Fi‑Wi Indoor Fiber to Wireless

Doing what’s thought impossible: scheduling 802.11 transmissions over unlicensed spectrum, so an operator can deliver low latency and responsiveness indoors.

One building-wide concentrator, fiber out to abundant 802.11 radio heads, and abundant inexpensive radio sensors that continuously measure the wireless hops. Scheduled centrally, on commodity silicon using unlicensed spectrum. It serves the tens of billions of Wi‑Fi devices already deployed.

Fi‑Wi architecture: a concentrator, a fiber plant, abundant radio heads, abundant sensors.

The fiber plant is the durable asset: installed once, it serves the building for decades, to 1 Terabit/sec and beyond. The radio heads and the sensors are the replaceable parts, inexpensive and swapped as standards move; the heads keep their 802.11 MAC and PHY and stay standard on the air. The concentrator is where the intelligence lives, and it does two things. First it makes each domain schedulable, deciding every transmission in time, in frequency and in space: which head sends, in which slot, on which allocation, and how transmissions are kept spatially separate. One entity deciding service order is what gives a queue there any meaning. Then it marks. It holds every payload in its own DRAM, one bottleneck queue per scheduled domain, and marks ECN on each, so senders back off before they build.

The fronthaul is PCIe extended over fiber: the concentrator builds the descriptor rings, the head starts the DMA, and the aggregate is pulled straight out of that DRAM and streamed through a small speed-matching FIFO to the air. The payload rests nowhere else, so bufferbloat has no second place to form. That is what lets L4S and other ECN-based congestion control work across the wireless hops.

The Sonde sensors see what humans cannot. They capture passive radiotap telemetry at the points where signals land and from where they originate. The Fi‑Wi telemetry, correlated centrally, becomes inputs to the Fi‑Wi forwarding plane. There is a path to sensing built into future radio-head platforms.

Fi-Wi architecture in four parts: one building-wide concentrator holding the global scheduler, L4S queue management, MAC/PHY state and x86 compute; a fiber plant carrying the PCIe-over-fiber fronthaul; 8 to 96 fiber-attached 802.11 radio heads, several per room, with the concentrator choosing which head transmits, and when; and abundant inexpensive radio sensors that listen passively and carry radiotap telemetry over a Wi-Fi control path through the radio heads to the concentrator, and on to cloud post-analysis. — Swipe the diagram sideways to see all of it. Scheduling and control run centrally. Each cell carries several radio heads, and the concentrator selects which head transmits, and when. The Sonde sensors attach to the radio heads over a Wi-Fi control path, carrying telemetry back in as scheduler input.

What Fi-Wi takes on

The contended wireless segment of the access path. The operator owns the customer experience, and Fi-Wi extends that ownership through the air interface: the last segment to come under a central schedule.

Why now: fiber is the durable plant, and it is cheapest installed soonest.

Fiber install costs are driven by labor rates, and labor rates rise. The same build costs less today than it will later, and it serves for decades either way.

It is also the most durable indoor plant. The same fiber carries Ethernet, DWDM or PCIe, so it is not tied to an application the way a copper category is. Cat5 becomes Cat6, then Cat7, then Cat8, each one a rip-and-replace; fiber installed once carries whatever comes next.

There is a second clock. 6 GHz low power indoor mode trades range for density, often requiring more radios for contiguous indoor coverage. As radio density rises, coordination becomes increasingly important. It lands first in multi-dwelling buildings, student housing, hotels and other dense indoor environments, and it does so on unlicensed spectrum, without paying billions in spectrum auctions.

Measure it first

Umber is a measure-it-first company, founded by the developer and maintainer of iperf 2. The tools that characterise the problem come before the build. They are how an operator sees what the wireless segment is actually doing, and how the result gets checked afterwards.

iperf 2, with an Android client The industry-standard network performance tool, created and maintained by Umber’s founder. The Android client adds L4S testing at the endpoint.
Sonde Captures what the MAC/PHY layer is doing at the points where signals land and from where they originate, simultaneously across the deployment.
UAX-8 developer kit The 8-radio developer platform for Fi-Wi’s C-RAN-style centralized MAC scheduling architecture. Configure and order it in the store, which needs an account.

Read the work

Fi-Wi Forwarding Plane v2 The technical paper, and ground truth for the architecture.
IETF: Scheduling of a Contended Fi-Wi Network The problem statement and the direction proposed for it, as put to the IETF.
A Forwarding Plane for In-Building Wireless The IETF 127 hackathon plan.
Physical AI Why causal observability is the prerequisite for learning, and what the scheduler actually does.

Schedule a demo

See a concentrator scheduling live traffic across radio heads, with Sonde telemetry running alongside it. Write to sales@umbernetworks.com and say what you would like to see.

Investing

Umber is raising on a SAFE. The investment case, the milestone plan and the financials sit behind an account, and investors get their own view of them. Write to info@umbernetworks.com and we will set one up.

Umber stock is eligible for qualified small business stock treatment. Shares issued when a SAFE converts begin their holding period at conversion, and holding them long enough can exclude federal capital gains at exit. Confirm the specifics with your own tax advisor.

Sign in for the full library

Engineering, advisory, customer and investor material sits behind an account, and signing in takes you straight to your own view of it. Account holders can also configure and order UAX‑8 systems and Sonde probes in the store. Accounts are provisioned individually. Write to info@umbernetworks.com and say which material you need.