Cellular Wireless Communication Research Articles

Hybrid Digital and Analog Beamforming Design for Large-Scale Antenna Arrays

The potential of using of millimeter wave (mmWave) frequency for future wireless cellular communication systems has motivated the study of large-scale antenna arrays for achieving highly directional beamforming. However, the conventional fully digital beamforming methods which require one radio frequency (RF) chain per antenna element is not viable for large-scale antenna arrays due to the high cost and high power consumption of RF chain components in high frequencies. To address the challenge of this hardware limitation, this paper considers a hybrid beamforming architecture in which the overall beamformer consists of a low-dimensional digital beamformer followed by an RF beamformer implemented using analog phase shifters. Our aim is to show that such an architecture can approach the performance of a fully digital scheme with much fewer number of RF chains. Specifically, this paper establishes that if the number of RF chains is twice the total number of data streams, the hybrid beamforming structure can realize any fully digital beamformer exactly, regardless of the number of antenna elements. For cases with fewer number of RF chains, this paper further considers the hybrid beamforming design problem for both the transmission scenario of a point-to-point multipleinput multiple-output (MIMO) system and a downlink multiuser multiple-input single-output (MU-MISO) system. For each scenario, we propose a heuristic hybrid beamforming design that achieves a performance close to the performance of the fully digital beamforming baseline. Finally, the proposed algorithms are modified for the more practical setting in which only finite resolution phase shifters are available. Numerical simulations show that the proposed schemes are effective even when phase shifters with very low resolution are used.

Intercarrier Interference Analysis for High-Speed Trains Based on Broadband Channel Measurements

This letter presents an analysis of intercarrier interference (ICI) in high-speed trains. The ICI is caused by the motion of the receiver together with the carrier frequency offset (CFO). It results in a degradation of the reliability of the OFDM transmission. The analysis is based on a channel sounding measurement campaign for cellular broadband wireless communications with high-speed trains that was carried out in the context of the CORRIDOR project. The considered scenario corresponds to a railway deployed network, where the base station is located directly next to the railway line. We present the ICI power obtained with the measurement campaign and some theoretical results for a simple channel model that captures the main effects observed in the measurements.

A Sectored CoMP with Constrained Greedy Resource Allocation for OFDM Communication System

In this paper, a sectored Coordinated Multi-Point (CoMP) scheme with constrained greedy resource allocation method is proposed to avoid the inter-cell interference and has a fair service provision advantage for a wireless cellular communication system. The proposed sectored CoMP is evaluated at the long term evolution system and compared with the traditional inter-cell interference coordination (ICIC) methods, such as the partial frequency reuse and the soft frequency reuse. Results show that the proposed scheme has a better ICIC performance than the conventional methods. Besides, the proposed sectored CoMP with constrained greedy resource allocation also has better system frequency utilization and fair cell-edge user data service advantages compared with the well-known proportional fair scheduling.

Self-organization in disaster-resilient heterogeneous small cell networks

Heterogeneous small cell networks with overlay femtocells and macrocell is a promising solution for future heterogeneous wireless cellular communications. However, great resilience is needed in heterogeneous small cells in case of accidents, attacks and natural disasters. In this article, we first describe the network architecture of disaster resilient heterogeneous small cell networks (DRHSCNs), where several self-organization inspired approaches are applied. Based on the proposed resilient heterogeneous small cell network architecture, self-configuring (power, physical cell ID and neighbor cell list self-configuration) and self-optimizing (coverage and capacity optimization and mobility robustness optimization) techniques are investigated in the DRHSCN. Simulation results show that self-configuration and self-optimization can effectively improve the performance of the deployment and operation of the small cell networks in disaster scenarios.

