WE CLAIM :

1, A method for transmitting on four transmit antennas comprising:

pre-coding information bits to generate four transmit symbols;

encoding two of the transmit symbols into a first Alarnouti matrix and encoding another two of the transmit symbols into a second Alamouti matrix,- transmitting the two Alamouti matrices on four antennas over four time intervals or four frequencies by:

transmitting the first Alamouti matrix on two antennas and two of the four time intervals or two of the four frequencies;

transmitting the second Alamouti matrix on the other two antennae and the other two of the four time intervals or the other two of the four frequencies;

wherein the pre-coding and encoding are such that all of the information bits are represented in what is transmitted from each antenna.

2. The method of claim 1, wherein the pre-coding comprises ;

generating the four transmit symbols by mapping M information bite as two sets of M/2 bits, wherein the first set of M/2 bits is mapped on a first and a third 2^{(M/2>} QAM mapping constellation to produce first and third transmit symbols, and the second set of M/2 bits is mapped on a second and a fourth 2^{tM/2>} QAM mapping constellation to produce second and fourth transmit symbols, wherein the first and second transmit symbols are encoded in the first Alamouti matrix and the third and fourth transmit .symbols are encoded in the second Alamouti matrix.

3. The method of claim 2 wherein the third and fourth mapping constellations are permuted mappings of the first second and mapping constellations, respectively.

4. The method of claim 2 or 3 wherein the second and fourth mapping constellations are the same as the first and third mapping constellations, respectively.

Ξ. The method of claim 1, wherein the pre-coding comprises :

mapping four pairs of information bits to 4-PSK symbols by mapping each pair of bits on a respective one of four rotated 4-PSK mapping constellations,- generating transmit symbols by forming

combinations of the real and imaginary components of the 4-PSK symbols.

6. The method of claim 5 wherein forming combinations of the real and imaginary components of the 4-PSK symbols comprises generating the following transmit symbols :

, and

, where Ci is the first rotated 4-PSK mapping constellation, G_{2} is the second rotated 4-PSK mapping constellation, Ca is the third rotated 4-PSK mapping

constellation, and C_{4} is the fourth rotated 4-PSK mapping constellation.

7. The method of claim 5 wherein each, respective one of four rotated. 4 PSK mapping constellations is rotated by an angle π/4 - θ where θ-tan^{"1} (1/3) .

S. The method of claim 1, wherein the pre-coding comprises!

generating four transmit symbols by mapping M information bits as two sets o£ M/2 bits, wherein the first pet of M/2 bits is mapped on one layer of a first two layer p_{SK ma}pp.j__{ng}^{.} constellation and one layer of a second two

layer

PSK mapping constellation to produce first and third transmit symbols, and the second set of M/2 bits is mapped on the other layer of the first two layer 2^{mfϊ)} PSK mapping constellation and the other layer of the second two layer 2^{wn)} PSK mapping constellation to produce second and fourth transmit symbols,

wherein the first and second transmit symbols are encoded in the first Alamαuti matrix and the third and fourth transmit symbols are encoded in the second Alamouti matrix.

9. The method of claim 5, further comprising using a rotation angle of the rotated 4-PSK mapping constellations to increase a minimum determinant distance of a 4X4 matrix containing the first and second Alamouti matrices,

10. The method of claim 9 wherein the rotation angle

11. A four transmit antenna transmitter for performing the methods of any one of claims 1 to 10.

12. A device for receiving and decoding the

transmitted first and aeσond Alamouti matrices of any one of the methods of claims 1 to 10.

13. A method for transmitting on three transmit antennas comprising:

pre-coding information bits to generate transmit symbols,- encoding the generated transmit symbols using a space time/frequency block code in which each transmit symbol appears an equal number of times and in such a manner that each of the three transmit antennas is utilized

equally;

transmitting the apace time/frequency block code over the three antennas;

wherein the pre-coding and encoding are such that all of the information bits are represented in what is transmitted from each antenna.

14. A method for transmitting on three transmit antennas comprising transmitting an Alamouti matrix on two antennas, time multiplexed with a single transmit symbol transmitted on a third antenna resulting in a block diagonal code matrix with 2X2 and 1X1 matrices as the diagonal elements.

15. The method of claim 13, wherein the pre-coding comprises ;

mapping four pairs of information bits to 4 PSK symbols by mapping each pair of bite on a respective one of four rotated 4 PSK mapping constellations;

generating transmit symbols by forming

combinations of the real and imaginary components of the 4 PSK symbols.

16. The method of claim 15 wherein forming

combinations of the real and imaginary components of the 4 PSK symbols comprises?

generating the following transmit symbols

, wherein Gi is the first rotated 4 PSK mapping constellation, C_{2} is the second rotated 4 PSK mapping constellation, C_{3} is the third rotated 4 PSK mapping

constellation, and C_{4} is the fourth rotated 4 PSK mapping constellation.

17. The method of claim 15 wherein each respective one of four rotated 4 PSK mapping constellations is rotated by an angle π/4 - θ where θ=tan^{"1}{l/3) .

18. A method for transmitting a rate-1 space-time block code for a 2n+l antenna transmitter where n>=l, the method comprising transmitting at least one code set by:

for each pair of consecutive transmission

intervals:

on each OFDM sub-carrier of a plurality of OFDM sub-carriers, transmitting a respective Alamouti code block containing two transmit symbols on a respective pair of antennas such that all sub-carriers are used and only one pair of antennas is active during a given pair of

consecutive transmission intervals for a given sub-carrier.

