Category Archives: Mobile communications


Wavelength is the distance between the peaks of an electromagnetic wave. Wavelength (λ) and frequency (f) are linked by the velocity of propagation (u) of the waves.



The higher the frequency (f), the shorter the wavelength (λ).


Visitor Location Register (VLR)

Some networks provide Visitor Location Registers (VLR) at their MSCs (Mobile Switching Center), such that, one an MS (Mobile Station) roams from a different traffic area, the subscriber information from its HLR (Home Location Register) can be transmitted to and temporarily stored in the VLR. VLRs prevent unnecessary, potentially long-distance, repeated communication with the HLR.

Home Location Register (HLR)

Each MSC (Mobile Switching Center) has access to a database called Home Location Register (HLR). This contains information on all subscribers who are initially registered within its traffic area. This information includes the subscriber identity numbers, MS (Mobile Station) identity numbers, service subscription details, usual and present traffic area locations plus authentication and encryption keys.