Private Mobile Radio Systems Research Articles

Mission critical ICT

In this paper, three technologies intended to be implemented in Private Mobile Radio systems are analyzed and compared: TETRA (Terrestrial Trunked Radio), LTE (Long Term Evolution) and DMR (Digital Mobile Radio). Characteristics of these networks are collected and compared in one SWOT table. Based on this analysis, appropriate recommendations are made, which should be taken into account when choosing a specific solution for specific uses in Critical Communications systems.

Vulnerability of Terrestrial-Trunked Radio to Intelligent Intentional Electromagnetic Interference

The terrestrial-trunked radio (TETRA) specification is produced by the European Telecommunication Standards Institute for private mobile radio systems. We investigated the resilience of TETRA against intelligent intentional electromagnetic interference (IEMI) with low amplitude. Low power signals interfering with the higher layers of the system have the advantage of staying covert. The analysis shows that if the access assignment channel is corrupted, the mobile stations cannot start conversations with the base station. TETRA's modulation scheme is also investigated. $\pi$ /4 differential quadrature phase shift keying (QPSK) is interfered with a continuous wave and a QPSK signal. The results show that a continuous wave created the largest error vector magnitude, but creates a peak in the received spectrum. The power of the QPSK signal, however, is distributed over a bandwidth and is more difficult to detect than the continuous wave in the received spectrum. From this, we conclude that the QPSK signal functions is more effective as an intelligent interference signal compared to a continuous wave. In this paper, it is shown that it is possible to create an IEMI that combines the vulnerability in the TETRA protocol with the QPSK signal to disrupt the service to the communication system, while staying covert.

A Model for the Allocation of Limited Resources for Technological Improvement: A Case of Courier Service

One of the basic questions in the field of microeconomics is how to make decisions about allocation of limited resources for technological improvement. The aim of this study is exactly to propose a model that will help firms in making this kind of decisions. The model puts employees’ stress level in the central place. There was a hypothesis introduced that based on stress level analyses in correlation with particular parameters of business, the recommendations for improvements can be reached.As a data collection tool, two questionnaires were used. First questionnaire was related to stress test. In this paper BHC test was used (Behavioral Health Concepts team, 2000). It is a standardized questionnaire containing 27 questions. The other questionnaire contained 12 questions of which 6 was related to defining employees attitudes about predefined business parameters.In order to get information about what should be changed first Work Stress Index – WSI is introduced. Higher value of WSIi indicates that in the case of the lack of resources for comprehensive changes, higher priority in improvement should be given to business parameter i.The examinees in this study were couriers that work in courier service sector in Serbian Post. There were 29 of them included in this research. Since there were a small number of examinees in this study, Fisher's exact test was used in order to examine the correlation between stress level of employees and particular parameters of the business process. In the case of a large number of examinees (above 100) other methodology should be used (see Dobrodolac et al., 2010). To calculate correlation, a frequency distribution of appearance in some of the stress categories should be analyzed (well adjusted, stressed, very stressed and extremely stressed). In the case of WSI calculation, we treated the average values of overall scores obtained from BHC stress testOne of the improvement points that were indicated as a result of the model’s implementation was the communication between dispatcher and couriers. This segment of courier service is further analyzed in this paper.The existing communication system that was the part of public network has not met the expectations. Therefore, a new communication system should be introduced. As a possible solution, Private Mobile Radio systems, also known as communication systems for closed user groups, were proposed for implementation. In the process of communication system design it is necessary to take into account the economic parameter, i.e. the overall costs. In that sense, good characteristic of Professional Mobile Radio system is that more departments or services using communication for closed user groups may use a common infrastructure, but to have a separate functioning. Thus, the introduction of such system should involve coordinating the various administrations interested in the use of communication system for closed user groups.Finally, the main contributions of this paper are: the design of a new model for the allocation of limited resources for technological improvement, a manifestation of model’s applicability and a proposal of new communication system for courier service in Serbian Post.The advantage of the proposed model lies in its simplicity of realization and the possibility of wide application. It could be applied to different types of businesses, to both manufacturing and service industries, and also to various positions, from low working levels to highest management level.DOI: http://dx.doi.org/10.5755/j01.ee.23.4.1502

A Spectrally Efficient PMR System Utilizing Broadcast Service

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.

Assessment of specific energy absorption rate (SAR) in the head from a TETRA handset

Finite-difference time-domain (FDTD) calculations of the specific energy absorption rate (SAR) from a representative TETRA handset have been performed in an anatomically realistic model of the head. TETRA (Terrestrial Trunked Radio) is a modern digital private mobile radio system designed to meet the requirements of professional users, such as the police and fire brigade. The current frequency allocations in the UK are 380–385 MHz and 390–395 MHz for the public sector network. A comprehensive set of calculations of SAR in the head was performed for positions of the handset in front of the face and at both sides of the head. The representative TETRA handset considered, operating at 1 W in normal use, will show compliance with both the ICNIRP occupational and public exposure restrictions. The handset with a monopole antenna operating at 3 W in normal use will show compliance with both the ICNIRP occupational and public exposure restrictions. The handset with a helical antenna operating at 3 W in normal use will show compliance with the ICNIRP occupational exposure restriction but will be over the public exposure restriction by up to ∼50% if kept in the position of maximum SAR for 6 min continuously.

QoS management with dynamic bearer selection schemes

This paper presents an evaluation of a radio level QoS management scheme developed to ensure the maintenance of QoS contracts. The concept of QoS contract is defined as the specification of the quality requirement for various types of services. According to the contracted QoS, a dynamic bearer selection is performed to adapt the link to the channel quality variations. Terrestrial Trunked Radio system (TETRA) presents itself as a suitable platform for illustrating the concept of QoS contract. This arises from its feature-rich bearer services that support data and voice with varying levels of error protection. The generic QoS management scheme presented in this paper has been applied to a private mobile radio system but it also represents an appropriate platform for multi-vendor, multi-technology and multimedia environments such as those found with 3G systems.

Performance analysis of private mobile radio systemwith finite unbalanced traffic sources

An exact formula is given for the probability distribution of a call delay in a private mobile radio (PMR) system serving a number of unbalanced groups of callers, i.e. groups offering different traffic loads, which generalises a recent result for balanced groups. This formula may help to dimension PMR systems.

Land mobile satellite systems

The general advantages and potential operating characteristics of the mobile satellite service (MSS) are described, and distinctions are made between radio telephone, which is interconnected to the public switched telephone network, and private mobile radio systems. Mobile satellite service offers voice, data, position location, and paging services, interconnection to the public switched telephone network, and the possibility of private networks. Performance and cost characteristics are given along with summaries of market needs and market demands. The space and ground systems of the MSS are described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

UK trunking system signalling standard—protocol aspects

In the UK, a standard signalling protocol has been defined for trunked private mobile radio systems in Band III. This paper describes the operation of some key aspects of the protocol: the contention control mechanisms, the control channel procedures for call set-up and the signalling formats. Also, results are presented from a computer evaluation of the protocol.