Mobile Communication Services Research Articles

대역확산 기법을 사용한 단일 채널 중계기 개발

This paper describes the elimination of feedback signals to implement a stable on-channel repeater regardless of input signals in the frequency bandwidth desired by the user. Toward this objective, the spread spectrum technique is applied to an adaptive filter, in which the least mean square algorithm removes the frequency characteristics of input signals. OCRs have been commercialized using adaptive filters based on the LMS algorithm in existing mobile communication services, including in GSM, CDMA, WCDMA, and LTE. However, in current mobile communication networks, various services with different signal characteristics can become mixed in the user’s frequency band, and bands with no signals may also exist. If the integrated bandwidth and the occupied bandwidth do not coincide, a bandpass filter cannot completely suppress other bands. Because the LMS algorithm is affected by the frequency characteristics of input signals as well as the feedback path of the object to be removed, feedback signals cannot be canceled for the entire band. Therefore, in this paper, the SS technique is applied to the existing LMS method to remove the frequency characteristics of input signals, thereby eliminating feedback signals in a more stable manner. The performance of the proposed scheme is verified through simulation and experiments.

Research on Smart Antenna System Based on Beamforming Algorithm

As the most important element of mobile communication, antenna is the component that radiates and receives electromagnetic waves.The performance of the antenna plays a very important role in the overall performance of mobile communications.Due to the increase in user demand, mobile communication systems are increasingly demanding antennas.In this paper, the composition and principle of the smart antenna system are analyzed. The smart antenna system is composed of an antenna array, a group of beam forming networks and algorithms. Compared with the antenna of the traditional antenna, it has no interference between signals and reduces. The characteristics of external interference and noise, and improved signal coverage, the research results show that smart antenna technology will provide the best service for future mobile communications.

Miniaturized PIFA for 5G Communication Networks

This paper designed a miniaturized Planar Inverted-F Antenna for 5G communication networks, including Long-Term Evolution Advanced mobile communication services. By showing the radiation pattern, voltage standing wave ratio, and antenna gain of the designed Planar Inverted-F Antenna, this paper evaluates its performance. To show the key characteristics of the Planar Inverted-F Antenna, this paper modeled and simulated it with various variances. Moreover, the real Planar Inverted-F Antenna was fabricated and measurements were done to validate the simulated characteristics of the internal antenna.

Forecasting the video data traffic of 5 G services in south korea

Along with the rapid evolution of mobile communication services, popularization of smartphones, and increase in traffic service usage, data traffic has also grown rapidly. Anticipating massive data traffic growth owing to the launch of the fifth-generation (5 G) mobile communication service in 2019, this study analyzes and forecasts: 1) the number of 5 G users using a logistic model, 2) consumer preference for 5 G services using a mixed logit model, and 3) 5 G data traffic increase using sensitivity analysis. The results indicate that data traffic would rapidly increase for 5 G services: the number of 5 G users is estimated to be 1.560 million by 2019, which will increase to 3.475 million by 2020 and 37.340 million by the end of 2025. Data traffic growth is predicted to reach 46 PB by the end of 2019, 129 PB by 2020, and 342 PB by 2021, after which it is projected to rapidly rise to 1,343 PB by 2022 and to 6,340 PB by 2025. The findings of this study provide a reference point for annual investment and marketing strategies of communication companies.

The impact of telecommunications regulation on less well-off Mexican households

Access to mobile communications in Mexico is heavily skewed in favour of those with higher incomes. In 2014, 80% of the highest 10 percent (decile) in the income distribution had access to mobile communications, while only 30% of the lowest decile did. The same figures for 2016 are 84% and 40%. This report sets out to review some of these numbers and places them within the narrative of asymmetric regulation and other reforms which Mexico adopted in 2013/14.Among our observations is that buyers of mobile communications services in the lowest decile in 2014 spent 6% of their income on that service while those in the highest decile spent only 2%. Over the next 2 years, mobile communications prices fell by 36%; this fall in the prices of mobile communications followed regulatory reforms in the sector which were introduced in 2013/4. An interesting component of these reforms was the imposition on the preponderant operator of asymmetric access charges, which reduced its mobile termination rates to zero. This means that a policy that, in principle, was not even aimed at, designed, or considered for the poor had a real strong impact on this group of the population.

