SOLUTION TO TEST 1 (1)
Uppgjord (även faktaansvarig om annan) - Prepared (also subject responsible if other) Nr - No.
KI/ERA/GDU/TG David Stalbe 2/ 038 17 - EN/LZU 108 888 Uen
Dokansv/Godk - Doc respons/Approved Kontr - Checked Datum - Date Rev File
KI/ERA/GD/UX Jimmy Westerlund 1999-10-22 A 03817_2.doc
WCDMA EXPERIMENTAL SYSTEM WORKSHOP
SOLUTIONS TO FINAL TEST
1) What are the different types of handover called? What are they used for?
Soft Handover Handover between two base stations.
Softer Handover Handover between two sectors within the same base station.
Hard Handover Change of frequency, change of short code.
2) Explain what is power control and why is it used?
Power regulation according to the path loss. The mobile transmits with low
power when it is close to the base station. When the mobile is far away from
the base station it transmits with high power.
Without power control the C/I value could become extremely small (~10-7) for
those mobiles that are far away from the base station, assuming that there
are mobile stations close to the base station that don’t adjust their power.
Thus, we need to introduce power control, which will solve the near-far
problem.
The near-far problem occurs when a strong signal from a mobile station close
to the receiving antenna will drown the signal of a mobile station that is far
away.
Power control has a side effect of prolonging the mobile’s stand-by time.
3) Explain the three different modes of power control. Where are they
performed? Draw a figure if you like.
The initial power control is based on measurements
on the downlink channel and gives a coarse estimate
Open (Initial) Loop
of what power level should be used initially for the
uplink channel.
Measurement on slot basis (1600 times per second)
Fast (Closed) Control Loop
from the opposite node. "Up or Down 1 dB"!
Measurement on a couple of frames (~100 equals to
Quality Control (Outer) Loop once a second) which sets or changes the target E b/I0
value.
SOLUTION TO TEST 2 (2)
Uppgjord (även faktaansvarig om annan) - Prepared (also subject responsible if other) Nr - No.
KI/ERA/GDU/TG David Stalbe 2/ 038 17 - EN/LZU 108 888 Uen
Dokansv/Godk - Doc respons/Approved Kontr - Checked Datum - Date Rev File
KI/ERA/GD/UX Jimmy Westerlund 1999-10-22 A 03817_2.doc
4) Explain what MOI data and MIO data are and the difference between
them.
MOI stands for Managed Object Interface and collects text notifications. MIO
stand for Multi-purpose Input/Output and collects binary data.
Text notifications can be viewed immediately, while binary data has to be
collected first and the file must be closed before it is possible to view the data.
There are some steps that has to be followed when collecting MIO data:
A) Open the MIO port, which collects the data to a file.
B) Specify the file where the data is to be collected.
C) Turn on reception parameters in Navigator to collect MIO data.
D) Turn on the node’s measurement status to "ON" for the data being
collected.
E) Start the logging session.
F) Close the logging session after some measuring time.
G) Open the same file in Navigator again and look into it. The binary
data are now converted to text messages.
5) What is the difference between the UDI service and the packet data
service?
Unrestricted Digital Information (UDI) Packet Data
Is transmitted on DTCH/ACCH. Is transmitted on UPCH.
If CRC check of the frame is faulty, the
No retransmissions.
packet is retransmitted.
Stronger coding (outer Reed-Solomon)
Convolutional coding.
which can correct more errors.
SOLUTION TO TEST 3 (3)
Uppgjord (även faktaansvarig om annan) - Prepared (also subject responsible if other) Nr - No.
KI/ERA/GDU/TG David Stalbe 2/ 038 17 - EN/LZU 108 888 Uen
Dokansv/Godk - Doc respons/Approved Kontr - Checked Datum - Date Rev File
KI/ERA/GD/UX Jimmy Westerlund 1999-10-22 A 03817_2.doc
6) Explain the different nodes in the Experimental System. What are the
major tasks for each one of them?
Node Major Tasks
Mobile Simulator Encodes/decodes speech. Adds error correction coding. Spreads a
base band bit stream into 5 MHz wideband. Despreads a wideband
bit stream into base (narrow) band. Modulates the signal with QPSK.
Measures the signal to noise ratio and sends power control
information to the base station. Measures neighbouring cells and
sends a measurement report to the Radio Network Controller.
Base Transceiver Station Antenna diversity handler. Puts the speech/data on an "Iub" ATM link
towards the Radio Network Controller.
Radio Network Controller Controls the radio resources in the system, Handover, admission
control ("Do I have the radio resources to support a call with
spreading factor 128" type of questions), macro diversity combining,
the outer control loop, timing and synchronisation between nodes in
the system. Speech encoding/decoding, G.729 codecs. Uses AAL2
and AAL5. Connects with Mobile Switching Center on an "Iu" ATM
link. Can handle several base stations.
Mobile Switching Center Echo cancelling, IP router, ISDN adaptation, ATM LAN interface.
Data adapter functions for circuit and packet data. Call switching.
WCDMA Operations System Monitors the different nodes. Enables remote access to each node,
collection of data, text messages and tools for Power Control,
Handover among other applications to see how the system behaves
in different states. Only one measurement session per node is
possible; two WOSs cannot connect to the same measurement.
7) Explain the multicode data transmission.
Multicode is used for high data rates. The bit stream is divided into three 256
ksymbol (maximum 470 kbit/s) UPCH channels.
8) How does a RAKE receiver work?
The purpose of a RAKE receiver is to combine multiple replicas of the same
signal, which arrives to the receiving antennas with different delays. It
allocates each "finger" to follow a sufficiently strong multipath component.
Mainly, it has two functions: 1) to find the delays and 2) to combine the
signals that were found.
SOLUTION TO TEST 4 (4)
Uppgjord (även faktaansvarig om annan) - Prepared (also subject responsible if other) Nr - No.
KI/ERA/GDU/TG David Stalbe 2/ 038 17 - EN/LZU 108 888 Uen
Dokansv/Godk - Doc respons/Approved Kontr - Checked Datum - Date Rev File
KI/ERA/GD/UX Jimmy Westerlund 1999-10-22 A 03817_2.doc
9) How does the RAKE receiver take care of the delay power spectrum?
It searches for the signal by correlating the received signal with the known
pilot symbols, which creates high peaks when a matching pattern is found. In
this way, the multipath components of the signal, which all arrive with different
time delays, can be detected by scanning the whole code-tracking window.
This procedure creates the known Delay Power Spectrum or Impulse
Response.
10) What is the difference between ATM Adaptation Layer 2 and ATM
Adaptation Layer 5?
AAL2 can combine speech data from several users into the same ATM cell. It
is used for synchronous services.
AAL5 is dedicated to transport data traffic, the packet data service in the
Experimental System. Only one user is allowed per ATM cell.
