Bit Error Rate Performance in Additive White Gaussian Noise Channel

Following the user's requirements, I will expand the text while preserving core concepts and integrating new technical content. In communication systems, QPSK (Quadrature Phase Shift Keying) modulation is a widely used technique that enables simultaneous transmission of two bits per symbol. The implementation typically involves mapping bit pairs to four phase states (0°, 90°, 180°, 270°) using constellation mapping algorithms. Code implementation would include symbol mapping, pulse shaping, and carrier modulation functions. When comparing DQPSK (Differential QPSK) and standard QPSK performance over Additive White Gaussian Noise (AWGN) channels, significant differences emerge in bit error rate (BER) characteristics. DQPSK employs differential encoding where information is carried in phase differences between consecutive symbols, eliminating the need for absolute phase reference. This implementation requires differential encoding/decoding algorithms that minimize phase transitions, thereby reducing error propagation and improving BER performance in noisy environments. The BER comparison can be simulated using MATLAB's comm.DQPSKModulator and comm.QPSKModulator system objects with AWGN channel models. Beyond modulation techniques, OFDM (Orthogonal Frequency Division Multiplexing) systems represent another critical communication technology. OFDM implementation involves dividing high-rate data streams into multiple parallel low-rate streams modulated onto orthogonal subcarriers. Key implementation components include IFFT/FFT operations for modulation/demodulation, cyclic prefix insertion for multipath mitigation, and pilot symbol insertion for channel estimation. This multicarrier approach effectively combats multipath fading and frequency-selective fading through frequency diversity, significantly enhancing system interference resistance and transmission rates. Simulation typically involves configuring OFDM parameters like FFT size, cyclic prefix length, and subcarrier spacing using communication toolboxes. These expanded technical descriptions with implementation insights should meet your requirements for comprehensive communication system analysis.