MULTI-CHANNEL THROUGH-WALL COMMUNICATION SYSTEM USING CROSSTALK SUPPRESSION

• US 20150085949A1
• Filed: 02/06/2013
• Published: 03/26/2015
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Rensselaer Polytechnic Institute
• Original Assignee: Rensselaer Polytechnic Institute
• Inventors: Saulnier, Gary J., Ashdown, Jonathan D., Lawry, Tristan J., Wilt, Kyle R., Scarton, Henry A.
• Granted Patent: US 9,331,879 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04B 11/00 Transmission systems employing sonic, ultrasonic or infrasonic waves
• CPC Class Codes: H04B 7/0413 MIMO systems
• CPC Class Codes: H04B 7/068 using space frequency diversity space-frequency coding H04L1/0606
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04L 25/08 Modifications for reducing interference; Modifications for reducing effects due to line faults ; Receiver end arrangements for detecting or overcoming line faults
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems

Abstract

A system for communicating through a solid wall uses piezoelectric transducers in a multiple-input multiple-output configuration and applies crosstalk suppression. Methods of suppressing or avoiding crosstalk between parallel communication channels includes zero-forcing, eigenmode transmission, and least mean squared error processing. Orthogonal frequency division multiplexing can be used to increase transmission rates using many subchannels. Bit-loading can be used to maximize system performance.

Claims

1. A method of sending signals through a barrier using multiple-input multiple-output (MIMO) channels comprising transducers and zero forcing crosstalk suppression, the method comprising the steps of:

providing a barrier, the barrier having a transmitter assembly on a first side of the barrier and a receiver assembly on a second side of the barrier;

wherein the transmitter assembly comprises a plurality of transmit transducers coupled to the first side of the barrier;

wherein the receiver assembly comprises a plurality of receiver transducers coupled to the second side of the barrier;

wherein equal numbers of transmit transducers and receiver transducers are provided, and wherein each transmit transducer is paired with and axially aligned with a corresponding receiver transducer on the opposite side of the barrier;

providing a plurality of communication channels for communicating signals through the barrier, wherein each communication channel comprises a portion of the barrier which is located between a pair of aligned transmit and receiver transducers, wherein the number of communication channels is the same as the number of transmit transducer and receiver transducer pairs, and wherein a plurality of the communication channels collectively form part of a MIMO signaling arrangement;

sending a transmit signal from the first side of the barrier through at least one communication channel using at least one transmit transducer;

receiving a receive signal vector at the receiver transducers;

determining a channel gain matrix H for the plurality of communication channels which are part of the MIMO signaling arrangement;

using zero forcing to cancel crosstalk within the MIMO signaling arrangement, wherein the step of using zero forcing comprises scaling the receive signal vector with the inverse of the channel gain matrix H.

2. The method of sending signals through a barrier of claim 1, wherein the step of sending a transmit signal from the first side of the barrier through the communication channels comprises using orthogonal frequency division multiplexing (OFDM);

and

wherein using OFDM comprises sending signals on a plurality of subcarriers.

3. The method of sending signals through a barrier of claim 2, wherein the process of determining a signal gain matrix H comprises the steps of:

the transmitter assembly transmitting known symbols on each subcarrier; and

the receiver assembly detecting the gain caused by each known symbol transmission at the plurality of receiver transducers.

4. The method of sending signals through a barrier of claim 2, wherein the process of determining a signal gain matrix H is repeated over time in order to track changes in signal gain over time.

5. The method of sending signals through a barrier of claim 2, wherein subcarriers are modulated including using phase key shifting (PSK).

6. The method of sending signals through a barrier of claim 2, wherein subcarriers are modulated including using quadrature amplitude modulation (QAM).

7. The method of sending signals through a barrier of claim 1, wherein the data rate of the MIMO signaling arrangement is at least as great as the combined total data rates of the plurality of communications channels if each communication channel is instead used individually.

8. The method of sending signals through a barrier of claim 2, wherein the step of sending the transmit signal through the communication channels comprises using bit-loading;

wherein bit-loading is implemented including by the transmitter assembly and the receiver assembly;

wherein the receiver assembly provides receiver side information, including information regarding subcarrier signal to noise ratios, to the transmitter assembly; and

wherein the transmitter assembly uses the receiver side information to determine a modulation level for use with each of a plurality of subcarriers.

