offset by the amount, minus the number of mismatches between bits of the pattern and itself at the same amount of offset.

39. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for asynchronously detecting a predetermined synchronisation pattern in a received burst to determine timing information about the burst, the predetermined synchronisation pattern being such that it has a peak self-correlation side lobe value of not more than +2 for any amount of offset, where the self-correlation side lobe value at an amount of offset is defined as a number of matches between bits of the pattern and itself offset by the amount, minus the number of mismatches between bits of the pattern and itself at the same amount of offset.

40. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for producing bursts for transmission by the telecommunication device at least some of which are in a particular format of digital data such that a burst in said particular format comprises a 24-bit synchronisation pattern selected from the group, defined in hexadecimal format;

BE4E50;

41B1AF;

EB1B05;

14E4FA;

0A727D;

F58D82;

A0D8D7; and

5F2728.

41. A telecommunication device for establishing time-division two-way communication with another device over a radio channel by exchanging radio signals in alternating bursts carrying digital data such that, during the time-division two-way communication, reception of a said burst from said other device is completed before transmission of the next burst by said telecommunication device is begun;

said telecommunication device comprising;

means for asynchronously detecting in a received burst a synchronisation pattern selected from the group, defined in hexadecimal format;

BE4E50;

41B1AF;

EB1B05;

14E4FA;

0A727D;

F58D82;

A0D8D7; and

5F2728, to determine timing information about the burst.