Method and transmitter structure reducing ambiguity by repetition rearrangement in the symbol domain
View Patent ↗A method is provided which improves reliability of channel estimation in a digital communication system by reducing the ambiguity in the recognition of received symbols evaluated for the channel estimation. A data word transmitted according to a first mapping of data word values to modulation states is re-transmitted at least once with a second, re-arranged mapping of data word values to modulation states. The second mapping and possible further mappings are generated from the first mapping in a way that the number of different results which can be obtained from combining the transmitted original data symbol and the re-transmitted counterpart data symbol(s) is lower than the number of original modulation states in the first mapping.
1. A method for transmitting data in a digital communication system, the method comprising:
a) a first transmission step of transmitting a data word modulated on a carrier according to a first mapping of first concatenated data word values to modulation states; and
b) at least one further transmission step of transmitting the same data word modulated on a carrier according to at least one further mapping of further concatenated data word values to modulation states, wherein:
a number of different combined values obtainable, by adding for each of the first and further concatenated data word values, complex values associated with said first concatenated data word value according to said first mapping and further complex values associated with said further concatenated data word values according to said at least one further mapping, is lower than a number of different data word values within said first mapping, and
said first mapping and said at least one further mapping are obtained from a common super-mapping by pre-pending a leading control word to a data word, wherein the common super-mapping maps concatenated values of a control word and the data word having said leading control word pre-pended thereto to modulation states, and each of the first and the at least one further transmission is associated with a specific value of the control word, resulting in the respective first and further concatenated data word values.
2. The method according to claim 1 , wherein said transmitting steps are carried out subsequently on the same transmission channel.
3. The method according to claim 1 , wherein said digital communication system comprises a frequency division multiple access component, and said transmitting steps are carried out in different frequency channels.
4. The method according to claim 1 , wherein said transmission steps are applied to each transmitted symbol.
5. The method according to claim 1 , wherein said further transmission steps are applied to a defined number of data symbols per transmission frame.
6. A non-transitory computer-readable storage medium having stored thereon program instructions that, when executed in a processor of a transmitter of a digital communication system, cause the transmitter to perform the method according to claim 1 .