Wireless standards by the bushel
There’s no shortage of new wireless standards that either are under discussion or in the process of being finalized by the Institute of Electrical and Electronics Engineers, IEEE.
Under the 802 category of IEEE WAN/MAN networking standards, there are a total of 11 working groups with four dedicated to formalizing wireless standards and a fifth — the 802.18 group — focuses on radio regulatory issues around the globe.
In addition, the 802.19 working group deals with coexistence issues with existing and-in development standards.
If that’s not enough fun, each working group has sub-topics — projects — within their category.
For example, the 802.11 Wireless LAN working group has projects ranging from 802.11a 5GHz and 802.11b 2.4GHz Wi-Fi standards to the recently introduced 802.11g 2.4GHz standard. Two standards efforts of looming interest are the 802.16 Broadband Wireless Access “WirelessMAN” working group and the 802.20 Mobile Wireless Broadband Access working group.
The WirelessMAN effort encompasses a set of standards to allow interoperability for outdoor “first-mile/last-mile” broadband wireless connections. With ranges up to 30 miles and data rates up to 70 Mbps using frequencies between 10 to 66GHz, WirelessMAN defines a medium access control (MAC) layer that supports multiple physical layer specifications customized for the frequency band of use. It supports continuously varying traffic levels at many licensed frequencies (e.g., 10.5, 25, 26, 31, 38 and 39 GHz) for two-way communications and enables interoperability among devices, so carriers can use products from multiple vendors. A separate amendment covers the 2-11GHz region for both licensed and unlicensed bands and incorporates both obstructed line-of-sight and non line-of-sight transmission protocols. The 10-66GHz air interface definition for WirelessMAN was published in April 2002 while the amendment covering 2-11GHz came out in April 2003. More detailed specifications spelling out test suites and radio conformance with existing applications for 10-66GHz are in progress.
Building in quality of service mechanisms is a significant effort for the WirelessMAN group, since free space wireless transmissions can be affected by mundane factors such as vegetation, buildings, weather (rain or fog), and vehicles. Incorporating QoS mechanisms within the MAC layer allows for the efficient adoption of a connection to support data, voice, and video applications. WirelessMAN supports adaptive modulation to balance data rates and link quality and can be adjusted almost instantaneously for optimum data transfer. The standard also supports both frequency and time division duplexing (FDD and TDD). FDD requires two channel pairs, one for transmission and one for reception, with some frequency separation between them to prevent self-interference. TDD providing a highly flexible duplexing scheme for regulatory environments where structured channel pairs do not exist. A TDD system can dynamically allocate upstream and downstream bandwidth depending on traffic requirements.
The 802.11a standard is designed to be scalable as well, with supports for hundreds and even thousands of users per available channel. Base station operators will be able to reallocate spectrum through sectorization and cell splitting. Mesh networks and various forms of antenna techniques can be applied to improve coverage even further.
Vendors have formed the WiMax industry group to promote the use of the 802.16 standard, certify interoperability, and “achieve global acceptance;” in other words, to sell lots of units around the world. At present, 28 vendors have signed up, including heavy hitters Fujitsu, Intel, Intel and Proxim. Wireless market research firm Visant Strategies projects the market for WiMAX equipment will exceed $1.6 billion by 2008, so there’s a lot of potential business at stake over the next five years. Intel has been especially aggressive.
One of WiMax’s challenges is to ensure compatibility with the IEEE 802.16 standards and existing European technical standards under the HiperMAN standard. WiMAX will initially focus its conformance and interoperability testing on equipment that supports the 256 OFDM physical layer and operates in 2.5 GHz and 3.5 GHz licensed bands and 5.8 GHz unlicensed band.
Another area being examined under the 802.16 banner is support for mobile broadband wireless connectivity, under the label of “802.16e Mobile Wireless MAN.” A timeline for discussion and review was published in September 2003 and a final standard may be published in October 2004. The 802.16e specification will only address licensed bands between 2-6 GHz for data rates possible at “vehicular” speeds, such as cars, trucks, and trains. The cost of including the hardware for a 802.16e receiver into a laptop computer or PDA is expected to be affordable compared to the total cost of the device.
However, 802.16e is not the only effort underway to establish mobile wireless broadband standards. The 802.20 Mobile Broadband Wireless Access (MBWA) group was chartered in December 2002 to examine alternatives to existing 3G cellular data schemes. The specification is focused on vehicle applications and features of the project include interoperable mobile systems operating in licensed bands below 3.5 GHz. According to the initial documents, the goal is to obtain peak download data rates of 4 Mbps and upload data rates of 800 Kbps at speeds of up to 150 miles/hour.
In addition, the 802.20 project will be designed to get better spectral efficiencies, sustained user data rates and numbers of active users all significantly higher than existing mobile systems. At least two hardware encryption methods have been presented for consideration.
If all goes according to plan, the MBWA standard will be approved by Dec. 10, 2004, but draft hardware close to the specifications may already be in existence if the attendees at the latest working session are any indication. ArrayComm has demonstrated data rates of up to 1 Mbps using their existing hardware and already have over 150,000 base stations deployed worldwide. Flarion Technologies has teamed with Northrop Grumman on a proposal to run a 10 Mbps wireless network on the 700 MHz band for a universal homeland security data network capable of being used at speeds from 0 to 150 mph = a range that covers everything from a stationary command post to a helicopter or UAV. Using licensed bands, IP Wireless can deliver up to 3 Mbps either to a PC-Card or external modem and is partnering with Alcatel and several Asian firms for deployment.
Creating standards is not a slow or easy process. For example, an initial proposal for what would become the 802.11g wireless standard started on March 2000 at an IEEE 802.11b Higher Rate study group. Presentations to the new 802.11g group were conducted in October 2000 and filtered down to two different approaches by Intersel and Texas Instruments in March 2001 with a first draft of the new standard made available in November. After going through six separate rounds of voting and comments, the finalized standard was published on July 2003, a slippage of seven months from an original estimate of finishing in January 2003. Often, major vendors end up split between supporting separate technical approaches and forcing others to take sides.
In addition, standards evolve over time, with earlier versions falling out of favor while faster ones continue to be developed. Ethernet, the “original open standard” first adopted by IEEE, was first published in 1985 as 802.3 and delivered over co-axial cable. Since then, Ethernet has “migrated” onto twisted-pair copper (i.e. telephone) wire, accelerated to 100 Mbps on copper and can be found on optical fiber at speeds up to 10 Gbps.
