Framing for an adaptive modulation communication system

• US 7,379,441 B2
• Filed: 02/13/2007
• Issued: 05/27/2008
• Est. Priority Date: 11/15/2000
• Status: Expired due to Fees

• Current Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Original Assignee: Quarterhill Inc. (f/k/a Wi-LAN Inc.)
• Inventors: Klein, Israel Jay, Chen, An, Stanwood, Kenneth L., Lin, George
• Primary Examiner(s): To; Doris H.
• Assistant Examiner(s): GREY, CHRISTOPHER P
• Application Number:
  US11/674,548
• Publication Number:
  US 20070133481A1
• Time in Patent Office: 469 Days
• Field of Search: None
• US Class Current: 370/337
• CPC Class Codes: H04B 7/15557 Selecting relay station operation mode, e.g. between amplify and forward mode, decode and forward mode or FDD - and TDD mode
• CPC Class Codes: H04B 7/212 Time-division multiple access [TDMA]
• CPC Class Codes: H04B 7/2615 using hybrid frequency-time division multiple access [FDMA-TDMA]
• CPC Class Codes: H04B 7/2656 for structure of frame, burst
• CPC Class Codes: H04B 7/2681 Synchronisation of a mobile station with one base station
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission
• CPC Class Codes: H04W 56/0085 detecting a given structure in the signal
• CPC Class Codes: H04W 72/23 in the downlink direction of a wireless link, i.e. towards a terminal

Abstract

A system and method for mapping a combined frequency division duplexing (FDD) Time Division Multiplexing (TDM)/Time Division Multiple Access (TDMA) downlink subframe for use with half-duplex and full-duplex terminals in a communication system. Embodiments of the downlink subframe vary Forward Error Correction (FEC) types for a given modulation scheme as well as support the implementation of a smart antennae at a base station in the communication system. Embodiments of the system are also used in a TDD communication system to support the implementation of smart antennae. A scheduling algorithm allows TDM and TDMA portions of a downlink to efficiently co-exist in the same downlink subframe and simultaneously support full and half-duplex terminals. The algorithm further allows the TDM of multiple terminals in a TDMA burst to minimize the number of map entries in a downlink map. The algorithm limits the number of downlink map entries to not exceed 2n+1, where n is the number of DL PHY modes (modulation/FEC combinations) employed by the communication system.

Claims

1. A method for conveying data in a downlink over a communication link, the method comprising:

providing a downlink subframe with a time division multiplex (TDM) portion, including at least one TDM section, and a Time Division Multiple Access (TDMA) portion, including at least one TDMA section with an associated preamble;

beginning the downlink subframe with a broadcast preamble;

establishing a downlink map for the downlink subframe, the downlink map indicating one or more time positions within the downlink subframe where the at least one TDM section begins, and indicating one or more time positions within the downlink subframe where the at least one TDMA section begins;

transmitting the downlink map in the downlink subframe after the broadcast preamble; and

transmitting all TDM sections and all TDMA sections, along with each associated preamble, within the downlink subframe after transmitting the downlink map.

2. The method of claim 1, further comprising:

transmitting the TDMA portion after at least one TDM section.

3. The method of claim 2, further comprising:

dividing the TDM portion according to physical parameters of data recipients, including differences in the combination of modulation type and forward error correction (FEC) types used by the data recipients.

4. A method for scheduling a communication system which includes a plurality of terminals and a base station, both configured to communicate using adaptive modulations in a downlink subframe and an uplink subframe, with each of the plurality of terminals having an associated preferred downlink modulation/forward error correction (PHY) mode, D₁, D₂, . . . D_N, wherein D₁ is a most robust modulation and D_N is a least robust modulation, and wherein each of the plurality of terminals and their associated preferred downlink PHY mode have an associated uplink PHY mode, U₁, U₂, U_N, and wherein U₁ is associated with the plurality of terminals that have the preferred downlink PHY mode D₁, and wherein U_N is associated with the plurality of terminals that have the preferred downlink PHY mode D_N, such that a number of downlink map entries does not exceed 2N+1, the method comprising:

grouping the plurality of terminals based on preferred downlink PHY modes;

allocating uplink bandwidth in an uplink subframe such that the plurality of terminals are put in order of their preferred downlink PHY modes, from a second most robust preferred downlink PHY mode and continuing in order of decreasing robustness followed by a most robust preferred downlink PHY mode last;

allocating the plurality of terminals that use a D₁ PHY mode to begin at a start of a downlink subframe;

if a time duration of the D₁ PHY mode is less than a time duration of a U₂ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use a D₂ PHY mode, beginning at a time that the U₂ PHY mode ends;

if the time duration of the D₁ PHY mode is greater than or equal to the time duration of the U₂ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D₂ PHY mode, beginning at an end of the D₁ PHY mode;

if a time duration of the D₂ PHY mode is less than a time duration of a U₃ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use a D₃ PHY mode, beginning at a time that the U₃ PHY mode ends;

if the time duration of the D₂ PHY mode is greater than or equal to the time duration of the U₃ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D₃ PHY mode, beginning at an end of the D₂ PHY mode;

