On orthogonal and superimposed pilot schemes in massive MIMO NOMA systems

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

37 Scopus Citations
View graph of relations


  • Junjie Ma
  • Chulong Liang
  • Chongbin Xu
  • Ping Li

Related Research Unit(s)


Original languageEnglish
Pages (from-to)2696-2707
Journal / PublicationIEEE Journal on Selected Areas in Communications
Issue number12
Online published11 Jul 2017
Publication statusPublished - Dec 2017


This paper is concerned with pilot transmission schemes in a large antenna system with non-orthogonal multiple-access (NOMA). We investigate two pilot structures-orthogonal pilot (OP) and superimposed pilot (SP). In OP, pilots occupy dedicated time (or frequency) slots, while in SP, pilots are superimposed with data. We study an iterative data-aided channel estimation (IDACE) receiver, where partially decoded data are used to refine channel estimation. We analyze the achievable rates for systems with IDACE receivers for both OP and SP. We show that the optimal portion of pilot power tends to zero for SP with Gaussian signaling. This result is consistent with existing findings obtained via the replica method in statistical physics. The latter involves multiple codes, which is convenient for theoretical analysis but difficult to implement. As a comparison, IDACE is potentially implementable in practice. We demonstrate that, with code optimization, SP can outperform OP in a high mobility environment with a large number of users. We provide numerical examples to verify our analysis.

Research Area(s)

  • Achievable rate, Iterative data-aided channel estimation, Massive multiple-input multiple-output (MIMO) system, Non-orthogonal multiple-access (NOMA), Orthogonal pilot, Superimposed pilot