Electrocardiogram (ECG) signals play a crucial role in diagnosing cardiovascular diseases. To reduce power consumption in wearable or portable devices used for long-term ECG monitoring, super-resolution (SR) techniques have been developed, enabling these devices to collect and transmit signals at a lower sampling rate. In this study, we propose MSECG, a compact neural network model designed for ECG SR. MSECG combines the strength of the recurrent Mamba model with convolutional layers to capture both local and global dependencies in ECG waveforms, allowing for the effective reconstruction of high-resolution signals. We also assess the model’s performance in real-world noisy conditions by utilizing ECG data from the PTB-XL database and noise data from the MIT-BIH Noise Stress Test Database. Experimental results show that MSECG outperforms two contemporary ECG SR models under both clean and noisy conditions while using fewer parameters, offering a more powerful and robust solution for long-term ECG monitoring applications.

Surface electromyography (sEMG) recordings can be contaminated by electrocardiogram (ECG) signals when the monitored muscle is closed to the heart. Traditional signal processing-based approaches, such as high-pass filtering and template subtraction, have been used to remove ECG interference but are often limited in their effectiveness. Recently, neural network-based methods have shown greater promise for sEMG denoising, but they still struggle to balance both efficiency and effectiveness. In this study, we introduce MSEMG, a novel system that integrates the Mamba state space model with a convolutional neural network to serve as a lightweight sEMG denoising model. We evaluated MSEMG using sEMG data from the Non-Invasive Adaptive Prosthetics database and ECG signals from the MIT-BIH Normal Sinus Rhythm Database. The results show that MSEMG outperforms existing methods, generating higher-quality sEMG signals using fewer parameters.

Surface electromyography (sEMG) is a widely employed bio-signal that captures human muscle activity via electrodes placed on the skin. Several studies have proposed methods to remove sEMG contaminants, as non-invasive measurements render sEMG susceptible to various contaminants. However, these approaches often rely on heuristic-based optimization and are sensitive to the contaminant type. A more potent, robust, and generalized sEMG denoising approach should be developed for various healthcare and human-computer interaction applications. This paper proposes a novel neural network (NN)-based sEMG denoising method called TrustEMG-Net. It leverages the potent nonlinear mapping capability and data-driven nature of NNs. TrustEMG-Net adopts a denoising autoencoder structure by combining U-Net with a Transformer encoder using a representation-masking approach. The proposed approach is evaluated using the Ninapro sEMG database with five common contamination types and signal-to-noise ratio (SNR) conditions. Compared with existing sEMG denoising methods, TrustEMG-Net achieves exceptional performance across the five evaluation metrics, exhibiting a minimum improvement of 20%. Its superiority is consistent under various conditions, including SNRs ranging from -14 to 2 dB and five contaminant types. An ablation study further proves that the design of TrustEMG-Net contributes to its optimality, providing high-quality sEMG and serving as an effective, robust, and generalized denoising solution for sEMG applications.

In time-slotted molecular communication systems, clock synchronization between transmitter and receiver is crucial. In this paper, training-based synchronization schemes in a molecular communication system with quantity-based modulation are proposed by utilizing the information of arrival times of molecules. For timing offset estimation, three estimators are proposed, including maximum likelihood estimation (MLE), unbiased linear estimation (ULE), and iterative ULE. For clock skew estimation, two algorithms, arithmetic mean estimation and weighted mean estimation, are proposed. Simulation results demonstrate that the proposed estimators are effective.

In molecular communication systems, information is conveyed via nanoscale particles or molecules. Traditionally, the distribution of the first arrival time to the receiver is considered for system design and evaluation if nanoscale particles or molecules are diffused from the transmitter to the receiver in diffusion-based molecular communication systems. In this paper, we consider an extra information in the diffusion-based molecular communication system, namely the first arrival position at the receiver. A mathematical framework is developed to obtain the closed-form density function of the first arrival position for particles/molecules diffusing under constant net drift. The derived density function not only provides a novel analytical framework for existing molecular communication systems but may inspire novel molecular communication system design.

