Joint alignment and steering to manage interference

In wireless communication networks,mobile users in overlapping areas may experience severe interference,therefore,designing effective Interference Management(IM)methods is crucial to improving network performance.However,when managing multiple disturbances from the same source,it may not be feasible to use existing IM methods such as Interference Alignment(IA)and Interference Steering(IS)exclusively.It is because with IA,the aligned interference becomes indistinguishable at its desired Receiver(Rx)under the cost constraint of Degrees-of-Freedom(DoF),while with IS,more transmit power will be consumed in the direct and repeated application of IS to each interference.To remedy these deficiencies,Interference Alignment Steering(IAS)is proposed by incorporating IA and IS and exploiting their advantages in IM.With IAS,the interfering Transmitter(Tx)first aligns one interference incurred by the transmission of one data stream to a one-dimensional subspace orthogonal to the desired transmission at the interfered Rx,and then the remaining interferences are treated as a whole and steered to the same subspace as the aligned interference.Moreover,two improved versions of IAS,i.e.,IAS with Full Adjustment at the Interfering Tx(IAS-FAIT)and Interference Steering and Alignment(ISA),are presented.The former considers the influence of IA on the interfering user-pair's performance.The orthogonality between the desired signals at the interfered Rx can be maintained by adjusting the spatial characteristics of all interferences and the aligned interference components,thus ensuring the Spectral Efficiency(SE)of the interfering communication pairs.Under ISA,the power cost for IS at the interfered Tx is minimized,hence improving SE performance of the interfered communication-pairs.Since the proposed methods are realized at the interfering and interfered Txs cooperatively,the expenses of IM are shared by both communication-pairs.Our in-depth simulation results show that joint use of IA and IS can effectively manage multiple disturbances from the same source and improve the system's SE.

SCIM: Incorporating secure communication and interference management in one operation

Due to the broadcast nature of wireless communications,users’data transmitted wirelessly is susceptible to security/privacy threats.Meanwhile,as a result of the limitation of spectrum resources,massive wireless connections will incur serious interference,which may damage the efficiency of data transmission.Therefore,improving both efficiency and secrecy of data transmission is of research significance.In this paper,we propose a wireless transmission scheme by taking both Secure Communication(SC)and Interference Management(IM)into account,namely SCIM.With this scheme,an SCIM signal is generated by the legitimate transmitter(Tx)and sent along with the desired signal,so that the SCIM signal can interact with and suppress the environmental interference at the legitimate receiver(Rx).Meanwhile,the SCIM signal may interfere with the eavesdropper in the coverage of legitimate transmission so as to deteriorate the eavesdropping performance.Therefore,the secrecy of desired transmission is improved.In this way,both the transmission efficiency and privacy are enhanced.Then,by taking various transmission preferences into account,we develop different implementations of SCIM,including Interference Suppression First SCIM(ISF-SCIM),Data Transmission First SCIM(DTF-SCIM),Anti-Eavesdropping First SCIM(AEF-SCIM),and Secrecy Rate Maximization SCIM(SRM-SCIM).Our in-depth simulation results have shown the proposed methods to effectively improve the efficiency and secrecy of the legitimate transmission.

Ultra Dense Satellite-Enabled 6G Networks:Resource Optimization and Interference Management

With the evolution of the sixth generation(6G)mobile communication technology,ample attention has gone to the integrated terrestrial-satellite networks.This paper notes that four typical application scenarios of integrated terrestrial-satellite networks are integrated into ultra dense satellite-enabled 6G networks architecture.Then the subchannel and power allocation schemes for the downlink of the ultra dense satellite-enabled 6G heterogeneous networks are introduced.Satellite mobile edge computing(SMEC)with edge caching in three-layer heterogeneous networks serves to reduce the link traffic of networks.Furthermore,a scheme for interference management is presented,involving quality-of-service(QoS)and co-tier/cross-tier interference constraints.The simulation results show that the proposed schemes can significantly increase the total capacity of ultra dense satellite-enabled 6G heterogeneous networks.

On Normalized Least Mean Square Based Interference Cancellation Algorithm for Integrated Sensing and Communication Systems

Integrated sensing and communication(ISAC)technology is a promising candidate for next-generation communication systems.However,severe co-site interference in existing ISAC systems limits the communication and sensing performance,posing significant challenges for ISAC interference management.In this work,we propose a novel interference management scheme based on the normalized least mean square(NLMS)algorithm,which mitigates the impact of co-site interference by reconstructing the interference from the local transmitter and canceling it from the received signal.Simulation results demonstrate that,compared to typical adaptive interference management schemes based on recursive least square(RLS)and stochastic gradient descent(SGD)algorithms,the proposed NLMS algorithm effectively cancels co-site interference and achieves a good balance between computational complexity and convergence performance.

