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6G Networks
Published in Paulo Sergio Rufino Henrique, Ramjee Prasad, 6G The Road to the Future Wireless Technologies 2030, 2022
Paulo Sergio Rufino Henrique, Ramjee Prasad
Graphene will lead the manufacturing of UM-MIMO technology on a large scale. MIMO antenna's principles are based on the phenomenon of multipath propagation of radio signals through an area. The multipath signal is a natural effect caused by a transmitted RF signal that arrives at an antenna in different paths due to its reflection on the environment while spreading. The multipath signal result is the combined effect of constructive and destructive interference on the original RF signal that creates fading and inter-symbol interference. MIMO technology uses M antennas to send signals from multiple paths to N antennas’ destination capable of recreating the original message arriving from multiple paths. Figure 5.4 describes how MIMO technology works to reconstruct the transmitted signal.
Coding and Modulation for Free-Space Optical Communications
Published in Hamid Hemmati, Near-Earth Laser Communications, 2020
Fading may be mitigated at a system level by introducing diversity into the communication system. For example, to mitigate pointing errors, one can utilize multiple transmit beams with separate pointing control systems such that the instantaneous pointing errors are uncorrelated. To mitigate scintillation one can use a larger aperture, averaging over many fading processes. Here we discuss methods not to reduce the variance of the fluctuations, but to mitigate the losses due to those fluctuations in signal processing. Our running example will be a system transmitting M-ary PPM with a rate R ECC and slot-width Ts. However, the approaches can be applied to any coded modulation.
Noise and Interference
Published in Michel Daoud Yacoub, Foundations of Mobile Radio Engineering, 2019
There are many types of additive noise, such as ambient, background, static, radio, etc. We are mainly interested in the radio-type noise, of which the most important are atmospheric noise, galactic noise, artificial (i.e., man-made) noise, and receiver noise. Multiplicative noise, which causes fading, is a peculiarity of mobile radio systems. The two types of fading that are commonly observed are long-term and short-term fading, which will be briefly reviewed for convenience.
State estimation and control for networked control systems in the presence of correlated packet drops
Published in International Journal of Systems Science, 2023
Ayyappadas Rajagopal, Shaikshavali Chitraganti
The above-mentioned literature that focuses on the packet drops or packet delay does not consider the cause of those delays or drops. For instance, a wireless channel can impose various types of impairments to the signals that are transmitted through it including noise, attenuation and fading, that may result in packet drops or delays. Of these impairments, fading is an important one, yet one that is not often considered. It is defined as random fluctuations in amplitude or phase of the signals that are transmitted through a channel. A detailed explanation of fading, its types and other relevant information can be seen in the literature (Chockalingam et al., 1998; Kumar et al., 2008; Simon & Alouini, 2001). Fading is imposed due to environmental or physical factors and can introduce a spatial or temporal correlation in the transmitted signals. This signal correlation can in turn result in correlated packet dropout owing to the fact that the channel condition remains constant for a particular amount of time known as coherence time. A specific number of packets experience similar amount of distortion during that time (Kumar et al., 2008). The amount of correlation may be arbitrarily selected for analysis, but the actual correlation of packets may be determined using an autocorrelation estimator (Torp et al., 1995). In Hmedi et al. (2022), the authors investigated on industrial networked control systems to ensure both stability and efficiency properties subject to shadow fading with correlated measurements. But they are not specifically considering correlated packet drops.
Performance of a multihop cognitive radio network with diversity under imperfect CSI
Published in International Journal of Electronics Letters, 2023
S. Mondal, D. Bepari, S. Biswas
Further, to extend the coverage area of the network, several works have been carried out on multihop relay network. In Guo et al. (2016), the authors investigates the outage probability of a cognitive multihop network under Nakagami-m fading channel. In Boddapati et al. (2016), instead of single relay, the authors have considered a cluster of multiple relays and analysed the performance of secondary network under peak interference constraint. Further, the outage probability of a multihop network is analysed for an underlay cognitive paradigm, and jointly optimised the transmit power and energy harvesting duration for minimising outage probability of secondary network (Xu et al., 2016). The closed form expressions for outage probability, bit error rate and ergodic capacity of a secondary network have been derived under the constraint of peak interference constraint over an non identically distributed Rayleigh faded channel (Bao et al., 2013b). A source transmitting data to destination over a single hop in presence of multiple primary transmitters Kalamkar and Banerjee (2015). Diversity technique is used to mitigate fading and shadowing effect in wireless communication. In Li (2012), the author has analysed impact of MRC diversity on the performance of CR network by considering multiple antennas at destination and a Rayleigh faded channel.
Effective capacity analysis of SIMO system with MRC and SC over Inverse-Gamma shadowing
Published in International Journal of Electronics, 2022
Vipin Kumar Upaddhyay, Puspraj Singh Chauhan, Sanjay Kumar Soni
Internet of things (IoT), underwater wireless communication, unmanned aerial vehicle air-to-ground (A2G) communication are most sought applications for both civil and military purposes in the present era of communication. These applications are more susceptible to dispersive and shadowing attenuation, which lead to the need of accurate estimation of fading depth to maintain continuous and reliable data link. Different techniques are utilised to improve system reliability by increasing the strength of the received signal. Diversity is one of the optimal techniques to suppress the effect of fading. Therefore, different diversity techniques are employed to improve the link reliability and quality of service (QoS), an essential requirement for any communication system. Open literature is flooded with physical layer performance analysis of the wireless communication systems employing various diversity techniques over a variety of fading environments ‘(Al-Hmood & Al-Raweshidy, 2016; Badarneh et al., 2018; Chauhan et al., 2019; Rana et al., 2017; Tiwari et al., 2017)’.