The evolution and future of Wi-Fi (Part 1)

by [Published on 10 Sept. 2009 / Last Updated on 10 Sept. 2009]

Wi-Fi began in 1997. Today, the technology has evolved and we now have 802.11n. This article describes some of the basics of this new technology, accompanied by a short outline of its evolution.

If you would like to read next part of this article series please go to The evolution and future of Wi-Fi (Part 2).

Introduction

The Institute for Electrical and Electronics Engineers (IEEE) standard 802.11, more commonly referred to as Wi-Fi, began in 1997 with the IEEE's introduction of the standard system. This “standard” has evolved over the years and today we have a version (well, at least a draft version as I write this article) known as 802.11n. In this article I will explain some of the basics of this technology and give an outline of its evolution.

Institute for Electrical and Electronic Engineers

Let us start with a brief explanation of what the IEEE is. The IEEE is, at its core, a standards organization. It consists of many Electrical and Electronics Engineers (many with advanced degrees from some of the World's most prestigious Universities) who are experts in their respective fields. It is important to have standards with widespread adoption to ensure interoperability. In fact, this is one of the more difficult tasks for the IEEE, ensuring widespread adoption; a task they do not always seem to accomplish. The standards published by the IEEE encompass all areas of Electrical Engineering including computer networking. When one analyzes these standards it is important to remember that performance is often not the penultimate design goal of the standard. In fact the standard may be far from perfect. However, as I suggested earlier, a standard is only valuable if it has widespread adoption; this goal trumps all others during the design of the standard.

The IEEE subcommittee this article is concerned with is the LAN/MAN subcommittee. This subcommittee has been given the designator 802, and so each standard decided upon by this committee will begin with the designator 802. The 11 of 802.11 means that the standard involves over-the-air modulation; all standards denoted with 802.11 will therefore have been published by the 802 subcommittee and use over-the-air modulation. You will often see 802.11, and many other standards for that matter, written with a date following the designator such as 802.11-1997. This date is the date of the publication of the standard. As the standard evolves the subcommittee will publish updates and this date will change to refer to the most recent publication. Also, you will often see these designators described along with a lower-case letter such as 802.11b. These lower-case letters denote amendments made to the originally published standard. In the case of 802.11 the letters are given to amendments which have been approved to give the 802.11 technology either greater speed, increased range, better reliability, or any combination of the three.

802.11-1997

The first published standard for Wi-Fi was 802.11-1997 published, of course, in 1997. Remember when I said that the IEEE does not always succeed in its goal for widespread adoption? This is one such case. The original standard received very little recognition. In part this was due to its relatively low bit rate of 1 or 2 MB/s. The actual bit rate depended on the physical link used to transmit the data. The 802.11-1997 standard allowed for three alternative technologies to be used:

  1. Infrared: which provided 1 MB/s throughput
  2. Frequency Hoping Spread Spectrum: which could provide either 1 or 2 MB/s throughput
  3. Direct Sequence Spread Spectrum: which could also provide either 1 or 2 MB/s throughput.

While the low adoption rate of this technology standard was due in part to the low bit rate, it was also due in part to the expense of the technology. In 1997 the transmitters and receivers required to use the 802.11-1997 standard were quite expensive, and that was on top of computers which, at the time, were also quite expensive (especially laptop computers, which due to their mobility have the most to gain from Wi-Fi technologies). It wasn't until the 802.11 standard was updated in 1999 with the 'a' and 'b' designators that Wi-Fi technology gained widespread adoption. However, while 802.11a and 802.11b were published simultaneously in 1999 it was only 802.11b which gained widespread acceptance.

802.11a and 802.11b

802.11a was an improvement over 802.11-1997 because of its increased throughput. While 802.11-1997 could only transmit data at 2 MB/s, 802.11a could transmit data at 54 MB/s. This increase in the data transfer rate was due mostly to the use of the 5 GHz frequency as opposed to the 2.4 GHz frequency used in 802.11-1997 (that was the frequency used for the Frequency Hoping Spread Spectrum and the Direct Sequence Spread Spectrum options; not the Infrared option). Apart from the increase in speed, another advantage of using the 5 GHz frequency was that, at the time, there were not very many devices using that frequency so there was less interference. However, the use of the 5 GHz band had one major draw-back. Since the 5 GHz frequency uses shorter wavelengths (the frequency is inversely proportional to the wavelength; so the higher the frequency the shorter the wavelength) the technology had a shorter range and the signals could not easily pass through walls. Generally all objects have an easier time absorbing radio waves of shorter wavelengths, which means that signals traveling with short wavelengths will have a harder time traveling through walls; also even without walls if the signal is traveling in a space with a lot of objects (desks, chairs, etc.) the signal will degrade quickly.

802.11b inherits Direct Sequence Spread Spectrum from the original 802.11-1997 standard, along with an operating frequency of 2.4 GHz. The continued use of the 2.4 GHz frequency was both a benefit and a drawback. It was a benefit because this frequency is unregulated and therefore was cheaper for manufactures to implement. It was, and is, a drawback because there are many devices which use this frequency (baby monitors, cordless phones, etc.) all of which can interfere with each other. 

The major change in 802.11b was the maximum data rate. The maximum data rate of 802.11b is about 11MB/s, which is comparable to the traditional Ethernet speeds widely available in 1999 and 2000. This increase in speed meant that many consumers could use Wi-Fi, receive all of the benefits of mobility, and no drawbacks in speed. This along with significant price reductions in the technology resulted in widespread adoption of the 802.11b technology.

802.11g

As Ethernet speeds increased, so too did the 802.11 standard. In 2003 the IEEE ratified the 802.11g standard. 802.11g operates at the 2.4 GHz frequency, like 802.11b and 802.11-1997, but it uses the Orthogonal Frequency Division Multiplexing (OFDM) used by 802.11a. This OFDM allowed 802.11g to operate at 54 MB/s; a significant increase over 802.11b's 11 MB/s. Like 802.11b, 802.11g gained widespread adoption amongst consumers and businesses alike.

802.11n

The latest and greatest standard is the 802.11n standard. This standard has yet to be ratified and currently exists in draft form. This, however, has not stopped manufactures from offering products based on this technology. I would not worry about it changing before ratification though, all indications point to the current draft standard being ratified in November 2009. The major evolution of the technology seen in 802.11n is Multiple Input / Multiple Output (MI-MO). I will talk about 802.11n in more detail in my next article, but as you can probably guess from the name MI-MO, 802.11n works with multiple transmitters and multiple receivers; basically if you have two transmitters and two receivers the transmitter can split the signal in half, transmit both halves at the same time and the receiver will receive both halves at the same time, recombine the halves and have the full transmission in basically half the time; this of course effectively doubles the data rate; but I will explain this further in my next article.

If you would like to read next part of this article series please go to The evolution and future of Wi-Fi (Part 2).

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