For high transmission efficiency, good modulation schemes are expected. This paper focuses on the enhancement of the modulation scheme of free space optical turbo coded system. A free space optical turbo coded system using a new signaling scheme called hybrid PPM-OOK signaling (HPOS) is proposed and investigated. The theoretical formula of the bit error rate of the uncoded HPOS system is derived. The effective information rate performances (i.e. channel capacity) of the proposed HPOS turbo coded system are evaluated through computer simulation in free space optical channel, with weak, moderate, strong scintillation. The performance of the proposed HPOS turbo coded system is compared with those of the conventional OOK (On-Off Keying) turbo coded system and BPPM (Binary Pulse Position Modulation) turbo coded system. As results, the proposed HPOS turbo coded system shows the same tolerance capability to background noise and atmospheric turbulence as the conventional BPPM turbo coded system, and it has 1.5 times larger capacity.

The purpose of this study was to examine an efficient interval encoding method with a slow-frame-rate image sensor, and show that the encoding can work to capture heart rates from multiple persons. Visible light communication (VLC) with an image sensor is a powerful method for obtaining data from sensors distributed in the field with their positional information. However, the capturing speed of the camera is usually not fast enough to transfer interval information like the heart rate. To overcome this problem, we have developed an event timing (ET) encoding method. In ET encoding, sensor units detect the occurrence of heart beat event and send their timing through a sequence of flashing lights. The first flash signal provides the rough timing and subsequent signals give the precise timing. Our theoretical analysis shows that in most cases the ET encoding method performs better than simple encoding methods. Heart rate transfer from multiple persons was examined as an example of the method's capabilities. In the experimental setup, the developed system successfully monitored heart rates from several participants.

A broadband approach to estimate the relative permittivity of dielectric cuboids has been proposed for materials of weak frequency dispersive characteristic. Our method involves a numerical iterative scheme with appropriate initial values carefully selected to solve for the relative permittivity in a wide range of frequencies. Good agreements between our method and references have been observed for nylon and acrylic samples. An applicable range relation between the minimal thickness, the frequency range and the dielectric property of the material has also been discussed.

Increasing demand in data-traffic has been addressed over the last few years. It is expected that the data-traffic will present the significant part of the total backbone traffic. Accordingly, much more transmission systems will be required to support this growth. A free space optic (FSO) communication is the greatest promising technology supporting high-speed and high-capacity transport networks. It can support multi Gbit/s for few kilometers transmission distance. The benefits of an FSO system are widespread, low cost, flexibility, immunity to electromagnetic field, fast deployment, security, etc. However, it suffers from some drawbacks, which limit the deployment of FSO links. The main drawback in FSO is the degradation in the signal quality because of atmospheric channel impairments. In addition, it is high sensitive for illumination noise coming from external sources such as sun and lighting systems. It is more benefit that FSO and mmWave are operating as a complementary solution that is known as hybrid FSO/mmWave links. Whereas the mmWave is susceptible to heavy rain conditions and oxygen absorption, while fog has no particular effect. This paper will help to better understand the FSO and mmWave technologies and applications operating under various atmospheric conditions. Furthermore, in order to improve the system performance and availability, several modulation schemes will be discussed. In addition to, the hybrid FSO/mmWave with different diversity combining techniques are presented.

Satellite clusters have been satisfactorily implemented in a number of applications, such as positioning and sensor networks, with the purpose of improving communication system capabilities. However, because the use of clusters requires good management of the resources, those solutions imply new challenges for communication systems. This paper focuses on improving the data management between network elements by considering a network formed by satellite clusters. Satellite clusters work in cooperation to provide real-time and non-real-time services in different footprint areas. This study proposes the adjustable energy consumption access scheme (AECS) as one possible solution response to particular necessities of communication and at the same time, as a way of decreasing the system energy consumption. Energy consumption is a key issue that concerns green network operations and it is directly linked to the cooperation and coordination between network elements. On the other hand, we support the implementation of Optical Inter-Satellite Links (OISL) for communication between cluster elements. The analysis involves the study of energy consumption, transmission delay, specific link margins, bit error rate (BER) and QoS.

In this paper, we propose a high-speed full-duplex optical wireless communication system using a single channel imaging receiver for personal area network applications. This receiver is composed of an imaging lens, a small sensitive-area photodiode, and a 2-aixs actuator and it can reject most of the background light. Compared with the previously proposed system with single wide field-of-view (FOV) non-imaging receiver, the coverage area at 12.5 Gb/s is extended by > 20%. Furthermore, since the rough location information of the user is available in our proposed system, instead of searching for the focused light spot over a large area on the focal plane of the lens, only a small possible area needs to be scanned. In addition, by pre-setting a proper comparison threshold when searching for the focused light spot, the time needed for searching can be further reduced. Proof-of-concept experiments have been carried out and the results show that with this partial searching algorithm and pre-set threshold, better performance is achieved.

In order to detect snow and ice on a road surface, the microwave measurement method of dielectric constants are presented. And some examples of measurements for artificial and natural snow and ice using the method are introduced. The results show reasonable estimations of the dielectric constants, and they indicate that the method could be utilized for the snow and ice detection.

With the increase of communication demand and the emergence of new services, various innovative wireless technologies have been deployed recently. Free Space Optics (FSO) links combined with Radio over Fiber (RoF) technology can realize a cost-effective heterogeneous wireless access system for both urban and rural areas. In this paper, we introduce a newly developed advanced DWDM Radio-on-FSO (RoFSO) system capable of simultaneously transmitting multiple Radio Frequency (RF) signals carrying various wireless services including W-CDMA, WLAN IEEE802.11g and ISDB-T signals over FSO link. We present an experimental performance evaluation of transmitting RF signals using the RoFSO system over a 1 km link under different deployment environment conditions. This work represents a pioneering attempt, based on a realistic operational scenario, aiming at demonstrating the RoFSO system can be conveniently used as a reliable alternative broadband wireless technology for complementing optical fiber networks in areas where the deployment of optical fiber is not feasible.

Point-to-point optical and millimeter wave communication has recently been of interest, especially in urban areas. Its benefits include simpler and easier installation compared with a land-based line. However, this technology suffers when adverse weather conditions are present, such as rain, fog and clouds, which induce scattering and absorption of the optical wave. The effects of scattering and absorption degrade the quality of the communication link resulting in increase of bit-error-rate. Therefore, there exists a need for accurate channel characterization in order to understand and mitigate the problem. In this paper, radiative transfer theory is employed to study the behavior of amplitude modulated signal propagating through a random medium. We show the effect of the medium to a modulated signal and relate the outcome on the quality of the communication link.

This paper presents a view on coming photonic network in which machines are potential customer to the network. The network will be providing unlimited number of virtual free spaces in which point to point and broadcasting modes of information interchanges are taking place simultaneously. It is also pointed out that the Asynchronous Transfer Mode (ATM) should be evolved to support this type of network by using true photonic switching technology.