What Is Fixed Wireless? Bridges, Signal Power, and Internet Links

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The short answer to what is fixed wireless is an internet or data connection that uses a radio link between fixed locations instead of a physical cable. A provider may connect a customer-premises radio to a tower, while a business may use two directional radios to extend an Ethernet network between buildings.

These systems share radio fundamentals but are not interchangeable. Provider access links connect a site to an internet service network; a local Wi-Fi-to-Ethernet bridge connects two customer network segments. Both require suitable spectrum, antennas, signal levels, and enough link margin for the selected data rate.

What is fixed wireless? Provider access versus mobile cellular

A fixed wireless link has two intended endpoints that remain in known locations. One endpoint is commonly mounted on a tower or provider facility, and the other is installed on a building, pole, or rooftop. Each endpoint contains a radio, an antenna, and usually an Ethernet port or network interface.

In a fixed wireless internet service, the customer-premises equipment receives the provider’s radio signal and presents an Ethernet handoff indoors. A router can then provide local wired and Wi-Fi connectivity. The provider may use a point-to-point link between two radios or a point-to-multipoint system in which one sector antenna serves multiple customer endpoints.

Fixed wireless can operate in licensed microwave bands or in unlicensed spectrum such as portions of the 5 GHz and 6 GHz ranges. The appropriate band affects range, interference, channel width, antenna size, and regulatory limits. Directional antennas concentrate energy toward the other endpoint, improving range and reducing unwanted reception from other directions.

Mobile cellular service is designed for moving devices. A phone or modem can change from one cell site to another through handoffs, and the network manages many subscribers across a coverage area. A conventional fixed point-to-point wireless link instead uses two deliberately aligned endpoints and normally does not support roaming between sites.

The distinction is based on network design and use, not only on the radio technology. A 4G or 5G provider can offer fixed wireless access to a home using a cellular network, even though the underlying system also supports mobile devices. Conversely, a licensed microwave connection between two buildings is fixed wireless without being a cellular service.

How a Wi-Fi-to-Ethernet bridge carries Ethernet between fixed endpoints

A Wi-Fi-to-Ethernet bridge uses radio to carry network traffic between a wired Ethernet network and a remote wired or wireless network. In a basic building-to-building arrangement, one bridge radio connects by Ethernet to a switch at the first site, and a second radio connects by Ethernet to a switch at the second site.

  1. Connect the local endpoint. A switch, router, camera system, access point, or other Ethernet device connects to the first radio.
  2. Transmit the frames. The first radio converts the network traffic into radio transmissions using a configured channel, modulation scheme, antenna, and security settings.
  3. Receive and forward. The remote radio decodes the transmission and sends the recovered Ethernet frames through its Ethernet port to the remote switch or device.
  4. Configure the network role. A transparent bridge normally extends the same Layer 2 network across the link. A routed wireless system instead uses IP interfaces and separate subnets at the two ends.

The two radios need compatible operating modes, matching channel settings, suitable encryption, and correct network configuration. Directional units must also be aligned so their main antenna beams face each other. An Ethernet handoff may carry a single VLAN or several tagged VLANs, depending on the bridge hardware and the network design.

A consumer Wi-Fi extender is not equivalent to every fixed-wireless bridge. An extender usually repeats a household access point so client devices can connect from a greater indoor area. It may use an omnidirectional antenna, share airtime between the client and upstream links, and be designed for short distances. A fixed bridge is intended to connect network locations, often with directional outdoor radios and a planned radio path.

Provider access equipment is different as well. The provider controls the tower-side radio, subscriber authentication, service profile, and connection to the provider network. A customer-owned bridge normally transports the customer’s Ethernet traffic between two sites and does not itself provide internet service unless one end connects to an active internet router or provider handoff.

