Open Signal is a mobile application that collects the data about your wireless network (2G/3G/4G) and generates coverage maps and host of other reports. The data is collected in the background while the user is busy in his daily routines. But data can also be collected on the request of the user. This is much better than drive testing since the data is collected in real life scenarios and on thousands of different devices that are in use.
The app works while the user is indoor or outdoor, at rest or in motion, on land or on water, at sea level or on a mountain, in dry weather or in rain. Basically anywhere and anytime there are wireless signals available. There are currently 20 million users of the app (both Android and iOS combined) and this number is increasing. In Pakistan all major networks are supported including Jazz, Telenor, Zong and Ufone (both 2G/3G and 4G networks are supported).
A Radiation Pattern is a 3 dimensional description of how an antenna radiates power in the surrounding space. This pattern is usually measured at a sufficient distance from the antenna known as the far-field. In simple words it is the power radiated in a certain direction with reference to an omni-directional antenna (a theoretical antenna that radiates equally in all the directions). Given below are the radiation patterns for some common antenna types.
Dipole Antenna 3D Radiation Pattern
Yagi Antenna 3D Radiation Pattern
Sector Antenna 3D Radiation Pattern
Although the Radiation Pattern is a 3 dimensional quantity it is usually sufficient to describe it in two orthogonal planes (one horizontal and one vertical) as shown in the figures above.
 Cisco Aironet Antennas and Accessories: Antenna Patterns and Their Meaning
Antenna Gain and Directivity are two terms that are sometimes not that well understood. The Antenna Gain and Directivity are related through the following equation.
That is, the Antenna Gain in a particular direction is equal to the Directivity in that direction multiplied by the Antenna Efficiency. Antenna Directivity is the ratio of energy transmitted (or received) by the antenna in a particular direction to the energy transmitted (or received) in that direction by an isotropic source. This is also known as the Directive Gain.
The Antenna Gain (also known as the Power Gain) seems to be a better metric to quantify the performance of an antenna as it takes into account the efficiency in converting electrical energy supplied to the antenna into radiated energy.
The 3-dimensional plot of the Gain of an antenna is known as the radiation pattern. The Antenna Gain with reference to an isotropic source is given in dBi (decibel above isotropic source). Sometimes the Antenna Gain is given with reference to a Dipole Antenna and is labelled as dBd. The figure below shows the Directivity of a Patch Antenna embedded inside a human body .
1. An isotropic source (a source that radiates uniformly in all directions) is only a theoretical concept and does not exist in reality.
2. The sun can be considered an isotropic radiator since it radiates uniformly in all directions (almost).
3. When no direction is given the Gain refers to the maximum Gain.