Heterogeneous Network Scenario Research Articles

Heterogeneous Wireless Network for IoT Applications

ABSTRACTInternet of Things (IoT) can connect billions of devices and services at anytime, anyplace with diverse applications. Heterogeneous network provides Always Best Connected network between the various technologies. We consider a hybrid network among recent Bluetooth and Wi-Fi technologies to provide the IoT applications. Bluetooth low energy (BLE) works with the minimum amount of power and data rate, sufficient to handle the IoT applications. Wi-Fi Alliance also developed the IEEE 802.11ah which is specifically designed for IoT applications. In this paper, we performed heterogeneous wireless network scenario between the advanced IEEE 802.15.1 (BLE) and IEEE 802.11ah (HaLow) based on Receive Signal Strength as threshold parameter for vertical handover. The simulation results show the Bluetooth versions of Basic Rate, BLE, and Wi-Fi (HaLow) network with the data rate increment after the handover.

A Survey of Contract Theory-Based Incentive Mechanism Design in Wireless Networks

The prevalence of high performance mobile devices such as smartphones and tablets has brought fundamental changes to existing wireless networks. The growth of multimedia and location-based mobile services has exponentially increased network congestion and the demands for more wireless access. This has led to the development of advanced techniques to address the resulting challenges based on the concept of cooperation in various heterogeneous network scenarios. Thus, innovative incentive mechanisms in wireless networks are needed to ensure the participation of third party nodes, such as access points, small cells, and users. In this tutorial, we demonstrate the effectiveness of contract theory to design incentive mechanisms for a wide range of application scenarios in wireless networks. In contract theory, participants are offered properly designed rewards based on their performances to encourage better participation. First, we present an overview of basic concepts and models of contract theory, with comparisons to other related methods from economics. We then discuss incentive mechanisms, with a focus on the design of rewards in a contract. We demonstrate how contract theory can be utilized for developing effective incentive mechanisms for emerging wireless network scenarios such as traffic offloading, mobile crowdsourcing, and spectrum trading.

Open Network Database for Application-Based Control in Multilayer Networks

Traffic engineering (TE) solutions are enabled by the adoption of the path computation element (PCE) architecture. Cooperative inter-PCE communications, in combination with TE information export mechanisms, such as the link state extensions to BGP protocol (BGP-LS) enable TE in heterogeneous networks scenarios with different layers, domains, and technologies. Multilayer networks, such as IP/MPLS over elastic optical networks are a typical example of such scenarios. However, these currently adopted export mechanisms are conceived for limited amount of exchanged information in order to preserve scalability, especially if centralized entities are considered, such as PCEs and controllers. Moreover, some information (e.g., router interfaces and transceiver card association) are not always available at the control plane level. Thus, so far limited deployment of interlayer TE procedures has been experienced. In this paper, we propose a novel network element called open network database. Exploiting the state-of-the-art of database platforms while assuring high scalability and reliability performance, dedicated control and management applications run complex reoptimization procedures with a set of ad hoc queries without relying on complex control infrastructure or without overloading the orchestrators, thus simplifying the implementation of network applications and achieving advanced TE. A YANG-based database for interconnected TE networks is proposed and implemented to enable dedicated applications to perform complex multidomain/layer operations. The database is successfully utilized for effective and extremely scalable maintenance applications in multilayer networks.

An evergreen cloud: Optimizing energy efficiency in heterogeneous cloud computing architectures

In a heterogeneous Cloud network scenario where a Cloud computing data center serves mobile Cloud computing requests, Cloud providers are expected to implement more innovative and effective solutions for a list of long standing challenges. Energy efficiency in the Cloud data center is one of the more pressing issues near the top of that list. Cloud providers are in constant pursuit of a system that satisfies client demands for resources, maximizes availability and other service level agreement metrics while minimizing energy consumption and, in turn, minimizing Cloud providers' cost.In this work, we introduce a novel mathematical optimization model to solve the problem of energy efficiency in a cloud data center. Next, we offer a solution based on VM migration that tackles this problem and minimizes energy efficiency in comparison to other common solutions. This solution includes a novel proposed technique to be integrated in any consolidation-based energy efficiency solution. This technique depends on dynamic idleness prediction (DIP) using machine learning classifiers. Moreover, we offer a robust energy efficiency scheduling solution that does not depend on live migration. This technique, termed Smart VM Over Provision (SVOP), offers a major advantage to cloud providers in the cases when live migration of VMs is not preferred due to its effects on performance. We evaluate the aforementioned solutions in terms of a number of critical metrics, namely, energy used per server, energy used per served request, acceptance rate, and the number of migrations performed.

On Energy-Efficient Edge Caching in Heterogeneous Networks

In this paper, we study the problem of content placement for caching at the wireless edge with the goal to maximize the energy efficiency (EE) of heterogeneous wireless networks. In particular, we consider the minimization of two fundamental metrics: the expected backhaul rate and the energy consumption. We derive both metrics in closed-form expressions, and we solve the minimization problem as a convex optimization for each, highlighting the existence of a tradeoff between the two metrics. Further, we show the advantage of encoding the data using maximum-distance separable (MDS) codes over the alternative concept of file fragmentation, with respect to both backhaul rate and energy consumption. Then, we thoroughly study the performance of the optimal MDS-encoded caching scheme in terms of overall energy consumption for an important heterogeneous network scenario. We compare our optimal strategy to several other sub-optimal caching strategies, including the caching scheme, minimizing the backhaul rate, and we analyze the effects of the system parameters on the overall performance. Our analysis can be generalized to any network topology and to any small-cell base station capability. Our results show that the optimal placement of MDS-encoded content in caches at the wireless edge increases significantly the overall EE of the heterogeneous network. This demonstrates the importance of the edge caching strategy for energy-efficient network designs.

Introduction to QAM-FBMC: From Waveform Optimization to System Design

The asynchronous heterogeneous network scenario is becoming one of the key features for 5G mobile communications. Compared to CP-OFDM, which is 4G waveform, superior spectrum confinement as well as higher spectral efficiency has been taken into consideration for 5G waveform design. In this article, we introduce a new waveform called QAM-FBMC that provides superior spectrum confinement and higher spectral efficiency simultaneously against CP-OFDM. The article explains fundamental trade-offs in waveform design and shows how they can be optimized for QAM-FBMC. We also introduce the transmission and reception procedures for QAM-FBMC including its similarities and differences compared to well-known waveforms such as CP-OFDM and OQAM-FBMC. Performance evaluation results show where the spectral efficiency gain of QAM-FBMC over CP-OFDM comes from.

An Enhanced QAM-FBMC Scheme With Interference Mitigation

Cyclic prefixed orthogonal frequency division multiplexing (CP-OFDM) has been used as a waveform for mobile communications, but CP-OFDM has weaknesses in an asynchronous heterogeneous network scenario. To overcome the disadvantage of CP-OFDM, a quadrature amplitude modulation (QAM)-filter-bank-based multi-carrier (FBMC) system is proposed to achieve superior spectrum confinement and better spectral efficiency. However, QAM-FBMC has inevitable performance degradation because of interferences from non-orthogonal filters. In this letter, we propose a decision feedback equalization (DFE)-based interference mitigation scheme for the QAM-FBMC system to cancel a residual interference. The interference from the filters of QAM-FBMC influences to other subcarriers and symbols, and it is modeled as an end-to-end system transfer function with para-Hermitian poly-nomial matrix form, equivalently. By spectral factorization of the system transfer function, the system response is transformed into causal, and the receiver detects the symbols successively. This letter describes the spectral factorization method and formulates the feed-forward and feedback filter of the DFE structure with the spectral factor of transfer function. Simulation results show the superiority of the proposed scheme to the conventional QAM-FBMC receiver scheme.

Softwarecast: A code-based delivery Manycast scheme in heterogeneous and Opportunistic Ad Hoc Networks

In the context of Opportunistic Ad Hoc Networking paradigms, group communication schemes (Manycast) are difficult to conduct. In this article, we propose a general delivery scheme for Manycast group communications based on mobile code. Our proposal extends network addressing by moving from the static header field paradigm to a software code-based addressing scheme. We allow messages to be delivered using built-in software codes that consider application-defined, context-aware or history-based information. Additionally, we allow messages to carry a delivery state that permits them to perform refined delivery-decision-making methods. As a consequence of this scheme, we have found that new group communication schemes, besides the traditional ones, may be beneficial to improve the network performance and to provide new functionalities to emerging scenarios like intermittently connected networks of heterogeneous physical objects. We present an application of this scheme to solve, following an analytical delivery method, the problem of sending a message to k and only k nodes of a heterogeneous and opportunistic network scenario that fit best a given criterion. We show, using simulations, that our proposal performs better than traditional approaches. Finally, to show that our proposal is feasible, we present an implementation of our proposal in a real Opportunistic Ad Hoc network, a DTN network, compatible with the de facto standard Bundle Protocol.

