Visvesvaraya Technological University (VTU) 2007 B.E Computer Science on mobile communications - Question Paper

GPRS.
4.14 Why and when are various signalling channels needed? elaborate the differences?
4.15 How is localisation, location update, roaming, etc. done in GSM and reflected in the
data bases? elaborate typical roaming scenarios?
4.16 Why are so many various identifiers/addresses (e.g., MSISDN, TMSI, IMSI) needed
in GSM? provide reasons and distinguish ranging from user related and system related
identifiers.
4.17 provide reasons for a handover in GSM and the issues associated with it. Which are
the typical steps for handover, what kinds of handover can occur? Which resources
need to be allocated during handover for data transmission using HSCSD or GPRS
respectively? What about QoS guarantees?
4.18 elaborate the functions of authentication and encryption in GSM? How is system
security maintained?
4.19 How can higher data rates be achieved in standard GSM, how is this possible with
the additional schemes HSCSD, GPRS, EDGE? elaborate the main differences of the
approaches, also in terms of complexity? What issues remain even if the data rate
is increased?
4.20 What limits the data rates that can be achieved with GPRS and HSCSD using real
devices (compared to the theoretical limit in a GSM system)?
4.21 Using the best delay class in GPRS and a data rate of 115.2 kbit/s – how many bytes
are in transit before a 1st acknowledgement from the receiver could reach the sender
(neglect further delays in the fixed network and receiver system)? Now think of typical
web transfer with 10 kbyte avg. transmission size—how would a standard TCP
behave on top of GPRS (see chapter nine and chapter 10)? Think of congestion
avoidance and its relation to the round-trip time. What modifications are needed?
4.22 How much of the original GSM network does GPRS need? Which elements of the
network perform the data transfer?
4.23 elaborate typical data rates in DECT? How are they achieved considering the TDMA
frames? What multiplexing schemes are applied in DECT for what purposes?
Compare the complexity of DECT with that of GSM.
4.24 Who would be the typical users of a trunked radio system? What makes trunked radio
systems particularly attractive for these user groups? elaborate the main differences
to existing systems for that purpose? Why are trunked radio systems cheaper
compared to, e.g., GSM systems for their main purposes?
4.25 Summarise the main features of third generation mobile phone systems. How do they
achieve higher capacities and higher data rates? How does UMTS implement

Earning:   Approval pending.