Mitigation of inter-cell interference in visible light communication

This paper proposes the orthogonal and nonorthogonal schemes in the interference environments for visible light communication（ VLC） systems. The proposed schemes pay attention to the case when different bit streams from multiple cells are simultaneously transmitted, which consequently causes inter-cell interference（ ICI） and greatly deteriorates the bit error rate（ BER） and channel capacity performance of the system. The performance of the newdeveloped multi-cell system in indoor VLC systems is evaluated. The bipolar phase shift keying（ BPSK） modulation scheme with orthogonal pulses（ OPs） for multiple cells environments is employed to mitigate the ICI problem and improve the BER and channel capacity performances. Since the use of different OPs in each cell requires more number of OPs, which requires high bandwidth, OPs are reused at certain distances. Three different schemes, which are OPs,orthogonal and non-orthogonal pulses（ NOP） reuse, are compared. This paper investigates the impact of using these schemes and compared their performances in the ICI environments. The BER and channel capacity using the proposed schemes are comprehensively examined. Simulation and theoretical results showthat the OPs schemes are more effective in the interference areas of the room and significantly outperform NOP.

Mechanically strong and folding-endurance Ti_(3)C_(2)T_(x) MXene/PBO nanofiber films for efficient electromagnetic interference shielding and thermal management

Electromagnetic interference(EMI)shielding materials with excellent flexibility and mechanical properties and outstanding thermal conductivity have become a hot topic of research in functional composites.In this study,the“sol-gel-film conversion technique”is used to assemble polyetherimidefunctionalized Ti_(3)C_(2)T_(x) nanosheets(f-Ti_(3)C_(2)T_(x))with poly(p-phenylene-2,6-benzobisoxazole)(PBO)nanofibers(PNFs),followed by dialysis and vacuum drying to prepare f-Ti_(3)C_(2)T_(x)/PNF films with lamellar structures.When the loading of f-Ti_(3)C_(2)T_(x) is 70 wt%,the f-Ti_(3)C_(2)T_(x)/PNF film presents optimal comprehensive properties,with an EMI shielding effectiveness(SE)of 35 dB and a specific SE/thickness((SSE,SE/density)/t)of 8211 dB cm^(2)/g,a tensile strength of 125.1 MPa,an in-plane thermal conductivity coefficient(λ)of 5.82 W/(m K),and electrical conductivity of 1943 S/m.After repeated folding for 10,000 cycles,the EMI SE and the tensile strength of f-Ti_(3)C_(2)T_(x)/PNFs films still remain 33.4 dB and 116.1 MPa,respectively.Additionally,the f-Ti_(3)C_(2)T_(x)/PNF film also shows excellent thermal stability,flame retardancy,and structural stability.This would provide a novel method for the design and fabrication of multifunctional composite films and considerably expand the applications of MXene-and PNF-based composites in the fields of EMI shielding and thermal management.

Clustering-based interference management in densely deployed femtocell networks

Deploying femtoceUs underlaying macrocells is a promising way to improve the capacity and enhance the coverage of a cellular system. However, densely deployed femtocells in urban area also give rise to intra-tier interference and cross-tier issue that should be addressed properly in order to acquire the expected performance gain. In this paper, we propose an interference management scheme based on joint clustering and resource allocation for two-tier Orthogonal Frequency Division Multiplexing （OFDM）-based femtoeeU networks. We formulate an optimization task with the objective of maximizing the sum throughput of the femtocell users （FUs） under the consideration of intra-tier interference mitigation, while controlling the interference to the maeroeell user （MU） under its bearable threshold. The formulation problem is addressed by a two-stage procedure： femtoeells clustering and resource allocation. First, disjoint femtocell clusters with dynamic sizes and numbers are generated to minimize intra-tier interference. Then each cluster is taken as a resource allocation unit to share all subehannels, followed by a fast algorithm to distribute power among these subchannels. Simulation results show that our proposed schemes can improve the throughput of the FUs with acceptable complexity.

