Traditional Cellular Systems Research Articles

A Tutorial on Cross-layer Optimization Wireless Network System Using TOPSIS Method

Each other, leading to issues such as interference, limited bandwidth, and varying channel conditions. These challenges require specialized optimization techniques tailored to the wireless environment. In wireless communication networks is to maximize the overall system throughput while ensuring fairness among users and maintaining quality of service requirements. This objective can be achieved through resource allocation optimization, where the available network resources such as bandwidth, power, and time slots are allocated to users in an optimal manner. Optimization-based approaches in wireless resource allocation typically involve formulating the resource allocation problem as an optimization problem with certain constraints.. These techniques provide practical solutions with reduced computational complexity, although they may not guarantee optimality. In summary, optimization-based approaches have been instrumental in studying resource allocation problems in communication networks, including the wireless domain. While techniques from the Internet setting have influenced the understanding of congestion control and protocol design, specific challenges in wireless networks necessitate tailored optimization techniques that account for interference, limited bandwidth, and varying channel conditions. power allocation problem in wireless ad hoc networks Cross-layer optimization refers to the process of jointly optimizing the allocation of resources across different layers of wireless networks, the interactions between different layers become more complex due to the shared medium and time-varying channel conditions. Nash equilibrium, where no user can unilaterally improve its own performance by changing its strategy. Game theory can capture the distributed nature of wireless networks and provide insights into the behavior of users in resource allocation scenarios Additionally, heuristics and approximation algorithms are often employed in wireless resource allocation due to the complexity of the optimization problems involved. In traditional cellular systems, each user is allocated a fixed time slot for transmission, regardless of their channel conditions. However, in opportunistic scheduling. Alternative parameters for “Data rate Ž kbps, Geographic coverage , Service requirements , cost ” Evaluation parameter for “Circuit-switched cell, CDPD, WLAN, Paging, Satellite.” “the first ranking training is obtained with the lowest quality of compensation.”

Research on frequency switching algorithm based on distributed antenna system

Since the traditional cellular cell communication system is no longer suitable for the development needs of the continuously accelerating high-speed railway, the distributed antenna system and the two-hop architecture are used to construct a system network architecture suitable for high-speed railway. Under the architecture of this system, for the problem of frequent handover between remote antenna units (RAUs) under the control of the same centralized unit (CU), this paper proposes an MFC/FSW algorithm by combining the concept of moving frequency concept (MFC) and frequency switching algorithm (FSW). Using FSW to trigger MFC, the frequency of RAU is changed by applying fiber optic radio technology in MFC. Due to the speed change has a greater effect on the success rate of the scheme, a correction factor is defined to mitigate the effect of speed on the success rate. The results show that the scheme can eliminate the traditional switching between RAUs, and the defined correction factor effectively mitigates the effect of the speed on the success rate. Compared with the traditional handover scheme, the switching success rate is not affected by the threshold in the switching judgment condition.

Study of MIMO integration methods with fifth generation technologies

It is expected that with the general deployment of cellular 4G systems the new technologies would be required to satisfy the heightening demand for higher data transfer speeds and lower delays while retaining low deployment and maintenance costs. Multiple array technologies such as MIMO will play a key role in the forthcoming 5G and 6G systems. This paper will present several MIMO architectures and beamforming solutions for cm- and mm-wave 5G systems that work in the 20 (3-30 GHz) and 100 (30-300 GHz) spectrums. These spectrums provide much higher potential for small cell deployment with the use of large-scale antenna arrays due to the higher data capacity than that of the traditional cellular network systems. The mm-wave 5G ELA systems that will gradually replace LTE are going to have higher capacity with the use of Frequency Division Duplexing (FDD) because it enables the usage of uplink/downlink reciprocity in controlling the beamforming operation. It is, however, must be noted that MIMO technology has a key problem that consists of obtaining the necessary information needed to control the transmit and receive algorithms, the solution of which will be discussed in this paper. The array calibration errors that can cause severe performance losses are also going to be considered. The paper therefore will focus on the performance and implementation issues of different multi-user-MIMO (MU-MIMO) solutions for transmission in the cm- and mm-wave bands as well as key problems that follow the transmit MIMO processing for 5G systems. Performance evaluation of RF-based architecture and the traditional baseband transmission methodology for downlink MU-MIMO implementation as well as several transmission schemes to highlight the issues with MU-MIMO for 5G and the solutions to them will be provided.

