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This paper addresses the interference optimization problem for multicast/broadcast traffics in multi-radio multi-channel wireless mesh networks equipped with directional antennas. Since a directional antenna radiates the major of transmission power to the main-lobe, it can reduce the interference. However, this may increase the number of transmissions. The adaptive directional antenna is an effective tool in controlling the above-mentioned trade-off. The main goal of this paper is to linearly model the multicast/broadcast interference in the presence of directional antennas. In this regard, the authors provide a Mixed Integer Linear Programming (MILP) formulation named “Minimum Interference and Transmission Tree with Directional Antenna (MITT-DA)” to jointly select the best multicast/broadcast routing tree, antenna beam, and transmission channel. The proposed MITT-DA is a comprehensive model which supports both directional and omni-directional antennas. It not only considers wireless broadcast advantage, but also optimizes both inter-flow and intra-flow interferences. Numerical results demonstrate the efficiency of the proposed MILP scheme in terms of the interference and the number of transmissions.

The fundamental trade-off in simultaneous wireless information and power transfer (SWIPT) is investigated from the point of view of power-splitting the signals of randomly deployed cellular base stations employing directional antennas. Leveraging tools from stochastic geometry and using realistic antenna gain profiles, we derive novel closed form expressions enabling an in-depth understanding of this trade-off and how a system-level optimization can be achieved.

The fifth generation wireless systems are expected to rely on a large number of small cells to massively offload traffic from the cellular and even from the wireless local area networks. To enable this functionality, mm-wave (EHF) and Terahertz (THF) bands are being actively explored. These bands are characterized by unique propagation properties compared with microwave systems. As a result, the interference structure in these systems could be principally different to what we observed so far at lower frequencies. In this paper, using the tools of stochastic geometry, we study the systems operating in the EHF/THF bands by explicitly capturing three phenomena inherent for these frequencies: 1) high directivity of the transmit and receive antennas; 2) molecular absorption; and 3) blocking of high-frequency radiation. We also define and compare two different antenna radiation pattern models. The metrics of interest are the mean interference and the signal-to-interference-plus-noise (SINR) ratio at the receiver. Our results reveal that: 1) for the same total emitted energy by a Poisson field of interferers, both the interference and SINR significantly increase when simultaneously both transmit and receive antennas are directive and 2) blocking has a profound impact on the interference and SINR creating much more favorable conditions for communications compared with no blocking case.

The ideal application scenario of a digital repeater is to let the repeater be operated as a transparent node in the radio access network, which means the repeater has to keep a linear gain all the time when it is forwarding data among base stations and handsets. For a handset in a cellular network, its UL transmitted power may be dramatically fluctuated by the closed loop power control to meet the required signal quality and to compensate the propagation loss due to wireless channel. When a repeater is serving the handset, it may not be able to keep a linear gain in dealing with such variant received signal strength and sometimes results in transmitting over-powered UL signal to desensitize base station reception and even to interfere the base station. In this paper, we propose a novel power control scheme, which is to adaptively adjust the maximum UL output power of a digital cellular repeater to cope with the problem mentioned above. Field test results are presented to show the effectiveness of the proposed scheme.

It has become a popular trend in using metallic housing for mobile phone. The metallic housing often posts a great challenge towards the design of internal antenna which is used commonly in mobile devices. As such, it has become a common practice that most will integrate the metallic housing as part of the antenna for the mobile phone. This paper presents an antenna solution for mobile phone with a metallic back cover. The antenna solution is for the Main Antenna operating at several frequency bands in the range of 700–960MHz, 1710–2170MHz, 2300–2400MHz as well as 2500–2690MHz, which cover the GSM850, GSM900, DCS1800, PCS1900, WCDMA2100, and various LTE Bands in the 4G cellular network. The antenna solution presented in this paper, demonstrates the use of tunable component, integrating with the metallic housing to provide flexible tuning to cover the various frequency spectrums in the 2G, 3G and 4G cellular network.

