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Getting Started

Prepare

  • Raspberry Pi 3B+ with SD card (>=16GB), 2 pcs.
  • ALFA Netowrk's 802.11ah PiHAT module -- AHPI7292S, 2 pcs.
  • Antennas for 802.11ah frequencies, 2 pcs.
  • RPi images with NRC7292 drivers and tools for 802.11ah field tests
    • Halow_RPi_base.img (Default role: AP)

Network Topology

Installation

Step 1. Flash SD cards for RPi

First, we need to flash two SD cards with dedicated image, one for client and another for AP.

For common users, we recommand using Raspberry Pi's official tool, Raspberry Pi Imager, to flash the SD cards.

You can download the software here:

http://rptl.io/imager

and follow its step-by-step tutorial youtube video to flash SD cards:

How to use Raspberry Pi Imager

Step 2. Install SD cards to RPi and power on the devices

SD card insertion

Insert the SD card to Raspberry Pi's slot, and then power on the board by micro-USB power plug.

Step 3. Access RPi and update configuration

The RPi instance has static IP: 192.168.1.1 on ethernet port by default with ssh enable. Prepare a PC/NB with static IP in the same subnet, ex: 192.168.1.2, and access RPi via ssh and RJ-45 wire.

Default connection profile is:

Host 192.168.1.1
Port 22
Username pi
Password raspberry

After enter PRi via ssh, please edit /etc/nrc.conf file and update parameters to fit your testing scenario. Here list some frequently used parameters below:

country_code US
EU
JP
KR
KR-MIC
TW
channel See UG-7292-003-S1G_Channel.pdf to find proper channel index
role ap
sta

After changing /etc/nrc.conf, remember to execute nrc_reload command and reboot to apply configurations.

Step 4. Check the wireless network connections

Prepare two RPi instance throungh steps 1. to step 3., one for ap role and another for sta role. After setup and boot on RPi instances, they will broadcast WiFi SSIDs in following format: Halow_RPi_<MAC address last 6 characters> (ex: Halow_RPi_a1b2c3) with RPi's built-in WiFi.

The ap and sta RPi instances are expected to establish a wireless LAN through WiFi WDS mode:

Subnet 192.168.200.0/24
Server IP 192.168.200.1 (by ap role)
DHCP server on ap role
SSID Halow_RPi_<MAC address last 6 characters> (each instance has its own SSID)
SSID for 802.11ah Halow_world
WDS enable
Bridge config Built-in WiFi(802.11n), WiFi Hallow(802.11ah) are in the same LAN
(nrc0, nrc1, wlan0)
  1. Power on both AP, STA devices and wait around 1~3 mins to make sure AP and STA establishing the 802.11ah WDS mutual connection.
  2. Connect from a notebook(named as NB1) to AP device via 802.11n WiFi, it's expected notebook will get 192.168.200.x IP via DHCP automatically
  3. Connect another notebook(named as NB2) to STA device, it's expected NB2 will get 192.168.200.x IP via DHCP automatically
  4. Lookup IP address of both NB1 and NB2, and let them ping each other.

If ping tests OK, then 802.11ah wireless is confirmed to work properly.

Note

Remember to check your computer's firewall settings to make sure it allows ICMP packet send/recv. Some OSes (ex: Windows) block ICMP packets by default.

Configuration

How to change channel

At first, look into the Newracom's offcial document about 802.11ah channel list tables:

UG-7292-003-S1G_Channel.pdf

and find required parameters:

  • The target country, like: US
  • The target frequency band index, like: 116
  • The corresponding 2.4G/5G frequency, like: 5580

Update RPi's /etc/nrc.conf with new parameters and reboot to apply new configuration.

NOTES:

  • Channel index are not consistent among differewnt countries.
  • Need both [country_code, channel index] to resolve the target frequency

Channels test pass

bandwidth channel idx freq 2.4G/5G freq
4 116 926 5580
2 161 925 5805
4 162 910 5810

Channels test failed

bandwidth channel idx freq 2.4G/5G freq
2 2 903 2417
2 153 909 5765
2 160 923 5800

How to set MCS manually

Run commands below:

cli set rc off
cli test mcs 10

Change the value 10 to the target MCS value you want.

NOTE:

  • rc means "Rate Control". Need to turn off rate control before setting static MCS value
  • MCS value is in range from 0 to 7 and 10

How to test performance

AP's image has iperf3 server by default. Users can just run the following command on RPi for speedtest:

iperf3 -c 192.169.200.1

How to scan

sudo iw nrc0 scan

References