260 research outputs found
Finite Block-Length Analysis of the Incremental Redundancy HARQ
No full textThis letter studies the power-limited throughput of a communication system utilizing incremental redundancy (INR) hybrid automatic repeat request (HARQ). We use some recent results on the achievable rates of finite-length codes to analyze the system performance. With codewords of finite length, we derive closed-form expressions for the outage probabilities of INR HARQ and study the throughput in the cases with variable-length coding. Moreover, we evaluate the effect of feedback delay on the throughput and derive sufficient conditions for the usefulness of the HARQ protocols, in terms of power-limited throughput. The results show that, for a large range of HARQ feedback delays, the throughput is increased by finite-length coding INR HARQ, if the sub-codeword lengths are properly adapted
Finite block-length analysis of spectrum sharing networks
No full textThis paper studies the throughput of spectrum sharing networks utilizing rate adaptation. We use some recent results on the achievable rates of finite block-length codes to analyze the secondary user (SU) throughput with a constraint on the primary user (PU) codeword drop probability. With codewords of finite length, we derive closed-form expressions for the SU activation probability and throughput. The results are obtained in different scenarios with no channel state information at the SU transmitter. As demonstrated numerically and analytically, using finite-length codewords there is considerable potential for the data transmission of unlicensed secondary users under different quality-of-service requirements of the licensed primary users
Green communication via Type-I ARQ: Finite block-length analysis
No full textThis paper studies the effect of optimal power allocation on the performance of communication systems utilizing automatic repeat request (ARQ). Considering Type-I ARQ, the problem is cast as the minimization of the outage probability subject to an average power constraint. The analysis is based on some recent results on the achievable rates of finite-length codes and we investigate the effect of codewords length on the performance of ARQ-based systems. We show that the performance of ARQ protocols is (almost) insensitive to the length of the codewords, for codewords of length ≥ 50 channel uses. Also, optimal power allocation improves the power efficiency of the ARQ-based systems substantially. For instance, consider a Rayleigh fading channel, codewords of rate 1 nats-per-channel-use and outage probability 10-3. Then, with a maximum of 2 and 3 transmissions, the implementation of power-adaptive ARQ reduces the average power, compared to the open-loop communication setup, by 17 and 23 dB, respectively, a result which is (almost) independent of the codewords length. Also, optimal power allocation increases the diversity gain of the ARQ protocols considerably
Wireless Energy and Information Transmission using Feedback: Infinite and Finite Block-length Analysis
No full textIn this paper, we propose and analyze a wireless energy and information transfer system. To reduce the outage probability, compared to open-loop communication, we implement retransmission protocols both in the energy and in the information transmission phases. We use some recent results on finite block-length codes, to analyze the effect of the energy and information signals lengths on the system outage probability/throughput. Finally, under a packet transmission delay constraint, we derive the optimal power allocation and time sharing between the energy and information signals such that the energy-constrained outage probability is minimized. The simulation and analytical results demonstrate that the retransmission-based protocols are efficient techniques to reduce the energy-limited outage probability of wireless energy and information transmission systems
Finite Block-Length Analysis of Spectrum Sharing Networks: Interference-Constrained Scenario
No full textThis letter studies the interference-constrained performance of spectrum sharing networks using adaptive power allocation. The throughput of the secondary user is derived in different cases with constraints on the primary user average or instantaneous received interference power. The analysis is based on some recent results on the achievable rates of finite-length codes and shows the effect of the codeword length on the performance of spectrum sharing networks. The results indicate that, with codewords of finite length and different primary user's interference constraints, there is potential for spectrum sharing, if the transmission power is properly adapted
Finite Block-Length Analysis of Spectrum Sharing Networks Using Rate Adaptation