Dramatic progress in nanotechnology has enabled nano-machines to perform basic functions of communication. To interconnect nano-machines, molecular communication is one of the most promising communication mechanisms, in which molecules are used to deliver information. However, compared to classical communication schemes, the reliability of molecular communication is often criticized due to the slow diffusion process and the inter-symbol interference (ISI). In this paper, we propose a low complexity receiver design for diffusion-based molecular communication to solve the ISI problem. We first derive the optimal receiver and then use the Poisson distribution to approximate the Poisson binomial distribution in order to obtain a receiver with lower complexity. The simulation results confirm the near-optimal performance of the proposed receiver design.

The advance in nanotechnology has enabled the fabrication of nanomachines for health applications. Recently, molecular communication has become a promising communication paradigm that allows nanomachines to exchange information by using messenger molecules in fluid environments. To enable molecular communications, the knowledge of distance between nanomachines is critical since the distance affects both the performance and the efficiency of molecular communication. However, works on molecular communication either assume the distance is known or the distance estimation is based on the assumption of clock synchronization between nanomachines. In this paper, we propose novel methods for distance estimation using only one-way transmission and requiring no clock synchronization between nanomachines. The noise of diffusion channel due to random walk of molecules is investigated and methods to effectively improve the estimation accuracy are proposed.

Due to the emergence of mmWave systems that provide multi-Gbps data rate over 60GHz band, uncompressed video transmission has been considered as a commonly used feature for wireless multimedia transmission over the wireless personal area networks (WPANs). However, mmWaves signals usually have higher attenuation than the conventional low-frequency wireless signals, and therefore supporting transmission in a low SNR condition becomes a challenging problem for such systems. In this paper, we propose a iterative decoding method for the wireless transmission of uncompressed video. With our proposed iterative decoding structure, the video decoder utilizes the temporal redundancy among the video frames to jointly decode the received coded bits from different video frames with the aid of correlation noise model. The simulation results show that the proposed method can significantly enhanced the video quality in terms of PSNR, even while operating in an extremely low SNR condition.

Molecular communications emerges as a promising scheme for communications between nanoscale devices. In diffusion-based molecular communications, molecules as information symbols diffusing in the fluid environments suffer from molecule crossovers, i.e., the arriving order of molecules is different from their transmission order, leading to intersymbol interference (ISI). In this paper, we introduce a new family of channel codes, called ISI-free codes, which improve the communication reliability while keeping the decoding complexity fairly low in the diffusion environment modeled by the Brownian motion. We propose general encoding/decoding schemes for the ISI-free codes, working upon the modulation schemes of transmitting a fixed number of identical molecules at a time. In addition, the bit error rate (BER) approximation function of the ISI-free codes is derived mathematically as an analytical tool to decide key factors in the BER performance. Compared with the uncoded systems, the proposed ISI-free codes offer good performance with reasonably low complexity for diffusion-based molecular communication systems.

In physical-layer security, secret bits are extracted from wireless channels. With the assumption of channel reciprocity, the legitimate users share the same channel which is independent of the channels between the legitimate users and the eavesdropper, leading to secure transmissions. However, practical implementation of the physical layer security faces many challenges. First, for the correlated channel such as the multiple-input and multiple-output (MIMO) channel, the security is decreased due to the correlation between the generated secret bits. Second, the nearby eavesdropper posts a security threat due to observing the same channel as the legitimate user's. Third, the eavesdroppers might try to reconstruct the wireless environments. In this paper, we propose two practical physical layer security schemes for the MIMO orthogonal frequency-division multiplexing (MIMO-OFDM) systems: the precoding matrix index (PMI)-based secret key generation with rotation matrix (MOPRO) and the channel quantization-based (MOCHA) scheme. The former utilizes PMI and rotated reference signals to prevent the eavesdroppers from learning the secret key information and the latter applies channel quantization in order to extract more secret key bits. It is shown that not only the secure communication but also the MIMO gain can be guaranteed by using the proposed schemes.

The emerging diffusion-based molecular communications is a promising scheme for nano-machine communications. Nevertheless, the Brownian motion model, which describes the behavior of molecules, makes the physical channel different from the channel in conventional wireless communications. In particular, the crossovers in time caused by the late arrivals of the molecules severely affect the communication reliability. In traditional communications, channel coding has long been used to enhance the reliability. Through our explorations, it is shown that the commonly used Hamming distance is no longer a good metric for the channel decoding in diffusion-based molecular communications. The conventional concepts of the channel code design cannot be straightforwardly applied. In this paper, the molecular coding (MoCo) distance function has been proposed, and shown to approach the optimum performance beyond the capability of using Hamming distance. This suggests that new paradigms can be developed upon the MoCo distance.

