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This work studied and compared the performances of VNN and RBF-NN models by variation of their individual intermediate layer neurons for effective prediction of electromagnetic signal power loss exerting measured data from micro-cell LTE environment. Their architectural structure, their individual characteristics and their training and prediction abilities in the prediction of signal power loss were studied and analyzed. Two different training techniques, the early stopping training technique and the Bayesian Regularization training technique were exerted for the training process and their performances compared. Results show superiority in the prediction of the measured dataset using 50 neurons in the intermediate layer of VNN and 70 neurons in the fixed intermediate layer of RBF-NN over all other various neuron number considered. Also, there is improved prediction using VNN over RBF-NN on application of Bayesian Regularization training technique and better performance using Bayesian Regularization training technique in comparison to early stopping training technique due to the ability of the Bayesian Regularization training technique to reduce both variance and bias during network training leading to improved generalization of the network. However, early stopping technique reduces variance but not bias. The VNN shows superior performance in the signal power loss prediction with the least RMSE, MAE, SD and highest r in comparison with the training results of RBF-NN model which requires more number of neurons in its fixed intermediate layer for more appropriate training. Also, training VNN requires lesser training time in comparison to training using RBF-NN model. The RBF-NN however shows good prediction performance in modeling of complex network. As the neuron numbers in the fixed intermediate layer get bigger, there prediction ability increases with better result output. Notwithstanding, training using RBF-NN requires more training time in comparison to training employing VNN. [ABSTRACT FROM AUTHOR]

Modern cellular communication networks are already being perturbed by large and steadily increasing mobile subscribers in high demand for better service quality. To constantly and reliably deploy and optimally manage such mobile cellular networks, the radio signal attenuation loss between the path lengths of a base transmitter and the mobile station receiver must be appropriately estimated. Although many log-distance-based linear models for path loss prediction in wireless cellular networks exist, radio frequency planning requires advanced non-linear models for more accurate predictive path loss estimation, particularly for complex microcellular environments. The precision of the conventional models on path loss prediction has been reported in several works, generally ranging from 8–12 dB in terms of Root Mean Square Error (RMSE), which is too high compared to the acceptable error limit between 0 and 6 dB. Toward this end, the need for near-precise machine learning-based path loss prediction models becomes imperative. This work develops a distinctive multi-layer perception (MLP) neural network-based path loss model with well-structured implementation network architecture, empowered with the grid search-based hyperparameter tuning method. The proposed model is designed for optimal path loss approximation between mobile station and base station. The hyperparameters examined include the neuron number, learning rate and hidden layers number. In detail, the developed MLP model prediction accuracy level using different learning and training algorithms with the tuned best values of the hyperparameters have been applied for extensive path loss experimental datasets. The experimental path loss data is acquired via a field drive test conducted over an operational 4G LTE network in an urban microcellular environment. The results were assessed using several first-order statistical performance indicators. The results show that prediction errors of the proposed MLP model compared favourably with measured data and were better than those obtained using conventional log-distance-based path loss models. [ABSTRACT FROM AUTHOR]

The provision of enhanced user experience with higher-data transmission speed over the radio frequency channels was one of the core objectives of evolving Long Term Evolution (LTE), which is a 4th generation of cellular broadband communication standard. LTE was developed to supports data transmission speed up to 300 Mbps and 75 Mbps in downlink and uplink, respectively, utilizing a robust multiplexing technique. For mobile radio networks operators to maintain high operability around the ever increasing and demanding subscribers, periodic evaluation, quantitative estimation and analysis of network performance is pivotal. There exist a quantum of previous research works on LTE system network performance that have been conducted both at spatial domain and temporal domain, but the authors concentrated their studies either on practical LTE radio coverage issues only or on general LTE network performance issues using analytical/simulation techniques. In this contribution, a combined statistical and machine learning approach is proposed and applied to provide an in-depth user data throughput performance of operational LTE networks in relation to signal coverage and signal quality parameters, using in typical microcellular built-up terrains as case study. Specifically, the impact of transmitter- receiver communication distance, received signal reference power, received Signal reference quality, Signal to Noise Ratio, Received Signal Strength and Channel Quality Indicator on user throughput over Radio Link Control, Physical Downlink Shared Channel and Packet Data Convergence Protocol layers have been shown using professional TEMS investigation tools. Particularly, for the purpose of effective LTE system network planning and management, the most influencing signal coverage and signal quality parameters on user throughput performance are also examined and shown in the framework of Self-organsing map (SOM) and statistical correlation stratagems. [ABSTRACT FROM AUTHOR]

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Service demand in cellular radio networks is generally heterogeneous and non uniform, leading to asymmetrical topologies. This complexity along with the multiple radio access technologies, the radio channel and practical constraints, make the radio network planning process a challenging task that leaves little room for intuitive solutions. In this paper we formulate the framework that allows for radio network planning analysis to be performed in the context of an evolutionary macro–micro-relay combination approach, or wide area microcell deployments. Coverage, capacity and cost requirements as well as different practical constraints such as reuse of existing 2G and 3G sites, are considered along with a multi-objective optimization algorithm adapted to the radio network planning problem for 4G systems. Among other things, the produced results highlight two key issues: (a) the way towards high capacity radio networks is to replace macrocells with a number of microcells that is more than one order of magnitude higher, (b) optimizing the radio network deployment can reduce the cost/Mbps/km2 by factors of 4 to 20, compared to equivalent macrocellular reference scenarios. [ABSTRACT FROM AUTHOR]

Wireless content caching in small cell networks has recently been considered as a promising way to alleviate the congestion of the backhaul in emerging heterogenous cellular network. However, how to select files which are cached in SBSs and how to make SBSs work together is an important issue for cooperative cache research for the propose of reducing file download time. In this paper, a Cooperative-Greedy strategy (CGS) among cache-enabled small base stations (SBSs) in small cell network is proposed, in order to minimize the download time of files. This problem is formulated as a Chinese restaurant game. Using this game model, we can configure file caching schemes based on file popularity and the spectrum resources allocated to several adjacent SBSs. Both the existence and uniquencess of a Nash equilibrium are proved. In the theoretical analysis section, SBSs cooperate with each other in order to cache popular files as many as possible near UEs. Simulation results show that the CGS scheme outperforms other schemes in terms of the file-download time. [ABSTRACT FROM AUTHOR]