System Design of Gigabit HAPS Mobile Communications

High-altitude platform stations (HAPSs) are expected to provide ultrawide-coverage areas and disaster-resilient networks from the stratosphere at around 20 km by installing wireless equipment on HAPS. Because their altitude is much lower than that of communications satellites, HAPSs can provide mobile communications services directly to smartphones, which are commonly used in terrestrial networks, such as fourth generation Long Term Evolution. Considering the widespread nature of mobile broadband communications and the importance as a backup line in case of disaster, HAPSs are expected to provide a large capacity in the future. A cellular system with single-cell frequency reuse using multiple cells similar to terrestrial mobile communications should be introduced to achieve such a capacity. The number of cells that a HAPS can accommodate ranges from 1 to more than 100, depending on unmanned aerial vehicle (UAV) ability. By contrast, the optimal cell configuration, which depends on the number of available cells, has not been clarified in previous research. In this paper, we propose an optimization method for the cell configuration for HAPS mobile communications using a genetic algorithm, which can be generally applied regardless of the number of cells and can clarify the optimal cell configuration. Although many cells are required to achieve gigabit-class HAPS mobile communications, the heightened power consumption due to the large number of cells is a critical problem for UAVs. Thus, we also investigate the reduction of the total transmission power and demonstrate the feasibility of energy-efficient gigabit HAPS mobile communications with wide coverage.

Telecom Spectrum Map of India

This paper aims at developing a spectrum map of the spectrum allocated for provisioning of mobile communications by Telecom Service Providers (TSPs) in India through various auctions from 2010 to 2016. The paper probably is the first initiative of its kind. It adopts a unique approach in translating the spectrum allocated over the years for mobile communication services in India into a visually comprehensible spectrum utilisation map(s). The map(s) provide(s) a visual state of the allocated spectrum which will be helpful for both policy formulators and the service providers in focussing their emphasis on both quality of spectrum allocated, and the quantum of spectrum allocated. It can also be used as a planning tool by all stake holders for subsequent spectrum auctions.

Green Base Station using WSN

Since the number of mobile users has been increased, there comes a number of new mobile operators. This accounts for the increased installation of towers. A critical mobile network consume 40-50MW (approx.) and a diesel generator consume 1MG (approx.) of diesel per day. Also a base station requires greater amount of power employed for its working in which some of its internal applications like light, coolant systems say air conditioning, fans etc., uses the major part of the power utilized. This intensifies the burning of coal which emits carbon dioxide into the atmosphere. At times the number of users for a base station may be very less especially during night time, consuming the power unnecessarily. Our approach is to reduce the intake of power by the base stations during unwanted time. This can be done by establishing communication between the adjacent towers to intimate the unused tower to remain idle or active based on the requirement. Also this approach conveys the measures taken to reduce the power consumed by the internal applications of the base station. The entire setup is under the surveillance of personal computer thereby creating an energy efficient mobile infrastructure with power saving, reduction of CO2 emission which in turn reduces global warming and successful operation of large scale mobile communication services.

Demand forecasting for the 5G service market considering consumer preference and purchase delay behavior

Unlike previous mobile communications technologies that centered on service subscribers, 5G mobile communication (5G) is expected to converge with various industry fields such as transportation, manufacturing, and construction, thereby stimulating innovation and generating significant ripple effects. At a time when 5G commercialization is incipient, it is necessary to understand mobile communication service users who are likely to be important initial users for the creation and diffusion of 5G services. The current study analyzed consumer preference for 5G services based on conjoint survey data and a mixed logit model, and we conducted a market simulation based on the estimation results to determine the impact of 5G technology development on the 5G market, specifically regarding the mobile communication fields. In addition, this study derived consumer purchase delay factors for 5G services using an ordered logit model. The results show that consumers delay the adoption of 5G services mainly because of the cost and lack of need. By considering the consumer purchase delay, it is estimated that the acceptance rate of 5G services by consumers will decrease by more than 50%; this is because it is hard to conclude a purchase delay of more than one year leads to an actual purchase. The results of this study suggest important strategic implications that are likely to reduce the purchase delay of consumers, improve the actual adoption rate, and increase the diffusion of 5G services.