This article discusses the challenges, benefits and approaches associated with realizing largescale antenna arrays at mmWave frequency bands for future 5G cellular devices. Key design considerations are investigated to deduce a novel and practical phased array antenna solution operating at 28 GHz with near spherical coverage. The approach is further evolved into a first-of- a-kind cellular phone prototype equipped with mmWave 5G antenna arrays consisting of a total of 32 low-profile antenna elements. Indoor measurements are carried out using the presented prototype to characterize the proposed mmWave antenna system using 16-QAM modulated signals with 27.925 GHz carrier frequency. The biological implications due to the absorbed electromagnetic waves when using mmWave cellular devices are studied and compared in detail with those of 3/4G cellular devices.

The capacity and coverage area are the two most important design considerations for the planning and optimisation of cellular networks. In this paper, we report on the field measurements of received signal strength (RSS) and available data transfer rate (DTR) at user end in a fixed WiMAX network operating at 2.62 GHz. The coverage area of the network under study covers both rural and urban sectors. Comprehensive measurements of RSS and available DTR are recorded for different settings of the base station antenna tilt and the height of customer premise equipment (CPE) antenna installed at the user premise. It is a directional antenna oriented towards the base station facilitating line of sight communication. It is interesting to observe that base station antenna down-tilt of 2° results in almost 100% fulfilment of the coverage and capacity requirements in rural sector of the network. Up-tilt of 1°, yields 97% fulfilment of the requirements in the entire cell area. These settings of the base station antenna tilt offers encouraging results for the optimisation of both capacity and coverage area and establishes that antenna tilt is an effective optimisation tool to achieve better utilisation of the network resources with enhanced quality of service.

A dual-channel subwavelength low-power radio repeater system is presented in this communication. The repeater system is composed of a low-profile miniaturized receive antenna, an end-fire two-element miniaturized transmit antenna array, and a low-power high-gain amplifier chain. The isolation between the receive antenna and transmit antenna is achieved by a near-field cancellation method. To achieve a dual-channel response antennas are made wideband using parasitic elements and the open-loop transfer function is designed in a manner to present zero-crossing phase at two frequency points within the band. The closed-loop gain of the repeater system has a gain higher than that of the amplifier at the zero-crossing phase frequency points, which gives rise to repeater performance at two distinct channels. A prototype of the repeater system operating in $2.4 \sim 2.5~{\rm GHz}$ with dimensions of $39.67~{\rm mm} \times 85.39~{\rm mm} \times 3.18~{\rm mm}$ is designed and fabricated. Performance of this repeater is characterized experimentally by measuring its radar cross section (RCS). Using an amplifier chain with gain of 45 dB, it is shown that dual-channel repeater exhibits RCS values of 27.7 dBsm and 26.0 dBsm at 2.42 GHz and 2.44 GHz, respectively.

Performance of cellular networks is severely limited by intense inter-cell interference due to aggressive frequency reuse among cells. How to characterize the dependency of inter-cell interference on positions of BS antennas and users is a key question for the capacity analysis of cellular systems, which unfortunately remains elusive. In this paper, a comparative study on the uplink ergodic sum capacity of cellular systems is presented, where L_c BS antennas are either co-located at the cell center or uniformly distributed within each cell. With a large number of users, the inter-cell interference density is shown to be inversely proportional to L_c if the co-located antenna (CA) layout is adopted. With the distributed antenna (DA) layout, it scales in the order of L_{c}^{-\frac α{2}}, where α is the path-loss factor, and is much lower than that in the CA case when L_c is large. Substantial gains on the uplink sum capacity are achieved by the DA layout thanks to the reduction of inter-cell interference level. The analysis also reveals that the inter-cell interference density of each BS antenna is sensitive to its position. With the DA layout, BS antennas at cell boundary areas suffer from much higher inter-cell interference than those at the cell center, which may exacerbate the performance disparity of users in cellular systems. To tackle the cell-edge problem, a distributed antenna system (DAS) is further considered, where L BS antennas are distributed over a wide area, and each user chooses Vl L surrounding BS antennas as its virtual cell, i.e., its own serving BS antenna set. A uniform inter-cell interference density is shown to be achieved thanks to the adaptive formation of virtual cells. More importantly, by the use of virtual cell, the number of users served by each BS antenna decreases with an increasing L, implying that much of the signal processing and information exchange can be performed in a local and distributed way. The uplink ergodic sum capacity and the ergodic rate with orthogonal access of DASs with V=1 are further derived, and shown to be close to each other even with a large L. It is in sharp contrast to cellular systems where a significant tradeoff between performance and complexity has to be made when the number of BS antennas is large.