Rework the Radio Link Budget for 5G and Beyond

The 5th generation of mobile communication system (5G) enables the use of millimeter wave frequency bands and beamforming with narrow-beam directional antennas for mobile communication. Accurate estimation of radio link budget which enables direct assessment of achievable cell range or maximum throughput and facilitates network parametrization before deployment is one of the most challenging problems in radio network planning. In contrast to traditional cellular systems, where omni-directional or sectoral antennas are deployed with half-power beam-width much larger than angular spread of the radio channel, the beam-width of antenna arrays assumed for 5G in sub-6GHz and millimeter wave bands can be comparable to or smaller than channel angular spread in scattering environment. Since the effective antenna pattern is determined jointly by the nominal antenna pattern and channel angular spread, it is no longer appropriate to use nominal pattern in radio link budget analysis or system level simulations. Simplified approach, where nominal pattern is assumed for all typical propagation conditions, results in overestimation of the signal power in serving links and underestimation of interference, which in consequence gives erroneous estimation of link budget and leads to unsatisfactory network design and deployment. To avoid inaccurate calculation of link budget while maintaining simplicity it is proposed to modify the simplified approach by using effective antenna patterns. On the other hand, effective antenna pattern can be further optimized by matching its half-power beam-width to the angular spread of the radio channel. It is demonstrated via simulations how to rework the radio link budget for accurate estimation of system performance in high bands for 5G and beyond, along with benefits of effective antenna pattern optimization.

An efficient system model to minimize signal interference and delay in mobile cloud environment

The integration of mobile computing with cloud computing has increased advantages to the users to access the applications from anywhere at any time. The traditional cellular system is overlaid by number of low power nodes which allows users to attain services at any time. But the increase of femto cells causes intra-tier, inter-tier interference and delay in the network. To overcome the bottleneck a sub-modular optimizing based offloading algorithm is proposed in this paper where the task is divided into two functions and processed. The main aim is to optimize execution time and interference. The simulation results show that the execution time has been reduced by 57.89% and performs well to obtain optimum solution compared to other existing methods.

Message Passing Based Distributed Learning for Joint Resource Allocation in Millimeter Wave Heterogeneous Networks

Millimeter wave (mmWave) provides an enormous spectrum for future broadband cellular communications. The corresponding challenging characteristics of radio propagation, and the use of highly directional transmission and the dense deployment, lead to more complex and critical resource allocation problems than in traditional cellular systems, where the channels are better tamed. In this paper, we study the joint power control and user association problem in heterogeneous networks (HetNets) by considering the dynamics of links as a Markov Decision Process (MDP). A reinforcement learning framework is proposed to study the problem. The large state/action space is handled by decomposing the large scale problem into multiple local problems, based on the topology of mmWave HetNet, which is motivated by the celebrated belief propagation (BP) algorithm in probabilistic graphical models. The decomposed problem is solved with a distributed message passing method and accelerated by the prior knowledge of the mmWave dynamics. Two categories of learning frameworks are proposed for time sensitive and power sensitive conditions. The real-world measurements in the 60GHz band are collected and used in the simulation of the proposed framework.

Device-to-Device (D2D) Communication as a Bootstrapping System in a Wireless Cellular Network

Device-to-Device (D2D) communication is considered to be a promising form of technology to distribute video contents to nearby users and devices at a high data rate and with few delays. In this paper, we propose utilizing the D2D services and cache of mobile devices as a bootstrapping system in a cellular network. The main objective of a bootstrapping-D2D (BD2D) system is to improve the quality of service in terms of achieving the minimum startup-time of popular video files in a cellular network. To achieve our objective, we propose a new caching concept for D2D communication in which each mobile device can cache and share the initial video portion or initial segments of the popular video files to other proximate users via a D2D communication link. We formulate an optimization problem that maximizes the cache-hit ratio of initial segments of the most popular video contents. The basic aim is to move the initial segments as close as possible to the wireless users. We also propose a network-assisted D2D architecture called mobile content delivery network-assisted-BD2D and algorithms that assist the BD2D system in the discovery of devices that have cached the initial segments of the requested video files, in cache placement decisions, and also in the registration of potential D2D devices at the core network. We evaluate the performance of the BD2D system and propose algorithms through extensive simulations under real wireless network conditions, such as interference, fading, and shadowing. Our concluding simulation results demonstrate that bootstrapping the initial segments using the short range BD2D system can significantly reduce the average startup-time of video files in comparison with bootstrapping the initial segments from the traditional cellular system.

