Joint Processing of Pilot and Data for Massive MIMO Systems in Ricean Fading Channels

Besides the pilot symbols, the received data signals also contain some extra channel state information (CSI), which can be exploited to further improve the channel estimation accuracy. Considering a multi-cell multi-user massive multiple input multiple output (MIMO) with Ricean fading, the spectral efficiency for joint processing of the pilot and data strategy is investigated. Through the mutual information analysis of the multi-cell multi-user massive MIMO system, the intractable expression for the ergodic spectral efficiency is lower bounded and decomposed into three terms, where the explicit physical meanings of them are discussed in detail. Facilitated by the decomposing operation, an asymptotic closed-form expression of the spectral efficiency is obtained, and it is proven to be accurate. Comparing with separate processing, numerical results show that the joint processing outperforms the separate processing in spectral efficiency since the additional CSI is captured. The performance advantage for joint processing over separate processing becomes obvious as the coherence block duration of channels (T) increases. For a long enough T, joint processing eventually approaches the case with perfect CSI in terms of spectral efficiency. In addition, the inter-cell interference heavily reduces the system performance of joint processing when T is relatively small.