Downlink Frequency Research Articles

이동형 위성단말을 위한 20 GHz 대역 채널 특성 분석

Abstract This paper describes the analysis results of channel characteristics in the operating area of satellite OTM(On-The-Move) terminal. The communication channel between the Koreasat-5 and OTM terminal on a test car is measured and recorded from Daejeon to Daecheon, using the downlink frequency of around 20 GHz. And the measurement data are divided into two classes ; highway environment and national road environment, and then are statistically analyzed. The statistical evaluation of satellite channel is conducted by using probability density function and Markov model and then presents average connection duration(ACD), average fade dura-tion(AFD), and level crossing rate(LCR) of highway environment and national road environment. Finally the statistics data of the two environments are compared with each other.Key words: Satellite Communication Channel, On-The-Move, Average Connection Duration, Average Fade Duration, Level Cross- ing Rate @[#\]D^(Agency for Defense Development)*_`+\Z/ab\#(Department of Electronic Engineering, Chungbuk National University)Manuscript received October 8, 2013 ; Revised November 25, 2013 ; Accepted December 1, 2013. (ID No. 20131008-090)Corresponding Author: Kun-Sup Kwon (e-mail: kevin.kwon@add.re.kr)

Sideband Noise Mitigation in a Co-Located Network Involving CDMA2000 and WCDMA System

The installation of base station antennas within close frequency range in a co-located scenario constitutes a major interference for radio spectrum engineers. In a co-located setting involving a downlink frequency of CDMA2000 (1960 -1990MHz) and an uplink frequency of WCDMA (1920-1980MHz) as used in the telecommunication industry in Nigeria, the base station receiver is required to receive low amplitude desired signals in the presence of strong transmitting power signals resulting to sideband noise interference. The paper identifies the major mechanism of the sideband noise and proposes the application of a Butterworth Band Pass Filter (BBPF) as a mitigation technique. The technique was developed through the applications of empirical and mathematical analysis conducted in two different scenarios to evaluate the levels of the interference signals on the WCDMA receiver from CDMA2000 transmitter. The first scenario involved a standalone un-collocated WCDMA network while the second scenario involved a co-located network (CDMA2000 and WCDMA). A 52dB required attenuation specification was obtained for the BBPF design.

Flexible Proportional-Rate Scheduling for OFDMA System

In this paper, we study the sum-rate maximization algorithms for downlink and uplink orthogonal frequency division multiple access (OFDMA) systems under proportional-rate constraint (PRC) and minimum-rate constraint. We develop a low-complexity weighted channel signal-to-noise ratio (w-SNR)-based ranking scheme for user selection on each subchannel in OFDMA combined with waterfilling (WF) power allocation. Both offline and online optimization algorithms are developed to optimize the SNR weight vector to maximize the sum rate while satisfying several constraints, such as PRC. The offline weight optimization technique relies on the analytical throughput results developed in this paper, and the online weight adaptation method tracks the user rates and meets the PRC using a subgradient search. Furthermore, we introduce a novel SNR operating region test to enhance the multiuser diversity gain and the sum rate. The proposed schemes have a low complexity, which is linear to the numbers of users and subchannels. Simulation results verify the accuracy of the developed analytical rates and fairness formulas, and show that the proposed w-SNR schemes can achieve higher sum rates than several benchmark schemes that provide the PRC with either short-term or long-term fairness.

