What is the difference between GSM, UMTS and LTE?

We live in an era where life without our mobile phones seems almost impossible even to imagine. During the lockdown period, our smartphones provided us with a phone to communicate with our loved ones and a backup for our home broadband. According to the Ericsson Mobility report from June 2021, which you can download by following this link on Ericsson’s website, today, we already have 8 billion worldwide mobile subscriptions. The report also suggests that towards the end of 2020, there were 6 billion smartphones. In the early 1980s, when mobile phones made their entry into our lives, they were more of a luxury for those among us who needed to make important phone calls while being on the move. Today we have more mobile phone subscriptions than the human population on this planet. Even though mobile phones are so personal and close to us, there is still a lot about them that is unclear to many of us. This post will dive into key networks technologies, GSM, UMTS, and LTE, to clarify what they mean and how they differ.

Are smartphones analogue or digital?

The word digital is very common nowadays and taken for granted sometimes, but did you know that our mobile phones were not always digital? The first generation of mobile networks was based on analogue technologies, and the mobile phone industry only went digital when the second generation was introduced around 1991-1992. The first generation networks, 1G, employed FDMA-based radio access technologies to connect our mobile phones to the mobile network. FDMA stands for Frequency Division Multiple Access, and it uses individual frequency channels for individual calls. The digital mobile networks are a lot more secure than the analogue systems, and the GSM, UMTS and LTE technologies that we will cover in this post are all digital technologies. You can check out our dedicated post on the difference between digital and analogue mobile networks.

what do GSM, UMTS and LTE mean?

GSM, UMTS and LTE are digital mobile communications technologies that enable mobile network coverage. GSM stands for Global System for Mobile Communications. UMTS stands for Universal Mobile Telecommunication System, and LTE stands for Long Term Evolution. GSM is a second-generation technology (2G), UMTS is a third-generation technology (3G), and LTE is a fourth-generation technology (4G).

If you are only interested in the GSM, UMTS and LTE technologies, then keep reading. On the other hand, if you are looking for an overview of all network generations and relevant technologies, you will find the new edition of Mobile Communications Made Easy more valuable.

What Is 2G – Second-Generation Mobile Technology?

2G or second-generation mobile networks were introduced in the early 1990s and the two key 2G technologies at the time were GSM and D-AMPS. Both GSM and D-AMPS employed a combination of FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) technologies for their air interface. The air interface is what creates the wireless connectivity and is enabled by the radio part of the mobile network which you can learn more about in our dedicated post on radio networks.

GSM, D-AMPS and IS-95

In GSM, the available frequency spectrum is first broken down into smaller frequency channels and then split further based on time slots. The original frequency band for GSM networks was from 890 MHz to 915 MHz for the uplink and 935 MHz to 960 MHz for the downlink. This frequency band is known as the Primary GSM band or P-GSM. The primary GSM band was later extended to add 10 MHz to both the uplink and the downlink. D-AMPS which stands for Digital Advanced Mobile Phone System is the digital version of first-generation mobile networks AMPS – Advanced Mobile Phone System. D-AMPS utilises the same frequency band for radio communication as the one originally employed by the AMPS network which is from 824 MHz to 894MHz. We have a dedicated post on the relationship between D-AMPS and AMPS if you want to learn more.

In the mid-1990s another key 2G technology IS-95 was introduced which was based on the CDMA technology. During the same period, a third technology called Interim Standard 1995 (IS-95) was introduced that chose CDMA (Code Division Multiple Access) for the air interface. IS-95 is commercially known as cdmaOne. You can learn more about CDMA mobile networks in our dedicated post on IS-95 and CDMA2000.