19. The method of claim 18, wherein there are three transmit antennas, and during the pair of consecutive transmission intervals every third sub-carrier starting at k is active on a first pair of transmit antennas, every third sub-carrier starting at k+l is active on a second pair of transmit antennas, and every third sub-carrier starting at k+2 is active on. a third pair of transmit antennas, where k ie an index of a first sub-carrier of the plurality of OPDM sub-carriers.

20. The method of claim 18, wherein the active antennas of the given sub-carrier alternate every pair of consecutive transmission intervals.

21. The method of claim 18, wherein the at least one code set: is one or more of a group of code sets consisting of:

Code Set-1

Code Set-2

Code Set-3

22. A method for transmitting a rate=2 space-time block code for a three antenna transmitter, the method comprising transmitting at least one code set by.

for each pair of transmission intervals:

on each OFDM sub-carrier of a plurality of OFDM sub-carriers _{/} transmitting one code set containing four transmit symbols on the three antennas such that all sub- σarriera are used and all three antennas are active during a given pair of transmission intervals for a given @ub- σarrier.

23. The method of claim 22 wherein transmitting one code set comprises transmitting an orthogonal space

time/frequency code block including two transmit symbols on two transmit antennas and two transmit symbols on a third transmit antenna.

24. The method of claim 22 wherein the at least one code set is one or more of a group of code sets consisting

Of:

Code Set-1

Code Set-2

Code Set-3

25. The method of any one o£ claims 18 to 24 further comprising:

receiving feedback pertaining to transmission channels of the antennas;

selecting, as a function of the feedback how the antennas are to be used in transmitting the at least one code set .

26. The method of claim 25, wherein transmitting at least one code set comprises transmitting an Alamouti matrix on two antennas determined to be most correlated.

27. The method of claim 26, wherein the feedback is an indicator of which antennas are most correlated.

28. The method of claim IS to 24, wherein

transmitting at least one code set comprises transmitting multiple code sets on a selected set of subcarriers to introduce additional diversity gain into the system.

29. A method for generating a space time/frequency code for a multi-antenna transmitter comprising:

combining various fixed rate space time/frequency codes for a given block length, of time intervals or

frequencies in a manner that the combination of various fixed rate space time/frequency codes utilize the entire transmission space of the given block length for each transmit antenna of the multi-antenna transmitter resulting in a space time/frequency code rate that is a function of each fixed rate space time/frequency code utilized.

30. The method of claim 29 wherein combining various fixed rate space time/frequency codes comprises combining two or more different fixed rate space time/frequency codes selected from a group of fixed rate space time/frequency codes consisting of:

a fixed rate space time/frequency code comprising one symbol in one block that is capable of being transmitted on one antenna;

a fixed rate space time/frequency code comprising two symbols in two blocks that are transmitted on two antennas ; and

a fixed rate space time/frequency code comprising three symbols in two blocks Chat are transmitted on three antennas .

31. A multi-antenna transmitter for performing the method of claim 29 or claim 30.

32. The method of any one of claims 2 to 4 and 7 wherein M=S .

33. A method of transmitting over three transmit antennas comprising •

for each antenna, generating a respective sequence of OPDM symbols, each OFDM symbol having a plurality of sub-carriers carrying data or pilots, and, transmitting the sequence of OPDM symbols,- inserting pilots for the three antennae

collectively in groups of pilots each group containing a pilot for each antenna, the groups scattered in time and frequency.

34. The method of claim 33, wherein each group

comprises one sub-carrier by three time intervals.

35. The method of claim 33 wherein each group

comprises one time interval by three sub-carriers.

36. The method of claim 33 wherein each group

comprises a first and a second pilot on a first sub-carrier over two time intervals and a third pilot on an adjacent sub-carrier located in the same time interval as one of the first and second OPDM symbols.

37. The method of claim 33 wherein each group

comprises, in a one sub-carrier by four time intervals arrangement or a one time interval by four sub-carriers arrangement, one pilots for each antenna in three of the four time intervale or three of the four sub-carriers, respectively,

38. A three transmit antenna transmitter for

performing the method of one of claims 13 to 26 and 33-36.

39. A device for receiving and decoding the

transmitted first and second Alamouti matrices of the methods of claim 13 or claim 14 ,

40. A method for transmitting on an even number of transmit antennas comprising:

pre-coding information bits to generate 2N transmit symbols;

encoding each pair of transmit symbols into a respective one of N Alamouti matrices;

transmitting the N Alamouti matrices on 2N antennae over 2Kf time intervals or 2N frequencies by:

transmitting each Alamouti matrix on two antennas and a respective two of the 2N time intervals or a

respective two of the 2N frequencies;

wherein the pre-coding and encoding are such that all of the information bits are represented in what is transmitted from each antenna.

41. A method for transmitting on an odd number of transmit antennas comprising:

pre-αoding information bits to generate 2N transmit symbols ;

encoding the 2N transmit symbols using a space time/frequency block code in which each transmit symbol appears an equal number of times and in such a manner that each of the transmit antennas is utilised equally;

transmitting the space time/frequency block code over the transmit antennas,- wherein the pre-coding and encoding are such that all of the information bits are represented, in what is transmitted from each transmit antenna.