Intra-Operator Customer Churn in Telecommunications: A Systematic Perspective

Customer churn as a common but extremely harmful phenomenon haunts service operators in telecommunications industry for a long time. Discriminating customers prone to churning in the early stage and taking precaution measures can mitigate customer churn effectively. Unlike previous works which mainly considered the inter-operator customer churn, we focus on a new problem of intra-operator customer churn, that is, customers abandon their fourth generation (4G) mobile communication services and switch to third generation/second generation (3G/2G). Due to quite different mechanisms and causes, previous studies cannot tackle this new problem well. In this paper, we propose a novel profit maximizing framework to solve this special customer churn problem. Specifically, we first build a profit maximizing classifier to predict whether a customer is prone to churn or not, in which profitable customers have more probability to be classified correctly. Then, we describe and quantify the switching behaviors of 4G customers by introducing a notion of switching score. Finally, we investigate relations between operators and customers, finding that some features of 4G service plans provided by operators indeed affect switching behaviors of 4G customers remarkably. This provides insight into reasonable design of 4G service plans for operators in the future. Our framework uncovers the root causes of intra-operator customer churn and solve the problem well. Experimental results based on real data demonstrate the effectiveness of our framework.

A two-stage structural equation modeling-neural network approach for understanding and predicting the determinants of m-government service adoption

Purpose Despite the widespread use of mobile government (m-government) services in developed countries, the adoption and acceptance of m-government services among citizens in developing countries is relatively low. The purpose of this study is to explore the most critical determinants of acceptance and use of m-government services in a developing country context. Design/methodology/approach The unified theory of acceptance and use of technology (UTAUT) extended with perceived mobility and mobile communication services (MCS) was used as the theoretical framework. Data was collected from 216 m-government users across Bangladesh and analyzed in two stages. First, structural equation modeling (SEM) was used to identify significant determinants affecting users' acceptance of m-government services. In the second stage, a neural network model was used to validate SEM results and determine the relative importance of the determinants of acceptance of m-government services. Findings The results show that facilitating conditions and performance expectancy are the two important precedents of behavioral intention to use m-government services, and performance expectancy mediates the relationship between MCS, mobility and the intention to use m-government services. Research limitations/implications Academically, this study extended and validated the underlying concept of UTAUT to capture the adoption behavior of individuals in a different cultural context. In particular, MCS might be the most critical antecedent towards mobile application studies. From a practical perspective, this study may provide valuable guidelines to government policymakers and system developers towards the development and effective implementation of m-government systems. Originality/value This study has contributed to the existing, but limited, literature on m-government service adoption in the context of a developing country. The predictive modeling approach is an innovative approach in the field of technology adoption.

Loss prediction model of a 850 MHz system using radio wave recommendations for terrestrial services

In the implementation of radiocommunication links necessary to determine the possible coverage areas for mobile communications services in urban environments, through modeling and statistical prediction by means of measurements of signal intensity in the field; therefore, it is necessary to have recent and updated mathematical models to predict the propagation losses considering the most appropriate correction parameters according to the working frequencies. The research focuses on establishing the losses obtained by means of power measurements according to the regulations of the International Telecommunications Union of a mobile radio system in the city of San José de Cúcuta, Colombia, in order to estimate the coverage and compare the performance of the model obtained with models similar.

150-W Power-Over-Fiber Using Double-Clad Fibers

This article presents simultaneous data and power transmission systems using a double-clad fiber (DCF). In future radio-over-fiber (RoF) networks, a large number of remote antenna units (RAUs) will be required to provide various kinds of mobile communication services. Power-over-fiber (PWoF), which delivers electrical power to drive the RAUs in optical fibers, is an attractive technique that offers cost-effective installation, operation, and maintenance of RAUs, and achieves the power savings across the entire RoF networks. In particular, the use of double-clad fibers (DCFs), which consist of a single-mode (SM) core and an inner cladding that surrounds the SM core, are useful for much higher power transmission than conventional PWoF techniques. Along the DCF link, optical data signals are transmitted into the SM core, whereas high-power feed light for optical powering is transmitted into the inner cladding, which has a core area that is approximately 240 times larger core area than that of conventional SM cores. In this article, we experimentally demonstrate a PWoF feed with up to 150-W of power using a 1-km DCF. To show the feasibility of the PWoF system, we investigate the bend performance and temperature characteristics of the DCF link. We also evaluate data and power transmission performance under the 150-W PWoF feed in the DCF link.

