Method and apparatus for providing variable rate data in a communications system using statistical multiplexing

• US 6,005,855 A
• Filed: 10/24/1997
• Issued: 12/21/1999
• Est. Priority Date: 04/28/1995
• Status: Expired due to Term

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Schiff, Leonard N., Zehavi, Ephraim, Wolf, Jack K.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): RAO, SEEMA SRINIVAS
• Application Number:
  US08/957,486
• Time in Patent Office: 788 Days
• Field of Search: 370/320, 370/335, 370/342, 370/441, 370/468, 370/206, 375/200, 375/206, 714/746, 714/748
• US Class Current: 370/335
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 3/247 ATM or packet multiplexing
• CPC Class Codes: H04L 1/0014 by adapting the source coding
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04W 72/52 based on load

Abstract

A variable rate transmission system wherein a packet of variable rate data generated by a variable rate data source is modulated on traffic channel by traffic channel modulator if the capacity of the traffic channel is capable of transmitting the packet. And where the packet of variable rate data is modulated onto traffic channel by traffic channel modulator and at least one overflow channel by traffic channel modulator, if the capacity of the traffic channel is less than required to transmit the packet. A receiving system for receiving variable rate data transmitted in accordance with the above.

Claims

1. An apparatus for transmitting a variable rate packet of data symbols comprising a variable number of said data symbols, said apparatus comprising:

channel packetizer means for receiving said variable rate packet and when the number of said data symbols exceeds a threshold value, splitting said variable rate packet into a traffic packet and at least one overflow packet;

transmission means for transmitting said variable rate packet on a traffic channel when in number of said data symbols is below said threshold value and for transmitting said traffic packet on said traffic channel and said at least one overflow packet on at least one overflow channel when the number of said data symbols exceeds said threshold value, wherein each of said at least one overflow channel is orthogonal to said traffic channel and wherein said at least one overflow channel is selected based on a statistical multiplexing of said at least one overflow channel.

2. The apparatus of claim 1 wherein said transmission means comprises:

modulator means for modulating said variable rate packet to provide said variable rate packet on said traffic channel in accordance with a first spread spectrum modulation format when the number of said data symbols is below said threshold value and for modulating said traffic packet to provide said traffic packet on said traffic channel in accordance with said first spread spectrum modulation format and for modulating said at least one overflow packet in accordance with a second spread spectrum modulation format to provide said at least one overflow packet on said at least one overflow channel when the number of said data symbols exceeds said threshold value wherein said first spread spectrum modulation format is orthogonal to said second spread spectrum modulation format; and

RF means for upconverting and amplifying said variable rate packet when the number of said data symbols is below said threshold value and for upconverting and amplifying said traffic packet and said at least one overflow packet when the number of said data symbols exceeds said threshold value.

3. The apparatus of claim 1 further comprising overflow channel signaling means for transmitting a signal identifying said at least one overflow channel.

4. The apparatus of claim 1 wherein said channel packetizer means includes means for receiving a signal indicative of said at least one overflow channel and for combining said signal indicative of said at least one overflow channel and said traffic packet.

5. The apparatus of claim 1 wherein said channel packetizer means includes means for receiving a signal indicative of said at least one overflow channel for a subsequent variable rate packet and for combining a signal indicative of said at least one overflow channel for a subsequent variable rate packet and said traffic packet.

6. The apparatus of claim 1 further comprising variable rate vocoder means for receiving speech samples and for compressing said speech samples in accordance with a variable rate vocoder format to provide said variable rate packet.

7. The apparatus of claim 6 further comprising encoder means for error correction coding said variable rate packet disposed between said channel packetizer means and said transmission means.

8. The apparatus of claim 7 further comprising interleaver means for reordering said variable rate packet disposed between said encoder means and said transmission means.

9. The apparatus of claim 6 wherein said variable rate vocoder means is further for compressing said speech samples in accordance with a second variable rate vocoder format to provide an alternative variable rate packet and wherein said channel packetizer means is further for selecting a variable rate packet for transmission from said variable rate packet and said alternative variable rate packet.

10. The apparatus of claim 1 further comprising cell controller means for providing an overflow channel availability signal and where said channel packetizer means is responsive to said traffic channel availability signal.

11. A method for transmitting a variable rate packet of data symbols comprising a variable number of said data symbols, said method comprising the steps of:

receiving said variable rate packet;

splitting said variable rate packet into a traffic packet and at least one overflow packet, when the number of said data symbols exceeds a threshold value;

transmitting said variable rate packet on a traffic channel when number of said data symbols is below said threshold value; and

transmitting said traffic packet on said traffic channel and said at least one overflow packet on at least one overflow channel when the number of said data symbols exceeds said threshold value, wherein each of said at least one overflow channel is orthogonal to said traffic channel and wherein said at least one overflow channel is selected based on a statistical multiplexing of said at least one overflow channel.

12. The method of claim 11 wherein said step of transmitting said traffic packet on said traffic channel and said at least one overflow packet on at least one overflow channel comprises the steps of:

modulating said traffic packet to provide said traffic packet on said traffic channel in accordance with said first spread spectrum modulation format;

modulating said at least one overflow packet in accordance with a second spread spectrum modulation format to provide said at least one overflow packet on said at least one overflow channel wherein said first spread spectrum modulation format is orthogonal to said second spread spectrum modulation format;

upconverting said traffic packet and said at least one overflow packet when the number of said data symbols exceeds said threshold value; and

amplifying said traffic packet and said at least one overflow packet when the number of said data symbols exceeds said threshold value.