Timeliness of Data Delivery from Q330 Systems

Research in rapid analysis of earthquake data, broadly classified as early warning (EW) or early alarm studies, has spurred interest in the capability of digital seismic data systems to provide low‐latency data. Because of the wide usage of Quanterra Q330 data systems in operational networks, published results analyzing the latency of deployed systems have considered these devices. Several years ago, studies (e.g., Allen, 2009; Brown et al. , 2011) showed that the effectiveness of EW systems was then limited by the total delay required to deliver waveform data for analysis of 4 s or more within instrumentation systems. Recent results (Kuyuk et al. , 2014), however, following the American Recovery and Reinvestment Act (ARRA)‐funded upgrade of instrumentation in California show that instrumentation‐related delays have been reduced in some operational networks to a comparatively small component, typically <10%, of the overall time required to issue EW alerts. We present a simple, robust method to measure the latency of data delivery arising in the Q330 family of data loggers, including the typical contribution to total latency of both hardwired and cellular wireless communication paths over the public internet. These latter two categories of communication represent the majority of those used in operational seismological networks. Current EW systems are capable of issuance of an alert within 8.68±3.73 s after the first P ‐wave detection for events in California (Kuyuk et al. , 2014). We show that the actual latency introduced by Q330 data loggers—including public internet latencies—is typically <1.5 s maximum, with a mean value <1 s, when communications network bandwidth is capable of sustaining continuous data delivery. The method is applicable to any data system. Measured values of data latency are consistent with in situ measurements in EW systems now operating in California. The sub‐1 s mean latency capability of Q330 systems now deployed widely in seismically active areas …

MIMO Reference Antennas Performance in Anisotropic Channel Environments

The new generation of cellular wireless communications, long term evolution (LTE), requires multiple antennas at both the transmit and receive ends of the radio link to improve system performance. This use of the radio link is termed multiple input-multiple output (MIMO), and in this work, the focus is on the downlink (base station transmit and mobile receive). Efforts to define over-the-air (OTA) downlink MIMO measurement methodologies are still being carried out within several standards bodies and are based on the evaluation of so-called good, nominal, and bad MIMO reference antennas. The reference antennas were necessarily defined independently of the channel environment, which is still under discussion. The reference antenna figures of merit, for an isotropic channel environment, were chosen as efficiency, branch power ratio (BPR), and correlation. The objective of this work is to evaluate the radiated performance of the MIMO reference antennas using anisotropic (nonuniform power angular spread) channel environments. The performance of the reference antennas in anisotropic environments is different to that in an isotropic environment, due to the antenna orientation in the three-dimensional space relative to the channel. This leads to a statistical description of the branch power ratio (BPR), correlation, and efficiency, which is expressed in terms of mean effective gain (MEG). The outcome of this new anisotropic evaluation is that the reference antennas are seen to vary significantly for BPR and mean effective gain (MEG) and somewhat less for correlation, relative to the isotropic environment.

English

English

Minimum Utilization of Electromagnetic (2G, 3G, 4G) Spectrum in Seamless Mobility Based on Various Estimation Methods

AbstractWireless Cellular Seamless Mobility is the most important feature of a wireless cellular communication system. Basically cell phones are used for communication purpose and therefore good cell coverage is needed to make and receive calls. Usually, continuous service is achieved by supporting handover from one cell to another. Handover is the process of changing the channel associated with the current connection while a call is in progress. It is often initiated either by crossing a cell boundary or by deterioration in quality of the signal in the current channel. Mobile IP, too, has to support redirection of data to a new foreign agent after the change of network access. In this case the additional delay caused by the redirection. The shorter the interruption of the service is -up to the ideal case of no service interruption. Minimizing the Delay based on some prior estimation methods in handover is better for quality of seamless connectivity anytime; anywhere across communication networks. All mobile phone system supports the seamless handover between base stations. To avoid the additional delay and wastage of Electromagnetic Spectrum, Mobile IP may use Optimizations such as rerouting of the whole packet in the flow of efficiently transmission of data with short interrupted service by Time series based Spectrum Estimation Technique. Due to the utilization of seamless handover mechanism it reduces the unwanted usage of Spectrum.

Performance Analysis of Blind Beamforming Algorithms in Adaptive Antenna Array in Rayleigh Fading Channel Model

In this paper, we analyze the performance of adaptive blind algorithms – i.e. Kaiser Constant Modulus Algorithm (KCMA), Hamming CMA (HAMCMA) – with CMA in a wireless cellular communication system using digital modulation technique. These blind algorithms are used in digital signal processor of adaptive antenna to make it smart and change weights of the antenna array system dynamically. The simulation results revealed that KCMA and HAMCMA provide minimum mean square error (MSE) with 1.247 dB and 1.077 dB antenna gain enhancement, 75% reduction in bit error rate (BER) respectively over that of CMA. Therefore, KCMA and HAMCMA algorithms give a cost effective solution for a communication system.

