HSDPA Block Error Ratio Measurement Description

Last updated: January 16, 2009

This section is only applicable to the lab application or a test application with the required feature license.

How is an HSDPA Block Error Ratio Measurement Made?

The HSDPA block error ratio (BLER) measurement can only be performed on a Radio Bearer Test Mode connection with a Channel Type of12.2k RMC + HSDPA or 12.2k RMC + HSPA. To perform the HSDPA BLER measurement, the test set sends blocks of data to the UE on the downlink HS-PDSCH(s). The data sent on the downlink HS-PDSCH(s) is determined by the HS-DSCH Data Pattern setting (or FDD Test "HS-DSCH Data Pattern" inFDD Test Operating Mode ). The test set then monitors the positive acknowledgments (ACKs) and negative acknowledgments (NACKs) sent by the UE on the uplink HS-DPCCH.

The UE is required to respond to every block of data directed to it with either an ACK or NACK. If it does not respond to a block in its assigned TTI, the test set logs the event as a statistical DTX (statDTX). Also, if the UE responds to a block with data other than all 1s (ACK) or all 0s (NACK), the TTI is treated as a statDTX. StatDTXs are considered block errors, and are included in the BLER calculation. You can specify how the test set responds to statDTXs using the statDTX Reception Behavior setting.

In addition to ACK/NACK information, the uplink HS-DPCCH also carries channel quality indicator (CQI) information. The test set analyzes the CQI values sent by the UE and reports the Median CQI .

FDD Test Mode Considerations

InFDD Test operating mode the test set does not provide radio bearer setup control of the UE. You must configure the UE to synchronize to the test set, demodulate the downlink HS-SCCH and HS-PDSCH channels and generate the appropriate uplink HS-DPCCH (see Synchronizing the UE to the Test Set's Downlink to Make Measurements ).

Once the UE begins transmitting its HS-DPCCH, the test set requires a finite amount of time to acquire and decode the UE's signal. If you initiate the HSDPA BLER measurement while the test set is still acquiring the UE's signal, the measurement will report statDTXs until it finishes its acquisition and begins demodulating the HS-DPCCH. To avoid an incorrect HBLER result, it is recommended that you wait approximately 2 seconds after the UE begins transmission of its HS-DPCCH before initiating the HBLER measurement (the amount of time required varies depending upon your test configuration).

HSDPA Block Error Ratio Measurement Parameters

Number of blocks to test
Sets the number of blocks to test during the measurement.

Note, the time for the measurement to complete increases linearly with theNumber of blocks to test . The test time (in seconds) is determined by:

(It takes six sub-frames (0.012 s) for a block sent to the UE by a HARQ process to be acknowledged at the test set).
Trigger Arm: see Trigger Arm (Single or Continuous) Description .
Measurement Timeout
See Measurement Timeouts . If you setMeasurement Timeout toOn , ensure that theMeasurement Timeout value is greater than the time the measurement needs to measure the desired Number of blocks to test .

The trigger source for this measurement is always protocol-based (see Trigger Source Description ).

HSDPA Block Error Ratio Measurement Results

Block Error Ratio
3GPP TS 34.121 F.6.3.2 defines the HSDPA block error ratio as:
Information Bit Throughput (kbps)
This result reports the data throughput of the HSDPA connection. 3GPP TS 34.121 F.6.3.1 defines Information Bit Throughput R as "the sum (in kilobits) of the information bit payloads (excluding the 24-bit HS-DSCH CRC) successfully received during the test interval, divided by the duration of the test interval (in seconds)."

Each time the test set receives an ACK from the UE, it increments a counter called "totalBits" by the size of the data block (in bits) that was positively acknowledged. Each time the test set transmits a data block on the HS-PDSCHs, it increments a counter called "blocksTransferred" (a transmission of a new block of data or retransmission of an old block of data both count as a block transmission). Each time the test set does not transmit a block in a TTI it increments a counter called regDTX.

Throughput (in kbps) is then calculated as follows:
ACKs
Number of positive acknowledgments received.
NACKs
Number of negative acknowledgments received.
statDTXs
Number of statistical DTXs received .
Blocks Tested
Blocks tested is the number of blocks that were tested in determining theBlock Error Ratio ,Information Bit Throughput ,ACKs ,NACKs ,statDTXs andMedian CQI .
Median CQI
The test set monitors the CQI values reported by the UE, then:
1. Generates a CQI frequency distribution (number of occurrences of each CQI value)
2. Generates a cumulative CQI frequency distribution (total number of occurrences at or below each CQI value)
3. Determines the median value of the cumulative CQI frequency distribution (determines which CQI value is above the (n-1)/2 occurrence point, where n is the total number of CQI occurrences).
This value is theMedian CQI , as specified by 3GPP TS 34.121 9.3.1.4.2 step 4.

For example:
CQI frequency distribution (frequency/CQI): 1/10, 3/11, 5/12, 4/13, 2/14
Cumulative CQI frequency distribution (cumulative freq/CQI): 1/10, 4/11, 9/12, 13/13, 15/14
TheMedian CQI value occurs at (15-1)/2 = 7 occurrences, which lies between a CQI value of 11 and 12. TheMedian CQI value in this example is thus 12.
Integrity Indicator

HSDPA Block Error Ratio Measurement Input Signal Requirements

The expected power into the test set must be set in order to maintain the link with the UE. This is done using the UE Target Power setting or by using manual receiver power control and specifying the expected power level. See Receiver Control .
Frequency: 800 to 1000 MHz, 1700 to 1990 MHz
Input level: -61 dBm to +28 dBm