WiFi System

The radio shack and farm are in a rural area with only power lines and traditional copper telephone lines available for utilities.  Originally, the 2 GHz WiFi local access system was connected to an HDSL modem providing 6 Mbps Down-Link (DL) and 400 kbps Up-Link (UL) service over the copper telephone lines.  Later, 5 GHz WiFi was used to make a 1.1 mile connection to a remote house with broadband cable Internet service.  DL rates of over 60 Mbps and UL rates of over 15 Mbps are achieved over the remote WiFi link.  The Internet service subscription is for 75 Mbps DL and 15 Mbps UL, but actual provided rates are 10 to 15% higher.  Possible rates at the radio shack are limited by the provided subscription rates.

The WiFi system supports web access for a primary desktop PC permanently located in the radio shack with a direct connection to the 5 GHz remote access system.  This provides as high as 67 Mbps DL and 18 Mbps UL performance.  Any laptops brought to the shack can access the Internet over the 2 GHz bridge.  The 2 GHz bridge also provides remote access for a smart thermostat and power outlet for HVAC in the shack.  The speed achieved over the 2 GHz bridge is about 15 Mbps for both the DL and UL which is limited by repeating the Internet packets in the 2 GHz bridge on a 20 MHz only channel.  Direct access on the 2 indoor 2 GHz AP’s in the house and primary outdoor 2 GHz AP supports up to 50 Mbps DL and 16 Mbps UL.

The Radio Shack is situated behind a large metal farm equipment shed relative to the house, so a WiFi bridge  is used to forward the 2 GHz WiFi signal around the large metal shed.  The WiFi bridge is mounted in a plastic can for protection, and 110 VAC is connected to the nearby equipment shed.   To maximize concurrent access performance, the 2 indoor AP’s are configured on non-overlapping channels 6 & 11.  The outdoor AP and bridge operate on a third non-overlapping channel 1.

The radio shack is the smaller building in the center of the picture behind the large metal shed.  The WiFi bridge for 2 GHz local access is on the pole to the right.  The taller wooden pole in the center is the bridge for the 5 GHz remote WiFi access to the Internet via a cable connection.

The 2 GHz outdoor AP is the taller unit to the left mounted above the rear roof line of the house, and the lower unit to the left is the client for the 5 GHz remote access system serving the routers/AP’s in the house.

The link for remote access to the Internet is over 1 mile long.  WiFi units with directional antennas are used to achieve acceptable signal levels.  Since the home is located down a hill from the radio shack,  a bridge is also used in the remote access system.  The bridge has line-of-sight (ignoring a few tree tops) to the remote AP connected to the Internet as well as line-of-sight to the 5 GHz outdoor clients at the house and at the radio shack.  To avoid conflict with the local access system, the remote access system uses 5 GHz.  Channel 157 is used for the 5 GHz system.

At the remote access site, an existing tower once used for analog TV holds a WiFi AP with a dish antenna pointing towards the bridge 1.1 miles away near the house and radio shack.  Located at about 8 feet of height on the tower is a weatherproof equipment box.

The equipment box contains the cable modem, a router, and a power-over-Ethernet unit to feed data and power together to the AP at the top of the tower.  The weatherproof equipment box is equipped with vents and a fan controlled by a thermostat to avoid overheating.

 

A smart WiFi Honeywell thermostat for the radio shack can be controlled from anywhere with web access on a smartphone.  It is connected with a 24 VAC transformer for power and a contactor (relay) which sends 110 VAC power to a 1500 watt baseboard heater when needed.  This allows me to warm up the radio shack an hour or so before arriving.  I can also monitor the temperature in the radio shack remotely.  The Intermatic device is a surge protector connected to the electrical distribution box to protect against lightning surges on the power lines.  In addition, I have a WiFi controlled outlet for a secondary milkhouse 1500 watt heater to help warm up the shack in very cold weather (it also can be controlled remotely).  During the summer, this outlet powers an air conditioner which allows remotely starting the cooling for the radio shack on warm days.

A number of cameras are connected to the WiFi system for security and monitoring farm operations around the buildings.

WiFi Equipment and Configuration Details

The 5 GHz Remote Access System using tp-link equipment

– The AP and bridge are CPE610’s

– The 2 clients are CPE510’s

– The router is a TL-R600VPN

The 2 GHz Local Access System using tp-link equipment

– The AP’s are TL-WR940N’s

– The outdoor AP is an EAP110

– The bridge is a WA855RE

Hints:

– Configure security for WPA-PSK/WPA2/AES for good protection and to avoid speed limitations that happen in older security modes.

– Configure each unit for the desired operating mode (AP, client, bridge) and parameters via a direct connection to a laptop per the manuals.

– The RTS parameter was set to 100 bytes threshold for the 5 GHz units to trigger RTS/CTS operation for normal large packets.  Since the clients and AP can not “hear” each other, hence the bridge,  the WiFi Listen-Before-Talk protocol is compromised.  RTS/CTS operation provides a means to mitigate this problem, but the default setting disables RTS.  Setting this to 100 bytes will cause it to trigger under significant traffic situations.

– disable short GI (Guard Interval) operation due to outdoor operation with significant radio signal dispersion and fading.

– Disable DHCP in all units except the router at the cable modem.  This results in a single DHCP.

– Use strong passwords on the radio links for security.

– Setup the entire system at one place and test it for proper operation before installing the units outside.