The Effect of Diversity Combining on ISI in Massive MIMO

Abstract

We analyze the resiliency of Massive Multiple-Input Multiple-Output (M-MIMO) systems to Inter-Symbol Interference (ISI) when diversity combining techniques are used at the Base Station (BS). We show that Maximum Ratio Combining (MRC) alone can equalize an ISI channel as the number of antennas grows unbounded. Additional constraints on the nature of the channel must be postulated depending on whether the information of the Angle-of-Arrival (AoA) is exploited at the receiver or not. Interestingly, the simpler Equal Gain Combiner (EGC) receiver is also able to equalize the channel as the number of antennas grows but, in this case, at least one channel path must be Ricean faded.These findings are confirmed via simulation on WSSUS channels and channels generated with a ray tracing engine simulating a real BS deployment in downtown Hong Kong and Shanghai. Finally, the observed scaling law indicates that normalized ISI power decreases N -fold for every N -fold increase in the number of antennas at the BS.

Fourier-Optics Based Opto-Electronic Architectures for Simultaneous Multi-Band, Multi-Beam, and Wideband Transmit and Receive Phased Arrays

“…x k (10) incident on the pick-up fiber array. Under narrowband approximation, harmonic time dependence 2 exp( ) j t ω is understood in (9), where ω2 is the frequency of the clone-laser output, so that:…”

“…In the ultimate case of an infinite number of radiating elements, the aperture approaches a spatial continuum and the transmitted waveform, properly compensated for the propagation channel characteristics via precoding, is conceptually analogous to a holographic profile-see [5] where the concept of "Holographic Massive MIMO" was first introduced. Additionally, large arrays mitigate many impairments such as hardware imperfections, phase noise, nonlinearities, quantization errors, noise amplification, intercarrier interference, and also inter-symbol interference [6]- [9]. To take advantage of the potential benefits offered by large arrays, architectures must support a large number of antenna elements and be capable of wideband beamforming with simultaneous multi-beam and multi-band operation, all of which are features in high demand among service providers.…”

Ergodic spectral efficiency of massive MIMO with correlated Rician channel and MRC detection based on LS and MMSE channel estimation

“…Here, orthogonal frequency division multiplexing (OFDM) is used such that no inter‐symbol interferences (ISI) and inter‐carrier interferences (ICI) exist. However, some few works have considered ISI [31, 32] or ICI [33] in massive MIMO systems. It is known that SE decreases in the presence of either ISI or ICI.…”

“…It is known that SE decreases in the presence of either ISI or ICI. However, it is shown in [31] that using an MRC detector reduces ISI in massive MIMO systems itself. Also, parallel quadrature spatial modulation has been proposed in [32] to compensate ISI.…”

Análise de Desempenho Assintótica das Técnicas EGC e SC com Múltiplos Ramos sob Desvanecimento Generalizado

“…longo do percurso, fenômenos como reflexão, difração e espalhamento acontecem a todo momento, causando em última instância alterações aleatórias de amplitude e fase no sinal recebido, um efeito conhecido como desvanecimento [1]. A fim de mitigar o impacto do desvanecimento e de seus efeitos nocivos sobre o desempenho dos sistemas, técnicas de diversidade como combinação por ganho igual (do inglês, equal-gain combining -EGC), combinação por seleção (do inglês, selection combining -SC) e combinação por razão máxima (do inglês, maximal-ratio combining -MRC) têm sido empregadas amplamente em diversos contextos, como em sistemas de quinta geração (5G) e suas tecnologias [2]- [4]. Ao combinar múltiplas réplicas de sinal recebidas, essas técnicas são capazes de oferecer na saída do receptor um sinal resultante de melhor qualidade, melhorando assim o desempenho do sistema e a qualidade de serviço [5].…”