In this study, a quad-band folded slot antenna with a monopole feed line embedded in a conductive housing structure (the LCD bracket of a mobile phone) is proposed. The performance of the proposed antenna is evaluated through simulation and measurement, demonstrating that it can provide total radiation e-ciencies of more than 40% in the EGSM900, DCS, PCS, and WCDMA1 bands. Over these four bands, the total radiated power (TRP) of a prototype mobile phone using the antenna is 28.5, 27.1, 27.5, and 21dBm, respectively, while the total isotropic sensitivity (TIS) is 102.7, 104.3, 103.8, and 107.3dBm, respectively; all of these values satisfy Cellular Telecommunication and Internet Association (CTIA) requirements for over-the-area-(OTA) testing standards. The radiation performance of the proposed antenna in the calling mode is tested and shown to be within satisfactory limits; similarly, the speciflc absorption rates (SARs) of the prototype mobile phone are also found to be within standard SAR limits.

In this paper, we begin by presenting a multiband antenna for mobile phone applications operating in GSM, DCS, PCS, UMTS, Bluetooth, and LTE bands. The antenna platform includes the ground plane, the battery, the camera, and other paraphernalia that the mobile phone environment typically comprises. Results show that the platform has a significant effect on the performance of the antenna, both in terms of its bandwidth and the number of its resonance frequencies. In addition, metal rings, frequently used in a mobile phone for mechanical reasons, can also have a significant influence on the performance of the antenna in the phone. Equivalent circuits and current distributions have been derived with the objective of investigating the effects of the metal ring that embrace the mobile phone. We investigate ways in which we can modify the ring so as to restore the desired performance of the antenna, which has been previously designed to operate in the phone environment but without the presence of the ring. We show how we can control the resonances of the ring by using capacitance loading and lower its Q by loading the ring resistively at a number of different strategic locations along the ring.

The demand for wireless power transfer via magnetic resonance coupling is increasing. Magnetic resonance coupling is a new technology that achieves power transfers across a large air gap by using transmitting and receiving antennas. However, repeater antennas can enable power transmission across an even larger distance. These repeater antennas without cross coupling can be expressed as a T-type equivalent circuit. Equivalent circuits that include cross coupling and mutual inductance, which is related to the antenna position, have not been studied. In this paper, a novel way to represent a repeater antenna by an equivalent circuit and a way to determine the mutual inductance are proposed and verified by performing an electromagnetic field analysis and experiment. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 51–62, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22360

Millimeter wave (mmWave) communications has been considered as a promising technology for 5G cellular networks. Exploiting directional beamforming using antenna arrays to combat path loss is one of the defining features in mmWave cellular networks. However, previous works on mmWave network analysis usually adopt simplified antenna patterns for tractability. In this paper, we show that there are huge discrepancies between the simplified and actual antenna patterns when investigating the coverage probability of mmWave networks. Analytical expressions for the coverage probabilities are derived using tools from stochastic geometry, by considering the actual antenna pattern with the uniform linear array. Moreover, the impact of the array size is investigated, which cannot be revealed from existing results with simplified antenna patterns. Numerical results will show that large-scale antenna arrays are required for satisfactory coverage in mmWave cellular networks. Furthermore, dense mmWave cellular networks are shown to achieve much higher rate coverage than conventional sub-6 GHz cellular systems.

A high-efficiency 3-D harmonic repeater for narrow band, wireless sensing applications is described herein. This repeater consists of a diode doubler and conjugate-matched 3-D receive and transmit antennas. The antennas are designed on the surface of a cube in part to provide a convenient volume for packaging the sensor electronics. The device operates by receiving a 2.4-GHz signal and re-radiating a 4.8-GHz signal and has been optimized for an RF input power level between - 30 and -20 dBm with zero dc power. The design enables the return signal to be readily modulated with very low ( ; 50 m in a free space environment. To the best of the authors' knowledge, the presented harmonic repeater has the best overall performance among previously published designs, in terms of conversion gain, communication range, and occupied electrical volume. A new approach for remote calibration of passive sensors using orthogonal polarization of the interrogation signal is also proposed in this paper.

