What is the difference between GSM, UMTS and LTE?

GSM, UMTS and LTE are three mobile communications technologies that provide cellular connectivity to a large number of mobile networks across the globe. While GSM and UMTS started their journey primarily in Europe, they are now the leading mobile communications technologies worldwide alongside LTE.

GSM, UMTS and LTE are cellular technologies that enable second (2G), third (3G) and fourth (4G) generations of mobile networks. GSM uses FDMA & TDMA, UMTS uses WCDMA and LTE uses OFDMA & SC-FDMA for air interface. The bandwidth is 200 kHz in GSM, 5 MHz in UMTS and 1.4 to 20 MHz in LTE.

Which network generations do GSM, UMTS and LTE belong to?

GSM belongs to the second-generation (2G) of mobile networks, UMTS belongs to the third-generation (3G) of mobile networks, and LTE belongs to the fourth-generation (4G) of mobile networks. Multiple cellular technologies enable 2G and 3G, but LTE is the only technology that enables 4G.

GSM stands for Global System for Mobile Communications, and it is a second-generation (2G) technology that introduced circuit-switched voice calls, SMS (Short Message Service) and mobile data on our phones. Later, GSM networks introduced packet-switched mobile data through GPRS (General Packet Radio Service), often referred to as 2.5G. UMTS stands for Universal Mobile Telecommunication System, and it is a third-generation (3G) network technology that provided the 3G migration path to GSM networks and introduced us to high-speed data services like High-Speed Packet Access (HSPA). LTE stands for Long Term Evolution (of mobile networks), and it is a fourth-generation (4G) network technology that can enable peak data rates of up to 3 Gbps with LTE-Advanced Pro. LTE is the 4G migration path for UMTS and other 3G network technologies.

Are GSM, UMTS and LTE digital cellular technologies?

GSM, UMTS and LTE are digital cellular technologies that started their journey with the launch of GSM in the early 1990s which marked the beginning of the digital era in mobile communications. UMTS (Year 2000) is the evolutionary step for GSM, and LTE (Year 2009) is the evolutionary step for UMTS.

The first generation of mobile networks (1G) was based on analogue cellular technologies that used FDMA (Frequency Division Multiple Access). 1G networks started their journey in the early 1980s, and the key 1G technologies include AMPS (Advanced Mobile Phone System), TACS (Total Access Communications System), NMT (Nordic Mobile Telephone) and C-Netz ( Radio Telephone Network C).

The digital cellular systems were introduced in the early 1990s with the launch of second-generation (2G) GSM (Global System for Mobile Communications) and D-AMPS (Digital Advanced Mobile Phone System). Since then, the mobile network evolution has been digital, and radio access technologies have evolved continuously. UMTS, CDMA2000, LTE and NR technologies have led the way for digital cellular communications. I have written a detailed post on analogue and digital mobile networks, which has a lot more information on this specific topic.

Which one is better: GSM, UMTS or LTE?

GSM is a second-generation (2G) cellular technology standard and is, therefore, less capable of providing high-speed data as compared to UMTS, which is a third-generation (3G) technology and LTE, which is a fourth-generation (4G) cellular technology.

Since GSM, UMTS and LTE co-exist in mobile networks today, you may sometimes wonder which one is better. Let’s first compare GSM and UMTS before discussing LTE. GSM is a second-generation (2G) technology, and UMTS is a third-generation (3G) technology. UMTS provides the 3G migration path to GSM and is therefore superior to GSM.

When GSM networks were originally launched, they were circuit-switched and mainly offered voice and text message (SMS) services. GSM networks had circuit-switched data (CSD) to enable mobile data (internet), but it wasn’t very efficient or high-speed.

GPRS (General Packet Radio Service) was introduced in GSM networks a few years before the launch of 3G, and it could offer peak data rates of up to 171.2 kbps which later improved to 384 kbps with another enhancement, EDGE (Evolved Data for Global Evolution).

When UMTS allowed GSM networks to migrate to 3G, the focus changed from voice and text to mainly mobile data. With the latest enhancements in the form of High-Speed Packet Access (HSPA and HSPA+), UMTS networks can enable peak data rates of up to 42 Mbps. Compared to UMTS and GSM, LTE (Long Term Evolution) is a more advanced and recent technology that considerably enhances the average data rates of a mobile user.

LTE is superior to UMTS and GSM in two ways; first, it is the fourth generation technology capable of enabling peak downlink data rates of up to 3 Gbps with LTE Advanced Pro; second, it is a technology that applies to all key cellular networks in the world including GSM, UMTS, IS-95 and CDMA2000.

LTE is the most widely available cellular technology globally and can enable peak data rates of up to 3 Gbps with LTE-Advanced Pro. It provides 4G migration paths to all 3G technologies, including UMTS and CDMA2000. Therefore, LTE is superior to UMTS and CDMA2000 and offers much higher data rates than preceding cellular technologies.