if the time duration of the D₃ PHY mode is greater than the sum of a time duration of a U₄ PHY mode, a U₅ PHY mode, and a U₁ PHY mode, segmenting the plurality of terminals that use the D₃ PHY mode and inserting the segments into any gaps in the downlink subframe;

if a time duration of the D₃ PHY mode is less than a time duration of the U₄ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use a D₄ PHY mode, beginning at a time that the U₄ PHY mode ends;

if the time duration of the D₃ PHY mode is greater than or equal to the time duration of the U₄ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D₄ PHY mode, beginning at an end of the D₃ PHY mode;

if a time duration of the D₄ PHY mode is less than a time duration of the U₅ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use a D₅ PHY mode, beginning at a time that the U₅ PHY mode ends;

if the time duration of the D₄ PHY mode is greater than or equal to the time duration of the U₅ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D₅ PHY mode, beginning at an end of the D₄ PHY mode;

if the time duration of the plurality of terminals that use the D₅ PHY mode is longer in duration than a combined time duration of the U₁ PHY mode and gaps that are not aligned with the U₅ PHY mode, rearranging allocated downlink bandwidth of the downlink subframe to accommodate a remainder of the D₅ PHY mode such that the remainder is not aligned with the U₅ PHY mode; and

if the time duration of the plurality of terminals that use the D₅ PHY mode is shorter in duration than the combined time duration of the U₁ PHY mode and the gaps that are not aligned with the U₅ PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D₅ PHY mode beginning at the end of the D₄ PHY mode and also interleaved in the gaps in the downlink subframe.

5. A method for scheduling a communication system which includes a plurality of terminals and a base station, both configured to communicate using adaptive modulations in a downlink subframe and an uplink subframe, with each of the plurality of terminals having an associated preferred downlink modulation/forward error correction (PHY) mode, D₁, D₂, . . . D_N, wherein D₁ is a most robust modulation and D_N is a least robust modulation, and wherein each of the plurality of terminals and their associated preferred downlink PHY mode have an associated uplink PHY mode, U₁, U₂, U_N, and wherein U₁ is associated with the plurality of terminals that have the preferred downlink PHY mode D₁, and wherein U_N is associated with the plurality of terminals that have the preferred downlink PHY mode D_N, such that a number of downlink map entries does not exceed 2N+1, the method comprising:

grouping the plurality of terminals based on preferred downlink PHY modes;

allocating uplink bandwidth in an uplink subframe such that the plurality of terminals are put in order of their preferred downlink PHY modes, from a second most robust preferred downlink PHY mode and continuing in order of decreasing robustness with a most robust preferred downlink PHY mode last;

allocating the plurality of terminals that use a D₁ PHY mode to begin at a start of a downlink subframe;

if a time duration for the plurality of terminals that have a D_N PHY mode is less than a time duration for the plurality of terminals that are assigned to a U_N+1 PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D_N PHY mode, beginning at a time that a U_N PHY mode ends;

if the time duration for the plurality of terminals that have the D_N PHY mode is greater than or equal to the time duration for the plurality of terminals that are assigned to the U_N+1 PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D_N PHY mode, beginning at an end of a D<sub>N−

1</sub> PHY mode;

if the time duration of the plurality of terminals that have the D_N PHY mode is longer in duration than a combined time duration of a U₁ PHY mode and gaps that are not aligned with the U_N PHY mode, rearranging downlink bandwidth of the downlink subframe to accommodate a remainder of the D_N PHY mode such that the remainder is not aligned with the U_N PHY mode; and

if the time duration of the plurality of terminals that have the D_N PHY mode is shorter in duration than the combined time duration of the U₁ PHY mode and the gaps that are not aligned with the U_N PHY mode, allocating bandwidth of the downlink subframe to the plurality of terminals that use the D_N PHY mode, beginning at the end of the D<sub>N−

1</sub> PHY mode and also interleaved in the gaps in the downlink subframe.

6. A method for scheduling physical slots within a downlink subframe for a first receiver and a second receiver, each receiver assigned to a operate with a level of robustness, the receivers receiving data from a single transmitter in an adaptive modulation communication system, the method comprising:

providing data for a first receiver which have been assigned a level of robustness including a combination of modulation and forward error correction (FEC) types in a time division multiplex (TDM) section of the downlink subframe having a combination of modulation and FEC at least as robust as the level assigned to the first receiver; and

providing data for a second receiver in a Time Division Multiple Access (TDMA) section of the downlink subframe which provides a combination of modulation and FEC which is at least as robust as a level assigned to the second receiver.

7. The method of claim 6, wherein the TDM section is provided before providing the TDMA section.

8. The method of claim 7, wherein the first receiver operates in a full-duplex fashion and the second receiver operates in a half-duplex fashion.

9. The method of claim 7, wherein the first receiver and the second receiver operate in a full-duplex fashion.

10. The method of claim 7, wherein the first receiver and the second receiver operate in a half-duplex fashion.

11. The method of claim 6, further comprising providing data to a single transmitter from the first and second receivers during an uplink subframe.

12. The method of claim 11, wherein the downlink subframe is transmitted on a first channel and the uplink subframe is transmitted on a second channel.

13. The method of claim 11, wherein the downlink subframe and the uplink subframe are transmitted on the same channel.