How to convert dBm to watts and calculate link margin

dBm expresses power relative to 1 milliwatt, while watts express absolute power. The correct conversions are:

  • Watts from dBm: P(W) = 10^((P(dBm) – 30) / 10)
  • dBm from watts: P(dBm) = 10 × log10(P(W) × 1000)

Useful reference points include 0 dBm = 1 mW = 0.001 W, 10 dBm = 10 mW = 0.01 W, 20 dBm = 100 mW = 0.1 W, and 30 dBm = 1 W. Negative dBm values represent power below 1 mW. For example, -30 dBm equals 0.001 mW, or 0.000001 W.

Transmit power is only one part of a link budget. A simplified received-power calculation is:

Received power = transmit power + transmit antenna gain + receive antenna gain – path loss – other losses

All terms in this equation are expressed in dB or dBm. Antenna gain is added because an antenna concentrates energy in a direction. Cable, connector, radome, polarization, and implementation losses are subtracted. Free-space path loss increases with distance and frequency, so a longer or higher-frequency link generally requires more antenna gain, more transmit power within legal limits, or a lower data rate.

Consider a sample point-to-point link with 20 dBm of transmit power, 23 dBi antennas at both ends, 120 dB of path loss, and 4 dB of combined cable and connector loss:

20 + 23 + 23 – 120 – 4 = -58 dBm

The predicted received signal is -58 dBm. Converting that value gives approximately 0.00000158 W, or 1.58 microwatts. The small watt value is normal for a radio receiver; dBm is usually more convenient for comparing wireless signal levels.

Noise is the unwanted radio energy present in the receiver’s channel. If the measured or predicted noise floor is -90 dBm, the sample link has a signal-to-noise ratio of approximately 32 dB:

-58 dBm – (-90 dBm) = 32 dB SNR

The radio also has a minimum receive level, or sensitivity, for each modulation and channel-width setting. If the selected mode requires -75 dBm, the link margin is:

-58 dBm – (-75 dBm) = 17 dB of margin

Link margin is the amount of additional loss the connection can tolerate before it reaches the required receive threshold. It accounts for effects such as rain, foliage movement, interference, alignment error, and hardware variation. A higher data rate usually has a less sensitive threshold, so changing modulation or channel width can reduce the available margin even when the antennas and distance remain unchanged.

How to evaluate antennas, spectrum, and line of sight before deployment

Start with the required distance, throughput, availability, and Ethernet design. These requirements determine whether a short unlicensed bridge, a high-gain licensed microwave system, or a provider access service is appropriate. Confirm whether the link must transport one network, multiple VLANs, or routed traffic before selecting bridge hardware.

  • Verify endpoint locations. Record the mounting height, coordinates, cable route, power source, grounding method, and physical access at both ends. A clear view from one roof to the other is helpful but does not prove that the radio path is clear.
  • Check line of sight and the Fresnel zone. Trees, buildings, terrain, and even water tanks can block or reflect radio energy. The first Fresnel zone is an oval region around the direct path; keeping roughly 60% of that zone clear is a common planning target. At longer distances, account for the Earth’s curvature and seasonal foliage.
  • Select the antenna pattern. High-gain directional antennas can improve the link budget, but their narrow beamwidth makes alignment more demanding. Match antenna polarization at both ends and use mounting hardware that resists movement in wind.
  • Survey the spectrum. Look for competing networks, radar or other incumbents where applicable, and adjacent-channel energy. A wider channel may increase peak throughput but also captures more interference and may require a stronger signal.
  • Calculate the link budget. Include transmit power, both antenna gains, feeder and connector losses, path loss, expected interference, and receiver sensitivity. Check the resulting received level, SNR, and fade margin at the intended modulation.
  • Allow for installation loss. Long coaxial cable runs can remove much of the antenna gain advantage. Outdoor Ethernet radios with Power over Ethernet can reduce cable loss, but surge protection, weather sealing, grounding, and cable ratings still require attention.

A link that works at close range during installation may still fail after foliage grows, interference changes, or heavy rain affects a higher-frequency path. The deployment is ready when both endpoints have a stable, correctly aligned path, the measured received level is close to the design prediction, and the available margin supports the required throughput rather than only a basic association.