[1st-mile-nm] 802.11-VHT: Gigabit Wireless Future?

[Steve Ross]

I've been talking to folks about this for months (I 
volunteer to do some of the security-related math). Two points:

1. The sub-6 GHz idea so far would be TERRIFIC for indoor 
wifi, especially in a specific dwelling unit. But over a 
wider area with lots of users, you'd need a lot of radios or 
it falls apart... and it might fall apart anyway (at least 
the clever Motorola plan). Indoors, the planned "802.11a" 
wavelength is more easily blocked than b/g/n, so ganging 
multiple radios at a base station to get a MIMO pattern is a 
key feature, not merely a bandwidth-enhancer.

2. In this spectrum, a lot of companies are likely to have a 
stake, meaning a complex standards-setting scrum. So 2012 is 
optimistic. The entrails I've been reading suggest an n-type 
mashup. Ugh. we'll be lucky to get n by 2010! By 2012, 
802.16-type ideas (WiMAX) and structured wiring may be the 
norm; the chipsets will certainly be cheap thanks to GSM 
pickup. Also, 1 Gbps in the home will probably be 
obsolete/too little bandwidth by 2020.... except maybe in 
places like New Mexico....<g>


Steven S. Ross
Editor-in-Chief
Broadband Properties
steve at broadbandproperties.com
www.bbpmag.com
SKYPE: editorsteve
+1 781-284-8810
+1 646-216-8030 fax
+1 201-456-5933 mobile

