Joint Power Allocation and User Association Optimization for Massive MIMO Systems
2016 (English)In: IEEE Transactions on Wireless Communications, ISSN 1536-1276, E-ISSN 1558-2248, Vol. 15, no 9, 6384-6399 p.Article in journal (Refereed) Published
This paper investigates the joint power allocationand user association problem in multi-cell Massive MIMO(multiple-input multiple-output) downlink (DL) systems. Thetarget is to minimize the total transmit power consumptionwhen each user is served by an optimized subset of the basestations (BSs), using non-coherent joint transmission. We ﬁrstderive a lower bound on the ergodic spectral efﬁciency (SE),which is applicable for any channel distribution and precodingscheme. Closed-form expressions are obtained for Rayleigh fadingchannels with either maximum ratio transmission (MRT) or zeroforcing (ZF) precoding. From these bounds, we further formulatethe DL power minimization problems with ﬁxed SE constraintsfor the users. These problems are proved to be solvable aslinear programs, giving the optimal power allocation and BS-user association with low complexity. Furthermore, we formulatea max-min fairness problem which maximizes the worst SEamong the users, and we show that it can be solved as aquasi-linear program. Simulations manifest that the proposedmethods provide good SE for the users using less transmit powerthan in small-scale systems and the optimal user associationcan effectively balance the load between BSs when needed.Even though our framework allows the joint transmission frommultiple BSs, there is an overwhelming probability that only oneBS is associated with each user at the optimal solution.
Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2016. Vol. 15, no 9, 6384-6399 p.
Massive MIMO, user association, power allocation, load balancing, linear program
IdentifiersURN: urn:nbn:se:liu:diva-131129DOI: 10.1109/TWC.2016.2583436OAI: oai:DiVA.org:liu-131129DiVA: diva2:968009
FundereLLIIT - The Linköping‐Lund Initiative on IT and Mobile Communications