In recent times, the rapid growth in mobile subscriptions and the associated demand for high data rates fuels the need for a robust wireless network design to meet the required capacity and coverage. Deploying massive numbers of cellular base stations (BSs) over a geographic area to fulfill high-capacity demands and broad network coverage is quite challenging due to inter-cell interference and significant rate variations. Cell-free massive MIMO (CF-mMIMO), a key enabler for 5G and 6G wireless networks, has been identified as an innovative technology to address this problem. In CF-mMIMO, many irregularly scattered single access points (APs) are linked to a central processing unit (CPU) via a backhaul network that coherently serves a limited number of mobile stations (MSs) to achieve high energy efficiency (EE) and spectral gains. This paper presents key areas of applications of CF-mMIMO in the ubiquitous 5G, and the envisioned 6G wireless networks. First, a foundational background on massive MIMO solutions-cellular massive MIMO, network MIMO, and CF-mMIMO is presented, focusing on the application areas and associated challenges. Additionally, CF-mMIMO architectures, design considerations, and system modeling are discussed extensively. Furthermore, the key areas of application of CF-mMIMO such as simultaneous wireless information and power transfer (SWIPT), channel hardening, hardware efficiency, power control, non-orthogonal multiple access (NOMA), spectral efficiency (SE), and EE are discussed exhaustively. Finally, the research directions, open issues, and lessons learned to stimulate cutting-edge research in this emerging domain of wireless communications are highlighted.
<div class="WordSection1"><p>Losses during transmission and high demand of high data rate by the end users have become the biggest challenges facing the telecommunication industries worldwide with Nigeria inclusive. Fiber optic cable as a channel of communication has been adapted worldwide in solving these problems but there is a little limitation in the place of multimode fiber in long distance communication. This paper focuses on the effect of changes in distance on transmitted bandwidth on single mode and multimode fiber. Two cases were considered during this research; (a) with optical amplifier placed in between multimode fiber and (b) without optical amplifier in between multimode fiber. Readings were taken at various distances when specific bandwidth ranging from 50Mbps to 500Mbps was transmitted from the base station to the various distances and it was observed that there was no significant changes in bandwidth received at specified distances (100, 200, 300, 400, 500 etc) m when using single mode fiber, there was a drastic reduction in bandwidth when it get to a distance of 300m when using multimode. When optical amplifier was placed in between the multimode fiber at some selected distances after 400m from the transmitting BTS, it was noticed that the drastic reduction in transmitted bandwidth was almost eliminated, thereby proven that multimode fiber can be use in long distance communication provided optical amplifiers are incorporated in between the distance to bust the signal strength.</p></div>
This article involves the site specific determination of an outdoor path loss model and Signal penetration level in some selected modern residential and office apartments in Ogbomosho, Oyo State. Measurements of signal strength and its associated location parameters referenced globally were carried out. Propagation path loss characteristics of Ogbomosho were investigated using three different locations with distinctively different yet modern building materials. Consequently, received signal strength (RSS) was measured at a distance d in meters, from appropriate base stations for various environments investigated. The data were analyzed to determine the propagation path loss exponent, signal penetration level and path loss characteristics. From calculations, the average building penetration losses were, 5.93dBm, 6.40dBm and 6.1dBm outside the hollow blocks B1, solid blocks B2 and hollow blocks mixed with pre cast asbestos B3, buildings respectively with a corresponding path loss exponent values of, 3.77, 3.80 and 3.63. Models were developed and validated, and used to predict the received power inside specific buildings. Moreover, the propagation models developed for the different building types can be used to predict the respective signal level within the building types, once the transmitter – receiver distance is known. The readings obtained from the developed models were compared with both the measured values and values computed using some existing models with satisfactory results obtained.
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