Rolling up developments in Wi-Fi
- 04 December, 2012 14:56
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 10 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, say nothing of the fact that it also helps alleviate interoperability issues between protocols.
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.
WildPackets develops hardware and software solutions that drive network performance, enabling organizations of all sizes to analyze, troubleshoot, optimize and secure their wired and wireless networks. Customers include Boeing, Chrysler, Motorola, Nationwide, and over 80 percent of the Fortune 1000. WildPackets is a Cisco Technical Development Partner (CTDP). For more information, visit www.wildpackets.com.
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