METHODS AND DEVICES FOR COMMUNICATIONS SYSTEMS USING MULTIPLIED RATE TRANSMISSION

• US 20150110216A1
• Filed: 04/29/2013
• Published: 04/23/2015
• Est. Priority Date: 04/27/2012
• Status: Active Grant

• Current Assignee: McGill University
• Original Assignee: McGill University
• Inventors: Bajcsy, Jan, Kim, Yong-Jin, Garba, Aminata Amadou
• Granted Patent: US 9,473,332 B2
• Time in Patent Office: Days
• US Class Current: 375/285
• CPC Class Codes: H04B 1/40 Circuits
• CPC Class Codes: H04L 2025/03414 Multicarrier
• CPC Class Codes: H04L 2025/03426 transmission using multiple-input and multiple-output channels
• CPC Class Codes: H04L 25/03171 Arrangements involving maximum a posteriori probability [MAP] detection
• CPC Class Codes: H04L 25/03197 methods of calculation involving metrics
• CPC Class Codes: H04L 25/03343 Arrangements at the transmitter end
• CPC Class Codes: H04L 25/06 Dc level restoring means; Bias distortion correction ; Decision circuits providing symbol by symbol detection
• CPC Class Codes: H04L 27/34 Amplitude- and phase-modulated carrier systems, e.g. quadrature-amplitude modulated carrier systems
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

Cost, electronic circuitry limitations, and communication channel behaviour yield communication systems with strict bandwidth constraints. Hence, maximally utilizing available bandwidth is crucial, for example in wireless networks, to supporting ever increasing numbers of users and their demands for increased data volumes, low latency, and high download speeds. Accordingly, it would be beneficial for such networks to support variable bandwidth allocations such that smaller frequency sub-bands are allocated to users, as their number increases, but the individual users/nodes insert more data-carrying signals in order to compensate pensate for the loss of operating bandwidth arising from the accommodation of more users. It would further be beneficial for transmitters and receivers according to embodiments of such a network architecture to be based upon low cost design methodologies allowing their deployment within a wide range of applications including high volume, low cost consumer electronics for example.

Claims

1. A communication system comprising:

a transmitter comprising;

a covariance inducing module configured to accept blocks of transmission values and generate blocks of modulation values in dependence upon at least the blocks of transmission values; and

a modulation unit coupled to the covariance inducing module configured to accept the blocks of the modulation values and form a corresponding transmission signal for transmission over a continuous channel in dependence upon at least the blocks of modulation values and a signalling signal; and

a receiver comprising;

a demodulation unit configured to accept a received signal from the continuous channel, and generate blocks of demodulated values in dependence upon at least the received signal; and

an covariance—

intersymbol interference (ISI) reducing module configured to accept the blocks of demodulated values and form decoded values in dependence upon at least the blocks of demodulated values, each decoded value being an estimate of a transmission value;

wherein the covariance inducing and covariance—

ISI reducing modules are configured to apply to the transmission signal and remove from the received signal a predetermined intersymbol interference applied to a transmission established in dependence upon at least a multiplier factor K and a signal pulse characterized by at least a bandwidth B.

2. The system according to claim 1 wherein the modulation unit encodes the modulation values using a plurality of signal pulses spaced by T/K where T is the Nyquist rate associated with a signal of bandwidth B and K is greater than 1.

3. The system according to claim 1 wherein the multiplier factor K is selected according to characteristics of the continuous channel.

4. The system according to claim 1 wherein at least one of:

the blocks of transmission values provided to the covariance inducing module have been pre-processed with at least one error correcting code of a plurality of error correcting codes; and

the covariance—

ISI reducing module performs iterative processing of at least one of soft and probability values to establish the estimate of a transmission value.

5. The system according to claim 1 wherein the modulation unit implements an encoding of the modulation values using a series of modulation pulses s₀(t), s₁(t), . . . , s_M−

1(t) at asynchronous time instances 0≦

τ

₀<

τ

₁<

. . . <

τ

<sub>N−

1</sub> chosen so that the average rate of sending the modulation values exceeds the Nyquist rate.

6. The system according to claim 1 wherein the covariance inducing module is configured to transform the transmission values as a matrix multiplication by a matrix proportional to H⁻

1/2, where a covariance of noise introduced by the continuous channel into the demodulation values is proportional to H.

7. A transmitter comprising:

a covariance inducing module configured to accept blocks of transmission values and generate blocks of modulation values in dependence upon at least the blocks of transmission values; and

a modulation unit coupled to the covariance inducing module configured to accept the blocks of the modulation values and form a corresponding transmission signal for transmission over a continuous channel in dependence upon at least the blocks of modulation values and a signalling signal;

wherein the covariance inducing module is configured to apply to the transmission signal a predetermined covariance established in dependence upon at least a multiplier factor K and a signal pulse characterized by at least a bandwidth B.

