| 1. |
- Yang, Wei, 1987, et al.
(författare)
-
Optimum Power Control at Finite Blocklength
- 2015
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Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 61:9, s. 4598-4615
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the maximal channel coding rate achievable at a given blocklength $n$ and error probability $\epsilon$, when the codewords are subject to a long-term (i.e., averaged-over-all-codeword) power constraint. The second-order term in the large-$n$ expansion of the maximal channel coding rate is characterized both for additive white Gaussian noise (AWGN) channels and for quasi-static fading channels with perfect channel state information available at both the transmitter and the receiver. It is shown that in both cases the second-order term is proportional to $\sqrt{n^{-1}\ln n}$. For the quasi-static fading case, this second-order term is achieved by \emph{truncated channel inversion}, namely, by concatenating a dispersion-optimal code for an AWGN channel subject to a short-term power constraint, with a power controller that inverts the channel whenever the fading gain is above a certain threshold. Easy-to-evaluate approximations of the maximal channel coding rate are developed for both the AWGN and the quasi-static fading case.
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| 2. |
- Zetterberg, P., et al.
(författare)
-
Initial multi-node and antenna transmitter and receiver architectures and schemes; Deliverable D5.1
- 2016
-
Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This deliverable provides the initial concepts and solutions from the technical work related to multi-antenna and multi-node transceiver schemes in millimetre wave (denoted as 6-100GHz) spectrum. It also briefly presents the use cases on which the work will be based and categorises the solutions in terms of their applicability to access, backhaul and relay deployments. Another important contribution from this report is the modelling of the hardware impairments in millimetre wave transceivers and the analysis of their impact on system performance.
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| 3. |
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| 4. |
- Athley, F., et al.
(författare)
-
Analysis of Massive MIMO with hardware impairments and different channel models
- 2015
-
Ingår i: 9th European Conference on Antennas and Propagation, EuCAP 2015, Lisbon, Portugal, 13-17 May 2015. - 9788890701856
-
Konferensbidrag (refereegranskat)abstract
- Massive Multiple-Input Multiple-Output (MIMO) is foreseen to be one of the main technology components in next generation cellular communications (5G). In this paper, fundamental limits on the performance of downlink massive MIMO systems are investigated by means of simulations and analytical analysis. Signal-to-noise-and-interference ratio (SINR) and sum rate for a single-cell scenario multi-user MIMO are analyzed for different array sizes, channel models, and precoding schemes. The impact of hardware impairments on performance is also investigated. Simple approximations are derived that show explicitly how the number of antennas, number of served users, transmit power, and magnitude of hardware impairments affect performance.
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| 5. |
- Balatsoukas-Stimming, Alexios, et al.
(författare)
-
Neural-Network Optimized 1-bit Precoding for Massive MU-MIMO
- 2019
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2019-July
-
Konferensbidrag (refereegranskat)abstract
- Base station (BS) architectures for massive multiuser (MU) multiple-input multiple-output (MIMO) wireless systems are equipped with hundreds of antennas to serve tens of users on the same time-frequency channel. The immense number of BS antennas incurs high system costs, power, and interconnect bandwidth. To circumvent these obstacles, sophisticated MU precoding algorithms that enable the use of 1-bit DACs have been proposed. Many of these precoders feature parameters that are, traditionally, tuned manually to optimize their performance. We propose to use deep-learning tools to automatically tune such 1-bit precoders. Specifically, we optimize the biConvex 1-bit PrecOding (C2PO) algorithm using neural networks. Compared to the original C2PO algorithm, our neural-network optimized (NNO-)C2PO achieves the same error-rate performance at 2× lower complexity. Moreover, by training NNO-C2PO for different channel models, we show that 1-bit precoding can be made robust to vastly changing propagation conditions.
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| 6. |
- Castaneda, Oscar, et al.
(författare)
-
1-bit Massive MU-MIMO Precoding in VLSI
- 2017
-
Ingår i: IEEE Journal on Emerging and Selected Topics in Circuits and Systems. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3365 .- 2156-3357. ; 7:4, s. 508-522
-
Tidskriftsartikel (refereegranskat)abstract
- Massive multi-user (MU) multiple-input multiple-output (MIMO) will be a core technology in fifth-generation (5G) wireless systems as it offers significant improvements in spectral efficiency compared to existing multi-antenna technologies. The presence of hundreds of antenna elements at the base station (BS), however, results in excessively high hardware costs and power consumption, and requires high interconnect throughput between the baseband-processing unit and the radio unit. Massive MU-MIMO that uses low-resolution analog-to-digital and digital-toanalog converters (DACs) has the potential to address all these issues. In this paper, we focus on downlink precoding for massive MU-MIMO systems with 1-bit DACs at the BS. The objective is to design precoders that simultaneously mitigate MU interference and quantization artifacts. We propose two nonlinear 1-bit precoding algorithms and corresponding very large-scale integration (VLSI) designs. Our algorithms rely on biconvex relaxation, which enables the design of efficient 1-bit precoding algorithms that achieve superior error-rate performance compared with that of linear precoding algorithms followed by quantization. To showcase the efficacy of our algorithms, we design VLSI architectures that enable efficient 1-bit precoding for massive MU-MIMO systems, in which hundreds of antennas serve tens of user equipments. We present corresponding field-programmable gate array (FPGA) reference implementations to demonstrate that 1-bit precoding enables reliable and high-rate downlink data transmission in practical systems.
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| 7. |
- Castaneda, Oscar, et al.
(författare)
-
Finite-Alphabet Wiener Filter Precoding for mmWave Massive MU-MIMO Systems
- 2019
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; , s. 178-183
-
Konferensbidrag (refereegranskat)abstract
- Power consumption of multi-user (MU) precoding is a major concern in all-digital massive MU multiple-input multiple-output (MIMO) base-stations with hundreds of antenna elements operating at millimeter-wave (mmWave) frequencies. We propose to replace part of the linear Wiener filter (WF) precoding matrix by a finite-alphabet WF precoding (FAWP) matrix, which enables the use of low-precision hardware that consumes low power and area. To minimize the performance loss of our approach, we present methods that efficiently compute FAWP matrices that best mimic the WF precoder. Our results show that FAWP matrices approach infinite-precision error-rate and error-vector magnitude performance with only 3-bit precoding weights, even when operating in realistic mmWave channels. Hence, FAWP is a promising approach to substantially reduce power consumption and silicon area in all-digital mmWave massive MU-MIMO systems.
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| 8. |
- Castaneda, Oscar, et al.
(författare)
-
VLSI Design of a 3-bit Constant-Modulus Precoder for Massive MU-MIMO
- 2018
-
Ingår i: Proceedings - IEEE International Symposium on Circuits and Systems. - 0271-4310.