To ensure reliable and secure communication in heterogeneous cellular network (HCN) with imperfect channel state information (CSI), we proposed a coordinated multipoint (CoMP) transmission scheme based on dual-threshold optimization, in which only base stations (BSs) with good channel conditions are selected for transmission. First, we present a candidate BSs formation policy to increase access efficiency, which provides a candidate region of serving BSs. Then, we design a CoMP networking strategy to select serving BSs from the set of candidate BSs, which degrades the influence of channel estimation errors and guarantees qualities of communication links. Finally, we analyze the performance of the proposed scheme, and present a dual-threshold optimization model to further support the performance. Numerical results are presented to verify our theoretical analysis, which draw a conclusion that the CoMP transmission scheme can ensure reliable and secure communication in dense HCNs with imperfect CSI. [ABSTRACT FROM AUTHOR]

In this paper, a full-duplex NOMA relaying based underlay device-to-device (D2D) communication scheme is proposed, in which D2D transmitter assists cellular downlink transmission as a full-duplex relay. Specifically, D2D transmitter receives signals from base station and transmits the superposition signals to D2D receiver and cellular user in NOMA scheme simultaneously. Furthermore, we investigate the power allocation under the proposed scheme, aiming to maximize D2D link's achievable transmit rate under cellular link's transmit rate constraint and total power constraint. To tackle the power allocation problem, we first propose a power allocation method based on linear fractional programming. In addition, we derive closed-form expressions of the optimal transmit power for base station and D2D transmitter. Simulation results show that the performance of two solutions matches well and the proposed full-duplex NOMA relaying based underlay D2D communication scheme outperforms existing full-duplex relaying based D2D communication scheme. [ABSTRACT FROM AUTHOR]

Abstract We introduce the problem of Flexible Allocation on Related Machines with Assignment Restrictions (FARM). In this problem the input consists of a set of machines and a set of jobs. Each machine has a finite capacity, and each job has a resource requirement interval, a profit per allocated unit of resource, and a set of machines that can potentially supply the requirement. A feasible solution is an allocation of machine resources to jobs such that: (i) a machine resource can be allocated to a job only if it is a potential supplier of this job, (ii) the amount of machine resources allocated by a machine is bounded by its capacity, and (iii) the amount of resources that are allocated to a job is either in its requirement interval or zero. Notice that a job can be serviced by multiple machines. The goal is to find a feasible allocation that maximizes the overall profit. We focus on r - FARM in which the required resource of a job is at most an r -fraction of (or r times) the capacity of each potential machine, for some r ≥ 0. FARM is motivated by resource allocation problems arising in cellular networks and in cloud computing. Specifically, FARM models the problem of assigning clients to base stations in 4G cellular networks. We present a 2-approximation algorithm for 1- FARM and a 1 1 − r -approximation algorithm for r - FARM , for any r ∈ (0 , 1). Both are based on the local ratio technique and on maximum flow computations. We observe that an LP-rounding 2-approximation algorithm for the Generalized Assignment Problem also applies to 1- FARM. Finally, we give an Ω (r log r) lower bound on the approximation ratio for r - FARM (assuming P ≠ NP). [ABSTRACT FROM AUTHOR]

The self-organizing network is envisioned as a key technology to future wireless networks, especially for densely deployed small cell scenarios. Self-healing (SH) is an essential functionality to allow the networks to automatically detect and compensate for cell outages, which typically occur when unexpected network failures arise. In this paper, reaping the benefits of machine learning, we propose a novel SH framework in ultra dense small cell networks for meeting the demands of low-cost and fast network operation, quality of service (QoS), and energy efficiency. The proposed SH scheme comprises small cell outage detection (SCOD) and small cell outage compensation (SCOC) to enable self-healing in ultra dense small cell networks. Based on the context information of the partial key performance indicator (KPI) statistics, we propose a novel SCOD algorithm to detect the outage by applying support vector data description (SVDD) approach. The SCOD algorithm detects a small cell outage efficiently considering two situations: KPIs available situation and non-KPIs available situation. Furthermore, in order to compensate the small cell outage, SCOC is formulated as a network utility maximization problem to optimally compensate for the outaged zone in small cell network. A distributed compensation algorithm with low computational complexity is developed to balance the load of small cell networks, considering the QoS provision for users. Simulation results demonstrate that the proposed SH scheme can detect the small cell outage efficiently and can achieve an optimized QoS performance when compensating for the detected small cell outage. [ABSTRACT FROM AUTHOR]

Rapid increase in number of cellular users and high demand for data has lead to the formation of multi-tier networks. Non-orthogonal multiple access (NOMA) has proved to be an efficient method to cater to the paradigm shift from 4G to 5G. This paper employs NOMA in an heterogeneous cellular network consisting of a macro base station (MBS) tier underlaid with femto base station (FBS) tier and device-to-device (D2D) tier, where NOMA is employed in FBS and D2D tier only. The congestion at the MBS tier is relieved by offloading macro users (MU) to the FBS tier. The offloaded MU are further supported by the D2D tier when the FBS tier fails to find a corresponding pairing user for the incoming offloaded MU. Since, absence of pairing user means outage for offloaded MU, D2D cooperation is employed, which decreases the rate outage probability by $86.87\%$ for the MU offloaded as cell edge user (CEU) in comparison to no cooperation. Also, a three times increase in ergodic rate and four times increase in sum ergodic rate for MU offloaded as CEU is achieved using cooperation from D2D tier. Verification of the results is done using Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

