Alain Azoulay

Survey on the Future Aeronautical Communication System and Its Development for Continental Communications

We present in this survey new technologies proposed for the evolution of the aeronautical communication infrastructure. Motivated by studies that estimate the growth of air traffic flow, it was decided to develop a future communication infrastructure (FCI) adapted to the future aeronautical scenario. The FCI development involves researchers, industrials, and aeronautical authorities from many countries around the world, and started in 2004. The L-band Digital Aeronautical Communication System (L-DACS) is the part of the FCI that will be in charge of continental communication. The L-DACS is being developed in Europe since 2007 and two candidates were preselected: L-DACS1 and L-DACS2. In this paper, we first describe the motivations of the FCI. We then give an overview of its development activities from 2004 to 2009. After that, we provide some insights about both preselected L-DACS candidates, at their physical and medium access layers. Finally, we address the challenges on the development of the FCI/L-DACS.

On the Statistics of Reverberation Chambers and Applications for Wireless Antenna Test

In this paper, statistical tools were applied to clarify the Rayleigh distribution of the fading signals in a reverberation chamber. Autocorrelation and cross-correlation functions, AFD and LCR are measured. The signals correlation coefficient versus spatial locations is assessed. With the above considered reverberation chamber, measurements reveal a good agreement for emulating mobile fading channels. The measurement procedure described in this paper can be used to verify the performance of any chamber for wireless characterizations

A dual band back coupled meanderline antenna for wireless LAN applications

We present a novel dual band printed meander line antenna with a shaped ground plane and a back coupled rectangular patch. The aim was to achieve 2 GHz and 5 GHz covering the two main frequency bands of commercially available WLANs. To obtain a dual band with wide bandwidth operation, a meander line microstrip printed antenna with a matched feed and a shaped ground plane was first designed at 2.45 GHz. Then, a rectangular patch was added at the back of the meandered antenna substrate, with a small gap between the rectangular patch and the shaped ground plane. Changing the length of the rectangular patch allows the resonance frequency to be tuned, for instance 5.25 GHz. In fact, the resonance frequency can be continuously adjusted between 5.2 GHz and 7 GHz by changing the rectangular patch length. Furthermore, the tuning of the second resonance frequency has very little effect on the first one. The obtained bandwidth is 11% at 2.45 GHz and 6% at the second frequency for a return loss less than -10 dB. Consequently, this antenna offers sufficient flexibility for all types of wireless local area networks in the available frequency bands. This small antenna structure (31/spl times/8/spl times/1.6 mm/sup 3/) and its achievable low price with an SMA type connector, make it appropriate for Notebook, PC, PDA and other commercial WLAN communications applications.

Diversity Techniques with Dipole Antennas in Indoor Multipath Propagation

In this paper, we investigate the correlation coefficient and the diversity gains of two parallel dipole antennas in various configurations. The correlation coefficient in an indoor environment is first computed from the 3D farfield radiation patterns of each antenna; then, it is measured inside a mode stirred reverberation chamber used as a model of indoor multipath. The diversity gains for switch combining and maximum ratio combining versus the dipole separation are derived from the measurements. Depending on the dipoles separation, three types of diversity techniques are defined: space, pattern and phase diversity. At large distances, the correlation coefficient is highly controlled by the space factor, but when the antennas are approached (up to 0.05 wavelength), phase diversity is the most dominant factor which greatly reduces the correlation coefficient and allows an efficient diversity

Electromagnetic environment of RFID systems

In this paper, the influence of the electromagnetic environment on RFID (radio frequency identification) systems is studied. By electromagnetic environment, we consider the electromagnetic waves interference on a RFID system performance produced by applications located nearby. In particular, we analyze the effects of using a GSM mobile phone near an UHF-868 MHz RFID system. For the tested configurations, the results show that the read range (the maximum distance of labels detection) of the RFID is considerably reduced. Also, the GSM mobile communication can be affected by the waves radiated by the RFID system.

A Pattern Diversity Antenna with Parasitic Switching Elements for Wireless LAN Communications

In this paper, a pattern diversity antenna with switched parasitic elements is presented for wireless LAN application. A wire meander-line antenna on top of a circular metallic ground plane is designed and used as the main radiator. Some conductive rods are installed on the ground plane, around the antenna. Connecting and disconnecting of the rods to the ground plane stirrers the antenna farfield radiation pattern. Two optimized switching categories are used in rods selection. A good impedance matching and low correlated radiation patterns are generated which results to an efficient diversity antenna system. The diversity signals correlation, in a uniform field scattering environment and Rayleigh multipath fading channel, is computed from the complex 3D radiation patterns. It is verified with the measurements accomplished inside a mode stirrer reverberation chamber (MSRC). The received signals correlation coefficient and the diversity gain for selection combining are provided

