Performance Comparison of BICM, 8PSK, and Coded Modulation Techniques in AWGN Channels

In wireless communication systems, Bit-Interleaved Coded Modulation (BICM), 8-Phase Shift Keying (8PSK), and traditional coded modulation techniques are common signal modulation methods, each exhibiting distinct advantages and disadvantages in Additive White Gaussian Noise (AWGN) channels.

### BICM (Bit-Interleaved Coded Modulation) BICM is a technique that combines coding and modulation, where a bit interleaver distributes encoded bits across different modulation symbols to enhance resistance to fading and noise. In implementation, a typical BICM system involves forward error correction encoding (e.g., convolutional codes) followed by bit-wise interleaving before modulation mapping. Under AWGN channels, BICM's advantage lies in its strong error correction capability, particularly at low Signal-to-Noise Ratio (SNR) conditions. The bit-level interleaving effectively mitigates burst error effects, which can be implemented using block interleavers or convolutional interleavers in practical systems. Key algorithms often involve soft-decision decoding with iterative demapping for optimal performance.

### 8PSK (8-Phase Shift Keying) 8PSK is a high-order modulation scheme where each symbol carries 3 bits of information, providing higher spectral efficiency compared to QPSK (4PSK). Implementation-wise, 8PSK modulation maps binary triplets to eight equally spaced phase points on the constellation diagram (0°, 45°, 90°, etc.). However, in AWGN channels, 8PSK demonstrates greater sensitivity to noise, with Bit Error Rate (BER) deteriorating rapidly as SNR decreases. The demodulation algorithm typically employs maximum likelihood detection with phase recovery mechanisms. This makes 8PSK suitable for high-SNR environments while performing poorly under low SNR conditions. Code implementation often requires precise carrier synchronization and phase tracking loops.

### Traditional Coded Modulation Traditional coded modulation techniques like Trellis Coded Modulation (TCM) employ joint symbol-level coding and modulation design, demonstrating stable performance in AWGN channels. Implementation involves set partitioning and convolutional coding integrated with modulation mapping, creating expanded constellation sets with built-in error protection. Compared to BICM, TCM may show slight advantages with low-order modulations but suffers from higher complexity with high-order modulations like 8PSK. The Viterbi algorithm is typically used for decoding with path metrics calculated based on Euclidean distances. Its resistance to burst noise is generally inferior to BICM due to the lack of bit-level interleaving.

### Performance Comparison Under AWGN channels, the performance comparison of these three technologies can be summarized as follows: BICM: Performs best at low SNR, suitable for noisy environments. Implementation advantage includes flexibility in choosing separate coding and modulation schemes. 8PSK: Provides higher data rates at high SNR but is noise-sensitive, making it appropriate for channels with good quality. Requires careful SNR threshold management in system design. Traditional coded modulation (e.g., TCM): Offers stable performance at medium-to-low SNR but with higher complexity. Less flexible than BICM in modern adaptive systems.

Overall, BICM demonstrates better robustness in AWGN channels, while 8PSK is more suitable for high-speed transmission requirements under high-SNR conditions. Traditional coded modulation shows balanced performance within certain ranges, but modern communication systems tend to adopt BICM for enhanced overall performance, particularly in adaptive modulation and coding schemes where the separation of coding and modulation allows for more flexible system optimization.