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We present an analytical characterization of the spectral efficiency achievable by D2D communication links overlaid on a cellular network. The analysis relies on a stochastic geometry formulation with a novel approach to the modeling and spatial averaging of interference, which facilitates obtaining compact expressions. These expressions are then a...
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... As the optimal values of the Lagrange-variables satisfy λ i = q i si ∀i, it is only necessary to update q. Using the formulation in (27), this results in the update formula Assign resulting rates to i * mn ∀(m, n) 19: end for where x ∈ N + is the iteration and θ > 0 is a fixed step-size. ...
Networked control system (NCS) refer to a set of control loops that are closed over a communication network. In this article, the joint operation of control and networking for NCS is investigated wherein the network serves the sensor-to-controller communication links for multiple stochastic linear time-invariant (LTI) sub-systems. The sensors sample packets based on the observed plant state, which they send over a shared multi-hop network. The network has limited communication resources, which need to be assigned to competing links to support proper control loop operation. In this set-up, we formulate an optimization problem to minimize the weighted-sum linear-quadratic-Gaussian (LQG) cost of all loops, taking into account the admissible sampling, control, congestion control and scheduling policies. Under some mild assumptions on the sampling frequencies of the control loops and the communication network, we find the joint optimal solution to be given by a certainty equivalence control with threshold-based sampling policy, as well as a back-pressure type scheduler with a simple pass-through congestion control. The interface between network and control loops is identified to be the buffer state of the sensor node, which can be interpreted as network price for sampling a packet from control perspective. We validate our theoretical claims by simulating NCSs comprising of multiple LTI stochastic control loops communicating over a two-hop cellular network.
... In the other words, the aim is to minimize the outage probability "The probability that the received Signal to Interference plus Noise Ratio (SINR) is less than the threshold" [8] and to maximize throughput "a nonlinear objective function on SINR". Previous studies [4,[8][9][10][11][12] presented only the approximate equations for outage probability in underlay and overlay scenarios, but exact equations have not been reported in these studies. In this paper, the exact formulas for both outage probability and throughput in underlay and overlay scenarios are extracted in the case of Additive White Gaussian Noise (AWGN) and multipath Rayleigh fading channel. ...
... Since overlaying scenario is interferencefree, SINR equals to Signal to Noise Ratio (SNR). It means that SINR is as (2) [9]: ...
... D EVICE to device (D2D) communication has recently evolved as an emerging research area, for its capability to improve spectral efficiency by re-using spectral resources intensively [1], offloading traffic from the base station [2], and providing local area services [3]. D2D communication enables direct peer to peer connectivity and supports higher data rates, both of which are highly desirable features for long term evolution-advanced (LTE-A) networks. ...
... In underlay D2D communication, the D2D users opportunistically access the time/frequency resources occupied by the cellular users [2], [6]. On the other hand, in overlay D2D communication, the D2D users use orthogonal time/frequency resources in such a way that the spectrum is optimally allocated to the D2D and cellular users [1], [6], [7]. In this paper, we consider overlay D2D communication assuming that optimal spectrum allocation has been performed between the cellular and D2D users. ...
... Recent studies on overlay D2D communication have primarily focused on the characterization of different performance metrics such as the spectral efficiency of overlaid D2D networks [1] and outage probability [8]. A spectrum sharing scheme is investigated in [7] where D2D users relay the communication from the base station to the cellular user while performing bidirectional communication with their D2D pairs. ...
In this paper, we consider device to device (D2D) communication overlaying cellular network where a group of D2D users exchange messages among themselves. We investigate the case when the channel conditions of the direct links among these D2D users are not strong enough to support direct communication and hence, an intermediate relay node assists the communication among the D2D users. Here we consider capacity achieving lattice codes at the D2D users along with compute-and-forward protocol at the relay. Based on these, we derive the received SNR at the relay, as well as the D2D users and formulate upper bounds on the achievable
sum rate. We also investigate the achievable sum rate when the devices communicate using the direct links and compare with that of the relay aided D2D communication. We find that when the D2D users are closer to the relay, relay aided communication achieves better performance compared to direct communication. However, for the same distances, the sum rate degrades more for relay aided communication. It is also shown that when the links between most of the D2D users and the relay have good channel conditions compared
to the direct links, relay aided communication can achieve better sum rate performance than the direct communication.
