Circuit switched networks physically connect two endpoints using a communication channel through the network. This utilises a fixed bandwidth for the session whilst the two endpoints remain connected. Packet switched networks offer the ability to split the communication channel into small packets to be sent across the network using multiple routes offering redundancy and increased performance. This utilises dynamic bandwidth management which can be optimised for each connected party and allows for many more services and connections to be active at the same time using the same bandwidth.
In the cellular network GSM (2G) and UMTS (3G) use circuit switching for voice, circuit switched dialup (CSD) and short messaging service (SMS) traffic and use packet switching for GPRS data traffic. In LTE (4G) the entire network uses packet switching and has no capability for circuit switched network support. As a result, the voice and SMS services must be moved over to a packet switched network when using the LTE (4G) network. In addition to this, CSD is no longer supported and GPRS data must be used instead.
Please see Circuit Switched Dialup (CSD) Migration to LTE Application Note' here.
Voice Overview Many applications in use today utilise voice as part of the service offering. This may be to connect two parties together to communicate such as in an elevator emergency failure system, to implement an automated payment service using a dial keypad or report a fault with a system using normal spoken language. Whatever the reason for using the voice service in a cellular system, there are some differences with the LTE network which are described in more detail below.
On legacy devices supporting GSM (2G) and UMTS (3G) services, the voice and SMS components of the system use circuit switching as the transmission channel. For GSM the whole system was built on an analogue infrastructure and digital data was added to the system later with the advance of GPRS packet data. The UMTS system is based on the GSM standard and therefore also supports both digital and analogue components. The UMTS framework allows much higher data rates over GSM but is still based on a similar infrastructure.
LTE on the other hand is entirely digital and has no analogue components at all. Therefore, new methods are used to take advantage of the new features offered by the LTE network as analogue voice calling is no longer possible and the packet switched network must be adopted.
VoLTE (Voice over LTE) Overview The LTE network supports voice and many other additional services in the same way as GSM and UMTS, however, as there is no analogue component the voice must be encoded and sent digitally across the network using packets. The 3GPP body have specified the voice service on LTE which is highly optimised and takes advantage of the additional bandwidth and low latency of the LTE network. This service is called Voice over LTE (VoLTE) and uses the digital packet switched network in a much more efficient way than traditional services. This means that VoLTE can support up to 3 times more voice capacity than previous UMTS networks and up to 6 times more capacity than older GSM networks.
The VoLTE service is provided on LTE over the IP Multimedia System (IMS) network service which is a standardized framework for delivering multimedia services over TCP/IP. It has been developed to allow all content rich media from wireless and wireline applications and allows for advanced services to be provided over the existing infrastructure without the need for individual control functions for each service.
The network provider must support IMS to be able to offer VoLTE as a service to its customers. The IMS framework must be integrated within the network's core architecture and is fundamental to the operation of the network.
Network Usage with Circuit Switch Fall Back (CSFB) With existing GSM (2G) and UMTS (3G) networks, the core functions are built into the application and can be supported with any hardware platform that supports voice and any SIM card that supports voice. This allows for a very simple implementation and calls can be established without any special configuration to the end equipment.
With newer modems that support LTE (4G) in addition to GSM (2G) and UMTS (3G) the firmware in the modem performs a subtle trick to continue having seamless voice support. When connected to the network for transmitting digital packet data, the unit connects to and uses the LTE network. When attempting to dial a voice number the unit automatically switches to UMTS (3G) or GSM (2G) to establish the call. Once the call is finished it reverts to the LTE network. This technology is called circuit switch fall back and is a short-term solution to allow all network providers to offer voice services on the LTE network whilst they implement their own full IMS solution.
This process is fine whilst there are UMTS (3G) and GSM (2G) networks available to use but the analogue networks are being gradually sunset to be replaced entirely with the LTE network.
With the LTE (4G) network it is necessary to configure the device to allow calls to be made using the LTE only network over the IMS service.
