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This paper focuses on the characterization of radio propagation, and data communication in a marine environment. More specifically, we consider signal propagation when three different sub-gigahertz industrial, scientific, and medical (ISM) bands, i.e., 169 MHz, 434 MHz, and 868 MHz, are used. The main focus of the paper is to evaluate the path loss (PL), i.e., the power loss that a propagation radio wave would experience when communication occurs between a sail boat and a buoy. We describe the measurement results obtained performing three different radio power measurement campaigns, at the three different aforementioned ISM sub-gigahertz bands. We also want to correlate the radio propagation quality with the weather conditions present in the measurement areas. The obtained results show that higher distances are achieved by transmitting at lower frequencies, i.e., 169 MHz, and, on average, the propagation is directly dependent from the dew point index. [ABSTRACT FROM AUTHOR]

The demand for wideband data transmission in the "next-generation" mobile communication system is growing rapidly. As the frequency band around 10 GHz could be the option for 6th-generation (6G) wireless communication systems. In this paper, a recently conducted measurement campaign in the 6–14 GHz radio wave propagation channel using a large antenna array with 1024 elements is introduced. In order to investigate the behavior of the wideband channel, we have analyzed the channel characteristics with respect to different carrier frequencies, bandwidths, the locations of antenna elements, and user locations, aiming at exploring the spatio-frequency variability of channels in the massive multiple-input multiple-output (MIMO) scenarios. Moreover, the sparsity of the channel in frequency and spatial domains is evaluated through the degree of freedom (DoF) analysis, and statistical models are established. [ABSTRACT FROM AUTHOR]

A communication blackout is one of the major problems that occurs during the reentry of a satellite into the Earth's atmosphere, which is caused by the reentry plasma blocking electromagnetic waves near the satellite for telecommunication. Moreover, it prevents tracking and data transmission, resulting in inaccurate prediction of landing sites and data loss. Therefore, there is a necessity to evaluate the propagation of electromagnetic waves in the reentry plasma and to mitigate the communication blackout. An inflatable aeroshell technology with lightweight and large-area features enables aerodynamic drag at high altitudes to reduce aerodynamic heating and to mitigate communication blackouts. Thus, a nanosatellite mission using such an inflatable aeroshell has been proposed. For the purpose of telecommunication possibilities during the reentry in future nanosatellite missions, a detailed investigation of communication blackout mitigation by inflatable aeroshell is required. In the present article, the plasma flow and electromagnetic wave propagation near the nanosatellite during atmospheric reentry were revealed by using a computational science approach. A low-temperature and low-density wake is formed behind the nanosatellite. Moreover, an electromagnetic wave propagation path is formed in the wake, indicating that this path is maintained during the reentry, and no communication blackout occurs when using the deployable nanosatellite. [ABSTRACT FROM AUTHOR]

Given the massive rapid growth for capacity in wireless data telecommunications every year, wireless carriers must be planned for a thousand-fold increase in mobile traffic in 2020. It compels scientists to explore for new wireless airwaves that can accommodate large data rates. Next-generation technologies must address issues such as increased spectrum allocation in millimetre wave frequency bands, the installation of directional antennas beam forming antennas, better battery life, high data transmission rates with reduced outage probability, lower capital costs, and increased capacity for multiple simultaneous users. There are two types of telecommunication links: terrestrial and satellite. Terrestrial links are also known as radio relay links. This connects the troposphere, which is located between the earth's surface and the high atmosphere, to the propagation of radio waves. Gases, water vapour, and other weather phenomena such as rain, storms, snow, and hail all interfere with higher frequency radio signals in this region. Due to these difficulties, energy is absorbed and diffused, resulting in signal attenuation. Another form of obstruction generated by radio waves on terrestrial paths is buildings, trees, lampposts, grill, and other urban features. Under these conditions, reflection, diffraction, refraction, scattering, depolarization, and other phenomena are studied. This study discusses the effects of rain on satellite and terrestrial communications. [ABSTRACT FROM AUTHOR]

