Layer mapping method and data transmission method for MIMO system
A method for indicating a combination between a codeword and a layer in a MIMO communication system, a layer mapping method, and a data transmission method using the same are disclosed. A minimum number of codeword-layer mapping combinations from among all available combinations based on the numbers of all codewords and all layers are pre-defined in consideration of a ratio of a codeword to a layer, a reception performance of a receiver, and reduction of combinations, so that a data transmission method using the predefined combinations is implemented. If a specific one codeword is mapped to at least two layers, a diversity gain can be acquired.
1. A layer mapping method for spatial multiplexing in a Multi-Input Multi-Output (MIMO) system, the layer mapping method comprising:
mapping symbols associated with each codeword to a corresponding at least one layer according to one of a plurality of mapping combinations;
precoding the symbols mapped to the corresponding at least one layer to produce a precoded signal; and
transmitting the precoded signals,
wherein the maximum number of layers to which the symbols associated with a single codeword are mapped is equivalent to the maximum number of layers employed by the MIMO system divided by the maximum number of codewords,
wherein the plurality of mapping combinations comprise only one mapping combination for each combination of a number of codewords and a number of layers,
wherein the plurality of mapping combinations comprise first mapping combinations for one codeword and second mapping combinations for multiple codewords, and
wherein the first mapping combinations comprise all possible mapping combinations for retransmitting only one codeword among the multiple codewords of the second mapping combinations.
2. The method according to claim 1 , wherein mapping the symbols associated with each codeword to the corresponding at least one layer comprises:
alternately mapping the symbols associated with one codeword to two layers.
3. The method according to claim 1 , wherein mapping the symbols associated with each codeword to the corresponding at least one layer comprises:
mapping the symbols associated with a first codeword to a corresponding first layer; and
alternately mapping the symbols associated with a second codeword to a corresponding second and third layers.
4. The method according to claim 1 , wherein mapping the symbols associated with each codeword to a corresponding at least one layer comprises:
alternatively mapping the symbols associated with a first codeword to a corresponding first and second layers; and
alternatively mapping the symbols associated with a second codeword to a corresponding third and fourth layers.
5. The method according to claim 1 , wherein the MIMO system employs
a maximum of 4 layers and a maximum of 2 codewords, and
wherein the plurality of mapping combinations limits the number of layers to which the symbols associated with a single codeword are mapped to 2.
6. The method according to claim 5 , wherein the symbols associated with at least one codeword are alternately mapped to two layers.
7. The method according to claim 1 , wherein the MIMO system uses a maximum of 4 layers and maximum of 2 codewords, and wherein the plurality of mapping combinations includes:
a first combination in which the symbols associated with a single codeword are mapped to a single layer;
a second combination in which the symbols associated with each of two codewords are mapped to two layers, respectively;
a third combination in which the symbols associated with each of two codewords are mapped to three layers, and
a fourth combination in which the symbols associated with each of two codewords are mapped to four layers.
8. The method according to claim 7 , wherein, according to the third or fourth combination, the symbols associated with at least one codeword are alternately mapped to two layers.
9. The method according to claim 7 , wherein the plurality of mapping combinations further includes:
a fifth combination in which the symbols associated with a single codeword are alternatively mapped to two layers.
10. A transmitter for a layer mapping in a Multi-Input Multi-Output (MIMO) system, the transmitter comprising:
at least one antenna;
a layer mapper configured to map one or more codewords to one or more layers according to one mapping combination from among a plurality of mapping combinations; and
a precoder receiving the one or more layers from the layer mapper and precoding the one or more layers to generate signals to be transmitted via the at least one antenna,
wherein a maximum number of the layers to which a single codeword is mapped is equivalent to a maximum number of the layers employed by the MIMO system divided by a maximum number of the codewords employed by the MIMO system,
wherein the plurality of mapping combinations comprise only one mapping combination for each combination of a number of codewords and a number of layers,
wherein the plurality of mapping combinations comprise only one mapping combination for a combination of a number of codewords and a number of layers,
wherein the plurality of mapping combinations comprise first mapping combinations for one codeword and second mapping combinations for multiple codewords, and
wherein the first mapping combinations comprise all possible mapping combinations for retransmitting only one codeword among the multiple codewords of the second mapping combinations.
11. The transmitter of claim 10 , wherein the maximum number of the codewords employed by the MIMO system is 2,
wherein the maximum number of the layers employed by the MIMO system is 4, and
wherein the maximum number of the layers to which the single codeword is mapped is equivalent to 2.
12. The transmitter of claim 11 , wherein the plurality of mapping combination comprise:
a first combination in which a single codeword is mapped to a single layer,
a second combination in which two codewords are respectively mapped to two layers,
a third combination in which two codewords are mapped to three layers, and
a fourth combination in which two codewords are mapped to four layers.
13. The transmitter of claim 11 , wherein the plurality of mapping combination consists of:
a first combination in which a single codeword is mapped to a single layer,
a second combination in which two codewords are respectively mapped to two layers,
a third combination in which two codewords are mapped to three layers,
a fourth combination in which two codewords are mapped to four layers, and
a fifth combination in which a single codeword is mapped to two layers.