How Does Your Mobile Communicate? The Generation Time Warp!

Estimated difficulty: 💜💜💜🤍🤍

In light of recent worries around 5G and its effects on the population (in particular the theory of it causing COVID-19), I thought I would try to demystify the cellular network generations and provide an understanding of how they have developed; in particular, focusing on the security and networking side of things. (Just to clarify the G for each cellular network stands for generations, so 5G means the fifth generation.) Several new features have been introduced to mobile networks across the decades, in the hopes of understanding the past, I hope to clarify the vision of the future!

Networking Fundamentals

To explain the different generations of the cellular systems, it is best to first explain how communication between two mobile phones works. There is a lot of detail that you can go into here so this will be a high-level description; if you would like a more in-depth post please feel free to comment or ping me a message. For a device to communicate with another, they have a built-in antenna. This antenna broadcasts electromagnetic radio-frequency waves, which are broadcast and captured by the nearest mobile-phone mast otherwise known as a Base Transceiver Station (BTS). The BTS routes the traffic through the Base Station Sub-system (BSS) and the cellular network to contact the BTS nearest the person you are contacting. Wires are usually used to connect the BSS to the Mobile Switching Centre (MSC), where authentication and packet data sent from the mobile is used to direct the traffic. 5G BTS’ are hard to connect with cables, meaning that they also use waves to communicate with each other. If the device is in a foreign location, databases of the user’s whereabouts show the area in which the phone is connected. The Home Locator Registry (HLR) and Visitor Location Registry (VLR) provide information of the contactee’s whereabouts, thus allowing the nearest BTS to be found and the signal to be transmitted.

Since mobile devices make use of specific frequencies to communicate, the masts are spaced out over a geographical area and divided into cells. Specific frequencies are used for different things and in mobile technology, radio and microwaves are used to communicate. Mobile-phone mast antennas are allocated frequency slots, the antennas frequency on the mast will not interfere, as long as they are facing different directions or not overlapping. A user is allocated their own frequencies to communicate on so that the masts know which device is sending and receiving data, this method is called multiple access techniques. Frequencies are extremely expensive, Telecomms companies paid billions for available waves! These waves are not expandable and therefore you have to work with what you got.

It is important for providers to cram as many people into one band as possible which has been shown over over the generations, but this can still be maxed out if there are too many people to one cell. Just think back to all those times you try to find your friend in a festival or call someone on NYE and had no signal… That would be because everyone is trying to use these waves at once!

Early Generation Comparison

We have come a long way from 1G to 4G and not to mention the slowly trickling in 5G. From each generation of cellular network, new features and improvements have been made. Mobile devices have evolved to accommodate the new functionality that the networks provide. There is a stark difference between 1G, making use of analogue signals, and 5G, making use of digital signals to transmit data to the transceivers. For starters, the analogue signal had high interference and the data was not able to be obscured, causing a large security risk. Since then the digital signals used in the later generations incorporated encryption. These encryption algorithms varied in strength! It is safe to say each generation brought something new and I have summarised the main points in the below table:

1Gc.1980s2.4Kbps30KHzPSTNFDMAIMTS, AMPSThe introduction of the first telephone network. Used analogue signals. suffered from interference and transmit data un-encrypted.
2Gc.1990s14.4 – 64Kbps1.8GHzPSTNFDMA, TDMAGSMDigital signals were used, improving the security and reliability of data being transmitted. Encryption, the Short Message Service (SMS) and the SIM card was introduced. GSM allowed more users to connect in a smaller geographical space. are used to split the frequencies when a mobile connects to a base station.
2.5Gc.1990s14.4 – 64Kbps1.8GHzPSTNCDMAGPRSStill making use of the digital signals, data/Internet was included with the introduction of this generation. General Packet Radio Service (GPRS) was introduced to allow IP-based packets over a switched network.
3Gc.2000s2Mbps1.6 – 2GHzPacket NetworkCDMAWCDMA, SGSN, GGSN, RNC3G focused on improving the speeds of the Internet. New technologies and protocols were introduced to allow users to connect to the mobile base stations such as WCDMA, this means each user gets a unique code.
4Gc.2000s – c.2010s1Gbps2 -8 GHzInternetCDMALTE, EPCFurther increased the speeds data was able to be transmitted.
5Gc.2010s1Gbps and higher!3 -30 GHzInternetOFDMMIMOMore cell base transceiver stations, higher frequencies used to allow improved data transmission speeds. Beamforming to direct transmissions in a certain direction.
Some information was sourced from:

I’m sure in that table there are plenty of acronyms that might leave you scratching your head, so here is a glossary to further explain what all these letters actually mean!

