Patent ID: 7433423

Claim:
A method of differential unitary space-time modulation by encoding messages to transmit through n T transmit antennas in a communication system wherein the signals are transmitted between n T transmit antennas and n R receive antennas wherein n T is an integer no less than 2, and n R is an integer no less than 1, comprising the step of: encoding a message into multiple trellis code which maximizes a product of minimum Euclidian distances between signals having minimum Hamming distance, wherein a relation among a transmitted signal C from a jth transmit antenna (j=1, 2, . . . , n T ) at time t (t=1, 2, . . . , T), the received signal Y at the ith receive antenna for the transmitted signal C, channel matrix H, and noise matrix N is given by Formula 2: Y =√{square root over (ρ)} CH+N [Formula 2] wherein, Y={Y t i } is the n T×n T received signal matrix, C={C tj } is the n T×n R transmitted signal matrix, H={h j i } is the n T ×n T channel matrix, N={n t i } is the n T×n R noise matrix, ρ is the SNR of the receive antenna, and T is the symbolic period, wherein the symbolic period T is n T ; a unitarty space time constellation V for V k , which is an n T ×n T data matrix at the kth block among T symbolic period, is V ≡ { V ⁡ ( l ) ❘ V ⁡ ( l ) = V ⁡ ( l ) l , l = 0 , 1 , 2 , … ⁢ , L - 1 } wherein , ⁢ V ⁡ ( 1 ) = diag ⁡ ( ⅇ j ⁢ 2 ⁢ π ⁢ ⁢ u 1 L , ⅇ j ⁢ 2 ⁢ π ⁢ ⁢ u 2 L , … ⁢ , ⅇ j ⁢ 2 ⁢ π ⁢ ⁢ u n T L ) , and L is the cardinality of V; and the n T ×n T transmitted signal matrix C k at the kth block, and the received signal matrix Y k for the C k are given by Formulas 4 and 5, respectively: C k =V k C k−1 , C 0 =I [Formula 4] Y k =√{square root over (ρ)}C k H+N k wherein, [Formula 5] wherein, N k is the noise matrix at the kth block, and H is the channel matrix which is constant during two consecutive blocks; and wherein pair-wise error probability (PEP) which is the probability of incorrectly decoding V to U when the encoded signal matrix sequence V={V 0 , V 1 , . . . } is transmitted, is given by Formula 9, and in order to minimize the PEP of the Formula (9), the message is encoded to maximize the minimum block Hamming distance δ min defined as Formula 14, and the minimum product of squared determinant distance ((ΠD 2 ) min ) defined as Formula 10, wherein: p ⁡ ( V → U ) ≤ ( ρ 8 ) - n T ⁢ n R ⁢ δ ⁢ ∏ k ∈ η ⁢ ⁢  det ⁡ ( V k - U k )  - 2 ⁢ n R ⁢ [ Formula ⁢ ⁢ 9 ] ( ∏ ⁢ D 2 ) min ≡ min U ⁢ ( ∏ k ∈ η ⁡ ( V , U ) ⁢ ⁢ D 2 ⁡ ( V k , U k ) ) = min U ⁢ ( ∏ k ∈ η ⁡ ( V , U ) ⁢  det ⁡ ( V k - U k )  2 n T ) [ Formula ⁢ ⁢ 10 ] δ min ≡ min U ⁢  η ⁡ ( V , U )  [ Formula ⁢ ⁢ 14 ] wherein, δ is the size of η(V,U) and represents the block Hamming distance between V and U, and η(V,U) is the set of k such that V k ≠U k .