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October 2007 | Volume 10 / Number 10
Inside Networking

Inside Networking The Next Generation Wireless LAN and the Unwired Enterprise

Hyperconnectivity is a mega-trend - a phenomenon through which everyone and everything that can benefit from being connected to the network will be connected. The implications of Hyperconnectivity go beyond the challenges of hyperconnected users (being addressed through rich media Unified Communications systems) to an explosion in network-connected devices - for example, in the realms of energy and property management, asset and location tracking, telemetry and enhanced security systems.

Hyperconnectivity, with 10 to 100 times more endpoints, will rely heavily on wireless network access - not the variety typical of today’s 802.11 a/b/g deployments - but true wireless broadband, pervasive, always-on, always-available wireless as provided through 802.11n. 802.11n will enable an impressive variety of mobile and even stationary devices to be economically connected, as the underlying cost per unit of wireless bandwidth continues to drop. In fact Forrester predicts that the emerging IEEE 802.11n standard is likely to drive a 3-5 year, large-scale “forklift” upgrade cycle beginning in 2008.

So what makes IEEE 802.11n so critical to the hyperconnected world? In one word: scalability.

802.11n is in the Air

How scalable is 802.11n?

802.11n represents a significant leap forward for WiFi in terms of capacity, performance, coverage and reliability. Real world data rates well over 100Mbps are possible, over 20 times faster than 802.11b, five times faster than 11a and 11g (the most recent standard ratified in 2003). In addition, the range of these systems will be roughly twice what is possible today at a given rate. Saying this differently, the rate at the edge of a coverage area could be over 10Mbps, compared to 1Mbps for legacy WiFi systems. 802.11n brings a range of technology innovations: most significantly, MIMO, spatial multiplexing and increased channel bandwidth.




MIMO (Multiple Input Multiple Output), also used in WiMAX, utilizes multiple transmit and receive antennas, each with their own radio components to achieve antenna and spatial diversity. The receiver can use from 2 to 4 antennas to coherently resolve information received across multiple paths (e.g. direct line-of-sight signals and those reflected for example, by walls and pillars in the building). Previous WiFi systems employ SISO (Single Input Single Output) technology and saw these multipath signals as interference which had a negative impact on performance.

Spatial multiplexing relies on MIMO and allows each of these discrete signal paths to carry unique packet streams in parallel. The receiver then re-assembles the packets from each path into a single cohesive stream resulting in greater data transfer rates. The greater the number of spatial streams, the greater the potential data rate - 802.11n specifies up to 4 spatial streams which is possible when both the transmitter and receiver support 4-antenna MIMO (referred to as 4x4). Antenna diversity and spatial multiplexing combine together to enable higher effective rates and longer distances, than SISO systems used by today’s WiFi systems.

Increased channel bandwidth of 40 MHz is twice that of today’s 802.11a/b/g. While this doubling of channel bandwidth is optional, the benefits are obvious.

IEEE 802.11n also includes some other technology innovations. Beamforming allows the transmitting station to replicate and phase the delivery of a single stream from each of its multiple antennas, such that the combined signal amplitude is optimized at the receiving station - essentially synthesizing a stronger signal which can then support a higher data rate. Payload aggregation increases efficiency by allowing more data to be handled in a single packet, thereby minimizing overhead and MAC coordination cycles.

Existing standards such as 802.11i for security and 802.11e for multimedia traffic management apply equally to 802.11n systems. Backward compatibility with existing IEEE802.11a/b/g is supported, although careful spectrum planning is highly recommended to avoid a significant performance penalty.

What’s happening on the standards front? Draft 2.0 was released in March 2007 along with over 3,000 comments, which will need to be handled in the next revision. The general consensus is that the Draft 3 spec will be completed in the first half of 2008 on a path to formal standardization in 2009. IEEE 802.11n is at least a year away from true interoperable solutions.

The Unwired Enterprise

In many ways, 802.11n will be the first enterprise wireless standard, which truly lives up to its billing as a ‘local area network’ technology, with LAN-like performance. 802.11n can meet the connectivity needs of the hyperconnected enterprise, with mobile user access to rich media applications, and at the same time handling an explosion of connected devices. With 802.11n, many enterprises building out new facilities will choose this wireless technology as an alternative to wired desktops and deploy all-wireless office environments. Consider that some customers have gone all wireless even with today’s 802.11a/b/g technology. Consider that Nortel recently announced a WiFi desktop video phone. With next-generation 802.11n wireless, the network architecture will evolve to be a truly integrated network in which the wireless functions are an organic extension of the LAN infrastructure - leveraging business optimized intelligence and common network and security management to deliver a simplified network and lower TCO.

So by all means continue to deploy traditional WiFi where it makes sense, but factor the plan to forklift to IEEE802.11n when the business need arises. IT

Tony Rybczynski is Director of Strategic Enterprise Technologies in Nortel, and has over 35 years experience in the application of packet network technology. He writes a quarterly ‘Inside Networking’ column in Internet Telephony magazine. Kyle Klassen is Director of Enterprise Wireless Solutions in Nortel, and has over 12 years experience in the design and commercial introduction of emerging technologies.

» Internet Telephony Magazine Table of Contents



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