It is essential for Nordic and Baltic SMEs to understand the critical success factors (CSFs) of enterprise resource planning (ERP) implementations which we argue determine whether their cross-border cooperation will be successful or not. Hence, this research aims to expand our understanding of the CSFs of ERP implementations in the context of Nordic and Baltic SMEs. Via an explorative survey among Nordic and Baltic companies, our results suggest that the CSFs in the pre-implementation stage are more related to preparations and planning tasks, such as identifying goals and objectives, preparing and identifying resources to support the systems’ adoptions, and, gaining support from all related parties. During the implementation stage, CSFs focus on project management activities in which companies will use the outputs from the pre-implementation stage as inputs to finalize the ERP implementation. Accordingly, the post-implementation stage emphasizes the importance of end users. Hence, we provide our results to aid organizations in their future ERP projects. Finally, we provide our recommendations for future research.
One of the key strategies for increasing throughput and optimum resource allocation in 5G communications is Device to Device (D2D) communications which can be obtained by minimizing the outage probability. In order to minimize the outage probability, it should be modeled by considering the effect of interference, noise and multipath phenomena in a joint state. In this paper, by considering the statistical models of Additive White Gaussian Noise (AWGN) and Rayleigh multipath fading in two scenarios, the exact formulas for outage probability of a D2D communications underlying cellular network is proposed. In the first scenario, each D2D pair is allowed to reuse radio resource of one cellular user whereas in the second scenario, resources of two cellular users can be reused. The proposed formulas are compared to the approximate (non-exact) ones. The comparative study for the first and second scenarios show that the non-exact formula and the proposed exact one are in accordance with simulation results in MATLAB. As a remarkable result, based on Non Orthogonal Multiple Access (NOMA) approach, two approximations for the non-exact and the proposed formulas are extracted which are acceptable for multiple resource reuse scenario. Finally, simulation results show that multiple reuse scenario offers higher throughput in an acceptable outage probability compared to one reuse scenario when the distance between the D2D pair and respected cellular user is more than 71m.
This chapter proposes the device&;#x02010;to&;#x02010;device (D2D) communication paradigm to better utilize the spectrum. The energy&;#x02010;efficient resource allocation problem in D2D systems for energy proportionality is considered as a case study for the application of the outlined sequential fractional programming algorithms. The chapter considers the downlink of an orthogonal frequency&;#x02010;division multiple&;#x02010;access (OFDMA) cellular network, where infrastructure&;#x02010;to&;#x02010;device (I2D) and D2D communications coexist and are coordinated. The resource allocation policy that will be derived aims at maximizing the global energy efficiency (GEE) of the coordinated I2D and D2D links. The chapter contains a description of the system model and the received signal model for the case of a D2D&;#x02010;enabled cellular system. It presents the two key performance measures namely the GEE and the weighted sum&;#x02010;rate (WSR). The chapter focuses back on the case study and presents the application of sequential fractional programming algorithms to the problem of resource allocation for a 5G cellular system with D2D communications.
Device-to-device (D2D) communication allows serving local wireless traffic bypassing the system's infrastructure. One way to control the interference in D2D networks is to carefully channelize transmissions. This paper presents an analytical characterization of ITLinQ, one of the principal D2D channelization schemes proposed to date. Recognizing that it captures well the spatial characteristics of D2D networks, a stochastic geometry setting is utilized for this analysis. The derived expressions enable gleaning insights on how ITLinQ avoids situations of excessive interference, and they facilitate optimizing the controllable parameters of ITLinQ so as to maximize the system spectral efficiency (bits/s/Hz per unit area). With the parameters thus optimized, the ultimate performance of ITLinQ can be evaluated with respect to other D2D channel allocation schemes. In particular, performance evaluation comparisons with the FlashLinQ scheme are provided, and the gains with respect to an unchannelized network are quantified.
This paper addresses the benefits of introducing exclusion regions around both transmitters and receivers in D2D wireless networks. Such exclusion regions offer protection from interference at the expense of a sparser spatial reuse of spectrum, bringing about a tradeoff whose resolution entails optimizing the size of the exclusion regions as function of relevant system parameters. Our figure of merit for this optimization is the spectral efficiency. We first characterize this quantity for a given size of the exclusion regions, and then proceed to its optimization, altogether establishing the major benefits of incorporating properly sized exclusion regions in the applicable scheduling algorithms.
