A Resilient Amateur Radio Digital Emergency Communications Network for Maine

A Resilient Amateur Radio Digital Emergency Communications Network for Maine Steve Hansen Richard Bates Donnie Dauphin KB1TCE WD1O WD1F April 23, 2019 Acknowledgements • Roger Pience N1XP • Jimmy White KC1ETT • Pete Thuotte N1ZRL • Our EMA Directors • And many more Outline • Introduction • How a packet network works – Node hardware and software – Features for resilience – Performance • How you can use the network – Client hardware and software – ElExample from recent MltiMulti‐CtCounty SET – Extending coverage with . HF radio . Win lin k RdiRadio‐EilEmail StSystem . Digital Traffic Network • Demonstration • Discussion Completing the Picture At last year’s conference we covered the Knox County Neighborhood HamWatch program. This year we are covering multi‐county, statewide, national and international emergency communications using Amateur Radio. Simplified Packet Network N1ZRL KB1TCE • N1ZRL connects to his home BBS to send a message to KB1TCE. • The system knows KB1TCE as KB1TCE@EOC.#KX.ME.USA.NA • Message is fddforwarded via one or more nodes. If a node is not available, the network will try to find an alternate path. • Nodes may have multiple functions e.g. node only, internet gateway for Winlink, BBS. Network as of March 2019 Windham and Libby Hill (Gardiner) are in progress. MEMA can connect via Lenfest Mtn. or Aborn Hill. Entry to the Canadian Maritime Packet Network (MARCAN) via New Brunswick and Nova Scotia. HF access is backup and also provides statewide access. The website http://nodemap.g8bpq.net:81/ automatically maintains a world‐wide map of internet‐connected BPQ network nodes Outline • Introduction • How a packet network works – Node hardware and software – Features for resilience – PfPerformance • How you can use the network – Client hardware and software – Example from recent Multi‐County SET – Extending coverage with . HF radio . Winlink Radio‐Email System . Digital Traffic Network • Demonstration • Discussion Packet Node Hardware using Raspberry Pi • Without Internet access, the real‐time clock enables secure over‐the‐ air administration using BPQAuth.EXE • Backup battery eliminates problems of SD card corruption due to power outages Packet Node Software BBS, node and gateway software developed by John Wiseman G8BPQ. Supports many HF and VHF/UHF modes. Versions are available for Windows (BPQ32), Linux (LinBPQ) and the Raspberry Pi (PiLinBPQ). Example of Console for node KX1EMA‐15 running PiLinBPQ current version node configuration file UHF and VHF ports initialised mail configuration file Features that give Resiliency • Moderate‐persistence CSMA/CR ‐ nodes that are polite and listen • Error‐detection in AX.25 ‐ corrupted frames are re‐transmitted • Automatic routing with NET/ROM ‐ adjust for changing propagation, node failures, etc Reference Model for Open Systems Interconnection (OSI) • Some applications, like packet radio apps, do not use all the upper layers Packet Radio Layers • AX.25 – derived from X.25, a 1970’s telecom’ protocol (users included ATM) • HDLC ‐ High Level Data Link Control • CSMA/CR ‐ Carrier sense multiple access with collision recovery • 1200 b/s uses old Bell 202 modem tones –1 = 1200 Hz & 0 = 2200 Hz Moderate –persistence CSMA/CR ElExample with radios A, B and C sending messages Conceptual CSMA/CR Performance with Persistence ALOHA: just send 1.0 p = 0.1 0.9 p = 1: send if idle 080.8 0.7 p < 1: send if idle p = 0.5 0.6 and x < p ghput uu 005.5 0.4 p = 1 Thro 0.3 Higher throughput is achieved 020.2 with moderate‐persistence, p ALOHA 0.1 (politeness) 0 Offere d Traffi c LLdoad Error Detection in AX.25 Flag Addresses & Control PID Information FCS Flag AX.25 Frame Structure • Flag ‐ 1 byte delimiter at beginning and end of each frame • Addresses (Sender and Receiver) & Control –typically 16 bytes • PID –Protocol Identifier, e.g. “no layer 3”, NET/ROM, TCP/IP • Information –up to N bytes in this packet • FCS –Frame Check Sequence, a 2 byte Cyclic Redundancy Check (CRC) The CRC is computed using at Transmitter and inserted into the frame At the Receiver the CRC is again computed and compared to what was sent If the two CRC numbers differ, a request is sent back to the Transmitter ‐ resend the frame 2 byte CRC can detect errors in up to 16 contiguous bits & others distributed across frame Principles of CRC for Error Detection • At the Transmitter the AX.25 frame is “divided by” a number Data Input using CRC‐16‐CCITT standard generator polynomial x16+x12+x5+1 • The Tx‐remainder is inserted into the frame as the FCS • At the Receiver the received data is “divided by” the same number • The Rx‐remainder is compared to the received FCS • If they differ, the Receiver requests the frame resent An Illustrative Analog with Decimal Numbers • Start with 30‐digit number 9876543210987654321098765432109876543210 • Diidivide by the number 19 to get a remaidinder 1 and transmit this as the FCS • Receiver gets 9776543211987654321099765432109876543220 • Divide by 19 to get a remainder 14 • Conclusion ‐ there are errors in the frame so request resend note: calculation done with large number calculator https://www.calculator.net/big‐number‐calculator.html Automatic Routing with NET/ROM Flag Addresses & Control PID NET/ROM Information CS Flag AX.25 Frame Structure with NET/ROM • NET/ROM is used for messages between nodes • NET/ROM is layer 3 –the Network Layer protocol –to accomplish routing • NET/ROM layer reduces the Information packet size by 20 bytes • Each node: • periodically announces its existence (FCC ‐ every 10 minutes) • creates a Neighbor list – nodes it can “hear” directly • creates a Destination list –nodes it has calculated it can hop to • periodically announces its Destination list (typically every hour) • The Destination list can have up to 3 routes to each node Neighbor & Destination Lists B A D C Nodes A, B, C & D Example: Destination Details from Node at St. George, ME to Yarmouth, NS N VE1YAR-1 Query: routes to node VE1YAR at Yarmouth KNXSTG:WD1O-15} Routes to: from node WD1O‐15 at St. George? #yar:VE1YAR-1 Response: routes to node VE1YAR‐1 198 5 4 KS1R-15 ‐ via node KS1R‐15 at Phippsburg ‐ quality 198 174 5 4 KX1EMA-15 ‐ via node KX1EMA‐15 at Rockland – quality 174 174 5 3 WD1O-5 ‐ via node WD1O‐5 at Lenfest – quality 174 Data File Used for Network Testing 50 names, phlhysical and email addresses, and phone numbers ~4 kBytes .CSV file ~ 2.5 kBytes compressed How Good is 1200 b/s Packet Radio? –delay waiting for idle channel – transmitter turn‐on delay Outline • Introduction • How a packet network works – Node hardware and software – Features for resilience – Performance • How you can use the network – Client hardware and software – Example from recent Multi‐County SET – Extending coverage with . HF radio . Winlink Radio‐Email System . Digital Traffic Network • Demonstration • Discussion User Configuration • Windows computer to run Winlink Express. • A hardware packet TNC or a sound card interface used with appropriate packet software. • VHF or UHF radio as needed. User Packet Software • Many options are available. We use Winlink Express bdbased on bdthbreadth of use and ftfeatures tha t support emergency communications. • Winlink Express: – Client software developed by the Winlink Development Team. – May be used for packet networks or with the Winlink radio‐ email system. – Functions with a broad set of ARQ modes for VHF/UHF packet and HF. – By default, uses Open B2F compression to minimize message size. – Accommodates text and binary file attachments. Winlink Express Main & Session Screens Main screen is set up like an email client. Session screen sets the mode and manages the connection. Example from Multi‐County SET January 26, 2019 Lenfest WD1O‐5 Rockland KX1EMA‐15 Rockland Whitefield EMA N1REX‐15 St. George Phipps burg WD1O‐15 KS1R‐15 Wiscasset EMA • Packet messages exchanged between the EMA Directors of Lincoln & Knox County • Sent by K1LX at EMA in Wiscasset, connecting to node KS1R‐15 in Phippsburg • Message automatically routed via node WD1O‐5 at Lenfest to node KX1EMA‐15 in RkldRockland (there was a alterna tive path via WD1O‐15 in St. G)George) • Message received at EMA in Rockland by KX1EMA Adding HF to the Network Hardware Configurations • Same software as for packet. • Compatible HF ARQ sound card modes include Winmor, ARDOP & VARA • Pactor (HF): Proprietary hardware (=$$$) but highest HF performance. HF for Extended Coverage • VHF/UHF packet is basi call y line of ssgight aadnd requires an infrastructure of nodes. • The network can be expanded by adding a limited number of HF ports. These can be accessed state (and region) wide using the same software and protocols. • Shou ld there be a filfailure of the VHF/UHF nodes, HF can help to fill the gap. • However, HF modes are slower than packet and any station can only accept one connection at a time. Packet Network with HF Ports Adding Winlink to the System What is Winlink? Winlink is a worldwide radio email service that uses radio pathways where the internet is not present. It is also capable of operating completely without the internet‐‐automatically‐‐using smart‐network radio relays. Winlink had its origins with the sailing community with email, position reporting and weather information. It now has a substantially broader role supporting emergency and disaster relief communications. Winlink also supports non‐ham governmental communications, one notable example being the SHARES (SHAred RESources High Frequency Radio Program) that is administered by DHS. The system is built, operated and administered entirely by licensed volunteers. Support for the system is provided by the Amateur Radio SftSafety FdtiFoundation, Inc., a US 501(c )(3) non‐profit, public‐bfitbenefit entity. Hardware Configurations for Winlink Same as before except that Winlink offers telnet as an option. Use if bandwidth is limited and the internet is available locally. Winlink System & Linkages “Radio‐Only” is ppyrimarily a backup if no internet connected RMS is available.

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