Stochastic method for determination of the organ‐specific averaged SAR in realistic environments at 950 MHz

The organ-specific averaged specific absorption rate (SARosa ) in a heterogeneous human body phantom, the Virtual Family Boy, is determined for the first time in five realistic electromagnetic environments at the Global System for Mobile Communications downlink frequency of 950 MHz. We propose two methods based upon a fixed set of finite-difference time-domain (FDTD) simulations for generating cumulative distribution functions for the SARosa in a certain environment: an accurate vectorial cell-wise spline interpolation with an average error lower than 1.8%, and a faster scalar linear interpolation with a maximal average error of 14.3%. These errors are dependent on the angular steps chosen for the FDTD simulations. However, it is demonstrated that both methods provide the same shape of the cumulative distribution function for the studied organs in the considered environments. The SARosa depends on the considered organ and the environment. Two factors influencing the SARosa are investigated for the first time: conductivity over the density ratio of an organ, and the distance of the organ's center of gravity to the body's surface and exterior of the phantom. A non-linear regression with our model provides a correlation of 0.80. The SARosa due to single plane-wave exposure is also investigated; a worst-case single plane-wave exposure is determined for all studied organs and has been compared with realistic SARosa values. There is no fixed worst-case polarization for all organs, and a single plane-wave exposure condition that exceeds 91% of the SARosa values in a certain environment can always be found for the studied organs.

Isolation improvement of a TRx stacked microstrip patch antenna using double spur-line band rejection filters

In this article, we present a TRx stacked microstrip patch antenna with improved isolation using double spur-line band rejection filters (DSL-BRFs).The typical TRx stacked microstrip patch antenna designed to operate at Ku-band with downlink frequency band of 12.25–12.75 GHz and uplink frequency band of 14.0–14.5 GHz had inherent isolation of 16 dB within TRx-band. The isolation performance of the antenna was improved by at least 23.45 dB in Rx-band and 17.82 dB in Tx-band after introducing the DSL-BRFs into Tx- and Rx-feed networks, respectively. Because the DSL-BRFs are compatible to be embedded in 50-Ω transmission lines, the TRx antenna with the filters are remained in as same size as the antenna without filters. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1444–1448, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27632

Radiofrequency Exposure in Greek Indoor Environments

This is the first measurement campaign that takes place in Greece in order to assess the exposure levels in different microenvironments (offices, bedrooms, living rooms, schools). Due to the exponential growth in the use of wireless network devices, the aim of this work was to perform indoor measurements with the use of personal dosimeters. The measurement period was 3 d in each of the 40 different locations that were selected, both in the urban and suburban area of Thessaloniki, the second largest city of Greece. The measurements took place from 23 July 2010 to 19 January 2012. After processing the obtained data with the robust regression on order statistics (ROS) method, various statistical exposure quantities were calculated. Compared to similar measurement campaigns across Europe, a larger proportion of measurement data above the detection limit for specific frequency bands (at most 56% for the DCS Rx frequency band) was found. Furthermore, mean exposure levels in the mobile downlink frequency bands were higher than those in other studies (GSM Rx: 0.259 V m, DCS Rx: 0.131 V m, UMTS Rx: 0.12 V m), yet many times below the ICNIRP guidelines. On the other hand, maximum exposures were found to be of the same magnitude (GSM Rx: 0.38 V m, DCS Rx: 0.3 V m, UMTS Rx: 0.28 V m). These measurement results indicate that signals from mobile base stations are dominant in workplaces and schools, whereas wireless phones and computer networks play the leading role in home environments. While the former reach their maximum values during daytime, the latter have an observable increase in the evening after work hours.

Compact UWB microstrip antenna with satellite down-link frequency rejection in X-band communications by etching an E-shaped step-impedance resonator slot

A multiresonance and UWB monopole antenna with frequency band-notched function in 7.25–7.75 for downlink of X-band satellite communication systems is presented.Proposed antenna consist of a square radiating patch with a pair of L-shaped slots, a feed-line with an E-shaped step-impedance resonator (SIR) slot, and a ground plane with a pair of L-shaped conductor-backed plane. In this design, by cutting a pair of modified L-shaped slots with variable dimensions on the radiating patch and also by inserting a pair of L-shaped conductor-backed plane, additional resonances are excited and hence much wider impedance bandwidth can be produced especially at the higher band 125% (2.95–13.36). To achieve a band-notched function an E-shaped SIR slot was inserted in the feed-line. Simulated and experimental results obtained for this antenna show that it exhibits good radiation behavior within the UWB frequency range. The designed antenna has a small size of 12 × 18 mm2. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:922–926, 2013; View this article online at wileyonlinelibrary.com. DOI: 10.1002/mop.27456