Interference management via access control and mobility prediction in two-tier heterogeneous networks

Abstract： Two-tier heterogeneous networks （HetNets）, where the current cellular networks, i.e., macrocells, are overlapped with a large number of randomly distributed femtocells, can potentially bring significant benefits to spectral utilization and system capacity. The interference management and access control for open and closed femtocells in two-tier HetNets were focused. The contributions consist of two parts. Firstly, in order to reduce the uplink interference caused by MUEs （macrocell user equipments） at closed femtocells, an incentive mechanism to implement interference mitigation was proposed. It encourages femtoeells that work with closed-subscriber-group （CSG） to allow the interfering MUEs access in but only via uplink, which can reduce the interference significantly and also benefit the marco-tier. The interference issue was then studied in open-subscriber-group （OSG） femtocells from the perspective of handover and mobility prediction. Inbound handover provides an alternative solution for open femtocells when interference turns up, while this accompanies with PCI （physical cell identity） confusion during inbound handover. To reduce the PCI confusion, a dynamic PCI allocation scheme was proposed, by which the high handin femtocells have the dedicated PCI while the others share the reuse PCIs. A Markov chain based mobility prediction algorithm was designed to decide whether the femtoeell status is with high handover requests. Numerical analysis reveals that the UL interference is managed well for the CSG femtocell and the PCI confusion issue is mitigated greatly in OSG femtocell compared to the conventional approaches.

Sponge:An Oversubscription Strategy Supporting Performance Interference Management in Cloud

Resource oversubscription optimizes the utilization of the computing resources. Many well-known virtual machine monitors(VMMs)such as Xen and KVM,adopt this approach to help maximize the yield of the cloud datacenters That is,with proper resource oversubscription strategies,more virtual machines(VMs) can be supported by limited resources. However performance interference among VMs hosting in the same physical machines(PMs) exists in cloud environment,and probably aggravated by resource oversubscription strategies,which aims to put more VMs into the same PM. In this paper,we present a resource oversubscription strategy called Sponge targeting cloud platforms Sponge mitigates the issue of performance interference among the oversubscribed co-hosting VMs. Sponge also provides a VM association strategy for each PM to handle with its besteffort. We performed our evaluation on a virtua datacenter simulated by Xen. Our evaluation results show that Sponge improves the resources utilization and manages to make each VM mee its performance requirement even hosting with other VMs in the same PM.

A Novel Radio Resource Management for Interference Mitigation in OFDMA System

In Orthogonal Frequency Division Multiple Access (OFDMA) systems, such as Long Term Evolution (LTE) and so on, the resources used by each user are orthogonal, and the OFDMA systems performances are mainly affected by the inter-cell interference. Therefore, the inter-cell interference mitigation technology becomes a hotspot. The objective of interference mitigation technologies used in OFDMA systems are to increase cell-edge throughput and average cell throughput. In this paper, the Resource Block Planning (BRBP) based scheme is proposed to mitigate the inter-cell interference and improve the cell-edge throughput. Comparison between the simulation results of BRBP and Round Robin (RR) illustrates that the enhanced performance of BRBP.

Network Coding.Based Interference Management Scheme in D2D Communications

In this paper,we propose an interference management scheme for device-to-device(D2D)communications in cellular networks.Considering the underlay D2D communications,the signal quality of cellular users would be affected by D2D users.To solve this problem,we explore the application of network coding and relay-assistance to mitigate interference.In the proposed scheme,helper nodes overhear the signal from cellular users,encode the received packets,and send the encoded packets to the base station.We design the helper node selection scheme and the transmission policy of helper nodes.The performance of the proposed scheme for different positions of the cellular user and D2D users is then evaluated.The results suggest that the cellular transmission scheme should be adjusted dynamically when underlay D2D communications are active.Compared with the existing solutions,the proposed scheme can effectively increase system throughput.

Interference analysis and novel fractional frequency reuse scheme in LTE networks

Inter-cell interference (ICI) mitigation is always a challenge issue in LTE system. In this paper, several common interference parameters are firstly analyzed for both cell edge users and center users, and then a novel fractional frequency reuse (FFR) architecture based on interference avoidance scheme coupled with power control is proposed to solve the problem of interference management in multi-cell LTE environment. The scheme divides the whole sub-carriers into three groups orthogonally. One is allocated to cell edge users, while another two are assigned to cell center users with different transmitter power. Then a parameter named interference avoidance factor (IAF) is defined to avoid ICI and adjust the number of allocated sub-carriers to match the number of users. The parameter also takes weight factor and fairness factor into consideration. The simulation results show the proposed scheme can improve the performance of cell edge users obviously.

