Transmission method for OFDM-MIMO communication system

• US 20060067417A1
• Filed: 09/26/2005
• Published: 03/30/2006
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Original Assignee: Samsung Electronics Co. Ltd., Seoul National University Industry Foundation (Seoul National University)
• Inventors: Nam, Seung-Hoon, Park, Chang-Soon, Lee, Kwang-Bok, Jung, Koo-Chul
• Granted Patent: US 7,623,588 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 7/0626 Channel coefficients, e.g. channel state information [CSI]
• CPC Class Codes: H04B 7/066 Combined feedback for a number of channels, e.g. over several subcarriers like in orthogonal frequency division multiplexing [OFDM]
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 1/0675 characterised by the signaling
• CPC Class Codes: H04L 25/0204 of multiple channels
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A data transmission method in a MIMO-OFDM communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas. The method includes selecting a spatial subchannel in which when bits are added by applying at least two spatial modes having different multiplexing gains for an individual subcarrier in a frequency domain, the minimum power increment is required during application of each spatial mode; allocating a spatial mode that requires the minimum total accumulated power, for each subcarrier; and selecting all subcarriers in the order of a subcarrier that requires the minimum power increment.

Claims

1. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

selecting a spatial subchannel in which when bits are added by applying at least two spatial modes having different multiplexing gains for an individual subcarrier in a frequency domain, a minimum power increment is required during application of each spatial mode;

allocating a spatial mode that requires the minimum total accumulated power, for each subcarrier; and

selecting all subcarriers in the order of a subcarrier that requires the minimum power increment.

2. The data transmission method of claim 1, wherein the accumulated power is determined by multiplying power of the spatial subchannel that requires the minimum power increment by the number of spatial subchannels in a corresponding spatial mode.

3. The data transmission method of claim 1, wherein the multiplexing gain is defined as the number of independent data streams transmitted for one symbol duration.

4. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

grouping consecutive subcarriers in a frequency domain into a predetermined number of subcarrier groups;

selecting a representative subcarrier from each subcarrier group;

selecting a spatial mode having the highest throughput for each of the selected subcarriers; and

allocating the selected spatial mode to all subcarriers in the corresponding subcarrier group.

5. The data transmission method of claim 4, further comprising the step of reducing the number of subcarriers of the subcarrier group if a multiplexing gain between different spatial modes allocated to adjacent subcarrier groups is greater than a predetermined threshold.

6. The data transmission method of claim 5, wherein the multiplexing gain is defined as the number of independent data streams transmitted for one symbol duration.

7. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

selecting a predetermined number of subcarriers in a frequency domain;

calculating a signal-to-noise ratio (SNR) for each subcarrier-spatial mode by applying at least two spatial modes having different multiplexing gains for the selected subcarriers;

determining a data rate corresponding to an SNR of each subcarrier-spatial mode using a mapping table;

calculating a sum of data rates for the subcarriers when the same spatial modes are applied;

selecting a spatial mode having a maximum data rate sum by comparing data rate sums between spatial modes; and

allocating the selected spatial mode to all subcarriers.

8. The data transmission method of claim 7, wherein the multiplexing gain is defined as the number of independent data streams transmitted for one symbol duration.

9. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

calculating data rates for all subcarriers when the subcarriers are applied to two spatial modes having different multiplexing gains;

calculating an average data rate of a first spatial mode having a lesser multiplexing gain of the two spatial modes;

determining whether the average data rate of the first spatial mode is lower than a saturated data rate;

allocating the first spatial mode for all subcarriers if the average data rate of the first spatial mode is lower than a saturated data rate; and

allocating a second spatial mode being greater than the first spatial mode in multiplexing gain, for all of the subcarriers if the average data rate of the first spatial mode is greater than or equal to the saturated data rate.

10. The data transmission method of claim 9, further comprising the steps of:

calculating an average data rate of the second spatial mode;

determining whether the average data rate of the second spatial mode is less than or equal to a predetermined compensated data rate; and

allocating the first spatial mode for the subcarriers where the average data rate of the second spatial mode is less than or equal to the predetermined compensated data rate.

11. The data transmission method of claim 9, wherein a multiplexing gain of the first spatial mode is 2 and a multiplexing gain of the second spatial mode is 4.

12. The data transmission method of claim 9, wherein the multiplexing gain is defined as the number of independent data streams transmitted for one symbol duration.

13. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

selecting a predetermined number of subcarriers in a frequency domain;

calculating total throughput for the selected subcarriers when a spatial mode with a multiplexing gain of 1 and a spatial mode with a multiplexing gain of 2 are applied;

determining whether a first condition that the spatial mode with the multiplexing gain of 2 is greater than or equal to the spatial mode with the multiplexing gain of 1 in terms of the total throughput is satisfied;

allocating the spatial mode with the multiplexing gain of 1 for all subcarriers if the first condition is not satisfied;

if the first condition is satisfied, determining whether a second condition that an average data rate of the spatial mode with the multiplexing gain of 2 is greater than or equal to a saturated data rate is satisfied;

allocating the spatial mode with the multiplexing gain of 2 for all subcarriers if the second condition is not satisfied; and

allocating a spatial mode with a multiplexing gain of 4 for all subcarriers if the second condition is satisfied.

14. The data transmission method of claim 13, further comprising the steps of:

calculating an average data rate for the subcarriers allocated the spatial mode with the multiplexing gain of 4 when the spatial mode with the multiplexing gain of 4 is applied;

determining whether a third condition that the average data rate of the spatial mode with the multiplexing gain of 4 is less than or equal to a predetermined compensated data rate is satisfied; and

allocating the spatial mode with the multiplexing gain of 2 for the subcarriers where the third condition is satisfied.

15. The data transmission method of claim 13, wherein the multiplexing gain is defined as the number of independent data streams transmitted for one symbol duration.

16. A data transmission method in a MIMO-OFDM (Multiple Input Multiple Output-based Orthogonal Frequency Division Multiplexing) communication system including at least one receiver for receiving a signal through a plurality of reception antennas and a transmitter for selecting a transmission channel using channel information being fed back from the receiver and transmitting a signal through a plurality of transmission antennas, the method comprising the steps of:

receiving a signal that was transmitted by uniformly allocating transmission power and a number of initial bits to each subchannel;

grouping subchannels according to a signal-to-noise ratio (SNR) of the received signal;

calculating minimum powers required for transmission of the number of initial bits allocated to each subchannel;

calculating the total available power by summing up extra powers except the minimum powers; and

allocating power and a number of bits to each subchannel group using a quantized power set table predetermined through calculation for each group.