A new concept for development of a high-gain and miniaturized radio repeater is presented in this paper. The proposed system utilizes a small array of low-profile miniaturized planar antennas with vertically polarized radiation pattern as well as a modified ring hybrid coupler as the array power distribution circuit and a low-power high-gain amplifier chain. In this configuration, a small receiving antenna is placed between a pair of transmit antenna array, which are fed 180° out of phase. The transmit array creates a null-plane where the receive antenna is placed, and this way an isolation value between the transmit and receive antennas in excess of 50 dB is achieved, while the shortest distance between the transmit and receive antennas is less than 0.16λ0. The proposed repeater has a small form factor and occupies a small volume (0.22λ02 × 0.03λ0). A prototype of the miniaturized radio repeater is fabricated and measured to verify the system performance. A radar cross section of the repeater is measured for evaluating the overall system gain and its bandwidth. It is shown that an amplifier chain with a gain of 50 dB can be inserted between the transmit and receive antennas, which results in the measured repeater RCS of 21.3 dBsm.

In this paper, we propose a directional spread-spectrum modulation (DSM) signal transmitted by a switched antenna array for physical layer security communication. The main idea is that the antenna hopping scheme is designed according to a spreading sequence. Fundamental frequency component and all harmonic components generated by antenna hopping are used to form the DSM signal with the characteristic of being directional. This signal is associated with the spreading sequence and the direction of the desired receiver because of DSM signal modulated both in the baseband and the antenna level. In this way, the desired receiver with a single antenna demodulates the receive signal as traditional spread-spectrum signal, whereas eavesdroppers cannot extract any useful information from the receive signal even if eavesdroppers know the spreading sequence of DSM signal. Finally, simulation results show that the proposed signal offers a more secure transmission method for wireless communication compared with the traditional spread-spectrum signal. Copyright © 2012 John Wiley & Sons, Ltd.

In this paper, isolation between the wireless repeater antenna systems for long term evolution (LTE) bands (700MHz/800MHz) has been investigated. To improve the isolation between repeater antennas, the compact elliptical planar monopole (LTE 700/800MHz) repeater antenna with Isolation >50dB, Gain >6.75dBi, F/B ratio>12dB is analyzed and designed.

In order to use more efficiently limited frequency resources at the broadcasting band and to eliminate blanket area of the terrestrial broadcasting and to improve broadcasting quality. The importance of repeaters has increasing continuously. However, in case of T-DMB digital on channel repeater in OFDM systems, some of the signal radiated feedback again at the receiver antenna. So it generates feedback signal interference in repeater system. Also phase noise increases ICI(Inter Carrier Interference). It affects seriously the frequency domain equalizer. In this paper, we remove the feedback signal interference by LMS with correlation. Also we propose an effective equalizer algorithm that can remove ICI caused by phase noise and the power amplifier`s back-off. In this simulation results, this system is satisfied the performance of BER

Several repeater systems are used to enhance the cell coverage to location such as shadow and rural areas in mobile systems. But the general RF repeater solutions are not suitable for high power outdoor environment because it has the weakness such as self oscillation problem With adoption of a adaptive digital filter technology, feedback interference cancellation repeater prevents oscillation by detecting and canceling the unwanted feedback signal between transmission and receiver antenna. In this paper, dual NLMS based interference cancellation method is proposed and the step size adaptation can be implemented by the estimation of the feedback channel Doppler frequency characteristics. The performance of the proposed algorithm is quantified via analysis and simulation for the static and multipath fading feedback channels.

