Performance Of Mobile Communication Systems Research Articles

Analysis of Carrier Aggregation as a Diversity Technique for Improved Spectral Efficiency and Secrecy Performance in Mobile Communications

Carrier aggregation (CA) was introduced in mobile communication systems in response to the demand for higher network capacity. CA was conceived as a technique to achieve higher data rates by aggregating multiple blocks of spectrum from the same or different frequency bands. This work explores a different point of view, where CA is employed not as a way to increase capacity through using more bandwidth, but as a diversity technique in order to increase the spectral efficiency of the existing spectrum, and therefore, achieve higher capacity without needing additional spectrum. A mathematical model and set of closed-form expressions are provided, which can be used to characterise the performance of CA as a diversity technique (in terms of both ergodic capacity and secrecy capacity) and determine the impact of various relevant configuration parameters. The numerical results obtained by evaluating the mathematical expressions derived in this work are in line with our previous simulation studies and demonstrate that CA can be effectively exploited as a diversity technique to improve the capacity and performance of mobile communication systems compared to the case of single-carrier transmission over the same amount of bandwidth.

A novel approach to efficient resource allocation in load-balanced cellular networks using hierarchical DRL

5G wireless networks require highly spectral-efficient multiple access techniques, which play an important role in determining the performance of mobile communication systems. Multiple access techniques can be classified into orthogonal and nonorthogonal based on the way the resources are allocated to the users. This paper investigates the joint user association and resource allocation problem in an uplink multicast NOMA system to maximize the power efficiency with guaranteeing the quality-of-experience of all subscribers. We also introduce an adaptive load balancing approach that aspires to obtain “almost optimal” fairness among servers from the quality of service (QoS) perspective in which learning automata (LA) has been used to find the optimal solution for this dynamic problem. This approach contains a sophisticated learning automata which consists of time-separation and the “artificial” ergodic paradigms. Different from conventional model-based resource allocation methods, this paper suggested a hierarchical reinforcement learning based frameworks to solve this non-convex and dynamic power optimization problem, referred to as hierarchical deep learning-based resource allocation framework. The entire resource allocation policies of this framework are adjusted by updating the weights of their neural networks according to feedback of the system. The presented learning automata find the $$\epsilon$$ -optimal solution for the problem by resorting to a two-time scale-based SLA paradigm. Numerical results show that the suggested hierarchical resource allocation framework in combination with the load balancing approach, can significantly improve the energy efficiency of the whole NOMA system compared with other approaches.

Novel cost-effective passive intermodulation measurement technique using a single power amplifier

The growing number of cellular devices and the introduction of high-speed data affect the network performance of mobile communication systems. Evaluation of passive intermodulation (PIM) phenomenon in the field of microwaves and mobile communications improve system performance. Typically, the PIM of the device-under-test (DUT) is measured using a set-up that involves two power amplifiers (PA), making it an expensive measurement set-up. This research aims to make PIM measurements cost-effective by using a single PA. Reflected (RFL) PIM distortion measured for two different DUTs, i.e., circulator and a microstrip (MS) line containing radio frequency interference (RFI) shielding gasket, using the presented and standard techniques. The presented PIM analyzer has a residue PIM of -104.5dBm. Comparison and error analysis suggested that the presented single PA method is feasible for DUTs having PIM between -60 and -94.5dBm at 43dBm input power. The residual PIM of the presented analyzer is high compared to the standard PIM analyzers; it is investigated that IM generated by the PA is the leading cause of this higher residual PIM product (RPIM). The proposed method will reduce overall system cost and size; it will also improve the battery efficiency of portable and desktop PIM analyzers.

Performance Evaluation of Key Performance of 5G Mobile Communication System And Development Countermeasures

This paper mainly studies the key performance of 5G mobile communication system and its development countermeasures. This paper introduces the challenges faced by 5G mobile communication system, which mainly come from increasing mobile data volume, connecting mass terminals anytime and anywhere, shortage of spectrum resources, and green environmental protection and energy efficiency; In order to study the key performance of 5G mobile communication system more comprehensively, first, this paper analyzes the practical significance of establishing the key performance indexes system of mobile communication system. Second, the performance requirements of mobile communication systems in six main application scenes are discussed. Third, the key performance indexes system of mobile communication system is constructed; This paper introduces the purpose and steps of performance evaluation of key performance of mobile communication system, and compares and evaluates the key performance of 5G and 4G in wide-area continuous coverage scene based on AHP. Suggestions on the development of 5G mobile communication system are put forward from four aspects: policy and system, demand and service, technology and talents, and sustainable development.

Performance evaluation of mobile communication system with reliability measures

Purpose – The purpose of this paper is to evaluate performance of mobile communication system with reliability measures. Design/methodology/approach – The mobile communication system consists of a mobile station (MS), base transceiver station (BTS), base station controller (BSC) and the mobile switching center. The MS is connected to BTS, BTS is connected to BSC and BSC is connected with the mobile switching system. With the help of these stations working, the authors have developed a mathematical model using Markovian approach. Findings – Using the supplementary variable technique, the Laplace transformations and Markov process theory, the reliability indices of the mobile communication system are determined. Originality/value – In the present work, the authors have developed a mathematical model based on a mobile communication system.

