Constellation rearrangement for transmit diversity schemes
A method of transmitting data in a wireless communication system from a transmitter to a receiver, comprising the steps of modulating data at the transmitter using a first signal constellation pattern to obtain a first data symbol. The first data symbol is transmitteds to the receiver using a first diversity branch. Further, the data is modulated at the transmitter using a second signal constellation pattern to obtain a second data symbol. Then, the second data symbol is transmitted to the receiver over a second diversity path. Finally, the received first and second data symbol are diversity combined at the receiver. The invention further relates to a transmitter and a receiver embodies to carry out the method of invention.
1. A method of transmitting data in a wireless communication system from a transmitter to a receiver, the method comprising:
modulating data at the transmitter using a first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
transmitting the first data symbol to the receiver over a first diversity branch;
modulating said data at the transmitter using a second modulation scheme to obtain a second data symbol;
transmitting the second data symbol to the receiver over a second diversity branch;
demodulating the received first and second data symbols at the receiver using first and second demodulation schemes corresponding to the first and second modulation schemes, respectively; and
diversity combining the demodulated data, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining the data bits of the demodulated data, the differences among the combined bit reliabilities are reduced, and
the data for transmission is modulated using a single redundancy version scheme with an identical data bit sequence.
2. A method of transmitting data in a wireless communication system from a transmitter to a receiver, the method comprising:
modulating data at the transmitter using a first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
transmitting the first data symbol to the receiver over a first diversity branch;
modulating said data at the transmitter using a second modulation scheme to obtain a second data symbol;
transmitting the second data symbol to the receiver over a second diversity branch;
demodulating the received first and second data symbols at the receiver using first and second demodulation schemes corresponding to the first and second modulation schemes, respectively; and
diversity combining the demodulated data, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining the data bits of the demodulated data, the differences among the combined bit reliabilities are reduced, and
the data for transmission is modulated using a multiple redundancy version scheme of partly identical bits.
3. A method of transmitting data in a wireless communication system from a transmitter to a receiver, the method comprising:
modulating data at the transmitter using a first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
transmitting the first data symbol to the receiver over a first diversity branch;
modulating said data at the transmitter using a second modulation scheme to obtain a second data symbol;
transmitting the second data symbol to the receiver over a second diversity branch;
demodulating the received first and second data symbols at the receiver using first and second demodulation schemes corresponding to the first and second modulation schemes, respectively; and
diversity combining the demodulated data, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining the data bits of the demodulated data, the differences among the combined bit reliabilities are reduced,
first and second signal constellation patterns defining the first and second modulation schemes are prestored in a memory table, and
the properties of the first and second signal constellation patterns are obtained by:
(a) interleaving the positions of the bits mapped onto the signal constellation patterns, or
(b) inverting the bit values of the bits mapped onto the signal constellation patterns.
4. A method of transmitting data in a wireless communication system from a transmitter to a receiver, the method comprising:
modulating data at the transmitter using a first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
transmitting the first data symbol to the receiver over a first diversity branch;
modulating said data at the transmitter using a second modulation scheme to obtain a second data symbol;
transmitting the second data symbol to the receiver over a second diversity branch;
demodulating the received first and second data symbols at the receiver using first and second demodulation schemes corresponding to the first and second modulation schemes, respectively; and
diversity combining the demodulated data, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining the data bits of the demodulated data, the differences among the combined bit reliabilities are reduced, and
the data is transmitted with a plurality of redundancy versions, and the transmitted bits comprise systematic and parity bits and the systematic bits are included in each redundancy version.
5. The method according to claim 4 , wherein the combined mean bit reliabilities for the systematic bits are higher than that of the parity bits.
6. A transmitter for transmitting data in a wireless communication system to a receiver, the transmitter comprising:
a table component that pre-stores first and second signal constellation patterns defining first and second modulation schemes;
a mapping unit that modulates data using the first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
a transmitting unit that transmits the first data symbol to the receiver using a first diversity branch;
said mapping unit modulates said data using the second modulation scheme to obtain a second data symbol; and
said transmitting unit transmits the second data symbol to the receiver using a second diversity branch, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining demodulated data bits of the first and second data symbols received by the receiver, the differences among the diversity combined bit reliabilities are reduced
said transmitter further comprising one of an interleaver and an inverter to obtain different signal constellation patterns.
7. A method of transmitting data in a wireless communication system from a transmitter to a receiver, the method comprising:
modulating data at the transmitter using a first modulation scheme to obtain a first data symbol, the first modulation scheme being a higher order modulation scheme and data bits mapped onto data symbols have different bit reliabilities depending on the chosen modulation scheme;
transmitting the first data symbol to the receiver over a first diversity branch;
modulating said data at the transmitter using a second modulation scheme to obtain a second data symbol;
transmitting the second data symbol to the receiver over a second diversity branch;
demodulating the received first and second data symbols at the receiver using first and second demodulation schemes corresponding to the first and second modulation schemes, respectively; and
diversity combining the demodulated data, wherein:
the first and second modulation schemes for the first and second diversity branches are selected such that after diversity combining the data bits of the demodulated data, the differences among the combined bit reliabilities are reduced,
the first and second signal constellation patterns are signaled to the receiver,
the properties of the first and second signal constellation patterns are obtained by:
(a) interleaving the positions of the bits mapped onto the signal constellation patterns, or
(b) inverting the bit values of the bits mapped onto the signal constellation patterns.
8. The method according to claim 3 or 7 , wherein the interleaving is performed with symbols resulting in an intra-symbol interleaving.