Small-cell network is a promising solution to high video traffic. However, with the increasing number of devices, it cannot meet the requirements from all users. Thus, we propose a caching device-to-device (D2D) scheme for small-cell networks, in which caching placement and D2D establishment are combined. In this scheme, a limited cache is equipped at each user, and the popular files can be prefetched at the local cache during off-peak period. Thus, dense D2D connections can be established during peak time aided by these cached users, which will reduce the backhaul pressure significantly. To do this, first, an optimal caching scheme is formulated according to the popularity to maximize the total offloading probability of the D2D system. Thus, most edge users can obtain their required video files from the caches at users nearby, instead from the small-cell base station. Then, the sum rate of D2D links is analyzed in different signal-to-noise ratio (SNR) regions. Furthermore, to maximize the throughput of D2D links with low complexity, three D2D-link scheduling schemes are proposed with the help of bipartite graph theory and Kuhn-Munkres algorithm for low, high, and medium SNRs, respectively. Simulation results are presented to show the effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

Abstract This article addresses the problem of delay mitigation for video streaming applications in congested cellular macro-cells by using a mobile micro-cell mounted on an Unmanned Aerial Vehicle (UAV). Small-scale UAVs are at a mature stage of development and can carry lightweight commercial micro-cells with small form factor. The mobile micro-cell is used to offload users from a congested macro-cell to optimize the bandwidth usage of video streaming applications. The paper proposes algorithms and comprehensive design criteria for user offload selection (selecting what users need to be offloaded to the micro-cell) and drone positioning (selecting the position of the UAV that minimizes the network delay). The effectiveness of the proposed criteria is evaluated through extensive performance analysis. We show that the performance increases consistently in terms of bandwidth requests mitigation and average delay reduction under different system configurations. [ABSTRACT FROM AUTHOR]

In order to solve the contradiction between spectrum resource and system capacity in the mobile communication system and the radius of the housing estate has been decreasing, the microcell has appeared. In this article, the scheme which combined ray tracing and genetic algorithm were studied to solve the problem of urban microcellular network planning. The author used the ray tracing to calculate the propagating characteristics of the micro-cellular scene in a precise way and the genetic algorithm to find the specific location of the urban microcellular base station. And at the same time, basing on the characteristics of the site selection of the urban microcellular base station, the improved genetic algorithm which proposed in the literature was adopted. The final study shows that basing on the simulation of urban microcells, combining with the scheme of the ray tracing and improving genetic algorithm can solve the problem of urban microcell location. [ABSTRACT FROM AUTHOR]

The effects of processing parameters on surface roughness of microcellular injection molded PC parts were investigated. Taguchi design of experiments (DOE) was performed with varying mold temperature, melt temperature, injection rate and supercritical fluid (SCF) concentration. It was found that mold temperature, injection rate and melt temperature appear to be the predominant molding parameters which affect the surface roughness. The results are helpful for designers to optimize the process conditions to achieve high quality microcellular PC part. [ABSTRACT FROM AUTHOR]

One of the goals of Heterogeneous Networks (HetNets) is to offload traffic from the macrocell BS to the microcell base stations (BSs). It has been proposed that in order for the microcell to acquire more users and offload increasing amounts of traffic, its region of coverage must be expanded. This however causes significant cross-tier interference, which can be remedied by utilizing coordinated multipoint (CoMP) within the microcell expanded region (ER). Our methodology considers the effect of overlapping ERs, and proposes the cooperation of concerned microcell BSs with the macrocell BS to further reduce the outage probability and improve throughput. Another important consideration in our analysis is the effect of having non-ideal backhaul on the system’s performance. That is, CoMP increases the strain on the backhaul network, since additional data that is proportional to the number of cooperating BSs needs to travel on the backhaul links. Furthermore, the delay should be minimal and less than one subframe duration in order for reported channel state information to remain valid. With this in mind, our proposed system considers the effect of having non-ideal backhaul in a cellular network with CoMP, while taking into account overlaps in the microcell ERs. [ABSTRACT FROM AUTHOR]

Open microcellular polylactic acid foams with a fibrous polytetrafluoroethylene additive were prepared by a coreback foam injection molding technique. The effects of this fibrous additive on the foam cell structure were investigated. Fibrous polytetrafluoroethylene forms a network structure in polylactic acid in metering and mixing processes. The fibrous polytetrafluoroethylene network increased the viscoelasticity of polylactic acid and provided polylactic acid with a strain-hardening property. The network also provided heterogeneous bubble nucleation sites for physical foaming. However, because of the slow crystallization rate of polylactic acid, the fibrous polytetrafluoroethylene additive did not promote the nucleation of polylactic acid crystals under fast cooling conditions. During fast cooling, such as injection molding cooling conditions, the crystals induced by the fibrous polytetrafluoroethylene network could not behave as bubble nucleation sites. Thus, changes in rheological properties and the increased number of heterogeneous sites contributed to the decrease in cell size, the increase in the number density of cells and the increase in the open cell content. As the number density of cells increased, the cell walls with the fibrous polytetrafluoroethylene fibrous additive became so thin that they could be easily fibrillated by a stretching operation during the coreback operation, while their strain-hardening property prevented the walls from complete breakage. Synergistically conducting cell reduction and stretching (coreback) operations, high expansion ratio foams with high open cell content were prepared. When we adjusted the foaming temperature and holding time, five-fold expansion (i.e. 80% void ratio) foams with cell diameters less than 25 mm and open cell contents (OCC) higher than 80% were produced. [ABSTRACT FROM AUTHOR]