Developing enterprise competitive advantage as a component of anti-crisis management

The article describes the concept of enterprise anti-crisis management, an important component of which is the formation and development of competitive advantages. Due to various factors, enterprise competitive advantages can be internal, which are, being subject to change, completely controlled by management of enterprises, and external – the ones that enterprises cannot quickly deal with. The study analyses the current state of activity of the information and telecommunications enterprises in Ukraine, which results in the determined reasons for a slowdown in development of small and medium-sized telecommunication enterprises (SMEs). The list of services of telecommunication enterprises, amongst which mobile communication services are of the highest demand, is provided. The problems of Ukraine’s mobile communication market development are determined. It is emphasized that enterprises should constantly implement anti-crisis management, which implies the development of telecommunication enterprise competitive advantages. Using the multi-factor correlation-regression analysis, a model of the dependence of net profit on the main types of costs is constructed. Applying the model will enable telecommunication enterprises to predict change in the net profit depending on changes in labour costs and costs of social events, material costs, depreciation and other operating costs, which will contribute to the development of their competitive advantages. The study offers the anti-crisis management mechanism providing timely determination of availability, as well as expediency of development of a competitive advantage, for a telecommunication enterprise.

A Fast Hybrid Beamforming Scheme for High-Speed Railway Communications

With the increasingly demand for reliable mobile communication service in the high-speed railway (HSR) system, the service stability of HSR communication is of great concern in recent research. Focusing on ensuring the quality of services (QoS) and system throughput, massive multi-input multi-output (massive MIMO) and beamforming technologies have been widely applied. In this paper, aiming to minimize the communication outage probability (OP) and not to decrease spectrum efficiency (SE) too much, we propose a fast HBF (F-HBF) scheme for HSR communications. The proposed scheme uses a low-complexity beam-searching algorithm to trace high-speed trains in real time. The simulation results verify that the proposed scheme can significantly reduce OP without too much SE degradation.

Investigation into Customer Relation of Two Global Systems for Mobile Communication (GSM) Service Provider in Nigeria

The assessment of customer care response of TEL1 and TEL2 global systems for mobile communication (GSM) service providers in Nigeria was done. Data were obtained from the customer care Departments of these two mobile service providers in their head office in Lagos for six months period. The data assessment result shows that the four service types: prepaid/postpaid, premium/HNI, BB/3G-HIS, and call roaming had 445510, 328396, 45221, and 4127 number of calls respectively for TEL 1 and 416935, 357810, 41968, and 2106 respectively for TEL 2, with prepaid/postpaid having the highest values and call roaming service type had the least for both TEL 1 and TEL2. The number of calls answered followed the same trend for both TEL1 and TEL2.It was observed that about 96% of the calls offered by prepaid/postpaid customers, 95% of Premium/HNI, were answered for both TEL 1 and TEL 2. About 93% of calls offered by BB/3G-HIS, and 95% of call roaming customers were answered for TEL1, while it is 92% and 93% respectively for TEL2. It can be deducted that PREPAID/POSTPAID customers enjoy highest customer service care in both telecommunication networks. Higher values of AHT(S) of TEL 1 over TEL 2 imply that TEL 1 spends the more time with its subscribers when attending to a complaint.

Towards secure 5G networks: A Survey

To support various new use cases from vertical industries besides enhanced mobile broadband communication services, the 5G system aims to provide higher speed, lower latency, and massive connectivity to various devices by leveraging the evolution of 4G with the addition of new radio technology, service-based architecture, and cloud infrastructure. The introduction of new technologies, new use cases and people’s growing concerns regarding privacy issues brings new challenges to providing security and privacy protection for 5G. This paper makes an extensive review of the state of the art towards ensuring 5G security and privacy. By analyzing the lessons from the 4G security system, the requirements from new scenarios and models, the challenges resulting from new technology and paradigm, we identify typical security and privacy issues to be solved in 5G. Then, we discuss potential solutions from academia and industry to secure 5G networks from several perspectives, including the overall 5G security framework, core network, radio access network, cloud infrastructure, and the Internet of things. Finally, several key open issues and potential research directions are identified and discussed.

