Combining semi-grant-free (SGF) transmission with non-orthogonal multiple access transmission (NOMA) allows grant-free (GF) UEs to access the network through resource blocks that are solely allocated to grant-based (GB) UEs. A channel gain constraint for GF UEs is introduced to reduce the interference impact to GB UE, which causes an access fairness problems for GF UEs. Moreover, the power collision (PC) interference significantly degrades the interference cancellation performance. To address these issues, this paper proposes a layer SGF-NOMA random access (RA) procedure and a joint power back-off (PB) scheme. In the proposed RA procedure, GF UEs can freely share the GB UE’s resource blocks without channel gain constraints. To suppress the PC interference, the proposed PB scheme optimizes the power distribution in the NOMA group according to the variable interference experienced by the NOMA UEs. To maintain the signal-to-interference balance, more power is transferred to the UEs that suffer more interference. The closed-form expressions of the outage probability, successful access probability and sum data rate are derived via order statistic theory. Both the analytical and simulation results demonstrate that the layer SGF-NOMA procedure and joint PB scheme achieves significant performance gains over traditional schemes.

Carrier-sense multiple access with collision avoidance (CSMA/CA) is one of the fundamental medium access control (MAC) protocols for ad hoc networks. As a network’s size increases, its throughput degrades substantially because of packet collisions. To reduce the collision probability, combining non-orthogonal multiple access (NOMA) with CSMA/CA is a promising solution. However, existing NOMA-CSMA/CA protocols adopt distributed power selection and channel inversion power control, resulting in a high power collision probability and limiting the number of power levels. To address these issues, we propose a power back-off NOMA-based CSMA/CA (PBN-CSMA/CA) protocol for ad hoc networks. The proposed protocol achieves centralized power allocation, avoiding power collisions by employing the Zadoff-Chu (ZC) sequence and the power level allocation (PLA) frame. Additionally, power back-off (PB) control is used to set the transmission power, which expands the number of power levels and gives full play to the performance advantages of NOMA. To analyze the performance comprehensively, the closed-form expressions of the average outage probability, normalized saturation throughput, average packet delay and transmission energy consumption are theoretically analyzed. Both the analytical and simulation results demonstrate that the PBN-CSMA/CA protocol outperforms the existing NOMA-CSMA/CA and traditional CSMA/CA protocols, with significant throughput gains and delay reductions.

Carrier-sense multiple access with collision avoidance (CSMA/CA) is one of the fundamental medium access control (MAC) protocols for ad hoc networks. As a network increases in size, its throughput degrades substantially due to packet collision. To reduce the collision probability, a nonorthogonal multiple-access (NOMA)-based CSMA/CA (NCSMA) protocol is proposed. The proposed NCSMA protocol employs Zadoff-Chu (ZC) sequences and a NOMA power coefficient allocation (N-PCA) frame to select the NOMA node and schedule the power level, preventing packet collisions caused by random selection. Moreover, the normalized saturation throughput and the average packet delay of the proposed approach are theoretically analyzed, and closed-form expressions are derived. Simulation results show that the proposed protocol improves the normalized saturation throughput by 66.7% and reduces the average packet delay by 35.97% compared to those of the current best CSMA/CA protocol.

In the realm of flying ad-hoc network(FANETs), unmanned aerial vehicles (UAVs) frequently encounter challenges related to adaptability in complex jamming environments. To address this issue, our research introduces an innovative frequency hopping(FH) strategy that combines federated learning(FL) with double deep Q-Networks (DDQN). The UAVs adaptively select frequency hopping patterns by a locally tuned DDQN model, which they then share with a multi-access edge computing (MEC) server to facilitate global aggregation optimization. The study also introduces an difficulty-adaptive training mechanism to optimize the allocation of computational resources. Experimental validations of our method confirm its efficacy in significantly improving both the adaptability and overall performance of FANETs in challenging jamming conditions, demonstrating robust convergence and high accuracy.

