Showing posts from August, 2018

What is MIMO Communication in 4G and WiFi Networks ?

Recently, the wireless communication systems have been transformed and now they have more robust communication link and higher spectral efficiency. One of the main improvement, which has been implemented into current 4G and WiFi networks, is MIMO (Multiple-Input Multiple-Output) technique.

MIMO communication networks include more than one transmitter and receiver antennas in order to use multiple channel at the same time and frequency resources. The idea behind this technique is each antenna port can have a separate channel due to reflection and the scattering of the microwaves during the propagation. These channels are utilized using software based receivers and equalizer in order to simultaneously transmit data.

MIMO enhances the spectral efficiency, thus the capacity of the link besides providing more communication links.

Polarisation of Electromagnetic Waves

The polarisation of electric field states the orientation and magnitude of its field vectors and their alteration through the time. Polarisation is related to the transverse electromagnetic waves (TEM), in which directions and magnitudes of both electric and magnetic fields vary by time. Polarisation of EM waves from an antenna is classified into three main categories: linear, circular or elliptical polarisations. Furthermore, the direction of polarisation may be clockwise (CW, right-hand polarisation) or counter-clockwise (CCW, left-hand polarisation). For instance, the equation indicates a circularly polarized wave which consists of two components in the x and y directions. If polarisation of the receiver antenna does not match with the polarisation of incoming waves, the amplitudes of the received waves decrease. This polarisation mismatch will cause polarisation loss and reduce the power of the received signal. On the other hand, polarisation discrepancy can be employed to transm…