Wireless Technologies Made Easy

The purpose of this note is to provide a short primer on wireless technologies that even a layman can understand. While writing this note I have consciously tried to avoid complex technical jargons.

GSM Technology

It is popularly known as 2G (2nd Generation) technology. The developers of this technology were inspired by wireline technology which connected each subscriber to the switch by a dedicated copper wire. Hence, to emulate this design, they sliced the wireless spectrum into narrow virtual "nailed up" connections, which block wireless resources even when there is no traffic to carry, thereby using spectrum very inefficiently. To make up for this inefficiency, the towers are closely packed together, thereby increasing operational cost. However, it has some advantages too. The most important one is that it is not overwhelmed by fragmented spectrum, as it is able to aggregate spectrum in smaller chunks of 0.2 MHz. But on the flip side making it unsuitable of carrying data.

CDMA Technology

It laid the foundation for 3G technology. To support that objective it used a revolutionary design which prevented wastage of wireless resources by releasing the "nailed up" connections to the common pool when they aren't used (i.e when the callers are thinking and not talking). This increased the spectrum efficiency (ability to pack users) significantly. Hence, it needed fewer towers compared to its GSM counterpart, for serving similar subscriber density (lower operational costs). It uses a minimum carrier size of 1.25 MHz (6 times of GSM) and therefore is capable of carrying data at a higher speed compared to GSM.

3G Technology

Its design is identical to that of CDMA but used a higher carrier size of 5 MHz (25 times of GSM). Hence, it is capable of carrier data at a much higher peak speed. All other characteristics are similar to that of CDMA. Just like that of CDMA, all towers are tuned to the same frequency making network planning much easier, where in the case of GSM, the adjacent towers are tuned to different frequencies to manage interference.

4G Technology

In order to drive higher speeds, it uses a different design compared to that of 3G. Here also the adjacent sites are tuned to the same frequency, but the interference is managed dynamically by preventing neighboring cell sites to transmit at the same frequency spots within the larger block of continuous spectrum. Since the spectrum efficiency plateaus as the technology evolve, the only way to get higher speeds is by aggregating larger chunks of spectrum. 4G technology has been configured for that purpose. Hence, to unlock the full potential of 4G technology, one must have a larger block of continuous spectrum (10 to 20 MHz).

5G Technology

In order to drive still higher speeds, there is a need to aggregate much larger blocks of continuous spectrum (>20 MHz). 5G technologies are designed for this capability. Since it is hard to find such larger blocks in the lower spectrum bands (< 3 GHz), the 5G technologies are forced to use higher spectrum bands (>6 GHz). This poses another challenge to overcome, i.e poor propagation characteristics of the higher spectrum bands (radio waves attenuates must faster at these higher frequencies). Hence, 5G technologies are empowered with beam steering capabilities, where the sites are programmed to dynamically follow the users by using narrow high power beams, as the users move within the cell.

WiFi Technology

This technology was developed to enable the users to use wireless spectrum without going through the complex regulatory process of acquiring spectrum. A portion of radio spectrum is earmarked for this purpose. Since the spectrum is meant for uncoordinated use (free for all), and therefore, special techniques are required to manage interference. In order to do that, the WiFi router keeps dynamically searching for the best frequency block (with minimum interference) to communicate with the end devices. In the process, a large chunk of spectrum gets wasted (20 times of the carrier size). The carrier size used here is typically 20 MHz, and therefore 400 MHz of spectrum needs to blocked at a time for the system to function properly. Since such large chunks of spectrum are only available at higher frequency spectrum band, therefore, WiFi cannot be efficiently deployed in the lower spectrum bands (< 1 GHz). This also explains why most wireless technologies use only licensed spectrum bands, and why these bands are priced so high.

Satellite Technology

Satellite technologies pose two challenges, a) the mobile needs to transmit at high power for the signals to reach the satellite located in the sky (hundreds of kms away), b) frequency reuse become very difficult and therefore needs a large quantum of spectrum compared to their terrestrial counterparts. Hence, satellite technologies are best suitable for broadcast where the receivers are only in the receive mode, or for serving remote areas which cannot be covered efficiently using conventional technologies.

IOT Technologies

IOT (Internet of things) technologies can use the same wireless technologies used for supporting conventional services. They can also use a different dedicated spectrum. The key difference between them and the conventional mobile is that they are programmed for greater reach and much lower power consumption. Since it may not be possible for them to be charged for an extended period of time (months or years).

Hope you find the above information useful. Many thanks for reading.