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Ten things to consider before buying an 802.11n wireless device

17 января 2007
If you've spent any time in your local tech shop, you are sure to have seen a rash of Pre-N and Draft-N wireless products. Before you get caught up in a rush of new product frenzy and hand over your money, take a few minutes and look at exactly what you are buying.
  • MIMO. One of the big advantages of 802.11n is MIMO, which is short for Multiple Input / Multiple Output. MIMO breaks the data transmission down to multiple parts that are sent separately to the client, where they are reassembled. One of the requirements for this is multiple antennas to send and receive the data.

    This system has the advantage of extending the range of wireless, along with increasing the capacity that can be carried by the signal. MIMO is implemented in almost all Draft N and Pre N specs. The use of MIMO in these devices has, for the most part, greatly extended the range of these devices. Unfortunately, there are still debates ongoing about the finalisation of MIMO itself, as the 802.11n spec is not ratified yet.
  • Standard not fully ratified. IEEE has not fully ratified the standards for 802.11n. This means that the technical details of 802.11n have not been decided upon. The original draft for 802.11n was voted on earlier this year and soundly rejected, receiving only 46 percent of the needed 75 percent of votes to be accepted. Draft 2.0 of the spec is scheduled be debated and approved in March of 2007. Items adhering to this spec can be labelled as Phase 1 Draft N. These items will be compatible with each other (unlike many current pre-n and draft n components). The final ratified standard will probably be ratified in early 2008. Of course, if no Draft 2.0 can be agreed upon in March 2007, this will push the schedule for all of this back.
  • Equipment cannot guarantee N compatibility. As the final spec of 802.11n is not fully ratified, it is impossible to guarantee that any equipment sold as Pre-N or Draft-N will be compatible with the final spec. Many manufacturers are banking on the assumption that compatibility can be achieved by firmware updates to their equipment.

    Currently the only vendor offering a full replacement warranty should their equipment not be compatible with the final spec is Asus.
  • Huge speed increases over 802.11g. The final 802.11n will undoubtedly boast a great speed increase over 802.11g. This boost will almost assuredly make wireless faster than 100MB Ethernet. Currently most Pre-N and Draft-N equipment is already showing great speed increases. The speed at which they operate, however, varies based on manufacturer and equipment. The advertised speeds vary from 100MB to 200MB.
  • Backward-compatibility with previous wireless standards. While IEEE has announced that any final spec for 802.11n will include backward compatibility for 802.11b and 802.11g, this specification is not finalised. With this being the case, there can be no guarantee of backward-compatibility for current Pre-N and Draft-N gear.

    While most of the products currently on the market offer backward-compatibility, how they implement it varies from vendor to vendor. As a result, there can be (and have been reported) many instances where gear labelled backward-compatible has not been fully backwardly compatible with equipment from other vendors.
  • Draft-N and Pre-N gear may not be compatible with Draft-N and Pre-N gear from other vendors. Currently in the Draft 1.0 of the 802.11n spec, there is nothing to guarantee compatibility among equipment. If you choose to use Pre-N or Draft-N gear you will need to buy all your equipment from a single vendor. While interoperability may be promised, there is no way to guarantee this. The Draft 2.0 spec of 802.11n will include interoperability standards for the release of Phase 1 Draft-N gear.
  • Testing has shown MIMO systems not based on Draft-N standards can be significantly faster than systems based on Draft-N. Real world testing has shown that highest possible speeds using MIMO can be achieved by not sticking to the Draft-N specifications. This means that if you are truly searching for the fastest possible wireless connection, do not force your search to just N class products; include products that use MIMO.
  • Draft-N gear is driven by marketing. It has been several years since any new development was made in consumer grade Wi-Fi. This has led to a certain degree of stagnation within the market.

    The advent of Pre-N gear has given companies something to latch on to in an attempt to offer their customers something new. While there are undoubtedly benefits (in speed and range) to using this new gear, you are putting yourself in line for potential problems. Weigh your needs before jumping on the bandwagon of a "not ready for prime-time" technology.
  • Potential to interfere with existing Wi-Fi. One of the issues with MIMO is that it uses a wide spectrum (40MHz) to send its data. Currently only three (1, 6, and 11) of the available channels in the current 2.4 GHz band are considered to be non-overlapping at this spectrum. However, under a powerful signal they can overlap.

    This means that if you have multiple wireless networks running, your Pre-N gear will need to be on one of these three channels, possibly necessitating a change in your current wireless networks. Also, you will want to plan for the overlap if possible, by moving your current networks to channels not sequential to 1, 6, and 11.
  • Issues with media-streaming devices. One issue that has been reported with Draft-N and Pre-N gear is that it appears it have some issues with various media-streaming devices. This is an extremely perplexing issue, as one of the goals of 802.11n was the ability to stream high-definition media wirelessly. Whether this is due to issues in the Draft 1.0 specs, or if it's an issue with the current generation of media-streaming devices remains to be seen, but at the moment a wired connection remains your best bet for streaming.

    Joshua Hoskins, Tech Republic


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