A Review in the Core Technologies of 5G: Device-to-Device Communication, Multi-Access Edge Computing and Network Function Virtualization

5G is a new generation of mobile networking that aims to achieve unparalleled speed and performance. To accomplish this, three technologies, Device-to-Device communication (D2D), multi-access edge computing (MEC) and network function virtualization (NFV) with ClickOS, have been a significant part of 5G, and this paper mainly discusses them. D2D enables direct communication between devices without the relay of base station. In 5G, a two-tier cellular network composed of traditional cellular network system and D2D is an efficient method for realizing high-speed communication. MEC unloads work from end devices and clouds platforms to widespread nodes, and connects the nodes together with outside devices and third-party providers, in order to diminish the overloading effect on any device caused by enormous applications and improve users’ quality of experience (QoE). There is also a NFV method in order to fulfill the 5G requirements. In this part, an optimized virtual machine for middle-boxes named ClickOS is introduced, and it is evaluated in several aspects. Some middle boxes are being implemented in the ClickOS and proved to have outstanding performances.

Downlink and Uplink Decoupling in Heterogeneous Networks for 5G and Beyond

To meet the explosively increased data traffic demand from 5G and beyond, one of the most promising technologies is densified heterogeneous networks (HetNets). In HetNets, base stations (BSs) are brought closer and closer to users by densifying small BSs, which results in considerable high spectral efficiency and energy efficiency for cellular systems. However, HetNet topology challenges the traditional cellular systems. One of the most important challenges is user association. Aiming to avoid the drawback brought by coupled access (CA) in user association of HetNets, a decoupled access (DA) approach has emerged recently. By allowing access points in uplink (UL) and downlink (DL) association to be different, DA significantly improves UL performance of HetNets. This article focuses on recent works in DA. First, typical scenarios of HetNets for DA are described, which is followed by presenting two major decoupled association policies under typical scenarios. Then, DA shows its superiority over CA under different scenarios and decoupled association policies via various performance metrics. Finally, future work on DA in HetNets is discussed.

LTE on License-Exempt Spectrum

The radio frequency spectrum is classified as licensed and license-exempt/unlicensed spectrum. A traditional cellular communications system (e.g., LTE) operates unexceptionally on licensed spectrum. This paper explains the concept of cellular communications on both licensed and license-exempt carriers under a unified cellular architecture. It addresses the key challenges and describes a baseline communication framework that enables such operation, including carrier sensing based on listen-before-talk, discontinuous transmissions with limited channel occupation time, synchronization between licensed and license-exempt carriers, and coexistence with other incumbent systems like WiFi. These concept and techniques are further exemplified by a practical system, the LTE license-assisted access, including the downlink featured in Release 13 LTE and the most recent addition of uplink in Release 14 LTE.

Implicit vs. Explicit Approximate Matrix Inversion for Wideband Massive MU-MIMO Data Detection

Massive multi-user (MU) MIMO wireless technology promises improved spectral efficiency compared to that of traditional cellular systems. While data-detection algorithms that rely on linear equalization achieve near-optimal error-rate performance for massive MU-MIMO systems, they require the solution to large linear systems at high throughput and low latency, which results in excessively high receiver complexity. In this paper, we investigate a variety of exact and approximate equalization schemes that solve the system of linear equations either explicitly (requiring the computation of a matrix inverse) or implicitly (by directly computing the solution vector). We analyze the associated performance/complexity trade-offs, and we show that for small base-station (BS)-to-user-antenna ratios, exact and implicit data detection using the Cholesky decomposition achieves near-optimal performance at low complexity. In contrast, implicit data detection using approximate equalization methods results in the best trade-off for large BS-to-user-antenna ratios. By combining the advantages of exact, approximate, implicit, and explicit matrix inversion, we develop a new frequency-adaptive e qualizer (FADE), which outperforms existing data-detection methods in terms of performance and complexity for wideband massive MU-MIMO systems.

Overload control of massive random access for machine-type communications

We show that random access retransmissions can lead to performance degradation.A Markov model is proposed to evaluate the performance of LTE random access.There is an optimal number of retransmissions for massive random access.Random access resources are separated into two subsets for MTC overload control.Conventional and proposed schemes can be used adaptively depending on traffic load. Traditional cellular systems may not be appropriate to support machine-type communications (MTC) due to a large number of devices and relatively small, infrequent data transmissions. The 3GPP has identified the MTC as an important area of the LTE system and has discussed several mechanisms that control random access (RA) overload caused by massive MTC devices. In this paper, we show that a retransmission mechanism of RA may lead to performance degradation in an overload situation, and propose two RA solutions that relieve the RA overload. Since the RA success probability is closely related with the number of simultaneous RA attempts, the first solution adjusts the maximum number of RA retransmissions to control the amount of RA attempts. The second solution separates the RA resources into two subsets that MTC devices can access according to the number of consecutive RA failures and distributes the RA traffic over the two subsets. The two proposed solutions are analyzed by a mathematical model assuming a simplified operation, and a more realistic environment is considered by protocol-level simulations. Since the performance of the proposed solutions depends on the system configurations and parameters, the base station may adaptively adjust them for an optimal operation.