Automatic clustering algorithms for indoor site selection in LTE

Small cell systems are a cost-effective solution to provide adequate coverage inside buildings. Nonetheless, the addition of any indoor site requires evaluating the trade-off between the coverage and capacity gain provided by the new site and its monetary cost. In this paper, a new automatic indoor site selection algorithm based on clustering techniques is presented. The algorithm calculates the number of antennas, radio heads, and baseband units needed for the area under study. Then, a clustering algorithm groups several radio heads of different buildings in a single pooled baseband unit, reducing deployment costs. The proposed clustering algorithm is based on a local refinement algorithm, whose starting point considers a new baseband unit for every new site, and then, possible reallocation to existing units is checked. To assess the method, the proposed indoor site selection algorithm is included in a network planning tool. The algorithm is tested in a real heterogeneous network scenario, taking into account vendor specifications and operator constraints. Results show that the use of the proposed clustering algorithm can reduce the total network cost by up to 58 % in a real scenario.

Cooperative Spectrum Sensing in Heterogeneous Cognitive Radio Networks Based on Normalized Energy Detection

Spectrum sensing is an essential technology to detect the presence of primary users' (PUs) signals in cognitive radio (CR) networks. To achieve desirable performances under shadowing and fading environments, cooperative spectrum sensing has been proposed as a promising scheme, which takes advantage of spatial and multiuser diversity gain. In this paper, we investigate cooperative sensing (CS) in a heterogeneous CR network scenario, where each secondary user (SU) may be equipped with different numbers of receive antennas and may have different signal processing capabilities, e.g., sampling rates. By considering the discrepancy in sensing reliability of different SUs, we propose an optimal normalized energy detection-based CS (NED-CS) scheme by virtue of the principle of log-likelihood ratio test (LRT). This LRT-based NED-CS scheme also takes into account the reporting errors at a fusion center (FC), which may receive erroneous results from some SUs due to channel fading and quantization errors. Our derivation shows that the detection statistic of our proposed LRT-based NED-CS scheme is the linear combination of modified local detection statistics, and the optimal combining coefficient can be shown to be a function of the numbers of antennas, the received signal samples, the received signal-to-noise ratios (SNRs), and the variances of reporting errors at each SU. Meanwhile, to drop the prerequisite on a priori information on the received SNRs of all SUs and the variances of reporting errors and to simplify the decision making and threshold setting, a simplified LRT (SLRT)-based NED-CS scheme is proposed as well. Furthermore, we analyze and compare the performance of our proposed LRT-based NED-CS scheme with existing NED-CS schemes, including the equal gain combination (EGC) method and the maximum normalized energy (MNE) detector, with reporting errors under both additive white Gaussian noise (AWGN) and Rayleigh fading channels in a heterogeneous CR network. We derive the probability density function (PDF) of received SNR at each SU and obtain the series expansions and closed-form approximate expressions of detection and false alarm probabilities of our proposed LRT-based NED-CS scheme. Our analytical results match simulation results well, and both of them show that the proposed LRT- and SLRT-based NED-CS schemes perform significantly better than the existing EGC and MNE methods.

A Decentralized MAC Protocol for Unfairness Problems in Coexistent Heterogeneous Cognitive Radio Networks Scenarios With Collision-Based Primary Users

Cognitive radio (CR) is introduced to improve spectrum efficiency by unlicensed usage when a licensed band is idle. These devices monitor licensed users to find spectral opportunities for transmission. A cognitive radio network (CRN) is defined as a structure, which is constructed by both licensed users and unlicensed CR users. In an effort to improve spectrum efficiency, CR users' spectrum issues have been widely studied over the last few years. However, the existing solutions are not capable of dealing with the following scenario: multiple CRNs operating simultaneously without a centralized coordinator. This issue is often referred to as a coexistence problem of heterogeneous CRNs. This problem is caused in a distributed framework of CRNs without a centralized component to negotiate spectrum usages with one another. The system characteristics of these heterogeneous networks are different; thus, the fairness issue between CR users must be considered. In this paper, a decentralized solution that does not limit the hardware capacity of a CR device is proposed as an added fairness feature. Several Markov chain models are proposed to study these unfairness conditions, and a medium access control layer approach is introduced. Numerical and simulation results are presented to verify the proposed solution.

