0018-9545 (c) 2017 IEEE. Personal use is permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. This article has been accepted for publication in a future issue of this journal, but has not been fully edited. Content may change prior to final publication. Citation information: DOI 10.1109/TVT.2017.2751569, IEEE Transactions on Vehicular Technology 1 Resource Allocation in Public Safety Broadband Networks with Rapid-Deployment Access Points Xu Chen, Xu Li, Dongning Guo, John Grosspietsch Abstract—A nationwide interoperable public safety broadband network is being planned by the First Responder Network Authority (FirstNet) under the auspices of the United States gov- ernment. The network will be based on the long term evolution (LTE) standards and use designated spectrum in the 700 MHz band. The public safety network has different objectives and traffic patterns than commercial wireless networks. In particular, the routine public safety traffic is relatively light, whereas when a major incident occurs, the traffic demand at the incident scene can be significantly heavier than that in a commercial network. Hence it is extremely costly to build the public safety network using conventional cellular network architecture based solely on an infrastructure of stationary base transceiver stations. A novel hybrid architecture is proposed in this paper, where stationary access points are deployed sparsely to serve light routine traffic and rapid-deployment access points are dispatched along with public safety personnel to incident scenes to support heavy traffic. Spectrum and power allocation for the public safety network is optimized with the objective of minimizing the maximum delay achieved by all user equipments. Simulation results show that the hybrid architecture with rapid-deployment access points provides the needed capacity and quality of service at a much lower cost compared with the conventional architecture. I. I NTRODUCTION The Federal Communications Commission (FCC) has des- ignated 2×10 MHz paired spectrum in the 700 MHz band for exclusive public safety use in the United States. A unified nationwide public safety broadband network is being planned by the First Responder Network Authority (FirstNet) based on long term evolution (LTE) technologies. This new public safety network and existing commercial networks have very different characteristics. Commercial networks typically have a higher user equipment (UE) density and target on a high net- work revenue by providing diverse levels of services without guaranteeing complete coverage. The public safety network, however, aims at providing immediate and reliable access (an excessive delay may cause loss of life and property) with guaranteed throughput and quality of service (QoS), as well as assured nationwide coverage. Copyright (c) 2015 IEEE. Personal use of this material is permitted. However, permission to use this material for any other purposes must be obtained from the IEEE by sending a request to pubs-permissions@ieee.org. This work was supported in part by the Motorola Center for Seamless Communications at Northwestern University and by the National Science Foundation under Grant No. CCF-1423040. X. Chen was with the Department of Electrical Engineering and Computer Science, Northwestern University, Evanston, IL. He is now with Apple Inc., Cupertino, CA 95014. X. Li is with Huawei Technology Co., Ltd., Shenzhen, China. D. Guo is with the Department of Electrical Engineering and Com- puter Science, Northwestern University, Evanston, IL 60208 (e-mail: dguo@northwestern.edu). J. Grosspietsch is with Roberson and Associates, LLC, Schaumburg, IL. The traffic pattern of the public safety network and that of commercial networks are very different. There are two typical sources of traffic in the public safety network, namely, light traffic due to routine activities such as patrols and surveillance, and temporary heavy traffic at a major incident scene due to large numbers of public safety personnel on site. A model for public safety traffic under normal and emergency scenarios has been developed in [1]. Reference [2] analyzed the public safety traffic in land mobile radio systems and found close fitting distributions for call inter-arrival time and call holding times. In [3], it is shown that the average number of busy channels in most cells is small compared to their capacities, whereas there are also periods of very high utilization. Averaged over time and across areas, the amount of routine traffic in a public safety network is much lower than that in a typical commercial network. When a major incident occurs, however, the amount of traffic reaches its peak, where the aggregate demand in a cell is at least comparable to that in a typical cell in a commercial network. In order to increase network capacity, some studies suggest that the public safety network should share spectrum with commercial networks [4], [5]. The cost of the public safety network per unit area of coverage is a critical issue. The FCC estimates the cell site density and network deployment cost of the public safety network to be comparable to a commercial network [6], while some other estimates are several times higher based on more stringent requirements [7]. It has also been proposed to build dedicated public safety networks in urban areas, and to share infrastructure with commercial networks in rural areas [8]. The network architecture must provide sufficient capacity to carry the sum of routine light traffic and temporary heavy traffic at a major incident scene. The conventional cellular network architecture is based on an infrastructure of stationary access points (APs) connected to the wired core network. If such an architecture is adopted by the nationwide public safety network, the deployment of APs needs to be wide and dense enough to meet the peak demand of public safety UEs everywhere, including both routine UEs and incident scene UEs. The utilization of the network is low most of the time in most areas, because the routine traffic is much lower than the peak traffic. In this paper, we propose a hybrid architecture for building an economic nationwide public safety broadband network. The wireless APs of the network consist of sparsely deployed sta- tionary APs for supporting light routine traffic and a distributed set of rapid-deployment APs ready to be deployed quickly to any incident scene by land vehicles, helicopters, or drones. The rapid-deployment APs are sparsely distributed across the