In the World Today, Wireless Networks Are Becoming More and More Common

1

Wireless Networking and the 802.11n Standard

Roman White and Pratt Hinds
In the world today, wireless networks are becoming more and more common. They can be found in homes, coffee shops, universities, and airports, to name a few. More and more people around the world are able to connect to the Internet using their desktops, laptops, smart phones, and all sorts of portable devices at hot spots at these places, as well as entire cities, such as Mountain View, California, that offer free Wi-Fi access to residents.

Wireless networks use radio waves to communicate, as do cellular phones, televisions, and radios. A computer’s wireless adapter converts data from its binary form into a radio signal, which is transmitted to the antenna on a router which decodes the signal back into binary form, and sends it through a physical line to a modem for modulation and transmission. The reverse is true for the return process. Data is sent to the modem where it is demodulated and sent through a physical line to the router, where it is converted to a radio signal and transmitted to a receiver on the computer’s wireless adapter. The adapter then decodes the message back into its binary form (Brain, n.d.).

Wireless communication started at the end of the 19th century, into the beginning of the 20th century when Guglielmo Marconi established the Wireless Telegraph and Signal Company in 1896. By the year 1901 radio transmissions were being sent over the Atlantic Ocean. Wireless technology was found to be especially useful for military applications, such as in World War II, in order to transmit messages to troops behind enemy lines. During the 1950s, the Bell Telephone Company started making the radio network accessible for consumers. In 1971, the University of Hawaii developed ALOHAnet, a method of wirelessly transmitting between a central hub and clients. In the early 1980s, the Advanced Mobile Phone Service became the radio telephony standard for the United States. Finally, in the late 1990s, a standard was developed for the use of Wi-Fi: 802.11 (Wireless Networking, n.d.).

The 802.11 standard was created in 1997 by the Institute of Electrical and Electronics Engineers. 802.11 has a data transfer rate of on average 1 megabit per second, while the maximum achievable data transfer rate is 2 megabits per second. It uses the 2.4 GHz frequency band, which is the same frequency used for many devices such as cell phones, walkie-talkies, and televisions. As a medium access method, 802.11 uses carrier sensing multiple access with collision avoidance. With this method, a transmitter can check to see if there is currently any data being transmitted for it to collide with. If there is, the transmitter will wait a random amount of time to check the channel again to see if it is free to send. 802.11 was the original standard created, but there are techniques that have been defined in amendments to the standard that have become more popular than others. These more popular techniques are those in the a, b, and g amendments. 802.11b was the first widely accepted standard, which was then followed by a and g (IEEE 802.11, n.d.).

The 802.11a amendment to the standard was added in 1999. It has some advantages and some drawbacks when compared to 802.11. One large advantage is that 802.11a has average expectable data transfer rates of 25 megabits per second, with a maximum of 54 megabits per second. Another slight advantage is that 802.11a uses the 5 GHz frequency band for transmission. The higher frequency allows for higher data transfer rates and less interference as less devices use this band. The higher frequency also is a disadvantage because it is absorbed more easily, penetrates less, and almost requires line-of-sight from the transmitter to the receiver. It was not quite as popular as its successor, the 802.11b, as the 802.11a’s 5 GHz components were not as available as other components, as well as it having a short range and poor starting product implementations.

The 802.11b amendment was also added in 1999. It has a data transfer rate typically around 6.5 megabits per second with a maximum data transfer rate of 11 megabits per second. This puts it faster than the original 802.11, but slower than 802.11a. Like the original 802.11, it uses the 2.4 GHz frequency band and the carrier sensing multiple access with collision avoidance protocol.

In 2003, the 802.11g amendment was added. 802.11g contains some of the strengths and weaknesses of the 802.11a and 802.11b standards. Like the 802.11a, the 802.11g has an average data transfer rate of 25 megabits per second and a maximum data transfer rate of 54 megabits per second. Like the 802.11b, the 802.11g uses the 2.4 GHz frequency band. This puts it in danger of receiving interference from other devices, but it makes the 802.11g compatible with 802.11b components.

The latest amendment to be put up for consideration for ratification is the 802.11n standard. The 802.11n standard has been under development since mid-2005. Current theoretical limits put the 802.11n at speeds fifty times faster than the 802.11b, and ten times faster than the 802.11a and 802.11g, with an estimate of 540 megabits per second.

802.11a, 802.11b, and 802.11g originally used one antenna. Most recently, some manufacturers have begun implementing MIMO (multiple in, multiple out) in some 802.11g devices. To the right is D-Link’s DI-634M Wireless 108G MIMO Router. Many vendors have begun implementing MIMO to improve range and signal capacity. The maximum data throughput using the 802.11g standard has been 108mb.

802.11n is boasting to achieve a theoretical 600mbps. Actual throughput will initially be closer to 200mbps. This will place 802.11n on par with and more appealing than Fast Ethernet (100mbps wired Ethernet). At 200mbps it will be possible to stream high quality video and voice over a wireless signal. Some vendors are already selling “Pre-N” products including Belkin, D-Link, Netgear, Asus, and Linksys. However since these are “Pre-N”, they are not guaranteed to be compliant with the 802.11n standard when it is released. Most of these vendors are promising firmware update support to help them be compatible with the final standard.