Diffusion-based molecular communications has becoming a promising approach for end-to-end communication between nano-machines. However, due to the randomness nature of molecule diffusions, the arriving time of each molecule is hard to predict and the late coming molecules will become a source of interference when doing detection. This effect will cause a severe degeneration of the system performance. Through our explorations, the conventional methods for mitigating the interference cannot be directly applied in these diffusion-based molecular communication environments. One of the main reasons is that the channel response is now time-variant. In this paper, we first apply Bayesian criterion to design an end-to-end communication system using quantity-based modulation (i.e. the information is imbedded in the number of molecules transmitted). Inspired by the idea of decision feedback in traditional communications, we propose an inter-symbol interference (ISI) cancellation approach. We also demonstrate the cancellation process based on our proposed quantity-based modulation system. Numerical results show that the proposed ISI cancellation method can help us achieve a reliable end-to-end transmission between nano-scale devices.

Communications based on diffusion refers to the transfer of information using molecules as message carriers whose propagation is governed by the laws of Brownian motion. Molecular communication is considered to be one of the most promising approaches for the end-to-end communication between nanoscale devices. In this paper, both an optimal and a suboptimal receiver detection scheme are proposed for a diffusionbased binary digital communication system in the presence of ISI. The transmission of binary information is accomplished by using On-Off Keying (OOK) with only one molecule. The proposed system can serve as the theoretical basis for end-to-end communication in molecular nanonetworks where molecules of different types are used by different nanoscale devices. The effect of channel memory resulting from the residual molecule diffusion from previous transmissions is treated analytically in the formulation of the detection schemes. Numerical results show that the proposed detection schemes can maximize the mutual information over a practical range of the parameter of signaling interval without a priori information. A channel capacity of 1 bit per channel utilization during a signaling interval can be ultimately achieved by extending the duration of the signaling interval, even with infinite channel memory.

Diffusion-based communication refers to the transfer of information using molecules as message carriers whose propagation is based on the law of molecular diffusion. Path loss can have a major impact on the link quality in molecular communication as the signal strength is shown inversely proportional to the cube of the communication distance. In this paper, various diversity techniques for Multi-Input Multi-Output (MIMO) transmissions based on molecular diffusion are proposed to improve the communication performance in nanonetworks in the presence of Multi-User Interference (MUI). Analogous to radio communication, the concept of diversity and Spatial Multiplexing (SM) can be successfully applied in molecular communication. To the best of our knowledge, our paper is the first which investigates the aspects of MIMO transmissions for molecular communication. Numerical results show that the proposed diversity techniques can successfully lower the error rate. Further performance improvement can be obtained by properly allocating molecules among the transmission nodes if the Channel State Information (CSI) is available at the transmitter end. To optimize the system throughput, a dynamic switching mechanism between the diversity mode and the Spatial Multiplexing (SM) mode can be employed.

Molecular communications emerges as a promising scheme for communication between nanoscale devices. In diffusion-based molecular communications, molecules as information symbols are released by transmitters and diffuse in the fluid or air environments to transmit messages. Under the diffusion channel modeled by Brownian motion, information sequences suffer from molecule crossovers, i.e., molecules released at an earlier time may arrive later, causing intersymbol interference (ISI). In this paper, we investigate practical channel codes for combating ISI. An ISI-free coding scheme is proposed to increase the communication reliability while keeping the encoding/decoding complexity reasonably low. We exemplify an ISI-free code and theoretically approximate its bit error rate (BER) performance. In addition, repetition codes are revisited out of the complexity concern and proved to be desirable. The BER approximations of the repetition code family are given as well. Compared with convolutional codes, the proposed ISI-free code and repetition codes offer comparable performance with much lower complexity for diffusion-based molecular communication systems.

