A Performance Study of Massive MIMO Heterogeneous Networks with Ricean/Rayleigh Fading

Abstract

Massive multiple-input and multiple-out (massive MIMO) systems and heterogeneous networks (HetNet) are envisioned to meet the new performance objectives of evolving networks. Now, the main challenge of massive MIMO with HetNet in two-tier networks is how to alleviate interference generated by the randomly deployed femtocells to the macro cells. In this paper, we investigate massive MIMO with HetNet, where the intended macro base station (MBS) transmission follows Ricean fading and interfering femto BS transmissions follow Rayleigh fading. Then, by exploiting matrix and stochastic geometric tools, we derive tight approximations for the intended signal power and aggregated interfering power signal. And derive the signal-to-interference (SIR) with the convolution of the two power signals. Then, we obtain the performance objectives: coverage and outage probabilities, and area spectral efficiency. Further, to reduce the cell edge effects and improve the SIR, we study the role of massive MIMO beamforming coordination with the high-powered MBSs. Thus, we develop maxi-min optimization to control the MBS transmit power. Numerical results show that the coverage and outage performance converge for different user locations, pathloss and Ricean factor. The monotonic increase in Ricean factor improves the SIR of a user located within coverage region. Optimal values of macro BS antenna and transmit power guarantee rate-fairness between the coordinating MBSs, and avoid strong Ricean channel correlation. Also, the performance gain is dependent on the user location, but independent of the cell size.

Multiple-Symbol Non-Coherent Detection for Differential QAM Modulation in Uplink Massive MIMO Systems

“…Figure 2 illustrates the simulation results of the proposed 16-DQAM scheme with different lengths of estimated signal vector L = 2 and 3, as well as the 16-DQAM schemes in [12,13] where the number of BS antennas are M = 128 and 500, and the coherent length T = 7. Since the authors of [12] did not show the detector when M is finite, we suppose that the 16-DQAM scheme in [12] uses the generalized detector as in [13], Equation (6), and the corresponding non-coherent distance in [13]. As previously shown in [12,13], the 16-DQAM scheme of [12] shows an error floor when M is not very large.…”

“…Massive multiple-input multiple-output (MIMO) transmission technique has gained a lot of attention in recent decades [1][2][3][4][5][6][7][8][9][10][11][12][13], since it can achieve significant improvement in terms of the energy and spectral efficiency while using simple signal processing [1][2][3][4]. Massive MIMO systems prefer operating in the time division duplex (TDD) mode in which users must synchronously send mutually orthogonal pilot signals to the corresponding base station (BS) so that the BS can estimate the channels.…”

“…Massive MIMO systems prefer operating in the time division duplex (TDD) mode in which users must synchronously send mutually orthogonal pilot signals to the corresponding base station (BS) so that the BS can estimate the channels. This method uses the estimated channels to perform signal processing [5][6][7][8][9][10][11][12][13], so that pilot signals account for a significant part of the total coherent interval, which decreases the spectral efficiency. In addition, when the number of users is large, the orthogonal pilot set has to be reused in every cell, which leads to pilot contamination problems; this is considered as a performance bottleneck in massive MIMO systems.…”

Dual-Hop Cooperative Relaying with Beamforming Under Adaptive Transmission in κ–μ Shadowed Fading Environments

“…Mainly, there are two dual-hop relaying techniques, which are categorized as decode-and-forward (DF) and amplify-and-forward (AF) relays. In a DF relaying method, the received signals are first decoded and re-encoded, then forwarded to the destination or end-user, whereas, in an AF relaying method, the received signals from the transmitter or source node are amplified first, then forwarded to the destination [5][6][7][8].…”

Worst Cell Based Pilot Allocation in Massive MIMO Systems

“…Massive multiple-input multiple-output (MIMO) techniques have been broadly investigated over the last two decades to keep up with the exponential increases in mobile data traffic in future 5G wireless systems [1][2][3][4][5][6], whereby a base station (BS) endowed with a very huge number of antennas serving many users concurrently. Massive MIMO has been considered as one of the main techniques which provide reliable and green communication [7,8], especially in smart cities networks.…”