WIRELESS LOCAL AREA NETWORKS, OR WLANs, have been around for more than 15 years, but early products were extremely slow and lacked security. Marketplace acceptance of WLANs really began with the debut of 802.11b-based products, which boosted the nominal data rate to 11Mbps. Later, the 802.11g standard raised the data transfer rate to a respectable 54Mbps (though this is the 'nominal,' over-the-air rate; with wireless LANs, actual data transfer rates as experienced by users are typically half the nominal rate).
The emerging IEEE 802.11n standard promises to give WLANs another speed boost'four to five times 802.11g, or more. Draft 2.0 of the standard was approved in March, and the Wi-Fi Alliance in late June began interoperability testing for IEEE 802.11n Draft 2.0-compliant products.
Aside from speed increases, there have been important steps forward in security. The first widely used encryption scheme, Wired Equivalent Privacy (WEP), proved to be cryptographically weak and is easily compromised. After much work, a more robust encryption scheme, known as Wi-Fi Protected Access (WPA), was released. WPA, and its latest revision, WPA2, have eliminated WEP vulnerabilities.
WHICH WAY TO GO?
Like any technology, wired and wireless LANs have their strengths and weaknesses. 'In virtually every company, you're going to find needs for both technologies for the foreseeable future,' says Mark Thompson, director of global sales and marketing for HP's ProCurve Networking business unit in Roseville, Calif. Further, Thompson notes, 'It's always going to be the case that performance levels of wired LANs are higher'a little to a lot higher.'
Wired LANs also excel in other areas, such as reliability (not subject to radio frequency interference), low latency (packet delay), and low jitter (packet-topacket variations in arrival times). Aaron Vance, senior analyst at Synergy Research Group, agrees that WLAN speed improvements are chasing wired LANs, which are on a pace that's hard to compete with.
'Gigabit Ethernet to the desktop is a trend [in wired LANs],' he says. 'Wireless doesn't nearly approach those speeds.'
But WLANs don't necessarily need to equal that performance. They just need to be up to the task at hand, while offering the benefits of being wireless: mobility, convenience, and the elimination of cabling costs. Why go wireless?
'It could be the comfort and ease of being able to put a notebook PC on your lap and not having a cord hanging off of it, all the way to the challenges of having connectivity where it would be almost impossible to pull wires,' says Thompson.
Ryan James, director of enterprise SMB markets in Nortel's Toronto office, ticks off what his firm sees as three indicators that a company is primed for adding WLAN. One is 'congestion' in the wiring closet, due, for example, to running out of ports on an existing router or switch. Instead of trading the router/switch for a bigger one, you could install a wireless access point. A second scenario is so-called 'Cat-5 exhaustion,' or running out of wiring to user locations.
Finally, SMBs have the same mobility needs as do larger organizations. 'People need to be able to move from one spot in the building to another, and not have to worry about what's going to happen when they move,' says James.
THE CUSTOMER IS KING
The answer depends on customer perspective, says Ken Dulaney, vice president and distinguished analyst for research firm Gartner Inc. 'If you're into taking risks, want the latest and greatest, and understand that there are potential incompatibilities that may occur, then go with [draft 11n products],' he says.
Large organizations typically have some installed base of 802.11a/b/g equipment, and Gartner has been advising its clients to stick with their existing WLAN infrastructure until the standard is finalized. As Dulaney notes, the existing WLAN equipment is readily able to handle current throughput requirements.
Some computers, principally laptops, are now beginning to ship with draft 11n-compliant WLAN adapters, however, and Dulaney says that Gartner is aware that companies purchasing new computers are faced with the decision of whether to purchase computers with those adapters, or with legacy 802.11g adapters. Dulaney notes that the 802.11n client adapters, because of MIMO technology, can coax slightly better performance out of 802.11a/b/g infrastructure.
On that basis, if customers are buying a laptop today and can get it with a Wi-Ficertified, Draft 2.0-compliant network adapter, 'it's probably worth putting it in your laptop,' he says. On the infrastructure (access point/wireless router) side, he still recommends waiting for the standard to be finalized.
The draft 11n products now on the market are largely directed at the consumer and, to some extent, the small business market. These groups might be considered more able to tolerate risk, as the prospect of having to replace perhaps one access point and a handful of WLAN clients is not that daunting. By comparison, some larger organizations have an investment in dozens or scores of access points and hundreds or thousands of clients.
Although manufacturers offering draft 11ncompatible products say that these products will be software- or firmware-upgradeable to the finished standard, there are few, if any, written guarantees to that effect. So it's advisable to make clients aware that there's always the possibility that any draft 11n equipment they buy now may have to be replaced. It's clear that the trend is toward WLAN adoption, and that 802.11n is helping to spur the uptake. This wave of adoption is already being felt in the home and small business markets, and will take up to several years longer in the medium and large enterprise markets. But it'll come.
WIRELESS TO THE NTH DEGREE
One of the key speed-boosting ingredients in the developing 802.11n standard is the utilization of multiple input/multiple output (MIMO) technology. MIMO involves the use of multiple receivers, transmitters, and antennae to send two or more independent data streams at the same time, within the same radio channel. The 802.11n standard specifies the use of at least two data streams, up to a total of four. Most of the draft 11n products coming out now employ two or three streams. Eventually, there will be products that support the maximum four streams. The new standard permits operation in either the 2.4GHz frequency band used by 802.11b/g devices (supporting interoperability with those products), or the 5GHz band used by 802.11a devices (permitting interoperability with 11a devices), or both.
Most of the early 802.11n products are expected to operate in the 2.4GHz band, but particularly for products targeted to large enterprises, you can expect dual-band 11n products, which further add to the potential aggregate data rate by using both bands simultaneously.
Another technique for boosting the data rate is to take advantage of the 802.11n standard's support for the use of double-wide 40MHz radio channels, which can theoretically double the data rate that is otherwise obtainable with the 20MHz channel used by legacy WLAN products (802.11a/b/g). In order to interoperate with those legacy devices, it is necessary to use 20MHz channel widths.
There are at least two schools of thought for making a wired-vs.-wireless decision. The first is to take advantage of wired Ethernet's high performance and use it where it makes the most sense'to desks in offices, for example. Wireless is provided where there's a need for mobility' conference rooms, common areas, and so on. The second is to simply go wireless, because WLAN technology has evolved to the point that it's able to handle the requirements. Nortel is one company that's confident wireless can do it all, both in the LAN and in the WAN (wide area network). In July, Nortel announced its 'Unwired Enterprise' initiative, which the company calls its 'vision for the all-wireless office.'
WLAN connectivity would be provided by 802.11n devices, while the wireless WAN connectivity could be courtesy of 3G mobile networks or WiMAX (the wireless metropolitan area network technology codified by IEEE as Standard 802.16, and promoted by the WiMAX Forum). Several points are clear: WLANs have already enjoyed strong adoption in homes and small businesses where there is generally no existing wired infrastructure. Larger organizations have relied mostly on wired Ethernet, deploying WLANs only where there's a clear need for mobility. Much of this reticence for using WLANs has been due to legitimate security concerns, but the new, stronger encryption schemes have now largely removed this crucial roadblock to corporate WLAN adoption. WLANs, while still latency-challenged when compared with wired LANs, are improving in this regard, and developments such as the IEEE 802.11e standard and the Wi-Fi Multimedia specification are helping to improve quality of service.
For those who opt to go wireless, a second question is whether to go with equipment based on the current 802.11g standard; wait for the 802.11n standard to be finished and for equipment based on it to come to market; or consider products currently on the market that comply with the draft of the developing 11n standard.