Noncooperative Cellular Wireless with Unlimited Numbers of Base Station Antennas
TL;DR: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval and a complete multi-cellular analysis yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve.
Abstract: A cellular base station serves a multiplicity of single-antenna terminals over the same time-frequency interval. Time-division duplex operation combined with reverse-link pilots enables the base station to estimate the reciprocal forward- and reverse-link channels. The conjugate-transpose of the channel estimates are used as a linear precoder and combiner respectively on the forward and reverse links. Propagation, unknown to both terminals and base station, comprises fast fading, log-normal shadow fading, and geometric attenuation. In the limit of an infinite number of antennas a complete multi-cellular analysis, which accounts for inter-cellular interference and the overhead and errors associated with channel-state information, yields a number of mathematically exact conclusions and points to a desirable direction towards which cellular wireless could evolve. In particular the effects of uncorrelated noise and fast fading vanish, throughput and the number of terminals are independent of the size of the cells, spectral efficiency is independent of bandwidth, and the required transmitted energy per bit vanishes. The only remaining impairment is inter-cellular interference caused by re-use of the pilot sequences in other cells (pilot contamination) which does not vanish with unlimited number of antennas.
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TL;DR: Simulation results demonstrate that the proposed schemes outperform the existing buffer-based secure relay selection schemes, in terms of both the secrecy outage probability and the average delay, as the explicit benefits of the novel introduced concepts.
Abstract: In this paper, we propose a novel secure buffer-aided decode-and-forward relay selection that amalgamates the benefits of the buffer-state-based relay selection, the max-ratio criterion, the simultaneous activation of multiple source-to-relay links, and the cooperative beamforming in dual-hop networks. More specifically, the proposed scheme is designed for selecting a single or multiple relay nodes for packet reception or transmission based on the buffer states of relay nodes, while avoiding the detrimental effects of both an empty buffer state and a buffer overflow. Analytical bounds on the secrecy outage probability and the average delay are derived for our proposed scheme, based on a Markov chain process, in order to verify the system model of our proposed scheme. Furthermore, we introduce the concept of cooperative jamming into the proposed scheme, in order to interfere with an eavesdropper’s reception, while dispensing with the full channel state information associated with an eavesdropper at a central coordinator. Our simulation results demonstrate that the proposed schemes outperform the existing buffer-based secure relay selection schemes, in terms of both the secrecy outage probability and the average delay, as the explicit benefits of our novel introduced concepts.
48 citations
Cites methods from "Noncooperative Cellular Wireless wi..."
...The beamforming exemplified in this paper corresponds to simple conjugate beamforming [34], [41], which maximizes the SNR at the destination node....
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TL;DR: This paper proposes two channel estimation schemes that completely remove pilot contamination in time-division duplex (TDD) multicell cellular systems, and the exact closed-form expression for average mean square error (MSE) of the proposed estimators is derived.
Abstract: This paper addresses the problem of channel estimation in time-division duplex (TDD) multicell cellular systems, where the performance of such systems is usually bounded by a bottleneck due to pilot contamination. We propose two channel estimation schemes that completely remove pilot contamination. The exact closed-form expression for average mean square error (MSE) of the proposed estimators is derived. More importantly, our proposed estimators do not need to know the second-order statistics of either desired user channels or interfering user channels. Finally, simulated results confirm gains over existing channel estimation schemes.
48 citations
Cites background from "Noncooperative Cellular Wireless wi..."
...The pilot sequences at different cells might be correlated because the orthogonal property might not hold among a large number of users in the whole network [3]....
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...The effects of pilot contamination in multicell MIMO systems with large number of base station (BS) antennas has been analyzed in [3], in which it was showed that pilot contamination still persists in large-scale MIMO systems....
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Posted Content•
TL;DR: A new precoding technique to mitigate the multi- user interference and the quantization distortions in a downlink multi-user MIMO system with coarsely quantized constant envelope (QCE) signals at the transmitter is presented.
Abstract: Coarsely quantized massive Multiple-Input Multiple-Output (MIMO) systems are gaining more interest due to their power efficiency. We present a new precoding technique to mitigate the Multi-User Interference (MUI) and the quantization distortions in a downlink Multi-User (MU) MIMO system with coarsely Quantized Constant Envelope (QCE) signals at the transmitter. The transmit signal vector is optimized for every desired received vector taking into account the QCE constraint. The optimization is based on maximizing the safety margin to the decision thresholds of the receiver constellation modulation. Simulation results show a significant gain in terms of the uncoded Bit Error Ratio (BER) compared to the existing linear precoding techniques.
