Digital cellular TDM system employing 6:1 packing of transcoded information

• US 5,111,454 A
• Filed: 08/16/1990
• Issued: 05/05/1992
• Est. Priority Date: 08/16/1990
• Status: Expired due to Term

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Hung, Nelson C., Welk, John R.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): SAMUEL, TEMESGHEN
• Application Number:
  US07/567,994
• Time in Patent Office: 628 Days
• Field of Search: 370/95.3, 370/109
• US Class Current: 370/337
• CPC Class Codes: H04B 7/2643 using time-division multiple access [TDMA] H04B7/2615, H04B7/2618 take precedence
• CPC Class Codes: H04W 88/08 Access point devices

Abstract

A digital cellular time-division multiple access (TDMA) system including a cellular switch and at least one base site employing 6:1 packing of transcoded information. The system incorporates the VSELP speech encoding algorithm to transcode data input from a cellular switch and a unique packing scheme to compress six messages channels worth of transcoded data into one 20 msec, 160 frame information block for transmission in one TDM timeslot. The compressed transcoded data is transmitted to a base-site on a T1 link where the six message channels worth of transcoded data is un-packed and coded. The coded information is then separated into two groups of three air-interface timeslots where two separate transmitters transmit one group each of three air-interface timeslots on two separate radio carrier frequencies.

Claims

1. A digital radio time-division multiple access (TDMA) system including a land-line telephone system interface and at least one base-site which generates at least one radio carrier frequency, the digital radio time-division multiple access (TDMA) system utilizing an equipment synchronization scheme to maintain equipment synchronization when required, the digital radio time-division multiple access (TDMA) system comprising:

means for compressing information input from at least two message channels from the land-line telephone system into one information block for transmission in one TDM timeslot;

means for inserting a block synchronization scheme into said one information block;

means for reserving a portion of said information block for the equipment synchronization scheme;

means for using a fraction of said reserved portion for said compressed information when equipment synchronization is not required;

means for conveying at least said one TDM timeslot from the land-line telephone system interface to a base-site; and

means, coupled to said means for conveying, for converting said compressed information of at least said one TDM timeslot to coded information for at least two information timeslots for radio transmission on a radio carrier frequency.

2. The digital radio TDMA system of claim 1 wherein said means for conveying said one TDM timeslot is at a rate of 64 Kbit/s.

3. The digital radio TDMA system of claim 1 wherein said means for compressing further comprises means for compressing information input from six message channels into one information block for transmission in one TDM timeslot.

4. The digital radio TDMA system of claim 3 wherein at least one of said six message channels in one 8-bit timeslot from one of six T1 carriers.

5. The digital radio TDMA system of claim 4 wherein said one 8-bit timeslot from one of six T1 carriers is transferred at a rate of 64 Kbit/s.

6. The digital radio TDMA system of claim 4 wherein said means for compressing further comprises first means for obtaining one hundred and sixty 8-bit samples from one of six T1 carriers and second means for obtaining one hundred and sixty 8-bit samples from a second of said six T1 carriers.

7. The digital radio TDMA system of claim 6 wherein said means for compressing further comprises first means for transforming said one hundred and sixty 8-bit samples into a first 160 bit group and second means for transforming said one hundred and sixty 8-bit samples into a second 160 bit group.

8. The digital radio TDMA system of claim 7 wherein said means for compressing further comprises means for packing at least said first 160 bit group and said second 160 bit group into a 1280-bit information block.

9. The digital radio TDMA system of claim 8 wherein said 1280-bit information block is one 160 frame information block of 8-bit timeslots.

10. The digital radio TDMA system of claim 9 wherein said means for compressing further comprises means for adding error control to said one 160 frame information block for each of said packed first 160 bit group and second 160 bit group.

11. The digital radio TDMA system of claim 10 wherein said error control further comprises a cyclic redundancy check (CRC) code.