Nonorthogonal multiple access (NOMA) is classified into grant-based (GB) random access (RA) and grant-free (GF) RA in 5G systems. GF NOMA RA allows user equipments (UE) to directly transmit data packet over uplink resources without grant information so that the signaling overhead is substantially reduced. This approach is suitable for small-size data packet IoT services. However, power collision interference resulting from uncoordinated resource selection leads to serious transmission failure in massive MTC scenarios. As a result, the number of transmissions and access delay are sharply increased. In this article, we make the best of the advantages of both GB RA and GF RA and propose a hybrid grant (HG) NOMA RA scheme to address the signaling overhead and power collision issues. The objective of the proposed scheme is to achieve an acceptable tradeoff among signaling overhead, access failure probability, and access delay. The UE selects the access resource without uplink grant, and the BS assists to avoid inter-NOMA power collision by limited interference resolution (IR) signaling. To comprehensively analyze the performance, the closed-form expression of outage probability is derived by adopting the order statistic theory and the sum of independent exponential distributions, and the maximum number of transmissions and access delay are theoretical analyzed. A Monte Carlo simulation framework is built to verify the theoretical analysis. Finally, the analytical and simulation results show that HG NOMA RA outperforms GB NOMA RA and GF NOMA RA in massive access scenarios.

This paper mainly analyzes the change of InSAR phase with deformation and displacement by using multifunctional microwave indoor measurement. The experimental target adopts the high-voltage line tower component with strong scattering - metal tripod, which causes “deformation” by padding the bottom of the tripod by 5mm. According to the experimental principle of equal height interference fringes of electromagnetic waves, the measured data before and after deformation of the metal tripod are processed to obtain the phase data at different incident angles, The consistency between the InSAR phase change after phase unwrapping and the actual vertical deformation of the tripod is verified, which provides a basis for the accurate evaluation of InSAR crustal deformation monitoring, and has a good reference for the influence of different working parameters, especially the incident angle on InSAR results.

Hypertension is one of the most important contributors to heart disease and stroke. Multimodality medical image fusion plays an important role in the precise diagnosis, treatment planning and follow-up studies of various diseases. In this paper, we propose an image fusion framework in patients with hypertension, which is based on Frei-Chen operators in generalized reisz-wavelet transform (GRWT) domain. The proposed method is tested on two cases of MRI/CT and MRI/SPECT images. The input medical images are first transformed by GRWT into basic and detail components. Further, they are fused respectively by Frei-Chen operators which extracts ripples, edges, lines and points well. Finally, the fused image is constructed by the inverse GRWT and evaluated by indicators such as average gradient and spatial frequency etc. The visual and quantitative evaluation of the results demonstrated the superior performance of the proposed image fusion method which assists doctors for precise and sufficient diagnosis.

In this paper, we consider a cluster-to-cluster (C2C) multicast scenario where multiple transmitters in a sending cluster cooperatively transmit a common known data packet to multiple receivers of the receiving cluster. The maximization of transmission rate is firstly formulated as a max-min fairness problem given the set of receivers, and an iterative transmit beamforming optimization algorithm is proposed to obtain the optimal transmit beamforming vector. Furthermore, in order to maximize the C2C system throughput, a joint optimization algorithm of transmit beamforming and receiver selection is proposed to search the optimal set of receivers based on the above transmit beamforming algorithm. The simulation results prove that the proposed algorithm has achieved a higher throughput than the conventional schemes in a lower complexity.

For sparse code multiple access advanced (SCMAA), the quality of initial information on each resource node and the convergence reliability of the detected user in each decision process were unsatisfactory at the message passing algorithm (MPA) receiver. Driven by these problems, this paper proposes a nonuniform code multiple access (NCMA) scheme. In the codebook design of NCMA, different transmitted layers are generated from different complex multidimension constellations, respectively, and a novel basic complex multidimension constellation design is proposed to increase the minimum intrapartition distance. Then a novel criterion of permutation set is proposed to maximize the sum of distances between interfering dimensions of transmitted codewords multiplexed on any resource node, where the number of nonzero elements of transmitted codewords is more than 1. On the other side, an advanced MPA receiver is proposed to improve the reliability of detection on each transmitted layer of NCMA. Simulation results show that the block error rate performance of NCMA outperforms SCMAA and sparse code multiple access (SCMA) under the same spectral efficiency.

