Space time transmit diversity with subgroup rate control and subgroup antenna selection in multi-input multi-output communications systems

• US 7,542,446 B2
• Filed: 04/21/2004
• Issued: 06/02/2009
• Est. Priority Date: 07/31/2002
• Status: Active Grant

• Current Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Electric Research Laboratories, Inc. (Mitsubishi Electric Corporation)
• Inventors: Sudarshan, Pallav, Mehta, Neelesh B., Zhang, Jinyun, Molisch, Andreas F.
• Primary Examiner(s): Kincaid; Lester
• Assistant Examiner(s): Lai; Daniel
• Application Number:
  US10/828,626
• Publication Number:
  US 20040196919A1
• Time in Patent Office: 1,868 Days
• Field of Search: 700/53, 375/299, 375/146, 375/267, 375/260, 455101-103, 455/63.4, 455504-506, 455/562.1, 370203-211, 343/700, 343/725
• US Class Current: 370/330
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0673 using feedback from receiving side
• CPC Class Codes: H04B 7/0691 using subgroups of transmit antennas
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• 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 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding

Abstract

A method and system transmits an input stream of data symbols in a multiple-input/multiple-output wireless communications system that includes M subgroups of transmitting antennas. A stream of data symbols is provided to a combined switch and demultiplexer. The combined switch and demultiplexer selects a subset L of the M subgroups of antennas as active, where L<M. The demultiplexer then splits the data stream into L substreams, which are fed to the L subgroups of antennas. Before transmission, each of the L substreams is adaptively modulated and coded to a maximum data rate while achieving a predetermined performance on an associated channel used to transmit the substream. Space-time transmit diversity encoding is applied to each coded substream to generate multiple output streams, one output stream for each antenna of each of the L subgroups. The selection by the switch is based on channel conditions fed back by a receiver of the output streams.

Claims

1. A method for transmitting an input stream of symbols in a multiple-input/multiple-output wireless communications system including M subgroups of transmitting antennas, comprising:

selecting, according to channel conditions of the multiple-input/multiple-output wireless communications system, L subgroups of the M subgroups of antennas, where L<

M and each of the L subgroups of antennas includes a set of at least two antennas;

demultiplexing, the input stream into L substreams, there being one substream for each one of the L selected subgroups of at least two antennas;

adaptively modulating and coding each of the L sub streams to a maximum data rate while achieving a predetermined performance on an associated channel used to transmit the substream;

space-time transmit diversity encoding each of the L coded substreams into a set of at least two output streams, there being one output stream for each antenna in the set of at least two antennas of each one of the L subgroups of antennas, wherein the selecting is performed before the adaptively modulating and coding and the space-time transmit diversity encoding; and

transmitting the set of at least two output streams using the L subgroups of at least two antennas.

2. The method of claim 1, further comprising:

feeding back, from a receiver, channel conditions; and

selecting a data rate according to the channel conditions.

3. The method of claim 2, in which the channel conditions used to select the data rate measure a signal to interference plus noise ratio of the output streams received in the receiver.

4. The method of claim 1, in which the adaptive modulation and coding depends on the number L of the substreams.

5. The method of claim 1, in which L is zero to increase an overall capacity of the system including a plurality of receivers.

6. The method of claim 1, in which the adaptive modulating and coding, further comprises:

coding each sub stream;

interleaving each coded substream; and

symbol mapping each interleaved substream.

7. The method of claim 1, further comprising:

demultiplexing each output stream into a plurality demultiplexed output streams;

multiplying each of the plurality of demultiplexed output streams by an orthogonal variable spreading factor;

adding the demultiplexed output streams, for each output stream, after multiplication into a summed output stream corresponding to each output stream; and

multiplying each summed output stream by a scrambling code.

8. The method of claim 7, wherein the orthogonal variable spreading factors are the same for all output streams.

9. The method of claim 7, wherein the scrambling codes are the same for all output streams.

10. The method of claim 1, wherein each input substream includes pairs of symbols X_i1 and X_i2, and wherein the space-time transmit diversity encoding encodes each pair of symbols as two pairs of symbols

$[\begin{array}{c}{X}_i\end{array}$

⁢

2 X i ⁢

⁢

1 - X i ⁢

⁢

1 * X i ⁢

⁢

2 * ] ,

where * is a complex conjugate.

11. The method of claim 10, wherein each pair of symbols X_i1 and X_i2 is transmitted by a first antenna of the set of at least two antennas while each pair of symbols −

X*_i2 and X*_i1 is transmitted by a second antenna of the set of at least two antennas.

12. The method of claim 1, further comprising:

performing the adaptively modulating and coding and the space-time transmit diversity encoding in parallel and independently for each substream.

13. The method of claim 1, wherein the number of selected antennas is at least 2L.

14. The method of claim 1, wherein performance reaches a maximal system capacities.

15. A system for transmitting an input stream of symbols in a multiple-input/multiple-output wireless communications system including M subgroups of transmitting antennas, comprising:

a switch configured to select, according to channel conditions of the multiple-input/multiple-output wireless communications system, L subgroups of the M subgroups of antennas, where L<

M and each of the L subgroups of antennas includes a set of at least two antennas;

a demultiplexer configured to split the input stream into L substreams, there being one substream for each one of the L subgroups of at least two antennas;

means for adaptively modulating and coding each of the L substreams to a maximum data rate while achieving a predetermine performance on an associated channel used to transmit the substream, wherein the switch selects before adaptively modulating and coding and space-time transmit diversity encoding; and

means for space-time transmit diversity encoding each of the L coded substream into a set of at least output streams, there being one output stream for each antenna in the set of at least two antennas of each one of the L subgroups of antennas.