12. The digital radio TDMA system of claim 11 wherein said CRC code is comprised of 6 bits.

13. The digital radio TDMA system of claim 10 wherein said means for inserting a block synchronization scheme in said one 160 frame information block further comprises means for inserting a bit having a value of `0` into the most significant bit position of frame 1 and inserting bits having alternating values of `1` and `0` into the most significant bit positions for the subsequent 39 frames, a bit having a value of `1` into the most significant bit position of frame 41 and inserting bits having alternating values of `0` and `1` into the most significant bit positions for the subsequent 39 frames, a bit having a value of `0` into the most significant bit position of frame 81 and inserting bits having alternating values of `0` and `0` into the most significant bit positions for the subsequent 39 frames, and a bit having a value of `1` into the most significant bit position of frame 121 and inserting bits having alternating values of `0` and `1` into the most significant bit positions for the subsequent 39 frames.

14. The digital radio TDMA system of claim 10 wherein said synchronization repeats every 80 frames.

15. The digital radio TDMA system of claim 10 wherein said synchronization repeats every 10 msec.

16. The digital radio TDMA system of claim 1 wherein said means for converting further comprises means for receiving said at least one TDM timeslot.

17. The digital radio TDMA system of claim 16 wherein said at least one TDM timeslot further comprises one information block of 160 frames.

18. The digital radio TDMA system of claim 17 wherein said means for converting further comprises means for synchronizing to said one 160 frame information block.

19. The digital radio TDMA system of claim 17 wherein said means for converting further comprises means for checking error control disposed in said one 160 frame information block for each of said multiplexed at least first 160 bit group and second 160 bit group.

20. The digital radio TDMA system of claim 19 wherein said means for converting further comprises means for separating multiplexed first 160 bit group and second 160 bit group disposed in said 160 frame information block.

21. The digital radio TDMA system of claim 20 wherein said means for converting further comprises means for coding each of said separated first 160 bit group and said separated second 160 bit group.

22. The digital radio TDMA system of claim 21 wherein said coded first 160 bit group further comprises a first 324 bit group and said coded second 160 bit group further comprises a second 324 bit group.

23. The digital radio TDMA system of claim 22 wherein said means for converting further comprises means for packing said first 324 bit group into a first information timeslot for radio transmission on a first radio carrier frequency and said second 324 bit group into a second information timeslot for radio transmission on a second radio carrier frequency.

24. A digital radio time-division multiple access (TDMA) system including a land-line telephone system interface and at least one base-site which receives at least one radio carrier frequency, the digital radio time-division multiple access (TDMA) system utilizing an equipment synchronization scheme to maintain equipment synchronization when required, the digital radio time-division multiple access (TDMA) system comprising:

means for converting coded information of at least two information timeslots received from radio transmission on a radio carrier frequency into one information block for transmission in one TDM timeslot, for reserving a portion of said information block for the equipment synchronization scheme, and for using a fraction of said reserved portion for said compressed information when equipment synchronization is not required, coupled to;

means for conveying at least said one TDM timeslot from a base-site to the land-line telephone system interface;

means, coupled to said means for conveying, for synchronizing to said one information block transmitted in at least said one TDM timeslot; and

means, coupled to said means for conveying, for expanding said compressed information of at least said one TDM timeslot.

25. A method which transfers messages from a land-line telephone system interface to at least one base-site in a digital radio time-division multiple access (TDMA) system, the digital radio time-division multiple access (TDMA) system utilizing an equipment synchronization scheme to maintain equipment synchronization when required, the digital radio time-division multiple access (TDMA) system, the method comprising the steps of:

compressing information input from at least two message channels from a land-line telephone system into one information block for transmission in one TDM timeslot;

inserting a block synchronization scheme into said one information block;

reserving a portion of said information block for the equipment synchronization scheme;

using a fraction of said reserved portion for said compressed information when equipment synchronization is not required;

conveying at least said one TDM timeslot from the land-line telephone system interface to a base-site; and

converting said compressed information of said one TDM timeslot, conveyed from said land-line telephone system interface, to coded information for at least two information timeslots for radio transmission on a radio carrier frequency.