SMS Overview The short messaging service (SMS) can be used to send and receive small text messages which can be used in a variety of ways for applications that use the cellular network. The messaging service can be used to configure settings in remote equipment as well as reporting on the current configuration. In addition, the messaging service can inform users directly of a triggered alarm state or indicate when a certain criterion has been met. As with voice, the existing GSM (2G) and UMTS (3G) core functions are built into the system and can be supported with any hardware platform that supports the SMS messaging service and any SIM card that has SMS functio
Europe Stories
11/12/2025
Dalet, a leading provider of cloud-native, end-to-end media workflow solutions, ...
03/12/2025
S an Nollaig
Celebrate 2025's top Irish sporting stars with RT Sport Awards live from RT Studios on RT One and RT Player
RT pays tribute to Ror...
02/12/2025
eds3_5_jq(document).ready(function($) { $(#eds_sliderM519).chameleonSlider_2_1({...
02/12/2025
--
The International Electrotechnical Commission (IEC), the International Organization for Standardization (ISO), and the International Telecommunication Unio...
02/12/2025
Harmonic's cOS Platform Will Redefine Subscribers' Quality of Experience, Lowering Churn SAN JOSE, Calif. - Dec. 2, 2025 - Harmonic (NASDAQ: HLIT) today...
02/12/2025
S an Nollaig
Hollywood blockbusters The Banshees of Inisherin, Barbie and Oppenheimer make their Irish TV debut
Tune into the classics such as Love Actual...
02/12/2025
Showcasing fresh Irish storytelling and emerging talent Storyland 2025 signals a fantastic time for Irish drama
RT and F s ireann/Screen Ireland are proud to...
01/12/2025
MANCHESTER, UK - November 2025 - Announced two days before the 30th anniversary of Oasis' debut album, Definitely Maybe, the Oasis Live '25 tour marks t...
01/12/2025
01 Dec 2025
Kyivstar and Ukrainian Ministry of Digital Transformation Select Go...
01/12/2025
The prequel to the global hit Sky Original mob crime saga, Gomorrah' is a s...
01/12/2025
Featuring Florence Welch, Red Hot Chilli Peppers' Flea, designer Bella Freud...
01/12/2025
Fox Corporation Chief Financial Officer Steve Tomsic to Participate in Upcoming ...
01/12/2025
Arvato Systems' Virtual Private Cloud (VPC) Receives BSI C5 Certification (T...
01/12/2025
Summary This short video gives you an summary of the changes in under two minutes.
--...
01/12/2025
As the festive season approaches, RT Supporting the Arts is proud to showcase a...
01/12/2025
Festive specials of Christmas in Kilmainham presented by Marty Whelan, High Road Low Road, Callan Kicks the Year and Keys to My Life
Ring in the New Year with ...
01/12/2025
Architect and television presenter Hugh Wallace, best known to RT audiences as a long-serving judge on Home of the Year, has died at the age of 68.
In a state...
28/11/2025
It's easy to ignore those little red update available badges. But when it ...
28/11/2025
Friday 28 November 2025
Sky Sports x Slawn drop limited-edition football jersey...
28/11/2025
Rohde & Schwarz shows resilience in a challenging environment, revenue exceeds t...
28/11/2025
Unwrapped: The Toy Show Appeal - airing this Sunday on RT One and RT Player- s...
27/11/2025
27 Nov 2025
GSMA brings M360 Eurasia 2026 to Samarkand in partnership with VEON...
27/11/2025
Tahar Rahim and Izuka Hoyle star in the gripping six-part Sky Original from Acad...
27/11/2025
Thursday 27 November 2025
Sky Arts Reveals the Nation's Greatest Basslines - and Queen Reign Supreme
The UK's most iconic basslines have been revealed...
27/11/2025
Rating reflects rating progress across areas including policies, diversity & inclusion, health & safety and Net Zero leadership
Winchester, UK, 27 November 202...
