Module 3: Building nodes (hardware)

Section Length
1: Topic introduction 15 min
2: Hands-on and material exploration 40 min
3: Discussion and reflection activity 20 min
4: Wrap-up and week ahead 5 min
Workshop length 1:30 min

1: Topic introduction

  • Break apart the mesh node into its base modules and brief overview of each module’s role:
    • Single board computer
    • Storage (SD card) and software (OS)
    • Power supply
    • Radio (onboard and external)
    • Antennas
  • Review Homework from Module 2 (radio waves)
  • Introduce WiFi concepts as they relate to configuring the radio (frequencies, bands, bandwidth (40 MHz vs 20 MHz), SSID, etc)
  • Touch upon licensed and unlicensed frequencies (900Mhz, 2.4Ghz, 5Ghz), how they change from jurisdiction to jurisdiction, and the CRTC as the governing body in Canada.

2: Hands-on and material exploration

Group activity to wirelessly mesh with other groups by configuring Raspberry Pis.

Objectives

  • Learn to establish wireless links between nodes and manipulate the nodes’ radio properties
  • Understand the role that frequency, bands, bandwidth and SSIDs play in a wireless mesh
  • Allow opportunity for students to tinker with the radios and create a mesh
  • Discover first hand real-world problems with growing the mesh

Materials

  • A Raspberry Pi 3 for each member labeled with the SSID for the node
  • SD cards with pre-flashed images with all required software
  • Laptops that can establish a SSH session to each Raspberry Pi (each running a Host AP with unique SSID)
  • USB WiFi radio that is ad-hoc or 802.11s-capable for each Raspberry Pi 3

Format

  • Pairs to start, then work toward establishing a class-wide mesh

Activity

  • As a class review the purpose of each command in a sample starter script: 
      ip link set dev wlanX down
  iw wlanX set type mp
  ip link set dev wlanX up
  iw dev wlanX mesh join MY_MESH_NAME freq 2412
  ip addr add 192.168.0.Y/24 dev wlanX
  • Break into groups of two
  • Each group needs a pair of Raspberry Pis
  • Each group will connect to their Raspberry Pi’s Host AP and initiate a SSH session
  • Use ifconfig to identify which wlan interface is which (Hint: look for 10.0.0.1)
  • Use ifconfig and iw to create a mesh between the nodes with this sample starter script
  • Use iw wlanX station dump to see if connections are established
  • Use iperf3 -s on one node and iperf3 -c 192.168.0.Y on another node to test the speed across the link
  • Once the nodes are properly meshed, have groups seek out another group that has finished
  • Work together to integrate all 4 nodes into one mesh
  • Encourage group to continue to merge meshes until all the groups are meshed into one
  • End the group stage by discussing
    • Did you seek help with another group to mesh your first two nodes?
    • What where the barriers of connecting to another group?
    • How did you come to a consensus of mesh method, frequency, SSID, ip address schema? Build upon discussion in Module 2
    • Was it easier or harder to connect as the mesh got bigger?
    • Did we manage to mesh the whole class? Why, Why not?
    • Parallel the experience with the real world
      • Mesh locals working together
      • Coming to a consensus working in larger groups

3: Discussion and reflection activity

Q & A discussion around the different hardware we employ to build a network.

  • Discuss alternative components that could be used in a node for different applications and environments
    • SBC (Orange Pi Zero, Rock64, ExpressoBin, Raspberry Pi, etc.)
      • Price point
      • Processing power
      • Power consumption
      • Features (10/100 Ethernet, mPci-e, USB ports, etc.)
    • Power Supply (wall wart, POE, battery, solar panel, lamp post)
    • Storage and OS (OpenWrt/Lede, LibreMesh)
    • Radios
      • 2.4 Ghz vs 5 Ghz
      • Ubiquiti proprietary protocols meshed over Ethernet

4: Wrap-up and week ahead

  • Next session we will discuss important factors to consider for deployment and use a mapping activity of the nearby area for planning

Homework

In This Section

Module 3. Presentation slides

Module 3. PDF assets

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