-
Konferensbidrag (refereegranskat)abstract
- Fifth-generation (5G) cellular systems will build on massive multi-user (MU) multiple-input multiple-output (MIMO) technology to attain high spectral efficiency. However, having hundreds of antennas and radio-frequency (RF) chains at the base station (BS) entails prohibitively high hardware costs and power consumption. This paper proposes a novel nonlinear precoding algorithm for the massive MU-MIMO downlink in which each RF chain contains an 8-phase (3-bit) constantmodulus transmitter, enabling the use of low-cost and powerefficient analog hardware. We present a high-throughput VLSI architecture and show implementation results on a Xilinx Virtex-7 FPGA. Compared to a recently-reported nonlinear precoder for BS designs that use two 1 -bit digital-to-analog converters per RF chain, our design enables up to 3:75 dB transmit power reduction at no more than a 2.7x increase in FPGA resources.
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| 9. |
- Coskun, Mustafa C., et al.
(författare)
-
Efficient error-correcting codes in the short blocklength regime
- 2019
-
Ingår i: Physical Communication. - : Elsevier BV. - 1874-4907. ; 34, s. 66-79
-
Tidskriftsartikel (refereegranskat)abstract
- The design of block codes for short information blocks (e.g., a thousand or less information bits) is an open research problem that is gaining relevance thanks to emerging applications in wireless communication networks. In this paper, we review some of the most promising code constructions targeting the short block regime, and we compare them with both finite-length performance bounds and classical error-correction coding schemes. The work addresses the use of both binary and high-order modulations over the additive white Gaussian noise channel. We will illustrate how to effectively approach the theoretical bounds with various performance versus decoding complexity tradeoffs.
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| 10. |
- Coskun, Mustafa Cemil, et al.
(författare)
-
Low-Complexity Joint Channel Estimation and List Decoding of Short Codes
- 2019
-
Ingår i: SCC 2019 - 12th International ITG Conference on Systems, Communications and Coding. - 9783800748624
-
Konferensbidrag (refereegranskat)abstract
- A pilot-assisted transmission (PAT) scheme is proposed for short blocklengths, where the pilots are used only to derive an initial channel estimate for the list construction step. The final decision of the message is obtained by applying a non-coherent decoding metric to the codewords composing the list. This allows one to use very few pilots, thus reducing the channel estimation overhead. The method is applied to anordered statistics decoder for communication over a Rayleigh block-fading channel. Gains of up to 1.2 dB as compared to traditional PAT schemes are demonstrated for short codes with QPSK signaling. The approach can be generalized to other list decoders, e.g., to list decoding of polar codes.
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| 11. |
- Devassy, Rahul, 1985, et al.
(författare)
-
Delay and Peak-Age Violation Probability in Short-Packet Transmissions
- 2018
-
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2018-June, s. 2471-2475
-
Konferensbidrag (refereegranskat)abstract
- This paper investigates the distribution of delay and peak age of information in a communication system where packets, generated according to an independent and identically distributed Bernoulli process, are placed in a single-server queue with first-come first-served discipline and transmitted over an additive white Gaussian noise (AWGN) channel. When a packet is correctly decoded, the sender receives an instantaneous error-free positive acknowledgment, upon which it removes the packet from the buffer. In the case of negative acknowledgment, the packet is retransmitted. By leveraging finite-blocklength results for the AWGN channel, we characterize the delay violation and the peak-age violation probability without resorting to approximations based on large deviation theory as in previous literature. Our analysis reveals that there exists an optimum blocklength that minimizes the delay violation and the peak-age violation probabilities. We also show that one can find two blocklength values that result in very similar average delay but significantly different delay violation probabilities. This highlights the importance of focusing on violation probabilities rather than on averages.
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| 12. |
- Devassy, Rahul, 1985, et al.
(författare)
-
Finite-SNR Bounds on the Sum-Rate Capacity of Rayleigh Block-Fading Multiple-Access Channels with no a Priori CSI
- 2015
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:10, s. 3621-3632
-
Tidskriftsartikel (refereegranskat)abstract
- We provide nonasymptotic upper and lower bounds on the sum-rate capacity of Rayleigh block-fading multiple-access channels for the set up where a priori channel state information is not available. The upper bound relies on a dual formula for chan- nel capacity and on the assumption that the users can cooperate perfectly. The lower bound is derived assuming a noncooperative scenario where each user employs unitary space-time modulation (independently from the other users). Numerical results show that the gap between the upper and the lower bound is small already at moderate SNR values. This suggests that the sum-rate capac- ity gains obtainable through user cooperation are minimal for the scenarios considered in the paper.
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| 13. |
- Devassy, Rahul, 1985, et al.
(författare)
-
Nonasymptotic coding-rate bounds for binary erasure channels with feedback
- 2016
-
Ingår i: IEEE Information Theory Workshop (ITW), Cambridge, ENGLAND, SEP 11-14, 2016. - 9781509010912 ; , s. 86-90
-
Konferensbidrag (refereegranskat)abstract
- We present nonasymptotic achievability and converse bounds on the maximum coding rate (for a fixed average error probability and a fixed average blocklength) of variable-length full-feedback (VLF) and variable-length stop-feedback (VLSF) codes operating over a binary erasure channel (BEC). For the VLF setup, the achievability bound relies on a scheme that maps each message onto a variable-length Huffman codeword and then repeats each bit of the codeword until it is received correctly. The converse bound is inspired by the meta-converse framework by Polyanskiy, Poor, and Verdú (2010) and relies on binary sequential hypothesis testing. For the case of zero error probability, our achievability and converse bounds match. For the VLSF case, we provide achievability bounds that exploit the following feature of BEC: the decoder can assess the correctness of its estimate by verifying whether the chosen codeword is the only one that is compatible with the erasure pattern. One of these bounds is obtained by analyzing the performance of a variable-length extension of random linear fountain codes. The gap between the VLSF achievability and the VLF converse bound, when number of messages is small, is significant: 23% for 8 messages on a BEC with erasure probability 0.5. The absence of a tight VLSF converse bound does not allow us to assess whether this gap is fundamental.
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| 14. |
- Devassy, Rahul, 1985, et al.
(författare)
-
Reliable Transmission of Short Packets Through Queues and Noisy Channels Under Latency and Peak-Age Violation Guarantees
- 2019
-
Ingår i: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 37:4, s. 721-734
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the probability that the delay and the peak-age of information exceed a desired threshold in a point-to-point communication system with short information packets. The packets are generated according to a stationary memoryless Bernoulli process, placed in a single-server queue and then transmitted over a wireless channel. A variable-length stop-feedback coding scheme - a general strategy that encompasses simple automatic repetition request (ARQ) and more sophisticated hybrid ARQ techniques as special cases - is used by the transmitter to convey the information packets to the receiver. By leveraging finite-blocklength results, the delay violation and the peak-age violation probabilities are characterized without resorting to approximations based on larg-deviation theory as in previous literature. Numerical results illuminate the dependence of delay and peak-age violation probability on system parameters such as the frame size and the undetected error probability, and on the chosen packet-management policy. The guidelines provided by our analysis are particularly useful for the design of low-latency ultra-reliable communication systems.
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| 15. |
- Durisi, Giuseppe, 1977, et al.