Abstract: A detailed structural analysis of 2D patterns generated by one‐dimensional M‐state additive cellular automata (ACA), where M is a prime (p) to a non‐negative power (t), is performed by using the transition matrix (TM), the barycentric fixed‐mass (BFM) method, and the small‐angle scattering (SAS) technique. The BFM method shows that, for M‐state ACA, the subsets of particular states are multifractals. The fractal dimensions of ACA of a given transition rule are shown to be equal at constant p and arbitrary t, and there is a prime p at which the fractal dimensions of different ACA are equal. The SAS technique is shown to be able to differentiate between patterns of such ACA. In addition, SAS can also provide complementary information about the overall size, number of elements, and number of rows generated by ACA. In the case of monofractals, SAS can recover also the scaling factor, which is shown to be, for the M = p t‐state ACA, the inverse of p. The above findings on the 2‐ and 3‐state Rule 90 and Rule 150 are illustrated as idealized models with possible applications toward assembly of nanoparticles into programmable patterns or in modeling biological systems such as fibroblast aggregation, the growth of bacterial colonies, neuronal maps, and virus spreading. [ABSTRACT FROM AUTHOR]

The microcell terrain is the most common wireless network terrain in our life. In order to solve wireless network optimization of weak coverage in the microcell terrain, improve call quality and reduce the cost of the premise, power amplifiers in base stations should be adjusted according to user volume. In this paper, characteristics of microcell topography are obtained after analysis. According to the topography characteristics of different microcells, changes in the number of users at different times have been estimated, meanwhile, the number of scatter users are also obtained by monitoring the PCCPCH RSCP and other parameters. Then B-Spline interpolation method has been applied to scatter users to obtain the continuous relationship between the number of users and time. On this basis, power amplification can be chosen according to changes in the number of users. The methods adopted by this paper are also applied in the engineering practice, sampling and interpolation are used to obtain the number of users at all times, so that the power amplification can be adjusted by the number of users in a microcell. Such a method is able to optimize wireless network and achieve a goal of expanding the area of base stations, reduce call drop rate and increase capacity. [ABSTRACT FROM AUTHOR]

An economic model was analyzed where a new supplier implements the technology of the small cells and positions itself as an incumbent service provider. This provider performs a dynamic reuse of resources to compete with the macrocells service provider. The model was analyzed using game theory as a two-stage game. In the first stage, the service providers play a Stackelberg differential game where the price is the control variable, the existing provider is the leader, and the new supplier is the follower. In the second stage, users’ behavior is modeled using an evolutionary game that allows predicting the population changes with variable conditions. This paper contributes to the implementation of new technologies in the market of mobile communications through analysis of competition between the new small cell service providers (SSPs) and the existing service providers along with the users’ behavior of mobile communications. The result shows that users get a better service, SSP profits are guaranteed, and SSP entry improves users’ welfare and social welfare. [ABSTRACT FROM AUTHOR]

In this paper, using the concept of stochastic geometry, we present an analytical framework to evaluate the signal-to-interference-and-noise-ratio (\textSINR ) coverage in the uplink of millimeter wave cellular networks. By using a distance-dependent line-of-sight (LOS) probability function, the location of LOS and nonLOS users are modeled as two independent nonhomogeneous Poisson point processes, with each having a different pathloss exponent. The analysis takes account of per-user fractional power control (FPC), which couples the transmission of users based on location-dependent channel inversion. We consider the following scenarios in our analysis: 1) pathloss-based FPC (PL-FPC) which is performed using the measured pathloss and 2) distance-based FPC (D-FPC) which is performed using the measured distance. Using the developed framework, we derive expressions for the area spectral efficiency and energy efficiency. Results suggest that in terms of \textSINR coverage, D-FPC outperforms PL-FPC scheme at high \textSINR where the future networks are expected to operate. It achieves equal or better area spectral efficiency and energy efficiency compared with the PL-FPC scheme. Contrary to the conventional ultra-high frequency cellular networks, in both FPC schemes, the \textSINR coverage decreases as the cell density becomes greater than a threshold, while the area spectral efficiency experiences a slow growth region. [ABSTRACT FROM PUBLISHER]

We consider heterogeneous industrial networks supporting soft handoff where users with different mobility are assigned to different layers. In other words, the microcells of the lower layer, assign a slow user, macrocells of the upper layer, assign the fast user. If it is not possible to obtain immediately a idle channel to handoff request, can reduce the terminates forced probability to provide handoff queue. Therefore, we propose an admission control four approaches by providing a handoff queue macrocells and microcells. In consideration of the system in multidimensional birth-death process, we derive the mathematical model by use of the Gauss-Seidel iterative method and steady-state probability distribution. As a result of the analysis, the provision of handoff queue of macrocells and microcells, improvement of performance is increased. [ABSTRACT FROM AUTHOR]

Location update and paging technique are studied widely at traditional single layer (Single-tier) of cellular networks, such as 5G mobile network. We propose and evaluate the location update/paging technique which used the new crossing-layer, which can be used hierarchical macro-cell/micro-cell concept at industrial mobile networks. In this paper, industrial network-based location update is proceeds only in the macro-cell layer which LMA (Local Mobility Area) domain was made from by large macro-cell. An MU (Mobile User) will stay in such the LMA domain for a long time. As a result, location update cost due to the reduced frequency of location update can be reduced. In order to reduce paging delay, when paging load is not high, the paged MU only will be searched in the macro-cell layer. Otherwise, it will be searched at the micro-cell layer which sequential searching method was applied. The operation for the scheme is simple, so the industrial network-based of macro-cell/micro-cell concept can have an advantage because MU can receive signal both overlapped micro-cell and macro-cell. Analytical cost modeling is analyzed and we evaluated delay costs for paging. Numerical results show that the paging delay that a crossing-layer scheme is low occurred in costs low relatively. [ABSTRACT FROM AUTHOR]

We thoroughly investigate the downlink beamforming problem of a two-tier network in a reversed time-division duplex system, where the interference leakage from a tier-2 base station (BS) toward nearby uplink tier-1 BSs is controlled through pricing. We show that soft interference control through the pricing mechanism does not undermine the ability to regulate interference leakage while giving flexibility to sharing the spectrum. Then, we analyze and demonstrate how the interference leakage is related to the variations of both the interference prices and the power budget. Moreover, we derive a closed-form expression for the interference leakage in an asymptotic case, where both the charging BSs and the charged BS are equipped with a large number of antennas, which provides further insights into the lowest possible interference leakage that can be achieved by the pricing mechanism. [ABSTRACT FROM AUTHOR]