Surface Correlation-Based Fingerprinting Method Using LTE Signal for Localization in Urban Canyon.

The Global Satellite Navigation System (GNSS) used in various location-based services is accurate and stable in outdoor environments. However, it cannot be utilized in an indoor environment because of low signal availability and degradation of accuracy due to the multipath distortion of satellite signals in urban areas. On the contrary, LTE signals are available almost everywhere in urban areas and are quite stable without much variation throughout the year. This is because of the fixed location of base stations and the well-maintained policy of mobile communication service providers. Its varied stability and reliability make LTE signals a more viable method for localization. However, there are some complexities in utilizing LTE signals including signal interference distortion phenomena during propagation multipath fading, and various types of noise. In this paper, we propose a surface correlation-based fingerprinting method to utilize LTE signals for localization in urban areas. The surface correlation converts timely measured signal strength into spatial pattern using the walking distance from a Pedestrian Dead-Reckoning (PDR). The surface correlation is carried out by comparing the spatial signal strength pattern of a pedestrian`s movement trajectory with a fingerprinting database to estimate the location. A reference trajectory of the moving pedestrian is chosen to have a greater correlation among the multiple trajectory candidates generated from a link-based fingerprinting database. By comparing spatial signal strength patterns, the proposed method can improve robustness in localization overcoming the accuracy degradation problem due to RF multipath and noise that are dominant in the conventional RSS measurement-based LTE localization scheme. The test results in urban areas demonstrate that the proposed surface correlation-based fingerprinting method has improved performance compared to the other conventional methods, thus proving to be a useful complementary method to the GNSS in urban areas.

이동통신 이용자의 지각된 고객가치가 고객만족도 및 고객충성도에 미치는 영향: 고객자산가치 모형을 기반으로

Korean mobile communications service providers are switching their axis of competition towards the retention of their own customers. However, the theoretical framework and experience in the industry for customer relation management(CRM) which is necessary for customer retention is insufficient in this market. Considering these aspects, this study is to develop measurement items for CRM in mobile communication industry and to verify the causal relationship between items based on the framework of customer equity drives. 495 samples from online survey questionnaire were collected from smartphone users in terms of three types of customer value, satisfaction, and customer loyalty to the mobile service provider, and empirically tested using a structural equation modeling technique. The results show that the theoretical model of customer equity driver is also fitted into this industry and confirm the casual relationships between the constructs of the model. Customer value elements are antecedents of customer satisfaction and customer loyalty, customer satisfaction partially and fully mediate the impact of customer value elements on customer loyalty. However, differently from other industry such as airline or hotel industry, relationship value was revealed as the most important factor on satisfaction in mobile communication industry.

Propagation Model in Indoor and Outdoor for the LTE Communications

Rapidly rising demand for radio communication and the explosion in the number of mobile communications service subscribers have led to the need for optimization in the development of fifth-generation (5G) mobile communication systems. Previous studies on the development of propagation models considering a propagation environment in the existing microwave band have been mainly focused on analyzing the propagation characteristics with regard to large-scale factors such as path losses, delay propagation, and angle diffusions. In this paper, we investigated the concept of spatial and time changes ratios in the measurement of wave propagations and measured RSRP of Long Term Evolution (LTE) signals at three locations considering the time rate of 1% and 50%. We confirmed the concept of spatial and time changes rate based on the results of analyzing the signal data measured and proposed the propagation models 1 and 2 in microcell downtown. The forecast results using proposed models 1 and 2 were better than the COST231 model in both indoor and outdoor measured places. It was predicted between a time rate of 1% and 50% indoor within 400m and outdoor within 200m. In the future, we will study the propagation model of 5G mobile communication as well as the current 4G communication using artificial intelligence technology.