Ubiquiti Wireless Backhaul (Point‑to‑Point)

This is my field guide for deploying a robust point‑to‑point (PtP) wireless backhaul. It covers link types, when to use each mode, channelization, alignment, and post‑install optimization. The goal is a stable, low‑latency link that survives real‑world noise.

Technologies & Concepts

• PtP Backhaul
• WDS Bridge
• Channel Planning
• Alignment & Fresnel Zone

Overview

A wireless backhaul is a Layer‑2 bridge between two locations. Unlike client Wi‑Fi, backhaul radios are dedicated to passing network traffic between sites, so design decisions (mode, channel, antenna, alignment) matter a lot more. These notes are vendor‑agnostic and apply well to Ubiquiti, MikroTik, EnGenius, and similar platforms.

Backhaul Link Types — When to Use What

• WDS Bridge (PtP): Purpose‑built backhaul. Radios pair by MAC and forward Layer‑2 transparently. Best choice for production PtP links.
• Client Bridge: One radio associates to an AP. Works, but less deterministic. Good for temporary links.
• Repeater/Extender: Same radio repeats and serves clients — halves throughput and adds latency. Avoid for backhaul.
• Mesh: Flexible multi‑hop fabric. Great for resiliency, but shared spectrum reduces capacity. For single PtP, WDS Bridge is cleaner.

Rule of thumb: Use WDS Bridge for PtP backhaul so the 5 GHz radio is fully dedicated to the link.

Recommended Topology (PtP)

Site A (Root)                    Site B (Remote)
┌──────────────┐             ┌──────────────┐
│  Router/SW   │             │  Router/SW   │
└───┬─────┬────┘             └───┬─────┬────┘
    │ LAN │                         │ LAN │
    │     └───[PoE]──Radio A◄──────►Radio B──[PoE]───
    │                          5 GHz, WDS Bridge
    └─────────────────────────────────────────────── L2
    

Keep the backhaul radio’s channel and power independent from any local access APs.

Planning & Site Survey

• Line of Sight (LoS): Avoid trees, buildings, terrain ridges.
• Fresnel Zone: Keep the first Fresnel zone mostly clear to prevent phase‑cancellation.
• Band: Prefer 5 GHz for PtP where allowed.
• Mounting: Rigid mounts, grounding, weatherproofing, and protected cabling.

Channelization & Power

• Static Channels: Fix the PtP link on a clean, DFS‑safe channel.
• Channel Width: Start at 40 MHz. Increase to 80 MHz only if SNR is excellent.
• TX Power: Use the minimum power that achieves target SNR.
• Access APs: Let client APs auto‑channel, but keep the backhaul static.

Physical Alignment

Perfect alignment is worth the time. Use live RSSI/SNR graphs at both ends and make small, alternating adjustments. Re‑check after thermal cycles or strong winds.

• Mount at final height and enable alignment mode.
• Aim for the center of the main lobe — avoid side‑lobe peaks.
• Secure cabling to prevent sway and strain.

Configuration Checklist (Root & Remote)

• Set both radios to WDS Bridge (PtP) and pair via MAC.
• Lock a static 5 GHz channel and width.
• Use strong WPA2/WPA3 keys.
• Disable unneeded services (client access, SSIDs).
• Assign static management IPs on your infrastructure VLAN.
• Enable watchdog/ping‑reboot only after validation.

Optimization After Turn‑Up

• Record baseline RSSI/SNR, MCS, throughput.
• Perform channel scans during peak hours.
• Verify latency/jitter — aim for stable single‑digit ms.
• Re‑run optimizers when adding nearby links.

Troubleshooting & Hardening

• Interference: Reduce width, change channels, lower TX power.
• Multipath/Fresnel: Increase height or re‑aim.
• Throughput dips: Check PoE, connectors, link speed/duplex.
• Weather: Inspect seals, drip loops, and UV protection.

What “Good” Looks Like

• Consistent SNR and RSSI with minimal daily swing.
• Stable MCS rates at chosen channel width.
• Low packet loss and jitter under load.
• Clean logs — no frequent DFS hits or re‑associations.

Feedback Welcome

Have tips to improve link budget, channel plans, or alignment techniques? I’m iterating this playbook based on real deployments.