Path Loss Reduction Research Articles

Revisiting Enhanced AIS Detection Range under Anomalous Propagation Conditions

Two clear-air over-the-horizon propagation mechanisms affecting the Automatic Identification System (AIS) detection range are considered. Comparison results are presented between the path loss due to tropospheric ducting and path loss due to tropospheric scattering (troposcatter) for the AIS frequencies. The calculations are based on the well-known parabolic equation approximation to the wave equation, in which a simple troposcatter formula is incorporated. In most studied cases, the ducting ensures a significantly greater reduction in path loss than troposcatter even when the AIS frequencies are not well trapped in the duct. Emphasis is placed on the elevated trapping layers, and some features that may make ducting propagation less favorable in terms of increasing the AIS detection range are discussed.

On-Body NLoS Radio Channel at Millimeter-Wave Frequencies

This article presents an analysis of on-body radio channels at millimeter-wave frequencies and possible solutions to reduce the path loss, particularly, at non-line of sight (NLoS) locations. We have chosen two specific channels around the wrist and waist, and a comprehensive study has been conducted at the frequency of 94 GHz. It is observed that in the presence of textile, a slow wave mode can be excited tangentially near the surface of human body. Clothing and the thin air between the clothing and the human body surface may attribute to the reduction of path loss at NLoS. Our findings show that the presence of different garment materials is linked to the variation of path loss in on-body radio channels. Moreover, we demonstrate numerically that by attaching thin metallic sheet underneath clothing may further reduce the path loss. In our parametric study, a maximum of 15 dB drop occurs in path loss at only 30 cm distance. A robust theoretical model based on the knife edge diffraction (KED) method has been applied to give physical insights of such a unique radio propagation mechanism, that can lead to abundant applications in 5G communications and beyond.

Performance Analysis of Multilayer Coil Based MI Waveguide Communication System

In the non-conventional media like underwater and underground, the Radio Frequency (RF) communication technique does not perform well due to large antenna size requirement and high path loss. In such media, magnetic induction (MI) communication technique is very promising due to small coil size and constant channel behavior. Unlike the RF technique, the communication range in MI technique is relatively less. To enhance this range, a waveguide technique is already brought in practice. This technique employs single layer coils to enhance the performance of MI waveguide. To further enhance the system functioning, in this paper, we investigated the performance of multi-layer coil (MLC) antenna based MI waveguide communication system in terms of transmission range, path loss, bit error rate (BER) and bandwidth. Besides, the system performance is quantitatively evaluated in three different non-conventional media viz., dry soil, fresh water and wet soil. As compared with the single layer counterpart, the MLC system shows a significant improvement in transmission range, BER even in loosely coupled scenarios and shows a corresponding reduction in path loss. However, the bandwidth is observed to be low (< 1 KHz). In this analysis, the eddy current effects and parasitic capacitance are compared for single and multi-layer coils. It is observed that the proposed system performs better in dry soil medium due to less medium conductivity.

Using MetaPrisms for Performance Improvement in Wireless Communications

In this paper, we put forth the idea of metaprism, a passive and non-reconfigurable metasurface acting as a metamirror with frequency-dependent reflecting properties within the bandwidth of the signal. We show that, with an appropriate design of the metaprism, it is possible to control that each data stream in an orthogonal frequency division multiplexing (OFDM) system is reflected in the desired direction by properly assigning subcarriers to users without the need of control channels and dedicated channel state information (CSI) estimation schemes. Furthermore, the metaprism can also be designed so that it focuses the signal towards a specific position depending on the subcarrier, provided that the user is in the near-field region of the metaprism, with consequent path-loss reduction. A critical discussion is also presented about the path-loss reduction obtainable from metaprisms and, more generally, from metasurfaces. The numerical results show that this solution is effective in extending the coverage in areas experiencing severe non line-of-sight (NLOS) channel conditions, thus making it an interesting alternative to reconfigurable metasurfaces when low-cost, no energy consumption, and backward compatibility with existing wireless standards are required.

2 λ switch.

We demonstrate an elastic multi-wavelength selective switch with up to two wavelength switching capability per crosspoint. We fabricated the switch in a silicon photonics foundry and demonstrated a 17 nm tuning range for ring resonators, with a mean path loss of 2.43 dB. This is a 70% reduction in path loss as compared to previous generations, and we demonstrate a high-speed pulse-amplitude-modulation-4 transmission at 111 Gbps through different paths of the switch.

