A Framework for Push-to-Talk Service Implementation using Voice over LTE (VoLTE) and its Key Features

With the recent advancement in wireless technology and enhanced smartphone capabilities, there has been an apparent increase in the utilisation of Push-To-Talk over Cellular (PTToC).  PTToC is a feature which can only be implemented when Voice-over-Long Term Evolution (VoLTE) capability is installed in the cellular networks. PTToChas wide coverage since it uses a cellular network. Moreover, PTToC is implemented as a data call. Therefore, calls can be made even when voice channels are congested. A pictorial representation of PTToC is shown in figure 1 below.


Figure 1: An illustration of PTToC using various cellular networks.

The Role of PTToC in Mission Critical Communications

With the advancement in telecommunications, the PTToC utility is currently being used in many commercial applications, for example, Public Safety networks and business critical sectors. This technology works in harmony with Mission-Critical applications offered by the Land Mobile Radio (LMR) networks. Today’s cutting edge communication techniques have enabled organisations to combine traditional voice communication with growing data sources in order to make better and faster decisions. PTToC is an essential component of LTE-based solutions. Moreover, encrypted Push-to-Talk over cellular offers enhanced features such as location tracking, group texting and image messaging for real-time communications.

Key PTToC Capabilities

PTToC offers multiple benefits for the agencies and organisations in commercial and business sectors by giving mission critical services. A brief description of the PTToC salient features is given below.

Instant Global Connectivity

Since PTToC is operating on modern digital cellular network standards, the entire world has now same network infrastructure. Public safety agencies can now connect any where around the globe in the same way as it would connect with the terrestrial-based trunked radio systems.

Fast and secure public safety networks

PTToChas connection speeds equivalent to land-mobile radio communication. Thus,byintegrating the benefits of PTToC and LMR, users can be facilitated with seamless mobile communication. With the introduction of encrypted PTToC, organisations are able to increase the number of users, in order to make them capable of communicating over a DMR network in a secure way.

Flexibility in critical communication services

This technology is well suited to a wide-range of devices. The user can use this technology with their choice of device. PTToC is very handy so that field workers can use it easily while working in remote areas and harsh environments. Group call in PTToC enables users to exchange information simultaneously with multiple users, and by this means all the group members are fully aware of the situation.

In summary, the rise in the usage off PTToC is due to the speed offered by 3G and 4G mobile networks and the introduction of smartphones. With the introduction of new applications for PTToC technology, it seems that PTToC communications will be an essential component of emerging LTE-based solutions.

To further know about implementation of VoLTE, Technologies, Challenges, and RCS for Public Service, you can join our  Voice over LTE (VoLTE) and RCS Certification Courses here.

Nokia Networks Advancing to LTE-A Carrier Aggregation Deployment

Nokia Networks is already globally known for its spectrum re-sharing, load balancing and traffic steering in different aspects. Now it is upgrading LTE-A technology globally that offers higher data rates to the subscribers and LTE operators.

Recently, in September 2015, the Nokia Networks have upgraded the Softbank’s commercial network by deploying LTE-A with faster data rates of up to 262.5 Mbps as claimed officially. The 1.4 times faster LTE-A technology has been facilitated with 3-band carrier aggregation on the commercial network.

By upgrading the LTE radio network to LTE Advanced Carrier Aggregation, the mobile network can now be benefitted with three component carriers besides the two aggregated bands. In carrier aggregation technology, 10 MHz spectrum sources are aggregated on the 900 MHz band as well as the 1800 MHz band. While, 15 MHz spectrum sources are aggregated on the 2100 MHz band. To derive the data rate even faster, a data highway of 35 MHz has been deployed in the network which offers about 262.5 Mbps downlink data rates to the subscribers.

The LTE-Advanced Carrier Aggregation technology evolves alongside the subscribers’ demands for higher data rates as well as the capability of their smartphones to support the band combinations of Carrier Aggregation. Today the user equipment are being built to aggregate up to three frequency bands, while some equipment have already been into the market which aggregate two frequency bands at a time. The new LTE-A software by Nokia Networks facilitates the subscribers to achieve the highest data rates that can be supported by their devices and smartphones. With this technology, any combination of the bands can be aggregated out of the three frequency bands.

So far we have discussed the advantages of the LTE-A Carrier Aggregation Technology for the users and subscribers. If we analyze the benefits of this technology from the operators’ point of view, we find out that the LTE operators will now able to drive the development of a wider range of smartphone ecosystem with the three frequency band aggregation technology.

