Where do the Standards come From?
Photo: Wireless Conference
Two organizations are responsible for setting and certifying the wireless standards. The Institute of Electrical and Electronics Engineers (sometimes called Eye-triple-E) is an international, nonprofit, technical professional organization. The Wi-Fi (wireless fidelity) alliance is a membership organization founded in 1999 that certifies product compliance to the IEEE 802.llx wireless standards. Over two hundred companies are members of this non-profit organization. While the IEEE exists to define and promote standards among engineers, the Wi-Fi Alliance exists to promote these same standards to the public through product testing, certification, and the use of the consumer-friendly term "Wi-Fi" in place of 802.llx standard numbers.
The IEEE produces standards through consensus-based working groups. When the IEEE approves and publishes a standard, industries use it as a blueprint for developing compatible products, processes, or solutions.
Because of IEEE standards, we have the ability to choose between different vendors for WLAN equipment, or even good old Ethernet equipment (IEEE 802.3x standard). The alternative would be multiple incompatible standards and proprietary technologies. In short, because of IEEE standards, you can shop around for great deals, mix and match equipment (to some extent), and be sure that your IEEE 802.1 Ix WLAN will operate.
The Wi-Fi alliance promotes the use of wireless technology worldwide by encouraging manufacturers to comply with the 802.1 lx standards when designing their networking products. The Wi-Fi Alliance also promotes 802.llx technology to home, SOHO, and enterprise consumers, has networking products independently tested to ensure that they are compliant with the 802.llx standard, and tests interoperability between certified products.
If a network component carries the Wi-Fi certified logo, it operates with other Wi-Fi certified products that operate in the same frequency range. This gives consumers a choice when shopping for WLAN products, enabling you to mix components from different manufacturers when building your WLAN.
on the web: For more information about Wi-Fi, visit the Wi-Fi Alliance Web site at
www.wi-fi.org.
Standards address different aspects of wireless networking. Some refer to frequency and encryption while others address quality of service or are extensions of previously existing standards. Standards define each of the three layers of a WLAN network model: infrastructure, Media Access Control, and physical.
Note: I refer to the standard 802.11 protocols as 802.11 x, except where I am speaking about a specific standard (for example, 802.11 b), and I use the term Wi-Fi in reference to the standards 802.11 b, 802.11a, and 802.11g.
Performance and Interoperability:
For WLAN devices to operate on the same network, they must use compatible standards and operate on the same frequency. Even though they are both Wi-Fi standards, 802.11b (2.4 GHz) products do not communicate with 802.11a (5 GHz) devices. They don't broadcast on or listen to the same frequency channel.
When designing your WLAN, be sure to purchase devices that operate on the same frequency and that adhere to the same standard. Some incompatible standards that
share the same frequency with 802.llx devices can interfere with data transfer on a Wi-Fi network.
Insider insight: Although 802.11 x devices operate only with compatible devices that use the same frequency band (such as 2.4 GHz), certified products that can operate in both the 2.4 GHz and 5 GHz frequencies have recently reached the market This means that a dual band AP can communicate with an 802.11 b or 802.11a NIC If you have existing WLAN equipment, purchasing a dual band AP would enable you to upgrade to a faster 802.11a (more expensive) network in stages, while still being able to use your older (and much cheaper) 802.11b hardware. In the future, these dual band devices are likely to dominate because of the extended functionality they offer.
Physical Layer Standards
You only need to concern yourself with physical layer standards when deciding on a standard to use for your WLAN; The 802.11 specifications currently describe three physical layer standards for WLANs: 802.11b, 802.11a, and 802.llg. These standards have risen to dominate the market. Adding to the confusion, IEEE did not approve these standards in alphabetical order: 802.11b predates 802.11a.
802.11b:
Also known by the consumer-friendly name "Wi-Fi" (Wi-Fi now also includes 802.11a and 802.11g), 802.11b came on the scene in 1999, competing with the rival standard HomeRF. 802.11b has since risen to dominate the home and SOHO market. The result is an abundance of 802.1 lb-compliant devices available to consumers. This means that the cost of 802.11b equipment is relatively inexpensive.
802.11b devices operate in the unregulated 2.4 GHz radio band, which means that unlike a ham radio, consumers do not need a license to operate the equipment. Although 802.11b allows for operation of 11 channels within the spectrum, devices usually utilize three to limit interference between access points. The maximum link rate is 11 Mbps, but heavy traffic on the same channel can significantly reduce maximum throughput. The data rate also decreases the farther you get from an access point (AP).
Insider insight: Marketing departments often use the terms data rate and throughput changeably when promoting the speed of a networking device, or use data rate as if it were the actual speed when it really represents the capacity. This has led to a lot of confusion, even among IT professionals, so you're in good company if this has left you scratching your head.
Data rate refers to the number of bytes of data transferred in a specified unit of time. For example, an 802.1 lx device operating at 11 Mbps (millions of bits per second), has the capacity to deliver 11 Mbps of data. The data rate is not the true measure of speed on a WLAN, or any network for that matter.
What really measures speed and performance is the throughput of a connection. You can calculate throughput by determining the amount of information sent over time. Many factors affect throughput, including number of users on a WLAN, interference, and latency of connections {latency is the amount of time it takes for data to travel between devices)
Throughput is always less than data rate, without exception. Often, actual throughput is less than half the data rate; therefore, users on an 11 Mbps WLAN may have an actual throughput of 6 Mbps or less. Being able to distinguish between these two terms will aid you when designing your WLAN, and will help you make smart buying decisions
802.11b also shares the 2.4 GHz band with other consumer electronic devices, including cordless phones and microwave ovens. When operating, these devices may interfere with 802.11b WLAN function.
802.11:
Another Wi-Fi standard, 802.11a, operates in the 5 GHz radio band, which is free from interference from other household electronic devices (for the time being). It has a maximum throughput rate of 54 Mbps almost five times faster than 802.11b. Unfortunately, 802.11a can only achieve this speed at a short distance from an access point; less than 30 feet is a good approximation. If you need to cover a wide area with Wi-Fi access, 802.11a may not be the best choice unless you are willing to invest in multiple access points.
Because it operates on a different frequency, 802.11a is not backward compatible with 802.11b, and upgrading requires you to purchase new equipment. Dual band equipment is available, these devices can operate on both 802.11b and 802.11a networks.
802.11g:
This is the newest addition to the 802.llx physical layer standards. 802.11g is an extension to 802.1 lb and provides the throughput of 802.11a, but operates in the same 2.4 GHz band as 802.11b. 802.llg is backward-compatible with 802.11b and devices for both standards can coexist on the same WLAN. However, for full throughput speed on a computer using 802.llg cards, you must have an 802.llg access point. An 802.llg access point can communicate with slower 802.11b cards, enabling you to continue to use them and upgrade as you see fit. 802.llg is susceptible to the same interference issues as 802.11b because it operates in the same 2.4 GHz band.
Insider insight: Because it offers the same speed advantages and is backward-compatible with 802.11 b, you may think that 802.11 g is a good alternative to 802.11a. In some cases it is, especially in a small WLAN in a home or SOHO environment, but when system capacity is important; 802.11a has the advantage. 802.11a has more channels available and can support more traffic. In a busy network environment 802.11a is a better choice, and ensures that you will be able to run mission-critical applications.
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