Received Signal Strength Indication (RSSI) of 2.4 GHz and 5 GHz Wireless Local Area Network Systems Projected over Land and Sea for Near-Shore Maritime Robot Operations

The effect of the maritime environment on radio frequency (RF) propagation is not well understood. In this work, we study the propagation of ad hoc 2.4 GHz and 5 GHz wireless local area network systems typically used for near-shore operation of unmanned surface vehicles. In previous work, maritime RF propagation performance is evaluated by collecting RSSI data over water and comparing it against existing propagation models. However, the multivariate effect of the maritime environment on RF propagation means that these single-domain studies cannot distinguish between factors unique to the maritime environment and factors that exist in typical terrestrial RF systems. In this work, we isolate the effect of the maritime environment by collecting RSSI data over land and over seawater at two different frequencies and two different ground station antenna heights with the same physical system in essentially the same location. Results show that our 2.4 GHz, 2 m antenna height system received a 2 to 3 dBm path loss when transitioning from over-land to over-seawater (equivalent to a 25 to 40% reduction in range); but increasing the frequency and antenna height to 5 GHz, 5 m respectively resulted in no meaningful path loss under the same conditions; this reduction in path loss by varying frequency and antenna height has not been demonstrated in previous work. In addition, we studied the change in ground reflectivity coefficient, R , when transitioning from over-land to over-seawater. Results show that R remained relatively constant, −0.49 ≤ R ≤ −0.45, for all of the over-land experiments; however, R demonstrated a frequency dependence during the over-seawater experiments, ranging from −0.39 ≤ R ≤ −0.33 at 2.4 GHz, and −0.51 ≤ R ≤ −0.50 at 5 GHz.

MIMO Interference and Path Loss Reduction using Adaptive Antenna System along with Optimization of Frequency for Zero Path Loss

MIMO Interference and Path Loss Reduction using Adaptive Antenna System along with Optimization of Frequency for Zero Path Loss

Threshold-based energy-efficient routing for transmission of critical physiological parameters in a wireless body area network under emergency scenarios

In current study and design, the technology used in wireless body area networks has revolutionized the future of healthcare systems by remote and personalized monitoring to improve diagnosis and evolution of many pervasive diseases at early stages. In this paper, we proposed an energy-efficient computing technique to transmit the emergency data during critical conditions using bio-sensors and highly advanced nodes. During transmission and communication, energy consumption is minimized by applied threshold values to the sensed data and found the most efficient path using the cost value metric to decrease the energy consumption of the entire network. For optimizing energy constraints and to maintain a balance throughout the network lifetime, a suitable transceiver characteristic is selected and used in the design. Obtained results exhibit an increased stability period, network lifetime, throughput, remaining energy after data communication and a reduction in path loss, propagation delay compared to existing advanced node direct and multi-hop routing techniques.

Particle Swarm Optimization for the Path Loss Reduction in Suburban and Rural Area

In the present work, a precise optimization method is proposed for tuning the parameters of the COST231 model to improve its accuracy in the path loss propagation prediction. The Particle Swarm Optimization is used to tune the model parameters. The predictions of the tuned model are compared with the most popular models. The performance criteria selected for the comparison of various empirical path loss models is the Root Mean Square Error (RMSE). The RMSE between the actual and predicted data are calculated for various path loss models. It turned out that the tuned COST 231 model outperforms the other studied models.

Group handoff management in low power microcell-femtocell network

This paper presents an analytical model of group based hand-off management based on bird flocking behavior. In the proposed scheme, a number of mobile devices form a group if these devices move together for a long time duration. Although call delivery or call generation are performed individually, hand-off is performed in a group. Dynamic group formation, group division and group merging methods are proposed in this paper. From the simulation results it is demonstrated that approximately 75%, 65% and 90% reduction in power, cost and latency consumption can be obtained respectively using group hand-off management. Thus the proposed scheme is referred as green, economic and fast hand-off strategy. In this paper instead of a macrocell network, a microcell-femtocell network is considered as the transmission power of a microcell or a femtocell base station is much less than a macrocell base station. Simulation results present that the microcell-femtocell network achieves approximately 25–55% and 35–55% reduction in power transmission, and 50–65% and 15–45% reduction in path loss than only a macrocell network and macrocell-femtocell network respectively. Thus microcell-femtocell network is a power-efficient network.

