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The VHT group has been considering the two frequency bands, for different reasons and possibly for different purposes. The group could even propose developing the standard for both, treating them as complementary, Moorti says.
That makes sense to interested observers like Proxim Wireless. "At this point, we're not sure whether or not the 60 Ghz band will provide enough range to support enterprise WLANs, but it is certainly worth exploring," says Ajit Jha, WLAN Product Manager at Proxim Wireless. "The 6 Ghz band is also worth exploring, since it provides the key benefit of backwards compatibility with existing 802.11 a/b/g/n WLANs."
The 60GHz band has a lot of unused spectrum available, and the VHT advocates like it because it’s well-suited for very high speed, single links. But because of the high frequency, the signal doesn’t penetrate easily through walls and other obstacles, so the applications are likely to span very short distances, such as one or two rooms in a home or office, for example. “This technology is very nascent,” Moorti says.
“It used to require all kinds of exotic silicon, but now you can do this in CMOS,” says Mathias. “But because of the problem of radio propagation, you have to be very directional, and you need sophisticated antenna arrays.”
The under-6GHz band has less available spectrum, so VHT advocates are looking at an array of methods, from advanced digital processing to more mature antenna technology, to dramatically boost throughput beyond 11n, Moorti says. “The under-6GHz band is about multi-user technology to improve overall network performance,” he says.
One technique being considered is parallelizing data transmissions between a VHT access point and its associated clients. Today’s access points share limited throughput and work with associated clients in serial fashion, Moorti says. Without parallel transmissions, even a VHT access point supporting 500Mbps would still be limited by that inherent serial transmission. “[But] if you can parallelize those guys, and send to them at the same time, each user gets the full 500Mbps,” Moorti says. “All the traffic would flow at the full rate.”
The VHT Study Group has already been in talks with the 802.15.3c task group, which focuses on wireless personal-area networks, and is also considering the 60GHz band. Some accounts portray the discussion as a real or at least potential conflict. Moorti sees the discussion as a sensible, early attempt to start resolving potential coexistence issues between the two technologies. “From what I understand, things are progressing,” he says. “I don’t see any problems that would prevent either group from moving forward.”
Read more about wireless & mobile in Network World's Wireless & Mobile section.