WCDMA Introduction and Overview

• WCDMA concept and Architecture• Spreading and Scrambling• Codes and Channels• Code tree• Rake Receiver• Soft, Softer and Hard hand over• Power control - fast and slow

WCDMA – Drive test Overview using TEMS Investigation

• TEMS Parameter for WCDMA• Optimization Tips for WCDMA• WCDMA Tools for Drive Test• 3G Voice Call Testing• 3G Packet call & Video call testing• 3G Drive test KPI overview• 3G Optimization overview

WCDMA Introduction and Overview

• WCDMA concept and Architecture• Spreading and Scrambling• Codes and Channels• Code tree• Rake Receiver• Soft, Softer and Hard hand over• Power control - fast and slow

WCDMA – Drive test Overview using TEMS Investigation

• TEMS Parameter for WCDMA• Optimization Tips for WCDMA• WCDMA Tools for Drive Test• 3G Voice Call Testing• 3G Packet call & Video call testing• 3G Drive test KPI overview• 3G Optimization overview

Interview and drive test tips

WCDMA Frequency and Spectrum

• Uplink=1920MHz -1980 MHz• Downlink= 2110MHz -2170MHz• Bandwidth=60 MHz Actual B.W assign to operator is 5MHz And out of that 3.84 MHZ is utilize.In WCDMA frequency reuse factor =1 because time and

frequency remains constant.

• In WCDMA first following process is done before Reading BCCH frequency. Slot Synchronization Frame Synchronization Scrambling CodeCPICH is pilot which will read BCCH information After Synchronization .In WCDMA following Channels use for various function in UL/DL.Downlink:- Uplink:-1.DL DPCH 1.UL DPDCH2.DL CCPH 2. UL DPCCH3. P-CCPH 3. UL CPCH4. S-CCPH 4. UL PRACH5. SCH 5. HS-DPCCH6. PICH7. CPICH (primary and secondary)8. AICH

WCDMA Spreading process

• Spreading:- This is used to increase the B.W of the signal beyond the bandwidth normally required to accommodate information.

For Spreading OVSF code are used which is known as Orthogonal variable spreading factor code .

Spreading factor=chip rate/symbol rate .Scrambling – Scrambling is used on top of the spreading so , it

does not change the signal bandwidth but only makes the signal from different source separable from each other.

Process gain = 10 log (chip rate/bit rate)As bit rate increase process gain decrease .Cell breathing is situation where cell foot print decrease due to

large amount of user access the network beyond the capacity of that particular cell.

• Eb /NO= Bit energy/Noise energy• Ec/No = Chip Energy /Noise Energy.

• Ec/No= Eb/No - process gain• As per Eb/No is fixed for each service for Ex: voice =2 and

video=4• Ec/N0= 2- 10= -8 for voice(for voice -8 is good limit)• Ec/N0= 4-18= -14 for video(for video -14 is good limit)

• Process gain(voice) = chip rate/bit rate= 10dB• Process gain (video) = chip rate /bit rate= 18dB• Chip rate = 3.84Mchips in WCDMA.

WCDMA codes

Code tree

Rake Receiver

Soft Handoff

Power Control types

For Speech drive Test

Mobile TX power

Received signal strength indication

Target Signal to interfere ratio

Signal to interfere ratio

Speech quality mean opinion square

Dedicate channel

GSM/WCDMA

Speech quality

SQI MOS Algorithm

Downlink Dedicate channel BLER%

Active Set- Currently serving Cell Measured neighbor- Defined Neighbor

Detected Neighbor- Undefined strong detected serverUARFCN DL- UMTS Absolute radio frequency channel number

Ranges for Radio Parameter

• 1. CPICH EC/No- 0 to -34 dB.• 2. CPICH RSCP - -15 dBm to -140 dBm for each rake finger.• 3.Ms TX power – -44 dBm to 60 dBm• 4. UTRA Carrier RSSI - -20 dBm to -140 dBm for each rake finger.• 5. SQI MOS - 1 to 5• 6. SQI - -20dBQ to 30 dBQ• 7 . SIR - -30 t0 20 db (signal interfere ratio measured on DPCCH )• 12.2 Kbit/s: 30 dBQ

10.2 Kbit/s: 28 dBQ7.95 kbit/s: 28 dBQ7.40 kbit/s: 27 dBQ6.70 kbit/s: 27 dBQ5.90 kbit/s: 24 dBQ5.15 kbit/s: 21 dBQ4.75 kbit/s: 19 dBQ

Drive Test KPI

• Parameter-• RSSI – In Between -75 to -85 dbm• RSCP – In Between -75 to -85 dbm• Ec /Io – In Between -8 to -10 db• FER – 1% or 2%• Ms TX Power - Between -5 to -10• Soft Handoff – 35% of total time

Use full Plots

• Server Plot – Useful to find out Swap or Overshooting.

