A Discussion About Some of the Principles/Practices of Wireless Communication Under a Maxwellian Framework

Abstract

There has been a plethora of papers dealing with wireless communication that use techniques, which when viewed from the perspective of a Maxwellian framework raise more questions than they answer. By Maxwellian framework we imply not only the relevance of electromagnetics in studying communication systems but also the proper interpretation of an ensemble processing in mathematical physics which was first introduced by Maxwell to study the behavior of an aggregate of molecules rather than the property of individuals. Initially, most of the modern signal processing techniques was developed for scalar acoustic problems. However, with the advent of wireless, these same techniques are being applied to the vector electromagnetics problem, which is fundamentally different in concept with respect to the scalar acoustic problem. The objective is to discuss some of these concerns associated with some of the current modeling methodologies particularly related to propagation modeling and antenna diversity. A goal is to initiate a dialog about the scientific merits of these new applications. One of the points to be made is that an incorrect use of probability theory can often lead to erroneous conclusions that directly contradict the principles of physics.A few examples are presented to initiate this dialog, mainly the applicability of scalar techniques to the vector wireless problem, including a proper interpretation of the Shannon channel capacity theorem. A methodology is also presented to illustrate how a simple multiple-input-multiple-output system can be based on the principles of reciprocity. Integration of the electromagnetic principles in some of the current methodologies of signal processing and communications theory may lead to a better system.

Hard-Input–Hard-Output Capacity Analysis of UWB BPSK Systems With Timing Errors

“…It is well known that for systems with large operating bandwidths, such as UWB systems, the soft-output capacity may not be a proper metric, as they only consider the propagation channel [43], while hard-output capacity takes the whole system into account and therefore, is more useful in this case. It is very challenging to derive the soft-output capacity and the exact hard-ouput capacity by taking the timing error and all the interferences into account.…”

EXPERIMENTAL INVESTIGATION OF GSM 900 MHz RESULTS OVER NORTHERN INDIA WITH AWAS ELECTROMAGNETIC CODE AND OTHER PREDICTION MODELS

“…However, the curve due to AWAS passes through the thick cluster of observed values. Sarkar et al [13] have shown that even in urban environment numerical electromagnetic codes based on Sommerfeld theory derived from Maxwell's postulates can be used to predict propagation characteristics. If one knows the electrical characteristics of the earth, it is possible to predict how the field strength will vary with the distance without carrying the experimental measurements.…”

“…In this study, the type of ground is the same in the case of all base stations, and the difference in urban and suburban regions comes from the degree of urbanization. In [13], a value of 4 for dielectric constant has been chosen for urban region when real earth is considered with imperfectly conducting ground. Keeping these aspects in view, we have carefully chosen a value of 6 for urban base stations and a value of 8 for suburban base stations in the AWAS simulation.…”

Multi-Antenna Information Theory

“…The most general upper bounds of capacity of a MIMO system have been given in (15) and (16). Now these general upper bounds will be applied to MIMO system in free space.…”

“…Therefore the channel models that include physical parameters are preferred. It has been noted that incorporating electromagnetics into the methodologies of signal processing and communication theory will lead to a better solution when deploying a system in a real environment [16]. In this paper, a general procedure of predicting the MIMO channel model from an electromagnetic point of view has been presented, which is based on the scattering matrix description of the MIMO system.…”