Exploiting Spatial Correlation for Pilot Reuse in Single-Cell mMTC

As a key enabler for massive machine-type communications (mMTC), spatial multiplexing relies on massive multiple-input multiple-output (mMIMO) technology to serve the massive number of user equipments (UEs). To exploit spatial multiplexing, accurate channel estimation through pilot signals is needed. In mMTC systems, it is impractical to allocate a unique orthogonal pilot sequence to each UE as it would require too long pilot sequences, degrading the spectral efficiency. This work addresses the design of channel features from correlated fading channels to assist the pilot assignment in multi-sector mMTC systems under pilot reuse of orthogonal sequences. In order to reduce pilot collisions and to enable pilot reuse, we propose to extract features from the channel covariance matrices that reflect the level of orthogonality between the UEs channels. Two features are investigated: covariance matrix distance (CMD) feature and CMD-aided channel charting (CC) feature. In terms of symbol error rate and achievable rate, the CC-based feature shows superior performance than the CMD-based feature and baseline pilot assignment algorithms.

Ribeiro Lucas, Leinonen Markus, Al-Tous Hanan, Tirkkonen Olav, Juntti Markku

A4 Article in conference proceedings

32nd IEEE Annual International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC 2021

L. Ribeiro, M. Leinonen, H. Al-Tous, O. Tirkkonen and M. Juntti, "Exploiting Spatial Correlation for Pilot Reuse in Single-Cell mMTC," 2021 IEEE 32nd Annual International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2021, pp. 654-659, doi: 10.1109/PIMRC50174.2021.9569562

http://dx.doi.org/10.1109/PIMRC50174.2021.9569562 http://urn.fi/urn:nbn:fi-fe2022012710501