9. The method of sending signals through a barrier of claim 8, wherein bit-loading implementation further comprises the steps of:

choosing a target bit error rate (BER);

choosing a modulation type;

choosing at least one modulation level;

calculating a target minimum signal to noise ratio (SNR) required to achieve the target bit error rate for a plurality of modulation levels; and

for each OFDM subcarrier, determining whether a first modulation level results in a SNR high enough to support bit-loading without exceeding the target bit error rate, and if the SNR is too low trying a higher modulation level, and if the SNR level is satisfactory filling a current frequency bin with a number of bits associated with the first modulation level.

10. A method of sending signals through a barrier using multiple-input multiple-output (MIMO) channels comprising transducers and eigenmode transmission, the method comprising the steps of:

providing a barrier, the barrier having a transmitter assembly on a first side of the barrier and a receiver assembly on a second side of the barrier;

wherein the transmitter assembly comprises a plurality of transmit transducers coupled to the first side of the barrier;

wherein the receiver assembly comprises a plurality of receiver transducers coupled to the second side of the barrier;

wherein equal numbers of transmit transducers and receiver transducers are provided, and wherein each transmit transducer is paired with and axially aligned with a corresponding receiver transducer on the opposite side of the barrier;

providing a plurality of communication channels for communicating signals through the barrier, wherein each communication channel comprises a portion of the barrier which is located between a pair of aligned transmit and receiver transducers, wherein the number of communication channels is the same as the number of transmit transducers and the number of receiver transducers, and wherein a plurality of the communication channels collectively form a MIMO signaling arrangement;

providing a transmit signal vector x;

multiplying the transmit signal vector x by a precoding matrix to produce a linearly transformed input vector;

transmitting the linearly transformed input vector from the first side of the barrier through the barrier using the MIMO signaling arrangement, wherein the communication channels making up the MIMO signaling arrangement are mathematically represented by a channel gain matrix H;

the receiver assembly receiving the linearly transformed input vector as a received signal vector at the second side of the barrier; and

shaping the received signal vector by performing a linear transformation on the received signal vector using a receiver shaping matrix and thereby producing and output signal vector.

11. The method of sending signals through a barrier of claim 10, wherein the step of transmitting the linearly transformed input vector from the first side of the barrier through the barrier comprises using orthogonal frequency division multiplexing (OFDM);

and

wherein using OFDM comprises sending signals on a plurality of subcarriers.

12. The method of sending signals through a barrier of claim 11, wherein subcarriers are modulated including using phase key shifting (PSK).

13. The method of sending signals through a barrier of claim 11, wherein subcarriers are modulated including using quadrature amplitude modulation (QAM).

14. The method of sending signals through a barrier of claim 11, wherein the data rate of the MIMO signaling arrangement is at least as great as the combined total data rates of the plurality of communications channels if each communication channel is instead used individually.

15. The method of sending signals through a barrier of claim 11, further comprising using bit-loading;

wherein bit-loading is implemented including by the transmitter assembly and the receiver assembly;

wherein the receiver assembly provides receiver side information, including information regarding subcarrier signal to noise ratios, to the transmitter assembly; and

wherein the transmitter assembly uses the receiver side information to determine a modulation level for use with each of a plurality of subcarriers.

16. The method of sending signals through a barrier of claim 15, wherein bit-loading implementation further comprises the steps of:

choosing a target bit error rate (BER);

choosing a modulation type;

choosing at least one modulation level;

calculating a target minimum signal to noise ratio (SNR) required to achieve the target bit error rate for a plurality of modulation levels; and

for each OFDM subcarrier, determining whether a first modulation level results in a SNR high enough to support bit-loading without exceeding the target bit error rate, and if the SNR is too low trying a higher modulation level, and if the SNR level is satisfactory filling a current frequency bin with a number of bits associated with the first modulation level.

17. The method of sending signals through a barrier of claim 10, further comprising deriving at least one decision variable from the output signal vector.