Hierarchical Group Based Mutual Authentication and Key Agreement for Machine Type Communication in LTE and Future 5G Networks

In view of the exponential growth in the volume of wireless data communication among heterogeneous devices ranging from smart phones to tiny sensors across a wide range of applications, 3GPP LTE-A has standardized Machine Type Communication (MTC) which allows communication between entities without any human intervention. The future 5G cellular networks also envisage massive deployment of MTC Devices (MTCDs) which will increase the total number of connected devices hundredfold. This poses a huge challenge to the traditional cellular system processes, especially the traditional Mutual Authentication and Key Agreement (AKA) mechanism currently used in LTE systems, as the signaling load caused by the increasingly large number of devices may have an adverse effect on the regular Human to Human (H2H) traffic. A solution in the literature has been the use of group based architecture which, while addressing the authentication traffic, has their share of issues. This paper introduces Hierarchical Group based Mutual Authentication and Key Agreement (HGMAKA) protocol to address those issues and also enables the small cell heterogeneous architecture in line with 5G networks to support MTC services. The aggregate Message Authentication Code based approach has been shown to be lightweight and significantly efficient in terms of resource usage compared to the existing protocols, while being robust to authentication message failures, and scalable to heterogeneous network architectures.

Cellular communications on license-exempt spectrum

A traditional cellular system (e.g., LTE) operates only on licensed spectrum. This article describes the concept of cellular communications on both licensed and license-exempt/unlicensed spectrum under a unified architecture. The purpose of extending a cellular system into the bandwidth-rich license-exempt spectrum is to form a larger cellular network for both spectrum types. This would result in an ultimate mobile converged cellular network. This article examines the benefits of this concept and the technical challenges, and provides a conceptual LTE-based design example that demonstrates how a traditional cellular system like LTE can adapt itself to a different spectrum type, conform to the regulatory requirements, and harmoniously coexist with the incumbent systems such as WiFi. In order to cope with the interference and regulatory rules on license-exempt spectrum, a special medium access mechanism is introduced into the existing LTE transmission frame structure to exploit the full benefits of coordinated and managed cellular architecture.

FISH: Finite Projective Plane Based Interference Cancellation for Slotted ALOHA

Due to the large number of light weight, low power devices in the future Internet, an efficient distributed multiple access protocol that can support a small fixed number of machines with continuous traffic along with a large variable number of devices with sporadic traffic is needed. The traffic in the future Internet has fundamentally different requirements: first, the accessing devices are of low power, which limit the transmission range; secondly, the delay is very stringent; thirdly, the number of active devices is time varying. In this paper, we propose a finite projective plane (FPP) based multiple access protocol (FISH) to meet such requirements. A low power node can transmit the replicas of a data packet in multiple time slots to achieve the same range of transmission as a high power node at one time. The initialization time slot of a frame allows for the estimation of the number of active nodes and the adjustment of the size of the frame to maximize the throughput. The interference cancellation and conflict resolution scheme of the FISH protocol is based on the theory of FPP. By using the property that the union of the sets of the FPP sharing one common point is a complete set, we are able to extract each of the individual user signals. One distinguishing feature of the FISH protocol is the amplification of the signal-to-noise ratio (SNR), which can either extend the transmission range or improve the bit error rate without sacrificing the throughput. In the performance evaluation, we demonstrate that the throughput is identical to the Slotted Aloha, while the SNR is magnified m times, where m is the order of the FPP. The proposed FISH protocol is of great use in the machine-to-machine communications as well as traditional cellular and satellite systems.

Incorporating D2D to Current Cellular Communication System

A device-to-device (D2D) group works as relay nodes to aid the information delivery from a source to a destination in cellular communication network. Within this system, we propose a communication mechanism to aid traditional cellular communication and correspondingly borrow some channel resource from traditional cellular communication system for D2D communication. On one side, to aid cellular communication, we propose a modified Alamouti scheme which does not modify the operation at the base station. This makes our proposed scheme consistent with previous cellular communication system. On the other side, there are many competitive D2D groups that want to potentially utilize the borrowed channel resource from traditional cellular system for delivering their own information. We model this competition as a game and utilize game theory technique to solve this competition problem.