In the fifth-generation (5G) system, millimeter-wave (mmWave) communication has been recognized as a candidate technique. To overcome the high transmission loss of mmWave, distributed antenna systems that consist of a base station (BS) connecting with multiple remote radio units (RRUs) were studied to improve the energy efficiency. In this letter, by utilizing the propagation characteristics of mmWave, we propose a cooperative multiuser beamforming method for energy-efficient transmissions in mmWave distributed antenna systems. The RRUs first decide the local serving group separately and the BS makes an optimization globally with limited data exchange. From simulation results, compared to the state-of-the-art method, it is shown that higher energy efficiency can be realized by the proposed method for the multiuser mmWave distributed system. [ABSTRACT FROM AUTHOR]

This paper investigates the quality of communication in wireless networks and connection quality evaluation on the basic parameters of indoor and outdoor applications with produced experimental data. The analysis of the influence of radio waves propagation conditions of in the wireless communication networks were performed at the different types of medium. Comparison of the radio waves propagation indoors and outdoors has been done. Also, the effect of the obstacles of various materials on radio propagation was performed. [ABSTRACT FROM AUTHOR]

In this paper a closed form expression for the bit error rate of LDPC-OC system in the presence of interferers is derived over an i.i.d Rayleigh fading channel using message passing algorithm. All interferers are assumed to have equal power. The analysis is done for the case when the number of interferes is more than the number of receive antenna elements. In this paper, analytical results showed that for a BER of 10, the LDPC-OC system provides an additional gain of 6.3 dB over OC system alone. Both the systems provide identical diversity gain of 1.2 dB when the number of receive antennas are increased from 5 to 6. [ABSTRACT FROM AUTHOR]

In an ad hoc cognitive radio network, secondary users access channels temporarily unused by primary users, and the existence of a communication link between two secondary users depends on the transmitting and receiving activities of nearby primary users. Using theories and techniques from continuum percolation and ergodicity, we analytically characterize the connectivity of the secondary network defined in terms of the almost sure finiteness of the multihop delay, and show the occurrence of a phase transition phenomenon while studying the impact of the temporal dynamics of the primary traffic on the connectivity of the secondary network. Specifically, as long as the primary traffic has some temporal dynamics caused by either mobility and/or changes in traffic load and pattern, the connectivity of the secondary network depends solely on its own density and is independent of the primary traffic; otherwise, the connectivity of the secondary network requires putting a density-dependent cap on the primary traffic load. We show that the scaling behavior of the multihop delay depends critically on whether or not the secondary network is instantaneously connected. In particular, we establish the scaling law of the minimum multihop delay with respect to the source–destination distance when the propagation delay is negligible. [ABSTRACT FROM AUTHOR]

This paper presents the large scale parameters of wideband multipath channels based on extensive measurement campaigns in various indoor environments. The measurements were conducted with a wideband multiple-input multiple-output (MIMO) channel sounder having a bandwidth of 400 MHz at 11 GHz which is a challenging frequency for future mobile systems. In particular, polarization characteristics of path-loss, shadowing, cross-polarization power ratio (XPR), delay spread and coherence bandwidth are characterized. The measurement results show that the path-loss exponents range between 2.0 and 3.0 for none-line-of-sight (NLoS), 0.36 and 1.5 for LoS, respectively. Vertically and horizontally polarized transmissions have almost same path-gain, but in some corridor-room NLoS environments, the path-loss for HH is significantly large. In most cases, the RMS delay spreads are less than 20 and 50 ns for NLoS and LoS, respectively, and the average coherence bandwidth is less than 30 MHz. The Rician K-factors range between 2 and 3 dB for cross-polarization, and in large Hall environments, those for co-polarization are greater than 6.0 dB with 10% probability. Finally, some dominant propagation mechanism and site-specific behaviors are illustrated using the double-directional measurement results. [ABSTRACT FROM AUTHOR]

In order to have an effective utilization of the radio wave resources, it is important to estimate propagation path in the urban area. In our previous work, we have examined the diffracted fields by two horizontal edges with an arbitrary angle which are in different and same heights, when a source is located lower than the height of the edges. In this paper, we compare the strength of the direct field, single and double diffracted fields, when the height of the source is varied. Furthermore, the effect of frequency change to the diffracted field is discussed. The numerical calculations are carried out for two wedges and a building-like double-wedge on perfect conductor, concrete and earth wedges. The results show that the higher the source is located, the stronger the diffracted fields become, and the frequency change has not a significant effect to the total field. [ABSTRACT FROM AUTHOR]

