Sathyanarayanan Chandrasekharan

Path loss study for millimeter wave device-to-device communications in urban environment

In the recent years the millimeter wave spectrum is being explored as a prospective band for the next generation (5G) cellular communications. In this paper we study the propagation of the the millimetre wave spectrum using ray tracing model for an urban environment. We consider the ISM bands in 24GHz and 61GHz in particular and conduct ray tracing simulations to study the path loss behaviour in terms of the path loss exponent and the shadowing variance for both Line of Sight and Non Line of Sight conditions. As a potential application we examine the device to device (D2D) communication, which is currently being developed for LTE-A standard. The resulting pathloss exponents and the shadow variances are presented here based on ray tracing simulations for an ITU-R statistical urban model, moreover this paper shows that intelligent beam steering can significantly improve the throughput for the considered D2D scenarios.

Clustering approach for aerial base-station access with terrestrial cooperation

In this paper we propose a clustering mechanism for improved energy efficiency in aerial based access systems suitable for disaster recovery scenarios and large scale public events. The aerial base station is a low altitude platform (LAP) station that provides access to several terrestrial nodes on the ground over a prescribed coverage area. The terrestrial nodes are battery operated power constrained terminals that have got no base station access except for the LAP. Since the aerial uplink is a high cost energy link we propose a cluster based approach for LAP access. The proposed clustering mechanism is simulated and is compared with the well known clustering technique HEED for energy efficiency. Results show that the proposed clustering technique improves the energy efficiency compared to the non-clustering situation as well as to the HEED clustering technique.

Coverage and rate analysis of aerial base stations

In this paper, we investigate the achievable coverage and the information rate of an aerial base station. The air-to-ground link is analysed by considering random fading and shadowing effects impairing the wireless transmission, together with a homogeneous spatial distribution of the terrestrial users. The distribution of the buildings in the underlying coverage region is modeled using the International Telecommunication Union-Recommendation statistical city model. For a given urban environment/region, we analytically quantify the achievable coverage probability and the information rate of users on the ground at a particular base station altitude. Furthermore, we analytically find the optimal altitude of the aerial base station to maximise the terrestrial coverage given a certain service region. Simulations are conducted to verify our analysis, and a close match between the analytical and simulation results is observed.

Spectrum occupancy measurements for different urban environments

In this paper we present the results of spectrum occupancy measurements conducted in different urban environments, in greater Melbourne area, Australia. We capture the dynamic nature of spectrum occupancy seen from a spatial perspective, by conducting spectrum monitoring measurements on board a mobile vehicle. With a wide spectrum window selected from 400 to 6000 MHz we aim to shed some light on the feasibility of utilizing smart spectrum access techniques facilitated by cognitive radios.

Propagation measurements for D2D in rural areas

Device-to-Device (D2D) communications is considered to be a promising technique in next-generation communication networks aiming to enhance spectrum utilization and energy-efficiency. In this paper, we investigate the radio propagation behavior of the D2D channel in rural areas by conducting field measurements. We characterize the D2D channel by estimating the path-loss exponent and the standard deviation of the shadowing and by presenting the shadowing correlation analysis in various propagation environments using ISM band frequencies of 922 MHz and 2,466 MHz. The reported results are of great importance to system designers and researchers alike, to assist the development and the evaluation of innovative D2D protocols under realistic propagation conditions.

Propagation measurements in 5.8GHz and pathloss study for CEN-DSRC

Dedicated Short-Range Communications (DSRC) technology in the 5.8GHz band is a key enabler to support a safer and more efficient vehicular transportation in the future. The chosen 5.8GHz frequency band is therefore of great interest for us to study the propagation of signals under various environments. In this paper we investigate and record the propagation effects of 5.8GHz radio signals in an urban and sub-urban like environments with experiments conducted in the city of Melbourne for an infrastructure to vehicle (I2V) use case. The experiments were conducted for a TX-RX separation from 20m to 150m with line of sight conditions for the three chosen environments with and without the vehicle for comparisons as described in the paper. Based on the measurements we estimate the pathloss exponent and the shadowing standard deviation for the chosen scenarios. More interestingly our results show a constant pathloss for the measurements with the car when compared to the measurements without the car for different scenarios.

Aerial Platforms for Public Safety Networks and Performance Optimization

Abstract: Aerial platforms have recently become popular as key enablers for rapid deployable wireless networks where coverage is provided by on-board radio heads. These platforms are capable of delivering essential wireless communications for public safety agencies in the aftermath of natural disasters, and are also able to provide a rapid coverage patch in remote areas which are out of reach of the main public safety network. From this perspective, aerial platforms can be seen as an essential component for a reliable public safety network, since most of the public safety operations are of mission-critical and lifesaving nature. PSN operators can opt to have several standby aerial platforms in order to support emergency off-grid operations or to complement a damaged terrestrial network in case of a natural or man-made disaster. An optimized deployment of these platforms is essential, considering the fact that over-designing might not be an available choice in disaster circumstances. The optimization process includes the selection of several controllable parameters such as location, transmit power and antenna pattern, but perhaps one of the most important parameters is the altitude of the platform itself.

Performance Evaluation of LTE and WiFi Technologies in Aerial Networks

In recent times, aerial platforms have been investigated to provide wireless coverage to terrestrial radio terminals. The advantages of using aerial platforms to provide wireless coverage are many including larger coverage in remote areas, better line-of-sight conditions and resilience to certain natural disasters. In this context, we investigate the performance of using LTE and Wi-Fi technologies in aerial networks. More precisely, we consider a practical urban scenario from Melbourne, Victoria, Australia and perform ray-tracing simulations to characterize the path-loss of the air-to-ground channel. We then perform system-level simulations utilizing the channel-loss from ray-tracing to evaluate the performance of LTE and WiFi 802.11g technologies in aerial networks.