Current Journal of Applied Science and Technology

The exponential growth of mobile data traffic requires higher spectral efficiency (SE) and lower hardware costs in 5G networks and beyond. Spatial Modulation (SM) activates a single transmit antenna per channel use, which removes inter-channel interference (ICI), requires a single RF chain and conveys log2(Mt) additional bits through the index of the active antenna. This paper evaluates SM combined with OFDM (SM-OFDM) over frequency-selective multipath channels using MATLAB Monte Carlo simulation (128-point FFT, zero-forcing/MRC receiver, no channel coding). The bit error rate (BER) and SE are assessed as functions of the M-QAM/M-PSK modulation order (up to M = 128), the numbers of transmit and receive antennas (Mt up to 128, Mr up to 64) and the channel-estimation error Δh (0 to 0.3). The principal findings are as follows: (i) 16-QAM reaches BER = 10⁻⁴ at about 30 dB, higher orders require a few additional dB, and QAM outperforms PSK by 1–2 dB; (ii) 16-PSK and 16-QAM differ by less than 1 dB; (iii) increasing Mt degrades the BER but raises the SE (for 4-PSK at 20 dB, from about 6 bit/s/Hz with Mt = 4 to about 9.5 bit/s/Hz with Mt = 64); (iv) adding receive antennas improves reliability; (v) channel-estimation errors produce an error floor, so accurate CSI is essential. Unlike earlier SM-OFDM studies limited to narrowband channels or to a single parameter, this work analyses modulation order, antenna numbers and CSI error jointly. The conclusions are simulation-based and should be validated with measured channels, coded transmission and a quantitative energy-efficiency assessment.