Increasing public safety broadband network resiliency through traffic control

Long Term Evolution (LTE)-based cellular networks are being deployed around the world to provide public safety with enhanced capabilities and access to broadband technology. In the United States, the First Responder Network Authority (FirstNet) is on the verge of deploying a nationwide network called the National Public Safety Broadband Network (NPSBN). Commercial networks typically aim at maximizing network capacity, i.e. the aggregate data rate, in order to increase revenue. However, in public safety networks, coverage, not capacity, is paramount, especially during an outage when sites are down. Through traffic control and preemption, the service level of low-priority users is reduced or denied, freeing up resources to restore coverage to high-priority users, e.g. users responding to an incident. In this study, we examine the effect of outages on network coverage and throughput. As our main contribution, we propose three traffic-control schemes that exploit variable modulation and coding, a feature that LTE enhances with respect to its 3G predecessors. The schemes differ based on the proportion of low- and high-priority users preempted. We show that the network coverage can be restored significantly and we investigate the tradeoff between the three schemes. Finally, we perform sensitivity analysis to confirm the effectiveness of the schemes across a wide range of scenarios.