To better understand the politics of 802.11n, it is necessary to first provide some perspective on how the industry got to this point.
The first wireless network standards were approved in late 1999 by the IEEE as part of the 802.11b effort. Those standards featured two major technologies to distribute packets over the radio spectrum using spread spectrum methods that are still in use by most wireless networks.
Shortly after, the 802.11a standard was ratified, which used orthogonal frequency division multiplexing (OFDM) methods to enable higher data rates. Instead of using the same 2.4 GHz frequency band as existing 802.11b products, however, the 802.11a standard operates at in the 5 GHz frequency range. This allows wireless designers to take advantage of a greater number of non-overlapping channels for transmitting data.
With the benefit of hindsight, we can see now that 802.11b's popularity created a powerful legacy ecosystem and established the need for backward compatibility as new wireless protocols emerge.
Lesson 1: Support legacy 802.11b.
The WLAN industry has since learned the importance of supporting legacy 802.11b devices. While it seemed like a good idea at the time to establish a new and potentially higher-performing frequency band at 5 GHz, this incompatibility was ultimately a disadvantage for these products.
While both 802.11a and 802.11b were important efforts, neither could handle the demands of multimedia applications, such as streaming audio and video. Therefore, another effort began to extend these protocols to support higher throughput and lower latencies. That effort turned into the 802.11g standard that was ratified in 2003, which applied the frequency division techniques of 802.11a but used the original 802.11b radio frequencies (see Table 1 below).
Despite lackluster adoption, 802.11a product lines weren't developed for naught. Working on 802.11a taught engineers how to build radios that operate on different frequency bands.
Many multi-frequency products now combine a/b or a/g radios together, and support clients that operate on either frequency. 802.11n products will have multiple-frequency support built-in, so clients can transmit and receive on both the 5 and 2 GHz spectrums simultaneously, boosting bandwidth and throughput and taking advantage of the larger number of channels and more efficient radio transmissions at the higher frequency range.
Lesson 2: Channels matter.
The number of separate transmission channels in the 802.11b/g frequency range is effectively three: channels 1, 6, and 11 are the only ones that don't overlap with the others.
In radio-rich environments, such as a major downtown urban core, there will be plenty of interference from neighboring wireless networks. To help improve throughput, the 802.11n task group is not only using the 5 GHz spectrum to increase the number of channels, but is also considering doubling the size of the channel itself. Thanks to improvements in channel utilization, most 802.11n products are expected to deliver 100-300 Mbps data rates.
With 802.11a and 802.11b, it took several years between the standard ratification and products appearing on retail shelves. The 802.11g effort was the first time that products were introduced in advance of a final standard.
The success of that strategy has influenced how companies have come to market with the 802.11n chipsets in the past year, and one of the reasons there are so many "draft-n" products sold by the major manufacturers.
By developing products in tandem with the evolving specification, many vendors hope to shrink time-to-market for 802.11n products to less than a year. This brings up the next lesson:
Lesson 3: IEEE and Wi-Fi Alliance need to work in parallel.
In the past, engineers in the IEEE working groups developed a draft standard. Once that was finalized, engineers in the Wi-Fi Alliance would start putting together a test and certification plan to ensure interoperability between various implementations of the standard. But as vendors move more quickly and the market becomes more complex, these two groups need to work in parallel.
That is now happening with the 802.11n standards process. The Wi-Fi Alliance agreed last November to start developing 802.11n certification processes in parallel with the IEEE 802.11n working group.
This also helps because the Alliance needs more time to test the implementations submitted from each vendor due to the complexity of the 802.11n standard. Greater inter-organization collaboration may remove issues and differences, such as those that arose with 802.11g: the IEEE made anything over 24 Mbps optional, but Wi-Fi certification required products to support 54 Mbps rates. Speaking of these higher rates, this brings us to the next lesson learned.