GPRS and EDGE

GPRS and EDGE are enhancements to the 2G GSM networks that enabled the packet-based mobile data services. GPRS stands for General Packet Radio Service and it was introduced in the GSM networks to make the data services more efficient through packet-switching. Circuit-switching continued to exist in GSM networks for voice and SMS, but for the data part, two new network nodes GGSN and SGSN were added. GPRS can offer peak downlink speeds of up to 171.2 kbps. Later, there was another enhancement called EDGE (Enhanced Data for Global Evolution) that increased the peak downlink speeds to 384 kbps. Have a look at our post GPRS vs EDGE to learn more about these technologies and to find out why GPRS and EDGE are referred to as 2.5G and 2.75G.

What Is 3G – Third-Generation Mobile Technology?

3G or third-generation mobile networks were introduced through two key technology tracks, one for the 2G GSM networks and the other for 2G IS-95 and D-AMPS networks. The first track was Universal Mobile Telecommunication Systems (UMTS) which was based on Wideband Code Division Multiple Access – WCDMA. The other track was CDMA2000 (Code Division Multiple Access – Year 2000) which was primarily for cdmaOne networks to migrate to 3G. For these two tracks, the standards organisation 3GPP (Third Generation Partnership Project) led the way in line with IMT2000 (International Mobile Telecommunication specifications for the year 2000) which resulted in two projects 3GPP and 3GPP2 to focus on UMTS and CDMA2000 respectively.

UMTS

UMTS was the 3G migration path for GSM networks. The air interface for UMTS is based on Wideband Code Division Multiple Access (WCDMA) which is different from FDMA and TDMA that GSM employed. 3G UMTS migration required major upgrades to the radio network as new base stations were needed. The UMTS mobile core network used the same packet-switched network nodes, SGSN and GGSN that were introduced as part of the GPRS upgrade. The customers required new mobile phones in order to be able to access the new UMTS technology. Since UMTS networks were designed to co-exist with the GSM networks, they were well-integrated to ensure that inter-technology handovers (IRAT – Inter Radio Access Technology) could occur seamlessly. UMTS networks can enable theoretical peak speeds of up to 2 Mbps and real-life speeds of around 384 kbps. These speeds were further improved by later enhancements High-Speed Downlink Packet Access (HSDPA) and High-Speed Uplink Packet Access (HSUPA). HSDPA and HSUPA are collectively called HSPA (High-Speed Packet Access) which can enable peak downlink and uplink speeds of up to 14.4 Mbps and 5.76 Mbps, respectively. HSPA was followed by HSPA+ or Evolved High-speed Packet Access which improves peak speeds to 42 Mbps in the downlink and 11.5 Mbps in the uplink. You can check out our dedicated post on 3G UMTS networks for a detailed view including UMTS frequencies, channel bandwidth and more. We also have a post on HSPA which you can find here.

High-level network diagram for GSM (2G) and UMTS (3G)

CDMA2000

The 3G migration for the other 2G technologies IS-95 (cdmaOne) and D-AMPS followed the CDMA2000 track. CDMA2000, also known as CDMA2000 1xRTT or IS-2000 is a successor of the earlier standard IS-95 (cdmaOne) and offers 3G mobile services as specified in IMT2000 (International Mobile Telecommunication specifications for the year 2000). CDMA2000 is backwards compatible with its predecessor IS-95, which makes the upgrade from IS-95 to CDMA2000 easy and seamless. It uses the same carrier bandwidth of 1.25 MHZ and is both circuit-switched as well as packet-switched. Just like HSPA was introduced to improve the data speeds in the UMTS networks, a technology called EVDO (Evolved Data Optimized) was introduced in CDMA2000 to offer higher data speeds. EVDO can offer peak downlink and uplink speeds of up to 14.7 Mbps and 5.4 Mbps respectively.

What is 4G – fourth-generation mobile technology?

The fourth generation of mobile networks – 4G was enabled by a new technology called LTE which stands for Long Term Evolution (of mobile networks). LTE is the 4G migration path for both Universal Mobile Telecommunication System (UMTS) and CDMA2000. While another technology WiMax (Worldwide Interoperability for Microwave Access) is capable of meeting the requirements of 4G services, LTE has been the primary technology for 4G deployments worldwide.

