A is a period of time that is inserted between data transmissions to prevent overlap between the transmissions. Though necessary, a guard interval is essentially wasted time, which means wasted bandwidth. 802.11n introduces efficiencies, which allow for the reduction of the guard interval, cutting the time in half, hence a "short" guard interval.

This efficiency can lead to up to an 11% improvement in overall performance, but keep in mind that the short guard interval can only be used when a 11n AP is communicating with a 11n client. If the wireless network includes a mix of 11n and non-11n wireless clients, the performance improvements of the short guard interval are reduced since the "long" guard interval will be used with all non-11n clients. Support for this capability is growing rapidly in commercially available hardware.

is arguably the most complex new technology introduced with 802.11n. In its simplest form, beam forming allows the transmitting device, whether AP or wireless client, to alter the transmission pattern from its antennas to "direct" the data towards the receiving party. It requires the AP and clients "learn" where each other are before employing any beam forming, and if clients are actively moving about (after all, isn't mobility one of the hallmarks of 802.11?) then beam forming becomes more or less useless.

Given its complexity, it's safe to assume that most 802.11n hardware has yet to take advantage of this part of the 802.11n specification. This is changing, however, and some enterprise-grade systems are beginning to include beam forming as part of the feature set. However, the jury is still out as to how effective, and how widely supported, beam forming will become.