(A)What is ciphering
Ciphering modifies the
contents of the eight interleaved blocks through the use of encryption
techniques to the particular mobile station and base transceiver station.
Two types of ciphering
algorithms, called A3 and A5, are used in GSM to prevent unauthorized network
access and privacy for the radio transmission respectively.
How many carrier frequencies
are there in GSM-900 and DCS-1800? How much is the separation between the
carrier frequencies?
124 carriers.
There are 8 channels in each carrier.
Channel separation is 200 KHz.
What is the Downlink and uplink spectrum is
allocated to DCS-1800?
1800 MHz. Up link
Frequency 1725-1780 MHZ.
Down link Frequency
1820-1870 MHz