On the Diversity Order of a General Cooperative Relaying Communication System

Cooperative communication technology exploiting distributed spatial diversity is a promising solution for the future high data-rate cellular and ad-hoc wireless communications. To characterize the performance of a cooperative network, the cooperative diversity is commonly used. In this paper, we revisit the concept of diversity and look into the essence of cooperative diversity. We analyze the diversity performance of a general cooperative relaying system with multiple branches. Moreover, each branch consists of one or more hops. Unlike in other analyses, the assumptions that each node being only equipped with a single antenna and that all channel characteristics belonging to the same family are NOT required in our study. Using the decode-and-forward (DF) relaying protocol as an illustration, we provide analytical results on the diversity gain and the coding gain. The results also encompass most of the existing results as special cases. We further show the relationship between the diversity order of a branch and those of the constituent links; and the relationship between the diversity order of the network and those of the constituent branches. In particular, we show that for the uncoded DF protocol, the full diversity order can be achieved by using simple hard-decision detection at the destination. The requirement is to set appropriate signal-to-noise-ratio (SNR) thresholds for the multi-hop branches. To improve the bandwidth efficiency, we also randomly select one branch, among those branches satisfying the SNR-threshold requirement, for the transmission. We show that such a scheme accomplishes the full diversity order and produces a good error performance.

Impact of Sectorization/Vehicular Traffic on Minimum Cell Size for Information Capacity Increase in Cellular Systems

In this paper results of mathematical analysis sup-ported by simulation are used to study the impact of sectorization/vehicular traffic on the theoretical limit for cell size radius reduction in cellular wireless communication systems. Information capacity approach is used for the analysis. Attention is given to the active co-channel interfering cells. Because at carrier frequencies greater than 2 GHz, co-channel interfering cells beyond the first tier becomes dominant as the cell size radius reduces. Results show that for sectorized cellular wireless communication system operating at carrier frequency greater than 2 GHz and having smaller cell size radius in a traffic environment the second tier co-channel interference still becomes active. This causes a decrease in the information capacity of the cellular wireless system. For example for a heavy vehicular traffic environment, at a carrier frequency fC = 15.75 GHz, basic path loss exponent α = 2 and cell radius R = 100, 300 and 500 m for a six sector cellular the decrease in information capacity, because of interference from the second tier was 5.47, 3.36 and 2.78%.

Full-dimension MIMO (FD-MIMO) for next generation cellular technology

This article considers a practical implementation of massive MIMO systems [1]. Although the best performance can be achieved when a large number of active antennas are placed only in the horizontal domain, BS form factor limitation often makes horizontal array placement infeasible. To cope with this limitation, this article introduces full-dimension MIMO (FD-MIMO) cellular wireless communication system, where active antennas are placed in a 2D grid at BSs. For analysis of the FD-MIMO systems, a 3D spatial channel model is introduced, on which system-level simulations are conducted. The simulation results show that the proposed FD-MIMO system with 32 antenna ports achieves 2-3.6 times cell average throughput gain and 1.5-5 times cell edge throughput gain compared to the 4G LTE system of two antenna ports at the BS.

Energy-Efficient Wireless Cellular Communications through Network Resource Dynamic Adaptation

Cellular networks represent one of the major energy consumers of communication networks and their contribution to the global carbon footprint and energy consumption continuously and rapidly increases. Improving energy efficiency of the cellular access networks become an important requirement and has recently gained considerable attention of the research community and operators. In this paper, improving cellular networks energy efficiency through dynamic adaptation of network resources is presented with foundations which justify practical realization of such approach. Paper gives insight into how the traffic pattern variations and transmitted power scaling influence on the instantaneous power consumption of the base stations. Also, impact of the base stations Tx power on two prominent energy efficiency metrics of the cellular access network is discussed. Results of a proposed optimization approach which is based on dynamic adaptation of the base stations on/off activity and the transmitted power in accordance with the spatial and temporal variations of traffic are presented. According to obtained results, dynamic adaptation of network resources can offer significant monthly energy savings on the level of complete cellular access network.

