Department of Electrical and Electronics Engineering

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    Indoor Propagation Effects in D2D Communication: 5G Applications and Coverage Analysis
    (IEEE, 2021) Joshi, Sandeep
    We study a practical simulation set-up of indoor device-to-device (D2D) communications scenario for fifth generation (5G) applications to analyse the effects of power level variations, path-loss, and the impact of transmission through direct and indirect communication links. We provide a simulation based analysis considering a generalized indoor office building for the context of D2D indoor communication with line-of-sight and non-line-of-sight communication links. We show the effect of power level on the transmission, variation of the connectivity probability with the change in the number of receivers, and also consider the impact on connectivity of modeling the network as a mesh where the users act as relays. The simulation is performed at different operating frequencies including the 5G frequency range and for different path loss functions. We present the coverage analysis by taking actual measurements for an office setup, validating it through simulations, and show that the network coverage extends with the D2D communications. Furthermore, we observe that, as the number of users increases, the number of users able to access the network also increases, but with D2D communication included, that number approaches between 80% and 100% at 2.4 GHz, or around 50% to 90% at 5.8 GHz, in the presented scenario.
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    Optimal Coverage Analysis of a Cellular Device-to-Device Communication Network
    (IEEE, 2020) Joshi, Sandeep
    This paper considers a device-to-device (D2D) cellular communication network with the wireless communication link among the devices and the base station (BS) modeled by the Rician fading and the wireless communication link between the devices modeled by Nakagami-m fading distribution. The devices and the BSs are assumed to be placed randomly as independent Poisson point processes with the devices experiencing interference from both D2D users and the cellular users. Using the techniques of stochastic geometry, series form expressions of the coverage probability of the cellular users are derived for the underlying interference-limited D2D cellular network. Furthermore, the optimal coverage values that maximize the energy efficiency of the network are also obtained analytically. The effect of the Rician factor and other system parameters on the performance of the system is studied by numerical results. The study of the variations of the optimal coverage analysis with the system parameters presented in this paper gives an insight into the design of cellular D2D communication networks.
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    Cooperative Device-to-Device Relaying Network with Power Line Communications
    (IEEE, 2019) Joshi, Sandeep
    Cooperative device-to-device communication with non- orthogonal multiple access (NOMA) employing additional power line communication technology is an effective way to increase the coverage and spectral efficiency of the next generation hybrid networks. In this paper, we present the outage analysis of a cooperative network with NOMA and decode-and-forward relaying assuming a direct link between the base station and the users. We consider a relaying network consisting of a wireless link for the strong user and the weak user having both wireless and a wired link which is assumed as a power line link. The wireless links are subjected to Nakagami-m fading and the power line link experiences Rayleigh fading. The outage probability expressions for both the strong and the weak users are derived assuming power division NOMA and perfect successive interference cancellation at the receivers. We also derive the optimal value of the NOMA power allocation coefficient minimizing the outage probability at the strong user and obtain the range of the power allocation coefficient between the power line and the wireless link at the weak user. Furthermore, numerical results validate the derived analytical results.
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    Cooperative NOMA with AF Relaying over Nakagami-m Fading in a D2D Network
    (IEEE, 2019) Joshi, Pankaj
    Cooperative non-orthogonal multiple access (NOMA) scheme is emerging as an important part of the next generation wireless systems. Recently, device-to-device (D2D) networks with NOMA have received considerable attention by the researchers due to the advantages offered by them. D2D communication involves direct contact between the devices in proximity and the devices can also be used as relays for cooperative communication. In this paper, we present the performance analysis of a downlink cooperative D2D network with NOMA and amplify-and-forward (AF) relaying with fixed gain assuming that the D2D communication links experience independent Nakagami-m fading. We derive closed-form expressions for the outage probability of strong and weak D2D users with the assumption that there exists a direct communication link between the base station and the D2D users. Further, we also present the system throughput and the asymptotic outage analysis for both strong D2D user and weak D2D user. As a special case, we also provide the outage expressions for both strong D2D user and weak D2D user when the D2D communication links experience Rayleigh fading. Furthermore, numerical results are in agreement with the derived analytical expressions.
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    Performance analysis of a cooperative D2D communication network with NOMA
    (IET, 2020-09) Joshi, Sandeep
    The cooperative device-to-device (D2D) network employing non-orthogonal multiple access (NOMA) is expected to play an important role in the next-generation wireless networks. In this work, the authors derive outage probability expressions of a cooperative NOMA D2D network which employs decode-and-forward relaying. A wireless link experiencing Nakagami-m fading is considered which is further assisted in the communication network by a wired link which is a powerline communication link and experiences Rayleigh fading. The outage analysis, shown for both the strong user and the weak user, is derived assuming that at the receiver there is perfect successive interference cancellation. Employing power division NOMA, optimum value for the coefficient of power allocation is obtained corresponding to the minimum probability of outage of the strong user. Furthermore, a range of the NOMA power allocation coefficient is provided for the communication link at the weak user which is between the wireless and the powerline link. Symbol error probability expressions are also derived for the strong and the weak users for the scenario when: i) both the wireless and the wired links are available for communication and ii) only the wireless link is available for communication.
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    Energy Consumption Performance of Opportunistic Device-to-Device Relaying Under Log-Normal Shadowing
    (IEEE, 2021-12) Zafaruddin, S.M.
    Efficient transmission protocols are required to minimize the energy consumption of mobile devices for ubiquitous connectivity in the next-generation of wireless networks. In this article, we analyze the energy consumption performance of a two-hop opportunistic device-select relaying (ODSR) scheme, where a device can either transmit data directly to a base station (BS) or relay the data to a nearby device, which forwards the data to the BS. We select a single device opportunistically from a device-to-device (D2D) network based on the energy required for transmission, including the energy consumed in the circuitry of the devices. By considering the log-normal shadowing as the dominant factor between devices and the BS, and Rayleigh fading in D2D links, we derive analytical bounds and scaling laws on average energy consumption. The derived analytical expressions show that the energy consumption of the ODSR decreases logarithmically with an increase in the number of devices, and achieves near-optimal performance only with a few nearby devices. This is an important design criterion to reduce latency and overhead energy consumption in a relay-assisted large-scale network. We also demonstrate the performance of the ODSR using simulations in realistic scenarios of a wireless network.