Next Generation Public Safety Networks Based on LTE

Public safety is one of the major area of interest for governments around the world. In the modern world, technology touches and changes our lives continuously. Everyone wants to be connected all the time and new technologies like LTE, Wi-Fi etc play important roles. Almost everyone has a good quality smartphone and the penetration of smart phones is increasing on a daily basis. This leads us to think of requirements for Public Safety Systems (PSS) and redefine the already existing PSS.

Next Generation Public Safety Networks Based on LTE

Some of the basic scenarios for PSS are listed below:

  • Disaster management for handling natural calamities like earthquakes, floods etc.
  • Emergency situations like terrorist attacks in a city, riots, crowd management etc.
  • Emergency squads like fire fighters, ambulance, police etc.

Therefore from a good governance perspective it is evident that we need to have a good PSS system in place. APSS which caters to the requirement of the new age generation is an added advantage to any government. Several governments worldwide have chosen to upgrade PSS – In US FirstNet is establishing a nationwide, interoperable public safety broadband network dedicated for first responders. FirstNet chooses LTE as the next generation public safety technology and similar discussions are ongoing in EU and the rest of the world. It seems that the future of PSS will be based on LTE (probably a modified version) along with the existing proven PSS like Project 25, TETRA, Digital Mobile Radio (DMR), NXDN etc which are based on narrowband technology and are proven systems for voice communication.

PSS is seen as mission critical communication which has different requirements from the commercial cellular communication. Critical communication should be robust, reliable, guaranteed access as per QoS, support group operation and provide priority control. Due to the stringent requirements, critical communication is quite expensive, especially because of lower call volumes and has a slow evolution in terms of standardization.

The Third Generation Partnership Project (3GPP) is actively working on the features suitable for PSS to ensure that LTE meets the stringent requirements of PSS. Some of the most useful LTE features for PSS are listed below and we will discuss them in this blog. Some of them are already available as per 3GPP Release 13 with study items published for them. We will touch base on these features in brief in this blog.

S.No. Work Item References
1 Group Communication 22.468, 22.146, 22.246
2 Proximity based services (ProSe) 23.303
3 Isolated E-UTRAN Operations for Public Safety(IOPS Operation) 22.346, 33.401
4 High Power UE (band 14) 36.837
5 Mission Critical Push to Talk 22.280, 22.179, 23.179, 23.779
6 Mission Critical Data 22.281
7 Mission Critical Video 22.282
8 Location based services, User Equipment (UE) positioning 36.305


High Power UE (HPUE) is a special class UE introduced for LTE in band 14 (700MHz). Band 14 is designated as Public Safety Band in US. Commercial UEs are allowed to transmit at a maximum output power of 23 dBm, while the HPUEs are allowed to transmit with an output power of up to 31 dBm. Since the transmission range depends on the transmit power, the cell range can be increased, leading to higher coverage.

Group communication is one of the most critical requirement for PSS, enabling co-ordination among first and second responders during any emergency situation. It may include broadcasting of data to all users (e.g. information related to the current situation) and communication between closed groups. LTE already has features like Evolved Multimedia Broadcast/Multicast Service (eMBMS) and Single Cell Point-To-Multipoint (SC-PTM) to support all these requirements. eMBMS can provide facility to broadcast data to all UEs of eNodeB and can be utilized to broadcast multimedia content to the users. To broadcast only warning messages, we can use features like Public Warning System (PWS) and Earthquake and Tsunami Warning System (ETWS). SC-PTM allows broadcasting of data to the members of a particular group which could include a group of first and second responders.

Isolated E-UTRAN (IOPS) concept is specifically derived for public safety. In this case the eNodeB can still work after its connection with backhaul is lost. This is very useful in cases like earthquake, floods etc. For IOPS operations, the capability of the eNodeB is enhanced to detect the failure of backhaul (all EPCs to which the eNodeB is connected) and then the eNodeB searches for a locally available EPC. If yes, the eNodeB connects to the local EPC and become operational for the UEs within its cell range to provide local communication only. This ENodeB is termed as an “IOPS capable eNodeB”. Using this concept, we can make Nomadic-eNodeB (NeNB) which can roam easily and provide services across cells. This concept is quite similar to the “Network-In-A-Box” kind of solution where eNodeB and EPC co-exist in a single box and thus can be deployed quickly. Some public surveillance systems are also based on this concept.

Mission critical services i.e. MCX with X = Push to talk (PTT) or X= Video or X= Data are defined keeping in mind quick setup time, high availability, reliability and priority handling. These kind of services are required if LTE wants to position itself as the technology for the next generation PSS. MCPTT is already defined in 3GPP release 13 and the base for other services i.e. MCVideo & MCData is already available and is work in progress. For MCX, changes are required at UE (MCX client) side and top of the session initiation protocol (SIP) core as dedicated application servers for MCX (Group Communication Service Application Server). LTE eMBMS & SC-PTM technology is well suited for group communication which forms a major part of the Public Safety related communication along with unicast communication and ProSe/D2D for off-network communication. 3GPP also proposes enhancements for MCX in areas like service continuity, better resource allocation for QoS etc. Please refer to 3GPP section 23.780 for more details. Apart from PSS, MCX is very useful for use cases like unmanned vehicles in the form of drones, robotics, railways etc.

ProSe are services based on the UEs being in proximity to each other (device-2-device technology). It improves the user experience and resource utilization by taking advantage of users’ proximity to each other. ProSe includes direct discovery, direct communication, EPC level ProSe discovery, EPC support for WLAN direct communication etc. From a PSS perspective, it is very useful in case of no coverage or partial coverage. A new concept “SideLink” is developed to achieve this and device to device (D2D) communication is referred to as sidelink transmission. New physical layer channels are defined along with changes in resource allocation and signaling changes at eNodeB for sidelink communication.

UE positioning is a very important feature in PSS, as first responders need to know the precise location of the people who require help and the location of their own team so that help can be provided in an optimal manner. 3GPP has defined several methods for deriving location of the UE and these methods used in plurality should be an integral part of a PSS. We have already discussed about UE positioning methods in other blog.

Hence, the feature set of LTE can unlock the full potential of next generation PSS. First responders can manage a situation with drones and other unmanned vehicles, video surveillance, live video feedback, better positioning information and better co-ordination among different teams. If first responders are equipped with better technology, governments can help save more lives in case of disasters.

Aricent has a suite of LTE solutions and a proven base platform for eNodeB & EPC which helps reduce time-to-market. Aricent also has a base platform for UE identification solution.

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