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W-CDMA (Wideband Code Division Multiple Access) is used by the UMTS (Universal Mobile Telecommunications System).

UMTS's Magic Numbers
Property Value
Modulation/Access scheme W-CDMA
Channel bandwidth 5MHz
Chip rate 3.84MHz
Common pilot channel (CPICH) Fixed-rate 30 Kbps, spreading factor (SF) 256
Primary CPICH (CCPCH) 14 slots in one radio frame
CCPCH slot First 256 chips Tx OFF, then 18 data bits (20 bits/2560 chips in total)
CCPCH frame 10ms total duration


  • A great PDF that deals with many technical aspects of the air interface.


Calculated and displayed using the the Fast Auto-correlation block:

  • 3G UMTS at 2.1125GHz:


Strong peaks precisely on the 10ms grid line are indicative of the pilot channel.

There is also a smaller peak at ~0.7ms, which should be the repeating slot of the pilot channel (if you count the peaks correctly, the 14th 'harmonic' will land precisely on the first strong 10ms peak).

The peak at ~21/22ms requires further investigation, although it could be from an adjacent panel or cell (since they all use the same frequency). If you know, let me know!

  • Telstra NextG at 842.5MHz:

NextG FAC.png

The above waterfall plot shows bursty traffic on the downlink.