10 10 TCM QPSK te 10 TCM Zero error range SNR[dB] Figure 5.1.4:Bit error probability of Quadrature Phase-Shift Keying (QPSK)and selected 8-PSK coded modulation (TCM).rellis-tubo coded (TTCM).and boc turbo coded(BTC)systems as a 5.1.1两种基本实现方法 Similar to the case of binary codes,we introduce interdependences between consecutive signal points in order to increas e the distance b etween the clo stpa nces of sign points.A perspective from signal-space coding may provide more insight into codec modulation schemes.In order to obtain large coding gain,the codes should be designed in a subspace of signal space with high dimensionality,where a larger minimum distance in relation to signal power can be obtained.The dimensionality 2BTo can be increased for fixed bandwidth B by in g the time interval To,making it multiple symbol intervals. For moderate coding gain at moderate complexity, Iwo ba ways to generate modulation (or signal-space)codes in conjunction with passband QAM modulation are as follows: ■直接来自于几何考虑：A sequence of N/2two-dimensional transmitted symbols can be considered as a single point in an N-dimensional constellation.Each element of the constellation alphabet(called a codeword)isa vector inN(or).Aset of K input bits are used to select one of2 codewords in the multidimensional constellation.A typical example of the multidimensional constellation is the lattice code.它类似于二进制编码 5.5 5-5 Figure 5.1.4: Bit error probability of Quadrature Phase-Shift Keying (QPSK) and selected 8-PSK trellis-coded modulation (TCM), trellis-turbo coded (TTCM), and block turbo coded (BTC) systems as a function of the normalized signal-to-noise ratio. 5.1.1 两种基本实现方法 Similar to the case of binary codes, we introduce interdependences between consecutive signal points in order to increase the distance between the closest pair of sequences of signal points. A perspective from signal-space coding may provide more insight into coded modulation schemes. In order to obtain large coding gain, the codes should be designed in a subspace of signal space with high dimensionality, where a larger minimum distance in relation to signal power can be obtained. The dimensionality 2BT0 can be increased for fixed bandwidth B by increasing the time interval T0, making it multiple symbol intervals. For moderate coding gain at moderate complexity, Two basic ways to generate modulation (or signal-space) codes in conjunction with passband QAM modulation are as follows: „ 直接来自于几何考虑：A sequence of N/2 two-dimensional transmitted symbols can be considered as a single point in an N-dimensional constellation. Each element of the constellation alphabet (called a codeword) is a vector in RN (or CN/2). A set of K input bits are used to select one of 2K codewords in the multidimensional constellation. A typical example of the multidimensional constellation is the lattice code. 它类似于二进制编码