How our wireless bridge technology works
Access control signals, sent by radio
A wireless bridge sends the same access control signal a wire would send, over a radio link, out to a door or gate the wire can't reach. Your access panel stays where it is and keeps making every decision. The Aether RF radio is built for that job: small messages that have to arrive correct and on time, through walls, buildings and other radio traffic.
Built for access control messages
An access control message is small. A card read, a door command or a status update is a few bytes next to a video stream, and it has to arrive correct and on time.
Faster data, shorter reach
Wi-Fi, Bluetooth and many other familiar wireless technologies are built to move a lot of data quickly. Sending data more slowly generally lets a receiver pick out a weaker signal, which can extend how far a link reaches. A headline data rate tells you little about whether a credential will reach a gate at the far end of a lot.
The balance in the Aether RF radio
Aether RF designed its radio to send enough data for credentials, door commands and status reports, with a receiver that can pick out a very faint signal. The design balances how long each message takes to send against how reliably it arrives.
How the radio gets a message through interference
The Aether RF radio spreads each message into a pattern the receiver already knows, and it hops between 50 channels. Both help a message get through interference.
Spreading the message into a known pattern
The radio uses Direct Sequence Spread Spectrum, or DSSS. Each piece of data goes out as a longer, known sequence of short signal elements called chips, spread across a wider slice of the band. The receiver compares what arrives against the sequences it expects, so it can recover the data even when interference has damaged some of the chips, as long as enough of the pattern survives.
Hopping between 50 channels
The radio also moves its transmissions across 50 channels. Interference concentrated on one channel then affects only some of the transmissions. DSSS and hopping deal with interference in different ways, and together they help a link keep working near other equipment on the same band.
Recovery and security are separate steps
After the receiver recovers a radio message, Aether RF's application security checks that it's authentic, current and meant for that device before anything happens at the door.
Why the radio runs at 900 MHz
The Aether RF radio runs in the 902 to 928 MHz band, usually called 900 MHz. Signals at that frequency reach further, get through buildings better, and stay away from the 2.4 GHz band that Wi-Fi and Bluetooth use.
More signal left at the same distance
At the same distance, power and antenna gain, a 900 MHz signal loses about 8.5 dB less strength in open air than a 2.4 GHz signal. In calculated free-space terms, a link that reaches 100 meters at 2.4 GHz would reach about 267 meters at 900 MHz. Inside a building, that extra signal helps a link get through walls and doors.
Through and around buildings
Lower frequencies generally get through many building materials better than 2.4 GHz does, and they bend around obstacles, so some of the signal reaches a receiver that has no clear line of sight.
Away from Wi-Fi and Bluetooth
Wi-Fi and Bluetooth use the 2.4 GHz band, and microwave ovens put out interference there too. A 900 MHz link doesn't overlap that traffic, and DSSS and hopping handle interference inside its own band.
The KNECT radio
Every KNECT link runs in the 902 to 928 MHz band, spreads each message with DSSS, and hops across 50 channels.
What the power and sensitivity figures mean
A KNECT radio transmits at up to 1 watt, and its receiver can read a signal as weak as about −125 dBm. The gap between the two is the room a link has to work with. Distance, walls, cables and connectors each use up part of it, and whatever is left over is the link's margin.
Why more doors don't cost range
Every Endpoint links straight to the central unit, so range to each Endpoint stays the same however many are on the system.
| Band | 902 to 928 MHz, the unlicensed 915 MHz band |
|---|---|
| Spread spectrum | Direct Sequence Spread Spectrum (DSSS) |
| Channels | 50, with frequency hopping |
| Transmit power | Up to 1 W (30 dBm) |
| Receiver sensitivity | About −125 dBm |
| Antenna gain | 2.1 dBi |
| Topology | A star. Every Endpoint links directly to the central unit |
| Bluetooth | Bluetooth Low Energy on every KNECT device, for the KNECT Tech app |
| Operating temperature | −30 to 85 °C across the KNECT series |
The engineering behind these figures, including the link budget, is in the Aether RF radio whitepaper.
What happens when somebody badges in
The credential goes out to the access panel by radio, and the panel's answer comes back to the door the same way.
- 1Somebody presents a card, a fob or a code at the reader.
- 2The reader passes the credential to the KNECT Endpoint wired in beside it.
- 3That Endpoint sends it by radio to the Endpoint wired to the access panel.
- 4The panel makes the same decision it makes for a wired door.
