RxMER provides an in-channel received Modulation Error Ratio (MER). RxMER is defined as an estimate, provided by the demodulator, of the ratio: (average constellation energy with equally likely symbols) / (average squared magnitude of error vector)

RxMER is measured just prior to FEC (trellis/Reed-Solomon) decoding. RxMER includes the effects of the HFC channel as well as implementation effects of the modulator and demodulator. Error vector estimation may vary among demodulator implementations. The CMTS RxMER is averaged over a given number of bursts at the burst receiver, which may correspond to transmissions from multiple users. In the case of S-CDMA mode, RxMER is measured on the de-spread signal.