With the proliferation and diversification of mobile communication services, the current mobile broadband networks face severe challenges. The progressive video service that will make up the majority of future network traffic has more demands for transmission bandwidth, network capacity, and management flexibility. Moreover, denser connectivity, higher reliability, lower latency, and better interaction impose some great challenges to existing networks. In order to meet these growing demands, a promising approach is to integrate a broadcast network with a cellular network. In this article, we briefly set forth the latest progress on the cellular network and the broadcast network, respectively. Then the logic architecture of the integrated network is given to clarify the functional partitioning. In addition, the physical architecture of the integrated network is presented to enable coordination in different aspects. Some feasible strategies are discussed and several promising technologies are presented. [ABSTRACT FROM AUTHOR]

This paper investigates the energy efficient resource allocation when adding dedicated device-to-device (D2D) communication in the co-located antenna systems (CAS). We consider the user equipments (UEs) are changing over time and the appropriate potential UEs to form D2D pairs are varying with time. Our optimization objective is to maximize the system’s energy efficiency (EE) with the constraints of the maximum transmit power of UEs and D2D pairs in different total power consumption models. Firstly, an algorithm is developed to choose appropriate potential UEs to form D2D pairs in this paper. Then we exploit fractional programming method to obtain optimal energy efficient power allocation solutions. Simulation results are provided to demonstrate the effectiveness of the developed D2D pairs choosing algorithm and the power allocation algorithm. [ABSTRACT FROM AUTHOR]

This paper aims at developing a power control framework to jointly optimize energy efficiency (measured in bit/joule) and delay in wireless networks. A multi-objective approach is taken dealing with both performance metrics, while ensuring a minimum quality-of-service to each user in the network. Each user in the network is modeled as a rational agent that engages in a generalized non-cooperative game. Feasibility conditions are derived for the existence of each player’s best response, and used to show that if these conditions are met, the game best response dynamics will converge to a unique Nash equilibrium. Based on these results, a convergent power control algorithm is derived, which can be implemented in a fully decentralized fashion. Next, a centralized power control algorithm is proposed, which also serves as a benchmark for the proposed decentralized solution. Due to the non-convexity of the centralized problem, the tool of maximum block improvement is used, to tradeoff complexity with optimality. [ABSTRACT FROM PUBLISHER]

Wireless self-backhauling is a promising solution for dense millimeter wave (mmWave) small cell networks, the system efficiency of which, however, depends upon the balance of resources between the backhaul link and access links of each small cell. In this paper, we address the discrete power control and non-unified transmission duration allocation problem for self-backhauling mmWave cellular networks, in which each small cell is allowed to adopt individual transmission duration allocation ratio according to its own channel and load conditions. We first formulate the considered problem as a non-cooperative game \mathcal G with a common utility function. We prove the feasibility and existence of the pure strategy Nash equilibrium (NE) of game \mathcal G under some mild conditions. Then, we design a centralized resource allocation algorithm based on the best response dynamic and a decentralized resource allocation algorithm (DRA) based on control-plane/user-plane split architecture and log-linear learning to obtain a feasible pure strategy NE of game \mathcal G . For speeding up convergence and reducing signaling overheads, we reformulate the considered problem as a non-cooperative game ${{\mathcal {G}}'}$ with local interaction, in which only local information exchange is required. Based on DRA, we design a concurrent DRA to obtain the best feasible pure strategy NE of game {\mathcal {G}'} . Furthermore, we extend the proposed algorithms to the discrete power control and unified transmission duration allocation optimization problem. Extensive simulations are conducted with different system configurations to demonstrate the convergence and effectiveness of the proposed algorithms. [ABSTRACT FROM AUTHOR]

Coded caching has emerged as a promising component of solutions to the exponential growth in network traffic. Previous approaches to network coding are all based on (simple) XOR coding, which is appropriate when links have the same rate. However, in typical wireless networks, different users experience different link rates. Thus, XOR coding is sub-optimal and cannot achieve full broadcast gain. In this paper, we consider the coded caching design for wireless networks with unequal link rates. More specifically, the backhaul networks of LTE-A or 5G system are considered, in which the link rates between the macroBS and microBSs are different. We leverage a new network coding scheme nested coded modulation (NCM) in the delivery phase and develop a novel file partition scheme for the placement phase based on unequal cache size allocation. This scheme adapts to unequal link rates for increasing broadcast gains. The achievable transmission time and the information-theoretic lower bound are derived; we show that transmission time of the NCM-based coded caching can achieve a constant gap to the lower bound. Moreover, the NCM-based coded caching can achieve significant performance improvement over the XOR-based coded caching; the example with normalized link rates from 1 to 6 achieves up to 250% throughput improvement. Numerical results also show that the NCM-based coded caching can well utilize the unequal link rates, which cannot be achieved by the XOR-based coded caching. [ABSTRACT FROM PUBLISHER]

The concept of site diversity is one of the fade mitigation techniques for radio communication system to overcome severe attenuation during an intense rainy condition. In this study, the performance of experimental findings during the threeyear rainy periods (2011-2013) at a tropical location, Akure (7.17°N, 5.18°E), Nigeria, using measurements from tipping bucket rain gauge network is presented to estimate and model site diversity fades mitigation over Earth-space links in the region. Timespecified rain attenuation is generated from the micro-rain cells over the site using Synthetic Storm Techniques by converting rain rate at the specified time and site into rain-induced attenuation time-series to obtain the diversity gain necessary to counter the severe rain events at Ku/Ka-bands frequency. Based on the micro-cell site diversity result, a modified site diversity gain prediction model has been proposed for different rainy periods: namely: onset, long-rainy and cessation of rainy months. Results are compared with the existing site diversity models. The modified model which incorporated seasonal influences show improved estimation capability better than the International Telecommunication Union-Recommendations (ITU-R) diversity gain model for this location. The overall result will enhance the performance of radio signal transmission along Earth-space paths under intense rainy event in this tropical environment. [ABSTRACT FROM AUTHOR]

