A Primer on Ray-Tracing: Shooting and Bouncing Ray Method
Ray-tracing is a promising alternative for Radio Frequency Planning particularly in urban areas. There are two fundamental techniques used for ray-tracing namely Shooting and Bouncing Rays and Method of Images. In this paper, we focus on the former and present simulation results for an urban scenario in the city of Helsinki. We also give an insight into how the Shooting and Bouncing Ray method can be implemented using basic linear algebra techniques. We show that ray-tracing can be used to evaluate the performance improvement attained through electromagnetic reflectors. Finally, we close the discussion by outlining the existing challenges and the way forward.
Orthogonal Minimum Shift Keying: A New Perspective on Interference Rejection
Co-Channel Interference is a classical problem in cellular systems that has been studied extensively and several methods have been proposed to overcome it. These include interference rejection techniques as well as joint detection techniques. We have previously proposed a joint detection technique for MSK-type signals that works quite well in certain conditions. In this paper, we formally present what we call Orthogonal MSK and postulate that if two MSK signals have a 90-degree phase offset between them then both can be detected successfully increasing the spectral efficiency two-fold. This technique works well even if the two signals are near equal power and have the same carrier frequency.
Why is MIMO Capacity in a Fading Environment Higher than in an AWGN Environment
A wireless channel suffers from two fundamental impairments; fading and noise. While fading is multiplicative, noise is additive. It is well-known that higher the noise, lower is the signal to noise ratio and lower the capacity. However, fading can be helpful in increasing the capacity when using multiple transmit and receive antennas. In this paper, we give an intuitive explanation for this. Anybody with a background in linear algebra and matrices can understand this.
This textbook covers fundamental topics in Telecommunication including Channel Modeling, Modulation/Demodulation, Channel Coding/Decoding, Multicarrier, Capacity, Antenna Arrays, Diversity, and 4G/5G. It will also cover advanced topics such as High-Resolution Spectral Estimation, Reconfigurable Intelligent Surfaces, Index Modulation, Full-Duplex, and Millimeter Wave. This book will mainly target engineering students (both graduate and advanced undergraduate) who are new to the fields of Communication and Signal Processing and are struggling to understand the fundamental concepts. This book will help the students step by step by introducing the concepts first in their most basic form and then providing the code that the students can experiment with. It contains pedagogical elements such as chapter introductions, end-of-chapter questions and numerical problems, MATLAB/Octave/Python code, figures and tables, and a website (raymaps.com) for feedback and interaction. It will not only be helpful for undergraduate and graduate students but also for professional engineers and hobbyists.
Yasir Ahmed has more than 20 years of experience in various organizations in Pakistan, Europe, and the USA in both Engineering and Management roles. He worked as a Research Assistant in the Mobile and Portable Radio Group (MPRG) of Virginia Tech under the supervision of Dr. Jeff Reed and was one of the first researchers to propose Space Time Block Codes (STBCs) for eight transmit antennas. The collaboration with MPRG has continued over the years and has resulted in 12 research publications and a book on Wireless Communications. Yasir worked as GM SEED at Ignite National Technology Fund, a company involved in supporting the innovation and entrepreneurship ecosystem in the country. He previously worked for Qualcomm USA, leading the physical layer performance and conformance testing of GSM/UMTS modems, and for COMSATS Islamabad as an Assistant Professor, teaching various subjects in the Telecom and Networks area. He was part of the Ignite team that evaluated multi-billion-rupee NIC and DigiSkills programs and has also helped fund a number of startups that have gone on to become successful commercial ventures.
There has been a continuous debate about harmful effects of Electromagnetic Radiations ever since they came into existence. Most of the research results suggest that there are no harmful effects, if the rules and regulations are followed. But there is a small body of research that suggests that there might be some harmful effects and more research needs to be carried out. This is particularly important now as 5G Wireless Technology is being rolled out around the world and it uses millimeter waves for which we have limited data. Also, 5G would be using much smaller cells meaning that base stations would be closer to human beings.
Wireless channel
is inherently unpredictable and this results in loss of information as it
travels from the transmitter to the receiver. The main reason for this is that
multiple copies of the wireless signal arrive at the receiver which sometimes
add constructively and at other times destructively, causing deep fades. The
deciding factor between signal copies (think of them as echoes) adding
constructively or destructively is the relative phase. If the phases are
aligned the signals add up but if the phases are not aligned, we get a fade
(fades can be as deep as 60-80dB). Wireless engineers over the years have
worked around this problem by using multiple antennas also called antenna
arrays.
