18 research outputs found
Multipair Massive MIMO Relaying Systems with One-Bit ADCs and DACs
This paper considers a multipair amplify-and-forward massive MIMO relaying
system with one-bit ADCs and one-bit DACs at the relay. The channel state
information is estimated via pilot training, and then utilized by the relay to
perform simple maximum-ratio combining/maximum-ratio transmission processing.
Leveraging on the Bussgang decomposition, an exact achievable rate is derived
for the system with correlated quantization noise. Based on this, a closed-form
asymptotic approximation for the achievable rate is presented, thereby enabling
efficient evaluation of the impact of key parameters on the system performance.
Furthermore, power scaling laws are characterized to study the potential energy
efficiency associated with deploying massive one-bit antenna arrays at the
relay. In addition, a power allocation strategy is designed to compensate for
the rate degradation caused by the coarse quantization. Our results suggest
that the quality of the channel estimates depends on the specific orthogonal
pilot sequences that are used, contrary to unquantized systems where any set of
orthogonal pilot sequences gives the same result. Moreover, the sum rate gap
between the double-quantized relay system and an ideal non-quantized system is
a moderate factor of in the low power regime.Comment: 14 pages, 10 figures, submitted to IEEE Trans. Signal Processin
Multipair Two-Way DF Relaying with Cell-Free Massive MIMO
We consider a two-way half-duplex decode-and-forward (DF) relaying system
with multiple pairs of single-antenna users assisted by a cell-free (CF)
massive multiple-input multiple-output (mMIMO) architecture with
multiple-antenna access points (APs). Under the practical constraint of
imperfect channel state information (CSI), we derive the achievable sum
spectral efficiency (SE) for a finite number of APs with maximum ratio (MR)
linear processing for both reception and transmission in closed-form. Notably,
the proposed CF mMIMO relaying architecture, exploiting the spatial diversity,
and providing better coverage, outperforms the conventional collocated mMIMO
deployment. Moreover, we shed light on the power-scaling laws maintaining a
specific SE as the number of APs grows. A thorough examination of the interplay
between the transmit powers per pilot symbol and user/APs takes place, and
useful conclusions are extracted. Finally, differently to the common approach
for power control in CF mMIMO systems, we design a power allocation scheme
maximizing the sum SE.Comment: 15 pages, 8 figures, This work was accepted in IEEE Trans. Green
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version may no longer be accessibl
A new achievable sum DoF result in multi-user half-duplex relay networks
This is the author accepted manuscript. The final version is available from IEEE via the DOI in this recordThis paper investigates the achievable sum degrees of freedom (DoF) in a wireless single-antenna multi-user relay network, which consists of multiple sources, multiple destinations, and multiple layers of half-duplex relays in between. A cluster successive relaying (CSR) transmission scheme is applied to efficiently deliver information in this network. Different from existing works on the CSR scheme which normally divide each layer of relays into two alternatively activated equal-size clusters, we allow the clusters to contain different numbers of terminals in order to properly involve all available relays into the transmission process. Using the channel-extension based interference alignment technique, it is shown that the asymptotically achievable sum DoF can be larger than the previously known results and hence can serve as a new lower bound to the optimally achievable sum DoF in the considered relay network.National Natural Science Foundation of ChinaEuropean Union Horizon 2020European Union FP
Energy Efficient Massive MIMO and Beamforming for 5G Communications
Massive multiple-input multiple-output (MIMO) has been a key technique
in the next generation of wireless communications for its potential to achieve
higher capacity and data rates. However, the exponential growth of data
traffic has led to a significant increase in the power consumption and system
complexity. Therefore, we propose and study wireless technologies to improve the trade-off between system performance and power consumption of wireless communications.
This Thesis firstly proposes a strategy with partial channel state information
(CSI) acquisition to reduce the power consumption and hardware complexity of massive MIMO base stations. In this context, the employment of partial CSI is proposed in correlated communication channels with user mobility. By exploiting both the spatial correlation and temporal correlation of the channel, our analytical results demonstrate significant gains in the energy efficiency of the massive MIMO base station.
Moreover, relay-aided communications have experienced raising interest; especially, two-way relaying systems can improve spectral efficiency with short required operating time. Therefore, this Thesis focuses on an uncorrelated massive MIMO two-way relaying system and studies power
scaling laws to investigate how the transmit powers can be scaled to improve the energy efficiency up to several times the energy efficiency without power scaling while approximately maintaining the system performance.
In a similar line, large antenna arrays deployed at the space-constrained relay would give rise to the spatial correlation. For this reason, this Thesis presents an incomplete CSI scheme to evaluate the trade-off between the spatial correlation and system performance. In addition, the advantages of linear processing methods and the effects of channel aging are investigated to further improve the relay-aided system performance.
Similarly, large antenna arrays are required in millimeter-wave communications to achieve narrow beams with higher power gain. This poses the problem that locating the best beam direction requires high power and complexity consumption. Therefore, this Thesis presents several low-complexity beam alignment methods with respect to the state-of-the-art to evaluate the trade-off between complexity and system performance.
Overall, extensive analytical and numerical results show an improved performance and validate the effectiveness of the proposed techniques
Massive MIMO for Full-Duplex Cellular Two-Way Relay Network: A Spectral Efficiency Study
© 2017 IEEE. This paper presents the new analysis of the applications of massive multiple-input-multiple-output (MIMO) in full-duplex (FD) cellular two-way relay networks, and sheds valuable insights on the interactions between massive MIMO, and relay and duplex modes. Practical scenarios are considered, where massive MIMO is deployed at the base station and the relay station. Based on generic relay modes, namely, antenna-selection-based decode-and-forward (DF) relay and signal-space alignment based amplify-and-forward (AF) relay, closed-form expressions for the asymptotic signal-to-interference-plus-noise ratios (SINRs) are derived. The difference between AF and DF in the FD mode is quantified, and so is that between FD and half-duplex (HD) under the two relay modes. With massive MIMO, the superiority of DF in the FD mode is confirmed in terms of spectral efficiency. The sufficient conditions for the FD mode to outperform the HD mode are identified. The effectiveness of massive MIMO in terms of self-loop interference cancellation and inter-user interference suppression is proved. All these insightful findings are corroborated by simulations