(författare)
-
Short-Packet Communications over Multiple-Antenna Rayleigh-Fading Channels
- 2016
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 64:2, s. 618-629
-
Tidskriftsartikel (refereegranskat)abstract
- Motivated by the current interest in ultra-reliable, low-latency, machine-type communication systems, we investigate the tradeoff between reliability, throughput, and latency in the transmission of information over multiple-antenna Rayleigh block-fading channels. Specifically, we obtain finite-blocklength, finite-SNR upper and lower bounds on the maximum coding rate achievable over such channels for a given constraint on the packet error probability. Numerical evidence suggests that our bounds delimit tightly the maximum coding rate already for short blocklengths (packets of about 100 symbols). Furthermore, our bounds reveal the existence of a tradeoff between the rate gain obtainable by spreading each codeword over all available time-frequency-spatial degrees of freedom, and the rate loss caused by the need of estimating the fading coefficients over these degrees of freedom. In particular, our bounds allow us to determine the optimal number of transmit antennas and the optimal number of time-frequency diversity branches that maximize the rate. Finally, we show that infinite-blocklength performance metrics such as the ergodic capacity and the outage capacity yield inaccurate throughput estimates.
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| 16. |
- Durisi, Giuseppe, 1977, et al.
(författare)
-
Toward Massive, Ultrareliable, and Low-Latency Wireless Communication With Short Packets
- 2016
-
Ingår i: Proceedings of the IEEE. - : Institute of Electrical and Electronics Engineers (IEEE). - 1558-2256 .- 0018-9219. ; 104:9, s. 1711-1726
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the recent advances in the design of highspeed wireless systems are based on information-theoretic principles that demonstrate how to efficiently transmit long data packets. However, the upcoming wireless systems, notably the fifth-generation (5G) system, will need to support novel traffic types that use short packets. For example, short packets represent the most common form of traffic generated by sensors and other devices involved in machine-to-machine (M2M) communications. Furthermore, there are emerging applications in which small packets are expected to carry critical information that should be received with low latency and ultra-high reliability. Current wireless systems are not designed to support short-packet transmissions. For example, the design of current systems relies on the assumption that the metadata (control information) is of negligible size compared to the actual information payload. Hence, transmitting metadata using heuristic methods does not affect the overall system performance. However, when the packets are short, metadata may be of the same size as the payload, and the conventional methods to transmit it may be highly suboptimal. In this paper, we review recent advances in information theory, which provide the theoretical principles that govern the transmission of short packets. We then apply these principles to three exemplary scenarios (the two-way channel, the downlink broadcast channel, and the uplink random access channel), thereby illustrating how the transmission of control information can be optimized when the packets are short. The insights brought by these examples suggest that new principles are needed for the design of wireless protocols supporting short packets. These principles will have a direct impact on the system design.
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| 17. |
- Durisi, Giuseppe, 1977, et al.
(författare)
-
Towards Massive, Ultra-Reliable, and Low-Latency Wireless Communication with Short Packets
- 2016
-
Ingår i: Proceedings of the IEEE. - 1558-2256 .- 0018-9219.
-
Tidskriftsartikel (refereegranskat)abstract
- Most of the recent advances in the design of high-speed wireless systems are based on information-theoretic principles that demonstrate how to efficiently transmit long data packets. However, the upcoming wireless systems, notably the 5G system, will need to support novel traffic types that use short packets. For example, short packets represent the most common form of traffic generated by sensors and other devices involved in Machine-to-Machine (M2M) communications. Furthermore, there are emerging applications in which small packets are expected to carry critical information that should be received with low latency and ultra-high reliability. Current wireless systems are not designed to support short-packet transmissions. For example, the design of current systems relies on the assumption that the metadata (control information) is of negligible size compared to the actual information payload. Hence, transmitting metadata using heuristic methods does not affect the overall system performance. However, when the packets are short, metadata may be of the same size as the payload, and the conventional methods to transmit it may be highly suboptimal. In this article, we review recent advances in information theory, which provide the theoretical principles that govern the transmission of short packets. We then apply these principles to three exemplary scenarios (the two-way channel, the downlink broadcast channel, and the uplink random access channel), thereby illustrating how the transmission of control information can be optimized when the packets are short. The insights brought by these examples suggest that new principles are needed for the design of wireless protocols supporting short packets. These principles will have a direct impact on the system design.
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| 18. |
- Ettefagh, Yasaman, 1989, et al.
(författare)
-
All-Digital Massive MIMO Uplink and Downlink Rates under a Fronthaul Constraint
- 2019
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. - 9781728143002 ; 2019-November, s. 416-420
-
Konferensbidrag (refereegranskat)abstract
- We characterize the rate achievable in a bidirectional quasi-static link where several user equipments communicate with a massive multiple-input multiple-output base station (BS). In the considered setup, the BS operates in full-digital mode, the physical size of the antenna array is limited, and there exists a rate constraint on the fronthaul interface connecting the (possibly remote) radio head to the digital baseband processing unit. Our analysis enables us to determine the optimal resolution of the analog-todigital and digital-to-analog converters as well as the optimal number of active antenna elements to be used in order to maximize the transmission rate on the bidirectional link, for a given constraint on the outage probability and on the fronthaul rate. We investigate both the case in which perfect channel-state information is available, and the case in which channel-state information is acquired through pilot transmission, and is, hence, imperfect. For the second case, we present a novel rate expression that relies on the generalized mutual-information framework.
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| 19. |
- Ferrante, Guido, 1987, et al.
(författare)
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Pilot-Assisted Short Packet Transmission over Memoryless Block-Fading Channels
- 2018
-
Ingår i: Annual Conference on Information Sciences and Systems (CISS). - 9781538605806 ; , s. 389-394
-
Konferensbidrag (refereegranskat)abstract
- Leveraging recent results in finite-blocklength information theory, we investigate the problem of designing a control channel in a 5G system. The setup involves the transmission, under stringent latency and reliability constraints, of a short data packet containing a small information payload, over a propagation channel that offers limited frequency diversity and no time diversity. We present an achievability bound, built upon the random-coding union bound with parameter s (Martinez & Guillen i Fabregas, 2011), which relies on quadrature phase-shift keying modulation, pilot-assisted transmission to estimate the fading channel, and scaled nearest-neighbor decoding at the receiver. Using our achievability bound, we determine how many pilot symbols should be transmitted to optimally trade between channel-estimation errors and rate loss due to pilot overhead. Our analysis also reveals the importance of using multiple antennas at the transmitter and/or the receiver to provide the spatial diversity needed to meet the stringent reliability constraint.
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| 20. |
- Ferrante, Guido, 1987, et al.
(författare)
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Pilot-Assisted Short-Packet Transmission over Multiantenna Fading Channels: A 5G Case Study
- 2018
-
Ingår i: 2018 52nd Annual Conference on Information Sciences and Systems, CISS 2018. - 9781538605790 ; 21 May 2018, s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- Leveraging recent results in finite-blocklength information theory, we investigate the problem of designing a control channel in a 5G system. The setup involves the transmission, under stringent latency and reliability constraints, of a short data packet containing a small information payload, over a propagation channel that offers limited frequency diversity and no time diversity. We present an achievability bound, built upon the random-coding union bound with parameter s (Martinez & Guillén i Fàbregas, 2011), which relies on quadrature phase-shift keying modulation, pilot-assisted transmission to estimate the fading channel, and scaled nearest-neighbor decoding at the receiver. Using our achievability bound, we determine how many pilot symbols should be transmitted to optimally trade between channel-estimation errors and rate loss due to pilot overhead. Our analysis also reveals the importance of using multiple antennas at the transmitter and/or the receiver to provide the spatial diversity needed to meet the stringent reliability constraint.
