# What is the advantages of BPSK+OFDM over usual BPSK (with no OFDM Modulation)?

The other days I read a useful article (on BER v.s. Eb/N0 curve of ofdm) whose link is as bellow. While watching the plot inside, a question was arisen in my mind. I wonder if the BER v.s. Eb/N0 curve of BPSK alone (without using OFDM) and one using OFDM could be the same in both AWGN and fading (flat and selective) channels? If so, what’s the use of applying OFDM to BPSK alone (expect the simpler equalizer for OFDM case)?

http://www.dsplog.com/2008/08/26/ofdm-rayleigh-channel-ber-bpsk/

Best Regards

• The BER should be the same. OFDM just maps a single high-rate modulated stream into multiple parallel lower-rate streams, so you should expect the same bit-error performance characteristics (note that for white noise, $\frac{E_b}{N_0}$ will not change between the two cases). You hit on the primary benefit: simple equalization. In addition, you gain flexibility in allocating subcarriers as needed, using different modulation schemes on different subcarriers, etc. May 12 '14 at 12:32
• @JasonR In the frequency selective fading case, if you don't use ofdm and instead send BPSK itself won't the error increase. The equaliser gets extremely complicated for the frequency selective fading case and due to that there could be a degradation in performance(i.e.increase in BER). Correct me if I am wrong. May 12 '14 at 12:57
• BPSK + OFDM is no improvement of BPSK on both rayleigh channel and AWGN but ofdm + QAM 16 is an improvemnet on QAM 16 alone on both channels, can someone please explain this??
– user10733
Aug 7 '14 at 16:30
• Welcome to dsp.se! This seems to be a question. Please post it as such (and add a reference to that statement when you do so)
– Deve
Aug 7 '14 at 17:58