What is D-AMPS
D-AMPS uses 832 channels (in every direction) with three users sharing a sole channel. This allows D-AMPS to support up to the 2496 users simultaneously per cell. GSM uses 124 channels with eight users sharing individual channel. This permits GSM to support up to 992 users concurrently. Both systems use about same amount of spectrum (25 MHz in each direction). D-AMPS uses 30 KHz × 892 = 26.76 MHz. GSM uses around 200 KHz × 124 = 24.80 MHz. The dissimilarity can be mainly attributed to better speech quality provided by GSM (13 Kbps per user) over D-AMPS (8 Kbps per user).