Resource allocation with interference mitigation in femtocellular networks

ABSTRACTThe introduction of femtocells enabled high data rates and better indoor coverage without the need for expanding or increasing the density of cellular networks deployment or upgrading the cellular network infrastructure. Despite this direct advantage, the introduction of femtocells challenges traditional interference mechanisms because of the ad hoc and dense nature of femtocell deployment. In this paper, we propose an optimal downlink frequency assignment scheme. The proposed algorithm is modeled as a transportation problem to optimally allocate frequency subcarriers with the objective of maximizing the system capacity. The scheme can be used as a benchmark for assessing the suitability of interference mitigation schemes in femtocellular networks.Copyright © 2012 John Wiley & Sons, Ltd.

RANCANG BANGUN ANTENNA WAJANBOLIC DENGAN DIAMETER 46 CENTIMETER PADA FREKUENSI 1900 MHz UNTUK MEMPERKUAT PENERIMAAN SINYAL WCDMA

Ichsyan Nafik, Yuniarto, in paper a 1900 MHz, 46 cm wajanbolic antenna design to strengthen wcdma signal reception explain that the antenna is a device used to transmit or receive electromagnetic waves electromagnetic waves. Reception using an antenna will amplify the signal acquisition in accordance with the ability of the antenna itself. Signal instability that often occurs in WCDMA networks makes the need for strengthening the acquisition of the signal is very large. Antenna Wajanbolic is one option reinforcement signal acquisition. In WCDMA networks, downlink frequency used at 2100 MHz, while the uplink frequency to 1900MHz. Antenna wajanbolic Must ditune to resonate in the uplink frequency is 1900 MHz. The final project focuses on making wajanbolic antenna for Line of Sight (LoS) who works at a frequency of 1900 MHz for WCDMA (3G). In accordance with the name wajanbolic antenna, this antenna uses a reflector from the pan, with a waveguide of modified pipes are coated with aluminum duct tape, and a signal receiver using a USB 3G modem. From the results of the testing and analysis of the results showed that wajanbolic antenna is directional antenna that has the directivity signal. This wajanbolic got an antenna gain of 16 dB value. Keyword: wajanbolic antenna, WCDMA, Line of Sight (LOS)

Dynamic Downlink Frequency and Power Allocation in OFDMA Cellular Networks

In order to mitigate inter-cell interference and cope with network, traffic, and channel fluctuations in space and time, Orthogonal Frequency Division Multiple Access (OFDMA) based cellular networks should be equipped with dynamic frequency and power allocation algorithms. Although dynamic frequency and power allocation has been well studied separately, very few results have been reported on dynamic joint frequency and power allocation. In this paper, we propose a dynamic frequency and power allocation algorithm for the DownLink (DL) of OFDMA-based cellular networks, where frequency resources are allocated to cells by a central broker to minimize long-term cell-edge inter-cell interference. Moreover, each cell independently assigns its available frequency resources and power to users in a way that its total DL transmission power is minimized while meeting the throughput demands of its users. Simulation results show that the proposed algorithm provides significant improvements in network outage performance, capacity, and throughput as compared with existing schemes.

Uplink and Downlink of LTE-Release 10 in Cellular Communications

In LTE-Advanced, orthogonal frequency division multiple access (OFDMA) has been selected as the multiple access scheme for downlink and single-carrier frequency division multiple access (SC-FDMA) for uplink. OFDM is an attractive modulation technique in a cellular environment to combat frequency selective fading channels with a relatively low- complexity receiver. However, OFDM requires an expensive and inherently inefficient power amplifier in the transmitter due to the high peak-to-average power ratio (PAPR) of the multicarrier signa l. This paper, presents the main components of LTE-Advanced including the all the details of Uplink (SC-FDMA) and Downlink (OFDMA). Also this paper clarifies the main reasons of using SC-FDMA in uplink and using OFDMA in downlink only, in order to obtain flexible mobile communication technology. DOI: http://dx.doi.org/10.11591/ij-ict.v1i1.557