8. The transmitter according to claim 7 wherein the modulation unit encodes the modulation values using a plurality of signal pulses spaced by T/K where T is the Nyquist rate associated with a signal of bandwidth B and K is greater than 1.

9. The transmitter according to claim 7 wherein the multiplier factor K is selected according to characteristics of the continuous channel.

10. The transmitter according to claim 7 wherein at least one of:

the blocks of transmission values provided to the covariance inducing module have been pre-processed with at least one error correcting code of a plurality of error correcting codes;

the modulation unit implements an encoding of the modulation values using a series of modulation pulses s₀(t), s₁(t), . . . , s<sub>M−

1</sub>(t) at asynchronous time instances 0≦

τ

₀<

τ

₁<

. . . <

τ

<sub>N−

1</sub> chosen so that the average rate of sending the modulation values exceeds the Nyquist rate; and

the covariance inducing module is configured to transform the transmission values as a matrix multiplication by a matrix proportional to H<sup>−

1/2</sup>, where a covariance of noise introduced by the continuous channel into the demodulation values is proportional to H.

11. The transmitter according to claim 7 wherein either the modulation unit operates as a linear time-invariant (LTI) transmit filter or the covariance inducing unit and modulation unit are provided as a single stage linear time-varying transmit filter.

12. The transmitter according to claim 11 wherein the impulse response of the linear time-varying transmit filter is such that it introduces the desired covariance into the transmitted data and performs a linear time-invariant filtering.

13. The transmitter according to claim 7 wherein the covariance inducing unit and modulation unit comprise a signal generator generating a plurality of time offset pulses and a plurality of encoders for encoding an original uncorrelated data stream upon the plurality of time offset pulses, wherein when combined the encoded plurality of pulse streams have the desired covariance.

14. A transmitter comprising:

a first transmitter section for modulating first blocks of modulation values according to one or more modulation pulses s₀(t), s₁(t), . . . , s<sub>M−

1</sub>(t) with a rate of 1/T values per second; and

a second transmitter section for communicating additional data in addition to the modulation values modulated by the first transmitter section by adding additional modulation pulses between the pulses generated by the first transmitter section.

15. The transmitter according to claim 14 wherein the T is less than or equal to the Nyquist rate for the modulation pulse but the combined rate of modulation pulses modulated by the first transmitter section and the second transmitter section exceeds the Nyquist rate.

16. A receiver comprising:

a demodulation unit configured to accept a received signal from the continuous channel, and generate blocks of demodulated values in dependence upon at least the received signal; and

a covariance—

ISI reducing module configured to accept the blocks of demodulated values and form decoded values in dependence upon at least the blocks of demodulated values, each decoded value being an estimate of a transmission value;

wherein the covariance—

ISI reducing module is configured to remove from the received signal a predetermined intersymbol interference applied to a transmission applied to a transmission channel coupled to the continuous channel, the predetermined intersymbol interference established in dependence upon at least a multiplier factor K and a signal pulse characterized by at least a bandwidth B.

17. The receiver according to claim 16 wherein the received signal comprises data encoded using a plurality of signal pulses spaced by T/K where T is the Nyquist rate associated with a signal of bandwidth B and K is greater than 1.

18. The receiver according to claim 16 wherein the multiplier factor K is selected according to characteristics of the continuous channel.

19. The receiver according to claim 16 wherein the covariance—

ISI reducing module performs iterative processing of at least one of soft and probability values to establish the estimate of a transmission value.

20. The receiver according to claim 16 wherein the received signal comprises data generated by encoding of the modulation values using a series of modulation pulses s₀(t), s₁(t), . . . , s_M−

1(t) at asynchronous time instances 0≦

τ

₀<

τ

₁<

. . . τ

<sub>N−

1</sub> chosen so that the average rate of sending the modulation values exceeds the Nyquist rate.

21. The receiver according to claim 16 further comprising;

a network discovery module, the network discovery module establishing that the received signal comprises N messages broadcast to N users and that M other receivers have better noise than the receiver; and

the covariance—

ISI reducing module performs iterative processing to decode N−

M messages in order to establish the message intended for that receiver.

22. The receiver according to claim 16 further comprising an equalizer evaluating in an iteration of decoding at least one of soft outputs and reliability values of data and receiving likelihood ratios relating to values of the data in a preceding iteration.

23. The receiver according to claim 16 wherein the receiver comprises at least one of:

a matched filter and an intersymbol interference reducing module exploiting the covariance structure of the received signal;

a plurality of matched filters; and

a plurality of time-varying correlators, each correlator followed by at least an integrator.