Joint Impact of Limited Fronthaul and Pilot Length on Payload Data Rate of Cell-Free Massive MIMO

This work studies the uplink of a cell-free massive MIMO (mMIMO) system with finite-capacity fronthaul links. In particular, the impacts of fronthaul capacity and pilot length on the channel estimation quality as well as the payload data transmission rates are analyzed. To this end, the powers of the quantization noise signals, the estimated channel coefficients and the estimation errors are calculated first. Then, it is followed by the derivation of the achievable payload data transmission rates under two combining schemes: optimal minimum mean squared error (MMSE) and low-complexity maximum-ratio combining (MRC) schemes. Numerical results show how the average sum-rate of the system is affected by the system parameters such as the fronthaul capacity, uplink signal-to-noise ratio (SNR), and the pilot length.