[LINK] WIFI Developments
stephen at melbpc.org.au
stephen at melbpc.org.au
Wed Dec 5 15:40:12 AEDT 2012
Rolling up developments in Wi-Fi
By Jay Botelho, (Network World) 04 December, 2012
<http://www.arnnet.com.au/article/443707/rolling_up_developments_wi-fi>
Even though users typically only notice the major changes designed to
improve the performance of Wi-Fi, the 802.11 specifications are
constantly under development.
For every "public" change there are five background changes, some of
which are significant.
With more than 20 802.11 specifications already ratified and many more in
development, it makes sense to occasionally "roll up" the changes. Many
of these protocols, after all, can cause functional overlap and need
extra attention to become interoperable.
802.11-2012 incorporates ten recently ratified 802.11 amendments into an
overall 802.11 spec, making it easier for engineers working with 802.11
to find what they need, and it also helps alleviate interoperability
issues between protocols.
IN DEPTH: 11ac will be faster, but how much faster really?
Here are the 10 specs that are part of this roll-up, including the year
they were ratified and a brief description of each:
* 802.11k: Radio Resource Measurement Enhancements (2008). Mainly used by
AP manufacturers, this amendment makes additional radio and network
information available to WLAN devices. This information is used to make
real-time decisions about WLAN management, typically for better load
balancing. [Also see: "Latest 802.11 standards: Too little too late?"]
The specification provides mechanisms for the AP or the central WLAN
controller to offload users to another AP, even if the new AP has weaker
signal strength than the impacted one. This could lead to signal strength
and connectivity issues for WLAN users, so this needs to be considered
when performing WLAN analysis of systems utilizing 802.11k.
WLAN systems designed for stadiums, auditoriums and large lecture halls
will benefit from this specification. Usage in these settings is
typically very dense, requiring careful WLAN bandwidth and user
management, and 11k will provide the necessary data and control for
managed WLAN equipment to handle these sporadically dense environments.
* 802.11n: Higher Throughput Improvements Using MIMO (September 2009).
Just about everyone is familiar with 802.11n. The key technology
introduced in this specific is MIMO (multiple input, multiple output),
which allows for the simultaneous transmission of multiple unique data
streams to significantly increase overall throughput.
802.11n is quickly becoming the de facto standard for commercially
available WLAN equipment. The new technologies it introduced are very
advanced, and it's unlikely that the full potential that 11n offers will
be delivered to the market due to some practical limitations. However,
the lessons learned from these limitations are quickly being addressed
with new 802.11 specifications, most notably 802.11ac.
* 802.11p: WAVE -- Wireless Access for the Vehicular Environment (July
2010). 802.11p deals with data exchange between high-speed vehicles, and
between vehicles and a yet-to-exist roadside WLAN infrastructure based on
licensed spectrum in the 5.85-5.925GHz band. Activity in this area has
been quite limited to date, as the overall implementation is complex,
expensive and requires the appropriate business model if it's ever to see
the light of day.
This specification provides a great example of how different
specifications need to work in concert. Imagine driving down the freeway
at 65 mph. Given the range of a typical access point is several hundred
feet, your client will need to roam from one AP to the next every 5
seconds or so. The specific application of 11p can take advantage of
certain techniques, like beamforming and increased power to perhaps
extend the available range of each AP, but the amount of time spent
connected to each AP will still be in the range of tens of seconds.
[802.11p issues: "Will electronic toll systems become terrorist targets?"]
If a user is only going to be on an AP for approximately 15 seconds
before being handed off to the next, the handoff time needs to be very
short to provide a seamless user experience. Handoff is specifically
addressed in 802.11r, also part of the 802.11-2012 roll-up, so it's
imperative that the capabilities defined in both specifications be
consistent and interoperable.
* 802.11r: Fast BSS Transition (2008). As more amendments have been added
to 802.11, the time it takes to make a "transition" or "handoff" when
moving from AP to AP has degraded significantly, causing problems for
services like voice over Wi-Fi (VoFi). This amendment addresses this
degradation, returning the handoff process to the simple 4-message
exchange as originally designed.
Technology based on 11r is already actively in use, and will become much
more common in enterprise WLAN equipment. Even if customers aren't yet
utilizing their WLAN for voice or video, they'll want to plan for the
future as more and more client equipment (smartphones and tablets) are
shipped ready for handoff from cellular networks to WLANs.
