Subch A/B Symbols

The Subch A Symbols and Subch B Symbols traces show the raw data for subchannel A and B in the analyzed burst, respectively, when the burst contains AQPSK modulation. When the Modulation Scheme is not AQPSK, these traces will be blank and show a NO DATA trace indicator.

These traces provide a way of looking at the detected symbol data for the AQPSK signal. AQPSK, which is just a modification of QPSK Quadrature phase shift keying, contains 2 bits per symbol. For the data in the Symbols trace, the I axis determines the most significant bit, while the Q axis determines the least significant bit. However, EDGE Enhanced Data for Global Evolution: A technology that gives GSMA and TDMA similar capacity to handle services for the third generation of mobile telephony. EDGE was developed to enable the transmission of large amounts of data at a high speed, 384 kilobits per second. (It increases available time slots and data rates over existing wireless networks.) Evolution uses the AQPSK modulation scheme to transmit two logical channels, A and B. Each 2-bit AQPSK symbol contains one bit for the A channel (the LSB Least Significant Bit: In a binary coding scheme, the bit having the least numerical value. Analogous to the units position in a decimal number. of the two bits, determined by the Q part of the signal) and one bit for the B channel (the MSB Most significant bit. In a binary coding scheme, the bit having the greatest numerical value. Analogous to the left-most numeric position in a decimal number. of the two bits, determined by the I part of the signal).

The Subch A Symbols trace contains just the bits for the A channel, so it shows 1 bit per symbol. Similarly, the Subch B Symbols trace contains just the bits for the B channel, and likewise shows 1 bit per symbol.