In non-volatile random-access memory (RAM) technologies, the spin-torque transfer magnetic random-access memory (STT-MRAM) is a promising candidate. STT-MRAM has attracted attention owing to its advantages, such as a ...
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In non-volatile random-access memory (RAM) technologies, the spin-torque transfer magnetic random-access memory (STT-MRAM) is a promising candidate. STT-MRAM has attracted attention owing to its advantages, such as a high density, high endurance, and high-speed writing/reading. Moreover, STT-MRAM is utilized to replace dynamic random-access memory (DRAM) in Internet of Things (IoT) and artificial intelligence (AI) applications. However, because the magnetic tunnel junction is used to write data, STT-MRAM must face process variation and thermal fluctuation problems. This causes errors in writing and reading processes. These errors are independent of each other. Therefore, to solve them and increase the reliability of STT-MRAM, the data are encoded before storage in STT-MRAM devices. In this study, we propose a method for designing codewords using modulation coding techniques. Our codewords increase the minimum Hamming distance and inheritance of the sparse code characteristic to exploit the asymmetric probability of the write errors. The simulation results show that our codewords can improve the bit error rate performance of STT-MRAM compared with previous works.
Here, the authors consider the uplink of a cellular massive multiple-input multiple-output (MIMO) system with maximum ratio combiner (MRC) at base stations (BSs). To achieve a better QoS provisioning, users in the cel...
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Here, the authors consider the uplink of a cellular massive multiple-input multiple-output (MIMO) system with maximum ratio combiner (MRC) at base stations (BSs). To achieve a better QoS provisioning, users in the cells employ link adaptation using adaptive modulation and coding (AMC) in conjunction with packet retransmission. The authors present a cross-layer approach for the AMC design exploiting the time variation feature of MIMO wireless channels. At first, a fast AMC (FAMC) scheme is proposed to adapt the fast small-scale fading of the wireless channel based on the instantaneous channel state information. Since the fast fading is asymptotically averaged out due to the channel hardening property of massive MIMO system, we then suggest a slow AMC (SAMC) scheme which adjusts the adaptation parameters based on only the large-scale channel fading statistics including shadow fading and pass loss of the channel. The SAMC substantially reduces the feedback rate and implementation cost because of using a larger coherence time compared to that of the FAMC. For the proposed schemes, the probability density function of signal-to-interference-plus-noise ratio (SINR) for MRC receivers at BSs is analytically derived and verified by simulation. Also, closed-form expressions are presented for the throughput and packet error outage of the system. Index Terms-Massive MIMO, MRC, AMC, ARQ, Performance analysis.
The principal target of this study is to enhance the performance of the 4-level holographic data storage (HDS) systems by using a well-suited modulation code scheme. The HDS system is one of the most promising approac...
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ISBN:
(数字)9781728180656
ISBN:
(纸本)9781728180656
The principal target of this study is to enhance the performance of the 4-level holographic data storage (HDS) systems by using a well-suited modulation code scheme. The HDS system is one of the most promising approaches for storing massive digital data for the next-generation optical data storage systems. However, the performance of retrieving data in the HDS system is severely affected by fatal interference (FI) patterns. The proposed coding design aims to get rid of all FI patterns during the recording procedure with reasonable computational complexity.
The queuing performance of the cross-layer system with Space-time block code (STBC) over Multi-input-multi-output (MIMO) channel is analyzed. The Adaptive modulation and coding (AMC) in physical layer and finite lengt...
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The queuing performance of the cross-layer system with Space-time block code (STBC) over Multi-input-multi-output (MIMO) channel is analyzed. The Adaptive modulation and coding (AMC) in physical layer and finite length of buffer in data-link layer are combined with this model. A simple cross-layer design and the queue state process are proposed based on finite state Markov channel model, which is to solve the service process. The proposed cross-layer design is also incorporated with STBC to further improve the system performance. Simulation results illustrate the dependence of system performance on various parameters, and quantify the performance gain due to cross-layer optimization. The adjustment of target packet loss rate of adaptive modulation coding in physical layer can maximize average throughput of the system, meanwhile a significant improvement of the system performance is brought.
An adaptive modulation and coding (AMC) scheme based on a Moore state machine is proposed for the high-speed railway communication systems. By setting a buffer zone for the signal-to-noise ratio threshold value, the p...
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An adaptive modulation and coding (AMC) scheme based on a Moore state machine is proposed for the high-speed railway communication systems. By setting a buffer zone for the signal-to-noise ratio threshold value, the proposed scheme is able to reduce the frequent transition of the modulation and coding scheme. Simulation results show that the proposed AMC strategy has a more stable spectral efficiency than the traditional AMC method using a piecewise function.
Inter-satellite link (ISL) will play an increasingly important role in the next generation of global navigation satellite system (GNSS). The inter-satellite distances in the GNSS vary greatly, resulting in a power los...
