Enhanced spatial multiplexing

1. A method of spatially multiplexing data comprising a signal vector, the method comprising:

selecting first and second modulation schemes for a data transmission wherein the second modulation scheme is an interpolation in the plane of the first modulation scheme; and further wherein the modulation schemes are selected so as to maintain the same minimum Euclidean distance between vectors comprising the first and second modulation schemes as the minimum Euclidean distance within the first and second modulation schemes; and

selecting a plurality of antennae, each of the plurality to concurrently transmit respective symbols of the signal vector;

wherein a portion of the respective symbols taking their values from the first modulation scheme take their values from a subset of the first modulation scheme; and wherein points of the subset of the first modulation scheme have reduced energy compared to other points of the first modulation scheme;

wherein the first modulation scheme comprises a first constellation and the second modulation scheme comprises a second constellation;

wherein third and fourth constellations are provided by a second interpolation;

wherein a combination of modulation schemes used to transmit the signal vector is represented by two binary sequences, one of the two binary sequences forms a repetition code and the other binary sequence forms a parity-check code.

2. The method of claim 1 wherein the modulation schemes are chosen so that points of any one modulation scheme are equidistant from neighbor points of any one other modulation scheme.

3. The method of claim 1 wherein a number of components from the transmitted signal vector taking their value from the second modulation scheme is even.

4. The method of claim 1 wherein one component on the signal vector takes its value from the first modulation scheme and N−1 components on the signal vector take their values from either the secondary modulation scheme or the subset of the first modulation scheme.

5. The method of claim 1 wherein the minimum Euclidean distance within the third and fourth constellations is the same as the minimum Euclidean distance within the first and second constellations.

6. The method of claim 1 wherein each constellation comprises a 4-point constellation.

7. The method of claim 1 wherein the minimum Euclidean distance between vectors comprising each constellation is the same.

8. The method of claim 1 wherein only points of the subset of the first modulation scheme are used.

9. The method of claim 1 wherein the fourth constellation is a π/2 rotation of the third constellation.

10. The method of claim 1 wherein an additional four constellations are derived from a third interpolation and used to increase a number of modulation combinations.

11. A system comprising the plurality of antennae to transmit the signal vector according to the method of claim 1 .

12. The system of claim 11 further comprising a receiver arranged to receive the signal vector and to determine the data transmitted in the signal vector.

13. A non-transitory computer readable medium comprising instructions that when executed by a processor cause the processor to carry out the method of claim 1 .