Wi-Fi chugs toward 1 gig

HP launches dual-radio APs with 900Mbps aggregate connect rates

HP has proclaimed itself to be the first enterprise-grade WLAN vendor to ship dual-radio, Wi-Fi-Certified 802.11n wireless access points with a total signaling rate of 900Mbps.

The two radios in each of the company's new E-MSM460 and E-MSM466 APs both operate in the 5GHz band, explains Roger Sands, HP director of mobility. The APs support three spatial streams and list for about $1,000 in the U.S. Another member of the family, the E-MSM430, supports two spatial streams and costs about $700.

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Sands adds that the high-data-rate APs can be fueled by 802.3af Power over Ethernet (PoE) switches' maximum 15.4-watt power budget without having to turn off any features.

Opportunities for higher 802.11n speeds lie in the 5GHz band, largely owing to a technology called channel bonding, which is impractical in the 2.4GHz band. Channel bonding merges two 20MHz channels into one 40MHz channel to widen the communications path. Similar efforts to further widen the path and achieve full 1Gbps Wi-Fi connect rates are afoot in two IEEE working groups, 802.11ac and 802.11ad.

HP has added support for three spatial streams in its APs, where most enterprise-class products have been supporting two.

In the MIMO world of 802.11n, you see data sheet descriptions of APs like 2x2, 2x3 and 3x3 MIMO. "N x n" refers to the number of transmitting radio/antenna pairs and the number of receiving radio/antenna pairs in an 802.11n device. A 2x3 MIMO product, for example, has two transmitting radios and antennas and three receiving radios and antennas.

The greater the numbers of radios/antennas at each end the more spatial streams you can have and -- in theory -- the greater your throughput should be.

The maximum number of diverse data streams is limited to the lowest number of transmitting and receiving radios and antennas. For example, a 2x2 MIMO AP could send a maximum of two streams. Similarly, the max a 2x3 MIMO AP could send is also two. Opinions on the impact of the third antenna on the receiving side in a two-spatial-stream system differ. Some say that the third antenna just adds cost to the system. Others contend that it contributes to performance improvement because it gives you better diversity and, thus, signal gain.

That's an argument for another day. Now, we just need some client devices to support the three-spatial-stream configuration so that end users can optimize the benefit of HP's performance improvement. Atheros, on whose chipsets HP's (and many other vendors') Wi-Fi gear is based, first introduced samples of its 3x3 MIMO technology last June. So we're likely to see client devices to soon follow.

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