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Mission Critical Communications

Emergency Medical Technicians talking on radio


The situations under which first responders are communicating necessitate more stringent performance and availability requirements compared to non-emergency personnel. To enable the mission-critical communications, whether it is voice, video, or data, new architectures are proposed, such as Mission Critical Push-To-Talk (MCPTT) and Group Communication System Enablers for LTE (GCSE_LTE). In collaboration with public safety partners such as FirstNet, we are contributing to the 3GPP standard development process to ensure that the public safety requirements are clearly defined and that specifications have the potential to meet those requirements.

A major focus has been on off-network MCPTT mode over LTE, where users communicate using ProSe without accessing the network. An extensive set of scenarios was created to cover most of the possible combinations of call control and floor control procedures. We have been able to verify the protocols’ correctness and provide solutions to issues identified using modeling and simulation. During our research, we evaluated the time required for users to be able to talk, also called access time, under various scenarios. We developed analytical and simulation models that provide insights regarding parameter configurations and ensure that the solutions will deliver the best possible performance for first responders.

We also investigated partial-coverage scenarios in LTE, where a remote UE connects to a relay UE using ProSe in order to extend the network coverage. In these situations, the remote UE stays connected to the network and can continue to use on-network MCPTT, albeit some impact on the performance due to the extra hop. Our research highlighted the impact of parameter configuration and network load on the end user performance.



  • P. Varin, Y. Sun, and W. Garey, “NISTIR 8236 Test Scenarios for Mission Critical Push-To-Talk (MCPTT) Off-Network Mode Protocols Implementation,” 2018. [Access paper]
  • Y. Sun, W. Garey, R.A. Rouil, and P. Varin, “Access Time Analysis of MCPTT Off-Network Mode over LTE,” Wireless Communications and Mobile Computing, Volume 2019, Article ID 2729370, 19 pages. [Access paper]
  • W. Garey, Y. Sun and R. Rouil, "Performance Evaluation of Proximity Services and Wi-Fi for Public Safety Mission Critical Voice Application". [Access paper]


  • R. Rouil, A. Izquierdo, M. Souryal, C. Gentile, D. Griffith, and N. Golmie, “Nationwide safety: Nationwide modeling for broadband network services,” IEEE Veh. Technol. Mag., vol. 8, no. 2, pp. 83–91, 2013. [Access paper]
  • D. Griffith, R. Rouil, A. Izquierdo, and N. Golmie, “Measuring the resiliency of cellular base station deployments,” in 2015 IEEE Wireless Communications and Networking Conference, WCNC 2015, 2015, pp. 1625–1630. [Access paper]
  • R. Rouil, W. Garey, C. Gentile, N. Golmie, and P. Schwinghammer, “Increasing public safety broadband network resiliency through traffic control,” Digit. Commun. Networks, vol. 4, no. 1, 2018. [Access paper]


  • C. Liu, C. Shen, J. Chuang, R. A. Rouil, and H. Choi, "Throughput Analysis between Unicast and MBSFN from Link Level to System Level," 2019 IEEE 90th Vehicular Technology Conference (VTC2019-Fall), Honolulu, HI, USA, 2019, pp. 1-7. [Access paper]
  • S. Feng, C. Liu, C. Shen, H. -A. Choi, and R. A. Rouil, "An Effective and Efficient Dynamic eMBMS Multicast Grouping Scheduling Algorithm in MBSFNs for Public Safety Scenarios," in IEEE Access, vol. 8, pp. 105701-105712, 2020. [Access paper]
  • C. Liu, C. Shen, J. Chuang, R. A. Rouil, and H. -A. Choi, "Evaluating Unicast and MBSFN in Public Safety Networks," 2020 IEEE 31st Annual International Symposium on Personal, Indoor and Mobile Radio Communications, London, UK, 2020, pp. 1-7. [Access paper]
  • C. Shen, C. Liu, R. A. Rouil and H. -A. Choi, "Study of Multicast Broadcast Single Frequency Network Area in Multicast Communications," 2020 14th International Conference on Signal Processing and Communication Systems (ICSPCS), Adelaide, SA, Australia, 2020, pp. 1-8. [Access paper]
  • C. Shen, C. Liu, and R.A. Rouil, "A Comprehensive Analysis on Multicast and Unicast Performance and Selection", IEEE Global Communications Conference 2021 (Globecom), Madrid, ES, [Access paper]


Wireless Systems Innovation and Performance Group

Created July 7, 2021, Updated May 9, 2022