Molecular communications emerge as a promising paradigm for the nano-scale communication in nanotechnology. Though still at an early stage, some research efforts have been made and various molecular communication systems have been proposed. However, existing works mainly focus on the synchronous communication schemes where the synchronous assumption is made for simplifying analyses. In this paper, we propose an asynchronous communication scheme for molecular communications. For the proposed scheme, we make extensive analyses and develop an approximation for channel capacity as a general performance measure which also applies to synchronous systems. Beyond the theoretical analysis, we also examine a specific asynchronous system and compare its performance with synchronous systems to confirm the feasibility of asynchronous molecular communications.

Diffusion-based communications refers to the transfer of information using particles as message carriers whose propagation is based on the law of particle diffusion. Though still at an early stage, there have been growing interests and research efforts dedicated to this communication technology. It has been identified that diffusion-based communications is one of the most promising approaches for end-to-end communication between nanoscale devices in the near future. In this paper, the design of a binary digital communication system is proposed based on particle diffusion. Stochastic signaling through On-Off Keying (OOK) for random particle emission and a diffusion channel with memory is considered. The diffusion is considered in the cases of one, two, and three dimensions. The receiver detection problem is formulated by using an information-theoretic approach. The optimal decision threshold for the receiver detection is derived through mutual information maximization for two cases, namely, when the a priori probability of bit transmission is fixed and known to the receiver and when this probability is unknown to the receiver. Numerical results indicate that in the case of diffusion in one or two dimensions, the information of a priori probability plays a key role in optimizing the system performance, while it does not when considering the diffusion in three dimensions.

In recent years, a number of rate-distortion (R-D) optimization schemes have been proposed. These works discussed the joint source-channel rate allocation problem for achieving best end-to-end video transmission quality under limited transmission bit rate. However, encoding complexity, a critical concern for video transmission from mobile devices, was hardly considered. Especially, the time-varying nature of computational resources for mobile devices was largely ignored. In this paper, an on-line adaptive video encoder parameters control scheme is proposed. Simulation results show that the proposed scheme, by dynamically adjusting the encoder parameters in H.264 using the precomputed rate-complexity-distortion (R-C-D) tables, achieves low end-to-end distortion under time-varying channel condition and dynamic computational complexity constraints.

Instant messaging (IM) services enable real-time text and multimedia exchange and online presence awareness. Users typically log onto instant messaging services persistently to discover available friends and also to be discovered. However, our analysis shows that the frequency exchange of presence information incurs massive power consumption to mobile devices over cellular or wireless local area networks. Such power consumption penalty can render persistent-instant messaging infeasible for battery-powered mobile devices. In this paper, we propose several solutions to mitigate the power consumption problem. By reducing the network access and keeping mobile devices in the sleep mode as much as possible, these solutions achieve significant power saving. The power consumption of the proposed solutions is derived analytically in this paper and the proposed solutions are implemented using a Jabber-based architecture. Actual power measurement results show that the power consumption of the proposed solutions agrees well with our analysis, and significant power saving can be achieved on mobile handsets with our low power consumption solutions implemented.

The multicast/broadcast service (MBS) has emerged as a key technology for delivering multimedia contents in wireless networks.The development of orthogonal frequency division multiplexing access (OFDMA) and multiple-input multiple-output (MIMO) communications have provided a high-throughput air interface for delivering the multimedia contents in MBSs. To further improve the spectral efficiency for MIMO communications, the technique of precoding can be applied to tailor the signals to the current downlink channel quality. However, due to the broadcasting nature of MBSs, link adaptation and precoder selection for individual user is infeasible. A fixed precoding scheme where the transmitter simply uses identical precoding matrices is commonly adopted for MBS transmissions in existing systems. In this paper, we propose an effective adaptive precoder selection scheme with low complexity based on precoder training and user feedback. Simulation results show that the proposed scheme effectively improves the performance of received SINR measured at the mobile stations (MSs).

A MIMO-OFDM PHY Integrated (MOPI) scheme is proposed to provide confidentiality against eavesdroppers in wireless networks. The proposed MOPI scheme prevents any eavesdropper from learning the channel state information (CSI) of the wiretap channel and decoding the information being exchanged. This is achieved by the use of channel sounding combined with a novel physical-layer network coding (PNC) scheme such that the eavesdropper, due to lack of CSI, will suffer from very poor decoding performance. The security of the proposed MOPI scheme is verified by computer simulation. The simulation results show that confidentiality is guaranteed as long as the eavesdropper's channel realization is independent of the legal receiver's, which is usually the case in a typical wireless network.