An enhanced almost blank sub-frame management for efficient elCIC in non-uniform HetNets

A new enhanced inter-cell interference coordination （elCIC） is adopted for managing almost blank sub-frame （ABS）,which jointly exploits the time, frequency and power dimensions to improve the resource utilization. In particular, a non-uniform two tier heterogeneous network （ HetNet） is considered, where the pico cells are located close to the macro cell and the number of users in each pico cell is different. To alleviate the interference caused by the co-channeldeployment,the macro cells employ low power ABS （LP- ABS）, and the resource blocks （RBs） are divided into twoparts during an ABS. One is exclusively reserved for macro cell users ad the other is reserved for pico cell users. Themacro cells are allowed to use different percentages of RBs and different powers for their own transmission during the LP- ABS. The user association,resource allocation,ABS proportion,the frequency band partition parameter and the transmission power of macro cells are considered, aiming at maximizing the proportional fairness utility of the system. An iterative algorithm is also proposed and simulation results demonstrate that the proposed algorithm can improve both the system throughput and user fairness compared with the existing schemes.

Successive Interference Cancellation and Alignment in K-User MIMO Interference Channels with Partial Unidirectional Strong Interference

Recently cellular networks have been densely and heterogeneously deployed indoors and outdoors to expand the network capacity,and thus the in-building propagation loss and the transmit power diversity of access points will exacerbate link heterogeneity and result in partial unidirectional strong interference.To make full use of the strong interference feature,we propose the successive interference cancellation and alignment(SICA)scheme in the K-user interference channel with partial unidirectional strong interference.SICA is designed to transmit two kinds of data streams simultaneously,the alignment streams and superposition streams.The alignment streams will follow the interference alignment criterion to maintain the optimal degrees of freedom(DoF)performance;the superposition streams are handled via successive interference cancellation at all the strongly interfered receivers to improve the overall achievable rate.The joint transceiver designs for SICA is modeled as a weighted sum rate(WSR)maximization problem,and then can be alternately solved for a local optimum according to the optimality equivalence between WSR and its corresponding weighted mean square error(WMMSE)problem.Simulation results have confirmed the sum rate improvement and DoF optimality of the proposed SICA scheme.

Inter-cell downlink co-channel interference management through cognitive sensing in heterogeneous network for LTE-A

Heterogeneous network for long term evolution advanced（LTE-A） creates severe interference.It is an urgent task to overcome the interference in macro cellular with low-power base stations（BSs）,such as relay,pico,and femto called subnet nodes.In this paper,the cognitive interference model in interference zone（IZ） of the practical heterogeneous scenario is proposed.Based on investigation of interaction between the macro BS and subnet nodes in this model,the strategy framework of the cognitive critical ratio and power reward factor is set up for interference management aiming to get the maximum net saving power.The study of interference management is transformed into a multiple objective non-linear programming（MONLP） of the maximum saving power for the macro BS and subnet nodes.To facilitate the best compromise solution for both,the MONLP is changed into single objective programming and genetic algorithm（GA） is employed to obtain the global optimum solution.In addition,the practical implementation using the proposed algorithm in heterogeneous network for LTE-A is designed.Finally,numerical evaluation is used to test the applicability of the proposed algorithm,and system level simulation results demonstrate the effectiveness of the proposed interference management scheme.

Superhydrophobic MXene‑Based Fabric with Electromagnetic Interference Shielding and Thermal Management Ability for Flexible Sensors

Smart fabrics have made remarkable progress in the field of wearable electronics because of their unique structure,flexibility and breathability,which are highly desirable with integrated multifunctionality.Here,a superhydrophobic smart fabric has been fabricated by decorating conductive MXene on nylon fabric modified by polydopamine(PDA),followed by spraying hydrophobic materials(SiO_(2) and FOTS).The hydrophobic layer not only provides the fabric with superhydrophobicity,but also protects MXene from oxidation.Highly conductive MXene-wrapped fibers endow the fabric with adjustable conductivity and many satisfactory functions.Commendably,the smart fabric possesses sensing performances of ultralow detection limit(0.2%strain),fast response time(60 ms),short recovery time(90 ms),and outstanding sensing stability(5000 cycles).These sensing performances allow the smart fabric to accurately detect body respiratory signals in the running state,exercise state and sleep state,thus keeping track of respiratory health information.Moreover,the smart fabric also exhibits outstanding EMI shielding effectiveness(66.5 dB)in the X-band,satisfactory photothermal performance(68.6℃at 100 mW/cm2),and excellent electrothermal conversion capability(up to 102.3℃at 8 V).Therefore,the smart fabric is extremely promising for applications in EMI shielding,thermal management,and respiratory monitoring,and is an ideal candidate for smart clothing and as a medical diagnostic tool.