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| 21. |
- Fountoulakis, Emmanouil, 1991-
(författare)
-
Performance Analysis and Optimization for Time Critical Networking
- 2019
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Future communication systems will be characterized by heterogeneous traffic and requirements. Time critical applications like cyberphysical systems, augmented and virtual reality, raise the need for a low-latency based network. At the same time, conventional devices requiring for high throughput will co-exist with time critical applications. Besides the new technologies, new scheduling and optimization techniques are needed to face these challenges. In this thesis, we investigate the issues arising from the deployment of these technologies. In Paper I, we explore the benefits of dynamic Transmission Time Interval (TTI) selection in a heterogeneous network environment. We consider packets with deadlines and we optimize jointly the TTI length and the channel allocation. After proving the NP-hardness of the problem, we propose a greedy algorithm taking decisions in polynomial time. The first work opens new questions regarding the deadline-constrained traffic such as how the minimum average drop rate can be achieved. In Paper II, we consider power-limited devices with deadline-constrained traffic. Lyapunov optimization methods are explored to solve the problem with time average objective and constraints. We develop a dynamic, polynomial time, algorithm that finds an approximation of the dropping rate minimization problem under average power constraints. Besides the new techniques, future communication systems will require the development of new technologies for a more exible and elastic network. Multi-access Edge Computing (MEC) and Virtual Network Function (VNF) technologies are considered two of the key technologies for next generation networks. In Paper III, we analyze the performance of a network that hosts VNF and consists of MEC servers and servers at the core. As a first step, we consider a simple end-to-end communication system and provide analytical expressions for the end-to-end delay and system throughput by applying tools from queueing theory. Based on the first step, we provide the methodology for analyzing scaled-up systems with arbitrary number of servers. Simulation results show that our analytical model performs well. Furthermore, this work provides insights for the design and performance optimization of such systems such as optimal ow control and resource allocation.
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| 22. |
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| 23. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Linear Precoding With Low-Resolution DACs for Massive MU-MIMO-OFDM Downlink
- 2019
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 18:3, s. 1595-1609
-
Tidskriftsartikel (refereegranskat)abstract
- We consider the downlink of a massive multiuser (MU) multiple-input multiple-output (MIMO) system in which the base station (BS) is equipped with low-resolution digital-to-analog converters (DACs). In contrast to most existing results, we assume that the system operates over a frequency-selective wideband channel and uses orthogonal frequency division multiplexing (OFDM) to simplify equalization at the user equipments (UEs). Furthermore, we consider the practically relevant case of oversampling DACs. We theoretically analyze the uncoded bit error rate (BER) performance with linear precoders (e.g., zero forcing) and quadrature phase-shift keying using Bussgang's theorem. We also develop a lower bound on the information-theoretic sum-rate throughput achievable with Gaussian inputs, which can be evaluated in closed form for the case of 1-bit DACs. For the case of multi-bit DACs, we derive approximate, yet accurate, expressions for the distortion caused by low-precision DACs, which can be used to establish the lower bounds on the corresponding sum-rate throughput. Our results demonstrate that, for a massive MU-MIMO-OFDM system with a 128-antenna BS serving 16 UEs, only 3-4 DAC bits are required to achieve an uncoded BER of 10(-4) with a negligible performance loss compared to the infinite-resolution case at the cost of additional out-of-band emissions. Furthermore, our results highlight the importance of considering the inherent spatial and temporal correlations caused by low-precision DACs.
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| 24. |
- Jacobsson, Sven, 1990, et al.
(författare)
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Massive MU-MIMO-OFDM Downlink with One-Bit DACs and Linear Precoding
- 2018
-
Ingår i: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813. ; , s. 1-6
-
Konferensbidrag (refereegranskat)abstract
- Massive multiuser (MU) multiple-input multiple- output (MIMO) is foreseen to be a key technology in future wireless communication systems. In this paper, we analyze the downlink performance of an orthogonal frequency division multiplexing (OFDM)-based massive MU-MIMO system in which the base station (BS) is equipped with 1-bit digital-to-analog converters (DACs). Using Bussgang’s theorem, we characterize the performance achievable with linear precoders (such as maximal-ratio transmission and zero forcing) in terms of bit error rate (BER). Our analysis accounts for the possibility of oversampling the time-domain transmit signal before the DACs. We further develop a lower bound on the information-theoretic sum-rate throughput achievable with Gaussian inputs.Our results suggest that the performance achievable with 1-bit DACs in a massive MU-MIMO-OFDM downlink are satisfactory provided that the number of BS antennas is sufficiently large.
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| 25. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Massive MU-MIMO-OFDM uplink with direct RF-sampling and 1-Bit ADCs
- 2019
-
Ingår i: 2019 IEEE Globecom Workshops, GC Wkshps 2019 - Proceedings.
-
Konferensbidrag (refereegranskat)abstract
- Advances in analog-to-digital converter (ADC) technology have opened up the possibility to directly digitize wideband radio frequency (RF) signals, avoiding the need for analog down- conversion. In this work, we consider an orthogonal frequency- division multiplexing (OFDM)-based massive multi-user (MU) multiple-input multiple-output (MIMO) uplink system that relies on direct RF-sampling at the base station and digitizes the received RF signals with 1-bit ADCs. Using Bussgang's theorem, we provide an analytical expression for the error-vector magnitude (EVM) achieved by digital down-conversion and zero-forcing combining. Our results demonstrate that direct RF-sampling 1-bit ADCs enables low EVM and supports high-order constellations in the massive MU-MIMO- OFDM uplink.
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| 26. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Massive MU-MIMO-OFDM Uplink with Hardware Impairments: Modeling and Analysis
- 2018
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; , s. 1829-1835
-
Konferensbidrag (refereegranskat)abstract
- © 2018 IEEE. We study the impact of hardware impairments at the base station (BS) of an orthogonal frequency-division multiplexing (OFDM)-based massive multiuser (MU) multiple-input multiple-output (MIMO) uplink system. We leverage Bussgang's theorem to develop accurate models for the distortions caused by nonlinear low-noise amplifiers, local oscillators with phase noise, and oversampling finite-resolution analog-to-digital converters. By combining the individual effects of these hardware models, we obtain a composite model for the BS-side distortion caused by nonideal hardware that takes into account its inherent correlation in time, frequency, and across antennas. We use this composite model to analyze the impact of BS-side hardware impairments on the performance of realistic massive MU-MIMO-OFDM uplink systems.
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| 27. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Massive multiuser MIMO downlink with low- resolution converters
- 2018
-
Ingår i: International Zurich Seminar on Information and Communication (IZS 2018) Proceedings.
