LTE in Public Safety

Public safety :

Public safety network is a wireless communication network used by emergency services organizations, to prevent or respond to various incidents. Many organizations are turning to mobile computing and other applications so that they can improve the efficiency of their networks . public safety workers are equipped with wireless laptops, various handheld devices in order to improve efficiency.

Today, the commercial cellular networks are driven by the needs of various consumers and business users, each and every user is dependent on the network for their tasks. With the cellular technologies advancements like 4G which is capable of transmitting data at huge data rates in mbps, also it has voice, messaging and multimedia capabilities.

Public safety networks provides communications for various services like police, fire department, ambulance services. For such applications of public safety , various safety standards have been developed for public safety networks like TETRA and P25. these provides a set of standards which are not being used in commercial cellular networks. These set of standards are also being used for mission critical communications like for airport operations. In comparison of the market scenarios of the public safety networks and the commercial networks, the market rate of public safety networks are much smaller.

LTE in public safety :

The idea of application of LTE technology to public safety networks came from USA.

Various recognized organisations including NPSTC (national public safety telecommunications council ) proposed an idea of using LTE in public safety networks. USA has reserved bandwidth of 700 Mhz for public safety networks. Implementation of public safety networks should be in such a way that it will be beneficial for consumer and business applications . A variety of standards are currently used for public safety communications globally like TETRA ( terrestrial trunked radio ) technology . TCCA (TETRA and critical communications associations ) has build up a system that provide support for broadband solutions for mission critical and business critical comparison with other, LTE technology is best to provide such solutions.

3GPP’s objective in public safety is to preserve the considerable strengths of LTE and addition of additional features required for public safety. For 3GPP LTE enhancements, there is requirement of proximity services that identifies mobiles in physical proximity and enables communications between them. The feature of Group call system enablers that provides efficient communications among group of users. Proximity services mainly consists of two main elements: network assisted discovery of users with a desire to communicate with users who are in physical proximity with one another , users can communicate with each other with or without supervision from the network.

In this there is direct communication which means that a radio connection is established between the user’s mobiles without transiting via network , main benefit of this is that we can save the network resources and users can communicate in such areas as well where there is no network access which means there is public safety as users can communicate even if there is no coverage.

Relay feature:

Because of this feature, user equipment can act as relay which means that one mobile can act as a relay for other devices in the network and it can provide access to services even if the device is not in coverage area of the network.

Another important feature in public safety is group calls or group communications . public safety users frequently need to communicate in dynamic groups . in dynamic groups, there are mobile users and fixed users , fixed users commonly known as dispatchers which are working in the control centre. LTE feature of group communications can enable group call communications for public safety networks.

Commercial LTE-A is applicable to public safety, however this release offers only consumer level services without specific LTE public safety features. With new release in LTE which is LTE rel -14 it offers same features as that of LTE-A with mission critical push to talk services . mission critical voice and mission critical video are the services which are added in release 15 . so Rel-14 can be implemented on public safety networks, because the features in rel-14 are good enough to support all features of public safety.

5G for public safety :

With release 15 & 16 , 5G technology will start its operation.some of the operations of 5G which are beneficial for public safety as:

Reliability and security: 5G technology is more reliable and secure which is most important feature for public safety. Some technologies like D2D ( device to device communications ), separation of user plane and data plane , concept of SDN and MEC ( mobile edge computing ) are important for public safety.

Critical communications networks needs to be designed for worst scenarios. 5G will add new technologies to the existing ones , which enables different use cases with different requirements in one physical network. With the concept of network slicing , the network can be divided into various slices with network functions virtualization. IOT is the key feature of 5G technology. With this, large number of machines that can communicate with each other, exchange data and automate processes. New radio interface aimed at supporting very high frequencies i.e very small cells all related to public safety have to be identified. With respect to public safety , there are some services which are to be developed :

Mission critical push to talk with group call setup within 300 ms and maximum end to end delay of 150 ms.

Group communications system enablers , proximity services which are equivalent to TETRA DMO ( direct mode operation ), isolated operation for public safety and mission critical video and data services.

The LTE network should be interoperable with existing PPDR networks (TETRA & TETRAPOL ).

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