Data transmission over a communications link with variable transmission rates

• US 6,307,867 B1
• Filed: 05/14/1998
• Issued: 10/23/2001
• Est. Priority Date: 05/14/1998
• Status: Expired due to Term

• Current Assignee: Lenovo Innovation Company Limited Hong Kong (Lenovo Group Ltd.)
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Johansson, Mathias, Roobol, Christiaan, Lundsjö, Johan, Beming, Per
• Primary Examiner(s): Patel, Ajit
• Assistant Examiner(s): Phunkulh, Bob A.
• Application Number:
  US09/078,598
• Time in Patent Office: 1,258 Days
• Field of Search: 370/328, 370/329, 370/335, 370/336, 370/337, 370/342, 370/345, 370/347, 370/465, 370/469, 370/470, 370/472, 375/222, 375/225
• US Class Current: 370/470
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04J 3/1647 Subrate or multislot multiplexing
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

An optimal data block size is determined for use in transmitting data at variable rates over a communications link in predetermined time intervals, where each predetermined time interval has the same time duration. Rather than varying data block size according to changes in transmission rates, which adds unnecessary complexity, the data blocks all have the same fixed size, i.e., the same number of data bits in each block. That fixed data block size is determined so that for all of the available data transmission rates, each predetermined time interval is fully occupied with useful information. The fixed data block size is determined based on a maximum frequency at which the transmission rate may change on the communications link and a lowest available transmission rate. Preferably, the fixed size of each data block is limited by predetermined maximum and minimum data block sizes in order to reduce the number of bit errors per data block, maintain a certain data throughput, and limit the amount of overhead bits relative to the number of payload bits for each data block.

Claims

1. A method of transmitting data at variable rates over a communications link in predetermined time intervals, where each of the predetermined time intervals has the same duration, comprising:

receiving data for transmission over the communications link;

detecting a first transmission rate for transmission over the communications link;

providing data bits at the first transmission rate into fixed size data blocks, each fixed size data block having the same number of bits;

transmitting over the communications link at the first transmission rate during one or more of the predetermined time intervals a first number of the fixed size data blocks corresponding to the first transmission rate;

detecting a change in transmission rate over the communications link from the first transmission rate to a second transmission rate;

providing data bits at the second transmission rate into the fixed size data blocks; and

transmitting a second number of the fixed size data blocks corresponding to the second transmission rate during one or more predetermined time intervals.

2. The method in claim 1, wherein the fixed size of each data block is determined so that the fixed size data blocks fully occupy each of the one or more predetermined time intervals for both the first and second transmission rates with useful information.

3. The method in claim 1, wherein the fixed size of each data block is determined based on a frequency at which the transmission rate may change and a minimal data transmission rate.

4. The method in claim 3, wherein the frequency corresponds to a maximum frequency at which the transmission rate may change and the minimal data transmission rate corresponds to the lowest rate available at which data may be transmitted.

5. The method in claim 3, wherein the fixed size of each of the fixed size data blocks must exceed a predefined minimum size.

6. The method in claim 3, wherein the maximum frequency at which the transmission rate may change is reduced when the data transmission rate is below a predefined rate.

7. The method in claim 1, wherein the transmission rate is prevented from changing during the predetermined time interval.

8. The method in claim 1, further comprising:

retransmitting at the second transmission rate one or more of the first number of data blocks during one of the predetermined time intervals,

wherein the retransmitted one or more of the first number of data blocks together with any one or more of the second number of data blocks fully occupy the one or more predetermined time intervals.

9. The method in claim 1, wherein the communications link employs a wire or optical cable for transmitting data.

10. The method in claim 1, wherein the communications link employs a wireless radio frequency resource for transmitting data.

11. A method of retransmitting data at variable rates at a first communications protocol layer in predetermined time intervals, where each of the predetermined time intervals has the same duration, comprising:

receiving a request for retransmission of a data message previously transmitted using a first transmission format specifying a first transmission rate;

segmenting at a second communications protocol layer above the first communications protocol layer the data message to be retransmit into fixed size protocol data units (PDUs), each fixed size PDU having the same number of bits independent of whether the PDU has the first or a second transmission format; and

transmitting the fixed size PDUs via the first communications protocol layer using a second transmission format specifying a second transmission rate different from the first transmission rate at which the data message was originally transmitted during one or more of the predetermined time intervals.