-
Konferensbidrag (refereegranskat)abstract
- In this review paper, we analyze the downlink of a massive multiuser multiple-input multiple-output system in which the base station is equipped with low-resolution digital-to-analog converters (DACs). Using Bussgang’s theorem, we characterize the sum-rate achievable with a Gaussian codebook and scaled nearestneighbor decoding at the user equipments (UE). For the case of 1-bit DACs, we show how to evaluate the sum-rate using Van Vleck’s arcsine law. For the case of multi-bit DACs, for which the sum-rate cannot be expressed in closed-form, we present two approximations. The first one, which is obtained by ignoring the overload (or clipping) distortion caused by the DACs, turns out to be accurate provided that one can adapt the dynamic range of the quantizer to the received-signal strength so as to avoid clipping. The second approximation, which is obtained by modeling the distortion noise as a white process, both in time and space, is accurate whenever the resolution of the DACs is sufficiently high and when the oversampling ratio is small. We conclude the paper by discussing extensions to orthogonal frequency-division multiplexing systems; we also touch upon the problem of out-of-band emissions in lowprecision-DAC architectures.
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| 28. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
MSE-Optimal 1-Bit Precoding for Multiuser MIMO Via Branch and Bound
- 2018
-
Ingår i: ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings. - 1520-6149. ; , s. 3589-3593
-
Konferensbidrag (refereegranskat)abstract
- In this paper, we solve the sum mean-squared error (MSE)-optimal 1-bit quantized precoding problem exactly for small-to-moderate sized multiuser multiple-input multiple-output (MU-MIMO) systems via branch and bound. To this end, we reformulate the original NP-hard precoding problem as a tree search and deploy a number of strategies that improve the pruning efficiency without sacrificing optimality. We evaluate the error-rate performance and the complexity of the resulting 1-bit branch-and-bound (BB-1) precoder, and compare its efficacy to that of existing, suboptimal algorithms for 1-bit precoding in MU-MIMO systems.
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| 29. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Nonlinear 1-bit precoding for massive MU-MIMO with higher-order modulation
- 2017
-
Ingår i: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; , s. 763-767
-
Konferensbidrag (refereegranskat)abstract
- Massive multi-user (MU) multiple-input multiple-output (MIMO) is widely believed to be a core technology for the upcoming fifth-generation (5G) wireless communication standards. The use of low-precision digital-to-analog converters (DACs) in MU-MIMO base stations is of interest because it reduces the power consumption, system costs, and raw baseband data rates. In this paper, we develop novel algorithms for downlink precoding in massive MU-MIMO systems with 1-bit DACs that support higher-order modulation schemes such as 8-PSK or 16-QAM. Specifically, we present low-complexity nonlinear precoding algorithms that achieve low error rates when combined with blind or training-based channel-estimation algorithms at the user equipment. These results are in stark contrast to linear-quantized precoding algorithms, which suffer from a high error floor if used with high-order modulation schemes and 1-bit DACs
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| 30. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Nonlinear Precoding for Phase-Quantized Constant-Envelope Massive MU-MIMO-OFDM
- 2018
-
Ingår i: 2018 25TH INTERNATIONAL CONFERENCE ON TELECOMMUNICATIONS (ICT). - 9781538623213 ; , s. 367-372
-
Konferensbidrag (refereegranskat)abstract
- We propose a nonlinear phase-quantized constant-envelope precoding algorithm for the massive multi-user (MU) multiple-input multiple-output (MIMO) downlink. Specifically, we adapt the squared-infinity norm Douglas-Rachford splitting (SQUID) precoder to systems that use oversampling digital-to-analog converters (DACs) at the base station (BS) and orthogonal frequency-division multiplexing (OFDM) to communicate over frequency-selective channels. We demonstrate that the proposed SQUID-OFDM precoder is able to generate transmit signals that are constrained to constant envelope, which enables the use of power-efficient analog radio-frequency circuitry at the BS. By quantizing the phase of the resulting constant-envelope signal, we obtain a finite-cardinality transmit signal that can be synthesized by low-resolution (e.g., 1-bit) DACs. We use error-rate simulations to demonstrate the superiority of SQUID-OFDM over linear-quantized precoders for massive MU-MIMO-OFDM systems.
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| 31. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
On Out-of-Band Emissions of Quantized Precoding in Massive MU-MIMO-OFDM
- 2017
-
Ingår i: Conference Record of the Asilomar Conference on Signals Systems and Computers. - 1058-6393. - 9781538618233 ; , s. 21-26
-
Konferensbidrag (refereegranskat)abstract
- We analyze out-of-band (OOB) emissions in the massive multi-user (MU) multiple-input multiple-output (MIMO) downlink. We focus on systems in which the base station (BS) is equipped with low-resolution digital-to-analog converters (DACs) and orthogonal frequency-division multiplexing (OFDM) is used to communicate to the user equipments (UEs) over frequency- selective channels. We demonstrate that analog filtering in combination with simple frequency-domain digital predistortion (DPD) at the BS enables a significant reduction of OOB emissions, but degrades the signal-to-interference-noise-and-distortion ratio (SINDR) at the UEs and increases the peak-to-average power ratio (PAR) at the BS. We use Bussgang’s theorem to characterize the tradeoffs between OOB emissions, SINDR, and PAR, and to study the impact of analog filters and DPD on the error-rate perfor- mance of the massive MU-MIMO-OFDM downlink. Our results show that by carefully tuning the parameters of the analog filters, one can achieve a significant reduction in OOB emissions with only a moderate degradation of error-rate performance and PAR.
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| 32. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
One-Bit Massive MIMO: Channel Estimation and High-Order Modulations
- 2015
-
Ingår i: 2015 IEEE International Conference on Communication Workshop, ICCW 2015. - 9781467363051 ; , s. 1304-1309
-
Konferensbidrag (refereegranskat)abstract
- We investigate the information-theoretic throughout achievable on a fading communication link when the receiver is equipped with one-bit analog-to-digital converters (ADCs). The analysis is conducted for the setting where neither the transmitter nor the receiver have a priori information on the realization of the fading channels. This means that channel-state information needs to be acquired at the receiver on the basis of the one-bit quantized channel outputs. We show that least-squares (LS) channel estimation combined with joint pilot and data processing is capacity achieving in the single-user, single-receive-antenna case. We also investigate the achievable uplink throughput in a massive multiple-input multiple-output system where each element of the antenna array at the receiver base-station feeds a one-bit ADC. We show that LS channel estimation and maximum-ratio combining are sufficient to support both multiuser operation and the use of high-order constellations. This holds in spite of the severe nonlinearity introduced by the one-bit ADCs.