The presence of non-line-of-sight (NLOS) propagation is a key issue that limits the accuracy of wireless location systems. The lack of direct sight causes the measurements obtained by location systems to be so unpredictable that they can produce high inaccuracies in the estimation of the mobile station location. In this paper we propose a novel technique to improve location reliability and accuracy in cases where NLOS propagation is present. For that, in registers of time of arrival (TOA) measurements taken from each base station (BS) in view, we detect the presence of NLOS propagation and estimate the ratio of the measurements coming from NLOS propagation. With this estimate we can assess how much is NLOS propagation affecting the measurements taken from each BS and then we can identify the best measurements and BSs to achieve the highest accuracies in location. [ABSTRACT FROM AUTHOR]

Abstract: This article deals with several aspects relative to the MIMO propagation channel. Based on simulations and/or measurements, different approaches are used to model the propagation channel. These models are useful for the MIMO system design. Several studies are performed in order to realize realistic simulation of MIMO channel. Different measurement techniques are used in characterizing the propagation channel in various environments. Measurement campaigns made in different situations have been analyzed to obtain the relevant statistical parameters of the channel. Simulation of MIMO channel is then presented. Measurement and simulation results provide an evaluation of the capacity of MIMO channel. Obtained results show feasibility in the integration of MIMO techniques in practical wireless communication systems. [Copyright &y& Elsevier]

Indoor wireless communications transport the vast information capacity using millimetre wave frequency band. Accurate characterization of the propagation channel is an important requirement for design and implementation of a local area network inside buildings. A tool for prediction of electromagnetic filed strength in indoor communications has been presented. A 3D ray tracing model is developed based on accurate electromagnetic theories that incorporate polarization characteristics. Propagation mechanisms for reflection and transmission are included in the model. The developed software enables prediction of the signal strength at any receiving point of the specific indoor environment. This deterministic model is compared with Motley-Keenan model. The obtained results from both models are compared with measured data. The ray tracing model is used with measured electromagnetic parameters. Non-destructive free space measurement method for the measurement of complex dielectric constant of the walls and other obstacles is used. The accuracy of the model enables the usage of it for characterization of a typical indoor environment for the performance evaluation of wireless local area network. [ABSTRACT FROM AUTHOR]

The propagation characteristics expected to occur in a typical - thus, multipath-reflective - indoor environment are treated analytically. It is shown that the mm-wave indoor radio channel can be considered as a discrete multipath channel that might be highly frequency selective for the high symbol rates of interest (2 Gb/s). Digital transmission over mm-wave channels is discussed, including some performance-improvement methods, and the suitability of some figures-of-merit that are commonly used to quantify transmission performance. [ABSTRACT FROM AUTHOR]

Rain-induced attenuation in the vertically polarised signal propagating at 32.6 GHz over a terrestrial path link of 1.4 km was measured for a period of one year (i.e. from January to December 2006) at Cyberjaya (2°55'N 101°39'E). Different rain attenuation prediction models such as International Radio Communication Union (ITU-R), synthetic storm technique (SST), Moupfouma and Crane Global are compared with the annual statistics of rain attenuation that have been derived from the measured experimental data. It has been observed that the measured values differ from those predicted using ITU-R, and the Crane Global model but follow closely those predicted using SST, Moupfouma and Silva Mello et al. models, resulting in low percentage of RMS errors below 6%. The Moupfouma model was developed for prediction from 0.1 to 0.001% of the time when rain attenuation is exceeded compared to the other models. [ABSTRACT FROM AUTHOR]

Mesh topologies are important for large-scale peer-to-peer systems that use low-power transceivers. The Quality of Service (QoS) in such systems is known to decrease as the scale increases. We present a scalable approach for dissemination that exploits all the shortest paths between a pair of nodes and improves the QoS. Despite the presence of multiple shortest paths in a system, we show that these paths cannot be exploited by spreading the messages over the paths in a simple round-robin manner; nodes along one of these paths will always handle more messages than the nodes along the other paths. We characterize the set of shortest paths between a pair of nodes in regular mesh topologies and derive rules, using this characterization, to effectively spread the messages over all the available paths. These rules ensure that all the nodes that are at the same distance from the source handle roughly the same number of messages. By modeling the multihop propagation in the mesh topology as a multistage queuing network, we present simulation results from a variety of scenarios that include link failures and propagation irregularities to reflect real-world characteristics. Our method achieves improved QoS in all these scenarios. [ABSTRACT FROM AUTHOR]

