Wireless communication of data symbols
A transmitter generates a constellation pattern comprising replications of a first constellation. Each replication has a replication offset relative to a neighbouring replication and alternates between corresponding to the first constellation and an axis mirrored constellation (mirrored around the real and/or imaginary axis). The transmitter selects from the pattern such that a symbol for a data value corresponding to a first constellation point of the first constellation is selected from all replications of this constellation point. The constellation point resulting in the lowest transmit power for a combination of a plurality of antennas may be selected. A receiver receives the selected symbol and provides a folding operation to compensate for replications and mirroring. The replication offset may be lower than the minimum distance between symbols in the first constellation thereby resulting in an improved trade off between transmit power and error probability, e.g. in a Multiple Input Multiple Output system.
1. A method of transmitting data symbols, the method comprising:
providing a constellation pattern comprising replications of a combined constellation with different translations such that each replication has a combination replication offset relative to a neighbouring replication, the combined constellation comprising at least a first constellation, a second constellation with a first translation offset between the first constellation and the second constellation and the second constellation corresponding to an axis mirroring of the first constellation around at least one of a real axis and an imaginary axis, and a third constellation with a second translation offset between the first constellation and the third constellation being different from the first translation offset, the third constellation corresponding to an axis mirroring of the first constellation around the real axis and the imaginary axis not used for the first axis mirroring;
a channel symbol selector, for selecting symbols for transmission from the constellation pattern, the selection including for a data value corresponding to a first constellation point of the first constellation selecting a symbol from replications of the first constellation point in the constellation pattern to meet a criterion; and
transmitting the selected symbols.
2. The method of claim 1 wherein the method comprises:
providing the first constellation comprising constellation points;
generating the second constellation by applying a first axis mirroring to the first constellation, the first axis mirroring being a mirroring around at least one of the real axis and the imaginary axis;
generating the combined constellation comprising at least the first constellation, the second constellation with the first translation offset between the first constellation and the second constellation, and the third constellation with a second translation offset between the first constellation and the third constellation being different from the first translation offset; and
generating the constellation pattern comprising replications of the combined constellation with different translations such that each replication has a combination replication offset relative to the neighbouring replication.
3. The method of claim 1 wherein the first translation offset is such that a first distance between at least one corresponding constellation point of the first constellation and the second constellation is less than a second distance between a pair of constellation points of the first constellation having a minimum distance of the first constellation.
4. The method of claim 3 wherein the first distance is between 10% and 90% percent of the second distance.
5. The method of claim 3 wherein the first distance is between 50% and 70% percent of the second distance.
6. The method of claim 1 wherein the combination replication offsets are such that a first distance between at least two corresponding constellation points of neighbouring replications is less than a second distance between a pair of constellation points of the first constellation having a minimum distance of the first constellation.
7. The method of claim 6 wherein the first distance is less than 90% percent of the second distance.
8. The method of claim 6 wherein the first distance is between 20% and 50% percent of the second distance.
9. The method of claim 1 wherein the combined constellation further comprises a fourth constellation with a third translation offset between the first constellation and the third constellation being different from the first translation offset and the second translation offset, the fourth constellation corresponding to an axis mirroring of the first constellation around both the real axis and the imaginary axis.
10. The method of claim 1 wherein selecting symbols comprises selecting a plurality of symbols for parallel transmission from a plurality of antennas; and transmitting the selected symbols comprises simultaneously transmitting the plurality of symbols from the plurality of antennas.
11. A method of receiving data symbols comprising:
receiving, by a receive circuitry, a received symbol corresponding to a constellation point selected from corresponding constellation points of a constellation pattern comprising replications of a first constellation, each replication having a replication offset relative to a neighbouring replication and each replication alternating between corresponding to the first constellation and a constellation of a set of at least one axis mirrored constellation of the first constellation around at least one of the real axis and an imaginary axis;
folding the received symbol into a region corresponding to the first constellation to generate a decoding symbol; wherein the folding comprises for at least a first axis of the real and the imaginary axis,
determining an integer replication offset between the received symbol and the region corresponding to the first constellation for the first axis:
generating an offset symbol by offsetting the received symbol along the first axis by a value corresponding to the integer replication offset multiplied by the replication offset; and
performing an axis mirroring of the offset symbol around a second axis of the real and the imaginary axis not being the first axis if the integer replication offset is odd; and
determining a received data symbol value from the decoding symbol.
12. The method of claim 11 wherein the replication offset is such that a first distance between at least two corresponding constellation points of neighbouring replications is less than a second distance between a pair of constellation points of the first constellation having a minimum distance.
13. The method of claim 12 wherein the replication offset along the first axis is equal to a sum of the first distance along the first axis and a second distance along the first axis.
14. The method of claim 11 wherein determining the integer replication offset comprises determining the integer replication offset as an integer closest to a first axis received symbol value of the received symbol divided by a first axis replication offset along the first axis.
15. The method of claim 11 wherein determining the integer replication offset comprises compensating the first axis received symbol value for a constellation pattern offset prior to determining the integer replication offset.
16. A transmitter for transmitting data symbols, the method comprising:
a unit for providing a constellation pattern comprising replications of a combined constellation with different translations such that each replication has a combination replication offset relative to a neighbouring replication, the combined constellation comprising at least a first constellation, a second constellation with a first translation offset between the first constellation and the second constellation and the second constellation corresponding to an axis mirroring of the first constellation around at least one of a real axis and an imaginary axis, and a third constellation with a second translation offset between the first constellation and the third constellation being different from the first translation offset, the third constellation corresponding to an axis mirroring of the first constellation around the real axis and the imaginary axis not used for the first axis mirroring;
a channel symbol selector for selecting symbols for transmission from the constellation pattern, the selection including for a data value corresponding to a first constellation point of the first constellation selecting a symbol from replications of the first constellation point in the constellation pattern to meet a criterion; and
a transmitter unit for transmitting the selected symbols.
17. A receiver for receiving data symbols comprising:
a receiving unit for receiving a received symbol corresponding to a constellation point selected from corresponding constellation points of a constellation pattern comprising replications of a first constellation, each replication having a replication offset relative to a neighbouring replication and each replication alternating between corresponding to the first constellation and a constellation of a set of at least one axis mirrored constellation of the first constellation around at least one of the real axis and an imaginary axis;
a processor for folding the received symbol into a region corresponding to the first constellation to generate a decoding symbol; wherein the folding comprises for at least a first axis of the real and the imaginary axis,
determining an integer replication offset between the received symbol and the region corresponding to the first constellation for the first axis;
generating an offset symbol by offsetting the received symbol along the first axis by a value corresponding to the integer replication offset multiplied by the replication offset; and
performing an axis mirroring of the offset symbol around a second axis of the real and the imaginary axis not being the first axis if the integer replication offset is odd; and
a decision unit for determining a received data symbol value from the decoding symbol.