This blog is by Al Jette at Nokia Networks.
Making sure Mission Critical Voice is heard on LTE
In the year since our original paper on LTE for Public Safety*, Nokia has continued to work with industry partners to evolve LTE for Public Safety. As previously noted, 3GPP LTE Rel-11 provides an excellent broadband data system for PPDR (Public Protection and Disaster Relief). For the past year, a majority of the standards focus has been on adding Mission Critical Voice on LTE for Public Safety.
Public Safety officials deal with life or death situations where their communication needs special treatment – this is supported by Mission Critical Voice. When Public Safety officials depress the Push-To-Talk (PTT) button on their handset, they need to be certain their Mission Critical Voice reaches the appropriate group members.
Mission Critical Voice includes the following capabilities:
1) Group Communication: A first responder needs the ability to monitor and communicate with a number of different groups. Depressing the PTT button allows the first responder to begin communication with a specific group for which they are a member. Additional Group Communication capabilities include:
• Managing the Group Communication Session: The ability to set-up and tear-down the group call, assigning floor control (who’s audio is routed to members of the group), identifying who is talking (or has floor control), pre-emption of the current talker for a higher priority talker, etc.
• Group Management: Setting up and managing membership in multiple groups (adding or removing users from groups)
2) Reliable & Resilient Communication: Although LTE networks can be designed for providing reliable connectivity, first responders need to be able to communicate even if the network is down (following a natural disaster) or devices are out of network range. Standards are being evolved to allow relaying of communication between users to the network and also allowing users to directly connect to other users in their proximity.
3GPP driving standards work
3GPP has been actively working on these capabilities in Release 12 (scheduled to be completed by March 2015) and will continue into Release-13 (expected to be completed in 2016).
Managing the Group Communication Session will be mostly handled at the application level between the handset application and an application server in the network. In a recent multi-forum industry meeting it was agreed that 3GPP will develop standards for the Mission Critical Push-to-Talk application. 3GPP will address the Group Communication Services (GCS) Application Server (AS) interface standards work in Rel-13.
Reliable and Resilient Communications involves a number of components. One aspect is to allow devices to directly communicate (with or without the help of an eNodeB). If the device is within network coverage, the eNB can assign resources for device-to-device (D2D) communication and the network can help to identify nearby devices for communication. The D2D communication related work in 3GPP is being handled under the Proximity Services (ProSe) work item. ProSe becomes more complex when there is no eNB to help identify other nearby Public Safety Users, since the device itself needs to handle discovery of other nearby devices (this off-network discovery capability is planned for Release 13). Public safety users outside eNB coverage may require other public safety devices to relay their communication to the network (this is also planned for Release 13). Another identified capability for Reliable and Resilient Communication is for an eNB to be able to operate (in a limited manner) if it loses communication with the core network partially or totally (this work is done in 3GPP under “Isolated E-UTRAN Operation for Public Safety”).
The Association of Public Safety Communications Officials (APCO) and the National Public Safety Telecommunications Council (NPSTC) have also been quite busy producing additional requirements and reports. In May 2014 a collaborative effort between APCO and NPSTC published a document defining the term “Public Safety Grade”. NPSTC has also been working on better quantifying the Broadband Launch Requirements for the National Public Safety Broadband Network.
North American standards organizations ATIS and TIA have been defining use cases and requirements for the interworking of Mission Critical Voice between LMR and LTE public safety systems.
ITU-R WP5A has also been actively working on broadband PPDR. They have been documenting global requirements and investigating the possibility of having a global radio band assigned for broadband PPDR equipment (this could reduce equipment cost).
As noted above, there has been a tremendous effort to standardize Mission Critical Voice for LTE and Release 12 will address a number of the basic capabilities. However, Nokia recognizes that additional work is needed and will continue to address Public Safety needs on LTE.
Nokia also remains committed to work with the Public Safety community to ensure their needs can be met by the LTE standards. Nokia continues to actively participate in the above standards work and is rapporteur for the 3GPP Release 13 feature: ”Service Requirements Maintenance for Group Communication System Enablers for LTE”.
In summary the commercial cellular standards bodies have welcomed collaboration with the Public Safety community to add specific features. Mission Critical Voice is a rather complex feature with many components. Significant progress has been made to add MCV into LTE Release-12, however, it will require additional time (Release-13) for completion. Nokia has been and will continue to be an industry dominant player in 3GPP to add support for Public Safety features in LTE.
* Nokia will publish an updated Whitepaper on Public Safety by the end of 2014.
For further reference:
LTE Group Communication System Enablers (Stage 2 spec)
LTE Proximity-based Services (Stage 2 spec)
LTE Isolated E-UTRAN operation for Public Safety (aka: Reliable and Resilient Communication for Public Safety)
NPTST / APCO Public Safety Grade Report:
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