Adaptive time diversity and spatial diversity for OFDM

• US 20060104196A1
• Filed: 12/22/2005
• Published: 05/18/2006
• Est. Priority Date: 09/01/2000
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Nortel Networks Limited (Nortel Networks Corporation)
• Inventors: Strawczynski, Leo, Tong, Wen, Wu, Shiquan
• Granted Patent: US 7,336,601 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/063 Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/068 using space frequency diversity space-frequency coding H04L1/0606
• CPC Class Codes: H04B 7/0689 using different transmission schemes, at least one of them being a diversity transmission scheme
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0891 Space-time diversity rake receivers H04B1/7115; space-time decoding H04L1/0631
• CPC Class Codes: H04L 1/0001 Systems modifying transmission characteristics according to link quality, e.g. power backoff adaptive data allocation for multicarrier modulation H04L5/0044; controlling transmission power for radio systems H04W52/04
• 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 1/0025 Transmission of mode-switching indication
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0625 Transmitter arrangements
• CPC Class Codes: H04L 1/0631 Receiver arrangements
• CPC Class Codes: H04L 1/0662 Limited orthogonality systems
• CPC Class Codes: H04L 1/0675 characterised by the signaling
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2604 Multiresolution systems by means of multiresolution subcarriers H04L27/183, H04L27/3488
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/2646 using feedback from receiver for adjusting OFDM transmission parameters, e.g. transmission timing or guard interval length
• CPC Class Codes: H04L 27/2647 : Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 5/0007 : the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 : Time-frequency-space
• CPC Class Codes: H04L 5/0025 : Spatial division following the spatial signature of the channel
• CPC Class Codes: H04L 5/0026 : Division using four or more dimensions
• CPC Class Codes: H04L 5/0046 : Determination of how many bits are transmitted on different sub-channels
• CPC Class Codes: H04L 5/006 : Quality of the received signal, e.g. BER, SNR, water filling

Abstract

An adaptable orthogonal frequency-division multiplexing system (OFDM) that uses a multiple input multiple output (MIMO) to having OFDM signals transmitted either in accordance with time diversity to reducing signal fading or in accordance with spatial diversity to increase the data rate. Sub-carriers are classified for spatial diversity transmission or for time diversity transmission based on the result of a comparison between threshold values and at least one of three criteria. The criteria includes a calculation of a smallest eigen value of a frequency channel response matrix and a smallest element of a diagonal of the matrix and a ratio of the largest and smallest eigen values of the matrix.

Claims

1. A method of transmitting data, comprising:

loading a first data on a sub-carrier of an orthogonal frequency division multiplexing (OFDM) symbol associated with an antenna;

loading a second data on a sub-carrier of another OFDM symbol associated with the antenna;

loading said first and said second data on sub-carriers of OFDM symbols associated with an another antenna according to at least one mapping rule, wherein said at least one mapping rule is a conjugate mapping rule; and

transmitting said first data with the antenna.

2. The method of claim 1, further comprising:

transmitting said second data with the antenna; and

transmitting said first and said second data with said another antenna.

3. The method of claim 2, wherein

said transmission of said first data with said another antenna is transmitted subsequent to said transmission of said first data with said antenna;

and

said transmission of said second data with said antenna is transmitted subsequent to said transmission of said second data with said another antenna.

4. The method of claim 1, wherein said loading step further comprises:

loading said first data on said sub-carrier of said OFDM symbols associated with said another antenna according to said conjugate mapping rule; and

loading said second data on said sub-carrier of said OFDM symbol associated with said another antenna according to a negative conjugate mapping rule.

5. The method of claim 3, wherein

a rate of transmission of said first data with said antenna is substantially equal to a rate of transmission of said first data with said another antenna;

and

a rate of transmission of said second data with said antenna is substantially equal to a rate of transmission of said second data with said another antenna.

6. A method for use with an adaptive orthogonal frequency division-multiplexing (OFDM) system that uses multiple input multiple output (MIMO) structure to transmit OFDM signals from a plurality of transmitter antennas to a plurality of receiver antennas, at least one of the OFDM signals having a frame of duration, the OFDM frame having data packets and a plurality of OFDM slots, each of the OFDM slots having a plurality of OFDM symbols that include a plurality of sub-carriers, the method comprising:

loading a first data onto a sub-carrier of a first OFDM symbol corresponding to a first transmitter antenna;

transmitting said first data within a duration of said first OFDM symbol; and

transmitting said first data within a duration of a second OFDM symbol corresponding to a second transmitter antenna according to a conjugate mapping rule.

7. The method of claim 6, further comprising

loading a second data onto said sub-carrier of said second OFDM symbol, said second OFDM symbol corresponding to said first transmitter antenna;

transmitting said second data within the duration of said second OFDM symbol corresponding to said first transmitter antenna;

transmitting said second data within the duration of said first OFDM symbol corresponding to said second transmitter antenna according to an another conjugate mapping rule.

8. The method of claim 7, wherein said transmission of said first data according to said conjugate mapping rule is transmitted subsequent to said transmission of said first data;

and

said transmission of said second data according to said another conjugate mapping rule is transmitted prior to said transmission of said second data.

9. The method of claim 7, wherein said another conjugate mapping rule is a negative conjugate mapping rule.

10. The method of claim 7, wherein

a rate of transmission of data corresponding to said first transmitter antenna is equal to a rate of transmission of data corresponding to said second transmitter antenna;

a rate of transmission of said first data within the duration of said first OFDM symbol corresponding to said first transmitter antenna is substantially equal to a rate of transmission of said first data within the duration of said second OFDM symbol corresponding to said second transmission antenna; and

a rate of transmission of said second data with the duration of said second OFDM symbol corresponding to said first transmitter antenna is substantially equal to a rate of transmission of said second data with the duration of said first OFDM symbol corresponding to said second transmission antenna.

11. An apparatus for transmitting data, comprising:

an orthogonal frequency division multiplexing (OFDM) encoder for loading;

a first data on a sub-carrier of an OFDM symbol associated with an antenna;

a second data on a sub-carrier of an another OFDM symbol associated with the antenna;

said first and said second data on sub-carriers of OFDM symbols associated with an another antenna according to at least one mapping rule, wherein said at least one mapping rule is a conjugate mapping rule; and

said antenna transmits said first data.

12. The apparatus of claim 11, further comprising:

said antenna transmits said second data; and

said another antenna transmits said first and said second data.

13. The apparatus of claim 11, wherein

said transmission of said first data with said another antenna is transmitted subsequent to said transmission of said first data with said antenna;

and

said transmission of said second data with said antenna is transmitted subsequent to said transmission of said second data with said another antenna.

14. The apparatus of claim 11, wherein said OFDM encoder is configured to load:

said first data on said sub-carrier of said OFDM symbols associated with said another antenna according to said conjugate mapping rule; and

said second data on said sub-carrier of said OFDM symbol associated with said another antenna according to a negative conjugate mapping rule.

15. The apparatus of claim 14, wherein

a rate of transmission of said first data with said antenna is substantially equal to a rate of transmission of said first data with said another antenna;

and

a rate of transmission of said second data with said antenna is substantially equal to a rate of transmission of said second data with said another antenna.