Design of a wideband 377 Ω E-shaped patch antenna for RF energy harvesting

The design of a 377 Ω E-shaped patch antenna with partial ground plane is presented and discussed in this article. Two parallel slots are introduced into the conventional patch antenna, and it was investigated by the currents through the patch to enhance its bandwidth. The antenna is designed, fabricated, and measured for downlink frequency band of GSM 900, which shows an impedance bandwidth of 29.03% (277 MHz) at 954 MHz. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:569–573, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26607

Reconfigurable 4 × 4 Switch Matrix for Ka-Band Geo-Stationary Satellite Mission

A 4 × 4 reconfigurable switch matrix based on low temperature co-fired ceramic technology for Geo-stationary satellite mission at Ka-band downlink frequencies (17–22 GHz) is presented. In comparison to its predecessor, the new generation of switch-matrix features augmented functionality whilst an overall reduced size (40%). The distinguished characteristics include the shifting of matching networks from top-layer into the embedded layers of the multilayer ceramic stack and the elimination of two external peripherals required to digitally control the bipolar current sources of the PIN-diodes based switch integrated circuits. As an additional functionality, four passive transparent paths between corresponding input and output are integrated within the module, to exhibit rudimentary transmission through the module in case of on-board power failure.

Raised Cosine-Like Companding Scheme for Peak-to-Average Power Ratio Reduction of SCFDMA Signals

The 3rd generation partnership project long term evolution standard uses orthogonal frequency division multiplexing access in downlink and single carrier frequency division multiple access (SCFDMA) scheme for the uplink transmissions, which utilizes single carrier modulation and frequency domain equalization. In this paper, we proposed a Raised Cosine-like companding scheme to reduce the peak-to-average power ratio (PAPR) of SCFDMA signals. The proposed scheme can transform the original SCFDMA signals into Raised Cosine-like-distributed. Moreover, this scheme can compress the large signals, while maintaining the average power constant. Computer simulation results show that the proposed companding scheme can offer better PAPR reduction by properly choosing the parameters.

Compact dual-band axially corrugated profiled horn for prime-focus reflector antenna

This paper reports a new compact dual-band axially corrugated profiled horn feed (DBCPH) for prime-focus reflector antenna at C-band (uplink and downlink frequency bands with bandwidth ratio of 1.6). DBPCH consists of one sinusoid profiled section and two internal axial corrugations (internal short-circuited ring slots), for obtaining a multimode horn feed. Such a blended structure is optimized over the specified frequency bands (3.68–3.70 and 5.865–5.915 GHz) to achieve various performance objectives (such as compactness, return loss, polarization purity, etc.). Measured and predicted results show that DBCPH provides better return loss >18.6 dB, low cross-polarization (better than −32 dB), and adequate edge taper at ±48° (8.5–11.7 dB) along with compact size (1.3λ aperture diameter and 0.88λ length at lower frequency). The horn would be used as a feed element for front-fed prime-focus reflector for pencil beam spacecraft antenna application.

Achieving Centimeter Ranging Accuracy with Triple-frequency Signals in C-band Satellite Navigation Systems

The Chinese Area Positioning System (CAPS) uses communication carriers at C-band for navigation services and all the navigation and ranging signals are generated at ground stations instead of onboard satellites. The C-band communication downlink frequency ranges from 3.4 GHz to 4.2 GHz, allowing CAPS to choose three frequencies for precision navigation. The paper identifies optimal code and phase combinations from three frequencies so that the ionospheric delays can be removed or mostly reduced in their differences and ambiguities of selected combined phase signals can be determined over a few epochs at a high success probability. Any two of these ambiguity-fixed phase combinations can be used to estimate the ionospheric corrections and form an ionosphere-free phase measurement for position estimation. Analysis shows that the third frequency in principle is chosen close to the middle of the two outer frequencies to minimize the time required for smoothing of the ionospheric corrections.