Applications of location estimation have drawn lots of interests in recent years. Many schemes have been developed to estimate the locations of the concerned users. Conventionally, the location of each user is estimated independently by its own observations from the local environment. In this paper, we propose a cooperative location estimation scheme. From the encounter history of a specific user meeting other users and the location estimation results of other users, the user is able to further improve the accuracy of its location estimation. Simulation results show that the cooperative algorithm provides a significant gain over the non-cooperative scheme and the location estimation accuracy increases with the number of users involved in cooperation.

In this study, the authors propose the optimal power allocation scheme that minimises the symbol error probability (SER) of vertical Bell Laboratories layered space-time (VBLAST) systems using M-ary modulations. The essence of the power allocation is to intentionally cause different received power from each layer at the receiver. By judiciously allocating the transmitting power to the layers, the performance of the successive interference cancelation at the receiver can be significantly improved. The exact SER of the VBLAST systems with non-uniform power allocation is analysed for the Rayleigh fading case. The SER is minimised to determine the optimal power allocation pattern for the VBLAST systems with M-ary modulations. Simulations show that our SER analysis is accurate and the proposed power allocation scheme significantly improves the performance of the VBLAST systems in fast fading environments by 3.5–4 dB. The work is applied to the power control of VBLAST systems in slow fading environments. Significant SNR gains of 8.5–10 dB are observed in the numerical experiments. It is also observed that the proposed optimal power allocation scheme can effectively reduce the SER variation among the layers.

Conventional cooperative diversity techniques consider a three-node setup, which involves a pair of source–destination nodes and a signal relay node. It is noted that the existing cooperation schemes are performed in a session-based manner in which the role of each node being a source or relay remains unchanged during each session. The radio resource allocation and the associated performance analysis are not jointly performed. As a result, resource utilisation is less efficient. In this paper, an energy-efficient quality-of-service (QoS)-aware cooperative transmission strategy based on joint resource allocation is proposed. Two source nodes with distinct destinations and QoS requirements are simultaneously considered in resource allocation to optimise the energy efficiency. The QoS outage probability is derived analytically and the attainable energy efficiency is investigated for the proposed scheme. Numerical results show that significant performance gain can be achieved for both node pairs with the proposed cooperation scheme.

IEEE 802.15.4 standard is designed to achieve low-power transmissions in low-rate and short-distance wireless personal area networks (WPANs). For the sake of reducing the control overheads, the modified CSMA/CA protocol used by 802.15.4 does not have the hidden device protection mechanism, such as RTS/CTS mechanism. Previous studies indicate that the probability of any two devices in a infrastructure network unheard of each other is around 41%. Therefore, the hidden device problem (HDP) results in inefficient data transmission and serious power consumption issues in WPAN. In this paper, we propose a cross-layer detection and allocation (CL-DNA) scheme to solve the HDP in IEEE 802.15.4 without the cost of extra control overhead in data transmissions. The proposed scheme detects hidden device relationships based on the overlapped signals and then allocates the hidden devices into distinct sub-periods for transmissions. Simulation results show that the proposed scheme significantly improves the goodput, and with reduction in the MAC delay and the power consumption.

To conduct collaborative beamforming in wireless ad hoc or sensor networks, several protocols must be executed, including the localization protocol, time synchronization protocol, and data dissemination protocol. In practice, however, these protocols are often limited by their complexities for achieving the ideal perfect performance. Therefore, protocol defects such as location errors, time synchronization errors, and message losses often appear in collaborative beamforming with distributed operations. In this paper, we introduce an analytical framework to analyze the impact of protocol defects on the performance of collaborative beamforming. We show numerical results of the proposed model, and explain how the proposed model can be used to mitigate the impact of protocol defects for collaborative beamforming in wireless networks.

Transmitting real-time multimedia data has been a big challenge for wireless communications. The QoS experienced by the multimedia traffic is subject to the time-variant characteristics of the wireless channels. In this paper, a cross-layer algorithm is proposed to combat the wireless channel variation by adjusting the multimedia codec settings according to the MAC frame error rate in real-time. The proposed algorithm is computational efficient and the numerical experiments show that the cross-layer algorithm indeed achieves better performance even for the wireless channels in severe conditions.