PSTNPublic Switched Telephone Network – Makes use of circuit switching.
FDMAFrequency Division Multiple Access – Divides frequency bands into multiple channels to allow a phone to communicate with the receiver.
IMTSImproved Mobile Telephone System – c.1960s was a radio system that linked to the PSTN. MAde use of 1 call for each frequency across 100km.
AMPSAdvanced Mobile Phone System – Also known as the Total Access Communications System (TACS). Divided the geographical region into cells to allow 10-15 calls on each frequency in the same area.
TDMATime Division Multiple Access – Allows several users to share the same frequency channel by dividing the signal into different time slots.
GSMGlobal System for Mobile communications – Is a cell-based system, with frequency reuse across cells and has mobility handover. GSM made use of TDMA.
CDMACode Division Multiple Access – Was a radio system technology built into phones that assigned a unique code to a call and allowed them to be made simultaneously on one channel. The spread spectrum technique is used in CDMA.
GPRSGeneral Packet Radio Service – Made to enhance GSM to allow connectionless packet delivery.
WCDMAWideband Code Division Multiple Access – Each user is separated by an assigned unique code instead of timeslots and frequencies.
SGSNServing GPRS Support Node – This is an IP gateway in which the data packet is passed to.
GGSNGateway GPRS Support Node – The packet is routed to the Internet through this gateway.
RNCRadio Network Controller – Carries out radio resource management, mobility management and encrypts data before it is sent to and from the mobile.
LTELong Term Evolution – Developed to increase the speed of the 4G network.
EPCEvolved Packet Core – This combines different technologies, such as the Serving Gateway (SGW), Packet Data Network Gateway (PGW), Mobility Management Entity (MME) and Policy and Charging Rules Function (PSCRF).
OFDMOrthogonal Frequency Division Multiplexing – Transmits large amounts of data over a radio wave by splitting the radio signal into multiple sub-signals that can be transmitted simultaneously.
MIMOMultiple Input Multiple Output (MIMO) technology introduced in the radios of the new devices to allow simultaneous connections to be made to the transceivers.


Honestly, learning about this technology has me in awe of how far wireless networks and devices have come. I am excited about the future! With the higher frequencies being used from the electromagnetic spectrum, more people and devices can make use of the cellular network with improved speeds. With issues such as higher interference, for example, 5G can be blocked by rain, small cell technology has been introduced meaning there are more base stations. Increased capacity, latency and throughput, means improved performance from smart cars, streaming and anything else to do with the Internet of Things (IoT).

Increasingly concentrated frequencies are now being used in 5G, however, we are surrounded by these waves constantly and they have so far shown to be harmless to people (does it seem like I have been triggered by the news yet?). It could be dangerous to stand right next to an antenna, and we must all keep safe, but we shouldn’t let irrational fear fuel us. Guidelines from the WHO have been put in place to further protect us from these waves, however, there are negligible adverse health effects. Any real fear we have should be from the security implications of the technology. 😉


I have talked a lot about the networking of the generations, however, to round off this post I thought I would highlight the risks to using 5G from a technological perspective:

  • If there is a national dependency on the 5G service, downtime could cause serious disruptions.
  • Administrative access to the network could be abused.
  • Equipment used could become vulnerable and be exploited by an attacker.
  • Equipment may become faulty or unreliable bringing the service down.
  • Vendors providing the equipment could potentially compromise their technology.

For a full security evaluation, a report has been produced by the NCSC.

There is no doubt that within these networks there are plenty of different hardware devices. There are multiple points our data can cross to get to where it is going, and it is just as important that these devices are secure as they can be. Therefore, I couldn’t finish this post without mentioning the situation of Huawei and its use in the UK’s new 5G network. It was reported that their technologies were to be banned from the core of the new 5G network, as there were security concerns around their technology. Nothing is yet determined with this, however, my only food for thought is to be as protected as possible, we must trust the providers we are using and personally, it is down to us to try not to send sensitive data in our comms! 🙂

Thanks for reading! If you have any feedback don’t hesitate to comment!

Sarah <3

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