I have written a dedicated post that compares LTE and HSPA+ to help you understand the differences because there has been some confusion between the two technologies.

How GSM, UMTS and LTE relate to CDMA cellular technologies

GSM and UMTS belong to the first track of cellular network evolution led by 3GPP, whereas CDMA technologies, IS-95 and CDMA2000, belong to the second track of cellular network evolution under the leadership of 3GPP2. LTE is the streamlining technology that offers a 4G migration path to both tracks.

GSM and CDMA can be seen as two technology tracks that led the evolution of 2G and 3G mobile networks. GSM and UMTS are part of the first track, whereas IS-95 and CDMA2000 represent the second track. LTE is a technology that streamlines the mobile network evolution as it provides the 4G migration path for both UMTS and CDMA2000.

In the first track, GSM uses a combination of FDMA and TDMA, whereas UMTS is based on Wideband Code Division Multiple Access. For clarity, even though the radio access for UMTS relies on a variant of CDMA, it has nothing to do with IS-95 or CDMA2000. As part of the second track, both IS-95 and CDMA2000 use a “narrowband” version of CDMA with a channel bandwidth of 1.25 MHz.

In comparison, UMTS can use channel bandwidths of 5, 10 and 20 MHz and is therefore referred to as the “Wideband” version of CDMA. I have written a dedicated post on the difference between the GSM track and the CDMA track, which you may check out for more details on this topic.

How is GSM related to other 2G cellular technologies?

Even though GSM is the most widely deployed second-generation (2G) cellular standard, two other 2G technologies, including D-AMPS and IS-95, have been key to the evolution of mobile networks. D-AMPS was similar to GSM and used a combination of FDMA and TDMA, whereas IS-95 was CDMA-based.

Both GSM and D-AMPS were introduced at the beginning of the 1990s and employed a combination of FDMA (Frequency Division Multiple Access) and TDMA (Time Division Multiple Access) for the radio access network. The radio access network is the air interface that enables wireless connectivity between the mobile network and the mobile phones.

When GSM was first introduced in Europe, the most dominant second-generation (2G) technology in the American region (USA) was D-AMPS, which was the digital version of AMPS (Advanced Mobile Phone System). Later, a CDMA-based technology, IS-95 (Interim Standard 1995), entered the market in the mid-1990s, which would later become the second most popular 2G technology after GSM.

D-AMPS networks have now been decommissioned and have been replaced by either GSM or IS-95. If you live in the US and wondering what IS-95 is, it is the technology behind cdmaOne. From an end-user perspective, 2G networks offer highly secure voice calling, text messaging (SMS – Short Message Service) and mobile internet services.

Today, GSM technology also plays a key role in mobile Internet of Things or mobile IoT, also referred to as Cellular IoT. I have written a dedicated post on Cellular IoT and if you are interested in the connectivity for home automation by any chance, feel free to check out that post.

In GSM and D-AMPS networks, the available frequency spectrum is first broken down into smaller frequency channels (FDMA) and then split further into multiple timeslots per channel (TDMA). GSM networks use multiple frequency bands in the 900 MHz, 1800 MHz, 850 MHz and 1900 MHz ranges which you can learn more about in our dedicated post on GSM frequencies.

D-AMPS networks utilise the 824 MHz to 894 MHz frequency band, which you can learn about in the dedicated post on AMPS and D-AMPS. Finally, the third 2G technology, IS-95, uses the 850 MHz and 1900 MHz bands, which you can learn about in our dedicated post on IS-95 frequency bands.

Enhancements to GSM: GPRS and EDGE

GPRS and EDGE are two network enhancements made to the GSM network for packet-switched mobile data services. While the GSM networks had High-Speed Circuit Switched Data (HSCSD) technology for mobile data, GPRS (General Packet Radio Service) was added to introduce a packet-switched approach to mobile data, which later replaced HSCSD.

The circuit-switching technique continued in GSM networks for voice and SMS services, but two new nodes, GGSN and SGSN, were added to the GSM core network to enable packet-switched mobile data. Later, another enhancement, EGPRS, was introduced under the umbrella technology EDGE (Enhanced Data for Global Evolution).

GPRS can offer peak downlink speeds of up to 171.2 kbps, and EGPRS (EDGE) can offer up to 384 kbps. I have written a dedicated post on the differences between GPRS, EGPRS and EDGE, which can provide further information on this topic.

How is UMTS related to 3G CDMA2000?

As discussed earlier, UMTS is a Wideband Code Division Multiple Access technology that provides a 3G migration path for the GSM networks as part of the first mobile network evolution track. The other 3G track is CDMA2000 (Code Division Multiple Access – Year 2000), which is primarily for cdmaOne networks.

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 focusing on UMTS and CDMA2000 respectively.