This article describes the design of a novel circularly polarized H-shaped microstrip-array antenna with a T-slot for dedicated short-range communication (DSRC) system roadside equipment (RSE: 5.850–5.925 GHz). The antenna system needs a correct radiation pattern, at the assigned communication area, without interference from the other radio wave propagation. The proposed antenna is designed to reduce the side lobe level (SLL) by using the proper distance for patch array and multilayer substrates for DSRC RSE. H-shaped patches are used for circular polarization (RHCP or LHCP) with a T-slot. The measured bandwidth of the fabricated antenna is from 5.830 to 5.939 GHz when the return loss < -10 dB. The measured axial ratio (RHCP) is 1.25–2.02 dB and gain is 15.62–15.94 dBi. The experimental 3-dB beam width (HPBW) in the E-plane and H-plane are 22.52° and 24.11° at 5.91 GHz, respectively. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 1545–1548, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24369 [ABSTRACT FROM AUTHOR]

Uncompressed high-definition video streaming over wireless personal area networks is a challenging problem because of the high data rate requirement and channel variations. With the advances in RF technology and the huge bandwidth available worldwide in the 57-66 GHz millimeter-wave unlicensed spectrum, mmWave WPANs that can support multigigabit transmission are being developed. However, compared to low-frequency signals (2.4 or 5 GHz), mmWave signals are more fragile; indeed, the propagation losses are significantly higher. In this article we present an mmWave system for supporting uncompressed HD video up to 3 Gb/s. The system includes various efficient error protection and concealment schemes that exploit unequal error resilience properties of uncompressed video. Some of them have been adopted in the emerging 60 GHz WPAN standards such as WirelessHD, ECMA TC48, and IEEE 802.15.3c. Simulations using real uncompressed HD images indicate that the proposed mmWave system can maintain, under poor channel conditions, good average peak-signal-to-noise-ratio and low video quality metric scores. [ABSTRACT FROM AUTHOR]

Different channel sounders are reported in the literature to measure the multiple-input-multiple-output (MIMO) wireless channel, most of them being dedicated systems. In this paper, a MIMO channel sounder that is based on two network analyzers is presented. The measurement process is totally controlled by a PC via a wireless local area network (WLAN), a local area network (LAN), and a general-purpose interface bus, and they are synchronized by using two Global Positioning Systems (GPSs). The system is restricted to static propagation environments. An advantage of this system is its configurability, thanks to which it is not wireless system dependent. Last, initial measurements in a laboratory of a university at 900 MHz for a 4 × 4 MIMO system are also presented. [ABSTRACT FROM AUTHOR]

High-rate streaming in WSN is required for future applications to provide high-quality information of battlefield hot spots. Although recent advances have enabled large-scale WSN to be deployed supported by high-bandwidth backbone network for high-rate streaming, the WSN remains the bottleneck due to the low-rate radios used and the effects of wireless interferences. First, we propose a technique to evaluate the quality of a path set for multipath load balancing, taking into consideration the effects of wireless interferences and that nodes may interfere beyond communication ranges. Second, we propose an Interference-Minimized Multipath Routing (I2MR) protocol that increases throughput by discovering zone-disjoint paths for load balancing, requiring minimal localization support. Third, we propose a congestion control scheme that further increases throughput by loading the paths for load balancing at the highest possible rate supportable. Finally, we validate the path-set evaluation technique and also evaluate the I2MR protocol and congestion control scheme by comparing with AODV protocol and Node-Disjoint Multipath Routing (NDMR) protocol. Simulation results show that I2MR with congestion control achieves on average 230 percent and 150 percent gains in throughput over AODV and NDMR, respectively, and consumes comparable or at most 24 percent more energy than AODV but up to 60 percent less energy than NDMR. [ABSTRACT FROM AUTHOR]

The propagation characteristics of double-layer SIW structures have been investigated in this paper. On the basis of the theory of resonance cavity and SIW, the simple theoretical formulas for the lower and upper frequencies in the passband have been found. The theoretical analyses have indicated that these two frequencies have much dependence on the width of SIW and the length of the coupling slot, the fractional bandwidth of the double-layer SIW structures can be controllable. Agreement between the simulation data and the calculated results from the formulas can be observed. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 1459–1463, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22469 [ABSTRACT FROM AUTHOR]