Theoretical Analysis and Experimental Study

The importance of wireless cellular communication in our daily lives has grown considerably in the last decade. The smartphones are widely used nowadays, besides voice communication; the authors routinely use them to access the internet, conduct monetary transactions, send text messages and query a lot of useful information regarding the location of specific places of interest. The use of smartphones in their day-to-day communication raises many unresolved security and privacy issues. In this paper they identify relevant security attacks in Wireless Cellular Network. The authors conduct experiments in four different platforms such as Iphone, Android, Windows and Blackberry. The packets captured through Wireshark for approximately 24 minutes, giving them a lot of information regarding security and privacy issues involving the users. A lot of useful apps installed and used by the end-users have serious issues in terms of privacy and the information exposed. Which is the better platform comparing all four and what exactly do they expose from the user’s information? What are the threats and countermeasures that the users should be aware of? The aim of the authors’ paper is to give answers to the above questions based on the data captured by conducting real-life scenarios.

Fractional frequency reuse for interference management in LTE-advanced hetnets

Improvement of cell coverage and network capacity are two major challenges for the evolving 4G cellular wireless communication networks such as LTE-Advanced networks. In this context, hierarchical layering of cells with macro base stations coexisting with low-power and shortrange base stations (corresponding to picocells or femtocells) in a service area is considered to be an efficient solution to enhance the spectral efficiency of the network per unit area. Also, such a hierarchical cell deployment, which is referred to as a heterogeneous network, or Het- Net, provides significant improvement in the coverage of indoor and cell edge users and ensures better QoS to the users. Interference mitigation between different layers is one of the key issues that needs to be resolved for successful deployment of HetNets. To this end, fast frequency response, FFR, is considered to be an efficient intercell interference coordination technique for OFDMA-based HetNets. This article focuses on evaluating three state-of-the-art FFR deployment schemes: strict FFR, soft FFR, and FFR-3 schemes for OFDMA-based two-tier HetNets comprising macrocells overlaid with femtocells. Also, a variation of the FFR-3 scheme, which is referred to as the optimal static FFR (OSFFR) scheme, is proposed. A broad comparison among all these FFR schemes is performed by using Monte Carlo simulations considering performance metrics such as outage probability, average network sum rate, and spectral efficiency. Simulation results show that, the average gains in spectral efficiency (b/s/Hz) of the network are significantly higher for the proposed scheme when compared to the strict FFR, soft FFR, and FFR-3 schemes.

A Survey of Self Organisation in Future Cellular Networks

This article surveys the literature over the period of the last decade on the emerging field of self organisation as applied to wireless cellular communication networks. Self organisation has been extensively studied and applied in adhoc networks, wireless sensor networks and autonomic computer networks; however in the context of wireless cellular networks, this is the first attempt to put in perspective the various efforts in form of a tutorial/survey. We provide a comprehensive survey of the existing literature, projects and standards in self organising cellular networks. Additionally, we also aim to present a clear understanding of this active research area, identifying a clear taxonomy and guidelines for design of self organising mechanisms. We compare strength and weakness of existing solutions and highlight the key research areas for further development. This paper serves as a guide and a starting point for anyone willing to delve into research on self organisation in wireless cellular communication networks.

Electromagnetic Macro Modeling of Propagation in Mobile Wireless Communication: Theory and Experiment

