Module Three

# Module 3: Building a node

1. Recap from last week
			2. Parts of a node
			3. Radio frequency
			4. Meshing your nodes
			5. Building your own node
			6. Wrap-up & homework

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			# Recap from last week

**First Week**

Using Raspberry Pis, we _formed_ a .highlight[wireless mesh network].

**Last week**

Using Raspberry Pis, we configured a .highlight[wired network].

**This Week**

Using Raspberry Pis, we will _configure_ a .highlight[wireless mesh network].

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			class: center, middle

# Parts of a node

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## Single Board Computer

* All the components of a computer on one board
			* Components include processors, memory, storage, peripherals
			* Smart phone revolution modernized these types of computers
			* A node runs our software, processing signals and routing traffic

![Single Board Computer](slide-images/single-board-computer.svg)

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## Storage

* Many types of storage, each good for different reasons
			* Some properties to be aware of:
			  * **Format** - how the physical device works?
			  * **Speed** - how fast can it access and store data?
			  * **Capacity** - how much data can it store?
			  * **Endurance** - how long can it store the data for?

![Storage](slide-images/storage.svg)

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## Power supply

* Allow us to power the node
			* Consider what power you have available:
			  * Wall plug - city's power gird
			  * Batteries - stored power from another source
			  * Solar, wind, etc. - alternative sources

![Power Supply](slide-images/power-supply.svg)

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## Antenna

* Used to receive (Rx) and transmit (Tx)
			* Designed for specific frequency ranges and purposes

![Antenna](slide-images/antenna.svg)

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## Radio

* We use the 802.11 standard known as "WiFi"
			* Radios can come in many formats
			* They connect to an antenna

![Radio](slide-images/radio.svg)

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class: center, middle

# Radio & waves

Radio - the technology of using electromagnetic waves to carry information

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**Properties of waves**
			# Frequency

* Measured in Hertz (Hz), or cycles per second
			* We tune the radio to hear other people on the same frequency

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**Properties of waves**
			# Amplitude

* How much power the wave has
			* How loud we are talking

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**Properties of waves**
			# Polarity

* Which direction is the wave cycling
			* Orientation of the antenna is important

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**Properties of waves**
			# Phase

* The offset of peaks and valleys of two waves
			* You add the values at each point to calculate the new amplitude
			  * Two peeks or valleys - wave has double the amplitude
			  * A peek and a valley - amplitude closer to zero
			* Interference happens when waves bounce off walls

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**Properties of waves**
			# Channel width

* Defines how wide of a frequency band does the signal take up
			* Larger channel width:
			  * Provides more frequencies
			  * Allows for more data to be sent at once
			  * Is more susceptible to mode noise

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**Properties of waves**
			# Frequencies & channels

Channels - human defined numbers that point to a specific frequency

* There are 13 channels defined for WiFi
			* In Canada we can only use the first 11
			* First channel starts at 2.412 GHz (or 2,412 MHz)
			* The channels are spaced out by 5 MHz
			* Standard WiFi signals use a channel width of 20 Mhz
			* There are only 3 non-overlapping signals in the 2.4 GHz range (1, 6, and 11)

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**Properties of waves**
			# Licensing

* There are many frequencies coexisting in the air
			* Most of them are designated to a specific function
			* Government agency tasked with controlling them in Canada is the CRTC
			* 2.4 Ghz and 5.0 Ghz do not require any licensing
			* Used by many devices, such as microwave ovens, not just WiFi devices
			* They look like noise to WiFi devices

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			class: center, middle

# Meshing your nodes

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**Connecting with WiFi**
			# Infrastructure mode

Most common setup for WiFi:

* Router acts as an Access Point (AP)
			* Each device connects to it to communicate
			* Single point of failure, the router

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**Connecting with WiFi**
			# Mesh mode

There are two different modes that we can use to create a mesh:

* Independent Basic Service Set (IBSS)
			  * Also known as Ad-hoc
			  * Much older and more supported
			* Mesh Point (802.11s)
			  * A new specification
			  * Not many devices support this mode
			  * Many useful features

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**Connecting with WiFi**
			# Meshing in Linux

To mesh in Linux you issue the following commands:

* Turn off the interface:
			  * `ip link set dev <interface> down`
			* Switch to a mesh mode:
			  * `iw <interface> set type <mode>`
			* Turn on the interface:
			  * `ip link set dev <interface> up`
			* Join a group at a particular frequency:
			  * `iw dev <interface> <mode> join <group name> <frequency>`
			* Assign an IP address:
			  * `ip addr add <ip address>/24 dev <interface>`

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# Worksheet

* Break up into pairs
			* Configure the two nodes to mesh together
			* Assign IP addresses
			* Ping each IP address

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			class: center, middle

# Building your own node!

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			class: center, middle

# Wrap-up & Homework

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# Homework

Next session we will discuss wireless links more extensively, both theoretically and the practical aspects when configuring a wireless mesh network.

📝 [A quick tour of a mesh networking installation](https://www.youtube.com/watch?v=aLusYsScrv0) from the [Metamesh YouTube channel](https://www.youtube.com/channel/UCGEnntxbGKMU9J9GIZ1LQUQ)

_Optionally:_

- Read [Wireless Networking in the Developing World](http://wndw.net/pdf/wndw3-en/ch10-deployment-planning.pdf), Chapter 10: Deployment Planning
			- Watch [How to install a Smartrek wireless mesh network for sugar making purposes](https://www.youtube.com/watch?v=eKkVEeVNhm8)  (4:31)
			- Watch [Rural Next Generation Broadband Project](https://www.youtube.com/watch?v=QM7MUWDcNxk) (6:12)