Interference analysis for the future aeronautical communication system

General and commercial aviation authorities have been using amplitude modulation communication systems for more than 70 years. Due to the great increase of air traffic during the last years, the VHF band tends towards saturation, whereas the aeronautical community faces new requirements: data rate, spectral efficiency and network capacity (maximum number of aircrafts simultaneously connected). Recently, the development of a new digital aeronautical communication system, named L-DACS, was proposed. This system will operate in the L band part allocated to aeronautics. There were many proposals but only two candidates have been pre-selected by the ITU and ICAO for this future communication system: L-DACS1 and L-DACS2. The deployment of this new system is expected to start after 2020. Among other issues, one important aspect is the impact of L-DACS on legacy systems. Actually, there are many onboard systems operating in L band, and any disfunction can put in danger the flight safety. This paper studies the maximum interference level generated by the two L-DACS candidates on a generic onboard receiver. Taking into account the antenna radiation pattern and the specific transmission mask of both candidates, the study determines the worst interference level and the corresponding spatial positions of the aircrafts around the receiver. The results show that the interference level can be determined by considering the several nearest aircrafts to the victim.

Effect of the Aeronautical L-DACS2 Radio-Frequency Signals on the DME System Performance

In this paper, we consider the Radio-Frequency Compatibility (RFC) of a candidate system for the future aeronautical communication infrastructure. This infrastructure is being developed within the International Civil Aviation Organization since 2004, to accommodate the air traffic load and improve the aerial security. The system presented in this paper is one of the two preselected proposals for the L-band Digital Aeronautical Communication System (L-DACS), which will be responsible for the continental communications. This proposed candidate is named L-DACS2 and is foreseen to use part of the L-band spectrum (960 to 1164 MHz) allocated to the Aeronautical Mobile Service reserved for communications relating to safety and regularity of flight. Despite its potentially large spectrum, the L-band is a challenging environment for aeronautical communications because of the channel propagation characteristics and the dense spectral occupation by a large number of aeronautical systems. On the other hand, the RFC characterizes the electromagnetic compatibility between two radio systems and determines if they can coexist in the same electromagnetic environment. For this reason, the RFC is one of the main issues for L-DACS deployment and if it is not satisfied, the flight safety could be endangered. Hence, we propose to study in this paper the impact of the L-DACS on the Distance Measuring Equipment (DME), which is a very important equipment that has been using this band for decades. According to recent studies performed in the frequency domain , that is assuming continuous transmissions and no time domain variations, the achieved RFC level seems insufficient. The main objective of this work is to analyze the RFC between L-DACS2 and DME taking into account the time domain aspects of both systems. The idea is to verify and quantify the impact of the radio- frequency signals generated by a L-DACS2 interferer on the performance of a DME victim receiver. The study is performed for the co-site case (\emph{i.e.} when both equipments are onboard of the same airplane), which is the most critical interference scenario due to the proximity of both systems. The results are obtained through computer simulations as well as laboratory measurements. They present the DME performance degradation for some values of the Signal to Interference Ratio, assuming a constant DME signal level and different L-DACS2 interference powers.

Study of a 5.8 GHz frequency band patch antenna integrated into a vehicle for automotive DSRC applications

This paper presents a simulation study of a 5.8 GHz patch antenna integrated into a vehicle for Dedicated Short Range Communication applications (DSRC). The DSRC deals with car-to-car and car-to-infrastructure communications and will permit to improve road transport by using information and communication technologies. This study provides simulation results validated by measurements that enable to assess the effects of car structures on radiation patterns.

Radioelectric compatibility of the future aeronautical communication system

The aeronautical community has recently decided to develop a new digital aeronautical communication system, named L-DACS, in order to fulfill the new air traffic requirements. This system, which will operate in the L frequency band (960 to 1164 MHz), would be internationally deployed from 2020. Many technologies were considered for this new aeronautical system but only two among them were preselected by the International Civil Aviation Organization (ICAO): candidate one, named L-DACS1, is based on a FDD-OFDM technology and candidate two, named L-DACS2, is based on a TDD-GMSK technology. One of the most important issues for both candidates is the electromagnetic compatibility (EMC) with the legacy systems operating in the same band or/and in adjacent bands. Different scenarios have to be evaluated due to the fact that these systems will be implanted either in the airplanes (on board) or in ground stations. In this paper, we propose to evaluate the air-air scenario, where we focus on the signals generated by onboard L-DACS transmitters on onboard victim receivers, taking into account the L-DACS antenna radiation pattern and the frequency mask. The study emphasizes that the interference phenomenon can be one of the main limitations for the L-DACS development.