| 1. |
- Kislal, Ahmet Oguz, 1993, et al.
(author)
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Efficient evaluation of the error probability for pilot-assisted finite-blocklength transmission
- 2022
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In: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2022-October, s. 1038-1044
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Conference paper (peer-reviewed)abstract
- We propose a numerically efficient method for evaluating the random-coding union bound with parameter s on the error probability achievable in the finite-blocklength regime by a pilot-assisted transmission scheme employing Gaussian code-books and operating over a memoryless block-fading channel. Our method relies on the saddlepoint approximation, which, differently from previous results reported for similar scenarios, is performed with respect to the number of fading blocks (a.k.a. diversity branches) spanned by each codeword, instead of the number of channel uses per block. This different approach avoids a costly numerical averaging of the error probability over the realizations of the fading process and of its pilot-based estimate at the receiver and yields a significant reduction of the number of channel realizations required to estimate the error probability via Monte-Carlo simulation. For example, in a single-input single-output scenario, when four or more diversity branches are available, an error probability of 10-4can be estimated accurately using our method by using less than 3000 samples. In contrast, the conventional saddlepoint approach requires around 106samples.
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| 2. |
- Kislal, Ahmet Oguz, 1993, et al.
(author)
-
Efficient evaluation of the error probability for pilot-assisted URLLC with Massive MIMO
- 2023
-
In: IEEE Journal on Selected Areas in Communications. - 0733-8716 .- 1558-0008. ; 41:7, s. 1969-1981
-
Journal article (peer-reviewed)abstract
- We propose a numerically efficient method for evaluating the random-coding union bound with parameter s on the error probability achievable in the finite-blocklength regime by a pilot-assisted transmission scheme employing Gaussian code-books and operating over a memoryless block-fading channel. Our method relies on the saddlepoint approximation, which, differently from previous results reported for similar scenarios, is performed with respect to the number of fading blocks (a.k.a. diversity branches) spanned by each codeword, instead of the number of channel uses per block. This different approach avoids a costly numerical averaging of the error probability over the realizations of the fading process and of its pilot-based estimate at the receiver and results in a significant reduction of the number of channel realizations required to estimate the error probability accurately. Our numerical experiments for both single-antenna communication links and massive multiple-input multiple-output (MIMO) networks show that, when two or more diversity branches are available, the error probability can be estimated accurately with the saddlepoint approximation with respect to the number of fading blocks using a numerical method that requires about two orders of magnitude fewer Monte-Carlo samples than with the saddlepoint approximation with respect to the number of channel uses per block.
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| 3. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
A Finite-Blocklength Analysis for URLLC with Massive MIMO
- 2021
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In: IEEE International Conference on Communications. - 1550-3607. ; June 2021
-
Conference paper (peer-reviewed)abstract
- This paper presents a rigorous finite-blocklength framework for the characterization and the numerical evaluation of the packet error probability achievable in the uplink and downlink of Massive MIMO for ultra-reliable low-latency communications (URLLC). The framework encompasses imperfect channel-state information, pilot contamination, spatially correlated channels, and arbitrary linear signal processing. For a practical URLLC network setup involving base stations with M = 100 antennas, we show by means of numerical results that a target error probability of 10-5 can be achieved with MMSE channel estimation and multicell MMSE signal processing, uniformly over each cell, only if orthogonal pilot sequences are assigned to all the users in the network. For the same setting, an alternative solution with lower computational complexity, based on least-squares channel estimation and regularized zero-forcing signal processing, does not suffice unless M is increased significantly.
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| 4. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
Cell-Free Massive MIMO for URLLC: A Finite-Blocklength Analysis
- 2023
-
In: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 22:12, s. 8723-8735
-
Journal article (peer-reviewed)abstract
- We present a general framework for the characterization of the packet error probability achievable in cell-free Massive multiple-input multiple output (MIMO) architectures deployed to support ultra-reliable low-latency (URLLC) traffic. The framework is general and encompasses both centralized and distributed cell-free architectures, arbitrary fading channels and channel estimation algorithms at both network and user-equipment (UE) sides, as well as arbitrary combing and precoding schemes. The framework is used to perform numerical experiments on specific scenarios, which illustrate the superiority of cell-free architectures compared to cellular architectures in supporting URLLC traffic in uplink and downlink. Also, these numerical experiments provide the following insights into the design of cell-free architectures for URLLC: i) minimum mean square error (MMSE) spatial processing must be used to achieve the URLLC targets; ii) for a given total number of antennas per coverage area, centralized cell-free solutions involving single-antenna access points (APs) offer the best performance in the uplink, thereby highlighting the importance of reducing the average distance between APs and UEs in the URLLC regime; iii) this observation applies also to the downlink, provided that the APs transmit precoded pilots to allow the UEs to estimate accurately the precoded channel.
