Portland-based Stephouse Networks, a wireless ISP that frequently provides broadband connectivity to businesses around Portland, recently setup an 8 mile Point-To-Point link using Ubiquiti SR71-15 cards (5ghz 2×2 MIMO 802.11n) to replace a bundle of 6 T1 lines they had feeding one of their wireless deployments in north Portland (St. Johns).
In testing Stephouse CEO Tyler Booth says they were able to push it up to 150Mbit in either direction with a 40mhz channel. Because they didn’t need the speed, Stephouse used a 20Mhz channel for better frequency utilization.
The Routerboard works as a switch/router/firewall device or a high performance Access Point (with the optional radio). RouterOS is part of the “secret sauce” to the speed and performance of the link in a noisy urban environment, says Booth.
When it was initially deployed, we where using the standard 802.11 MAC layer which uses CSMA to control when either side is allowed to transmit. As you can imagine in a noisy environment with 30db of receive gain, these radios are seeing an extremely high noise floor which has an adverse effect on the CSMA protocol, which resulted in slow performance and interface errors.
Most polling protocols have the ability to bypass CSMA since every client has a timeslot (this even applies in PTP links). By turning on Mikrotik’s proprietary polling protocol (Nstream) it allows us to essentially ignore the noise around us (this doesn’t eliminate noise, just lessens the effect it has on the link).
Using a 20Mhz channel (on both polarities), we can get association rates up to 130Mbit and real world throughput of just under 100Mbit even at 8 miles which was pretty impressive to me. I’d initially only expected to see about 50Mbit at this distance.
Stephouse uses Proxim equipment to provide the city of Portland with wireless broadband connectivity. Stephouse has deployed a combination of Proxim’s Tsunami MP.11 WiMAX and Proxim’s ORiNOCO AP-4000LR Wi-Fi mesh technology to blanket seven square miles of Portland with wireless broadband coverage.
Utilizing a combination of the Tsunami MP.11 WiMAX for backhaul and Proxim’s ORiNOCO AP-4000LR Wi-Fi access points deployed in mesh mode for connectivity, Stephouse can provide high-performance fixed-line replacement for a fraction of the cost.
Currently, Stephouse has covered five square miles of Portland’s downtown area and two square miles of North Portland’s St. Johns area with both Wi-Fi and WiMAX service.