Wireless Bridges for CCTV: Linking Gates and Far Buildings

What a wireless bridge is

A wireless bridge is a pair of outdoor radios that act like an invisible network cable. One radio sits near your NVR or network switch, the other at the far location, and they point at each other. Cameras at the far end plug into a small PoE switch there, and their video travels across the link as if it were wired.

This is not the same as Wi-Fi cameras. A bridge is a dedicated link between two fixed points, uses directional antennas, and is set up so nothing else can join it. It is common in factories, farmhouses, large campuses and apartments where the main gate is across a road or a long driveway from the security room.

When a bridge makes sense

• The far point is more than 100 m away and trenching for fibre would mean digging up roads, lawns or paved yards.
• A public road, a neighbour’s land or a nala lies between the two buildings.
• The site is rented and the owner will not allow digging.
• You need cameras working quickly, for example at a construction site or during an event.
• A temporary building, such as a site office or godown, may be moved later.

Distance, line of sight and bandwidth

Line of sight matters more than distance

The two radios must see each other with clear space around the straight line between them, not just a narrow gap. Trees, water tanks, new construction and even a parked truck can weaken the link. In Bangalore, trees growing through the monsoon are the most common reason a link that was perfect in March is unreliable by August. Mount radios high on a pole or parapet, above the tree line where possible, and plan for growth.

Plan bandwidth with headroom. A 4 MP camera on H.265 uses roughly 2 to 4 Mbps; eight such cameras need about 30 Mbps, and a bridge rated at 100 Mbps may only deliver half that in real conditions. Leaving at least 50% spare keeps playback smooth when someone watches live while the NVR records.

Power, weather and lightning

• Each radio is powered by PoE from the switch or an injector; the far end also needs power for its own switch and cameras.
• Use outdoor-rated radios (IP65 or better) and outdoor shielded cable for the short run to the radio.
• Earth the mast and add surge protection on the cable entering the building; tall masts attract lightning.
• Put the far-end switch on a small UPS so the cameras keep recording in a power cut.

Bridge or cable?

Where you can trench, fibre is still the most reliable choice and needs almost no maintenance. A bridge is cheaper and quicker to install, but it needs periodic checks of alignment and line of sight. Many sites use both: fibre to the main buildings and a bridge for the one gate across the road.

Worked example

A factory in Bommasandra has its main office and NVR at the front and a scrap yard and rear gate 320 m away across an internal road with heavy truck movement. Trenching meant breaking the concrete road. We fitted a pre-paired 5 GHz bridge on 4 m masts at both ends, with a PoE switch and a small UPS at the rear. Six 4 MP cameras at the rear gate and scrap yard now record on the main NVR, using about a third of the link’s measured capacity.

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