27/11/2025
What are the industry standards for Retail Media? Kathryn explains that certification is based on the IAB Europe Retail Media Measurement Standards and the IAB ...
27/11/2025
World champion boxer and Irish sporting icon Katie Taylor will be in studio this...
27/11/2025
Roblox, one of the world's most popular online gaming platforms for primary ...
26/11/2025
Book podcasts are booming. On Spotify, you'll find everything from celebrity book clubs to deep dives with bestselling authors. And in markets where audiobo...
26/11/2025
YouView Achieves Greenly Gold Certification for SustainabilityNov 26, 2025
YouView is proud to announce a Gold Certification award from Greenly for our perform...
25/11/2025
Tracy Bonareri Onchoke, an investigative journalist from Kenya is the winner of the Thomson Foundation's Young Journalist Award 2025.
The 26-year-old-sele...
25/11/2025
The best playlists, podcasts, and audiobooks bring a little extra magic to your daily routine. With new features and offerings, Spotify Premium delivers even mo...
25/11/2025
Comprehensive new research confirms what we already knew: Australian music fans love the quality, quantity, and access they have to new and local music on strea...
25/11/2025
Applicable Products
Objectives The purpose of this application note is to give a brief background on 5G (NR) wireless communication an explain the reason a SN...
25/11/2025
25. November 2025 Cecilia Pierron
Last week, we took part in OnDAM 2025, an educational conference fully dedicated to DAM, hosted by Activo Consulting. The ...
25/11/2025
25 Nov 2025
VEON's QazCode and MeetKai Sign Agreement to Power National LLM...
25/11/2025
UKTV has acquired a high-profile slate of US dramas from Paramount Global Conten...
25/11/2025
A symphony of genius, rivalry and vengeance, boldly reimagined from Peter Shaffe...
25/11/2025
Article courtesy of Cinematography World
Read the article
FilmLight has finalised the prestigious 2025 FilmLight Colour Awards jury and welcomed award-winning...
25/11/2025
Article courtesy of Prensario
Read the article
La serie fue dirigida por Juli n de Tavira, Rodrigo Santos, y David Leche Ruiz, con direcci n de fotograf a a...
25/11/2025
Article courtesy of The Hollywood Reporter
Read the article
The awards, celebr...
25/11/2025
Article courtesy of Televisual
Read the article
Already live in Los Angeles and rolling out in New York and London, Nara gives producers, colourists, conform ...
25/11/2025
Article courtesy of Digital Media World
Read the article
ARTONE post-house in Tokyo is the first facility in Japan to integrate Baselight M, choosing its prec...
25/11/2025
Article courtesy of The Hollywood Reporter
Read the article
Once hidden in post-production suites, the artists who make movies and TV shows look the way they ...
25/11/2025
Article courtesy of Deadline
Read the article
The Brutalist' & Bad Bunny's Nuevayol' Music Video Among 2025 FilmLight Colour Award Winners - Cam...
24/11/2025
Robyn made her long-awaited return to the stage this week, as Spotify and Acne Studios brought friends and top fans together for an unforgettable evening at the...
24/11/2025
After more than two years of redevelopment, FC Barcelona returned to its spiritual home on November 22, hosting Athletic Club in the first La Liga match at the ...
24/11/2025
24 Nov 2025
Kyivstar Launches Starlink Direct to Cell Satellite Connectivity in Ukraine Today's Launch Makes Ukraine the First Country in Europe Where Star...
24/11/2025
Ahead of the new ninth series of Dancing with the Stars, kicking off in January 2026, RT and Shinawil have announced the arrival of three new faces to the hit ...
Circuit switched networks physically connect two endpoints using a communication channel through the network. This utilises a fixed bandwidth for the session whilst the two endpoints remain connected. Packet switched networks offer the ability to split the communication channel into small packets to be sent across the network using multiple routes offering redundancy and increased performance. This utilises dynamic bandwidth management which can be optimised for each connected party and allows for many more services and connections to be active at the same time using the same bandwidth.