18. A method of sending signals through a barrier using multiple-input multiple-output (MIMO) channels comprising transducers and using minimum mean-squared error (MMSE) crosstalk suppression, the method comprising the steps of:

providing a barrier, the barrier having a transmitter assembly on a first side of the barrier and a receiver assembly on a second side of the barrier;

wherein the transmitter assembly comprises a plurality of transmit transducers coupled to the first side of the barrier;

wherein the receiver assembly comprises a plurality of receiver transducers coupled to the second side of the barrier;

wherein equal numbers of transmit transducers and receiver transducers are provided, and wherein each transmit transducer is paired with and axially aligned with a corresponding receiver transducer on the opposite side of the barrier;

providing a plurality of communication channels for communicating signals through the barrier, wherein each communication channel comprises a portion of the barrier which is located between a pair of aligned transmit and receiver transducers, wherein the number of communication channels is the same as the number of transmit transducer and receiver transducer pairs, and wherein a plurality of the communication channels collectively form a MIMO signaling arrangement;

sending a transmit signal vector from the first side of the barrier through at least one communication channel using at least one transmit transducer;

receiving a receive signal vector at the receiver transducers;

determining a weight matrix W for the plurality of communication channels which are part of the MIMO signaling arrangement; and

using minimum mean-squared error processing to cancel crosstalk within the MIMO signaling arrangement, wherein the step of using minimum mean-squared error processing to cancel crosstalk comprises scaling the receive signal vector with the weight matrix W.

19. The method of sending signals through a barrier of claim 18, wherein the step of sending a transmit signal from the first side of the barrier through the communication channels comprises using orthogonal frequency division multiplexing (OFDM);

and

wherein using OFDM comprises sending signals on a plurality of subcarriers.

20. The method of sending signals through a barrier of claim 18, wherein the weight matrix W is updated over time.

21. The method of sending signals through a barrier of claim 18, wherein the process of updating the weight matrix W comprises determining an error vector by comparing the transmit signal vector with the result of scaling the receive signal vector with the weight matrix W.

22. The method of sending signals through a barrier of claim 18, wherein subcarriers are modulated including using phase key shifting (PSK).

23. The method of sending signals through a barrier of claim 18, wherein subcarriers are modulated including using quadrature amplitude modulation (QAM).

24. The method of sending signals through a barrier of claim 18, wherein the data rate of the MIMO signaling arrangement is at least as great as the combined total data rates of the plurality of communications channels if each communication channel is instead used individually.

25. The method of sending signals through a barrier of claim 19, wherein the step of sending the transmit signal through the communication channels comprises using bit-loading;

wherein bit-loading is implemented including by the transmitter assembly and the receiver assembly;

wherein the receiver assembly provides receiver side information, including information regarding subcarrier signal to noise ratios, to the transmitter assembly; and

wherein the transmitter assembly uses the receiver side information to determine a modulation level for use with each of a plurality of subcarriers.

26. The method of sending signals through a barrier of claim 25, wherein bit-loading implementation further comprises the steps of:

choosing a target bit error rate (BER);

choosing a modulation type;

choosing at least one modulation level;

calculating a target minimum signal to noise ratio (SNR) required to achieve the target bit error rate for a plurality of modulation levels; and

for each OFDM subcarrier, determining whether a first modulation level results in a SNR high enough to support bit-loading without exceeding the target bit error rate, and if the SNR is too low trying a higher modulation level, and if the SNR level is satisfactory filling a current frequency bin with a number of bits associated with the first modulation level.

27. A method of sending signals through a barrier using multiple-input multiple-output (MIMO) channels comprising transducers and zero forcing crosstalk suppression, the method comprising the steps of:

providing a barrier, the barrier having a transmitter assembly on a first side of the barrier and a receiver assembly on a second side of the barrier;

wherein the transmitter assembly comprises a plurality of transmit transducers coupled to the first side of the barrier;

wherein the receiver assembly comprises a plurality of receiver transducers coupled to the second side of the barrier;

wherein equal numbers of transmit transducers and receiver transducers are provided, and wherein each transmit transducer is paired with and axially aligned with a corresponding receiver transducer on the opposite side of the barrier;

providing a plurality of communication channels for communicating signals through the barrier, wherein each communication channel comprises a portion of the barrier which is located between a pair of aligned transmit and receiver transducers, wherein the number of communication channels is the same as the number of transmit transducer and receiver transducer pairs, and wherein a plurality of the communication channels collectively form part of a MIMO signaling arrangement;

sending a transmit signal from the first side of the barrier through at least one communication channel using at least one transmit transducer;

receiving a receive signal vector at the receiver transducers; and

reducing cross-talk among the transmitted and received signals.

28. The method of sending signals through a barrier of claim 27, wherein the reducing of cross-talk among the transmitted and received signals is achieved by at least one of:

zero forcing;

eigenmode transmission; and

minimum mean-square error.