# PS-CARA: Context-Aware Resource Allocation Scheme for Mobile Public Safety Networks
## 5 Proposed PS-CARA Scheme for mPC  
Deployment: We propose PS-CARA scheme under the SDN-based cloud network architecture because of its capability to centrally manage all the base stations. The number of mPC required per macro BS varies according to the deployment situation or scenario. That is, in the PS scenario a higher number of mPCs are desired to meet the user requirements. Therefore, more mPCs are deployed in PS scenario and the resources are allocated by considering the context information of the users. BH, SH, and AL resource allocation: In the proposed scheme, mPUE and MUE are connected to mPC and MBS, respectively via AL, whereas mPCs are connected to MBS via BH links. Similarly, mPC is connected with neighbor mPC by using SH links. All these links are using the orthogonal frequency band in order to avoid interference. mPC can switch to use different BH and SH modes to allocate different ratio of resources for BH and SH depending on the nature of deployment situation. That is, more BH resources can be reserved for non-PS deployment and less for PS scenario. For example, the system with 10 MHz BW and 50 RBs in non-PS scenario, has RB distribution ratio of BH:SH:AL \(=R/2\):\(R/4\):\(R/4\), whereas for PS scenario, this ratio can be BH:SH:AL \(=(R/4\):\(R/2\):\(R/4)\). The reason for this dynamical variation of RBs is the deployment situation, because in non-PS scenario, there is a lower possibility of SH communication between the mPCs. While in the PS situation, due to multi-hop communication between mPC, there is more demand of SH communication, and hence more SH resources are required. Thus, in the proposed PS-CARA scheme, these resources are dynamically adjusted, and one of the possible combinations is shown in Figure 3.  
mPC call admission control (CAC): In LTE system, CAC determines whether to accept or reject a new call based on the availability of sufficient network resources to guarantee the QoS parameterswithout affecting the existing calls. Since CAC is the connection provisioning module in mPC for the user initially accessing the system. Therefore, CAC is capable of identifying the call type at any moment. Hence, the number of PS users are decided based on the connection request information. However, if there is a large number of PS users sending the connection request to mPC, then mPC will switch to PS mode from the non-PS mode and start assigning resources based on PS scenario deployment configuration. Context-information collection: We use the context information by considering the PS priority of the users to dynamically schedule and allocate the resources. There are two types of context information (1) location information which is decided based on received SINR, that is if \(\gamma^{\text{rx}}<\gamma^{\text{th}}\), user is located at cell-edge and vice versa, (2) the number of PS users sending the emergency connection request is decided by CAC. The users are prioritized by considering the connection priority defined in Table 2. In this paper, we modeled the PS scenario where PS users are greater than the non-PS users, and generally we divided the users into two broad categories, that is PS users and commercial non-PS users. Since our interest is to check the performance of PS scenario, we deploy a greater number of PS users as compared with non-PS users. The priority of the users is decided by the priority indicator variable \(\delta\), that is when \(\delta=1\), the user has high priority and vice versa. The main steps in the proposed PS-CARA scheme are shown in Figure 4. The important steps of the proposed PS-CARA scheme are also described here by providing brief details as  
**PS and non-PS user resource allocation**: During this phase, firstly, all resources are reserved for PS users with high connection priority; then, based on round robin scheduling these resources are distributed among the high-priority users to maximize their sum rate.