Mobile communications have come a long way in terms of access technology. This means from the transmission of signals in the air going to your device or gadgets. Let’s take for example basic walkie-talkie two-way radio. These are used by young people, to communicate and have fun with their playmates. We you say “hello” message goes to the air and received by the other set. When the “hello” is sent over the air it is converted into analogue transmission. It’s fast and reliable to reach the other hand set. However, if you observe the voice quality is bad and garbled. Still you can understand the words, your sender has said. This is the same with first generation Mobile networks and handset. The main objective was to send the message to the other party immediately. But the quality and security of your transmission is not good.

Another challenge of the analogue system is capacity. This includes the efficient use of the frequency and bandwidth allocation. The Analogue system uses the FDMA (frequency division multiple access) technology to transmit the signals from point A to point B. This made them use intensively the bandwidth of the spectrum. The whole of Europe and Americas saw this problem as the mobile industry thrived and demand for a better system has been on everybody’s mind. These changes gave birth to the digital age of Mobile communications. In this campaign, the Americans went to modify their existing networks into D-AMPS (Digital AMPS) to save their current infrastructure.

In Europe, they were doing research for a new Mobile System. New set of protocols, different from their American counterparts. This would address the following:

1. A Network Architecture compliant to ETSI and 3GPP.
   
2. Better voice quality.
   
3. Introduce Air Interface encryption – protect the transmission of the call from “eves dropping” (intrusion).
   
4. Increase of Capacity and Efficient use of the Frequency Spectrum.
   
5. The introduction of value added services- such as Short Messaging Services (SMS).
   
6. The solution of using your mobile number in any global partner network. Roaming Service.
   

The late 1980’s to the early 1991, the new system was called GSM (Global System for Mobile Communications) was developed. It was called Groupe Spécial Mobile (French pronunciation). The Scandinavian part of Europe were the most active participants of the trials for development of GSM (second generation-2G). In the year 1992, the first working GSM network was launched in Europe. This new system fulfilled the needs as given above. This new system used TDMA (Time Division Multiple Access) technology. It is a game changer due to new features it gave to the subscribers. When this new system was introduced in the Philippines, most subscribers noticed the improvement of the voice quality. The caller ID, your caller’s name and number appears on your screen. These were value added services that the subscribers appreciated.

The most appreciated value-added service which the Filipinos have embraced is the Short Message System. The ability of the subscriber to send text messages to your contacts. This was made without any third party involved. The best part, is that it’s free (initially). This proved to be the selling point of GSM against the analogue system. Both can do calls, have mobility. But the security and value-added service of GSM was better than the existing network. In 1995 the Philippines, started to roll-out GSM system with Isla Com and Globe Telecom taking the lead. To illustrate this better, let’s view a system diagram below:

Note: Credit goes to Pinterest (GSM Architecture)

Let us define the important parts of the network:

1. SIM – Subscribers Identification Module Card
   
2. Mobile Equipment – A mobile phone or Gadget (Tablet, Laptop, etc.)
   
3. BTS – Base Transceiver Station
   
4. BSC – Base Station Controller
   
5. MSC – Mobile Switching Center
   
6. HLR – Home Location Register
   
7. VLR – Visitor Location Register
   
8. EIR – Equipment Identity Register
   
9. AuC – Authentication Register
   

This is the basic GSM System Architecture, as we progress to our next topic in the blog series. This Architecture will grow and give us Data capabilities. When GSM was in its early design stage, one of the objective is to have data capability. You know what was the first data rate of these networks? It was 9.6 kbps this was enough to send a fax message. GSM became the universal network from 1992 onwards. Dominating even the American market, adoption rate was so fast globally. The latest news for GSM is that it has matured to full growth in the last 26 years. However, the Data Capability of this technology is limited. This would be our next discussion on our Blog. The growth of Data Services from GSM to WCDMA and LTE. Thank you and see you soon on the next Blog.

Disclaimer: This Blog is the product of the authors 20 years’ experience in the Cellular Telecommunications in the Philippines. This does not have any relation or thoughts with my current, former and future employers. This includes my customers in all my years in Telecoms in the Philippines. All ideas are mine by way of experience. References are found in Wikipedia and corporate websites in the internet which are for public use and viewing. This includes presentations or Blog pages which are also acknowledge by the author.