In this paper, an accurate performance analysis is proposed for type-II hybrid ARQ scheme. As opposed to the existing type-II hybrid ARQ analysis work in the literature, the analysis proposed in this paper takes the dependency of the successive decoding attempts into account. The proposed analysis is applicable for type-II hybrid ARQ schemes with known weight spectrum of the error-correcting codes used. The channel models considered include AWGN and Rayleigh fading. Numerical experiments show that the proposed analysis is accurate in capturing the performance of type-II hybrid ARQ systems at mid-to-high SNR region.

As the multimedia applications become more popular, there is an increasing demand for wireless communication technology that supports high transmission rate. Vertical bell laboratories layered space-time (V-BLAST) is one of the most popular multiple-input multiple-output (MIMO) architectures that achieves very high spectral efficiency and thus high transmission rate. In this work, we propose the use of power diversity scheme to minimize the bit error rate (BER) of V-BLAST systems. The essence of power diversity scheme is to intentionally cause different received power from each layer at the receiver. By judiciously allocating the transmitting power to the layers, the performance of the successive interference cancellation at the receiver can be significantly improved. The exact BER of the V-BLAST systems with non-uniform power allocation is analyzed for the Rayleigh fading case. The BER is minimized to determine the optimal power allocation pattern for the V-BLAST systems. Simulations show that our BER analysis is accurate and the proposed power diversity scheme significant improves the performance of the V-BLAST systems by 3 to 3.6 dB.

Instant messaging (IM) services enable real-time text and multimedia exchange and online presence awareness. Users typically log onto IM services persistently in order to discover available friends and also to be discovered. However, our analysis shows that running a desktop-oriented IM client on a mobile device over a cellular or a wireless LAN network incurs massive power consumption. Such power consumption penalty can render persistent-IM infeasible for battery-powered mobile devices. The reason for the power penalty lies in the fact that IM must communicate with the network frequently to exchange presence information with remote entities. In this paper, we propose several low power consumption solutions for IM on mobile devices. By reducing the network accesses and keeping mobile devices in the sleep mode as much as possible, these solutions achieve significant power saving. We implement the proposed solutions using a Jabber-based architecture. We also present power measurement results under this implementation. The results agree with our analysis very well.

A new union bound on the bit error probability of bit-interleaved space–time (BI-ST) coded systems is derived. Unlike existing performance analysis tools for BI-ST systems, the new bound provides a general framework for analysing the performance of BI-ST systems employing finite interleaver sizes. The derivation is based on the uniform interleaving assumption of the coded sequence prior to transmission over multiple antennas. The new bound is a function of the distance spectrum of the code, the signal constellation used and the space–time (ST) mapping scheme. The bound is derived for a general BI-ST coded system and applied to two specific examples, namely, the BI space–time coded modulation and the BI space–time block codes. Results show that the analysis provides a close approximation to the BI-ST performance for a wide range of signal-to-noise ratios. The analysis can also accurately characterise the performance differences between different interleaver sizes, which is a breakthrough in the analysis of BI-ST coded systems.

In this paper a union bound on the bit error probability of bit-interleaved space-time (BI-ST) coded systems is derived. The derivation is based on the uniform interleaving assumption of the coded sequence prior to transmission over the multiple antennas. The performance of a BI-ST coded system is a function of how the bit errors are distributed over the signals in the codeword. In this paper, we derive this distribution as well as the corresponding pairwise error probability. The bound is a function of the distance spectrum of the code, the signal constellation used and the space-time (ST) encoding scheme. The bound is derived for a general BI-ST coded system and applied to two specific examples; namely, the BI space-time coded modulation (BI-STCM) and the BI space-time block codes (BI-STBC). Results show that the analysis provides a close approximation to the performance for a wide range of signal-to-noise ratios (SNR).

In this paper a union bound on the bit error probability of bit-interleaved coded modulation (BICM) is derived. In the derivation we assume that the bit errors in a codeword are uniformly distributed over the transmitted symbols. We derive the bound for BICM systems over AWGN, Rician and Nakagami fading channels. The proposed bound is general to any signal constellation and coding scheme with a known distance spectrum