This paper investigates a power allocation problem for maximizing energy efficiency (EE) in downlink Coordinated Multi-Point (CoMP) systems with non- orthogonal multiple access (NOMA). First, users' achievable data rate and network throughput are analysed under three transmission schemes: 1) all users' signals are jointly transmitted by coordinated base stations (BSs); 2) only cell-edge users' signals are jointly transmitted by coordinated BSs; 3) each user's signals are transmitted by only one BS. Next, we formulate EE maximization problems for the three schemes under the constraints of minimum users' data rate and maximum BS transmit power. The considered problem is non-convex and hard to tackle. To address it, an iterative sub-optimal algorithm is proposed by adopting fractional programming and difference of convex programming. Numerical results show that the near optimality performance of EE can be achieved by using the proposed algorithm with advantages of fast convergence and low complexity. Three transmission schemes of NOMA have superior EE performance compared with conventional orthogonal multiple access scheme in the same CoMP networks.

In this paper, we propose a dynamic resource allocation with quality-of-service (Qos) guarantee for clustered machine-to-machine (M2M) communications, which provides higher throughput as well as higher resource efficiency and lower access delay in a co-existing environment of both delay-sensitive and delay-tolerant services. We develop the dynamic resource allocation into four cases. In each case, the total throughput is improved under the condition of satisfying the access delay constrain for each cluster by two folds. First, a reasonable resource tradeoff between physical random access channel (PRACH) and physical uplink shared channel (PUSCH) is achieved. Second, the PRACH resource are separated for each cluster, and the access class barring (ACB) schemes separately control the number of devices belonging to different clusters. The case whose the total throughput is maximum is selected from the four cases as the optimal resource allocation scheme. Simulation results demonstrate our scheme can significantly improve the total throughput as well as the resource efficiency and reduce the access delay for each cluster.

Spatially coupling data transmission (SCDT) is a multiple access technique. Since both SCDT and low density parity-check (LDPC) codes can be represented by a factor graph, a joint sparse graph (JSG) including the single graphs of SCDT and LDPC codes is constructed. Based on the JSG, the joint demodulation and decoding (JDD) by applying belief propagation (BP) algorithm in the parallel schedule is performed, but its convergence rate is slow. In order to accelerate convergence rate, a new serial schedule is proposed. The extrinsic information transfer (EXIT) charts of iterative JDD are investigated for the two schedules and employed to evaluate their converge behaviour. EXIT analysis and simulation results demonstrate that about half iteration number can be saved at the cost of marginal system performance loss. Furthermore, compared with separate demodulation and decoding, turbo-structured JDD and the uncoupling structured JDD, the JDD based on JSG for SCDT by utilizing serial schedule achieves the best performance.

Motivated by improving the number of successful access for machine-to-machine (M2M) communications, and realizing resource allocation for any number of active M2M UEs with less computation, a computationally efficient adaptive resource allocation scheme is given in this paper. eNB first learns the resource allocation for few active M2M UEs, which is adaptively changed with the number of uplink resource blocks. Then the resource allocation for other M2M UEs is derived from those active M2M UEs. In addition, the access barring scheme is incorporated to improve the number of successful access. Experimental simulations demonstrate our scheme can significantly improve the number of successful access and reduce resource allocation computation.

This paper proposes an improved random access (RA) procedure for machine to machine (M2M) communications. The proposed RA procedure makes evolved nodeB (eNB) detect if a preamble is selected by multiple user equipments (UEs) in the first step. To avoid false detection, an extended guard band is provided in PRACH. Based on the improved RA procedure, theoretical analysis on the probability of preamble collision and the number of successful access are addressed. In the simulation, the simulation of the probability of false detection with different number of bits of UE ID, the number of successful access and the impact of preamble collision are presented. Simulation results show that the new RA procedure outperforms traditional RA procedure on both probability of preamble collision and the number of successful access.