12. The method in claim 11, wherein different transmission formats include different coding schemes, interleaving lengths, or repetition schemes.

13. The method in claim 11, wherein each PDU includes a header having a sequence number, at least a portion of the data message, and an error detection field.

14. The method in claim 11, wherein the fixed size of each PDU is selected so that the PDUs integrally occupy the predetermined time interval despite differences in transmission formats.

15. The method in claim 14, wherein the PDUs occupy the predetermined time interval without having to add filler data bits to complete the predetermined time interval.

16. The method in claim 11, wherein the fixed PDU size is determined based on a frequency at which the transmission rate may change and a minimal data transmission rate.

17. The method in claim 16, wherein the frequency corresponds to a maximum frequency at which the transmission rate may change and the minimal data transmission rate corresponds to the lowest rate available at which data may be transmitted.

18. The method in claim 17, wherein the maximum frequency at which the transmission rate may change is reduced when the data transmission rate is below a predefined rate.

19. The method in claim 11, wherein the transmission rate is prevented from changing during the predetermined time interval.

20. A communications device comprising:

a buffer configured to store data for transmission over a communications link;

data processing circuitry configured to detect a first transmission rate associated with data to be transmitted over the communications link, and provide data bits at the first transmission rate into fixed size data blocks, each fixed size data block having the same number of bits; and

a transmitter configured to transmit over the communications link at the first transmission rate during one or more of the predetermined time intervals, each time interval having the same duration, a first number of the fixed size data blocks per time interval corresponding to the first transmission rate;

wherein the data processing circuitry is configured to detect a change in transmission rate over the communications link from the first transmission rate to a second transmission rate, provide data bits at the second transmission rate into the fixed size data blocks, and transmit a second number of the fixed size data blocks per time interval corresponding to the second transmission rate during one or more of the predetermined time intervals.

21. The communications device in claim 20, wherein the fixed size of each data block is determined so that the fixed size data blocks fully occupy the one or more predetermined time intervals with useful information for both the first and second transmission rates.

22. The communications device in claim 20, wherein the fixed size of each data block is determined based on a frequency at which the transmission rate may change and a minimal data transmission rate.

23. The communications device in claim 22, wherein the frequency corresponds to a maximum frequency at which the transmission rate may change and the minimal data transmission rate corresponds to the lowest rate available at which data may be transmitted.

24. The communications device in claim 22, wherein the fixed size of each of the fixed size data blocks must exceed a predefined minimum size.

25. The communications device in claim 24, wherein the maximum frequency at which the transmission rate may change is reduced when the data transmission rate is below a predefined rate.

26. The communications device in claim 20, wherein the transmission rate is prevented from changing during the predetermined time interval.

27. The communications device in claim 20, wherein the transmitter is configured to retransmit at the second transmission rate one or more of the first number of data blocks during one of the predetermined time intervals, and

wherein the retransmitted one or more of the first number of data blocks together with any one or more of the second number of data blocks fully occupy the one or more predetermined time intervals.

28. The communications device in claim 20, wherein the communications link includes a wire or an optical cable for transmitting data.

29. The communications device in claim 20, wherein the communications link includes a wireless radio frequency resource for transmitting data.

30. The communications device in claim 20, wherein the communications device is a mobile radiotelephone.

31. The communications device in claim 20, wherein the communications device is a radio base station.

32. A communications protocol for data communications over a communications link between a mobile station and a base station, comprising:

a first communications protocol layer for transmitting data over the communications link at variable rates in predetermined time intervals, where each of the predetermined time intervals has the same duration, and

a second communications protocol layer for;

(a) receiving a request to retransmit a data message previously transmitted using a first transmission format specifying a first transmission rate, and

(b) segmenting the data message into fixed size protocol data units (PDUs),

each fixed size PDU having the same number of bits,

wherein the fixed size PDUs may be transmit at a second transmission rate different from the first transmission rate at which the data message was originally transmit during one or more of the predetermined time intervals via the first communications protocol layer.

33. The communications protocol of claim 32 as applied to a code division multiple access (CDMA) mobile communications system, wherein the first communications protocol layer employs a spreading code in transmitting the PDUs over a radio communications link and the second communications protocol layer corresponds to a radio link control access control (RLC) protocol layer.