Effective emergency and natural disaster management depend on the efficient mission-critical voice and data communication between first responders and victims. Land mobile radio system (LMRS) is a legacy narrowband technology used for critical voice communications with limited use for data applications. Recently, long term evolution (LTE) emerged as a broadband communication technology that has a potential to transform the capabilities of public safety technologies by providing broadband, ubiquitous, and mission-critical voice and data support. For example, in the United States, FirstNet is building a nationwide coast-to-coast public safety network based on LTE broadband technology. This paper presents a comparative survey of legacy and the LTE-based public safety networks, and discusses the LMRS-LTE convergence as well as mission-critical push-to-talk over LTE. A simulation study of LMRS and LTE band class 14 technologies is provided using the NS-3 open source tool. An experimental study of APCO-25 and LTE band class 14 is also conducted using software-defined radio to enhance the understanding of the public safety systems. Finally, emerging technologies that may have strong potential for use in public safety networks are reviewed.
In this paper our focus is more on the comparative analysis of legacy and emerging technologies for PSC, when compared with the contributions in @cite_186 @cite_211 @cite_194 . We take up the public safety spectrum allocation in the United States as a case study, and present an overview of spectrum allocation in VHF, UHF, 700 MHz, 800, MHz, 900 MHz, and 4.9 GHz bands for various public safety entities. We also provide a holistic view on the current status of the broadband PSN in other regions such as the European Union, the United Kingdom, and Canada.
@cite_211 @cite_186 @cite_194
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The lack of available unlicensed spectrum together with the increasing spectrum demand by multimedia applications has resulted in a spectrum scarcity problem, which affects satellite communications (SatCom) as well as terrestrial systems. The goal of this paper is to propose resource allocation (RA) techniques, i.e., carrier, power, and bandwidth allocation, for a cognitive spectrum utilization scenario where the satellite system aims at exploiting the spectrum allocated to terrestrial networks as the incumbent users without imposing harmful interference to them. In particular, we focus on the microwave frequency bands 17.7–19.7 GHz for the cognitive satellite downlink and 27.5–29.5 GHz for the cognitive satellite uplink, although the proposed techniques can be easily extended to other bands. In the first case, assuming that the satellite terminals are equipped with multiple low block noise converters (LNB), we propose a joint beamforming and carrier allocation scheme to enable cognitive space-to-Earth communications in the shared spectrum where fixed service (FS) microwave links have priority of operation. In the second case, however, the cognitive satellite uplink should not cause harmful interference to the incumbent FS system. For the latter, we propose a joint power and carrier allocation (JPCA) strategy followed by a bandwidth allocation scheme, which guarantees protection of the terrestrial FS system while maximizing the satellite total throughput. The proposed cognitive satellite exploitation techniques are validated with numerical simulations considering realistic system parameters. It is shown that the proposed cognitive exploitation framework represents a promising approach for enhancing the throughput of conventional satellite systems. Wide-spread provisioning of TV services has strongly shaped the cultural development since the last century; terrestrial radio broadcast transmission has been the original form of TV distribution. Although the majority of TV reception is today based on alternative distribution means, like cable or satellite, TV broadcast enjoys still a significant amount of allocated terrestrial spectrum (∼300 MHz). However, it has been identified that TV broadcast does not efficiently use its allocated spectrum. At the same time, other spectrum users like mobile communication systems experience a tremendous growth and demand for spectrum. The scarcity of radio spectrum has led the US FCC rule that additional 500 MHz of spectrum are to be identified for mobile broadband systems in the next decade — out of which 120 MHz are to come from the TV band in the next 5 years. In this paper we identify an alternative transmission architecture for TV distribution based on cellular LTE MBMS, with densely placed low-power transmitters that transmit in a synchronized single frequency network. It is demonstrated that in this way a full frequency reuse at all sites is possible, in contrast to the large reuse distances in high-power high-tower TV transmission. As a result, we show that it is possible to support TV services with 84 MHz of spectrum via LTE MBMS, in contrast to the 300 MHz used by today's ATSC TV broadcast system. This approach can be realized in a cost-effective manner by re-using existing mobile network infrastructure and we also show that the total radiated power can be decreased. Since the inception of mobile radio, public safety agencies have relied on wireless communication systems to coordinate day-to-day and emergency operations. The decentralized and autonomous nature of the various public safety agencies in the United States has led to the deployment of a variety of systems operating in a fragmented spectrum, ranging from lower VHF to upper UHF. Due to the narrowband technologies used in public safety communications systems, public safety agencies have been limited primarily to voice services and low-speed data transfer on their private networks. In contrast, the commercial cellular sector now offers a large portfolio of services that include voice, messaging, email, Web browsing, picture transfer, video streaming, and other wideband services. In this article, some of the factors driving the expansion of spectrum allocated to public safety agencies arc described. Static spectrum allocation prohibits radio devices from using spectral bands designated for others. As a result, some bands are under-utilized while other bands are over-populated with radio devices. To remedy this problem, the concept of spectrum agility has been considered so as to enable devices to opportunistically utilize others' spectral bands. In order to help realize this concept, we establish an analytical model to derive performance metrics, including spectrum utilization and spectrum-access blocking time in spectral-agile communication systems. We then propose three basic building blocks for spectral-agile systems, namely spectrum opportunity discovery, spectrum opportunity management, and spectrum usage coordination, and develop protocols for each blocks. These protocols are integrated with the IEEE 802.11 protocol, and simulated using ns-2 to evaluate the protocol overhead. The simulation results show that our proposed protocols can improve the throughput of an IEEE 802.11 wireless LAN by 90 for the simulated scenarios, and the improvements matched well our analytical model. These results demonstrate the great potential of using spectrum agility for improving spectral utilization in an efficient, distributed, and autonomous manner