With the widespread application of wireless networks and the requirements of different user equipments (UEs), energy has become a scarcer resource as well as spectrum. In this paper, considering the actual scenarios of imperfect channel state information (CSI), we study a resource allocation scheme in the downlink orthogonal frequency division multiple access (OFDMA) systems. To balance between energy efficiency (EE) and proportional fairness (PF), the problem is formulated as maximizing average achievable EE with the constraints of PF of users and QoS assurance. To solve the optimal problem, we divide it into two layers. The sub-problem P1 of inner layer is solved to maximize PF, with the parameter of total transmit power which is updated by the sub-problem P2 of outer layer. In outer layer, with the allocation scheme from P1, a gradient-based adaptation resource allocation algorithm is proposed to achieve the maximum EE with total transmit power updated in every gradient iteration. Moreover, the impacts of the imperfect CSI on EE and PF are analysed. Simulation results are presented to show the superior performance of the proposed algorithms and verify the analytical findings.

On dispersing different base matrices combined with masking, different kinds of quasi-cyclic low-density parity check (QC-LDPC) codes are constructed, which may achieve good error performances. Two new algebraic constructions of regular QC-LDPC codes are presented in this paper. The two constructions are based on two base matrices by dispersing and masking. The two base matrices are based on the generators of the cyclic group of a prime field. Results show that the two classes of codes presented in this paper perform well with iterative decoding over AWGN channel and have advantages over MacKay codes in some aspects of code performances. We find that one of the constructed codes converges very fast with iterative decoding, which is a critical property in ultra-high throughput communication systems.

Chronic diseases are gradually becoming the principal factors of harm to people's health. Fortunately, the development of e-health provides a novel thought for chronic disease prevention and treatment. This paper focuses on the research of cardiovascular disease (CVDs) prevention and early warning techniques using e-health and data mining. In this paper, we will use weighted associative classification algorithm to model the data in healthcare database to determine the level of cardiovascular risk. Besides, on the basis of data mining and knowledge discovery, intelligent warning mechanisms are proposed to provide different services to patients with different levels of risk. The experimental results show that the used classification algorithm is a more effective mining algorithm in the field of healthcare with higher accuracy and better comprehension. Our study is of definite significance to help control risk level of CVDs patients.

This paper presents a healthcare monitoring architecture coupled with a wireless sensor network and wearable sensor systems which monitor chronic patients in nursing house or the elderly in their home. With this architecture, we investigate how sensor nodes are deployed in the three-dimension (3D) monitoring region to achieve uniform distribution, which directly determines the Quality of Service (QoS). Based on the existing two-dimension (2D) coverage-enhancing algorithms for wireless sensor networks, a 3D sensing model and a coverage optimization algorithm are proposed in this paper. Firstly, an intelligent optimization algorithm is utilized to adjust the position of sensor nodes. Then, we pick out the redundant nodes with the set coverage algorithm, and move them into the uncovered area to increase the coverage ratio. The simulation results show that the coverage ratio increased by the coverage optimization algorithm compared with the other coverage algorithms.

Energy is one of the crucial factors in wireless sensor network. In this paper, we consider energy fairness problem in heterogeneous wireless sensor network. Firstly, we propose a nodes' deployment model in which we deploy heterogeneous sensor nodes judiciously to conserve energy. This prevents the problem of occurrence of 'energy holes' and ensures prolonged network lifetime. Then, we use Game Theory to model the packet transmission among sensor nodes, and get the Nash equilibrium by properly designing the measurement function. Finally, the simulation results fully prove the effectiveness of the proposed scheme in this paper, which not only make the energy consumption of the network balanced but the network lifetime also improved.