The effect of a frequency-selective surface (FSS) on enhancing the isolation between a donor and a coverage antenna for indoor WCDMA repeater antenna systems is presented.A unit cell of the proposed FSS consists of a half-wavelength resonator, an FR4 substrate, and a ground plane. Embedding it on the wall of each reflector for a donor and service antenna, the measured isolation enhancement is about 10 dB. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:697–700, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25806

Multiple-input multiple-output (MIMO) repeater systems have been discussed in several published papers. When a repeater has only one antenna element, the propagation environment is called keyhole. In this kind of scenario the achievable channel capacity and link quality are decreased. Another limit is when the number of the antenna elements of a repeater is larger than that of a MIMO transceiver, the channel capacity cannot be increased. In this paper, in order to obtain an upper bound of the channel capacity, we express a propagation process of the distributed MIMO repeater system with amplify-and-forward method by the numerical formular, and optimize the position of each repeater.

This paper studies the problem of detection of directional antennas and omni-directional antennas by hostile detection systems. We present a model for calculating the probability of detecting a transmitter at arbitrary location around the transmitter. Our study shows that, if a directional antenna employs the same transmit power as an omni-directional antenna, the directional antenna can not decrease the probability of being detected. In some scenarios, a directional antenna is more likely to be detected than an omni-directional antenna. However, if a directional antenna provides the same Effective Isotropic Radiated Power in the direction of the receiver as an omni-directional antenna, the transmit power needed by a directional antenna to send data is much less than that of an omni-directional antenna. In this scenario, the probability of detecting a directional antenna is reduced by over 90%. This reveals that directional antennas can be used to build a secure path to send data at low probability of being detected by adversaries.

A chip antenna formed by using an FR4 chip base and a folded-loop metal pattern embedded therein for internal mobile phone antenna application is presented. The folded-loop metal pattern is embedded in two different layers inside the FR4 chip base to achieve a compact structure, and a coupling gap is introduced to successfully excite two wide operating bands at about 900 and 2000 MHz to cover GSM850/900/1800/1900/UMTS, 2.4-GHz WLAN, and 2.5-GHz WiMAX operations; that is, a seven-band internal mobile phone antenna for covering WWAN/WLAN/WiMAX operation is obtained. The proposed chip antenna also occupies a small volume of 4 × 5 × 40 mm3 (0.8 cm3) and shows a low profile of 5 mm when mounted on the system circuit board of the mobile phone, making it suitable for thin mobile phone applications. The proposed chip antenna is studied and tested. The SAR effect of the antenna is also analyzed in the study. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 543–549, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24063

A promising six-band internal antenna suitable for small-size mobile phone application is presented. The mobile phone considered in this study has a system ground plane of length 60 mm only, much less than that of the general mobile phones. For such small-size mobile phones, it is not easy for the embedded antenna to achieve a wide operating band at 900 MHz for GSM850/900 operation. The proposed antenna solved the problem with a reasonable occupied volume. The antenna mainly comprises three radiating elements of two longer monopoles and a shorter monopole, which are configured to occupy a volume of 3.6 cm3 only. The two longer monopoles incorporating an external parallel chip inductor lead to the successful excitation of a wide operating band for the antenna's lower band to cover GSM850/900 operation. Moreover, the three monopoles together contribute to the excitation of a very wide upper band to cover GSM1800/1900/UMTS/WLAN operation. That is, the antenna can perform six-band operation for WWAN and WLAN communications. The proposed antenna is studied in detail in this article. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 2242–2247, 2008; Published online in Wiley InterScience (www.interscience.wiley.com).DOI 10.1002/mop.23659

With the introduction of digital cellular phones, hearing-aid users have experienced a severe buzzing noise caused by the interaction between digital cellular phones and hearing aids. The cellular-phone industry, the hearing-aid industry, and consumers have been seeking a solution for the interference issue. Efforts reported in the literature have focused on measurements, modeling, and evaluation of interference and RF emission, but not on methods to solve the problem. In this paper, we focus on the causes of the interference and an understanding of the problem. We also present a method to reduce near-field electromagnetic energy around a cellular phone, mitigating the interference between cellular phones and hearing aids. The theoretical investigation of both the radiation mechanisms and fundamental limits on antennas suggested that a low-g antenna, such as an ultra-wideband antenna, could reduce the near-field intensity. Simulations and measurements were performed at 900 and 1880 MHz, using both low- and high-Q test antennas mounted on a mock cellular phone. The results showed that the peak electric and magnetic near-field strengths of the low-g test antenna were lower than those of a high-Q test antenna by at least 5 dBV/m and 4 dBA/m, respectively. The improvement in the near-field performance for the low-g antenna was without any sacrifice in far-field performance. Furthermore, in the presence of a human head, the simulation results showed that the radiation efficiency of the low-Q test antenna was better than that of the high-Q test antenna.

