The Omni Scanner. Luke Berndt

Transcription

1 The Omni Scanner Luke Berndt

2 Game plan What I built Why I built it How it works Why it is useful Why its days maybe numbered Where it could go

3 DC Radio System DC s Fire & EMS have a digital 800MHz trunked sys Motorola SmartZone II - proprietary control channel, P25 CAI for the voice DC City services also on the system Channels span MHz MHz 11 voice channels + 1 control channel = lots of CPU Too wide for RTLSDR HackRF 8MHz & I7 Mac Mini and GR

4 OpenMHz.com Records and archives (almost) all of the radio traffic on the system Captures lots of metadata, including radio Unit IDs Streams new calls using WebSockets Integrates with Twitter Filterable

5 Motivation

6 Motivation Scanners for Trunked Digital radio system are expensive and complex Recording and Archiving is even tougher and usually only possible for single channel Transform stream of audio in to packets/snippets Bring the RF world to Social Media Trunking and Twitter are sort of similar

7 Trunking 101 Create private channels without permanently reserving physical resources Talkgroups are abstractions - a channel is assigned with each talkgroup transmission Talkgroups Channels A channel is dedicated for sending out control message and channel assignments

8 Approach Started from gr-smartnet code by Nick Foster Python based program that can record SmartNet II transmission Only works with Analog voice, DC is Digital Python was happy with multiple GnuRadio graphs running at the same time Moved to C++ and created a recorder that uses DSD to decode the Digital voice

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11 Gnuradio Program Decode New TG? Update Keep Alive Control Channel 5MHz Capture Decode Voice Store & Upload Active TG Thread Capture Decode Voice Store & Upload Inactive TG Thread

12 Dispatch Medical Holding Unit Main St. Elizabeth's Hospital - Maintenance/Motor Pool Fireground St. Elizabeth's Hospital - Ops Fireground St. Elizabeth's Hospital - Security Fireground 1A St. Elizabeth's Hospital - Ops Fireground St. Elizabeth's Hospital - Maintenance Fireground Department of Human Services Ops Fireground 2A Department of Health A3 Fireground A Office of the Chief Medical Examiner (OCME) A5 Fireground A Department of TransportaUon Traffic Control A6 Fireground 3A Department of TransportaUon A7 Fireground A Parking Enforcement A9 Fireground A Water and Sewer Authority A10 Fireground 4A Water and Sewer Authority 2

13 SmartNet Trunking Messages are 27 bits [ 16bits ID ][ 1bit Group Flag ][ 10bits Command ] Channel Grant - Assign a talkgroup a channel 508D G 308 DAD0 G 141 Channel Grant 141 I 508D -> G DAD0 Keep the channel assigned DAD0 G 141 Continuation 141 G DAD0 Affiliate a radio to the system 0B0D I A I 310 Affiliation I 0B0D -> G 065A

14 Control Chan Decode gr_freq_xlating_fir_filter_ccf digital_fll_band_edge_cc gr_pll_freqdet_cf A 0 Balint Graph! digital_clock_recovery_mm_ff digital_binary_slicer_fb gr_correlate_access_code_tag_bb smartnet_deinterleave smartnet_crc

15 Voice Channel Decode freq_xlating_fir_filter_ccf rational_resampler_base_ccf quadrature_demod_cf fir_filter_fff multiply_const_ff gr_dsd wavfile_sink Graph connected to NULL Source/Sink when not active Don t have have stop/start top block to add & remove voice chan recorders

16 System View Website Capture Decode Process Store Record Upload Web Socket Push App GnuRadio Web Server

17 Web Side Nothing special NodeJS & NGINX for the Server MongoDB for the DB to store call info Audio stored in static MP4 files Socket.IO library provides Web Sockets for polling for new calls Bootstrap for a responsive UI

18 The Benefit Transparency - make an opaque system accessible Give citizens a better sense of how well things are working Give journalists better additional sources to work with Allow for fact checking after an event

19 Challenges Jurisdictions are moving to more advanced Trunking - P25 Phase II OP25 is working on / has support FirstNET? Encryption! Do Citizens have a right to monitor non-sensitive communication by public officials? Linux + GnuRadio + Custom Program + RT = Pain Tough tracking down problems, upgrading systems Codecs - transcoding is dumb, IMBE -> MP4

20 PublicRecord Advanced Emergency Radio Scanner & Repository Selected for Knight Foundation Prototype funding Builds on open source OpenMhz code Collaborating with news outlets in MA, FL and WA Delivering an initial barebone system and then working with journalists to build UX

21 Analytics & Metadata Lots of data besides the audio - Handset joining, IDs Is it possible to sort all the calls and figure out which are the Important ones? Which ones are to & from your local Engine Co? Speech to text?

22 Links Website: ios App: id ?mt=8 GnuRadio Program: smartnet-recorder Web Code: