Implications of diversity from a sensing point of view

The objective of this chapter is to illustrate that the influence of diversity in the regeneration of species is quite different from the effect of diversity in a vector wireless environment. Diversity in a regenerative environment is always welcome and often provides variety, the often desired spice of life. However, diversity from an electrical engineering standpoint is quite different, as the vectors representing a desired outcome may add or subtract, resulting in a final form that can be beyond any common sense expectation and that cannot be anticipated a priori unless the environment is clearly defined. This situation is primarily true for electromagnetic sensing. Examples are presented to compare the principles of physics with the conventional wisdoms of established myths held by most wireless practitioners. One area of recent notoriety in the wireless community is the multiple-input multiple-output (MIMO) system and the associated misinterpretation and misrepresentation of the various metrics often used to illustrate MIMO’s superiority over conventional systems. Just like the vector problem when the quantities of interest add in phase, one gets superior performance; however, when they subtract, the performance can be very bad. Clearly, one cannot average good and bad behaviors, because each piece of datum is equally important-like transmitting one’s bank balance over wireless where each digit has to be accurate and an average value really has no significance.