IEEE 802.11n is the new international standard for wireless Local Area Networks, incorporating new smart antenna technologies (MIMO – Multiple In and Multiple Out) permitting a 5x performance and 2x coverage improvement for WLANs. While this new technology is becoming the de facto standard in consumer and enterprise networks, it has not yet made an appearance in outdoor, metropolitan scale networks derived from Wi-Fi technology. (Note: Meraki just released today the first 802.11n outdoor mesh product)
Many of these same MIMO techniques are being incorporated in both WiMax and in LTE for cellular networks. Sadly, neither is being produced in much volume and fixed WiMax networks do not incorporate MIMO technology.
There has been much dispute about whether the specifics of 802.11n designed for indoor networks would apply to outdoor networks and bring the economy of scale of 802.11 to outdoor applications. At Novarum, we tested the effects of 802.11n on outdoor performance. We found dramatic improvements in using indoor 802.11n technology outdoors, so much so that 802.11n has become, for us, the recommended baseline for new network deployments.
First, let’s review the key pieces of technology incorporated in 802.11n and how it might affect outdoor performance.
In the course of Novarum’s Wireless Broadband Review in 2007 and 2008, we examined over 25 deployed Wi-Fi networks (including all major vendors), 46 deployed 3G cellular networks and 4 fixed pre-WiMax networks. In the case of Wi-Fi networks, we noted the dramatic effects that client selection had on network performance, coverage, and ultimately, user satisfaction.
We both examined 802.11n clients against the installed multi-vendor base of 802.11g infrastructure and constructed our own testbed from early outdoor 802.11n components to evaluate the effect of 802.11n when deployed in the infrastructure itself.
It is important to recognize that in almost all outdoor Wi-Fi networks, the client access uplink is the weakest link in the communication chain. Legacy 802.11b/g clients experience VERY high packet retry rates of between 100% and 1000%, and there are often deep multi-path fades of between 10-30 dB within a few tens of feet. The Wi-Fi protocol is VERY good at masking these effects – instead they are most commonly seen indirectly – by lower throughput and higher delay variance. These effects are seen even for deployments of very high access node density of 50 nodes per square mile or more.
These deep fades and very high packet retry rates made mobility difficult, dramatically affecting throughput, and causing packet delay variance to be so high as to make streaming media difficult, thereby materially decreasing the overall capacity of these networks.
The improvements that 802.11n provides outdoor networks astonished us – particularly for a technology that has been disparaged as inappropriate for outdoor deployment. Deploying IEEE 802.11n technology has dramatic effects outdoors – both with legacy systems and even more compellingly with green field deployments.
Let’s summarize what we found in Novarum’s experiments:
- 100% throughput improvement of 802.11n Wi-Fi clients with legacy 802.11g outdoor infrastructure;
- 100% throughput improvement of legacy 802.11g Wi-Fi clients with new 802.11n outdoor infrastructure;
- 200% throughput improvement of 802.11n client with 802.11n outdoor infrastructure;
- Similar coverage of 802.11n clients and infrastructure in the 5.4 GHz band as for legacy 802.11g clients and infrastructure in the 2.4 GHz band – making the 5.4 GHz band useful for client access;
- 25% decrease in access latency and a dramatic improvement in latency variance;
- a low power 802.11n client has the same throughput and coverage as a high power 802.11g with 10x the power and antenna; and
- coverage to smartphones at low power and with poor antennas dramatically improves.
These results have a dramatic impact on outdoor wireless networks, bringing the benefits of MIMO technology at consumer price-points.
These are the improvements we expect in outdoor networks that use 802.11n technology:
- 400% to 800% increase in system capacity and throughput;
- 200% to 300% improvement in spectral efficiency through increased link budgets, reduced packet errors, increased modulation rates and improved fading performance;
- effective client access to the 200 MHz of the 5.4 GHz band;
- 802.11n clients dramatically improve legacy 802.11g networks and new 802.11n networks dramatically improve legacy 802.11g clients;
- Streaming media applications will perform as we expect and will be much easier to deploy;
- Better backbone designs by reducing the interference of the backbone mesh through beam-forming antennas rather than omnidirectional broadcast;
- Decreased deployment cost due to decreased node cost, possibly dramatically.
While not optimally designed for outdoors, 802.11n will substantially increase the performance of and customer satisfaction with outdoor wireless networks.
We can expect the first product announcements of outdoor Wi-Fi networks incorporating 802.11n shortly. We also expect all major vendors of outdoor Wi-Fi equipment to ship 802.11n products by the end of 2009.
Novarum recommends that all new outdoor Wi-Fi networks use 802.11n products in their infrastructure and 802.11n clients wherever possible.
About the author
Ken Biba is a co-Founder and Chief Technical Officer of Novarum, an advisory firm specializing in wireless data networks. Ken has over 30 years experience in the network information systems industry combining a background of general management with a strong product and marketing focus in network systems and information security. Ken was an early engineer of the Internet in 1975. He has co-founded and managed four notable networking companies-Sytek, which was focused on cable TV-based local and metropolitan data networks, Agilis which delivered the first wireless handheld computers, Xircom, which pioneered local area networks for mobile computing, and Vivato, which was focused on scaling Wi-Fi infrastructure to cover campuses and metropolitan areas. Ken’s perspective as CEO, board member of public and private companies, and as a technologist brings unique insight to the business, market and technology of bringing useful wireless solutions to users. Ken has a Bachelor of Science in Physics (Magna Cum Laude, Tau Beta Pi) and a Master of Science in Computer Science from Case Western Reserve University. This article is posted on the Novarum blog.
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