Cell Phones

This page is devoted to cell phone-related topics. My end goal is to write a 3G demodulator from scratch so I can at least see the clear traffic like time of day, and I'll keep updating this page as I make progress.

Decoding

My first step is to positively identify a signal by finding a PSK constellation.

IS-95, however, is a 2G standard that only uses QPSK.

IQ Recordings

All of these signals are downlinks. That's all I'm interested in since downlinks are constant and dependable.

Please comment if you see that I've given a sample the wrong name.

Unless specified, recordings and pictures are of indoor reception and are 8 MHz wide. All were done using these TV rabbit ears from Target.

It should be noted that while IQ is usually not compressible, I can occasionally get ratios near 70% using 7-Zip. Therefore, I offer these as 7-Zip archives, saving myself between 20 and 50% on space and upload time.



CDMA 1xRTT (Voice/Texting)
Center Freq: 862.895 MHz
IQ Download, 741 MiB

Width: 2 MHz taken with 1.536 MHz IF filter
City: Hanahan, SC
Duration: 2m 14s

3G WCDMA
Center Freq: 1936.562 MHz
IQ Download, 752 MiB

Width: 6 MHz
Duration: 41.6 seconds
Unlike the bottom 3 that I recorded from home, this came from a large city and I'm positive it's WCDMA as it measured about 3.9 MHz. I used the SDRplay EXTIO option to do post-tuner DC compensation because the DC spike looked pretty bad. The power fluctuations are the tower dynamically changing its transmit power.

2G GSM
Center Freq: 1963.18 MHz
IQ Download, 214 MiB

Width: 1 MHz with 600 kHz IF filter
Duration: 2m 12s

7-Zip was able to take this from 505 to 214 MiB.

Maybe [e]CLR #1

Center Freq: 887.5 MHz
IQ download, 1.33 GiB

Maybe eCLR #2

Center Freq: 871 MHz

Some CDMA2000-related double signal, probably 3G EV-DO data (in which case there is no voice/texting)

Center Freq: 877.880 MHz
IQ download, 1.26 GiB