* 802.11s: Mesh Networking, Extended Service Set (July 2011). Mesh
networking specifies an architecture and protocol to create self-
configuring multi-hop wireless networks. These are typically high-
performing, scalable, ad hoc networks, often with no wired access at all.
Proprietary mesh technology has been in use for years, mainly in the
public service/emergency management space where ad hoc local networks
need to be set up in an area with little or no wired infrastructure --
basically temporary field networks. 802.11s will help tremendously in
standardizing this technology, making it more interoperable and more
accessible to wider business applications.
* 802.11u: Interworking with Non-802 Networks (February 2011). This is an
extremely hot topic in mobile computing, and one that will continue to
get tremendous attention. It also requires solutions to solve some pretty
difficult practical problems, including discovery, authentication,
authorization and compatibility, across multiple technologies and
multiple service providers, hence the delivery of compatible products has
been slower than anticipated.
Transition for data delivery is easier and is already fairly widespread.
Most smartphones transition automatically from the cellular data network
to an 802.11 network once users come into range of a network that has
already been configured. Transitioning active telephone calls is much
more complicated and much less common, but the need and the desire for
products to do so is apparent and it is just a matter of time.
802.11u also provides key technology that enables the Wi-Fi Alliance
Passpoint certification program (a.k.a. Hotspot 2.0). This program allows
for the seamless transition of Wi-Fi clients between any hotspot AP that
is certified to be Passpoint compliant, eliminating many of the
complexities that exist today in discovering and connecting to both
public and carrier-sponsored hot spots. Look for 802.11u, and Passpoint
compliant, hardware to be hitting the market very soon. [Also
see: "802.11u and Hotspot 2.0 promise Wi-Fi users a cellular-like
experience"]
* 802.11v: Wireless Network Management (February 2011). 802.11v provides
a mechanism for wireless clients to share information about the WLAN
environment with each other and APs to improve WLAN network performance
in real time. This specification is relatively new, and manufacturers are
just beginning to take advantage of some of its features. As WLANs become
even more heavily utilized, the benefits of 802.11v will certainly become
obvious.
* 802.11w: Protected Management Frames (September 2009). 802.11w
specifies methods to increase the security of 802.11 management frames.
Management frames are 802.11 packets that control communication on the
WLAN, but do not contain data. Currently, management frames are sent "in
the clear." This makes them potentially vulnerable to malicious
manipulation and can lead to a wide variety of WLAN attacks, from client
spoofing (a rogue pretending to be an approved user) to hijacking of all
data destined for one or more APs. 802.11w will significantly reduce
these risks.
* 802.11y: 3650-3700MHz Operation in the U.S. (2008). 802.11y specifies
a "light-licensing" scheme for U.S. users to take advantage of spectrum
in the 3650-3700MHz band, at power levels that are significantly higher
than those used in the 2.4GHz or 5GHz bands. The use case for this
technology will typically be for longer distance, point-to-point,
backhaul communication using 802.11, for example fixed point-to-point
mobile links that may be required in a large-scale, temporary wireless
network (like in an emergency situation), wireless interconnectivity
between buildings in a campus setting, or links between islands of 802.11
hotspots in a municipal environment.
* 802.11z: Extensions to Direct Link Setup (September 2010). Direct link
setup (DLS) allows WLAN client devices to connect directly to each other,
bypassing the typical link through an infrastructure AP. This has many
benefits, including an increase in speed (between the clients), an
increase in network throughput (for all users), and an increase in
overall service delivery, especially for multimedia (like a computer to
DVR connection or a laptop to projector connection). [Also see: "Wi-Fi
Alliance starts certifying tunnel technology for better wireless
performance"]
The Wi-Fi Alliance (WFA) already has a program in place called Wi-Fi
Direct that addresses this functionality, and most commercial devices are
being certified under this program. 802.11z standardizes this behavior,
making it easier for equipment designers to ensure their products can
deliver popular features like Wi-Fi Direct.
The recently ratified 802.11-2012 specification is most certainly a wide-
ranging roll-up. From generic and already prolific technology like
802.11n to highly specific technology like 802.11y, this new
specification integrates all current Wi-Fi technology into a single
specification again, making it easier for developers and testers to find
all the information they need in a single document. And although the
ratification of such a specification may seem trivial to end users of
this technology, they will also benefit, both from tighter feature
integration as well as faster time to market for interoperable 802.11
devices.
--
Cheers,
Stephen
More information about the Link
mailing list