Evolution from 1G to 5G and its Applications

1. Evolution of Cellular Generations: From 1st Generation – 4th Generation (Summary)
Evolution of Cellular Generations: From 1st Generation – 4th Generation (Summary)

2. Evolution of Cellular Generations: From 1st Generation – 4th Generation and Beyond (5G)
Evolution of Cellular Generations: From 1st Generation – 4th Generation and Beyond (5G)

3. Unit-2

4. MULTIPLE ACCESS SCHEMES
WIDELY USED SCHEMES
•Frequency Division Multiple Access (FDMA)
•Time Division Multiple Access (TDMA)
•Code Division Multiple Access (CDMA)

5. FREQUENCY DIVISION MULTIPLE ACCESS
• The available system bandwidth W is divided into N nonoverlapping bands, each
of width Wu.
• A guard band is provided between bands Wu, to reduce interference from
adjacent channels.
• The bands Wu are assigned on demand to users who request service. During the
period of service, no other user can share the same frequency band. When the
user terminates the service, the frequency band may by reassigned to another
user.

6. • An FDMA channel carries only one phone circuit at a time.
• If an FDMA channel is not in use, then it sits idle and cannot be used by
other users to increase or share capacity.
• The bandwidths of FDMA channels are relatively narrow (30 kHz) as
each channel supports only one circuit per carrier.
• Since FDMA is a continuous transmission scheme, fewer bits are needed
for overhead purposes (like synchronization and framing bits) as
compared to TDMA.
• FDMA systems have higher cell site system costs as compared to other
systems, because of the single channel per user design.
• FDMA requires tight RF filtering to minimize adjacent channel
interference.
Features of FDMA:

7. • The first U.S. analog cellular system, the Advanced Mobile Phone System
(AMPS), is based on FDMA/FDD.
• A single user occupies a single channel which is actually comprising of 2
simplex channels which are frequency duplexed with a 45 MHz split.
• In AMPS, analog narrowband frequency modulation (NBFM) is used to
modulate the carrier.
• The number of channels that can be simultaneously supported in a FDMA
system is given by
Features of FDMA:

8. FREQUENCY DIVISION MULTIPLE ACCESS
Number of channels in a FDMAsystem:
• N … number of channels
• Bt … total spectrum allocation
• Bguard … guard band
• Bc … channel bandwidth

9. • Example :
If Bt is 12.5 MHz and Bguard is 10 kHz, and Bc is 30 kHz, then find the number of
channels available in an FDMA system ?

10. Time Division Multiple Access (TDMA)
• Time division multiple access systems divide the time axis into slots. The slots are grouped
in frames.
• Only one user is allowed to transmit or receive in each slot. Each user occupies a cyclically
repeating time slot, thus a channel may be thought of as particular time slot that reoccurs
every frame.
• In TDMA system the transmission for any user is discontinuous. That is why, unlike FDMA
systems which accommodate analog transmission, digital data and digital modulation must
be used with TDMA. In TDMA/TDD systems, half of the time slots in the frame is used for
the forward link channels and half is used for reverse link channels. In TDMA/FDD
systems, a similar frame structure is used solely for either forward or reverse transmission,
but the carrier frequencies are different for the forward and reverse links.