LTE

LTE was originally introduced in Release 8 of 3GPP in 2009 and since then it has seen multiple enhancements including LTE-Advanced and LTE-Advanced Pro. LTE-Advanced and LTE-Advanced add new capabilities to LTE to increase the available capacity and achievable bit rates. One such capability is carrier aggregation where a single user device e.g. a mobile phone can get connected to multiple frequency channels (carriers) to get higher data speed. You can learn more about the differences between LTE, LTE-Advanced and LTE-Advanced Pro in our dedicated post on the topic. From a download speed viewpoint, the following peak speeds are achievable with LTE.

  • LTE – up to 300 Mbps in the downlink
  • LTE Advanced – up to 1Gbps in the downlink
  • LTE Advanced pro – up to 3 Gbps in the downlink

These are the peak data speeds that the network can generate but due to the nature of the radio signal e.g. path loss etc. and due to multiple users accessing the network simultaneously, the peak speeds are never achieved on a single device. The average download speeds with LTE are considerably lower but you can read all about that in our dedicated post on average LTE and LTE-Advanced speeds. In addition to high-speed mobile data, LTE networks also have a technology called VoLTE – Voice over LTE that makes use of the packet-switched part of the mobile network for voice calls and SMS. We have a detailed post on VoLTE, but generally speaking, it involves a new network entity called IP Multimedia Subsystem (IMS) that works alongside 4G core network EPC (Evolved Packet Core) to enable voice calls and SMS just like other data services. LTE networks also have a circuit-switched fallback CSFB which allows circuit-switched part of the mobile network to make phone calls in areas where VoLTE is not available. CSFB basically means that the phone calls and SMS are facilitated by 2G or 3G mobile networks because they are the ones with the circuit-switched capability. We have a post on circuit-switched and packet-switched if you are not sure about the difference between the two.

The air interface of LTE networks is based on Orthogonal Frequency Division Multiplexing – OFDM. It employs OFDMA – Orthogonal Frequency Division Multiple Access in the downlink radio access and SC-FDMA – Single Carrier Frequency Division Multiple Access in the uplink. Compared to the earlier access technologies, OFDM is much more efficient in extracting more ‘bits’ out of the available capacity by making better use of the available bandwidth. It supports a highly efficient modulation technique Quadrature Amplitude Modulation – QAM. As we go from LTE to LTE-Advanced and from LTE-Advanced to LTE-Advanced Pro, the QAM configuration gets higher which leads to higher data rates. It also employs better antenna technology through spatial multiplexing (Multiple Input Multiple Output – MIMO). You can learn more about OFDMA and why LTE networks use it in our dedicated post on the topic.

High-level network diagram for UMTS (3G) and LTE (4G)

You may also check out our Mobile Networks Made Easy if you need some help with the network entities shown in the diagram above.

What about 5G?

5G or fifth generation of mobile networks are enabled by a technology called NR (New Radio). NR is to 5G what LTE is to 4G. Just like LTE streamlined the 4G migration by providing a single 4G technology to both CDMA2000 and UMTS, NR is the only technology that enables 5G. It means that both UMTS and CDMA2000 networks will continue to use LTE for 4G and NR for 5G until the 3G technologies are no longer needed. In the US, Verizon has already announced the retirement of their 3G CDMA networks (CDMA2000) by the end of 2022 which you can read all about on this page on Verizon’s website. 5G NR networks exist in two forms; non-stand-alone 5G (NSA) and stand-alone 5G (SA). The non-stand-alone 5G network makes use of the existing 4G LTE core network (EPC) to deliver 5G speeds. The standalone version is the full 5G network which uses its own 5G cloud-native core network. If you want to learn about the basics of 5G and what it means for 4G and your WiFi, check out this post on 5G meaning. We also have a separate post on 5G stand-alone vs non-stand-alone if you are interested.

Now that we have covered the basics of GSM, UMTS, LTE and other inter-related 2G, 3G and 4G technologies, let’s dive into some comparisons to look at how some of these technologies relate to each other.