A simplified analytical model is presented to predict the specific attenuation for propagation through a tree canopy in a residential environment for frequencies of up to 2 GHz. In this approach, the canopy of a tree is modeled as an ensemble of leaves and branches all having prescribed location and orientation statistics. The Foldy-Lax discrete scattering theory is used to find the specific attenuation of a tree associated with the mean field. Explicit formulas are presented to calculate the specific attenuation of a tree canopy. It is shown that the specific attenuation of a tree canopy depends on the frequency, polarization, electrical and geometrical characteristics of branches and leaves, biophysical parameters of a tree, and statistical distribution of branches and leaves in reference to the angle of incidence of the plane wave. It is also shown that for deciduous trees, as opposed to coniferous trees, the inclination angle distribution of the branches is more vertical, producing a higher specific attenuation for the vertical-polarization incident wave than for the horizontal-polarization incident wave. [ABSTRACT FROM AUTHOR]

This paper concerns the measurement-based comparison of urban microcellular mobile radio channel characteristics at 1.9 GHz and a higher frequency, i.e., 5.8 GHz, where future wireless systems could operate. Characteristics that are reported include transmission loss, root-mean-square delay spread, frequency correlation, and envelope fading statistics. Conclusions are drawn concerning whether significant differences in the performance of mobile radio links operating under the same signal-to-noise ratio conditions in the two bands would be expected in the area where the measurements were made. [ABSTRACT FROM AUTHOR]

This article analyzes the wireless coverage problem of remote regions with low user density and propagation problems due to irregular terrain and high tree density. The use of a wireless mesh network is proposed as a solution where user data is transmitted directly to a base station when it is possible or relayed through other nodes in a multi-hop manner when there is not a direct link. The mesh topology uses short links with higher capacity instead of long links with low capacity. We analyze radio propagation and MAC protocols, including random sources, queues, and packet delays. The article is based on the coverage of a realistic rural region near Medellin, a mid size city in Colombia, and it shows that a wireless mesh network is an alternative to a typical cell based solution. It includes propagation analysis and MAC protocol behavior, so it is not limited to a radio coverage problem but also traffic, scheduling, and routing analysis. [ABSTRACT FROM AUTHOR]

We consider a coded multiple-input multiple-output (MIMO) DS-CDMA system using layered space-time transmission in multipath wireless channels, where space-time signals from multiple antennas of multiple users propagate through rich scattering multipath fading. We propose a receiver employing iterative joint detection and decoding with a reduced-complexity detector using linear minimum mean squared error filtering with a priori information and parallel soft-input soft-output (SISO) decoders. Computer simulation results show that the proposed receiver for multi-user MIMO transmission provides high-spectral efficiency and performance approaching to single-user bound. Furthermore, the reduced-complexity receiver outperforms an iterative soft decision-directed maximal ratio combining (DD-MRC) receiver, RAKE receiver as well as a conventional non-iterative receiver. [ABSTRACT FROM AUTHOR]

The paper investigates the use of differential modulation techniques to achieve high rate data transmission by near vertical incidence sky wave high frequency propagation, using a 2.7 kHz voice channel bandwidth. Channel characteristics have been measured for a range of frequencies between 2.8 and 9.4 MHz, using a transmitter power of 100 W over a distance of 160 km. These measurements are used to characterise simulated channel conditions, and the simulator is then used to determine the performances of differential modulation methods. In particular, time-differential amplitude and phase shift keying and frequency-differential amplitude and phase shift keying modulation methods are investigated. Symbol error rates are presented for data rates ranging from 4.3 to 20.6 kbit/s, where the system performances are limited by time-varying channel dispersion rather than by additive noise. [ABSTRACT FROM AUTHOR]

This paper considers multiple beamforming in the transmitter and receiver in MIMO channels and discusses the weight control procedure. The first half of the paper describes the transmitter and receiver weight conditions for realizing large capacity, for the cases with and without interference signals from other users. The second half proposes a weight control method which can realize high capacity in a real environment. In the proposed system, the control signal is exchanged between the transmitter and the receiver and the transmitter and receiver weights are determined. Using the proposed method, a satisfactory transmission weight can be determined even if the transmitter does not know the propagation information. As a result of simulation, we see that the proposed method is less affected by the propagation path and can assure stable throughput. We also find that the proposed method can achieve high throughput even if a control error occurs. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 88(6): 55–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.20145 [ABSTRACT FROM AUTHOR]

Reports on the principles that exploit electromagnetic induction during data transmission. Role of near field communications in transforming the technology of short range data transmission and position sensing; Promotion of a novel close-range wireless technology where waves do not have to propagate to be useful; Indications showing that near field are also proving useful for communicating with body implants and even for making wireless control knobs.

