Reducing OFDM-Based Radio Network Energy Consumption by Frame Format Optimization
Channel time dispersion causes inter-symbol interference (ISI) which is mitigated by the Orthogonal Frequency Division Multiplexing (OFDM) symbol cyclic prefix (CP). However, CP is an overhead which reduces spectral efficiency and increases energy per delivered bit. In Long Term Evolution (LTE), the widely deployed normal CP corresponds to a fixed overhead of about 7% (4.69 μs), which is conservative for many practical environments and is equivalent to path-length variations on the order of 1.4 km. This paper address CP sizing from an energy-efficiency viewpoint for OFDM-based 4G/5G radio networks. We combine an analytical model based on delay spread statistics with link-level simulations to determine a reduced CP that remains effective for ISI mitigation across indoor-to-urban scenarios. Optimal CP intervals are derived for the LTE M-ary Quadrature Amplitude Modulation formats (4-QAM, 16-QAM, and 64-QAM) and validated using standard delay-dispersive mobile radio channels. Results indicate that CP can be reduced by 70–95% relative to the LTE normal CP in typical deployments, yielding measurable net-throughput improvements and energy savings without compromising error-rate targets, supporting greener wireless communications.