A Spectrally efficient PMR System Utilizing Broadcast Service

Cataloged from PDF version of article.Different trunked Private Mobile Radio (PMR) systems have been designed over the last several decades, all of which have symmetric downlink and uplink channel capacities. Due to this symmetry, these systems may not be spectrally efficient in case of different types of services, which are specific to PMR systems, such as group and broadcast calls. In this study, a new asymmetric trunked PMR system comprising a broadband, wide-area downlink and a narrowband cellular uplink, is proposed to achieve a higher spectral efficiency than current digital trunked PMR systems. This system is spectrally more efficient because in group and broadcast calls only a single downlink channel has to be allocated in the downlink part. However, as the number of clusters in the system increases, this advantage relative to PMR systems is lost, since the latter can employ frequency reuse. Spectral efficiency of the proposed asymmetric system (a-PMR) system and a standard TETRA system are compared using numerical case studies against different traffic loads and number of clusters. The optimum point, with respect to number of clusters, up to which the proposed a-PMR system is more efficient, is determined. It is shown that a very large PMR user population can be efficiently served using the proposed a-PMR system. The issues related to implementing such a system are discussed

Spectrum Allocation in Networks with Finite Sources and Data-Driven Characterization of Users\u27 Stochastic Dynamics

During emergency situations, the public safety communication systems (PSCSs) get overloaded with high traffic loads. Note that these PSCSs are finite source networks. The goal of our study is to propose techniques for an efficient allocation of spectrum in finite source networks that can help alleviate the overloading of PSCSs. In a PSCS, there are two system segments, one for the system-access control and the other for communications, each having dedicated frequency channels. The first part of our research, consisting of three projects, is based on modeling and analysis of finite source systems for optimal spectrum allocation, for both access-control and communications. In the first project, Chapter 2, we study the allocation of spectrum based on the concept of cognitive radio systems. In the second project, Chapter 3, we study the optimal communication channel allocation by call admission and preemption control. In the third project, Chapter 4, we study the optimal joint allocation of frequency channels for access-control and communications. Note that the aforementioned spectrum allocation techniques require the knowledge of the call traffic parameters and the priority levels of the users in the system. For practical systems, these required pieces of information are extracted from the call records meta-data. A key fact that should be considered while analyzing the call records is that the call arrival traffic and the users priority levels change with a change in events on the ground. This is so because a change in events on the ground affects the communication behavior of the users in the system, which affects the call arrival traffic and the priority levels of the users. Thus, the first and the foremost step in analyzing the call records data for a given user, for extracting the call traffic information, is to segment the data into time intervals of homogeneous or stationary communication behavior of the user. Note that such a segmentation of the data of a practical PSCS is the goal of our fourth project, Chapter 5, which constitutes the second part of our study