WIRELESS COMMUNICATIONS SYSTEM

Abstract

Wireless transmission of data is effected across a communications channel defined by a communications medium by means of an encoder, operable to apply a low density parity check (LDPC) code to data for transmission. The LDPC code is irregular with respect to the degree of variable nodes, and so the transmitter further comprises means for sorting encoded data with respect to the corresponding variable node degree, and modulation and distribution means for allocating encoded and sorted data onto the communications medium. The distribution of the data onto the communications medium is carried out with respect to a prior established pre-coding algorithm, such as SVD.

Description

Further aspects, features and advantages of the invention will now be described by means of specific embodiments of the invention, provided by way of example only, with reference to the accompanying drawings in which:

FIG. 1 illustrates a communications system including a MIMO transmitter in accordance with an embodiment of the invention, together with a receiver suitable for use therewith;

FIG. 2 illustrates a transmitter encoding train in accordance with a second embodiment of the invention;

FIG. 3 illustrates a transmitter encoding train in accordance with a third embodiment of the invention;

FIG. 4 illustrates a transmitter encoding train in accordance with a third embodiment of the invention;

FIG. 5 illustrates a communications device configured in accordance with the transmitter of the first described embodiment;

FIG. 6 illustrates variable node degree distribution for an irregular LDPC code of length 1000 bits;

FIG. 7 illustrates variable node degree of a 1000 bit length irregular LDPC code prior to sorting;

FIG. 8 illustrates the variable node degree of the code illustrated in FIG. 7, after sorting; and

FIGS. 9 and 10 illustrate experimental results obtained from a computer based simulation of an embodiment of the invention;

Claims

1. A wireless transmitter for transmitting data in a communications channel defined in a communications medium, the transmitter comprising an encoder, operable to apply a low density parity check (LDPC) code to data for transmission, the LDPC code being irregular with respect to the degree of variable nodes, sorting means for sorting encoded data with respect to the corresponding variable node degree, and modulation and distribution means for allocating encoded and sorted data onto the communications medium, the distribution means being operable to distribute the sorted data onto the communications medium in accordance with a predetermined preceding algorithm, such that the distribution order can be determined by a receiver without recourse to side information.

2. A wireless transmitter in accordance with claim 1 and wherein the distribution means is operable to distribute the sorted data onto the communications medium in accordance with singular value decomposition of a matrix representing the communications channel.

3. A wireless transmitter in accordance with claim 2 wherein the distribution means is operable to distribute the sorted data onto streams in the communications channel, defined by means of the singular value decomposition, with reference to the degree of the respective variable nodes of the LDPC coding.

4. A wireless transmitter in accordance with claim 3 wherein the distribution means is operable to distribute relatively higher degree symbols onto an SVD stream of relatively lower gain.

5. A wireless transmitter in accordance with claim 1 wherein the transmitter is for use in a MIMO based system.

6. A wireless transmitter in accordance with claim 1 wherein the transmitter is for use in an OFDM system.

7. A wireless receiver for receiving and decoding data transmitted in a communications channel defined in a communications medium, the receiver comprising demodulation means operable to demodulate data from a plurality of data streams, in accordance with a predetermined distribution algorithm, de-sorting means for reverting the received data to an unsorted condition, and a decoder operable to apply an LDPC parity check to decode the received, de-sorted data.

8. A wireless receiver in accordance with claim 7 wherein the demodulation means is operable in accordance with a predetermined preceding algorithm and without recourse to side information carried with the received data.

9. A method of transmitting data in a communications channel, the method comprising applying a low density parity check (LDPC) code to data for transmission, the LDPC code being irregular with respect to the degree of variable nodes, sorting encoded data with respect to the corresponding variable node degree, and allocating encoded and sorted data onto the communications channel in accordance with a predetermined precoding algorithm, such that the distribution order can be determined by a receiver without recourse to side information.

10. A method of receiving and decoding data transmitted in a communications channel defined in a communications medium, the method comprising demodulating data from a plurality of data streams, in accordance with a predetermined distribution algorithm, reverting the received data to an unsorted condition, and applying an LDPC parity check to decode the received, de-sorted data.

11. A computer program product comprising processor executable steps which are operable to configure computerised communications apparatus to perform the method of claim 9 or claim 10.