No full textThis paper studies the throughput of spectrum sharing networks utilizing rate adaptation. We use some recent results on the achievable rates of finite block-length codes to analyze the secondary user (SU) throughput with a constraint on the primary user (PU) codeword drop probability. With codewords of finite length, we derive closed-form expressions for the SU activation probability and throughput. The results are obtained in different scenarios with perfect or no channel state information at the SU transmitter. As demonstrated numerically and analytically, using finite-length codewords and rate adaptation, there is considerable potential for the data transmission of unlicensed secondary users under different quality-of-service requirements of the licensed primary users
A joint power and information transfer system using retransmissions
No full textIn this paper, we develop a green joint power and information transfer system. To guarantee reliable communication, we implement hybrid automatic repeat request (HARQ) feedback both in the power and information transmission phases. Moreover, with a limit on the packet transmission delay, we derive the optimal power allocation minimizing the energy-constrained outage probability. The simulation and analytical results indicate that the diversity gain of the joint power and information transfer system is the same as the diversity gain of the conventional non-green information transfer systems. Also, the implementation of HARQ improves the power efficiency significantly. For instance, consider a Rayleigh fading channel, outage probability 10-3, code rate 1 nats-per-channel-use and the case where the receiver requires to receive 0.1 Joule-per-channel-use energy per codeword length from the transmitter to process the information. Then, with a maximum of two retransmissions in the power and information transfer phases, the HARQ reduces the average required energy by 4 dB, compared to the open-loop communication setup
Fast HARQ over Finite Blocklength Codes: A Technique for Low-Latency Reliable Communication
No full textThis paper studies the performance of delay-constrained hybrid automatic repeat request (HARQ) protocols. Particularly, we propose a fast HARQ protocol where, to increase the end-to-end throughput, some HARQ feedback signals and successive message decodings are omitted. Considering quasi-static channels and a bursty communication model, we derive closed-form expressions for the message decoding probabilities as well as the throughput, the expected delay, and the error probability of the HARQ setups. The analysis is based on the recent results on the achievable rates of finite-length codes and shows the effect of the codeword length on the system performance. Moreover, we evaluate the effect of various parameters, such as imperfect channel estimation and hardware on the system performance. As demonstrated, the proposed fast HARQ protocol reduces the packet transmission delay considerably compared with the state-of-the-art HARQ schemes. For example, with typical message decoding delay profiles and a maximum of 2,..., 5 transmission rounds, the proposed fast HARQ protocol can improve the expected delay compared with standard HARQ by 27%, 42%, 52%, and 60%, respectively, independently of the code rate/fading model
Delay-Sensitive Area Spectral Efficiency: A Performance Metric for Delay-Constrained Green Networks
No full textThis paper introduces a new metric, referred to as delay-sensitive area spectral efficiency (DASE), to analyze the performance of delay-constrained wireless networks. We study DASE in different point-to-point, spectrum sharing, interference, and Poisson-point process-based dense network configurations and with different levels of channel state information (CSI) at the transmitters. Also, we determine the optimal rates/powers optimizing DASE. Finally, we use some recent results on finite block-length codes to analyze the effect of the codewords length on the network DASE. As demonstrated, DASE is a useful metric for analyzing delay-sensitive green networks. Moreover, adaptive power allocation and partial CSI feedback are powerful tools for performance improvement in green networks
Mapping Middle-earth : Environmental and Political Narratives in J.R. R. Tolkien’s Cartographies (2024) by Anahit Behrooz
No full textThe force driving Anahit Behrooz’s Mapping Middle-earth is a desire todemonstrate that J. R. R. Tolkien’s work deserves to be taken (more) seriouslyin the field of literary studies. The author argues this case by relating maps,mapping, and cartography – within and outside the story world – to a handfulof critical perspectives that currently enjoy certain appeal both within themainstream and among fantasy scholars. And should the book fail to convincesome hobbitophobic critics out there, the fault does not seem to lie either withTolkien’s work or Behrooz discussions of it but with the fact that fantasy(including Tolkien) require more of its analytical tools than some mainstreamcritical perspectives offer when taken off the rack
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