Empirical models of the communications performance of Multi-hop Cellular Networks using D2D

Multi-hop Cellular Networks (MCNs) can improve the quality of service, capacity and energy-efficiency of traditional infrastructure-centric single-hop cellular systems. MCN systems can exploit Device-to-Device (D2D) communications and utilize the communications and computing capabilities of mobile devices. However, the communications challenges resulting from the use of mobile devices and D2D communications require empirical solid evidences of their performance benefits, and the design of robust communications and networking protocols. In this context, this paper presents a unique set of empirical models of the communications performance of MCN systems that utilize D2D communications. The models take into account the impact of the distance, propagation/visibility conditions, number of hops, and communication settings. The set of derived models can help design, test and optimize communications and networking protocols for MCNs that utilize D2D communications.

Proximity discovery for device-to-device communications over a cellular network

This article first reviews the proximity discovery techniques used in most device-to-device communication systems. The associated issues when applied to a cellular network and the potential solutions are then addressed. We propose a unified discovery design for full, partial, and off-network coverage scenarios. We discuss the advantages and disadvantages of packet and signature-based discovery schemes. We present a signature-based discovery design as a conceptual example for cellular applications. Through this example, we demonstrate that a cellular network can benefit from the information provided by the device discovery that a traditional cellular system lacks so that resources, interference, and connection selection can be more efficiently managed under a unified cellular network centric architecture.

A New Scheme for Network Selection in Heterogeneous Wireless Network using Fuzzy Logic

ABSTRACT Ensuring seamless and reliable switching across different constituent technologies is the basic requirement of heterogeneous wireless networks. IEEE 802.21 standard is recommended for 4G networks for coordinating among different mobile network for better services. Still, there exists a scope of further improving its performance by introducing the fuzzy logic concepts in it. The present work aims in this direction where a fuzzy interface system is designed using four different parameters viz. speed of mobile terminal, available bandwidth, received signal strength and number of users. The simulation result show that the number of vertical handoffs in the proposed technique reduced by 27% as compared to the existing fuzzy approach and by 42% as compared to the classical approach. Keywords Heterogeneous networks, seamless mobility, fuzzy logic, handoff. 1. INTRODUCTION The heterogeneous wireless network is a collection of different wireless technologies like cellular networks, wireless metropolitan area network (WiMax) and wireless local area network (WiFi). Besides traditional handoff (between cells of same technology), a vertical handoff (between cells of different technology) is the primary requirement for the proper functioning of heterogeneous networks. The most desiring features are to maintain best quality of service (QOS) by connecting to most fascinating network among the available networks. Figure 1 shows the integrated network structure of cellular networks, Wi-Fi and WiMax. In WiFi or WiMax the point of attachment through which a user gets connected is called an access point and in cellular network is termed as base station. The three basic steps in the vertical handover process are network discovery, handover decision and handover execution process [1]. In the traditional cellular system also known as GSM, the threshold comparison of different specific parameter metrics is used to make handover decisions [2]. The inter-system handovers are not only supposed to maintain ongoing connections but also to provide users with better services and to meet their individual requirements. In contrast to horizontal handover, vertical handover considers not only the received signal strength (RSS) but also the service class Mapping between handoff-in and handoff-out networks [3].The IEEE 802.21 standard defines the basic requirement for heterogeneous mobility. Quality of service is measured with the performance of transmission of data, network technologies and service accuracy [4]. The idea is to provide good connectivity with different network, reduction in call dropping and good quality of service. A cell phone call may be interrupted or drop after an unnecessary handover or incorrect handover. An unnecessary handover decision can degrade the quality of service and can also interrupt the ongoing communication. So it is essential that the handover process execute seamlessly and accurately to improve the quality of service. The multimedia applications like video streaming, VOIP, web browsing requires good quality of service. Therefore it is mandatory to indicate the quality of a vertical handover network selection and the network performance. In the vertical handover quality can be define as reduction in ping-pong effect, reduction in interruption in the ongoing call during handover and enhancing the throughput of the system [5].The scheme presented in this work shows better performance in this regard.

Experimental evaluation of multihop cellular networks using mobile relays [Accepted From Open Call

Future wireless networks are expected to provide high bandwidth multimedia services in extended areas with homogeneous Quality of Service (QoS) levels. Conventional cellular architectures might not be able to satisfy these requirements due to the effect of surrounding obstacles and the signal attenuation with distance, in particular under Non Line of Sight (NLOS) propagation conditions. Recent studies have investigated the potential of Multi-hop Cellular Networks (MCNs) to overcome the traditional cellular architecture limitations through the integration of cellular and ad-hoc networking technologies. However, these studies are generally analytical or simulation-based. On the other hand, this paper reports the first experimental field tests that validate and quantify the benefits that MCNs using mobile relays can provide over traditional cellular systems.