The implementation of wireless local area networks (WLANs) inside buildings is growing rapidly. It is important to predict the indoor coverage zone. The propagation-prediction models proposed in recent years have paid attention to the effects of propagation and reflection. But in a small room with metallic furniture, diffraction is the main influence upon path loss. Propagation loss and the diffraction loss are considered in the propagation-prediction model that we propose in this paper. The simulation and measurement results are obtained in order to verify the feasibility of this model. The mean error between the measurement and simulation results is within 2 dB. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 44: 281–284, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20611 [ABSTRACT FROM AUTHOR]

This paper presents an experimental analysis of the use of wireless data-transmission systems in manned space platforms. Previous studies have analyzed the general advantages of substituting radio systems for some of the harnesses in the platforms. This paper presents a detailed experimental characterization of the radio channel in the environment of a space platform at frequency bands of 2.5 GHz and 17 GHz. For this purpose, a mockup, based on the Columbus Space Laboratory, was built. The probability distribution functions of the fading have been obtained for narrow-band as well as wideband parameters, such as the mean square delay and the coherence bandwidth of the channel. Moreover, a study of the operating mode of a commercial wireless system, based on the IEEE 802.11b standard, has been performed, by monitoring the bit-error rate. The error rates of the IEEE 802.11b system in the typical environment of a small or medium-sized office are compared with those of a space-platform environment. The results and conclusions can be extended to other environments that present geometrical and structural characteristics similar to those of a space platform, such as ships and submarines. [ABSTRACT FROM AUTHOR]

The variation of the refractivity profiles of the troposphere and especially of the ducting effect, affects the radio wave propagation causing various phenomena such as refraction, fading and interference between radio-stations. In this work, the tropospheric ducting phenomena over the Hellenic region are studied using data from Helleniko and Thessaloniki Airports for the time period from 1991 to 1999. The data are analysed, corrected and enhanced using interpolation techniques and after a final statistical process the ducting conditions over the Hellenic region are summarized. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Deals with a study which measured the capacity of multiple-input multiple-output radio systems in microcellular environments. Measurement setup; Capacity computation; Results; Conclusion.

To obtain a matching over a wide frequency range, pyramid-type and wedge-type matching layers are used in front of the multilayered wave absorbers. In this paper, a transmission mode approximation is proposed in which the period of the wedges and the incident polarization direction are taken into account in the calculation of the characteristics of a wedge-type wave absorber. The degree of difference of the equivalent permittivity derived by the propagation mode approximation from the one by the conventional method (corresponding to the low-frequency limit) is presented by numerical calculations. It is also shown that there is a difference from the wave absorber characteristics derived by the conventional method even at a wavelength longer than the wedge period. The tendency of the reflection to increase at the higher frequency side is visually explained by replacing it with the taper shape. [ABSTRACT FROM AUTHOR]

To understand the propagation structure of the microcells with a tall and medium-height antenna in an urban area, the fundamental propagation parameters are found and the structural model of the propagation loss was constructed. The fundamental propagation parameters were obtained based on the multivariable analysis of the propagation data at 800 MHz measured m the Tokyo Metropolitan area. These parameters are the distance between the transmitter and receiver, the average building height between the transmitter and receiver, and the base-station height which have high correlation and regression coefficients with the propagation loss. The relationship of parameters obtained from the model is (20 - α) log(h) for the base-station height characteristics and (α - 20) log (H) for the building height characteristics if the distance characteristics are α log (d). The relationships of coefficients of the conventional estimation equation and the regression equation obtained by the measured data almost agreed with those of the model so that the validity of the model was confirmed. [ABSTRACT FROM AUTHOR]