Isabona et al. [[5]] developed a multilayer perceptron neural network for optimal predictive modeling in urban microcellular radio environments. The rapid development of information technology opens up new opportunities in many areas of human activity. Particular attention is paid to the study of the mathematical foundations of information processing methods, quantum computing, artificial intelligence, digital image processing, and the use of information technologies in medicine. [Extracted from the article]

The exponential growth in data traffic and dramatic capacity demand in fifth generation (5G) have inspired the move from traditional single-tier cellular networks toward heterogeneous cellular networks (HCNs). To face the coming trend in 5G, the high availability requirement in new applications needs to be satisfied to achieve low latency service. Usually, these applications require an availability of six nines or even higher. In this paper, we present a tractable multitier multiband availability model for spectrum aggregation-based HCNs. We first derive a closed-form expression for the availability of spectrum aggregation-based HCNs using the signal-to-interference-plus-noise model. By doing so, we formulate two optimization problems, one is to maximize the average availability, and the other one is to minimize the average power consumption. These two optimization problems are both nonconvex problems, which are challenging to solve. To cope with them, we propose to apply genetic algorithm for the joint user equipment (UE) association, subcarrier assignment, and power allocation problem. Our results show that the average availability in spectrum aggregation-based HCNs improves with decreasing number of UEs, as well as increasing power budget ratio. We also show that increasing the maximum number of aggregated subcarriers decreases the average power consumption, but cannot guarantee the substantial improvement of average availability. [ABSTRACT FROM PUBLISHER]

With huge bandwidth available in the mmWave band, wireless backhaul at mmWave frequencies can be a promising backhaul solution for small cells densely deployed underlying the homogeneous macrocells. With multiple links under such mmWave wireless network, it is desired to have a scheduling mechanism that can effectively improve the capacity of network with Quality of Service (QoS) considered. In this paper, we propose the regret benefit ratio scheduler (RBRS) that can maximize the number of links with their QoS requirements satisfied. Our proposed indicator, called regret benefit ratio (RBR), allows us to simultaneously maximize the QoS benefit and minimize contention among links under directional antennas. We design RBRS for a time slot based centralized control mmWave network in which we utilize RBR to find suitable concurrent transmission links for every single time slot. Furthermore, we also propose a distributed scheme under Carrier-sense multiple access with collision avoidance (CSMA/CA), which implements the RBR by prioritizing Medium Access Control (MAC) contention window to provide better concurrent transmission support while achieving the QoS-aware capability. Simulations in the 73-GHz band are conducted to demonstrate the superior performance of our algorithm under different criteria. [ABSTRACT FROM PUBLISHER]

We provide a theoretical framework for the study of massive multiple-input multiple-output (MIMO)-enabled full-duplex (FD) cellular networks in which the residual self-interference (SI) channels follow the Rician distribution and other channels are Rayleigh distributed. In order to facilitate bi-directional wireless functionality, we adopt: 1) in the downlink (DL), a linear zero-forcing (ZF) with SI-nulling precoding scheme at the FD base stations and 2) in the uplink (UL), an SI-aware fractional power control mechanism at the FD mobile terminals. Linear ZF receivers are further utilized for signal detection in the UL. The results indicate that the UL rate bottleneck in the FD baseline single-input single-output system can be overcome via exploiting massive MIMO. On the other hand, the findings may be viewed as a reality-check, since we show that, under state-of-the-art system parameters, the spectral efficiency gain of FD massive MIMO over its half-duplex counterpart is largely limited by the cross-mode interference between the DL and the UL. In point of fact, the anticipated twofold increase in SE is shown to be only achievable when the number of antennas tends to be infinitely large. [ABSTRACT FROM AUTHOR]

A new scheme to resolve the intra-cell pilot collision for machine-to-machine (M2M) communication in crowded massive multiple-input multiple-output (MIMO) systems is proposed. The proposed scheme permits those failed user equipments (UEs), judged by a strongest-user collision resolution (SUCR) protocol, to contend for the idle pilots, i.e., the pilots that are not selected by any UE in the initial step. This scheme is called as SUCR combined idle pilots access (SUCR-IPA). To analyze the performance of the SUCR-IPA scheme, we develop a simple method to compute the access success probability of the UEs in each random access slot. The simulation results coincide well with the analysis. It is also shown that, compared with the SUCR protocol, the proposed SUCR-IPA scheme increases the throughput of the system significantly, and thus decreases the number of access attempts dramatically. [ABSTRACT FROM PUBLISHER]

This paper studies the optimal frequency reuse for the transmission of multimedia scalable sources, such as embedded images or scalable video, which need unequal error protection or unequal transmission rates in the bitstream. First, we analyze the crossover of the outage probabilities for full and partial frequency reuse cases in terms of the data rate. We prove that we can find a crossover of the outage probability curves for a data rate lower than a given threshold, which is a function of the parameters such as the partial frequency reuse factor and the user location in the cell. Moreover, the crossover point in the signal-to-noise ratio (SNR) is a strictly increasing function of the data rate. On the other hand, for a data rate higher than or equal to the threshold, there is no crossover; for all SNRs, the outage probability of full-frequency reuse is lower than that of partial-frequency reuse. The results are proven for the arbitrary location of a user in a cell, and for an arbitrary partial frequency reuse factor. Furthermore, the results hold, regardless of the numbers of transmit and receive antennas in the multiple-input multiple-output systems of orthogonal space-time block codes, and of the vertical Bell Labs space-time architecture with a zero-forcing linear receiver. Based on the analysis, we propose unequal-frequency reuse for the optimal transmission of scalable sources. The numerical results show that the peak-SNR performance improves when a sequence of scalable packets is transmitted at the subbands governed by unequal-frequency reuse in cellular networks. [ABSTRACT FROM AUTHOR]

