VAMOS

VAMOS allows multiplexing of two users simultaneously on the same physical resource in the circuit switched mode both in downlink and in uplink, using the same timeslot number, ARFCN and TDMA frame number. Hence, a basic physical channel capable of VAMOS supports up to 4 TCH channels along with their associated control channels (FACCH and SACCH).

A pair of TCH channels along with their associated control channels sharing the same timeslot number, ARFCN and TDMA frame number is referred to as a VAMOS pair. Up to 2 VAMOS pairs can be supported by a basic physical channel capable of VAMOS. The TCH channels along with their associated control channels in a VAMOS pair are said to be in VAMOS mode and are referred to as VAMOS subchannels. In a VAMOS pair, each VAMOS subchannel shall be assigned a training sequence which is different from the training sequence assigned to the other VAMOS subchannel in that VAMOS pair.

The test set support VAMOS test by combine a real MS and a fake MS into a VAMOS pair for downlink signal modulation. For the real MS, all call processing and test is normal. For the fake MS, the test set will simulate the link with PRBS data. New TSC set is introduced for support the VAMOS pair. Currently the test set allows VAMOS pair to take TSC value in the same TSC set or different TSC sets. In the downlink direction, the test set modulate the signal with AQPSK during VAMOS transmission.