47 citations
Cites background from "Noncooperative Cellular Wireless wi..."
...To achieve these challenging requirements, the following technologies are the subject of current research: • massive Multiple-Input Multiple-Output (MIMO) systems, where the Base Stations (BSs) are equipped with a very large number of antennas (100 or more) that can simultaneously serve many users [2]–[6],...
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TL;DR: A novel differential space-time coding scheme is conceived for open-loop noncoherent multiple-input multiple-output (MIMO) downlink scenarios, where the transmission rate increases logarithmically in a scalable manner upon increasing the number of transmit antennas.
Abstract: In this paper, a novel differential space-time coding scheme is conceived for open-loop noncoherent multiple-input multiple-output (MIMO) downlink scenarios, where the transmission rate increases logarithmically in a scalable manner upon increasing the number of transmit antennas. More specifically, the proposed scheme relies on the projection of a differentially encoded square matrix to its rectangular counterpart and so is capable of reducing the number of symbol intervals needed for block transmission. This is especially beneficial for massive MIMO scenarios, in which the number of transmit antennas is very high. Another advantage exclusive to the presented scheme is that no channel state information (CSI) is required at either the transmitter or the receiver, which eliminates pilot overhead, CSI estimation, CSI feedback, and time-division duplex reciprocity. Furthermore, the rectangular transmission matrix of the proposed scheme contains only a single non-zero element per column, and hence, the transmitter may rely on only a single RF chain, similar to the conventional coherent spatial modulation scheme.
47 citations
Cites background or methods from "Noncooperative Cellular Wireless wi..."
...The conjugate BF [1] is a pioneering massive MIMO scheme that was designed for the closed-loop multiuser down-...
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...The single-antenna differential star-QAM scheme [21], the conventional square DSM scheme [17], the semi-blind CE and DD scheme [16], and the conjugate BF scheme [1] were considered as benchmarks for the proposed G-RDSM scheme....
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...Massive multiple-input multiple-output (MIMO) [1]–[4] is a promising technique that can significantly increase both spectral and energy efficiencies in multiuser scenarios and is achieved with the aid of a large-scale antenna array equipped at a base station (BS)....
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...Unlike the conjugate-BF massive MIMO counterpart [1]–[4], the SM scheme operates in an open-loop manner, where CSI at the transmitter (CSIT) is not needed....
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..., the classic square DSTC scheme [10], the conventional differential SM (DSM) scheme [17], [19], the semiblind joint channel estimation (CE) and data detection (DD) scheme [22], and the closed-loop conjugate BF scheme [1], each of which has its own advantages, when operating in a massive MIMO system....
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01 Dec 2014
TL;DR: In this article, the optimal number of scheduled users, K∗, depends on N and other system parameters, while simulations are used to show what happens at finite N, in different interference scenarios, and for different beamforming.
Abstract: Massive MIMO is a promising technique to increase the spectral efficiency of cellular networks, by deploying antenna arrays with hundreds or thousands of active elements at the base stations and performing coherent beamforming. A common rule-of-thumb is that these systems should have an order of magnitude more antennas, N, than scheduled users, K, because the users' channels are then likely to be quasi-orthogonal. However, it has not been proved that this rule-of-thumb actually maximizes the spectral efficiency. In this paper, we analyze how the optimal number of scheduled users, K∗, depends on N and other system parameters. The value of K∗ in the large-N regime is derived in closed form, while simulations are used to show what happens at finite N, in different interference scenarios, and for different beamforming.
47 citations
References
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TL;DR: This paper addresses digital communication in a Rayleigh fading environment when the channel characteristic is unknown at the transmitter but is known (tracked) at the receiver with the aim of leveraging the already highly developed 1-D codec technology.
Abstract: This paper addresses digital communication in a Rayleigh fading environment when the channel characteristic is unknown at the transmitter but is known (tracked) at the receiver. Inventing a codec architecture that can realize a significant portion of the great capacity promised by information theory is essential to a standout long-term position in highly competitive arenas like fixed and indoor wireless. Use (n T , n R ) to express the number of antenna elements at the transmitter and receiver. An (n, n) analysis shows that despite the n received waves interfering randomly, capacity grows linearly with n and is enormous. With n = 8 at 1% outage and 21-dB average SNR at each receiving element, 42 b/s/Hz is achieved. The capacity is more than 40 times that of a (1, 1) system at the same total radiated transmitter power and bandwidth. Moreover, in some applications, n could be much larger than 8. In striving for significant fractions of such huge capacities, the question arises: Can one construct an (n, n) system whose capacity scales linearly with n, using as building blocks n separately coded one-dimensional (1-D) subsystems of equal capacity? With the aim of leveraging the already highly developed 1-D codec technology, this paper reports just such an invention. In this new architecture, signals are layered in space and time as suggested by a tight capacity bound.
