If you’ve been following of our recent blog you’ll come across different modulation technics such as Phase shift-keying, Gaussian frequency-shift keying. This blog post goes into the detail of Gaussian Minimum Shift Keying. Gaussian filtered Minimum Shift Keying (GMSK) is a form of modulation used in a variety of digital radio communications systems.
Let’s understand GMSK using GNU Radio,
Basic function of blocks in GNU Radio companion is to generate and process a waveform and GNU Radio companion comes with some modulation blocks which helps to demonstrate modulation technics.
Gaussian Minimum-Shift Keying (GMSK) is used in Global System for Mobile communication. One exiting feature about GMSK is that it make use of spectrum in efficient way.
When we are using other forms of modulation technic sidebands extend outwards from the main carrier and these can cause interference to other radio communications systems.
Before we start with Gaussian Minimum-Shift Keying (GMSK) let’s have a look on minimum-shift keying (MSK) because GMSK modulation is derived from MSK. MSK is a type of continuous-phase frequency-shift keying, where information is encoded with bits alternating between quadrature components, with the Q component delayed by half the symbol period.
In digital communication, GMSK is a continuous-phase frequency-shift keying modulation scheme. It is similar to standard minimum-shift keying (MSK); however the digital data stream is first shaped with a Gaussian filter before being applied to a frequency modulator. This has the advantage of reducing sideband power, which in turn reduces out-of-band interference between signal carriers in adjacent frequency channels.
To know more about implementation of GMSK in GNU Radio companion, please click on the link for the application note below,