A surface-mount chip antenna integrated with the speaker in the mobile phone for GSM/DCS/PCS/UMTS multiband operation is presented. The antenna is to be mounted on the top no-ground portion of the system circuit board of the mobile phone as an internal multiband antenna, and the speaker in the mobile phone can be inset into the chip base of the antenna to achieve a compact integration of the antenna and the speaker. Moreover, the chip antenna occupies a small volume of 35.5 × 10 × 7 mm3 (about 2.5 cm3) only. Details of the proposed chip antenna are presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1126–1132, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23287

An internal wideband metal-plate monopole antenna for mobile phone applications is presented. The antenna is easily fabricated by bending a single metal plate and suitable to be embedded within the casing of a mobile phone as an internal antenna. Moreover, the antenna shows a wide operating bandwidth of about 5 GHz (about 1.8–6.7 GHz), making it easy to cover the UMTS band (1920–2170 MHz) and the 2.4–GHz (2400–2484 MHz) and the 5.2/5.8-GHz (5150–5350/5725–5825 MHz) WLAN bands for mobile/WLAN dual-mode operation of a mobile phone. The proposed antenna is studied in detail, and the experimental and simulation results of the constructed prototype are also presented. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 1741–1744, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23546

The main criteria for designing the upcoming cellular systems are: More network capacity and less energy consumption. Recently, distributed antenna system (DAS) has received considerable attention due to its potential to provide higher spectral efficiency and uniform coverage for cellular networks. In this regard, this article compares the performance of DAS with centralized antenna system (CAS) in LTE-Advanced system in term of cell throughput and energy efficiency (EE), where practical restrictions such as out-of-cell interference, path-loss, and small-scale fading are taken into account. Furthermore, the EE degradation is investigated under two different sleep-mode scenarios (moderate and low loaded networks) where different number of antennas are activated. Finally, we investigate the impact of channel bandwidth enhancement on the compensation of EE degradation due to the antenna muting during the sleep modes. The results reveal that DAS considerably outperforms CAS in term of EE (up to 56.6%). Furthermore, the simulation results show that during the sleep modes, by optimally assigning channel bandwidth, the EE-loss, not only can be compensated, but also EE can be significantly improved, where the proposed methodology guarantees a considerable power-saving for the cellular network (up to 27.63%).

Exploring innovative cellular architectures to achieve enhanced system capacity and good coverage has become a critical issue towards realizing the fifth generation (5G) of wireless communications. In this context, this paper proposes a novel concept of an intelligent Amplify and Forward (AF) 5G repeater for enabling the densification of future cellular networks. The proposed repeater features a Spectrum Sensing (SS) intelligence capability and utilizes such intelligence in a complementary fashion in comparison to its existing counterpart (e.g., Cognitive Radio) by detecting the active channels within the assigned spectrum. This intelligence allows the proposed repeater to carry out selective amplification of the active channels in contrast to the full amplification in conventional AF repeaters. Furthermore, the performance of a Frequency Division Multiple Access (FDMA) based two hop cellular network utilizing the proposed repeater is evaluated in terms of the system throughput. Simulation results demonstrate up to 13 % increase when compared with the conventional repeaters. Moreover, the effect of SS errors on the system capacity is analyzed.

Computer-telephone-integration (CTI) interference may happen when a mobile phone is operated adjacent to a digital device. This device could be a tablet or a laptop computer, the mobile phone nearby is used as a gateway for the device, and therefore the CTI interference from the mobile phone may disrupt the device. To evaluate the device immunity to such an interference, a near-field testing should be performed. For this testing, the transmitting antenna representing the mobile phone should be carefully selected since the interference is a near-field effect and the antenna performance could be affected reversely by the nearby device. In this paper, the optimal type of antenna is suggested. This type of antenna shows to be insensitive to the nearby device. Both simulated and measured results are obtained to support the suggestion.