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Inter-satellite link (ISL) will play an increasingly important role in the next generation of global navigation satellite system (GNSS). The inter-satellite distances in the GNSS vary greatly, resulting in a power loss difference of as much as 20 db. However, there are no reports on promotion of spectral efficiency in inter-satellite channels at present. In this study, the authors propose an efficient utilisation of the adaptive modulation and coding (AMC) scheme for ISLs in the GNSS. A novel method, based on inter-satellite distance, is presented for choosing the modulation and coding scheme (MCS). The proposed method provides a convenient way to estimate signal-to-noise ratio of the ISLs in GNSS. This AMC technique is implemented according to two different algorithms. One is the target bit error rate (BER) algorithm based on inter-satellite distance, aimed at keeping the BER below a target limit. The other is the maximum throughput algorithm based on inter-satellite distance, aimed at maximising the data throughput. In cases where the inter-satellite distance is short, simulation results show that, under the premise of the same transmission power, the throughput of two proposed AMC schemes is nearly six times that of a fixed MCS.
Communication and computation are traditionally treated as separate entities, allowing for individual optimizations. However, many applications focus on local information's functionality rather than the informatio...
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Communication and computation are traditionally treated as separate entities, allowing for individual optimizations. However, many applications focus on local information's functionality rather than the information itself. For such cases, harnessing interference for computation in a multiple access channel through digital over-the-air computation can notably increase the computation, as established by the ChannelComp method. However, the coding scheme originally proposed in ChannelComp may suffer from high computational complexity because it is general and is not optimized for specific modulation categories. Therefore, this study considers a specific category of digital modulations for over-the-air computations, quadrature amplitude modulation (QAM) and pulse-amplitude modulation (PAM), for which we introduce a novel coding scheme called SumComp. Furthermore, we derive a mean squared error (MSE) analysis for SumComp coding in the computation of the arithmetic mean function and establish an upper bound on the mean absolute error (MAE) for a set of nomographic functions. Simulation results are presented to affirm the superior performance of SumComp coding compared to traditional analog over-the-air computation and the original coding in ChannelComp approaches in terms of both MSE and MAE over a noisy multiple access channel. Specifically, SumComp coding shows at least 10 dB improvements for computing arithmetic and geometric mean on the normalized MSE for low noise scenarios.
Fluid antenna multiple access (FAMA) is a concept capable of massive connectivity on the same physical channel without the need of precoding or interference cancellation, by exploiting a super-high dimensional receive...
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Fluid antenna multiple access (FAMA) is a concept capable of massive connectivity on the same physical channel without the need of precoding or interference cancellation, by exploiting a super-high dimensional received signal in the spatial domain from fluid antenna system (FAS). This letter investigates the use of 5G New Radio (NR) modulation coding Scheme (MCS) for FAMA systems to improve its connectivity over block fading channels. In particular, an iterative decoding receiver with iterative interference covariance estimation is proposed, designed explicitly for slow fading channels. Extrinsic information transfer (EXIT) chart is used to analyze the performance of the proposed iterative receiver. Both EXIT chart analysis and numerical results indicate that the proposed receiver outperforms the existing approach that uses fixed covariance in block fading channels. Also, the results indicate that coded FAMA can serve 100 user terminals (UTs) at the rate of 0.5 bit/s/Hz under rich scattering.
This paper discusses an extended modulation mapping technique to improve hybrid automatic repeat request (ARQ) protocols by reducing communication errors in wireless systems. The extended mapping (EM) hybrid ARQ (HARQ...
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This paper discusses an extended modulation mapping technique to improve hybrid automatic repeat request (ARQ) protocols by reducing communication errors in wireless systems. The extended mapping (EM) hybrid ARQ (HARQ) protocol has been developed using irregular repetition code with turbo processing. This protocol uses EM and ARQ to improve efficiency, including retransmission for error correction. The existing hybrid ARQ technique uses a horizontal iterative decoding scheme to reduce error. The suggested method employs both serial and parallel iterative decoding schemes for error detection and correction. A bit error rate (BER) analysis evaluates the proposed model, EM-HARQ performance in the additive white Gaussian noise channel. The results show a significant gain in signal-to-noise ratio (SNR) from the theoretical limit of the irregular repetition coding using MATLAB simulation software. The adoption of EM in the proposed method improves the SNR to a 0.99 dB performance gap difference and 0.3 dB performance gain due to enhanced error detection. Even with low SNR channels, the proposed EM-HARQ system can achieve a low BER and close to the theoretical limit capacity.
In previous studies of ghost imaging transmission methods, the influence of real transmission channel on communication quality is weakened to a certain extent. Therefore, in this letter, a channel transmission model i...
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In previous studies of ghost imaging transmission methods, the influence of real transmission channel on communication quality is weakened to a certain extent. Therefore, in this letter, a channel transmission model in real scenes (Rayleigh fading channel) is introduced. By leveraging the ultra-strong anti-noise capability and weak-signal imaging characteristics of ghost imaging, we explore ways to enhance the transmission of information while minimizing channel interference. Through the analysis of metrics such as bit error rate (BER), structural similarity (SSIM) and peak signal-to-noise ratio (PSNR), the proposed method effectively addresses issues like low restoration accuracy and limited feasibility of current transmission imaging methods, providing a new imaging technology for the research in the field of image transmission and holding significant theoretical value.
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