I'm working on a wireless communication system using QPSK modulation, and I'm struggling with high bit error rates in noisy environments. What practical steps can I take to improve performance without exceeding power constraints?

For my university project, I'm implementing a QPSK-based data link over a 2.4 GHz frequency band. I've already tried increasing transmit power and adjusting antenna positions, but the bit error rate remains too high for reliable communication. The system has limited battery life, so I need solutions that are power-efficient.