Backgrounder:   Evolution of wireless network standards

1.  WiFi or IEEE 802.11:

The first published standard for Wi-Fi was 802.11-1997 published in 1997. 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:

-Infrared: which provided 1 MB/s throughput
-Frequency Hoping Spread Spectrum: which could provide either 1 or 2 MB/s throughput
-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.  MIMO is realized  with multiple transmitters and multiple receivers.  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

2.  Wireless cellular communications:

The second generation (2G) wireless voice networks of the early 1990s first introduced digital cellular technology, through the deployment of third generation (3G) systems with their higher speed data networks to the much-anticipated fourth generation technology being developed today. Currently there are only two 4G candidates being actively developed today: 3GPP LTE-Advanced (the front runner) and IEEE 802.16m (which is sometimes referred to as WiMAX 2.0).

Currently, LTE Advanced appears to be the 4G technology of choice, based on most wireless operators opting for LTE.  Qualcomm will provide its perspective on cellular network evolution and directions.