Development of a MATLAB Toolbox for Mobile Radio Channel Simulators

A profound knowledge of mobile radio channels is required for the development, evaluation, and also assessment at practical conditions of present and future mobile radio communication systems. The modelling, analysis, and simulation of mobile radio channels are important key area in current context. In addition to that, knowledge of channel behaviour in mobile radio communication is extensively recommended for the study of transmitter/receiver performances under different propagation scenarios. Our intention in this research work was to develop various kinds of mobile fading channel simulators using MATLAB and embed them into MATLAB software as a toolbox. Implemented channel simulators were combined MATLAB as a toolbox which users can easily select well-known channel models to test and to study the performance of mobile communication systems. It gives better support for the new users to work on the developed channel simulators, run the test procedures as well as parameter computation. The toolbox contains channel simulators for simulating non-stationary land mobile satellite channel, spatial shadowing processes, MIMO channels, multiple uncorrelated Rayleigh fading channels, mobile to mobile channel, frequency hopping channels etc. Set of test procedures were developed such as the autocorrelation function ACF, average duration of fades ADF, the probability density function PDF, and the level-crossing rate LCR etc., in order to test and to confirm the correctness of the implemented channel simulators. Proposed new algorithms to compute the model parameters of the channel simulators were also implemented in the toolbox to enable the parameterization of the channel simulators under specific propagation conditions. Some of the simulation models were implemented based on specification of GSM system by CEPT-COST 207. DOI: http://dx.doi.org/10.4038/jur.v2i1-2.7853 J. Univ. Ruhuna 2014 2:40-45

Performance Evaluation of Coordinated Multi-Point Transmission and Reception in Indoor Mobile Communication Systems

Recently, mobile communication systems are suffering from exponentially increasing data traffic. As a promising solution to the increase in data traffic, a coordinated multi-point transmission and reception (CoMP) scheme has been proposed. Although a great deal of research has been done on this new technology, the performance of mobile communication systems with CoMP has not been evaluated properly in a typical indoor environment. To address this, we have developed a system-level simulator and evaluated the performance of mobile communication systems with CoMP. Unlike previous works, we have used an actual antenna pattern in our simulator and link-level results are properly taken into account through link-level abstraction. By using a system-level simulator, we have evaluated the performance of mobile communication systems with CoMP in an indoor environment and found that unlike an outdoor cellular environment, CoMP may not improve the performance of overall mobile communication systems in an indoor environment.

Average SER Performance of Distributed Antenna Systems Over Shadowed Generalized-Gamma Channels for Different Modulation Schemes

Recently, much attention has been drawn to distributed antenna systems (DAS), which are proposed to improve the performance of mobile communication systems. This paper focuses on the analysis of the average symbol error rate (SER) of DAS over a generic composite channel. Initially, a new composite channel model is considered for DAS, which is a mixture of path loss, lognormal shadowing and generalized-Gamma fast fading. This composite channel model is a generic model, which includes many well-known composite channel models as special cases. Based on the channel model, the cumulative distribution function of the output signal-to-noise ratio is obtained by employing selective transmission scheme. Moreover, by averaging the channel conditions and the positions of the MS in the cell, an approximate expression of the average SER is derived, which is a unified form of expression for many commonly used modulation schemes. Numerical results show that the derived expression of the average SER can provide sufficient precision for evaluating the SER performance of DAS under different modulation schemes.

Simulation Performance of CDMA/QA in Mobile Channel

The aim of this work is to study, analyze and evaluate software the link performance of mobile communication system under the impairment of the multiple access schemes, down-link thermal noise and the multipath fading in the mobile channel. For this purpose, modeling and simulation has been used to study the effects of nonlinearities in mobile channel using spread spectrum for Direct Sequence Code Division Multiple Access, with Quadrature Amplitude Modulation (DS-CDMA/QAM).

Design and Simulation of Measurement-Based Correlation Models for Shadow Fading

This paper deals with the design of measurement-based correlation models for shadow fading. Based on the correlation model, we design a simulation model using the sum-of-sinusoids (SOS) method to enable the simulation of spatial lognormal processes characterizing real-world shadow fading scenarios. The model parameters of the simulation model are computed by applying the Lp-norm method (LPNM). This method facilitates an excellent fitting of the simulation model’s autocorrelation function (ACF) to that of measured channels. Our study includes an evaluation of all important statistical quantities of the proposed measurement-based simulation model, such as the probability density function (PDF), spatial ACF, decorrelation and coherence distance, as well as the level-crossing rate (LCR) and the average duration of fades (ADF). A comparison with the Gudmundson correlation model shows that the developed measurement-based correlation model outperforms the former one by far in terms of the goodness of fit to the measured data. The proposed measurement-based simulation model allows to study the effects of long-term fading on the performance of mobile communication systems under real-world shadow fading conditions.