Since SoftBank is considered as one of the top ten largest LTE Operators worldwide, this new frequency band combination will be widely installed in the markets around the globe. When the 900 MHz band for 2G is reframed to the 1800 MHz band for LTE, and the 2100 MHz band for 3G is reframed on the LTE band, the LTE operators get the advantage of higher data rates due to this carrier aggregation of three components.

The LTE-Advanced Carrier Aggregation technology deployment has opened new horizons in the communication technology and set a global example for LTE operators in achieving higher data rates for 4G.

To further know about LTE Network Planning, LTE-A Carrier Aggregation, Implementation, and Challenges you can join our  4G LTE Radio Network Planning and Optimization and 4G LTE-A Certification Courses here.

TETRA Radio Evolution Archive

TETRA Radio Evolution Path to 4G LTE

TETRA Radio evolution to 4G LTE is essential in order to enhance the mission critical emergency communication services. A framework for smooth transition of TETRA RADIO to LTE is shown below.

tetra radio evolution to LTE

For smooth transition of TETRA Radio to LTE, initially the critical voice and data messages will run in the narrowband TETRA network, while the high speed non-critical yet secured data will run in the commercial LTE broadband network. A technical architecture of TETRA Radio smooth transition to LTE is shown below:

TETRA Radio Evolution to TETRA 3 Broadband TETRA

Most recently, TETRA standardization bodies have identified user requirements for broadband mission critical data applications which include transfer of multimedia video and photo transfer, location data,  office applications, upload and download of operational information and online database enquiries. As a result, ETSI TC TETRA has initiated a new work item to expand the TETRA standard for transfer of broadband packet data which is scheduled until the end of 2016. Even the whole TETRA industry is extremely uncertain in the moment whether TETRA is already a legacy technology and will shortly be replaced by mission critical LTE.

tetra radio evolution training

UK & USA plan to replace TETRA with LTE until 2016 for Critical Communications & Public Safety

Within the next three years, LTE could replace the TETRA system that currently provides mission-critical communications for public-safety agencies and other government organizations in Great Britain, an official said yesterday.

Since 2005, mission-critical communications have been transmitted over the Airwave system—a privately owned TETRA network that covers 99% of the land mass and 98% of the population in Great Britain (England, Scotland and Wales). It serves “all three emergency services and other national users” that pay subscriptions fees, according to Gordon Shipley of the United Kingdom Home Office. Although the performance of the TETRA system is “very good,” it is “extremely expensive” for users, particularly when compared to the plummeting per-minute costs of commercial wireless air time, he said.

In addition, the contracts associated with the Airwave system are scheduled to expire from 2016 to 2020, so the UK Home Office is looking for alternatives, Shipley said.

“Because [the Airwave network is] a TETRA-based system, it’s narrowband data,” Shipley said during the session. “One of the things which has become clear is that the emergency services are now increasingly going broadband services, which can provide even higher speeds. And we need to provide a better, more reliable and secure service for broadband, as well as narrowband voice. So, my program’s responsibility is to find a replacement for critical voice, as well broadband data services, and to do so cost effectively.

“We think, in the UK, that 4G LTE promises significant benefits over the current service that we buy.”

UK officials will conduct a supplier conference next month to get input on the notion of having a public-safety LTE system operational in December 2016, with the entire system transitioned to the 4G technology by 2020, Shipley said.

This development could have an impact in the United States, which is trying to get 3GPP—the global standards body for LTE—to include public-safety requirements such as mission-critical voice in future revisions of LTE that can be implemented in the nationwide broadband network being built by FirstNet, according to Andrew Thiessen, who helps lead the standards effort for Public Safety Communications Research (PSCR), a unit of the U.S. Dept. of Commerce.

“I think it’s imperative that everyone in the audience understand that the United States isn’t the only country that’s actually looking forward to LTE,” Thiessen said during the session. “In many ways, the United Kingdom is actually working faster than FirstNet, looking at a 2016 date for mission-critical voice.”

Of course, one of the key requirements for public safety is mission-critical, push-to-talk voice. A draft set of requirements for push-to-talk over LTE has been distributed to officials in other countries, and the initial response has been positive, Thiessen said.

“We’re actually getting pretty close,” he said. “The comments that we’re getting back are more about clarification of what a particular sentence meant and less so about, ‘Well, we view things very differently.’ Public safety operates fairly similar globally, so push to talk is push to talk, whether it’s TETRA or P25 or whether it’s the United Kingdom or the United States—the expectations of the user community are very similar.”

A Roadmap For Cellular Networks Evolution Towards LTE-Advance Networks

lte 5g

What is 4G LTE-Advanced?