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| 33. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Quantized Precoding for Massive MU-MIMO
- 2017
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 65:11, s. 4670-4684
-
Tidskriftsartikel (refereegranskat)abstract
- Massive multiuser (MU) multiple-input multiple-output (MIMO) is foreseen to be one of the key technologies in fifth-generation wireless communication systems. In this paper, we investigate the problem of downlink precoding for a narrowband massive MU-MIMO system with low-resolution digital-to-analog converters (DACs) at the base station (BS). We analyze the performance of linear precoders, such as maximal-ratio transmission and zero-forcing, subject to coarse quantization. Using Bussgang's theorem, we derive a closed-form approximation on the rate achievable under such coarse quantization. Our results reveal that the performance attainable with infinite-resolution DACs can be approached using DACs having only 3-4 bits of resolution, depending on the number of BS antennas and the number of user equipments (UEs). For the case of 1-bit DACs, we also propose novel nonlinear precoding algorithms that significantly outperform linear precoders at the cost of an increased computational complexity. Specifically, we show that nonlinear precoding incurs only a 3 dB penalty compared with the infinite-resolution case for an uncoded bit-error rate of 10-3, in a system with 128 BS antennas that uses 1-bit DACs and serves 16 single-antenna UEs. In contrast, the penalty for linear precoders is about 8dB.
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| 34. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Throughput Analysis of Massive MIMO Uplink With Low-Resolution ADCs
- 2017
-
Ingår i: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 16:6, s. 4038-4051
-
Tidskriftsartikel (refereegranskat)abstract
- We investigate the uplink throughput achievable by a multiple-user (MU) massive multiple-input multiple-output (MIMO) system, in which the base station is equipped with a large number of low-resolution analog-to-digital converters (ADCs). Our focus is on the case where neither the transmitter nor the receiver have any a priori channel state information. This implies that the fading realizations have to be learned through pilot transmission followed by channel estimation at the receiver, based on coarsely quantized observations. We propose a novel channel estimator, based on Bussgang's decomposition, and a novel approximation to the rate achievable with finite-resolution ADCs, both for the case of finite-cardinality constellations and of Gaussian inputs, that is accurate for a broad range of system parameters. Through numerical results, we illustrate that, for the 1-bit quantized case, pilot-based channel estimation together with maximal-ratio combing, or zero-forcing detection enables reliable multi-user communication with high-order constellations, in spite of the severe nonlinearity introduced by the ADCs. Furthermore, we show that the rate achievable in the infinite-resolution (no quantization) case can be approached using ADCs with only a few bits of resolution. We finally investigate the robustness of low-ADC-resolution MU-MIMO uplink against receive power imbalances between the different users, caused for example by imperfect power control.
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| 35. |
- Jacobsson, Sven, 1990, et al.
(författare)
-
Timing and Frequency Synchronization for 1-bit Massive MU-MIMO-OFDM Downlink
- 2019
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. - 9781538665282
-
Konferensbidrag (refereegranskat)abstract
- We consider timing and frequency synchronization for the massive multiuser (MU) multiple-input multiple-output (MIMO) downlink where 1-bit digital-to-analog converters (DACs) are used at the base station (BS). We focus on the practically relevant scenario in which orthogonal-frequency division multiplexing (OFDM) is used to communicate over frequency-selective channels. Our contributions are twofold. First, we use Bussgang's theorem to analyze the impact on performance caused by timing and frequency offsets in the presence of 1-bit DACs at the BS. Second, we demonstrate the efficacy of the widely used Schmidl-Cox synchronization algorithm. Our results demonstrate that the 1-bit massive MU-MIMO-OFDM downlink is resilient against timing and frequency offsets.
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| 36. |
- Keykhosravi, Kamran, 1990, et al.
(författare)
-
A Tighter Upper Bound on the Capacity of the Nondispersive Optical Fiber Channel
- 2017
-
Ingår i: European Conference on Optical Communication, ECOC.
-
Konferensbidrag (refereegranskat)abstract
- An upper bound on the capacity of the nondispersive optical fiber channel is presented. This bound, which is valid for arbitrary launch powers, confines the capacity within a much narrower range compared to what the previously known upper bound provided.
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| 37. |
- Keykhosravi, Kamran, 1990, et al.
(författare)
-
Accuracy Assessment of Nondispersive Optical Perturbative Models through Capacity Analysis
- 2019
-
Ingår i: Entropy. - : MDPI AG. - 1099-4300. ; 21:8
-
Tidskriftsartikel (refereegranskat)abstract
- A number of simplified models, based on perturbation theory, have been proposed for the fiber-optical channel and have been extensively used in the literature. Although these models are mainly developed for the low-power regime, they are used at moderate or high powers as well. It remains unclear to what extent the capacity of these models is affected by the simplifying assumptions under which they are derived. In this paper, we consider single-channel data transmission based on three continuous-time optical models: (i) a regular perturbative channel, (ii) a logarithmic perturbative channel, and (iii) the stochastic nonlinear Schrödinger (NLS) channel. To obtain analytically tractable discrete-time models, we consider zero-dispersion fibers and a sampling receiver. We investigate the per-sample capacity of these models. Specifically, (i) we establish tight bounds on the capacity of the regular perturbative channel; (ii) we obtain the capacity of the logarithmic perturbative channel; and (iii) we present a novel upper bound on the capacity of the zero-dispersion NLS channel. Our results illustrate that the capacity of these models departs from each other at high powers because these models yield different capacity pre-logs. Since all three models are based on the same physical channel, our results highlight that care must be exercised in using simplified channel models in the high-power regime.
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| 38. |
- Keykhosravi, Kamran, 1990, et al.
(författare)
-
Demodulation and Detection Schemes for a Memoryless Optical WDM Channel
- 2018
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 66:7, s. 2994-3005
-
Tidskriftsartikel (refereegranskat)abstract
- It is well known that matched filtering and sampling (MFS) demodulation together with minimum Euclidean distance (MD) detection constitute the optimal receiver for the additive white Gaussian noise channel. However, for a general nonlinear transmission medium, MFS does not provide sufficient statistics, and therefore is suboptimal. Nonetheless, this receiver is widely used in optical systems, where the Kerr nonlinearity is the dominant impairment at high powers. In this paper, we consider a suite of receivers for a two-user channel subject to a type of nonlinear interference that occurs in wavelength-division-multiplexed channels. The asymptotes of the symbol error rate (SER) of the considered receivers at high powers are derived or bounded analytically. Moreover, Monte-Carlo simulations are conducted to evaluate the SER for all the receivers. Our results show that receivers that are based on MFS cannot achieve arbitrary low SERs, whereas the SER goes to zero as the power grows for the optimal receiver. Furthermore, we devise a heuristic demodulator, which together with the MD detector yields a receiver that is simpler than the optimal one and can achieve arbitrary low SERs. The SER performance of the proposed receivers is also evaluated for some single-span fiber-optical channels via split-step Fourier simulations.
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| 39. |
- Keykhosravi, Kamran, 1990, et al.
