What does the future hold in store for us with 802.11 wireless networking? The draft amendments are a looking glass into the future of the enhancements and new capabilities that might be available soon for 802.11 wireless networking devices.
Greater throughput, client control, improved roaming, mesh networking, and more all await us on the wireless horizon. Draft amendments are proposals that have yet to be ratified. Therefore, although some vendors are already selling products that have some of the capabilities described below, these features are still considered proprietary.
For example, if you buy a “pre-802.11n” access point from vendor #1, then the promised increase in throughput capabilities will only be achieved using a “pre-802.11n” client card from that same vendor. Vendor #2’s radio will most likely not be able to communicate in the same manner with vendor #1’s radio.
Also, even though a vendor might be marketing these preratified capabilities, there is no guarantee that the current products will work with future products that are “certified” as compliant with the forthcoming final ratified 802.11n amendment.
The recent ratification of the 802.11e QoS amendment combined with the future approval of the 802.11k, 802.11n, and 802.11r drafts is expected to spark a major convergence of data, voice, and video over the wireless medium. We will give you a glimpse into more sophisticated Wi-Fi products with more advanced capabilities.
802.11k
The goal of the 802.11 Task Group k (TGk) is to provide a means of radio resource measurement. The draft amendment calls for measurable Physical layer 1 and MAC sublayer of the Data-Link layer 2 client statistical information in the form of requests and reports.
802.11k defines mechanisms in which client station resource data is gathered and processed by an access point or WLAN switch. In some instances, the client may also request information from an access point or WLAN switch.
The following are some of the key resource measurements defined under 802.11k: Transmit power control (TPC) The 802.11h amendment defined the use of TPC for the 5 GHz band in Europe to reduce interference.
Under 802.11k, transmit power control will also be used in other frequency bands and in areas governed by other regulatory agencies. Client statistics Physical layer information such as signal-to-noise ratio, signal strength, and data rates can all be reported back to the access point or WLAN switch.
MAC information such as frame transmissions, retries, and errors may all be reported back to the access point or WLAN switch as well. Channel statistics Clients may assemble noise floor information based on any RF energy in the background of the channel and report back to the access point.
Channel load information may also be collected and sent to the AP. The access point or WLAN switch may use this information for channel management decisions. Roaming site reports Mobile Assisted Hand-Over (MAHO) is a technique used by digital phones and cellular systems working together to provide better handover between cells.
802.11k gives access points or WLAN switches the ability to direct stations to perform the sort of tasks that a cellular network requires its handhelds to do when using Mobile Assisted Hand-Over. Using proprietary methods, client stations keep a table of “known access points” and make decisions on when to roam to another access point.
As defined by 802.11k, the access point or WLAN switch will request a station to listen for access points on other channels and gather information. The current AP or WLAN switch will then process that information and generate a “site report” detailing available access points from best to worst.
Before a station roams, it will request the site report from the current AP and then roam to the best access point on the site report. The 802.11k draft in conjunction with the 802.11r “fast roaming” draft have the potential to greatly improve roaming performance in 802.11 wireless networks.
802.11m
The IEEE Task Group m (TGm) started an initiative in 1999 for internal maintenance of technical documentation of the 802.11 standard. 802.11m is often referred to as "802.11 housekeeping," with a mission of clarification and correction to the 802.11 standard. Unless we are a member of Task Group M, this amendment is of little significance to us.
802.11n
An event that is sure to have a major impact on the Wi-Fi marketplace will be the passage of the 802.11n amendment. Since the year 2004, the 802.11 Task Group n (TGn) has been working on improvements to the 802.11 standard to provide for greater throughput.
The IEEE 802.11 standards in the past have always addressed bandwidth data rate; however, the objective of the 802.11n supplement is to increase the throughput in both the 2.4 GHz and 5 GHz frequency band.
The baseline minimum throughput goal is 100 Mbps, although throughput of as much as 600 Mbps may be possible under the right conditions.
802.11n makes use of multiple-input-multiple-output (MIMO) technology in unison with Orthogonal Frequency Division Multiplexing (OFDM) technology. MIMO uses multiple receiving and transmitting antennas and actually capitalizes on the effects of multipath as opposed to compensating or eliminating them.
The beneficial consequences of using MIMO are increased throughput and even greater range. Currently two competing proposals are vying for 802.11n ratification, with companies aligning themselves into two separate consortiums called World-Wide Spectrum Efficiency (WWiSE) and Task Group n-Sync (TGn Sync).
The WWiSE group has the backing of Airgo, Broadcom, Motorola, Nokia, and others. The TGn Sync group includes membership from Atheros, Cisco, Intel, Philips, Symbol, and others. Issues being debated include OFDM channel sizes of possibly 10 MHz, 20 MHz, or 40 MHz and the use of one to four antennas.
Other Physical layer issues such as transmit beamforming as well as MAC layer issues still have these two groups in disagreement. Thankfully, another group called the Enhanced Wireless Consortium (EWC) was formed to help speed up the IEEE 802.11n development process as well as promote the forthcoming 802.11n technology.
Final ratification of the 802.11n amendment is expected in 2007. Passage of the 802.11n draft will give 802.11 enterprise deployments the desired throughput needed by a multiple-user and application-intensive environment.
802.11p
The mission of the 802.11 Task Group p (TGp) is to define enhancements to the 802.11 standard to support Intelligent Transportation Systems (ITS) applications. Data exchanges between high-speed vehicles will be possible in the licensed ITS band of 5.9 GHz.