The objective of this paper is to illustrate that electromagnetic macro modeling can properly predict the path-loss exponent in mobile cellular wireless communication. This represents the variation of the path loss with distance from the base-station antenna. Specifically, we illustrate that the path-loss exponent in cellular wireless communication is three, preceded by a slow-fading region, and followed by the fringe region, where the path-loss exponent is four. The sizes of these regions are determined by the heights of the base-station transmitting antennas and the receiving antennas. Theoretically, this is illustrated through the analysis of radiation from a vertical electric dipole situated over a horizontal imperfect ground plane, as first considered by Sommerfeld in 1909. To start with, the exact analysis of radiation from the dipole is made using the Sommerfeld formulation. The semi-infinite integrals encountered in this formulation are evaluated using a modified saddle-point method for field points moderate to far distances away from the source point, to predict the appropriate path-loss exponents. The reflection-coefficient method is also derived by applying a saddle-point method to the semi-infinite integrals, and this is shown to not provide the correct path-loss exponent that matches measurements. The various approximations used to evaluate the Sommerfeld integrals are described for different regions. It is also important to note that Sommerfeld's original 1909 paper had no error in sign. However, Sommerfeld overlooked the properties associated with the so-called “surface-wave pole.” Both accurate numerical analyses, along with experimental data, are provided to illustrate the above statements. In addition, Okumura's experimental data, and extensive data taken from seven different base stations in urban environments at two different frequencies, validate the theory. Experimental data revealed that a macro modeling of the environment, using an appropriate electromagnetic analysis, can accurately predict the path-loss exponent for the propagation of radio waves in a cellular wireless communication scenario.

Antennas in Cellular Phones for Mobile Communications

The mobile industry has experienced a dramatic growth; it evolves from analog to digital 2G (GSM), then to high date rate cellular wireless communication such as 3G (WCDMA), and further to packet optimized 3.5G (HSPA) and 4G (LTE and LTE advanced) systems. Today, the main design challenges of mobile phone antenna are the requirements of small size, built-in structure, and multisystems in multibands, including all cellular 2G, 3G, 4G, and other noncellular radio-frequency (RF) bands, and moreover the need for a nice appearance and meeting all standards and requirements such as specific absorption rates (SARs), hearing aid compatibility (HAC), and over the air (OTA). This paper gives an overview of some important antenna designs and progress in mobile phones in the last 15 years, and presents the recent development on new antenna technology for LTE and compact multiple-input-multiple-output (MIMO) terminals.

Ontology for Mobile Phone Operating Systems

This ongoing study deals with an important part of a line of research that constitutes a challenging burden. It is an initial investigation into the development of a Holistic Framework for Cellular Communication (HFCC). The main purpose is to establish mechanisms by which existing wireless cellular communication components and models can work holistically together. It demonstrates that establishing a mathematical framework that allows existing cellular communication technologies (and tools supporting those technologies) to seamlessly interact is technically feasible. The longer-term future goals are to actually improve the interoperability, the efficiency of mobile communication, calls quality, and reliability by applying the framework to specific development efforts.

Telestroke Ambulances in Prehospital Stroke Management

Pre- and intrahospital time delays are major concerns in acute stroke care. Telemedicine-equipped ambulances may improve time management and identify patients with stroke eligible for thrombolysis by an early prehospital stroke diagnosis. The aims of this study were (1) to develop a telestroke ambulance prototype; (2) to test the reliability of stroke severity assessment; and (3) to evaluate its feasibility in the prehospital emergency setting. Mobil, real-time audio-video streaming telemedicine devices were implemented into advanced life support ambulances. Feasibility of telestroke ambulances and reliability of the National Institutes of Health Stroke Scale assessment were tested using current wireless cellular communication technology (third generation) in a prehospital stroke scenario. Two stroke actors were trained in simulation of differing right and left middle cerebral artery stroke syndromes. National Institutes of Health Stroke Scale assessment was performed by a hospital-based stroke physician by telemedicine, by an emergency physician guided by telemedicine, and "a posteriori" on the basis of video documentation. In 18 of 30 scenarios, National Institutes of Health Stroke Scale assessment could not be performed due to absence or loss of audio-video signal. In the remaining 12 completed scenarios, interrater agreement of National Institutes of Health Stroke Scale examination between ambulance and hospital and ambulance and "a posteriori" video evaluation was moderate to good with weighted κ values of 0.69 (95% CI, 0.51-0.87) and 0.79 (95% CI, 0.59-0.98), respectively. Prehospital telestroke examination was not at an acceptable level for clinical use, at least on the basis of the used technology. Further technical development is needed before telestroke is applicable for prehospital stroke management during patient transport.