Tilt Angle Optimization in Two-Tier Cellular Networks—A Stochastic Geometry Approach

In this work, we address the antenna tilt optimization problem for a two-tier cellular network consisting of macrocells and femtocells, where both tiers share the same spectrum and their positions are modeled via two independent Poisson point processes (PPPs). First, we derive the coverage probability for a traditional cellular network consisting only of macrocells and obtain the optimum tilt angle that maximizes the overall energy efficiency (EE). Gains of up to 400% in EE were found for a scenario (approximately) equivalent to a hexagonal cell deployment with cell radius of 200 m when the optimum tilt was selected. We then proceed to model the heterogeneous network (HetNet) scenario where femtocells are also deployed in the network's area. We observe that the macrousers performance is highly sensitive to the interference emanating from the femtocell tier. In order to circumvent this issue, interference coordination employing a guard zone for the macrocell user is proposed. Subsequently, we formulate a joint optimization problem where we derive both, the radius of a guard zone protecting the macrouser and the tilt angle that maximize the EE of the network.

Cognitive Optical Network Testbed: EU Project CHRON [Invited

The aim of cognition in optical networks is to introduce intelligence into the control plane that allows for autonomous end-to-end performance optimization and minimization of required human intervention, particularly targeted at heterogeneous network scenarios. A cognitive network observes, learns, and makes informed decisions based on its current status and knowledge about past decisions and their results. To test the operation of cognitive algorithms in real time, we created the first operational testbed of a cognitive optical network based on the Cognitive Heterogeneous Reconfigurable Optical Network (CHRON) architecture. In this experiment, an intelligent control plane, enabled by a cognitive decision system (CDS), was successfully combined with a flexible data plane. The testbed was used to test and validate different scenarios, demonstrating benefits obtained by network cognition, particularly lightpath establishment and a teardown scenario, improved failure restoration time, cognitive virtual topology reconfiguration, and a modulation format change.

Study on Access Selection of Heterogeneous Wireless Network in the View of Evolutionary Game

Along with the continuous development of wireless communication technology and popularization of multi- mode terminal, the seamless fusion of various heterogeneous wireless networks has gradually become the trend of net- work development. The diversified forms of network access enable the multi-mode terminal to dynamically select the ac- cess network with the highest utility value to obtain network service according to specific standard. The study selects a typical heterogeneous network scenario, abstracts users' network selection process to be group game model, adopts the evolutionary methods, and then studies user's network selection process through replicator dynamics. On the basis of it, it puts forwards a kind of network selection algorithm in the view of replicator dynamics and verifies its algorithm perfor- mance through simulation results, and then analyzes the impact of different factors on evolutionary equilibrium in detail.

Backhaul-aware energy efficient heterogeneous networks with dual connectivity

In this paper, we consider backhaul-aware mechanisms for energy efficient operation of next generation heterogeneous wireless networks, with dense small cell deployments. We assume control and data plane separation based on the LTE-Advanced dual connectivity architecture. The mechanisms are evaluated using LTE-Advanced heterogeneous network scenarios, with varying levels of network densities, user traffic and cell load conditions. For comparison, conventional traffic offloading schemes based on small cell proximity and load are also evaluated. The performance results indicate significant energy saving (ES) gains for the backhaul-aware mechanism, depending on the backhaul technology used. Evaluations were also done on the impacts of user mobility, and for indoor and outdoor deployments of small cells. Trade-offs between user throughput and energy efficiency are evaluated, and using the considered mechanism, ES gains of up to 20 % is observed, without significant loss in throughput.

A Heuristic Coordination Framework for Self-Optimizing Mechanisms in LTE HetNets

A self-organizing network (SON) is effectively realized by means of specific SON mechanisms (SONm), which relate to particular SON use cases (SONuc), these being defined by the Third-Generation Partnership Project (3GPP) and Next Generation Mobile Networks (NGMN). Typically, SONuc are grouped into self-configuration, self-optimization, and self-healing functions. Focusing on self-optimization, SONm therein aim at maintaining relevant key performance indicators (KPIs) above/below a specific target by actuating over an appropriate set of input parameters to achieve predefined network objectives. Typically, this problem is represented by several control loops where controllable input parameters are dynamically adjusted according to output measurable metrics and their corresponding target requirements. From an implementation viewpoint, the concept of a single SON “black box,” integrating multiple SONm, is very appealing. However, this approach may threaten the control that network operators (NOPs) have over their own network. As a result, a coordinated framework involving stand-alone SONm is proposed. Here, a SON controller (SONc) may be implemented responding to strategies, deciding at a given time which SONm actions have higher priority with respect to others. In the context of a heterogeneous network (HetNet) scenario, we propose and develop a simplified framework where stand-alone SONm react to either overshot or undershot KPI events by deciding to either increase or decrease corresponding influential parameter(s). By inspecting the arising interactions and possible conflicts between several SONm, we provide, for a specific evaluation scenario, a heuristic strategy-based solution for SON coordination, which may eventually trade off high-level NOP goals.