Additionally, communications between vehicles and roadside infrastructure will be supported in the 5 GHz bands, specifically the 5.850 to 5.925 GHz band within North America. Communications may be possible at speeds of up to 200 kilometers per hour (124 mph) and within a range of 1,000 meters (3281 feet).
Very short latencies will also be needed as some applications must guarantee data delivery within 4 to 50 milliseconds. 802.11p is also known as Wireless Access and Vehicular Environment (WAVE) and is the possible foundation for a U.S. Department of Transportation project called Dedicated Short Range Communications (DSRC).
The DSRC project envisions a nationwide vehicle and roadside communication network utilizing applications such as vehicle safety services, traffic jam alarms, toll collections, vehicle collision avoidance, and adaptive traffic light control. 802.11p will also be applicable to marine and rail communications.
802.11r
The 802.11r draft is often referred to as the fast roaming amendment because the 802.11 Task Group r (TGr) is currently working on a protocol that will define faster handoffs when roaming occurs between cells in a wireless LAN. 802.11r was proposed primarily because of the time constraints of applications such as VoIP.
Average time delays of hundreds of milliseconds occur when a client station roams from one access point to another access point. Roaming can be especially troublesome when using an 802.11i enterprise security solution, which requires the use of a RADIUS server for authentication and often takes several hundred milliseconds.
VoIP requires a handoff of 50 milliseconds or less to avoid a degradation of the quality of the call or, even worse, a loss of connection. Under 802.11r, a station will be able to establish a QoS stream and set up security associations with a new access point before actually roaming to the new access point.
The station can achieve these tasks either over the wire via the original access point or through the air. Eventually the station will complete the roaming process and move to the new access point. The time saved from prearranging security associations and QoS services will drastically speed up the handoffs between WLAN cells.
802.11s
A high-tech story that receives a lot of attention in the media describes blanketing entire cities with Wi-Fi coverage with the goal of citywide wireless access to the Internet. For the most part, the equipment being used for these large-scale 802.11 deployments is proprietary wireless mesh routers or mesh access points.
The 802.11s Task Group has set forth the pursuit of standardizing mesh networking using the IEEE 802.11 MAC/PHY layers. 802.11 access points typically act as portal devices to a distribution system (DS) that is a wired 802.3 Ethernet medium. However, the 802.11 standard does not mandate that the distribution system use a wired medium.
Access points can therefore act as portal devices to a wireless distribution system (WDS). The 802.11s amendment proposes a protocol for adaptive, autoconfiguring systems that support broadcast, multicast, and unicast traffic over multihop mesh topologies in a WDS.
Initially 15 different mesh proposals were submitted for 802.11s, although proposals from 2 major vendor alliances seem to have taken the lead. One consortium called Simple, Efficient and Extensible Mesh (SEEMesh) is backed by companies such as Intel, Motorola, Nokia, Texas Instruments, and others.
The other major consortium is the Wi-Mesh Alliance (WiMA), whose membership includes Extreme Networks, Nortel, NextHop Technologies, Philips, Thomson, and more.
802.11T
The goal of the IEEE 802.11T Task Group (TGT) is to develop performance metrics, measurement methods, and test conditions to measure the performance of 802.11 wireless networking equipment.
The 802.11T draft is also called Wireless Performance Prediction (WPP), with the final objective being consistent and universally accepted WLAN measurement practices. These 802.11 performance benchmarks and methods could be used by independent test labs, manufacturers, and even end users.
802.11u
The primary objective of the 802.11 Task Group u (TGu) is to address interworking issues between an IEEE 802.11 access network and any external network to which it is connected. A common approach is needed to integrate IEEE 802.11 access networks with external networks in a generic and standardized manner.
802.11u is also often referred to as Wireless InterWorking with External Networks (WIEN). This amendment may well address seamless handoff and session persistence with other external networks such as the Internet, cellular networks, and WiMAX.
Proprietary equipment such as hybrid telephones that allows for roaming between an enterprise WLAN and the wide area cellular networks are currently being developed. The 802.11u draft may one day standardize the procedures needed for the interworking between two very different networks.
802.11v
While 802.11k defines methods of retrieving information from client stations, 802.11v will give us the ability to configure client stations wirelessly from a central point of management.
The main goal of the IEEE Task Group v (TGv) is for WLAN infrastructure (access points and wireless switches) to take improved control of wireless client stations.
The following list includes some of the 802.11v proposals currently being discussed: Wireless client control SNMP Management Information Bases (MIBs) for client station attributes are currently being defined under 802.11v.
This will give the ability to configure and manage clients wirelessly from a WLAN infrastructure device. Load balancing Enterprise WLAN deployments often encounter disproportionate associations of client stations between access points.
This can cause an uneven distribution of available bandwidth and result in throughput problems. Currently, vendors implement proprietary load-balancing procedures to alleviate these problems. 802.11v may standardize and simplify load balancing.
Network selection In order to join a wireless network, a client station radio card must be preconfigured with a profile that matches all the security credentials on the infrastructure side. 802.11v may provide mechanisms to implement client-side security settings from the WLAN infrastructure.
802.11w
One common type of attack on an 802.11 wireless LAN is a denial of service attack (DoS attack). There are a multitude of DoS attacks that can be launched against a wireless network; however, a very common DoS attack occurs at layer 2 using 802.11 management frames.
Currently it is very simple for an attacker to edit deauthenication or disassociation frames and then retransmit the frames into the air, effectively shutting down a wireless network.
The IEEE Task Group w (TGw) is working on a “protected” management frame amendment with a goal of delivering management frames in a secure manner. The end result will hopefully prevent many of the layer 2 denial of service attacks that currently exist.
