Waves in Communications Flashcards
satellite range/frequency
Beam signals up and down between satellites and ground stations allowing them to be sent around the world
High frequency range of 1-50GHz
Communication range of over 13 billion
Cellular range/frequency/networking
Talks with transceiver tower in a cell of a few km in radius
Low frequency range of 2.4-5GHz
Networked together to cover the country and also joined to the wider telephone network
Wi-fi hub range/frequency/networking
Low frequency range of 2.4-5GHz
Range of 50m of less
Wi-fi hubs connect to a wired local network and together cover a whole building
Bluetooth range/frequency
10-400m
From 2.402GHz to 2.481GHz
What satellites do to avoid interference
Have two dish antennas and use quite different frequency bands for up/downlink
Transponder unit on board receives, filters, amplifies and retransmits on the new frequency
What phones do to avoid interference
Phones transceivers (transmitter-receivers) use separate frequencies for up/downlink, but these are nearby channels
In addition, each cell also uses a different frequency from all its adjacent cells
What Bluetooth does to avoid interference
Frequency-hop across a range of channels many times a second to limit their interference with Wi-FI, which operates in the same frequency band
Handshaking
Series of short messages sent backwards and forth allowing one device to recognise another and to set up communication parameters.
Connecting to wi-fi
Handshaking pros
Stops info getting lost or jumbled by acknowledging when message received
What do phones do when travelling
Swap from one cell to another as user travels
Networking with satellites ground stations
Linked into communications network
Bluetooth and infrared networking
Not networked, just for device-to-device links
GHz
Gigahertz
What are communications parameters
Basic setting for modern transmission