Wireless indoor and outdoor microcells (WIOMs) have emerged as a promising means to deal with a high demand of mobile users for a variety of services. Over such heterogeneous networks, the deployment of WIOMs costs mobile/telecommunications company high capital expenditures and operating expenses. This paper aims at optimising the WIOMs taking into account various network communication environments. We first develop an optimisation problem to minimise the number of cells as well as determining their optimal locations subject to the constraints of the coverage and quality-of-service (QoS) requirements. In particular, we propose a binary-search based cell positioning (BSCP) algorithm to find the optimal number of cells given a preset candidate antenna positions. The proposed BSCP algorithm is shown to not only reduce the number of cells for saving resources but also requires a low computational complexity compared to the conventional approaches with exhaustive search over all available sites. Moreover, EDX SignalPro is exploited as a simulation platform to verify the effectiveness of the proposed BSCP for the WIOMs with respect to various propagation modes and antenna parameters of different types, including isotropic, multiple-input single-output and multiple-input multiple-output. [ABSTRACT FROM AUTHOR]

For a time-correlated channel, we consider the differential feedback of the geometrical mean decomposition (GMD) precoder, which is known to be optimal for a number of criteria. When the channel varies slowly, we can expect the optimal GMD precoders of consecutive channel uses to be close. We consider the feedback of the so-called differential precoder and show that it lies in a neighborhood of the identity matrix using matrix perturbation theory. Furthermore, the radius of the neighborhood is shown to be proportional to a time-correlation parameter. Such a characterization allows for subsequent efficient quantization of the differential precoder. We show how to design codewords for the prescribed radius by perturbing the identity matrix and applying QR decomposition on the perturbed matrix. Simulations are given to demonstrate that, with a small feedback rate, the performance of the proposed differential GMD comes close to the case when perfect channel state information is available to the transmitter for slowly time-varying channels like those in indoor and microcellular environments. [ABSTRACT FROM PUBLISHER]

The focus in Mobile communication networks has been addressed to high data rate networks that offer high quality of service. Long Term Evolution Advanced (LTE-A) technology has been the first to completely fulfill 4G requirements. However, performance gains remain limited due to severe interference levels. For this reason, the Inter-Cell Interference (ICI) problem is one of the main challenges in LTE-A systems. In order to deal with this ICI problem, in this paper we propose a novel framework to analyze the fairness of several scheduling techniques when Fractional Frequency Reuse (FFR) schemes are used. We evaluate the system performance of a typical FFR-based LTE-A scenario. Performance results show the optimum values of the Signal to Interference plus Noise Ratio and partition bandwidth for frequency reuse that maximizes the spectral efficiency. Fairness evaluation has been done in terms of the Gini index, showing a trade-off between spectral efficiency and fairness among users. In that sense, the proposed Truncated-Equal Transmission Rate scheduling policy is able to adjust this trade-off by means of a parameter $$\varepsilon$$ . [ABSTRACT FROM AUTHOR]

We derive a full measurement-based parametrization for a 3-D geometry-based stochastic channel model for an urban microcell type of environment at 10 GHz. The measurements were performed with a vector network analyzer and dual polarized virtual arrays at the bandwidth of 500 MHz. The proposed parametrization is validated by channel simulations. Multiple-input multiple-output channel is reconstructed from the measured data and compared with channel generated by the quasi deterministic radio channel generator using the proposed statistical parameters. The capacity and eigenvalue distribution are used as the validation metrics, showing almost perfect match between the reconstructed and simulated channels. [ABSTRACT FROM AUTHOR]

Multihop cellular networks offer a cost-effective solution to the problem of achieving higher capacity and extending coverage by using relay stations (RSs) deployed within the coverage area of a base station (BS). We herein consider directional transmission based on adaptive beamforming in which multiple users are served at the same time using multiple directional beams; this represents one promising technology that could improve the capacity of multihop cellular network. In directional transmission, severe intra-BS/RS, inter-BS-RS, and inter-RS interferences can occur due to the concurrent transmission and accordingly, system performance can be degraded severely. In this paper, we propose resource allocation to maximize the system capacity of multihop cellular networks by taking into account these severe interferences caused in multihop cellular network using directional transmission. To alleviate the problem of high computational complexity, we propose a sub-optimal scheme. A heuristic scheme is also proposed which can be performed in distributed manner with lower computational complexity. Through simulation results, we show that the use of our proposed schemes increases system capacity. [ABSTRACT FROM AUTHOR]

The GSM, CDMA cellular systems are most trendy 2G and 3G digital cellular telecommunications systems, which is widely used throughout the world. These systems have many advantages such as high security, higher quality of call transmission over the long distances, low transmitted power, and enhanced capacity with more efficient utilization of the frequency spectrum. With these advantages these cellular systems have attracted more subscribers with more attention in the field of mobile communications. One of the most attractive features of cellular system is handoff which is a continuation of an active call when the mobile is moving from one cell to another without disconnecting the call. Usually, continuous service is achieved by efficiently designed handoff algorithms. So, efficient handoff algorithms are necessary for enhancing the capacity and QoS of cellular system. In this paper, the handoff analysis for GSM, CDMA cellular networks are done under various propagation models. Various handoff algorithms of GSM are described and also a novel received signal strength (RSS) based GSM handoff algorithm with adaptive hysteresis is analyzed. CDMA Soft handoff algorithm is analyzed and effective soft handoff parameters are estimated for better performance. The Comparison of handoff algorithms is studied based on results. [ABSTRACT FROM AUTHOR]

