Download COM5345 Midterm-1 Reference Solutions 1. Sol. AMPS, IS

COM5345 Midterm-1 Reference Solutions
1. Sol.
AMPS, IS-41, IS-136 and IS-95 are all standards of North-America wireless
communication systems.
z IS-41 is the standard for core-network.
z AMPS, IS-136 and IS-95 are the standards for radio access network.
z AMPS is 1G system, while IS-136 and IS-95 belong to 2G systems.
i.
AMPS is an analog system using FDMA.
ii.
IS-136 is a digital system using TDMA.
iii.
IS-95 is a digital system using CDMA.
2. Sol.
z Each subscriber to 3GPP network services is assigned a globally unique IMSI
as its permanent identifier. A subscriber uses its IMSI as its common
identifier for accessing PS, CS, or both PS and CS services at the same time.
z
z
A subscriber’s IMSI is stored on a USIM on a mobile station.
To reduce the need to transmit IMSI over the air, 3GPP uses a TMSI to
identify a mobile whenever possible. A TMSI is a 4-octet number assigned to
a mobile temporarily by an MSC/VLR for CS services or by an SGSN for PS
services. The mapping between the mobile’s TMSI and IMSI is known only
by the mobile and the network node that assigned the TMSI.
3. Sol.
UE
ME
MT
USIM
TE
TA
4. Sol.
The switching and call control functions of an MSC are separated and
implemented on the following network entities:
i.
MSC Server: for handling call control and mobility management.
ii.
CS Media Gateway: for handling circuit-switching, media conversion,
payload processing, payload transport.
Separation of switching and call control allows switching and call control
technologies to evolve independently. It also helps increase network scalability.
5. Sol.
6. Sol.
UE1
Radio bearer
Node B
UE2
7. Sol.
Iu (GTP Tunnel)
RNC
SGSN
Gn (GTP Tunnel)
GGSN
8. Sol.
User IP packets are encapsulated and tunneled over an A10 connection between
PCF and PDSN and over A8 connection between BSC and PCF. The A10 and A8
connections are implemented as IP tunnels using the GRE protocol. Since the PPP
session is tunneled by the GRE protocol, the PPP session will not break. Therefore,
there is no need to reestablish the PPP session when a MS moves to a new BSC or
PCF within the same PDSN.
9. Sol.
No, the 3GPP2 packet core network does not directly interface with the circuit
core network. Through BSC inside the radio network, PDSN can access the
information in the HLR.
10. Sol.
z Differences:
3GPP
Radio network
z
3GPP2
WCDMA: divided into cdma2000: One RN
CS (GERAN) and PS using CS technologies.
(UTRAN)
Interface
between Direct interface
PS-CN and CS-CN
No direct interface
CS-CN Evolvement
GSM
IS-41
PS-CN Evolvement
GPRS
New PS technology.
Most protocols follow
IETF standard.
Tunneling in PS-CN
GTP tunneling
GRE tunneling
Others
...
…
Similarities:
i.
Both core network architectures are divided into PS and CS domain.
ii.
Radio technology uses CDMA.