기존의 2-Tx Radio Unit 을 재활용한 4-Tx 빔포밍 Radio Unit 구현 방법

To improve the performance of mobile communication systems, beamforming technology is being considered. However, the number of antenna should be more than four to implement beamforming technology. Therefore, the existing 2-Tx RU (radio unit) for MIMO (multiple input multiple output) should be replaced by 4-Tx RU for beamforming function. In this paper, we propose a new method to implement 4-Tx beamforming RU reusing the existing 2-Tx RU. We think that our method is very useful from the viewpoint of cost and environment because the existing 2-Tx RUs can be reused.

A New RF-path Calibration Method for BSs with Repeaters

To increase the performance of mobile communication systems, base statations having beamforming function are released recently. For the proper beamforming function, it is required that each RF paths be calibrated periodically. However, the current calibration method has a problem when the base station is connected to a repeater. In this paper, we report the problem and propose a new calibration method to solve the problem.

셀 내 간섭원에 의한 수신기의 신호 대 간섭비 분포 특성

To analyze the performance of mobile communication systems, the exact information of the carrier-to-interference ratio is important. Under the presence of an interferer in a cell, the carrier-to-interference ratio of the receiver is determined by the ratio between the informer-receiver distance and the receiver-interferer distance. In this paper, we derive the carrier-to-interference distribution based on values using the geometric relation among the informer, interferer and receiver, and confirm its exactness using the simulation result. We also apply the derivation result to a system with the adjacent channel interference, and analyze the outage probability.

Diversidade em Modulação Aplicada a Canais de Comunicações Móveis

The performance of mobile communications systems can be significantly improved by using the modulation diversity technique which is, basically, based on the combination of a suitable choice of the reference angle of an MPSK constellation with independent interleaving of the symbols components. This technique presents good performance assuming the absence of estimation errors for channels characterized by the flat fading. In this article, the performance of that recent technique is analyzed taking into account the effects of channel estimation errors. It is shown, by simulation, that the efficiency of this technique is maintained even under this assumption. Additionally, the impact of the Doppler effect on the system performance is treated and a trade-off between the interleaving depth used and the error probability is achieved.

Application of a Recurrent Neural Network to Space Deversity in SDMA and CDMA Mobile Communication Systems

Linear and non-linear adaptive algorithms are investigated for Space Division Multiple Access (SDMA). SDMA is one of the emerging techniques for multiple access of users in mobile radio, which uses spatial distribution of users for their differentiation. The performance of the linear Square Root Kalman (SRK) algorithm for SDMA is compared to that of the non-linear Recurrent Neural Network (RNN) technique. The proposed SDMA-RNN technique is evaluated over Rician fading channels, and it shows improved Bit Error Rate (BER) performance in comparison with the linear SRK-based technique. The performance of SDMA-RNN is also compared with that of Code Division Multiple Access (CDMA) systems, showing that it could be used as a viable alternative scheme for multiple access of users. Finally, a Hybrid CDMA-SDMA system is proposed combining CDMA and SDMA-RNN systems. Hybrid CDMA-SDMA exhibits a very good potential for increase in the capacity and the performance of mobile communications systems.

On the performance of HTS microstrip quasi-elliptic function filters for mobile communications application

The low-loss and high-selective high-temperature superconducting (HTS) bandpass filters can enhance performance of mobile communications systems. In this paper, we summarize a recent progress of novel HTS preselect bandpass filters that have been developed for a European research project. The objective of the project is to construct an HTS-based transceiver for mast-mounted DCS1800 base stations. The HTS preselect receive filters have been designed to have a quasi-elliptic function response in order to provide low insertion loss and very steep rolloff at the filter band edges. The filters cover a 15-MHz sub-band of a receive band, which ranges from 1710 to 1785 MHz. The filters have been fabricated using double-sided YBCO thin films on 03-mm-thick MgO or 0.5-mm-thick LAO substrates. The latest experimental results of the filters, including those encapsulated with a low-noise amplifier in an RF module are presented, showing very promising performance. The issues associated with asymmetric frequency response are investigated to improve the filter performance.

Application of antenna arrays to mobile communications. II. Beam-forming and direction-of-arrival considerations

Array processing involves manipulation of signals induced on various antenna elements. Its capabilities of steering nulls to reduce cochannel interferences and pointing independent beams toward various mobiles, as well as its ability to provide estimates of directions of radiating sources, make it attractive to a mobile communications system designer. Array processing is expected to play an important role in fulfilling the increased demands of various mobile communications services. Part I of this paper showed how an array could be utilized in different configurations to improve the performance of mobile communications systems, with references to various studies where feasibility of apt array system for mobile communications is considered. This paper provides a comprehensive and detailed treatment of different beam-forming schemes, adaptive algorithms to adjust the required weighting on antennas, direction-of-arrival estimation methods-including their performance comparison-and effects of errors on the performance of an array system, as well as schemes to alleviate them. This paper brings together almost all aspects of array signal processing.