13. The method of claim 11 further transmitting a signal identifying of said at least overflow channel.

14. The method of claim 11 further comprising combining said signal indicative of said at least overflow channel with said traffic packet.

15. The method of claim 11 further comprising the step of combining a signal indicative of said at least overflow channel for a subsequent variable rate packet and said traffic packet.

16. The method of claim 11 further comprising the steps of:

receiving speech samples; and

compressing said speech samples in accordance with a variable rate vocoder format to provide said variable rate packet.

17. The method of claim 16 further comprising the step of error correction coding said variable rate packet.

18. The method of claim 17 further comprising the step of reordering said variable rate packet.

19. The method of claim 16 wherein said step of compressing said speech samples further comprises compressing said speech samples in accordance with a second variable rate vocoder format to provide an alternative variable rate packet.

20. The method of claim 11 further comprising the step of providing an overflow channel availability signal.

21. A system for transmitting a variable rate packet of data symbols comprising:

an interleaver having an input and having a first output for outputting said variable rate packet when the number of said data symbols in said variable rate packet is less than a threshold and for outputting a first portion of said variable rate packet when the number of said data symbols in said packet is greater than said threshold and having a second output for outputting a second portion of said variable rate packet when the number of said data symbols in said variable rate packet is greater than said threshold;

a first modulator having an input coupled to said first interleaver output and having an output; and

a second modulator having an input coupled to said second interleaver output and having an output wherein said output of said second modulator is dependent on an availability of at least one overflow channel.

22. The system of claims 21 further comprising a variable data source having an input and having an output coupled to the interleaver.

23. The system of claim 22 further comprising a selector disposed between said variable rate data source and said interleaver having an input coupled to said variable rate data source output and having an output coupled to said interleaver input.

24. The system of claim 23 wherein said selector having a second input and said system further comprises a cell controller has an output coupled to said second selector input.

25. Apparatus for receiving a variable rate packet of data symbols in a communication system in which one or more base stations communicate with one or more mobile stations using spread spectrum communication signals in which variable rate data is placed on one of a plurality of orthogonal code channels which are also spread using at least one PN code and transferred from one station to another using a selected traffic code channel and one or more corresponding orthogonal overflow code channels within a spread communication signal, comprising:

a traffic channel demodulator connected to receive and demodulate communication signals to produce demodulated traffic packets in accordance with a selected traffic channel code and modulation format to provide a demodulated traffic packet;

at least one overflow demodulator connected to receive and demodulate communication signals to produce one or more demodulated overflow packets in accordance with selected overflow channel codes and modulation formats to provide at least one demodulated overflow packet which corresponds to said demodulated traffic packet; and

at least one combiner coupled to said traffic and overflow demodulators for receiving and combining said demodulated traffic and overflow packets to produce a single variable rate packet in accordance with said statistical multiplexing of data packets onto overflow channels.

26. The apparatus of claim 25 further comprising decoder disposed between said traffic demodulator and said combiner for selecting a demodulated overflow packet of said at lest one demodulated overflow packet.

27. The apparatus of claim 26 wherein said decoder combines said demodulated traffic packet and each of said at least one demodulated overflow packet and decodes each combination to determine a selected overflow packet.

28. The apparatus of claim 27 wherein said decoder decodes said traffic packet to determine an overflow channel identification signal and wherein said at least one overflow demodulator is responsive to said overflow channel identification signal for selecting at least one overflow channel packet.

29. System for transferring variable rate data symbols in a communication system in which one or more base stations communicate with one or more mobile stations using direct sequence spread spectrum communication signals in which variable rate data is placed on one of a plurality of orthogonal code channels which are also spread using at least one PN code and transferred using a traffic code channel and one or more corresponding orthogonal overflow code channels within a FDM communication signal, comprising:

means for receiving variable rate data packets and dividing them into traffic and overflow channel packets when a number of data symbols in the variable rate packet exceeds a preselected amount;

transmission means for transmitting said variable rate packets on a traffic channel except when divided into traffic and overflow packets, and then for transmitting said traffic and overflow packets on a traffic and at least one corresponding overflow channel, respectively, selected based on statistical multiplexing of data packets, with said channels being orthogonal to each other according to preselected orthogonal codes used to modulate said channel data;

receiver means for receiving traffic and overflow channel signals;

a traffic channel demodulator connected to receive and demodulate channel signals to produce demodulated traffic packets in accordance with a selected traffic channel code and modulation format to provide a demodulated traffic packet;

at least one overflow demodulator connected to receive and demodulate channel signals to produce one or more demodulated overflow packets in accordance with selected overflow channel codes and modulation formats to provide at least one demodulated overflow packet which corresponds to said demodulated traffic packet; and

at least one combiner coupled to said traffic and overflow demodulators for receiving and combining said demodulated traffic and overflow packets to produce a single variable rate packet in accordance with said statistical multiplexing of data packets onto overflow channels.