- 5The panel's answer comes back by radio, and the Endpoint at the door switches its relay to release the lock or open the gate.
The two Endpoints are the same part. Switch 4 on each one sets whether it's the Central, wired to the panel, or the Remote, wired to the reader, and the two wire differently. Central and Remote wiring guide
The credential and the answer both cross the radio, so the radio's response time is part of how long the door takes to open. Aether RF designs its bridges so the person at the door gets a response that feels like a wired door.
How far a KNECT link reaches
A typical KNECT installation runs 500 to 2,000 feet through obstructions. Site conditions dictate where in that range yours lands, so measure it before you commit.
- What's between the units
- The same distance reaches further over open ground than through occupied housing or poured concrete. Walk the path between the two units as well as measuring the distance.
- Where the antenna goes
- A well placed antenna beats a stronger radio in a bad spot. On a One to Many system, the ARF Tether mounts up to 400 feet from the Gateway.
- A measured site
- At a build-to-rent community in Phoenix, two gates link to the panel from 1,100 feet away, through the rental housing. The Phoenix site plan
- Reading it on site
- Signal strength shows on the Endpoint itself and in the KNECT Tech app, so you have a reading from the actual site.
A range figure is only as useful as the conditions behind it. Line of sight figures often come from open ground and well placed antennas. A radio set up for longer range can also take longer to send each message, and on a bridge every credential makes a round trip, so a slower message means a slower door.
Send Aether RF the property and we'll help lay the system out. Product support is (602) 396-4186, weekdays 8:30am to 5:30pm Arizona time.
The panel decides, the bridge carries the signal
A wireless bridge carries the signal between a reader and an access panel. The credentials, the schedules and the logs all stay in the panel.
Use a bridge when there's a panel on site
- The panel stays where it is and keeps making every access decision.
- The bridge extends the system that's already there.
- The credentials, the schedules and the logs don't move.
- Each credential makes a round trip over the radio, out to the panel and back.
Use a controller when there's no panel
- There's no panel on site for a bridge to connect to.
- The system on site is being replaced.
- The job needs a controller that makes the access decision itself.
- Each KNECT Core Access controller decides locally, and keeps deciding through an internet or radio outage on the permissions it last synced.
KNECT Core Access (coming soon)
Why installers use wireless bridges
A wireless bridge replaces the cable run to a door or gate, which on most sites is the slowest and most expensive part of the job.
- No trenching or new conduit
- No trench across the drive, no opened wall, and no repair to conduit that has already failed once.
- The site stays open
- The entrance drive, the lobby and the loading dock stay in use while the link goes in.
- Jobs you can bid
- Retrofits, historic buildings, and finished sites where the owner won't let you cut the ground or the plaster.
Wiegand or OSDP
A wireless bridge has to speak the protocol your readers already use. Most readers in service today are Wiegand, and new specifications increasingly ask for OSDP.
Wiegand
The reader sends the credential to the panel one way. The panel answers on separate lines that light the reader's LED and sound its buzzer. Wiegand has been in the field for decades, and KNECT supports formats from 4 to 64 bit.
OSDP
OSDP runs both ways on one connection and can be encrypted. On a KNECT link, the Endpoint at the door or gate keeps an encrypted OSDP connection with the reader, and the Endpoint at the panel keeps its own encrypted connection with the panel. Between the two, the Endpoints translate the credential data out of OSDP and carry it over the radio.
| Product | Wiegand | OSDP |
|---|---|---|
| KNECT Endpoint | 4 to 64 bit | Built in |
| KNECT Gateway | 4 to 64 bit | With the KGW-H OSDP Hat |
| Wiegand Wave 150 | 4 to 64 bit | No |
The OSDP Hat mounts on top of the Gateway and covers its Wiegand terminals, so a One to Many system runs one protocol or the other.
Point to Point or One to Many
How many doors and gates the wire doesn't reach decides which KNECT setup you want.
| Doors and gates | The setup | How it works |
|---|---|---|
| 1 | Point to Point Two Endpoints, one at the panel and one at the door or gate. The pair links with the DIP switches on the units. | |
| 2–8 | One to Many A Gateway at the panel, an ARF Tether for its radio, and an Endpoint at each door or gate. Up to four per Gateway, and eight with two. |
Not sure which one you need?
Call Aether RF product support and describe the site: (602) 396-4186, weekdays 8:30am to 5:30pm Arizona time.