Q: Is 802.11a the Betamax vs. VHS of wireless networking? Betamax was technically better. Why haven't companies adopted 802.11a?
- Chris, Chicago.
The Wizards (wireless industry experts) respond:
Dan Simone, Trapeze Networks
We don’t believe that 802.11a will prove analogous to Betamax. The 802.11a radio spec provides a number of advantages over 802.11b for businesses, which more time and usage will make obvious.
At first glance, 802.11g seems to provide a similar performance improvement to 802.11a, with 54 Mbit/s as the often-quoted maximum data rate, and the added benefit of backward compatibility with 802.11b. In reality, this backward compatibility hobbles 802.11g’s performance. The minute ANY 802.11b device appears in the neighborhood, the protection modes for 802.11g/802.11b co-existence kick in and significantly reduce the cell’s potential throughput. In addition, 802.11g is susceptible to the same interference sources in the 2.4 GHz band that impact 802.11b, with microwaves and cordless phones being the prominent culprits.
So what are 802.11a’s advantages? First, it runs in the 5.0 GHz band, which is less crowded than the 2.4 GHz band and therefore is less susceptible to interference. Second, 802.11a provides for a maximum throughput of 54 Mbit/s, much faster than 802.11b’s 11M bit/sec. But 802.11a’s greatest advantage is its channel diversity. In the US, the FCC recently allocated additional spectrum in the 5.0 GHz band, so 802.11a will soon offer as many as 24 non-overlapping channels. This feature lets businesses deploy more radios more closely together, with no performance-degrading interference. Each radio therefore supports fewer users, improving the shared medium’s performance for those users.
The main reason for the slow uptake is the lack of built-in support for 802.11a in client devices, such as laptops. As multi-band 802.11a/b/g clients begin to dominate the market, and more users are on the WLAN, businesses will want to migrate to the higher-performing 802.11a frequency. To prepare for that evolution, businesses should ensure that the single-radio access points they buy today are software-configurable for 802.11b/g or 802.11a, so they can migrate painlessly to 802.11a in the future. They’ll still want to keep some 802.11b in the network to support older clients, but the majority of the deployment will move to 802.11a (read how one user, Inmarsat, used 802.11a to make an upgrade to its WLAN)
Albert Lew, Legra Systems
No. Unlike Betamax, which did not spawn a cottage industry of dual technology VCRs, there are such devices in the wireless world. They are known as dual mode (for 802.11a/b) or trimode (for 802.11a/b/g) NIC cards and access points. These wireless devices support all flavors of 802.11. It is a fallacy that companies have not adopted 802.11a. We are seeing that the majority of enterprise deployments we are involved with are using 802.11a. For the price of a call to the help desk complaining about the speed of the wireless network, a wireless user can be equipped with an enterprise-class, WPA certified trimode NIC card. Also, unlike Betamax versus VHS, all the technology that works for 802.11b/g, such as WPA, also works with 802.11a. This is because 802.11a and 802.11b/g only differ at the physical layer (layer 1 in the OSI model). Both 802.11a and 802.11b/g are the same at the MAC layer (Layer 2 in the OSI model).
Marcel Wiget, Chantry Networks
802.11a does indeed offer more non-overlapping channels and isn¹t sharing a frequency spectrum with video surveillance and cordless phones. However, the vast majority of notebooks and handhelds do have 11b/g built-in, and only the more high-end/business-oriented devices offer 802.11a today. This will change over time. More chip manufacturers are offering integrated dual-band solutions. Enterprise-class wireless vendors already offer dual-radio access points that support 802.11b/g and 802.11a simultaneously, and more wireless client devices will also offer dual radios. The more wireless users within a company, the more likely they will take advantage of the 802.11a radio for the additional bandwidth and to avoid congestion. In the end it is tough to say whether 802.11a is like the Betamax of the past. However, we can be certain that both 802.11a and 802.11b/g will co-exist for a long period of time.
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