Understanding BER, BLER, and DBLER in GSM/GPRS Testing

BER, BLER, and DBLER are fundamental performance metrics in GSM and GPRS systems. These measurements determine the quality of the wireless link and whether a device or network is operating within acceptable performance parameters.

The standards define specific pass/fail criteria for BER, BLER, and DBLER at various Signal-to-Noise Ratios (SNR) for both traffic channels (TCH) and data channels (PDTCH or PDCH). The acceptable limits for these metrics vary depending on the GPRS modulation scheme used (CS1, CS2, CS3, CS4) and the EGPRS modulation and coding schemes (MCS1 through MCS9). The 3GPP standard provides detailed specifications for each scenario.

• BER: Bit Error Rate
• BLER: Block Error Ratio
• DBLER: Data Block Error Rate

Let’s break down what each of these represents:

• BER = (Erroneous bits / Total number of bits) x 100%
  • BER II = (Erroneous class II bits / Total number of class II bits) x 100%
  • BER Ib = (Erroneous class Ib bits / Total number of class Ib bits) x 100%
• FER (Frame Erasure Rate) = (Erroneous frames / Total number of frames) x 100%
• BLER = (Blocks received in error / Total number of blocks) x 100%
• DBLER = (Blocks with erroneous data fields / Total number of blocks) x 100%
• USF BLER = (Assigned USFs received in error / Total number of blocks) x 100%
• False USF Detection = (Unassigned USFs received in error / Total number of blocks) x 100%

BER Limit

For TCH/FS (Traffic Channel/Full Speed), class II bits have specific BER limits:

• Under static channel conditions, BER should be $\leq 10^{-4}$
• Under EQ50 channel conditions, BER $\leq 3\%$

This performance should be maintained up to an input level of -40 dBm in both static and multipath channel environments.

A BER of $10^{-3}$ needs to be maintained up to a level of -15 dBm for the GSM-900 band and -23 dBm for the DCS-1800 band.

These BER specifications vary based on receiver sensitivity levels:

• For DCS-1800 class 1 or class 2 Mobile Stations (MS), the limit is -100 dBm.
• For DCS-1800 class 3 MS, it is -102 dBm.
• For GSM-900 and small MS, it is -102 dBm.

The GSM 05.05 Version 5.0.0 standard provides comprehensive FER/BER limits for various channel types, including TCH/HS (Traffic Channel/Half Speed) and TCH/FS. Refer to table 1: “Reference sensitivity performance” in the standard for precise limits under different channel conditions.

BLER Limit

The BLER must be less than or equal to 10% for various GSM bands, including GSM 400, GSM 700, GSM 850, GSM 900, DCS 1800, and PCS 1900. This limit is defined in the Release 99 GSM 5.05 specifications.

PDTCH Reference Levels

The following table summarizes the reference levels for different PDTCH (Packet Data Traffic Channel) modulation coding schemes under static channel conditions:

Test and Measurement Equipment

This section outlines the test and measurement equipment used for evaluating device performance against WLAN, WiMAX, Zigbee, Bluetooth, GSM, UMTS, LTE, and other standards. This includes devices such as:

• Spectrum Analyzers
• Vector Signal Generators (VSG)
• Vector Signal Analyzers (VSA)
• Frequency Counters
• Protocol Analyzers
• Arbitrary Waveform Generators (AWG)
• Digitizers
• Function Generators
• Pulse Generators
• RF Network Analyzers
• Power Meters
• Logic Analyzers

BER Testing Equipment

Common manufacturers of BER testing equipment include:

• Agilent T&M Solutions
• Anritsu T&M Solutions
• Rohde & Schwarz T&M solutions

Other useful equipment:

• Wireless Channel Emulator
• Vector Signal Generator
• Vector Signal Analyzer
• Power Analyzer Equipments
• Protocol Analyzer