The use of repeater for the support of high data rate data transmission and the extension of cell coverage is imperative for the Wibro system, which is based on the IEEE 802.16e standardization. Generally, if the separation between transmitting and receiving antennas is not sufficient, the oscillation of repeater and the interference due to the feedback signals from original transmitted signal may be occurred. Hence, the Interference Cancellation System (ICS) should be implemented as the important part of the repeater system for the mobile cellular systems in order to eliminate an unwanted signals from the corrupted signals in the receiver. In this paper, we propose an adaptive techniques for the LMS-based interference cancellation methods by changing the step size according to the variation of channel environment in order to improve the performance degradation which is occurred by using the fixed step size approach. Simulation results show that the proposed scheme attains a little lower BER performance and much faster convergence speed compared to the conventional LMS-based interference cancellation techniques. The proposed scheme can be applied to other OFDM-based cellular systems and also be expected to achieve a similar performance improvement to IMT-advanced system, which is called as the next generation mobile communication standards.

In view of lack of checking devices for the frame structure of DMX512 protocol, this paper presents a design scheme of pulse interference suppressor. The interference suppression repeater is composed of PIC microcontroller, level conversion and isolating circuit, and through the repeater, local network data transmission rate can be doubled and the check of the data transmission is realized. The design scheme can effectively reduce more than 95i¾ź% of the given communication interference environment operation error, and improve the reliability of the DMX512 application system.

A shorted patch antenna suitable for application in the sliding mobile phone as an internal antenna is presented. The shorted patch antenna is mounted at the bottom end of the lower ground plane of the mobile phone, and can generate a wide operating band for UMTS (1920–2170 MHz) operation in the talk condition (the mobile phone is slid open for use). In addition, when the mobile phone is in the standby condition (not slid open), the antenna can still provide acceptable impedance matching for operating frequencies over the UMTS band. Details of the antenna design are described, and experimental results of a constructed prototype are presented. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 48: 726–729, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.21457

The authors have developed a method of suppressing the radio echo generated by the coupling of transmitting and receiving antennas at the repeater station for a cellular system that repeats wireless signals at the same frequency. The method includes a function to automatically detect and suppress the radio echo generated by reflection from buildings near the repeater as well as the direct coupling between the transmitting and receiving antennas. A repeater for cdma2000 based on this scheme is fabricated, with the antenna of the repeater pointed to the base station and the antenna pointed to the mobile station installed on the same pillar. When the interference suppression function is activated, it is found that the repeater gain of the repeater may exceed 80 dB. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 89(4): 32–41, 2006; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20200

A novel compact ultra-wideband (UWB) metal-plate monopole antenna for mobile-phone applications is presented. The antenna is easily fabricated from a single metal plate and is suitable to be embedded within the casing of a mobile phone as an internal antenna. Further, the antenna shows a wide operating bandwidth of about 6 GHz (about 1.9–7.9 GHz), which makes it easily cover the UMTS band (1920–2170 MHz) for mobile communications and the 2.4-GHz (2400–2484 MHz) and 5.2/5.8-GHz (5150–5350/5725–5875 MHz) bands for WLAN communications. That is, the antenna is suitable for application in a UMTS/WLAN dual-mode mobile phone. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 265–268, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20791

There have been many proposals for media access control protocols in packet radio networks (PRN) in which transmission efficiency is improved by using a directional antenna. This paper assumes that the topology of the PRN and the data to be transmitted among the stations are specified, and discusses the essential effectiveness of using the directional antenna, as independent of the protocol, using the shortest time needed to complete all data transmissions as a measure. It is shown that the number of directional antennas in each station is sufficient if it is equal to the number of neighboring stations, and that the effectiveness of the directional antenna is more pronounced when the PRN has a high density. The effectiveness when the communication buffer used to store the data to be sent or received is combined with the directional antenna is also discussed. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 85(9): 51–58, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1125