6,812 citations
"Noncooperative Cellular Wireless wi..." refers background in this paper
...A point-to-point MIMO system [2] requires expensive multiple-antenna terminals....
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TL;DR: Under certain mild conditions, this scheme is found to be throughput-wise asymptotically optimal for both high and low signal-to-noise ratio (SNR), and some numerical results are provided for the ergodic throughput of the simplified zero-forcing scheme in independent Rayleigh fading.
Abstract: A Gaussian broadcast channel (GBC) with r single-antenna receivers and t antennas at the transmitter is considered. Both transmitter and receivers have perfect knowledge of the channel. Despite its apparent simplicity, this model is, in general, a nondegraded broadcast channel (BC), for which the capacity region is not fully known. For the two-user case, we find a special case of Marton's (1979) region that achieves optimal sum-rate (throughput). In brief, the transmitter decomposes the channel into two interference channels, where interference is caused by the other user signal. Users are successively encoded, such that encoding of the second user is based on the noncausal knowledge of the interference caused by the first user. The crosstalk parameters are optimized such that the overall throughput is maximum and, surprisingly, this is shown to be optimal over all possible strategies (not only with respect to Marton's achievable region). For the case of r>2 users, we find a somewhat simpler choice of Marton's region based on ordering and successively encoding the users. For each user i in the given ordering, the interference caused by users j>i is eliminated by zero forcing at the transmitter, while interference caused by users j
2,616 citations
"Noncooperative Cellular Wireless wi..." refers background in this paper
...An alternative to a point-to-point MIMO system is a multiuser MIMO system [3], [4], [5], [6] in which an antenna array simultaneously serves a multiplicity of autonomous terminals....
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Book•
28 Jun 2004TL;DR: A tutorial on random matrices is provided which provides an overview of the theory and brings together in one source the most significant results recently obtained.
Abstract: Random matrix theory has found many applications in physics, statistics and engineering since its inception. Although early developments were motivated by practical experimental problems, random matrices are now used in fields as diverse as Riemann hypothesis, stochastic differential equations, condensed matter physics, statistical physics, chaotic systems, numerical linear algebra, neural networks, multivariate statistics, information theory, signal processing and small-world networks. This article provides a tutorial on random matrices which provides an overview of the theory and brings together in one source the most significant results recently obtained. Furthermore, the application of random matrix theory to the fundamental limits of wireless communication channels is described in depth.
2,308 citations
"Noncooperative Cellular Wireless wi..." refers background in this paper
...It can be shown that the vector φkjΦ ∗ l has exactly the same probability distribution as does any row vector of Φl [15], [16]....
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01 Jan 2004
2,180 citations
TL;DR: It is shown that the dirty paper achievable region achieves the sum-rate capacity of the MIMO BC by establishing that the maximum sum rate of this region equals an upper bound on the sum rate.
Abstract: We consider a multiuser multiple-input multiple- output (MIMO) Gaussian broadcast channel (BC), where the transmitter and receivers have multiple antennas. Since the MIMO BC is in general a nondegraded BC, its capacity region remains an unsolved problem. We establish a duality between what is termed the "dirty paper" achievable region (the Caire-Shamai (see Proc. IEEE Int. Symp. Information Theory, Washington, DC, June 2001, p.322) achievable region) for the MIMO BC and the capacity region of the MIMO multiple-access channel (MAC), which is easy to compute. Using this duality, we greatly reduce the computational complexity required for obtaining the dirty paper achievable region for the MIMO BC. We also show that the dirty paper achievable region achieves the sum-rate capacity of the MIMO BC by establishing that the maximum sum rate of this region equals an upper bound on the sum rate of the MIMO BC.
1,802 citations
"Noncooperative Cellular Wireless wi..." refers background in this paper
...An alternative to a point-to-point MIMO system is a multiuser MIMO system [3], [4], [5], [6] in which an antenna array simultaneously serves a multiplicity of autonomous terminals....
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