Spectral and Energy Efficiency of Superimposed Pilots in Uplink Massive MIMO
2018 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 17, no 11, p. 7099-7115Article in journal (Refereed) Published
Abstract [en]
Next-generation wireless networks aim at providing substantial improvements in spectral efficiency (SE) and energy efficiency (EE). Massive MIMO has been proved to be a viable technology to achieve these goals by spatially multiplexing several users using many base station (BS) antennas. A potential limitation of massive MIMO in multicell systems is pilot contamination, which arises in the channel estimation process from the interference caused by reusing pilots in neighboring cells. A standard method to reduce pilot contamination, known as regular pilot (RP), is to adjust the length of pilot sequences while transmitting data and pilot symbols disjointly. An alternative method, called superimposed pilot (SP), sends a superposition of pilot and data symbols. This allows use of longer pilots which, in turn, reduces pilot contamination. We consider the uplink of a multicell massive MIMO network, with i.i.d. Rayleigh fading channels, using maximum ratio combining and compare RP and SP in terms of SE and EE. To this end, we derive rigorous closed-form achievable rates with SP under a practical random BS deployment. We prove that the reduction of pilot contamination with SP is outweighed by the additional coherent and non-coherent interference. Numerical results show that when both methods are optimized, RP achieves comparable SE and EE to SP in practical scenarios.
Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE) , 2018. Vol. 17, no 11, p. 7099-7115
Keywords [en]
Massive MIMO, spatial multiplexing, spectral efficiency (SE), energy efficiency (EE), superimposed pilots (SP), channel estimation, pilot contamination, achievable rates, stochastic geometry
National Category
Signal Processing Telecommunications
Identifiers
URN: urn:nbn:se:kth:diva-295870DOI: 10.1109/TWC.2018.2860939ISI: 000449978700001Scopus ID: 2-s2.0-85051383168OAI: oai:DiVA.org:kth-295870DiVA, id: diva2:1663996
Conference
36th IEEE Global Communications Conference (GLOBECOM), DEC 04-08, 2017, Singapore, SINGAPORE
Note
QC 20220614
2022-06-032022-06-032022-06-25Bibliographically approved