Multiple antennas at transmitters and receivers to achieving higher diversity and data rates in MIMO systems

• US 20040202257A1
• Filed: 04/21/2004
• Published: 10/14/2004
• 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: Zhang, Jinyun, Molisch, Andreas F., Sudarshan, Pallav, Mehta, Neelesh B.
• Granted Patent: US 7,020,446 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04B 7/061 using feedback from receiving side
• CPC Class Codes: H04B 7/0667 of delayed versions of same signal using space-time coding H04L1/0618
• 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 7/0686 Hybrid systems, i.e. switching and simultaneous transmission
• 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 transmits an input stream of data symbols in a multiple-input, multiple-output wireless communications system. The input stream is demultiplexed into M substreams. Each of the M substreams is adaptively modulated and coded to a coded substream according to channel conditions. A first of the M coded substreams is space-time transmit diversity encoding into two space-time transmit diversity encoded substreams. There is one space-time transmit diversity encoded substream for each one of two transmit antennas. Each other coded substream is transmitted directly by a corresponding one of remaining M−1 transmit antenna.

Claims

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

demultiplexing the input stream into M substreams;

adaptively modulating and coding each of the M substreams to a coded substream;

space-time transmit diversity encoding a first of the M coded substreams into two space-time transmit diversity encoded substreams, one space-time transmit diversity encoded substream to be transmitted by a corresponding one of two transmit antenna; and

transmitting directly each other coded substream by a corresponding single transmit antenna.

2. The method of claim 1 further comprising:

feeding back, from a receiver, channel conditions of an associated channel for each transmit antenna.

selecting a maximum data rate and a modulation for each substream based on the channel conditions.

3. The method of claim 2, in which the channel conditions 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 modulating and coding, further comprises:

coding each substream;

interleaving each coded substream; and

symbol mapping each interleaved substream.

5. 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 ouput stream, after multiplication into a summed output stream corresponding to each output stream; and

multiplying each summed output stream by a scrambling code.

6. The method of claim 1, further comprising:

space-time transmit diversity encoding each of a subset of the M coded substreams into two space-time transmit diversity encoded substreams, one space-time transmit diversity encoded substream to be transmitted by a corresponding one of two transmit antenna; and

transmitting directly each other of the M coded substream not included in the subset by a corresponding single transmit antenna.

7. The method of claim 2, further comprising:

selecting the number M of substreams based on the channel condition.

8. An apparatus for transmitting an input stream of data symbols in a multiple-input/multiple-output wireless communications system, comprising:

M+1 transmit antennas;

a demultiplexer configured to demultiplex the input stream into M substreams;

M means for adaptively modulating and coding each of the M substreams to a coded substream;

means for space-time transmit diversity encoding a first of the M coded substreams into two space-time transmit diversity encoded substreams, one space-time transmit diversity encoded substream to be transmitted by a corresponding one of two transmit antenna; and

means for transmitting directly each other M−

1 coded substream by a corresponding single transmit antenna.