(författare)
-
How to Increase the Achievable Information Rate by Per-Channel Dispersion Compensation
- 2019
-
Ingår i: Journal of Lightwave Technology. - 0733-8724 .- 1558-2213. ; 37:10, s. 2443-2451
-
Tidskriftsartikel (refereegranskat)abstract
- Deploying periodic inline chromatic dispersion compensation enables reducing the complexity of the digital back propagation (DBP) algorithm. However, compared with nondispersion-managed (NDM) links, dispersion-managed (DM) ones suffer a stronger cross-phase modulation (XPM). Utilizing per-channel dispersion-managed (CDM) links (e.g., using fiber Bragg grating) allows for a complexity reduction of DBP, while abating XPM compared to DM links. In this paper, we show for the first time that CDM links enable also a more effective XPM compensation compared to NDM ones, allowing a higher achievable information rate (AIR). This is explained by resorting to the frequency-resolved logarithmic perturbation model and showing that per-channel dispersion compensation increases the frequency correlation of the distortions induced by XPM over the channel bandwidth, making them more similar to a conventional phase noise. We compare the performance (in terms of the AIR) of a DM, an NDM, and a CDM link, considering two types of mismatched receivers: one neglects the XPM phase distortion and the other compensates for it. With the former, the CDM link is inferior to the NDM one due to an increased in-band signal--noise interaction. However, with the latter, a higher AIR is obtained with the CDM link than with the NDM one owing to a higher XPM frequency correlation. The DM link has the lowest AIR for both receivers because of a stronger XPM.
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| 40. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
Capacity of SIMO and MISO Phase-Noise Channels with Common/Separate Oscillators
- 2015
-
Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 63:9, s. 3218-3231
-
Tidskriftsartikel (refereegranskat)abstract
- In multiple antenna systems, phase noise due to instabilities of the radio-frequency (RF) oscillators, acts differently depending on whether the RF circuitries connected to each antenna are driven by separate (independent) local oscillators (SLO) or by a common local oscillator (CLO). In this paper, we investigate the high-SNR capacity of single-input multiple-output (SIMO) and multiple-output single-input (MISO) phase-noise channels for both the CLO and the SLO configurations.Our results show that the first-order term in the high-SNR capacity expansion is the same for all scenarios (SIMO/MISO and SLO/CLO), and equal to 0.5ln(SNR), where SNR stands for the signal-to-noise ratio. On the contrary, the second-order term, which we refer to as phase-noise number, turns out to be scenario-dependent. For the SIMO case, the SLO configuration provides a diversity gain, resulting in a larger phase-noise number than for the CLO configuration. For the case of Wiener phase noise, a diversity gain of at least 0.5ln(M) can be achieved, where M is the number of receive antennas. For the MISO, the CLO configuration yields a higher phase-noise number than the SLO configuration. This is because with the CLO configuration one can obtain a coherent-combining gain through maximum ratio transmission (a.k.a. conjugate beamforming). This gain is unattainable with the SLO configuration.
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| 41. |
- Khanzadi, M Reza, 1983, et al.
(författare)
-
High-SNR Capacity of Multiple-Antenna Phase-Noise Channels with Common/Separate RF Oscillators
- 2015
-
Ingår i: IEEE International Conference on Communications. - 1550-3607. - 9781467364324 ; , s. 4012-4017
-
Konferensbidrag (refereegranskat)abstract
- In multiple antenna systems, phase noise due to instabilities of the radio-frequency (RF) oscillators, acts differently depending on whether the RF circuitries connected to each antenna are driven by separate (independent) local oscillators (SLO) or by a common local oscillator (CLO). In this paper, we investigate the high-SNR capacity of single-input multiple-output (SIMO) and multiple-output single-input (MISO) phase-noise channels for both the CLO and the SLO configurations.Our results show that the first-order term in the high-SNR capacity expansion is the same for all scenarios (SIMO/MISO and SLO/CLO), and equal to 0.5ln(SNR), where SNR stands for the signal-to-noise ratio. On the contrary, the second-order term, which we refer to as phase-noise number, turns out to be scenario-dependent. For the SIMO case, the SLO configuration provides a diversity gain, resulting in a larger phase-noise number than for the CLO configuration. For the case of Wiener phase noise, a diversity gain of at least 0.5ln(M) can be achieved, where M is the number of receive antennas. For the MISO, the CLO configuration yields a higher phase-noise number than the SLO configuration. This is because with the CLO configuration one can obtain a coherent-combining gain through maximum ratio transmission (a.k.a. conjugate beamforming). This gain is unattainable with the SLO configuration.
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| 42. |
- Lancho, Alejandro, et al.
(författare)
-
A High-SNR Normal Approximation for Single-Antenna Rayleigh Block-Fading Channels
- 2017
-
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; , s. 1773-1777
-
Konferensbidrag (refereegranskat)abstract
- This paper concerns the maximal achievable rate at which data can be transmitted over a non-coherent, single- antenna, Rayleigh block-fading channel using an error-correcting code of a given blocklength with a block-error probability not exceeding a given value. In particular, a high-SNR normal approximation of the maximal achievable rate is presented that becomes accurate as the signal-to-noise ratio (SNR) and the number of coherence intervals L over which we code tend to infinity. Numerical analyses suggest that the approximation is accurate already at SNR values of 15 dB.
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| 43. |
- Lancho, Alejandro, et al.
(författare)
-
Normal Approximations for Fading Channels
- 2018
-
Ingår i: 2018 52ND ANNUAL CONFERENCE ON INFORMATION SCIENCES AND SYSTEMS (CISS). - 9781538605790 - 9781538605790
-
Konferensbidrag (refereegranskat)abstract
- Capacity and outage capacity characterize the maximum coding rate at which reliable communication is feasible when there are no constraints on the packet length. Evaluated for fading channels, they are important performance benchmarks for wireless communication systems. However, the latency of a communication system is proportional to the length of the packets it exchanges, so assuming that there are no constraints on the packet length may be overly optimistic for communication systems with stringent latency constraints. Recently, there has been great interest within the information theory community in characterizing the maximum coding rate for short packet lengths. Research on this topic is often concerned with asymptotic expansions of the coding rate with respect to the packet length, which then give rise to normal approximations. In this paper, we review existing normal approximations for single-antenna Rayleigh block-fading channels and compare them with the highSNR normal approximation we presented at the 2017 IEEE International Symposium on Information Theory (Lancho, Koch, and Durisi, 2017). We further discuss how these normal approximations may help to assess the performance of communication protocols.
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| 44. |
- Lancho Serrano, Alejandro, 1991, et al.
(författare)
-
Saddlepoint Approximations for Noncoherent Single-Antenna Rayleigh Block-Fading Channels
- 2019
-
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2019-July, s. 612-616
-
Konferensbidrag (refereegranskat)abstract
- This paper presents saddlepoint approximations of state-of-the-art converse and achievability bounds for noncoherent, single-antenna, Rayleigh block-fading channels. These approximations can be calculated efficiently and are shown to be accurate for SNR values as small as 0 dB, blocklengths of 168 channel uses or more, and when the channel's coherence interval is not smaller than two. It is demonstrated that the derived approximations recover both the normal approximation and the reliability function of the channel.
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| 45. |
- Liva, Gianluigi, et al.
(författare)
-
Short Codes with Mismatched Channel State Information: A Case Study
- 2017
-
Ingår i: Proc. IEEE Int. Workshop Signal Process. Advances Wireless Commun. (SPAWC).
