BICM Communication Process with 8PSK Modulation

Analysis of BICM System Communication Process (8PSK Modulation Scheme)

In wireless communication systems, the Bit-Interleaved Coded Modulation (BICM) architecture is widely adopted due to its excellent interference resistance performance. This article focuses on the implementation process of BICM systems employing 8PSK modulation.

Transmitter Processing Flow: The system first performs channel coding on the input bit stream, typically using coding schemes such as convolutional codes or LDPC codes. The coded bit stream passes through a carefully designed bit interleaver - this critical step ensures burst errors can be distributed and processed separately during decoding. Subsequently, 8PSK constellation mapping is performed, where every 3 bits are mapped to 8 phase points on the constellation diagram, forming modulation symbols with 8 possible phases. In code implementation, this mapping can be achieved using lookup tables or mathematical functions like: symbol = exp(1j*2*pi*(bin2dec(bit_triplet)/8)).

Constellation Diagram Characteristics: The 8PSK constellation displays 8 points uniformly distributed on the unit circle with adjacent constellation points separated by 45 degrees phase difference. This modulation scheme transmits more information than QPSK under the same bandwidth but requires higher SNR to maintain the same bit error rate. The constellation generation algorithm typically involves creating complex points at angles: [0:45:315]*pi/180 radians.

Receiver Processing Mechanism: The demodulation process begins with symbol synchronization and carrier recovery, followed by generating soft decision information by calculating the Euclidean distance between received signals and each constellation point. These soft informations are deinterleaved and fed into the channel decoder, which performs probabilistic decoding using the soft information to ultimately recover the original message. The Euclidean distance calculation can be implemented using vector operations: distances = abs(received_signal - constellation_points).^2.

System Advantage Analysis: The 8PSK modulated BICM system achieves an excellent balance between spectral efficiency and power efficiency. The introduction of the interleaver makes the system robust against channel burst errors, while soft information demodulation fully utilizes channel state information, significantly improving overall system performance. The interleaver implementation typically uses matrix-based permutation algorithms like block interleaving or convolutional interleaving patterns.