A Study of a repeater concept of a transmitting antenna (Tx) for wireless battery charging system of a portable devices is reported in this paper. The objective is to extend the charging area by using the repeater coil concept. The repeater coil is located near the Tx active coil in the same plane of Tx active coil without any direct connection from a source. The operating frequency at 6.78MHz is chosen by following the frequency A4WP wireless battery charging system specification. The proposed Tx antenna is designed for extending a charging distance of the portable devices on xy-plane (such as on table) using a repeater coil (called Rp). The charging area of the proposed antenna is larger than a conventional single Tx antenna. The repeater coil is the same size of the single Tx antenna. The single Tx antenna transfers the magnetic energy to the repeater coil. The receiving antenna (small coil) in a mobile phone picks up the magnetic energy from the repeater coil. The suitable separating distance between the single Tx coil and the repeater coil will be investigated. The study is performed by analyzing the power transfer efficiency of the proposed antennas via scattering parameters [S-parameters] and of the two port network representation. The 50 Ohms system impedance is chosen in this study. The optimum impedance matching at the Tx and Rx sides are considered. It is found that the charging area is increased by using the proposed repeater coil antenna.

This paper considers the problems associated with cellular network coverage for mobile phone users within energy efficient buildings. As energy efficient building materials can significantly attenuate radio frequency (RF) signals, a two story energy efficient building is considered having external wall attenuation of 20 dB, and an internal floor attenuation of 3 dB. Results are presented showing how external signals propagate within the building and how a passive antenna system can be utilized to increase the internal signal coverage by up to 30 dBm.

Full-dimensional multiple input multiple output (FD-MIMO) is a practical implementation of massive MIMO in cellular communication systems. FD-MIMO relies on an active two-dimensional antenna grid at the base stations and harvests the benefits of both azimuth and elevation beamforming. This paper briefly introduces the concept of FD-MIMO, and surveys the recent research results and applications of active antenna systems (AAS) technology. The key concepts discussed range from antenna patterns and channel modeling to vertical sectorization and heterogeneous networks deployment. The paper focuses on the benefits of FD-MIMO in an urban environment with high rises and three-dimensional user deployment. It demonstrates the importance of FD-MIMO in enhancing the performance of cellular networks.

This paper presents the effects of cell size, directional antenna, diversity reception, and log-normal shadowing on the reverse-link operated code division multiple access (CDMA) capacity. The capacity improvement by a small-cell approach associated with the directional terminal antenna is also suggested. The simulation results show that the directional terminal antenna suppresses the outside cell cochannel interference caused by the small-cell approach, thereby resulting in significant capacity improvement. It is also found that two-branch antenna diversity reception improves the capacity by 2.0/spl sim/2.5 times relative to a single antenna, and the log-normal shadowing with a standard deviation of 10 dB decreases the capacity by 10/spl sim/13% in comparison with that for 2-dB standard deviation.

In recent years, electromagnetic interference (EMI) on implanted cardiac pacemakers due to mobile phones has become a large concern. Here, in the previous studies, dipole antenna or monopole antenna loaded to a metallic case which simulates the PCB, battery etc. were mainly employed as a mobile phone model. However, recent mobile phones are generally equipped with an embedded antenna such as planar inverted-F antenna (PIFA) which have different characteristics from linear antenna. In this study, a realistic mobile phone model consists of 0.1×0.1×0.1 mm3 voxel was employed for calculation of the interference voltage induced at the pacemaker, in order to evaluate the characteristics of the EMI due to mobile phones with existing communication systems. It is consequently shown that the realistic mobile phone model has different characteristics of the interference voltage from those of the simple mobile phone model such as half-wavelength dipole antenna.

We have implemented a same-frequency cellular repeater that uses adaptive signal processing to cancel the feedback path, thereby allowing high gain while maintaining stability. Preliminary results are presented for a real-time laboratory demonstration using an FPGA development board, realizing cancellation of about 20 dB over a 10-MHz bandwidth.

A same-frequency cellular repeater is proposed that uses adaptive signal processing to cancel the feedback path, thereby allowing high gain while maintaining stability. This technique has application wherever it is desired to boost signal strength in outlying areas of cell coverage, particularly inside homes and buildings. It is intended to provide useful gain without needing special donor/transmit antennas requiring directional gain, separation beyond a meter or so, or roof installation. A simulation of a 900-MHz repeater with 10-MHz bandwidth is presented that demonstrates the feasibility and determines the effect of parameter values on convergence and cancellation performance.