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10/17/2007Better Client Devices Improve Citywide Wi-Fi User Experience
I have already discussed here how metropolitan Wi-Fi infrastructure products are pushing 802.11 technology and FCC regulations to their limits to provide coverage over the largest possible area. But it's the Wi-Fi client that is the weak link in the chain in terms of radio reception on a metro Wi-Fi network. Using a better client device may be the simplest way to improve the user experience on these networks. For our Wireless Broadband Review, Novarum has tested many different Wi-Fi clients with today's metro Wi-Fi networks. Our standard client is an 802.11g client built into a Dell notebook. This is a fairly typical enterprise-class Wi-Fi adapter with 30 mW output power and an integrated antenna with a few dB of gain. We also test with a high-power client which has 10 times the power of the standard client — 300 mW with 5-dB gain antennas. The high-power client is similar to what you might find in a police car running public-safety applications on a metro Wi-Fi network. It also has similar RF capabilities to the metro Wi-Fi home gateways (such as PepLink) that are recommended by EarthLink, MetroFi, Kite Networks and other ISPs for their residential broadband subscribers. Power Rules It is not too surprising that the high-power adapter gets better results in our testing. On average, the high-power client showed 38% better service availability than the standard client. Networks that had marginal coverage with the standard client delivered excellent coverage with the high-power client. There was a noticeable difference on every network tested. Performance was better with high-power clients, too. The high-power client gets 36% higher throughput than the standard client on average. What does this all mean? Pay close attention to your client type when using a metro Wi-Fi network. When doing acceptance testing on a network, it doesn’t make sense to validate an open public-access network with a 300 mW adapter. The high-power client will give an overly optimistic impression of a network that must support all types of clients. Similarly, if you are certifying a network for public safety, it should be tested with a matching high-power client device rather than a low-power client. When planning a network, be clear on the types of applications and clients that the network must support. A public-access network that supports any Wi-Fi client may need twice as many access points as a network that is used exclusively for public safety with high-power client devices. One downside of the high-power approach is interference. Today, metro Wi-Fi networks and indoor enterprise and home networks are relatively isolated and don’t interfere with one another. By the time the high-power Wi-Fi signal from the outdoor metro Wi-Fi network infrastructure penetrates exterior walls, it is usually lower power than any indoor Wi-Fi access points. If high-power residential gateways for metro Wi-Fi become very popular, however, interference will increase as we bring the high-power devices indoors, closer to other Wi-Fi networks.
Surprising Upside We have been testing draft 802.11n products with metro Wi-Fi networks, and the results are stunning. The draft 11n client we use is a consumer-level USB adapter that is not optimized for metro Wi-Fi in any way. It has 20% better service availability and 26% higher throughput than the standard client. This is surprising because the new technology in the 11n standard was not predicted to have this much improvement when operating outdoors. And this improvement comes with no increase in power over the standard 802.11g client! The infrastructure is still based on 802.11g technology, so we are operating in a mixed mode — only the client side has the new 802.11n technology. What will happen when the infrastructure is upgraded to 802.11n technology? High-power Wi-Fi clents and new 802.11n clients are positive news for cities and service providers. Notebook PCs and handhelds will quickly transition to 802.11n. As more and more customers use 802.11n clients to access existing metro Wi-Fi networks, their perception of the networks will be much better. We usually think of 802.11n as a huge speed increase. In this scenario, it is not a speed increase, but rather better and more robust coverage that is the key benefit. In our most recent Novarum rankings, enhanced Wi-Fi clients (either 802.11n or high power) took eight of the top 10 spots. Clients matter.
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