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WCDMA Measurements-UE,NodeB

This tutorial section on WCDMA (UMTS) basics covers following sub topics:
UMTS Tutorial  UMTS channels  measurements  PHY layer  TDD vs FDD PHY  RRC States  Security  Cell search  Bands  UARFCN  Frame 

This page describes WCDMA measurements as per 3GPP TS 34.121 from RF and baseband domain perspective for both UE and NodeB.

Circuit switched and Packet switched call need to be tested from UE to NodeB and vice versa. This is referred as Mobile Originated call(MO call) and Mobile Terminated call(MT call). This establishment of the WCDMA call is carried out by connecting UE with R & S CMW500 system simulator or Agilent 8960 system. Refer following links for MO and MT CS and PS call flow message details.

•  WCDMA MO MT Voice call
•  WCDMA PS data call

The call establishment confirms basic voice and data test. To perform RF and baseband testing 3GPP TS 34.12(FDD)1 and TS 34.122(TDD) UE specifications need to be followed. Conformance testing for NodeB is specified in 3GPP TS 25.141(FDD) and 3GPP TS 25.142(TDD).

WCDMA UE Transmitter measurements

1. Nominal maximum output power: It should be within tolerance is examined as per different bands and power classes.

2. Frequency error: The frequency offset between received RF modulated carrier frequency from NodeB and one transmitted by UE after necessary frequency correction is incorporated as commanded by NodeB.
•  The frequency error should not exceed +/-(0.1 ppm + 10 Hz).

3. EVM Another time domain measure of the performance of the WCDMA transmitter is EVM(Error Vector Magnitude). EVM gives estimate of modulation quality of the designed transmitter with the ideal WCDMA UE transmitter. To measure EVM,vector difference between reference signal and the signal under test is calculated as per following equation. For more refer EVM page.
•  Measured EVM should be less than or equal to about 17.5%

4. Peak code domain error(PCDE): Another measure of transmitter distortion is the Peak Code Domain Error. It is defined using mean value of error vector power spreaded over code domain power.

For UE to be tested, WCDMA system simulator should generate two coded channels with spreading factor of 4 and DPCCH. The PCDE should be 15dB below the transmit signal power.

5. Adjacent channel leakage ratio(ACLR) It measures how much adjacent power leaks from wanted band to the adjacent band. As per specifications , there are two ACLR levels defined one at 5MHz (about 33dB) and another at 10MHz (about 43 dB) .

6. Spectrum emission mask This is measure of the transmitter's RF power amplitude limits in addition to ACLR. The measurement is based on 30KHz and 1MHz bandwidths. The standard defines UE power density levels at these frequencies.

WCDMA Node B transmitter specifications

Transmit power: It is about 10-40 W in range and is varied manufacturer to manufacturer. Power control is about upto 18 dB and in the steps of either 1dB or 0.5dB. EVM: It is same for NodeB as specified for UE.

PCDE: It should be 33dB below the transmitted signal power for NodeB.

ACLR: It is the same measure as specified in UE part. The levels are different. ACLR performance levels are 45dB at 5MHz offset and 50dB at 10 MHz offset.

Spectrum emission mask: The mask varies based on the power amplitude from the transmitter. The masks are defined in the standard and vary from 31 dBm to greater than 43 dBm. The measurements are based on 30KHz and 1MHz bandwidths.

Spurious emissions: Any unwanted frequencies at the output of the transmitter is referred as spurious frequencies. The power emission limit for spurious is specified in the conformance requirement. For example, For 1920-1980 MHz (UTRA Rx Band I) the level is -96dBm with 100KHz measurement BW.

Receiver specifications for UE/NodeB

The receiver sensitivity,BER,receiver adjacent channel selectivity, dynamic range, receiver blocking specifications(inband/out-of-band), intermodulation requirements are the measurements carried out for both the WCDMA UE as well as NodeB testing.

Other than the normal Transmitter and Receiver measurements, radio characteristics viz. frame error rate,Signal to Interference ratio,Interference power are measured by the physical layer and reported to upper layers and to NodeB via messages. These measurements will help make decision in handover from one cell to the other. It also helps in selecting the right cell during the initial network entry procedure.

What is Difference between

Difference between TDD and FDD WCDMA physical layer
Difference between TDD and FDD

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