Distributed multiple-input multiple-output (DMIMO) system is a combination of distributed antenna systems (DAS) and co-located antenna systems (CAS). Power allocation between different antennas is a very important aspect in both DAS and CAS. In this paper, we investigate the downlink power allocation scheme in D-MIMO systems based on minimum symbol error rate (SER) criteria. We propose a power allocation scheme which can effectively approximate the optimal allocation scheme. In the proposed scheme, both Large-scale fading and transceiver antenna correlation are taken into consideration. Moreover, mobile terminal (MT) only needs to feedback largescale fading information and the rank of transmit antenna correlation matrix periodically, which significantly reduces the feedback overhead. Simulation results verify the capacity improvement based on the proposed power allocation scheme.

In many practical systems, perfect channel state information (CSI) is difficult to obtain at the base station (BS), we usually use limited feedback CSI to reduce the symbol error rate (SER). To analyze the SER performance of different transmit distributed antenna (DA) subset in limited feedback distributed antenna systems (DAS), the closed-form SER expressions for both binary phase shift keying (BPSK) and M-phase shift keying (MPSK) are derived in this paper. From these expressions, we find there exists an appropriate transmit DA subset which can obtain the best SER performance. Then, an adaptive transmit DA selection scheme with the minimum SER is proposed. Simulation results show that the proposed scheme can achieve SER performance gain than blanket transmission scheme and selection diversity scheme.

BACKGROUND: Traditional Chinese Medicine (TCM) is characterized by the wide use of herbal formulae, which are capable of systematically treating diseases determined by interactions among various herbs. However, the combination rule of TCM herbal formulae remains a mystery due to the lack of appropriate methods. METHODS: From a network perspective, we established a method called Distance-based Mutual Information Model (DMIM) to identify useful relationships among herbs in numerous herbal formulae. DMIM combines mutual information entropy and "between-herb-distance" to score herb interactions and construct herb network. To evaluate the efficacy of the DMIM-extracted herb network, we conducted in vitro assays to measure the activities of strongly connected herbs and herb pairs. Moreover, using the networked Liu-wei-di-huang (LWDH) formula as an example, we proposed a novel concept of "co-module" across herb-biomolecule-disease multilayer networks to explore the potential combination mechanism of herbal formulae. RESULTS: DMIM, when used for retrieving herb pairs, achieves a good balance among the herb's frequency, independence, and distance in herbal formulae. A herb network constructed by DMIM from 3865 Collaterals-related herbal formulae can not only nicely recover traditionally-defined herb pairs and formulae, but also generate novel anti-angiogenic herb ingredients (e.g. Vitexicarpin with IC50=3.2 μM, and Timosaponin A-III with IC50=3.4 μM) as well as herb pairs with synergistic or antagonistic effects. Based on gene and phenotype information associated with both LWDH herbs and LWDH-treated diseases, we found that LWDH-treated diseases show high phenotype similarity and identified certain "co-modules" enriched in cancer pathways and neuro-endocrine-immune pathways, which may be responsible for the action of treating different diseases by the same LWDH formula. CONCLUSIONS: DMIM is a powerful method to identify the combination rule of herbal formulae and lead to new discoveries. We also provide the first evidence that the co-module across multilayer networks may underlie the combination mechanism of herbal formulae and demonstrate the potential of network biology approaches in the studies of TCM.

In this paper, the pilot design aiming at mitigating the inter-cell interference in MIMO OFDM systems is addressed. We first compute the mean square error of the frequency domain LS joint channel estimation with the consideration of interfering cell. We then overview the optimal pilot sequences within a cell, which can cancel the intra-cell multiple access interference. Based on the mean square error and variation coefficient, we propose two conditions for the pilot design to mitigate the intercell interference. It is shown that if an ideal channel between interferer and receiver is assumed, we can obtain the pilots resulting in a smaller value of mean square error based on the variation coefficient of zero, which make the power of inter-cell interference distribute at all paths of the channel more uniformly and less, therefore, the performance on system level would be improved. A further discussion about proposed guidelines in practical system is made, and numerical calculations as well as simulation results are presented to verify the theoretical analysis.