Richard Lowenberg wrote:
> Gigabit Wi-Fi Could Follow 802.11n
> 
> http://news.yahoo.com/s/zd/20080902/tc_zd/231522
> 
> Mark Hachman - ExtremeTechTue Sept. 2.
> 
> Although the IEEE 802.11n specification is still a year or more away from
> release, a small group of engineers is already moving ahead to the next
> generation of wireless networking. The goal? Gigabit Wi-Fi, to match the wired
> gigabit Ethernet links of today's PCs.
> 
> A working group is preparing to propose what may eventually be known as IEEE
> 802.11 VHT (Very High Throughput), in what some call the successor to 802.11n.
> Two working groups each are suggesting proposals to push throughput in excess
> of one gigabit per second, roughly ten times that of the 802.11n specification.
> 
> At this point, the IEEE has yet to formally approve what's known as a PAR, or a
> Project Approval Request, the first step on the road to an IEEE standard.
> However, that approval is expected. The proposed technology has also not yet
> been blessed by the Wi-Fi Alliance, which governs the technology.
> 
> On the other hand, much of the group's work has been in cooperation with the
> Alliance, including plans to use the technology in wireless display
> technologies for HDTV, fast file transfer, and campus deployments, among
> others.
> 
> If approved, the increase in data rates would be dramatic, at least by today's
> standards. The 802.11n standard calls for bandwidth on the order of 600
> Mbits/s; today, so-called "pre-n" devices offer roughly 300 Mbits/s. But actual
> throughput can be much less, or only about 100 Mbits/s, after overhead and other
> traffic. The 802.11 VHT proposals call for throughput of at least a gigabit per
> second, which could place actual data rates many times higher. Interestingly,
> none of the PAR documents mention the estimated range for the wireless link.
> 
> When could such a standard be ratified, and IEEE 802.11 VHT products hit the
> market? Possibly around 2011 or 2012, according to James Gilb, the technical
> editor for the WirelessHD consortium and the maintainer of the 802.11 VHT PAR
> page.
> 
> IEEE specifications typically take about four to five years from proposal to
> product; the confusion surrounding the 802.11n standard will probably push
> formal 802.11n products out until 2010, Gilb said. In July, the IEEE P802.11n
> task group pushed the timeline for the official publication of 802.11n out by
> six months, to November 2009.
> 
> Gigabit Wi-Fi has been proposed before, although not in specification form. In
> 2007, a research group from the Georgia Electronic Design Center (GEDC) at
> Georgia Tech developed a 15-Gbit link at 1 meter.
> 
> The details
> 
> Two IEEE 802.11 VHT PARs have been submitted, according to documents the group
> has posted: one dealing with sub- 6 GHz communications, and one using
> frequencies of 60 GHz and above. While a few key details have been released,
> more updates are expected in the second quarter of 2009, Bruce Kraemer, the
> chairman of the IEEE Working Group and a senior manager of strategic marketing
> for Marvell Semiconductor, said in an email.
> 
> The author of both the sub-6-GHz and 60-GHz PAR is Eldad Perahia, a senior
> wireless systems engineer at Intel, who did not reply to requests for comment.
> 
> The 802.11 VHT sub-6-GHz spec has two overarching goals. "It would be fair to
> say a goal is to find ways to either serve more users per unit area or to
> increase the bits/second delivered to users in a given area and backward
> compatibility is the norm," Kraemer said in an email, when asked about the goal
> behind 802.11 VHT.
> 
> "There are no technical agreements on the project plan since it has been
> concentrating on a basic objective statement for the PAR," Kraemer added.
> 
> At this point, it's difficult to say which of the two PARs might have more of an
> effect on PC users and consumer-electronics aficionados. According to Gilb, the
> sub-6-GHz PAR looks more likely to replace traditional Wi-Fi, if only because
> the proposal looks more like a traditional wireless network. The goal is for
> the sub-6-GHz spec to be backwards-compatible with traditional Wi-Fi, but to
> avoid using and interfering with the 2.4-GHz frequency band used by today's
> 802.11b and 802.11g.
> 
> The sub-6-GHz PAR proposes a single-link throughput of only 500 Mbits/s, but
> contains an interesting provision: "a maximum multi-STA throughput (measured at
> the MAC data service access point), of at least 1 Gbps". Put simply, it means
> that the proposal suggests that bandwidth be aggregated among STAs (stations),
> which include the Wi-Fi client cards and chips found within PCs.
> 
> How? A July 2007 proposal by Motorola may have the answer. It suggested using
> Orthogonal Frequency-Division Multiple Access (OFDMA) bandwidth allocation,
> which would assign a user "chunks" of bandwidth measured in time and frequency.
> OFDMA is an advanced form of CDMA, a channel access method employed by
> CDMA-based cellular phones, among other devices.
> 
> According to the document, 100 MHz of bandwidth would represent 320 subcarriers,
> with 8 adjacent subcarriers grouped into one chunk. The forty chunks would then
> be divided by the number of users. Using a technique called optimized chunk
> allocation, throughput increased as the number of users also increased,
> Motorola found: 33 percent for two users, and 66 percent for six users. The
> performance gains trailed off sharply after that.
> 
> The authors of the Motorola report suggested that the 802.11 VHT PAR "adopt a
> requirement on the aggregated throughput and not the peak throughput to
> introduce multi-user component into the standard" ? which, apparently, the
> sub-6-GHz PAR has done: "The project may include the capability to handle
> multiple simultaneous communications," according to the PAR. "The 1Gbps maximum
> multi-STA [client] throughput may be achieved when considering multiple
> simultaneously actively-communicating STAs, e.g., a BSS [base station] with 1
> AP [access point] and at least 3 STAs."
> 
> Modifications to both the physical access layer (PHY) and media access control
> (MAC) would be required, the PAR says. However, the working group also hopes to
> design in power-saving technologies above and beyond what is offered in Wi-Fi.
> 
> The 60-GHz PAR
> 
> The 60-GHz proposal, however, aims for pure, blazing speed. Like the sub-6-GHz
> PAR, the 60-GHz flavor of 802.11 VHT also proposes altering the MAC and PHY. In
> this case, however, each single link would be capable of a gigabit per second
> throughput, primarily through the use of a wider swath of spectrum, or 57 to 66
> GHz.
> 
> If the sub-6-GHz proposal seeks to avoid interference with traditional Wi-Fi,
> the 60-GHz version is hoping to design around the wireless multimedia
> specifications that operate in the 60 GHz range. The problem here is twofold:
> first, there is an existing specification that offers similar capabilities:
> IEEE 802.15.3, designed for "personal area networks" running at speeds up to 55
> Mbits/s or so. Second, specifications like the WirelessHD group also operate in
> the 60-GHz band.
> 
> According to the 60-GHz working group, the proposal will maintain the "802.11
> user experience" ? basically, a familiar universe of base stations, access
> points, and clients, together with the underlying infrastructure. The group
> anticipates that future Wi-Fi radio will access the familiar 2.4-GHz/5-GHz
> Wi-Fi networks, but also 60-GHz networks as well. And if a 60-GHz network isn't
> available, the radio would search out a lower-bandwidth Wi-Fi connection.
> 
> Co-existence with other 60-GHz systems is so important that it is specifically
> called out in the PAR as a requirement.
> 
> What appears to be happening, however, is that 802.15.3 and the new 802.11 VHT
> technology "will go out as separate standards, and we'll let the market
> decide," Glib said. While the physical chips are relatively similar, the fact
> that both use the same frequency band means that they'll both share the same
> airwaves. The question will be whether the two standards can truly cooperate,
> or whether manufacturers will have to choose one over the other.
> 
> 
> ---------------------------------
> Richard Lowenberg
> 1st-Mile Institute
> P.O. Box 8001, Santa Fe, NM 87504
> 505-989-9110;   505-603-5200 cell
> rl at 1st-mile.com  www.1st-mile.com
> 
> 
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