We consider the downlink of a two-layer heterogeneous network, comprising macrocells (MCs) and small cells (SCs). The existing literature generally assumes independent placements of the access points (APs) in different layers; in contrast, we analyze a dependent placement where SC APs are placed at locations with poor service from the MC layer. Our goal is to obtain an estimate of the number of SCs required to maintain a target outage rate. Such an analysis is trivial if the MCs are located according to a Poisson point process (PPP), which provides a lower bound on performance. Here, we consider MCs placed on a hexagonal grid, which complements the PPP model by providing an upper bound on performance. We first provide accurate bounds for the average interference within an MC when SCs are not used. Then, by obtaining the outage areas, we estimate the number of SCs required within an MC to overcome outage. If resource allocation among SCs is not used, we show that the problem of outage is not solved completely and that the residual outage area depends on whether cochannel or orthogonal SCs are used. Simulations show that a much smaller residual outage area is obtained with orthogonal SCs. [ABSTRACT FROM PUBLISHER]

New local and semi-global tuning methods for a 3D site-specific propagation path loss model based on the uniform theory of diffraction are proposed in this paper. The purpose of the tuning methods is to efficiently incorporate measured data in the prediction process to enhance the accuracy of the path loss model in microcell environments. The performance of the proposed tuning procedures is compared with a third method that corresponds to a global tuning approach based on the least squares error technique. Our results show that the local tuning procedure outperforms any of the other tuning methods, by providing a significant reduction of the mean absolute error, up to 35 % in error reduction was observed. [ABSTRACT FROM AUTHOR]

In Long-Term Evolution (LTE) random access (RA) systems, upon an access failure, the user equipment not only performs a backoff to randomly spread the retransmission attempt over a certain time period but also increases the transmission power for the retransmission, which is called a power ramping (PR) scheme. This paper analyzes the RA performance of LTE-based two-tier small-cell networks, in which the PR scheme may be a source of uplink cross-tier interference to the macrocell and small cells. To reduce cross-tier interference, we propose a scheme for partial sharing (PS) of orthogonal random access preambles (RAPs), in which small cells are allowed to use a subset of RAPs, whereas the macrocell uses the whole set of RAPs. We compare the PS scheme with a full-sharing scheme, in which the entire set of RAPs is shared by the macrocell and small cells. Our study characterizes the RA performances of LTE-based two-tier small-cell networks in terms of throughput, access delay, mean power consumption, and RAP-dropping probability and shows the benefits of the PS scheme and its trade-off between throughput and access delay of small cells. [ABSTRACT FROM PUBLISHER]

In a massive multiple-input–multiple-output (MIMO) uplink system, the pilot sequence reuse in neighboring cells causes pilot contamination, causing the decoding performance to degrade significantly. In this paper, a blind decoding method based on independent component analysis (ICA) is proposed without using pilot sequences. The proposed blind decoding method uses ICA to separate the received signals (from in-cell and neighboring cells) and estimate channels. The energy levels of the estimated channels are used to differentiate an in-cell signal from neighboring cell signals. The analytical performance results of the blind decoding method are derived. Numerical results show that the proposed blind decoding scheme outperforms minimum-mean-square-error (MMSE) decoding and zero-forcing (ZF) decoding with imperfect channel state information (CSI). The proposed scheme has only a negligible performance loss compared with MMSE decoding and ZF decoding with perfect CSI. [ABSTRACT FROM PUBLISHER]

Being an important application of spectrum sharing in cellular networks, mobile traffic offloading, which advocates third-party owners of network resource on unlicensed/licensed spectrum to share their spectrum and provide data offloading services, is considered a promising solution to severe spectrum shortage faced by cellular network service providers. In this paper, we consider a general mobile traffic offloading system that adopts the widely used Gale–Shapley algorithm to optimize its mobile phone users (MUs) to offloading stations allocation plan. We notice that without careful protection, such a system could cause serious threat to MUs’ location privacy, and thus design effective countermeasures based on the powerful state-of-the-art differential privacy concept. Specifically, we have proposed two joint differentially private Gale–Shapley mechanisms with strong privacy protections for mobile traffic offloading systems. The first mechanism is able to protect each user’s location privacy even when all other users collude against this user assuming the system administrator can be trusted. The second mechanism is able to achieve the same privacy guarantee against colluding users, and moreover against an untrusted semi-honest system administrator. We perform extensive experiments to evaluate our mechanisms, and the results show that our mechanisms have good efficiency, accuracy, and privacy protection. [ABSTRACT FROM PUBLISHER]

In this paper, we propose a novel bandwidth-efficient handoff scheme for proxy mobile IPv6 networks. Mobile nodes (MNs) are classified as either slow or fast; first, though, to implement a bandwidth-efficient handoff scheme, an MN should be registered in a microcell. The microcell is overlapped to handle an overflow session request, which is nested; in a macrocell, an overflow session request makes a request to return from the boundary of the new microcell. If idle session traffic is in a cell, it is requested by the target microcell. If the total systemic traffic load is not very large, the proposed scheme provides the best bandwidth efficiency and a more favorable quality of service (QoS) for an MN without the incurrence of a large systemic processing cost. [ABSTRACT FROM AUTHOR]

We propose a novel handover scheme for indoor microcellular visible light communication (VLC) network. With such a scheme, the room, which is fully coverage by light, is divided into several microcells according to the layout of light-emitting diodes (LEDs). However, the directionality of light arises new challenges in keeping the connectivity between the mobile devices and light source under the mobile circumstances. The simplest solution is that all LEDs broadcast data of every user simultaneously, but it wastes too much bandwidth resource, especially when the amount of users increases. To solve this key problem, we utilize the optical positioning assisting handover procedure in this paper. In the positioning stage, the network manager obtains the location information of user device via downlink and uplink signal strength information, which is white light and infrared, respectively. After that, a Kalman filter is utilized for improving the tracking performance of a mobile device. Then, the network manager decides how to initiate the handover process by the previous information. Results show that the proposed scheme can achieve low-cost, seamless data communication, and a high probability of successful handover. [ABSTRACT FROM AUTHOR]