26. The method of claim 25 wherein said step of conveying said one TDM timeslot is at a rate of 64 Kbit/s.

27. The method of claim 25 wherein said step of compressing further comprises the step of compressing information input from six message channels into one information block for transmission in one TDM timeslot.

28. The method of claim 27 wherein said at least one of six message channels is one 8-bit timeslot from one of six T1 carriers, and wherein said one 8-bit timeslot from one of six T1 carriers is transferred at a rate of 64 Kbit/s, said step of compressing further comprises the step of obtaining one hundred and sixty 8-bit samples from one of six T1 carriers and obtaining one hundred and sixty 8-bit samples from a second of said six T1 carriers.

29. The method of claim 28 wherein said step of compressing further comprises the step of transforming said one hundred and sixty 8-bit samples into a first 160 bit group and transforming said one hundred and sixty 8-bit samples into a second 160 bit group.

30. The method of claim 29 wherein said step of compressing further comprises the step of packing at least said first 160 bit group and said second 160 bit group into a 1280-bit information block.

31. The method of claim 30 wherein said 1280-bit information block is one 160 frame information block of 8-bit timeslots, said step of compressing further comprises adding error control to said one 160 frame information block for each of said packed first 160 bit group and second 160 bit group.

32. The method of claim 31 wherein said step of adding error control further comprises the step of generating a cyclic redundancy check (CRC) code and wherein said CRC code further comprises 6 bits.

33. The method of claim 31 wherein said step of inserting a block synchronization scheme in said one 160 frame information block further comprises the step of inserting a bit having a value of `0` into the most significant bit position of frame 1 and inserting bits having alternating values of `1` and `0` into the most significant bit positions for the subsequent 39 frames, a bit having a value of `1` into the most significant bit position of frame 41 and inserting bits having alternating values of `0` and `1` into the most significant bit positions for the subsequent 39 frames, a bit having a value of `0` into the most significant bit position of frame 81 and inserting bits having alternating values of `1` and `0` into the most significant bit positions for the subsequent 39 frames, and a bit having a value of `1` into the most significant bit position of frame 121 and inserting bits having alternating values of `0` and `1` into the most significant bit positions for the subsequent 39 frames, wherein said inserted synchronization repeats every 80 frames and wherein said inserted synchronization repeats every 10 msec.

34. The method of claim 25 wherein said step of converting further comprises the step of receiving said at least one TDM timeslot.

35. The method of claim 34 wherein said at least one TDM timeslot further comprises one information block of 160 frames and wherein said step of converting further comprises the step of synchronizing to said one 160 frame information block.

36. The method of claim 35 wherein said step of converting further comprises the step of checking error control disposed in said one 160 frame information block for each of said multiplexed at least first 160 bit group and second 160 bit group.

37. The method of claim 36 wherein said step of converting further comprises the step of separating multiplexed first 160 bit group and second 160 bit group disposed in said 160 frame information block.

38. The method of claim 37 wherein said step of converting further comprises the step of coding each of said separated first 160 bit group and said second 160 bit group.

39. The method of claim 38 wherein said coded first 160 bit group further comprises a first 324 bit group and said coded second 160 bit group further comprises a second 324 bit group and wherein said step of converting further comprises the step of packing said first 324 bit group into a first information timeslot for radio transmission on a first radio carrier frequency and said second 324 bit group into a second information timeslot for radio transmission on a second radio carrier frequency.

40. A method which transfers messages from a land-line telephone system interface to at least one base-site in a digital radio time-division multiple access (TDMA) system comprising the steps of:

converting coded information of at least two information timeslots received from radio transmission on a radio carrier frequency into one information block for transmission in one TDM timeslot;

conveying at least said one TDM timeslot from a base-site to the land-line telephone system interface;

synchronizing to said one information block transmitted in at least said one TDM timeslot conveyed from a base-site; and

expanding said compressed information of said TDM timeslot of conveyed from a base-site.