A Novel Algorithm to Improve Indoor Localization Accuracy and Path-Loss Reduction Using Real Time RSSI

Distance estimation is vital for localization and many other applications in wireless sensor networks. Research has revealed that the correlation between distance and RSSI (Received Signal Strength Indication) values is the key of ranging and localization technologies in wireless sensor networks (WSNs). Distance measurement based on RSSI (Received Signal Strength Indication) is a low cost and low complexity of the distance measurement technique, and it is widely applied in the range-based localization of the WSN. In this paper, an Log Normal Shadowing Model (LNSM) that estimates the distance between sensor nodes in WSNs is presented. The performance of this model and proposed method are evaluated and analyzed in an indoor environment with and without considering obstacles by performing an empirical measurement using Crossbow TelosB wireless sensor motes. Our result shows that the proposed method reduced distance error and path-loss effectively than LNSM. The results of these evaluations would contribute towards obtaining accurate locations of wireless sensor nodes.

Matching layer for path loss reduction in ultra wideband implant communications.

Real-time monitoring of various physiological signals is of utmost importance for the treatment of chronic conditions. Radio technology can enable real-time sensing and collection of physiological data to facilitate timely medication and early pre-hospital management of patients. This can be realized with the aid of implantable biomedical sensors with the capability to transmit wirelessly the collected information to an external unit for display and analysis. Currently, commercial wireless medical implantable sensors operate in frequencies below 1 GHz with narrowband signals. Recently, it has been demonstrated that ultra wideband (UWB) signals could be also used for the radio interface of these devices. However, establishing an implant communication link in the allocated UWB spectrum of 3.1-10.6 GHz is challenging. The attenuation of UWB signals propagating through biological tissues at these frequencies is high. Part of these path losses are caused by the impedance mismatch between the two propagation environments (i.e., air and biological tissues) that constitute an implant communication link. This mismatch results in inefficient power transmission of the radio waves. In this paper we propose the use of a layer of dielectric material that can be applied on the patient's skin. The permittivity value of this matching layer has to be chosen such that wave coupling is maximized. Through numerical simulations we determined the appropriate permittivity value of a matching layer for UWB implant communication links in the human thorax for 1-6 GHz. Path loss reduction of up to 10 dB can be obtained in this frequency band. These results can help improve the use of UWB signals for other in-body biomedical devices like the wireless capsule endoscope (WCE).

Enhancement of Indoor Localization by Path-Loss Reduction Using Modified RSSI Technique

Localization is one of the most challenging and important issue in wireless sensor networks (WSN), especially if cost effective approaches are demanded. Distance measurement based on RSSI (Received Signal Strength Indication) is a low cost and low complexity of the distance measurement technique, and it is widely applied in the range-based localization of the WSN. The RSS (Received Signal Strength) used to estimate the distance between an unknown node and a number of reference nodes with known co-ordinates. Location of the target node is then determined by trilateration. Log-normal shadowing model can better describe the relationship between the RSSI value and the distance. Due to the Non-line of sight and multipath transmission effects in the indoor environment, the distance error or ranging error will be large. It is a challenging task to optimize the transmission power of WSNs, in presence of path loss, because although increasing the transmission power reduces the residual energy, it also reduces the number of retransmissions required. In this paper, experimental results that are carried out to analyze the sensitivity of RSSI measurements in an indoor environment for various power levels are presented. Along with the reduction in the Distance error through improved RSSI technique, Path-loss also reduced comparatively.

Performances of Amplify-and-Forward Cooperative Relay Networks with Different Topologies

When the sizes of terminals are limited, cooperative relay networks are recommended as promising virtual MIMO systems to improve the performances of wireless communication systems in literature. Accordingly, some comparisons on the performances of different systems are useful to guide the selection and deployment of cooperative relay systems in field applications. In this paper, we compare the outage probabilities of cooperative relay networks of different topologies (different numbers of antennas used at a transmitter and relays used in a system), as well as the outage probabilities of the MISO systems. We propose an aggregated channel mode, which combines the power gain obtained from the reduction of path loss through the deployment of relays, and the flat fading caused by multi-path propagation. During the evaluation of the performances of different systems, we apply information theory in the calculation of ergodic capacities and consider the requirement on wireless resources in the estimation of outage probabilities. Numerical simulation shows that (1) cooperative networks with multiple relays outperform those with multiple antennas; (2) only when the power gain is included, the performances of cooperative relay networks are comparable with their counterparts in direct transmission; (3) the performances are significantly affected by the locations of relays.

A Comparative Analysis of Cell Planning for Path Loss Reduction

A Comparative Analysis of Cell Planning for Path Loss Reduction

Performance of cooperative diversity using Equal Gain Combining (EGC) over Nakagami-m fading channels

Cooperative diversity is a promising technology for future wireless networks. In this paper, we derive exact closed-form expressions for the average bit error rate (BER) and outage probability (Pout) for differential equal gain combining (EGC) in cooperative diversity networks. The considered network uses amplify-and-forward relaying over independent non-identical Nakagami-m fading channels. The performance metrics (BER and Pout) are derived using the moment generating function (MGF) method. Furthermore, we found (in terms of MGF) the SNR moments, the average signal-to-noise ratio (SNR) and amount of fading. Numerical results show that the differential EGC can benefit from the path-loss reduction and outperform the traditional multiple-input single output (MISO) system. Also, numerical results show that the performance of the differential EGC is comparable to the maximum ratio combining (MRC) performance.