RANCANGAN AWAL SISTEM KOMUNIKASI SATELIT IMAGE PROCESSING LAPAN-TUBSAT

The LAPAN-TUBSAT is a joint reseaverd between LAPAN and TECHNICAL UNIVERSITY OF BERLIN for image processing application. The satellite will be built in with half-duplex transmission system, with uplink frequency is uHF-band 435.075 Mhz in minimum data rate 1200 pbs, while the downlink frequency is S-band 2.2 GHz use data rate 38400 bps. The uplink frequency will functioned for command and donwlink frequencies for telemetry data and image data. The main communication payload consists of transmitter and antenna s-band, tranceiver and antenna UHF-band, two cameras with resolution 50 mm and 1000 mm with PAL standard, data and video multiplexes, on borad data handling and power control unit. The ground station consists of TT and C operates in UHF-band and ground receiver processing operates in S-band frequency. The minimum image signal quality received is 45 dB for BER 10.

PAPR in 3rd Generation Partnership Project Long Term Evolution: An Overview to Find the Impact

Third Generation Partnership Project Long Term Evolution (3GPP LTE) has adopted orthogonal frequency division multiple access (OFDMA) as the downlink and single-carrier frequency division multiple access (SC-FDMA) as the uplink for the multiple access scheme. SC-FDMA is adopted in the uplink due to its low peak-to-average-power ratio (PAPR). To reduce the PAPR in OFDMA, several techniques have been used in the literature. Many researches are still going on to find the impact of different parameters on PAPR in SC-FDMA. To further reduce the PAPR in SC-FDMA, techniques used to reduce the PAPR in OFDMA can be a potential choice. In this paper, we investigate some existing papers and find the opportunity to build a platform for further reduction in the PAPR in SC-FDMA environment.

Compact High-Performance Reflector-Antenna Feeds and Feed Networks for Space Applications [Antenna Applications

Reflector antennas are widely used on satellites to communicate with ground stations. They simultaneously transmit and receive RF signals using separate downlink and uplink frequency bands. These antennas require compact and high-performance feed assemblies with small size, low mass, low passive intermodulation (PIM) products [1], low insertion loss, high power handling, and low cross-polar levels. The feeds must also be insensitive to large thermal variations, and must survive the launch environment. In order to achieve these desirable features without prototyping and/or bench tuning, Custom Microwave Inc. (CMI) has combined integrated RF design, precision CAD, and a precision manufacturing technique known as electroforming to closely integrate the various components of a feed or feed network, thereby achieving small size while maintaining high RF performance [2]. In addition to close integration, electroforming eliminates split joints and minimizes flanges by allowing several components to be realized in a single piece, making it the ideal manufacturing technique for ultra-low passive-intermodulation applications. This paper describes the use of precision design CAD tools along with electroforming to realize high-performance feed assemblies for various communication frequency bands for fixed satellite, broadcast satellite, and broadband satellite services.

Millimeter-Wave Wireless Local Area Network Over Multimode Fiber System Demonstration

A radio over fiber system using millimeter-wave for downlink (DL) and intermediate frequency for uplink (UL) transmission, that includes a wireless path and uses multimode fiber (MMF), is investigated by throughput measurements. Live wireless local area network transmissions (IEEE 802.11g, 54 Mbps), are upconverted to 25.2 GHz for the DL by using an optical phase modulator and optical filter millimeter-wave generation approach. Both DL and UL data were successfully transmitted between a mobile unit (MU) and commercial access point (AP), via a remote antenna unit connected to the AP by a 300-m MMF link. The measurements, for the full link using omni-directional antennas at the MUs, demonstrate good signal coverage throughout an office area of 12.8 × 7.2 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and indicate that a coverage area four times this size would be possible if the antenna were placed in the center of a room.