Hello.

In my phone specs says that it support: UMTS/HSDPA/HSUPA (850, 900, 1900, 2100 MHz).

At the wikipedia, I can read:

Uplink Downlink GSM-850 824.2 – 849.2 869.2 - 894.2

GSM 900: ------------------------------------------------

P-GSM 900 890,0 - 915,0 935,0 - 960,0 E-GSM 900 880,0 - 890,0 925,0 - 935,0 R-GSM 900 876,0 - 880,0 921,0 - 925,0

GSM1900: ------------------------------------------------

GSM 1900 1850,0 - 1910,0 1930,0 - 1990,0

More clearly(?): MHZ 1111111111 88888888888888888888999999999999999999990000000000 00112233445566778899001122334455667788990123456789 BAND: 05050505050505050505050505050505050505050505050505 GSM-850 : -----^^^^^----vvvvvv------------------------------ P-GSM 900: ------------------^^^^^^---vvvvvv----------------- E-GSM 900: ----------------^^^------vvv---------------------- R-GSM 900: ---------------^^-------vv------------------------

(^) means uplink, (v) downlink.

Posible overlap between bands:

SRC Band From To DST Band Hole size P-GSM 900 ----(890.0 - 894.2)---> GSM-850 | 4.2 MHZ E-GSM 900 ----(880.0 - 894.2)---> GSM-850 | 14.2 MHZ R-GSM 900 ----(876.0 - 880.0)---> GSM-850 | 4.0 MHZ

Can a phone, with a modified baseband firmware, transmit data to another phone directly, without BSS? Or are there any hardware limitation?

From https://gnuradio.org/redmine/attachments/115/all_gsm_channels_arfcn.txt

Source channel: Channel: 0; Band: EGSM-900 Uplink: 890 MHz, Downlink: 935 MHz Channel: 1; Band: GSM-900 Uplink: 890.2 MHz, Downlink: 935.2 MHz ... Channel: 20; Band: GSM-900 Uplink: 894 MHz, Downlink: 939 MHz Channel: 21; Band: GSM-900 Uplink: 894.2 MHz, Downlink: 939.2 MHz

Destination channel: Channel: 232; Band: GSM-850 Uplink: 845 MHz, Downlink: 890 MHz Channel: 233; Band: GSM-850 Uplink: 845.2 MHz, Downlink: 890.2 MHz ... Channel: 250; Band: GSM-850 Uplink: 848.6 MHz, Downlink: 893.6 MHz Channel: 251; Band: GSM-850 Uplink: 848.8 MHz, Downlink: 893.8 MHz

For example using a phone on channel 0 (GSM-900 band) to send a packet to a phone on channel 232 (GSM-850 band), using 890 MHz common frecuency.

I could't get any useful info about that.

Greetings. Rodrigo.