The UMTS technology is based on Wideband Code Division Multiple Access (WCDMA), which is different from the FDMA and TDMA combination that GSM uses. The UMTS mobile core network uses the same packet-switched network nodes, SGSN and GGSN that were introduced as part of the GPRS upgrade.

UMTS networks are tightly integrated with GSM networks to ensure inter-technology handovers for call and data sessions (IRAT – Inter Radio Access Technology). UMTS networks can enable theoretical peak speeds of up to 2 Mbps and real-life speeds of around 384 kbps.

You can check out my dedicated post on 3G UMTS networks with details about UMTS frequencies, channel bandwidth and more. CDMA2000, on the other hand, provides the 3G migration path for IS-95 (cdmaOne) and D-AMPS.

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. 

Enhancements to UMTS: HSPA and HSPA+

While UMTS was a big step forward, the high-speed data services in 3G UMTS networks were enabled by a combination of two 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. UMTS primarily employs a channel bandwidth of 5 MHz, which is considerably higher than the 200 kHz used by GSM.

Just for comparison with the CDMA networks, the equivalent of HSPA in CDMA2000 is EVolution Data Optimised – EVDO, which can offer peak downlink and uplink speeds of up to 14.7 Mbps and 5.4 Mbps respectively.

LTE – The fourth Generation (4G) cellular technology

LTE is the 4G migration path for UMTS (Universal Mobile Telecommunication System) 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 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 Pro add new capabilities to LTE by increasing the available capacity and achievable bit rates.

LTE employs flexible channel bandwidths of 1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz and 20 MHz. An enhancement, carrier aggregation, was introduced in LTE-Advanced networks to improve data rates considerably by allowing a user device, e.g. a mobile phone, to connect to multiple frequency channels (carriers) simultaneously. In summary, the three versions of LTE can offer the following downlink (download) speeds:

• 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 theoretically generate, but due to the nature of the radio signal, e.g. path loss and multiple users accessing the network simultaneously, the peak speeds are never achieved in real life. The average download speeds with LTE are considerably lower, which you can read about 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 to enable IP-based voice calls and SMS. VoLTE involves a new network entity called IP Multimedia Subsystem (IMS) that works alongside 4G core network EPC (Evolved Packet Core) to enable IP-based (Internet-based) voice calls and SMS just like other data services.

LTE networks also have a circuit-switched fallback CSFB, which allows the circuit-switched part of the mobile network (2G and 3G) to make voice calls in situations where the VoLTE capability is not available. LTE networks do not have a circuit-switched part, and therefore, CSFB essentially means that phone calls and SMS are facilitated by 2G or 3G mobile networks.

The air interface for LTE networks is based on Orthogonal Frequency Division Multiplexing – OFDM. LTE employs OFDMA – Orthogonal Frequency Division Multiple Access for the downlink radio access and SC-FDMA – Single Carrier Frequency Division Multiple Access for the uplink.

Compared to the radio access technologies in 2G and 3G networks, OFDM is more efficient in extracting higher ‘bits’ out of the available bandwidth. It supports a highly efficient digital modulation technique, Quadrature Amplitude Modulation – QAM. A higher QAM configuration ensures higher bits per symbol, which means higher data rates.

LTE Advanced and LTE-Advanced Pro networks use higher QAM configurations. LTE networks also employ an advanced antenna technology, MIMO (Multiple Input Multiple Output), which uses multiple transmitter and receiver antennas. MIMO is more efficient compared to the single antenna (SISO)-based technologies that GSM networks use.

How 5G NR relates to GSM, UMTS and LTE

5G, or the fifth generation of mobile networks, is enabled by the New Radio (NR) technology. Just like LTE streamlined the 4G migration by providing a single 4G upgrade path to all 3G technologies, including UMTS and CDMA2000, NR is the only technology that enables 5G migration.

It means that both UMTS and CDMA2000 networks will continue to use LTE for 4G and NR for 5G until the 3G technologies eventually get phased out. In the US, Verizon has already announced the retirement of their 3G CDMA networks (CDMA2000) by the end of 2022, which you can read about on this page on Verizon’s website.

5G NR networks are expected to co-exist and evolve alongside 4G LTE for a long time, and therefore, LTE and NR require tight integration. As a result, there are currently at least two popular 5G network deployment modes: 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 through dual connectivity. The standalone version is the full 5G network, which uses its own 5G cloud-native core network. If you are a student or professional and want more details, you can check out this dedicated post on the 5G New Radio technology and how it works.

Conclusion

The difference between GSM, UMTS and LTE is that they represent three different generations of mobile networks between the 1990s and 2009.GSM, UMTS and LTE are 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.

GSM, UMTS and LTE currently co-exist alongside the new 5G NR technology. The LTE technology is expected to evolve alongside NR to enable many existing and futuristic use cases for customers.