Efficient Resource Allocation with Improved Interference Mitigation in FFR-Aided OFDMA Heterogeneous Networks

Fractional frequency reuse(FFR) has recently emerged as an efficient inter-cell interference coordination technique for orthogonal frequency division multiple access(OFDMA) based multi-tier cellular networks due to its low complexity, minimal signaling over-head, and coverage improvement. In this work, an intermediary region(IR) at the border of the center region(CR) and edge region(ER) is defined, which prevents severe cross-tier interference and is usually ignored by other schemes. Furthermore, a strategic resource allocation scheme is proposed, which allows macro users in this new region to be served more resources due to their good channel conditions close to the serving base station(BS), while femto users are assigned resource blocks from sub-bands that receive the least net interference from a set of usable sub-bands in any region. We find by analysis and simulation the optimal threshold for IR, which minimizes the cross-tier interference, and show that the femto throughput is also maximized for this threshold. Numerical results show the proposed scheme outperforms other notable schemes in terms of throughput and outage performances.

Solving Dynamic Spectrum Management Problem Based on Cloud Computing Using Genetic Algorithm

With the rapid development of wireless sensor network （WSN）, the demands of limited radio frequency spectrum rise sharply, thereby dealing with the frequency assignment of WSN scientifically and efficiently becomes a popular topic. To improve the frequency utilization rate in WSN, a spectrum management system for WSN combined with cloud computing technology should be considered. From the optimization point of view, the study of dynamic spectrum management can be divided into three kinds of methods, including Nash equilibrium, social utility maximization, and competitive economy equilibrium. In this paper, we propose a genetic algorithm based approach to allocate the power spectrum dynamically. The objective is to maximize the sum of individual Shannon utilities with the background interference and crosstalk consideration. Compared to the approach in [1], the experimental result shows better balance between efficiency and effectiveness of our approach.

Hierarchical Ni-plated melamine sponge and MXene film synergistically supported phase change materials towards integrated shape stability,thermal management and electromagnetic interference shielding

Along with the integrated and miniaturized development of advanced electronic devices,phase change materials(PCMs)simultaneously with efficient thermal management and high electromag-netic interference(EMI)shielding effectiveness(SE)are ungently demanded.Herein,the shape-stabilized MXene/Ni-platted melamine sponge/Regenerated cellulose/Graphene nanoplate/Polyethylene glycol(MX/Ni@MS/RCG/PEG)composite PCMs comprising hierarchical Ni@MS/RCG and MXene film were fabricated via a facile encapsulation approach.Hierarchical Ni@MS/RCG hybrid aerogel was prepared by electroless plating and sol-gel methods,and MXene film was obtained using vacuum-assisted filtra-tion procedure.The synergistic effect of conductive Ni@MS/RCG networks and tight MXene film endows MX/Ni@MS/RCG/PEG composite PCMs with good shape stability,high cyclic reliability,large latent heat of phase change(154.3 J g^(–1)),excellent thermal conductivity(TC,0.47 W m^(–1)K^(–1))and favorable EMI shield-ing performance(32.7 dB).The TC of acceptable 0.47 W m^(–1)K^(–1)is observed for MX/Ni@MS/RCG-5/PEG at a rather low GNP content of merely 0.39 wt%.In addition,the temperature variation of MX/Ni@MS/RCG-5/PEG is a lot faster than that of pure PEG in the heating/cooling process,revealing the remarkable energy storage and release efficiency for the composite PCMs.This investigation has taken an important step to-wards shape-stabilized composite PCMs with both effective thermal management and high EMI SE for promising applications in electronic packaging and advanced energy.

Dynamic Interference Coordination With Analytical Near-Optimal Power Allocation Toward High User Fairness

To mitigate interference on celledge users and improve fairness of the whole system, dynamic inter-cell interference coordination(ICIC) is one of the promising solutions. However, traditional dynamic ICIC is considered as an NP-hard problem and power variability further adds another dimension to this joint optimization issue, making it even more difficult to quickly reach a near-optimal solution. Therefore, we theoretically obtain the closed-form expression of the near-optimal power allocation ratio for users in adjacent cells paired in the same resource block and interfere each other, so that the total utility corresponding to α-fairness is maximized. Dynamic ICIC using this closed-form solution could improve user fairness without causing an increment of the computational complexity. Numerical results show that, compared with the schemes using identical power for different users, our method does not obviously degrade the system's average spectral efficiency.