A case exists in which cancellation of interference is not possible with an interference canceler which cancels the interference wave from ground radio stations mixing into the ground station for the satellite communication. It is found experimentally that this is caused by the difference in the frequency characteristics of the input signals to the two antennas by the multipath effects. Further, a method is proposed to discriminate whether the arriving interferences can be cancelled. Its effectiveness is confirmed experimentally. Whether or riot the interferences can be cancelled can be determined by the amount of variation of the received electric field intensity of the interferences. If there is a signal with a constant-shaped spectrum, the distortion of the shape can be used for discrimination. As a result, the condition and limit of applications of the interference canceler are found. [ABSTRACT FROM AUTHOR]

Satellite communication has the following problems. The propagation delay is larger than in the terrestrial channel. When the carrier frequency exceeds 10 GHz, the bit-error rate tends to increase due to the effect of rain and snow, which degrades the transmission efficiency. To cope with such problems, a highly efficient error control protocol has been proposed to prevent the degradation of the transmission efficiency. This paper describes a new large- capacity, highly efficient retransmission scheme for satellite communication (extended SREJ scheme), which was devised considering the compatibility to the terrestrial network. The method is based on the SREJ (selective reject) scheme, which is specified in the HDLC (high-level data link control) protocol, employed widely in terrestrial data transmission. To evaluate quantitatively REJ, SREJ and extended SREJ schemes, a satellite communication control equipment was developed. The result of the data transmission experiment is described in detail, indicating that the extended SREJ scheme is efficient. Then, through the discussion of practical usefulness, it is shown that the extended SREJ scheme has no problem from the viewpoint of the number of buffers in transmitting and receiving stations. Further- more, to realize the efficient processing as far as possible, even if the bit-error rate is higher than 1.0 × 10-4, the extended SREJ/REJ scheme is discussed by combining the proposed scheme with the REJ scheme. [ABSTRACT FROM AUTHOR]

The performances (throughput and transmission delay) of the Co-back-N ARQ scheme are affected greatly by the bit error rate of the link and the round-trip propagation delay. This paper discusses the transmission delay of the tandem Co-back-N scheme, in which the round-trip propagation delay can substantially be reduced. First, the generating function for the transmission delay distribution is derived, and then the result is applied to derive the average transmission delay. As a result, it is shown clearly that the performance of the tandem Co-back-N ARQ scheme is better than that of the standard Co-back-N ARQ scheme. [ABSTRACT FROM AUTHOR]

This paper presents an analysis method for the maximum throughput of the window controlled data link under the effect of the propagation delays. The data link is divided into two submodels, and each stochastic process is analyzed independently and the results are integrated. The Calculation by this method is simpler than that by the direct analysis, and highly, accurate evaluation can be made for comparatively general frame length distribution. It is shown that this approach provides very good approximation, especially for the throughput efficiency ranging from 0.7 to 1.0. The region satisfying certain thoughtput value is derived and effective way of selecting the value of window size is presented. [ABSTRACT FROM AUTHOR]

A switchable Yagi-Uda antenna prototype with radiation pattern reconfiguration is presented in this letter. The proposed reconfigurable antenna is based on the concept of switching between the reflector and director of a Yagi-Uda antenna using a radio frequency PIN diode. As a result, the minimum/maximum radiation can be steered towards desired signals or away from interfering signals in opposite directions. The measured 10 dB impedance bandwidth and gain are 210 MHz (7%) and 8.02 dBi at 3 GHz, respectively. Details of the antenna design and its performance are described and empirically analyzed. [ABSTRACT FROM AUTHOR]

Joint source-channel coding (JSCC) involves the use of a single coding scheme in order to encode data from a redundant information source (source coding/data compression) for reliable transmission over a noisy channel (channel coding/error correction). JSCC can be attractive in the non-asymptotic regime, where the residual redundancy of the source sequence can be used by the channel decoder to improve channel decoding. In this work, a method for JSCC based on concatenated spatially coupled low-density parity-check (SC-LDPC) codes is investigated. A construction consisting of two SC-LDPC codes is proposed: one for source coding and the other for channel coding, with a joint belief propagation-based iterative message passing decoder. Using a windowed version of the decoder, simulation results show a notable performance improvement compared to existing state-of-the-art JSCC schemes based on LDPC codes for approximately equal latency and complexity requirements. [ABSTRACT FROM AUTHOR]