Multicell cooperation for LTE-advanced heterogeneous network scenarios

In this article we present two promising practical use cases for simple multicell cooperation for LTE-Advanced heterogeneous network scenarios with macro and small cells. For co-channel deployment cases, we recommend the use of enhanced interference coordination, or eICIC, to mitigate cross-tier interference and ensure sufficient offload of users from macro to small cells. It is shown how the eICIC benefit is maximized by using a distributed inter-base station control framework for dynamic adjustment of essential parameters. Second, for scenarios where macro and small cells are deployed at different carriers an efficient use of the fragmented spectrum can be achieved by using collaborative inter-site carrier aggregation. In addition to distributed coordination/collaboration between base station nodes, the importance of explicit terminal assistance is highlighted. Comprehensive system-level simulation results illustrate the performance benefits of the presented techniques.

Middleware Architecture for Next Generation Heterogeneous Networks

In this paper we present a framework, called Futon, which provides a platform to integrate heterogeneous radio access networks. Futon is a hybrid fibre-radio network that replaces legacy base stations with simple remote antenna units, which are connected to a central unit. As a part of the Futon framework, a generic middleware architecture is discussed in detail, which provides interoperability, cooperative management and service provisioning to both underlying radio access networks (RANs) and IP layer for a heterogeneous network scenario. One of the middleware's functionality is to provide vertical handover between heterogeneous IP-based radio access technologies and to ensure seamless mobility and service continuity, which is implemented on top of an IPv4/IPv6 Mobile IP (MIP) core. In this paper, the Futon framework and a generic middleware architecture as a part of Futon framework for heterogeneous RANs is discussed. The main modules of the middleware, namely common radio resource management (CRRM), media independent handover, Service/Connection Manager and link selection are explained in detail. Radio over fibre (RoF) Manager is an important part of Central unit, which does performance, fault and security management of network elements. RoF manager helps middleware during handoff, by providing the status of fibre optic links. The implementation of Security management module as a part of RoF manager, and results of authentication with AAA protocol are explained. The CRRM as part of middleware is simulated and the results of experimental evaluation are presented.

Optimized Burst LSP Design for Absolute QoS Guarantees in GMPLS-Controlled OBS Networks

Over the past decade, the scientific community has thrown itself into assessing optical burst switching (OBS) as the switching technology for next-generation all-optical networks. In this regard, a significant amount of work has concentrated on providing OBS with the required carrier-class features. During this process, however, little attention has been paid to fundamental questions on the interoperability and interworking issues that OBS will have to face in a heterogeneous network scenario such as the future Internet. This article introduces a generalized multi-protocol label switching (GMPLS)-based control plane architecture for future OBS networks. This GMPLS/OBS control plane solution leverages on the GMPLS interoperability to enable seamless vertical and horizontal OBS integration with different switching layers under a common control plane. The burst label switched path (b-LSP) entity has been introduced to accomplish this purpose, as well as to guarantee end-users' quality of service (QoS) requirements to effectively support emerging data applications. The establishment of a b-LSP does not entail explicit resource reservation, but the addition of new entries in the OBS node forwarding tables with the resources available for that b-LSP. Hence, by making a resource available to multiple b-LSPs, the statistical multiplexing nature of OBS is preserved. A mixed integer linear programming formulation has been presented to get the most out of the available resources given the expected traffic demands and their QoS requirements. Moreover, in the network operation phase, GMPLS-driven b-LSP capacity reconfigurations are dynamically triggered whenever unfavorable network conditions are detected. An exhaustive simulation campaign assesses the performance of the proposed GMPLS/OBS network architecture on different network scenarios. Finally, future research lines on the topic are outlined.

Hybrid vehicular communications based on V2V-V2I protocol switching

In this paper, a hybrid communication paradigm for vehicular networking is presented in which connectivity is provided by both existing network infrastructure (e.g. wireless network access points) through a vehicle-to-infrastructure protocol and traditional vehicle-to-vehicle networking. Pre-existing infrastructure can provide seamless connectivity, especially when vehicles are sparse or travelling in disconnected neighbourhoods, while vehicular communications are available for dense traffic scenarios. In this vision, we depict a novel heterogeneous vehicular network scenario, in which overlapping wireless networks partially cover the vehicular grid. Vehicle-to-X (V2X) is based on a protocol switching decision, which is achieved in a distributed fashion by each vehicle based on a cost function using path alternatives. An analytical model for protocol switching in V2X is described. Moreover, we analyse how messages are forwarded by vehicles communicating via V2X. We characterise the maximum and minimum bounds of information propagation and compare performance with traditional message propagation based on opportunistic networking.