Test Mode A vs. Test Mode B in GPRS/EGPRS

Test Mode A and Test Mode B, as defined in ETSI 44.014, are used for testing GPRS/EGPRS compliant mobile devices. Test Mode A is primarily for transmitter measurements, while Test Mode B is used for both transmitter and receiver measurements.

Key Differences

• Test Mode A: Focuses on transmitter characteristics.
• Test Mode B: Evaluates both transmitter and receiver performance.

Measurements Carried Out

• Test Mode A:

  • Power versus Time
  • Phase and Frequency
  • Spectrum (including modulation/switching characteristics)
  • Multislot measurements

• Test Mode B:

  • Bit Error Rate (BER)
  • Data Block Error Rate (DBLER)
  • Includes multislot measurements (similar to Test Mode A)

Equipment

A popular piece of equipment used for these measurements is the Rohde & Schwarz CMU200.

GPRS/EGPRS Test Mode A: Transmission Mode

This mode forces the mobile device into a transmission mode, using a specific Pseudo-Random Number (PN) sequence, like 2E9-1 PSR Bit Pattern.

This setup (using CMU200) allows detailed analysis of the transmitted signal.

GPRS/EGPRS Test Mode B: Loopback Mode

This mode sets up an internal loopback within the mobile device. Received data is transmitted back without modifications. This allows testing with different GPRS modulation and coding schemes (CS1 to CS4) and EGPRS modulation and coding schemes (MSC1 to MCS9). This is very useful for BER, BLER (Block Error Rate) and DBLER measurements.

In Test Mode B, the CMU200 sends blocks containing PRBS (Pseudo-Random Binary Sequence) data. It then compares this data with the data received back from the mobile phone to determine the BER. If the CMU200 detects bit errors in the received data block, it declares the block as invalid, thus calculating the DBLER.