osmocom-bb-gprs-no-hw

Modified version of osmocom-bb project where I try add this features:

• Communication with BTS via UDP socket using GSMTAP headers
• Add GPRS support to osmocom-bb

For these purposes I create new application named bts_proxy (src/host/bts_proxy/src/proxy), which communicate with BTS and layer23/mobile application. I also created the BTS application (src/host/bts_proxy/src/BTS) which create and send GSM messages with GSMTAP header to the proxy application via UDP socket.

What already work in proxy application

• receive messages from BTS and layer23
• send L1CTL messages to the layer23
  • L1CTL_RESET_CONF
  • L1CTL_SIM_CONF
  • L1CTL_PM_CONF
  • L1CTL_FBSB_CONF
  • L1CTL_CCCH_MODE_CONF
  • L1CTL_DATA_IND

BTS

All messages are based on sniffed communication in based configuration for osmocom-bb (mobile phone with sim card) BTS send these messages:

• BCCH - system type information 3
• BCCH - system type information 4
• BCCH - system type information 2
• BCCH - system type information 2ter
• PCH - Paging request

Hints

• http://www.benkeser.com/obbphy.pdf
• http://www.sharetechnote.com/html/BasicCall_Voice_GSM.html