• UE Plot - To Check Neighbour Relation.• RSCP Plot- Coverage wholes• Ec /No- for good Throughput and removing

pilot pollution.• 4th best Server – Echno should be > -10db• 5th best Server – Echno should be > -10db

Condition for Radio Environment

• Pilot Pollution – RSCP >= -85dBm & Ec /Io =< -10 dB Coverage Limited – RSCP <= -85dBm & Ec /Io => -10 dB Poor Radio Condition- RSCP <= -85dBm & Ec /Io =< -10 dB Good Coverage –RSCP >= -85dBm & Ec /Io => -10 dB

3G –voice call testing

SCFT-Single Cell Functional Test• Before the single site verification, we should only ensure the following

conditions have been met. – Alarm Check– Cell Status Check– Parameter Check

• Alarm Check / Cell Status Check

– The product support engineer will be responsible for checking and resolving all the

alarms. It is important for the optimization engineer prior to any field test to check

with product support engineer regarding any alarms especially intermittent

alarms.

• Parameter Check

– The optimization engineer need to ensure the radio part parameters configuration

list has been achieved. In the list the radio part parameters includes: the

scrambling code, power setting, neighbor cell list, handover parameter etc.

3G –voice call testing

• Site Verification Items:– Installations: CPICH RSCP, CPICH Ec/Io, Rx Antenna Swap

Test– Settings: Frequency & SC, Cell reselection parameters,

LAC/RAC, Neighbor List.– Functions: LA/RA update, 3G<->2G Cell reselection, SMS

(MT & MO), Voice (MT & MO), VP (MT & MO), PS Attach & Detach, PS service, Voice/VP/PS soft handover, Voice 3G->2G handover

Testing On CELL site

– Items: Voice Call (MT & MO)

– Purpose: Verify the voice call function is normal and the voice call quality is

good

– Method: Make the dialing test of 3G voice service between two 3G mobiles,

one for the terminating call and another one for the originating call. Test the

voice communication quality

– Items: Voice Call (MT & MO)

– Purpose: Verify the voice call function is normal and the voice call quality is

good

– Method: Make the dialing test of 3G voice service between two 3G mobiles,

one for the terminating call and another one for the originating call. Test the

voice communication quality

Feeder Connection Check

Test Process Items: Antenna swapping testPurpose: Verify the Rx feeder installation is right.Method: Switch the transmitter from one feeder to another, check the RSCP changed or not. If no change happened, it means that the feeder is correct.Notes: Check the RSCP from scanner

Problem and Solution

• In the site verification, following problems have been found

– Scrambling Code Setting is wrong: The scrambling code from scanner and

mobile is different from the planning

– After feeder swapped, the CPICH RSCP is 20dB lower than before.• Scrambling Code Setting is wrong

– The Scrambling Code may be wrong in RNC, check the datasheet in RNC.

– If the Scrambling Code from scanner is the same as that of another sector in same site planned, maybe the TX/RX feeder is crossed to the another sector.

• After feeder swapped, the CPICH RSCP is 20dB lower than before: – The RX feeder is crossed to the antenna of another sector. In this

case, the CPICH RSCP will be high in the coverage area of the other antenna. Check the connection between the feeder and the antenna.

DATA drive window

Data Drive Parameter with low through. put

Channel quality index

Modulation technique

As 64 QAM is utilized so less HSDPA

throughput is less.

Case-2 with high throughput

In this case 16 QAM is used 100% and

Throughput is high

Data Drive

• There is 3 modulation technique QPSK,16QAM,64QAM.• For high through put 16QAM and 64QAM should be utilized high

Utilization• So, if There is less Utilization of QPSK in downlink than data throughput is

also high’• CQI is like SQI in speech which ensure good channel quality for data

transfer.• Retransmission of HS- DSCH(High-Speed Downlink Shared Channel) packet

is high than also throughput is decreases.• In case of stationary Data Test- 2Mbits speed can be achieved • In case of moving Vehicle – 800kbits to 1.2 Kbits speed can be achieved.• Application throughput is always 85% of physical layer data rate

throughput because at application level IP inclusion and overhead information will be there.

• Latency time is round trip time from server and for 3G it should be 150 ms for 32 bit data .

• The modulation scheme and coding is changed on a per-user basis depending on signal quality and cell usage. The initial scheme is Quadrature phase-shift keying (QPSK), but in good radio conditions 16QAM and 64QAM can significantly increase data throughput rates. With 5 Code allocation, QPSK typically offers up to 1.8 Mbit/s peak data rates, while 16QAM offers up to 3.6. Additional codes (e.g. 10, 15) can also be used to improve these data rates or extend the network capacity throughput significantly.

• Data Throughput will be also depend on MS class which support 5,10 and 15 codes resp.

• CQI- Channel quality information may include carrier level received signal strength indication (RSSI) and bit error rate (BER). I

• Channel quality indicators are messages that are sent on a communication system (such as a mobile communication system) that provide the remote connection (e.g. base station) with channel quality information

Drive Test tool for drive

• Sony Ericsson C702 (capable of Scanning)• Sony Ericsson Z750i (capable of Scanning)• PCTel SeeGull LX WCDMA 2100• PCTel SeeGull LX Plus WCDMA 2100• Global Sat BU-353 (NMEA-0183)

• Garmin 10 Mobile Bluetooth (NMEA-0183)

Thanks……