GSM Physical Layer Channel Encoding

In the GSM physical layer, a series of processing steps are required including channel encoding, modulation, channel simulation, synchronization search, channel estimation, equalization and demodulation, and channel decoding. These steps are crucial for ensuring communication reliability and accurate data transmission. Channel encoding enhances interference resistance and error correction capability through algorithms like convolutional coding (e.g., using polynomials [5, 7] for rate 1/2 coding). Modulation converts digital signals to analog waveforms for wireless transmission, typically implemented using Gaussian Minimum Shift Keying (GMSK) with a BT product of 0.3. Channel simulation emulates real wireless environments through Rayleigh fading models and additive white Gaussian noise (AWGN) injection for system performance testing. Synchronization search employs correlation algorithms (e.g., cross-correlation with training sequences) to achieve precise time and frequency alignment. Channel estimation techniques like Least Squares (LS) or Minimum Mean Square Error (MMSE) characterize channel fading and distortion. Equalization and demodulation utilize Viterbi equalizers to mitigate intersymbol interference. Finally, channel decoding applies Viterbi algorithm-based decoders to recover original data from encoded signals for subsequent processing and analysis.