The 802.11a standard was formed in 1999 and achieves a maximum throughput of 54mbps, with a 5 GHz frequency range. 802.11b came out the same year with 11mbps at a 2.4 GHz range. In 2003, 802.11g was made a standard and worked at the same 2.4 GHz and achieved 54mbps as well (Vaughan-Nichols Pg. 17).

The 802.11n standard will work at 2.4 GHz, making it easily backwards compatible with the b and g standards. This will make 802.11n flexible enough to be used alongside and integrate into existing wireless networks. This will be ideal for colleges and businesses alike. It will enable video conferencing over wireless (Panettieri Pg. 40). Large file transfers will become much more reliable and faster.

As seen in figure 3, 802.11n’s range will vastly outperform the previous standards. With the increased range and a higher data rate, 802.11n will be able to provide the speeds of wired Ethernet with the flexibility of wireless. Everything from the before mentioned video conferencing, to high end graphics intensive gaming will be possible over wireless connections. File sharing through a wireless connection will no longer be sluggish and risky.

MIMO resolves the multiple redundant radio signals caused by signals deflecting off objects. This resolution allows the wireless network devices to use the antennas as multiple data paths, similar in concept to adding more wires for data transfer. This is how high data rates are achieved. This is also how the range is increased. (Vaughan-Nichols Pg. 16)

In an October 2006 article in Computer, a publication of the IEEE Computer society, the future of wireless is discussed. Craig Mathias from Farpoint, a wireless consulting firm, said “With the technology’sperformance advantages802.11a, b, and g will disappear.”

Vaughan-Nichols goes on to quote Gemma Tedesco, a senior market research analyst with In-Stat, “802.11n is the future,and eventually, all productsegments will shift to this standard.” (Vaughan-Nichols Pg 18)

It is inevitable for the other wireless standards to be replaced, and with products based off of drafts of the 802.11n standard, why hasn’t there been a standard yet?

The “N” standard has had a very rocky road. Figure 5 shows a few of the obstacles that 802.11n has had to overcome. TGnSynch supported a 802.11n solution that would achieve a possible 600mbps rate. WWiSE wanted a more backward compatible solution that would yield 540mbps. TGnSynch and WWiSE could not agree upon how to implement 802.11n and finally disbanded in 2005 (Vaughan-Nichols Pg 17). Various members from both groups (Atheros, Broadcom, Intel, and Marvell) joined together and made the EWC (Enhanced Wireless Consortium). Since its formation the EWC has been joined by Mitsubishi, Motorola, and Qualcomm who have abandoned their own efforts of 802.11n proposals. (Vaughan-Nichols Pg 17)

There are still disagreements on the implementation. Airgo, leader of the former WWiSE, has not joined the EWC and claims that the EWC’s proposal will interfere with existing wireless networks. IEEE’s TGn may not be able to make a vote soon due to 12,000 comments on the most recent draft proposal. Currently the earliest projected date for standardization of 802.11n is not until 2008. (Vaughan-Nichols Pg 18)

Meanwhile, Vendors begin fighting for market control with Pre-N products. Mathias stated that due to Pre-N sales many vendors will not feel the need to agree upon a standard. Those that decide to buy Pre-N products do so at their own risk. Currently, Asus is guaranteeing free firmware and hardware upgrades to make their devices 802.11n compliant when it is made a standard. (ASUSTek) Still, if you miss the three month window after the standardization, AsusTek will not provide a free support. Also, if it does require a hardware upgrade, the buyer is responsible for shipping the item.

802.11n may be the future of wireless networking and many vendors are eagerly seeking market dominance, but it will be some time yet before and standardization is reached. When it is reached, though, it will revolutionize wireless networks and propel connectivity to new levels.

References

Blandford, Jameson (2006). 802.11n spec shifts into high gear. Network Computing, 17 (18), 20-22.

Brain, Marshall, & Wilson, Tracy V. How WiFi Works. Retrieved December 1, 2006, from

IEEE 802.11. Retrieved December 1, 2006, from IEEE_802.11.

Kish, William (2006). What They Don’t Tell You About 802.11n. Wireless Week, 12 (21), 37.

Matta, Sudheer (2006). 802.11n speeds wireless LANs. Network World, 23 (42), 31.

Molta, Dave (2006). 802.11n: Good Luck. Network Computing, 17 (18), 14.

Nobel, Carmen (2006). 5 Things You Need to Know About 802.11n. VARBusiness, 22 (19), 53-56.

Newman, David (2006). Breaking the Standards. Network World, 23 (43), 42.

Panettieri, Joseph C. (2006). Wireless: The ‘n’ is near. University Business, 9 (11), 38-43).

Quain, John R. (2006). A Wi-Fi Express Lane. New York Times, 156, 11.

Understanding the Basics of MIMO Systems. Microwaves and RF, 45 (10), 100.

Vaughan-Nichols, Steven J. (2006). Will the new Wi-Fi fly? Computer, 39 (10), 16-18.

Waring, Becky (2006). The truth about superfast Wi-Fi. PC World, 24 (10), 116-130.

Wireless networking. Retrieved December 1, 2006 from

Wireless standards. MarketWatch, 5 (10), 176-177.