Wireless in the real world
This article was published in PC Pro magazine in July 2015 (issue 249, page 114) and features comments from Alan Ingram (Technical Director).
Around a year ago, PC Pro received an email from reader Alan Ingram with a plea for help. He wrote:
One aspect of Wi-Fi technology that seems to have been forgotten about is point-to-point connections. I’m responsible for two sites that employ point-to-point Wi-Fi to link buildings. Both have challenges of distance, line-of-sight and so on. But after a lot of messing around, the best solution I came up with has been a pair of Buffalo WHR-HP-G54 running DD-WRT connected up to D-Link ANT24-210021dBi directional 11g grid antennas. This gave me a reasonably quick connection (a little of 20Mbits/sec) over a few hundred metres, even when line-of-sight was iffy at best.
However, this kit is now seven years old. With VDSL I could theoretically achieve similar speeds by routing the data halfway around the country via a consumer-level broadband connection to each building; there must be a better solution now?
The problem seems to be that most of the advances in Wi-Fi are around MIMO, which require a router looking like a Christmas tree, with more and more antennas. This doesn’t lend itself well to directional antennas from what I can gather. Has there been a wireless standard or router since 802.11g that’s designed for single antennas, that allows for better stability and throughput than 802.11G?
Alan is Founder and Technical Director at ePartner Consulting Ltd in Lightwater, Surrey, a company that’s heavily into areas such as business process management, workflow automation and data capture. The company uses its site-to-site wireless link mainly for things such as VM replication, where Alan reports that the initial copying can take days.
I don’t normally get involved with reader queries this specific, but this particular case piqued my interest.
Alan mentioned that Wi-Fi bridges don’t use MIMO technology, and many believe this, but it’s not true. It may look as though a point-to-point link contains only a single antenna, but often they’ll contain several, albeit much closer together than with a typical domestic or SME-focussed wireless access point (AP). I pointed Alan at the kit available from Ubiquiti Networks, and in particular its NanoBeam outdoor APs.
I’ve found these to be very useful for point-to-point wireless links, as well as being relatively inexpensive. The NanoBeams are an update of Ubiquiti’s earlier NanoBridge/NanoStation units, which I’m sure some of you will be familiar with. To give you an idea of the price, the NanoBeam NBE-5AC-19 (which, if we decode the model number, is a 19dBi antenna with 5GHz 802.11ac wireless) retails for around £60 exc VAT per end.
Alan told me he wasn’t particularly impressed with Ubiquiti’s support and advice; the manufacturer had just passed him off to resellers that either didn’t have the details he needed, or didn’t care. I guess that’s one of the pitfalls when buying kit this cheap – there’s no margin to pay for a decent pre-sales function. However, there’s an excellent community forum at http://community.ubnt.com. Alan found several people there who were able to guide him in the right direction. He reports that:
The results were good. I’ve gone from Windows file transfers of about 2MB/sec with the old D-Link kit to pushing 50MB/sec. I suspect with a bit of fiddling I may be able to achieve slightly better, but I’m happy for now.