-
Konferensbidrag (refereegranskat)abstract
- The rising interest in applications requiring the transmission of small amounts of data has recently lead to the development of accurate performance bounds and of powerful channel codes for the transmission of short-data packets over the AWGN channel. Much less is known about the interaction between error control coding and channel estimation at short blocks when transmitting over channels with states (e.g., fading channels, phase-noise channels, etc. . . ) for the setup where no a priori channel state information (CSI) is available at the trans- mitter and the receiver. In this paper, we use the mismatched- decoding framework to characterize the fundamental tradeoff occurring in the transmission of short data packet over an AWGN channel with unknown gain that stays constant over the packet. Our analysis for this simplified setup aims at showing the potential of mismatched decoding as a tool to design and analyze transmission strategies for short blocks. We focus on a pragmatic approach where the transmission frame contains a codeword as well as a preamble that is used to estimate the channel (the codeword symbols are not used for channel estimation). Achievability and converse bounds on the block error probability achievable by this approach are provided and compared with simulation results for schemes employing short low-density parity-check codes. Our bounds turn out to predict accurately the optimal trade-off between the preamble length and the redundancy introduced by the channel code.
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| 46. |
- Popovski, Petar, et al.
(författare)
-
5G wireless network slicing for eMBB, URLLC, and mMTC: A communication-theoretic view
- 2018
-
Ingår i: IEEE Access. - 2169-3536 .- 2169-3536. ; 6, s. 55765-55779
-
Tidskriftsartikel (refereegranskat)abstract
- The grand objective of 5G wireless technology is to support three generic services with vastly heterogeneous requirements: enhanced mobile broadband (eMBB), massive machine-type communications (mMTCs), and ultra-reliable low-latency communications (URLLCs). Service heterogeneity can be accommodated by network slicing, through which each service is allocated resources to provide performance guarantees and isolation from the other services. Slicing of the radio access network (RAN) is typically done by means of orthogonal resource allocation among the services. This paper studies the potential advantages of allowing for non-orthogonal sharing of RAN resources in uplink communications from a set of eMBB, mMTC, and URLLC devices to a common base station. The approach is referred to as heterogeneous non-orthogonal multiple access (H-NOMA), in contrast to the conventional NOMA techniques that involve users with homogeneous requirements and hence can be investigated through a standard multiple access channel. The study devises a communication-theoretic model that accounts for the heterogeneous requirements and characteristics of the three services. The concept of reliability diversity is introduced as a design principle that leverages the different reliability requirements across the services in order to ensure performance guarantees with non-orthogonal RAN slicing. This paper reveals that H-NOMA can lead, in some regimes, to significant gains in terms of performance tradeoffs among the three generic services as compared to orthogonal slicing.
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| 47. |
- Sac, Hakan, et al.
(författare)
-
Age-Optimal Channel Coding Blocklength for an M/G/1 Queue with HARQ
- 2018
-
Ingår i: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2018-June
-
Konferensbidrag (refereegranskat)abstract
- We consider a communication system in which a source transmits information updates to a destination node through a binary erasure channel (BEC). When a packet containing an information update, which consists of a fixed number of information bits, arrives at the transmitter, it gets queued in a buffer, to be encoded and sent over the channel. Before transmitting a packet, the transmitter selects a channel coding blocklength n and then uses an automatic repeat request (ARQ) protocol, whereby packets that are decoded incorrectly are repeated. The choice of the coding blocklength thus affects the end-to-end status age. However, this dependency is nontrivial since, on the one hand, the duration of a single transmission attempt is directly proportional to n, so the smaller n the better. On the other hand, a smaller value of the blocklength n yields a higher probability of decoding error, which increases the end-to-end status age. Employing recent finite-blocklength information-theoretic bounds and approximations on the rate achievable on a BEC for a given blocklength and a given error probability, we study the age-optimal design of this system. We find that for any nontrivial BEC, there exists an optimal blocklength that minimizes the average age and average peak age of information.
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| 48. |
- Scarlett, Jonathan, 1990, et al.
(författare)
-
The dispersion of nearest-neighbor decoding for additive non-Gaussian channels
- 2017
-
Ingår i: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 63:1, s. 81-92
-
Tidskriftsartikel (refereegranskat)abstract
- We study the second-order asymptotics of information transmission using random Gaussian codebooks and nearest neighbor decoding over a power-limited stationary memoryless additive non-Gaussian noise channel. We show that the dispersion term depends on the non-Gaussian noise only through its second and fourth moments, thus complementing the capacity result (Lapidoth, 1996), which depends only on the second moment. Furthermore, we characterize the second-order asymptotics of point-to-point codes over K -sender interference networks with non-Gaussian additive noise. Specifically, we assume that each user's codebook is Gaussian and that NN decoding is employed, i.e., that interference from the K-1 unintended users (Gaussian interfering signals) is treated as noise at each decoder. We show that while the first-order term in the asymptotic expansion of the maximum number of messages depends on the power of the interfering codewords only through their sum, this does not hold for the second-order term.
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| 49. |
- Scarlett, Jonathan, 1990, et al.
(författare)
-
The Dispersion of Nearest-Neighbor Decoding for Additive Non-Gaussian Channels
- 2016
-
Ingår i: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2016-August, s. 2664-2668
-
Konferensbidrag (refereegranskat)abstract
- We study the second-order asymptotics of information transmission using random Gaussian codebooks and nearest neighbor (NN) decoding over a power-limited additive stationary memoryless non-Gaussian channel. We show that the dispersion term depends on the non-Gaussian noise only through its second and fourth moments. We also characterize the second-order performance of point-to-point codes over Gaussian interference networks. Specifically, we assume that each user’s codebook is Gaussian and that NN decoding is employed, i.e., that interference from unintended users is treated as noise at each decoder.
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- Studer, Christoph, et al.
(författare)
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Quantized Massive MU-MIMO-OFDM Uplink
- 2016
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Ingår i: IEEE Transactions on Communications. - 0090-6778 .- 1558-0857. ; 64:6, s. 2387-2399
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Tidskriftsartikel (refereegranskat)abstract
- Coarse quantization at the base station (BS) of a massive multi-user (MU) multiple-input multiple-output (MIMO) wireless system promises significant power and cost savings. Coarse quantization also enables significant reductions of the raw analog-to-digital converter data that must be transferred from a spatially separated antenna array to the baseband processing unit. The theoretical limits as well as practical transceiver algorithms for such quantized MU-MIMO systems operating over frequency-flat, narrowband channels have been studied extensively. However, the practically relevant scenario where such communication systems operate over frequency-selective, wideband channels is less well understood. This paper investigates the uplink performance of a quantized massive MU-MIMO system that deploys orthogonal frequency-division multiplexing (OFDM) for wideband communication. We propose new algorithms for quantized maximum a posteriori channel estimation and data detection, and we study the associated performance/quantization tradeoffs. Our results demonstrate that coarse quantization (e.g., four to six bits, depending on the ratio between the number of BS antennas and the number of users) in massive MU-MIMO-OFDM systems entails virtually no performance loss compared with the infinite-precision case at no additional cost in terms of baseband processing complexity.
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