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| 5. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
Cell-free Massive MIMO with Short Packets
- 2021
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In: IEEE Workshop on Signal Processing Advances in Wireless Communications, SPAWC. ; 2021-September, s. 416-420
-
Conference paper (peer-reviewed)abstract
- In this paper, we adapt to cell-free Massive MIMO (multiple-input multiple-output) the finite-blocklength framework introduced by Ostman et al. (2020) for the charac- ¨ terization of the packet error probability achievable with Massive MIMO, in the ultra-reliable low-latency communications (URLLC) regime. The framework considered in this paper encompasses a cell-free architecture with imperfect channelstate information, and arbitrary linear signal processing performed at a central-processing unit connected to the access points via fronthaul links. By means of numerical simulations, we show that, to achieve the high reliability requirements in URLLC, MMSE signal processing must be used. Comparisons are also made with both small-cell and Massive MIMO cellular networks. Both require a much larger number of antennas to achieve comparable performance to cell-free Massive MIMO.
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| 6. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
Finite-Blocklength Approximations for Noncoherent Rayleigh Block-Fading Channels
- 2019
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In: Conference Record - Asilomar Conference on Signals, Systems and Computers. - 1058-6393. ; 2019, s. 815-819
-
Conference paper (peer-reviewed)abstract
- Several emerging wireless communication services and applications have stringent latency requirements, necessitating the transmission of short packets. To obtain performance benchmarks for short-packet wireless communications, it is crucial to study the maximum coding rate as a function of the blocklength, commonly called finite-blocklength analysis. A finiteblocklength analysis can be performed via nonasymptotic bounds or via refined asymptotic approximations. This paper reviews finite-blocklength approximations for the noncoherent Rayleigh block-fading channel. These approximations have negligible computational cost compared to the nonasymptotic bounds and are shown to be accurate for error probabilities as small as 10^-8 and SNRs down to 0 dB.
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| 7. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
On Joint Detection and Decoding in Short-Packet Communications
- 2021
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In: Proceedings - IEEE Global Communications Conference, GLOBECOM. - 2334-0983 .- 2576-6813.
-
Conference paper (peer-reviewed)abstract
- We consider a communication problem in which the receiver must first detect the presence of an information packet and, if detected, decode the message carried within it. We present general nonasymptotic upper and lower bounds on the maximum coding rate that depend on the blocklength, the probability of false alarm, the probability of misdetection, and the packet error probability. The bounds, which are expressed in terms of binary-hypothesis-testing performance metrics, generalize finiteblocklength bounds derived previously for the scenario when a genie informs the receiver whether a packet is present. The bounds apply to detection performed either jointly with decoding on the entire data packet, or separately on a dedicated preamble. The results presented in this paper can be used to determine the blocklength values at which the performance of a communication system is limited by its ability to perform packet detection satisfactorily, and to assess the difference inperformance between preamblebased detection, and joint detection and decoding. Numerical results pertaining to the binary-input AWGN channel are provided.
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| 8. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
On single-antenna Rayleigh block-fading channels at finite blocklength
- 2020
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In: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 66:1, s. 496-519
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Journal article (peer-reviewed)abstract
- This article concerns the maximum coding rate at which data can be transmitted over a noncoherent, 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. A high-SNR normal approximation of the maximum coding 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 at SNR values above 15dB and when the number of coherence intervals is 10 or more.
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| 9. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
Saddlepoint Approximations for Noncoherent Single-Antenna Rayleigh Block-Fading Channels
- 2019
-
In: IEEE International Symposium on Information Theory - Proceedings. - 2157-8095. ; 2019-July, s. 612-616
-
Conference paper (peer-reviewed)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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| 10. |
- Lancho Serrano, Alejandro, 1991, et al.
(author)
-
Saddlepoint Approximations for Short-Packet Wireless Communications
- 2020
-
In: IEEE Transactions on Wireless Communications. - 1558-2248 .- 1536-1276. ; 19:7, s. 4831-4846
-
Journal article (peer-reviewed)abstract
- In recent years, the derivation of nonasymptotic converse and achievability bounds on the maximum coding rate as a function of the error probability and blocklength has gained attention in the information theory literature. While these bounds are accurate for many scenarios of interest, they need to be evaluated numerically for most wireless channels of practical interest, and their evaluation is computationally demanding. 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 and blocklengths of 168 channel uses or more.
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