LTE-Advanced is the next level mobile broadband LTE technology. It is the faster version of the already fast wideband 4G. Some major networks in the UK and in the United States prominently, Sprint and T-mobile which are currently operating in the United States have already upgraded to LTE-Advanced. Wireless specialists have declared LTE-Advanced “True 4G” because it meets the specifications set by International Telecommunication Union’s (ITU) for 4G wireless systems. The goal is to provide a communication system which not only provides faster data speeds but also supports many more devices online at the same time with reduced latency. In order to meet the goal, the network providers are continuing to evolve the current LTE standard that is leading towards the 5G standards, which is known as LTE-Advanced Pro. As a result, we will get higher network capacity, more consistent connection,and cheaper data rates. A timeline for the progress in LTE standards towards 5G is shown in Figure 1 below.

lte 5g

Figure 1: Timeline for advancement in LTE-Advanced towards 5G.


How fast is LTE-Advance?

The main objective of LTE-Advanced is to add the IMT-Advanced functionality while maintaining the compatibility with LTE user equipment. It is important because if not enabled, the early adopters would be penalized when the carrier is upgraded to LTE-Advanced on the infrastructure side. LTE-Advanced is designed to provide the data rate up to 300 Mbps for downloading and 75 Mbps for uploads. Moreover, LTE-Advanced includes some new transmission protocols and multiple-antenna schemes (MIMO) which enable smoother handoffs between cells and increase throughput at cell edges. A graphical illustration of data rates of different releases of is shown in figure 2 below.

lte 5g

Figure 2:   A Bar graph showing the comparison of data rates among different versions of LTE.

What LTE-Advanced adds to LTE?

LTE-Advanced is a speedy network. Theoretical peak download speeds are up to 300 Mbps while the standard data rate of 4G LTE is 150 Mbps. Other factors such as the type of device, proximity to a 4G mast and number of user on the network have a drastic affect on the network speed.

Moreover, LTE networks mainly use frequency reuse factor of one to maximize utilization of the assigned bandwidth. LTE uses the heterogeneous networks where the cells are of different size referred to as Macro, Micro, Pico and Femtocells. The actual cell size depends not only on eNB power but also on antenna position, as well as the environment of the location such as rural or urban, indoor or outdoor. An illustration of a heterogeneous network is shown in the figure below.
lte 5g

Figure 3: An illustration of a heterogeneous network with large and small cells.


In LTE-Advance, the technology of heterogeneous network is amalgamated with Carrier Aggregation, one of the big enablers behind faster data speeds. Carrier Aggregation enables the mobile device to receive several 4G signals of different frequencies all at once.  For example, with LTE-Advance, we can receive an 1800 MHz and 80 MHz signal at the same time. Five component carriers, each having a bandwidth up to 20 MHz are combined to fom a data pipe of up to 100 MHz of bandwidth. But in LTE-Advanced Pro release the number of component carriers will increase to 32 different carriers.


Figure 4: Illustration of Carrier Aggregation in LTE-Advanced network.

Besides Carrier Aggregation, another feature which distinguishes LTE advanced from its predecessors is Multiple Input, Multiple Output (MIMO). MIMO allows base stations and user equipment to send and receive data using multiple antennas. It serves two purposes.

  1. In noisy radio environment, the multiple transmitters and receivers function together to focus the radio signals in a single direction. This beam forming feature amplifies the strength of received signal without increasing the transmission power.
  2. It is also used to increase data rates and the number of users for a limited spectrum. Currently, LTE supports MIMO, but only for downlink. It allows four transmitters in the base stations and four receivers in the handset. While in LTE-Advanced, up to eight antennas are used for downlink and up to four pairs for uplink.


LTE-Advance User Equipment Categories

In order to utilize the services of LTE-Advanced, you might need to get a new phone because, the standard 4G phones are not compatible with LTE-Advance. Many newly introduced mobile phones such as Samsung Galaxy S6, iPhone 6s, HTC One M9, Sony Xperia Z5, LG G4 and Microsoft Lumia 950 support it. Hence, over time, smarter phones will be introduced with LTE-Advanced support and as it becomes more widespread it should start filtering down to low-end devices too.

Towards next-generation Cellular Networks

Telecommunication is a fast evolving industry. The term 5G is abbreviated as Fifth Generation of mobile wireless systems. It is expected to be a big step as it promises to give high data rates along with IoT and other cutting-edge services. The specifications are still under development and it is expected to be deployed by 2020. The main goal of 5G is to receive data speeds up to 1 Gbps, which is a mind blogging number.

To further know about LTE Network Planning, LTE-A Carrier Aggregation, Implementation, and Challenges you can join our  4G LTE Radio Network Planning and Optimization and 4G LTE-A Certification Courses here