GSM vs UMTS: Is GSM better than UMTS?

GSM is a second-generation technology whereas UMTS is a third-generation technology. UMTS is superior to GSM because it provides the 3G migration path to the GSM networks. Both GSM and UMTS can offer voice, text and data services. When GSM networks were originally launched they mainly only offered voice and short-message-service – SMS. Even though they had circuit-switched data capability, the proper mobile data service was added as part of GPRS – General Packet Radio Service. GPRS and a later enhancement EDGE (Enhanced Data for Global Evolution) were part of 2G GSM network evolution. 3G UMTS offered peak downlink data rates of up to 2 Mbps which moved up to 42 Mbps with the HSPA and HSPA+ enhancements (High-Speed Packet Access).

Is UMTS linked to GSM or CDMA?

UMTS – Universal Mobile Telecommunication System is a 3G migration path for 2G GSM networks. Even though UMTS is based on the access technology WCDMA (Wideband Code Division Multiple Access), it has nothing to do with the other CDMA-based networks IS-95 and CDMA2000. UMTS and CDMA2000 are two different technologies that enable the third generation of mobile networks. GSM and UMTS are the 2G and 3G technologies for one track whereas IS-95 and CDMA2000 are the 2G and 3G technologies for the other track. We have a great post on UMTS which you can read by clicking here.

Is UMTS the same as LTE?

LTE or Long Term Evolution is a 4G – fourth-generation cellular technology that provides a 4G migration path to 3G UMTS and CDMA2000. LTE is superior to UMTS and CDMA2000 because it offers much higher data rates as compared to earlier technologies. The HSPA+ technology (Evolved High-Speed Packet Acces) which is part of the UMTS networks has been incorrectly linked to 4G in the past. However, there is no link between UMTS/HSPA+ and LTE. We have a detailed post on HSPA+ vs LTE if you are interested.

LTE vs CDMA vs GSM

GSM and CDMA can be seen as two technology tracks that still exist for 2G and 3G cellular technologies. 2G GSM and 3G UMTS form the first track whereas 2G IS-95 and 3G CDMA2000 form the second track. LTE is a technology that streamlines the network evolution as it is the 4G migration technology for both UMTS and CDMA2000. We have a comprehensive post on the difference between GSM and CDMA for more information.

Conclusion

GSM, UMTS and LTE represent 2G, 3G and 4G mobile network technologies respectively. GSM stands for Global System for Mobile Communications, UMTS stands for Universal Mobile Telecommunications System, and LTE stands for Long Term Evolution (of Mobile Networks). GSM uses TDMA and FDMA for its air interface, UMTS uses WCDMA, and LTE uses a combination of OFDMA and SC-FDMA.

Here are some helpful downloads

Thank you for reading this post, I hope it helped you in developing a better understanding of cellular networks. Sometimes, we need some extra support especially when preparing for a new job, or studying a new topic, or maybe just buying a new phone. Whatever you are trying to do, here are some downloads that can help you:

Students & fresh graduates: If you are just starting, the complexity of the cellular industry can be a bit overwhelming. But don’t worry, I have created this FREE ebook so you can familiarise yourself with the basics like 3G, 4G etc. As a next step, check out the latest edition of the same ebook with more details on 4G & 5G networks with diagrams. You can then read Mobile Networks Made Easy which explains the network nodes e.g. BTS, MSC, GGSN etc.

Professionals: If you are an experienced professional but new to mobile communications, it may seem hard to compete with someone who has a decade of experience in the cellular industry. But not everyone who works in this industry is always up to date on the bigger picture and the challenges considering how quickly the industry evolves. The bigger picture comes from experience which is why I’ve carefully put together a few slides to get you started in no time. So if work in sales, marketing, product, project or any other area of business where you need a high-level view, Introduction to Mobile Communications can give you a quick start. Also, here are some templates to help you prepare your own slides on product overview and product roadmap.

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