무선네트워크에서 적응형 협력통신의 성능 분석에 관한 연구

단일 안테나를 사용하는 사용자들 사이의 협력통신은 무선 매체의 전송 특성이나 경로 손실을 이용하여 안테나의 숫자를 증가하지 않고도 다중 안테나 시스템의 강력한 장점을 얻을 수 있다. 본 논문에서는 ML(Maximum Likelihood) 검파기의 구조를 간단하게 할 뿐만 아니라 에러확률을 최소화 할 수 있는 전송신호 증폭인자의 최적화를 통해 전파환경의 변화에 순응하는 협력통신의 방법에 대해 제안한다. 제안하는 협력통신에 대해 수학적인 해석에 의한 BER(Bit Error Ratio) 표현을 유도할 뿐만 아니라 모의 실험 결과를 통해 그 성능을 비교한다. 다양한 수학적 계산의 결과를 통해 주파수 비선택적 Rayleigh 페이딩 채널에 AWGN(Additive White Gaussian Noise)이 합쳐진 채널 환경에서 실험한 결과 협력통신이 비 협력통신 보다 현저히 성능이 좋음을 알 수 있다. Broadcast nature of wireless medium and path-loss reduction create a favourable condition for collaborative communications (CC) among single-antenna users to gain the powerful benefits of multi-antenna system without the demand for physical arrays. This paper proposes a CC strategy adapting to the propagation environment changes by optimizing the transmit signal amplification factors to simplify the structure of maximum likelihood (ML) detector and to obtain the minimum error probability as well. The closed-form BER expression was also derived and compared to the simulation results to evaluate the performance of the suggested solution. A variety of numerical results revealed the cooperation significantly outperforms non-cooperative counterpart under flat Rayleigh fading channel plus AWGN (Additive White Gaussian Noise).

Path Loss Reduction in an Urban Area by Genetic Algorithms

In this paper, we use the SBR/Image method to compute the path loss for different outdoor environments in the commercial area of Taipei. Four types of antenna arrays such as L shape, Y shape, triangular and circular arrays are used in the base station and their corresponding path loss on several routes in the outdoor environment are calculated. Moreover, the genetic algorithm is employed to optimize the excitation voltages and phases for antenna arrays to form proper antenna patterns. The performance in reduction of path loss by the genetic algorithm is investigated for these antenna arrays. By the obtained antenna patterns, we can know the route with the lowest path loss; meanwhile, transmission power using this route in the base station can be reduced. The investigated results can help telecommunication engineers improve their planning and design of microcellular system.

Effects of antenna height, antenna gain, and pattern downtilting for cellular mobile radio

Results of wideband path loss and delay spread measurements using high gain, high and low antenna heights with pattern tilting are presented. The measurements were done in the frequency range 905-915 MHz, at two existing cellular mobile radio (CMR) sites. Also presented are potential approaches for analyzing data from high gain antennas. It is shown that, to a large extent, existing models can be used to predict path loss for high gain antennas with downtilting. The results further support the notion that high sites together with high gain antennas and suitably selected pattern tilting can result in a significant reduction in path loss and delay spread, as well as reduction in power transmitted from the cell site and reduction in system interference.

X-band transhorizon measurements of CW transmissions over the sea-Part I: path loss, duration of events, and their modelling

This article presents measurements, analysis, and modelling of path loss and duration of events obtained in a transhorizon experiment over the English Channel (La Manche, operated from 1987 to 1991, totalling 3708 valid data days and using five paths with three radiofrequencies at X-band. An overview of the equipment, operation and data acquisition, and processing is first given. The study reveals that the decibel path loss is normally distributed but exhibits three distinct regions of normality: path losses with probability of occurrence greater than about 1% reflect propagation dominated by several propagation mechanism. The second region, which can be clearly identified with probabilities of path loss below about 1%, reflects the various anomalous propagation mechanisms, and these are identified and discussed. The experimental median is compared with the value derived using several prediction methods, one of which is found to agree well with only a few decibels of difference. On the other hand, the existing CCIR prediction for small time percentages under values the strongest enhancements found. The continuous reduction of path loss below a given threshold L (decibels) constitutes an event with some duration. The analysis has shown that the conditional distribution Prob (D'>or=D/L' >