GSM Cell Phones

GSM cell phones are some of the most high-tech phones on the market. For this reason, many people would be surprised to learn that they've actually been around for almost three decades. The format for GSM cell phones, originally developed by the Groupe Speciale Mobile in the early 1980s, was established as a way of ensuring a common cellular network across national borders.

Differences between GSM Cell Phones and CDMA Phones

The main difference between GSM cell phones and CDMA cell phones (the main competing standard) is how the base network handles phone traffic. Because the frequency range available for cellular communications is limited, it's necessary to figure out a way to pack a lot of calls into one small band of airwaves. GSM and CDMA take different approaches to this problem, which means that they are not compatible.

GSM solves the bandwidth problem by giving each user of the frequency channel specific time slots to communicate data. In other words, GSM calls are split up into tiny pieces that are transmitted in short bursts. Theoretically, only one call is using the frequency band at any specific moment in time, but the data bursts are so brief that a lot of calls can be transmitted simultaneously.

CDMA uses a type of technology called "Spread Spectrum" to pack multiple calls into one signal. Spread Spectrum technology uses digital modulation to spread and mix the data packets from each call into the stream, along with all the other calls. On the receiving end, this spread signal is decoded so only the desired call comes through.