18,870 research outputs found
Cooperative wireless transmissions of dynamic power price and supply information for smart grid
No full textSpreading Factor Allocation for Massive Connectivity in LoRa Systems
No full textAlong with enhanced mobile broadband and ultra-reliable low latency communication, massive connectivity has been one of the key requirements for enabling technologies of 5G. For IoT, low power consumption and wide area coverage for end devices (ED) are important figures of merit, for which LoRa, SigFox and Narrow Band-IoT are dominant technologies. In this letter, we analyze LoRa systems for increasing average system packet success probability (PSP) under unslotted ALOHA random access protocol. The lower bound for average system PSP is derived by stochastic geometry. And it is shown that the average system PSP can be maximized by properly allocating spreading factor (SF) to each traffic, which also maximizes connectivity of EDs. We formulate an optimization problem for maximizing the average system PSP to propose a sub-optimal SF allocation scheme to each traffic. Analysis on PSP is validated through simulations, and comparison with existing schemes reveals that our proposed scheme achieves the highest PSP and so the maximum connectivity.
Joint Power and Time Allocation for Two-Way Cooperative NOMA
No full textIn this paper, we propose a two-way cooperative relay scheme based on non-orthogonal multiple access (NOMA) where bidirectional communication is supported for two users in three phases. We jointly optimize power and time allocations to minimize system outage probability whose exact closed-form expression is derived and verified by Monte Carlo simulations. For performance comparison, four schemes based on power allocation and time allocation as well as the conventional one-way cooperative NOMA (OW-CNOMA) scheme are provided. It is shown that the proposed scheme can improve outage probability and ergodic rate performances over a conventional OW-CNOMA system.
Multi-RAT Wireless Network Capacity Optimization under Optimal Spectrum Splitting in LTE-U
No full textEfficient utilization of limited spectrum resource has been a major issue in wireless communication systems, which has triggered the design and development of advanced cellular networks. Recently, heterogeneous network (HetNet) with small cells to satisfy the demand for higher data rate transmission and throughput has attracted a lot of attention in the unlicensed spectrum bands environment to overcome the scarcity of licensed spectrum. In this paper, we consider network capacity optimization problem for HetNet comprised of Long-Term Evolution (LTE) small cell and wireless fidelity (Wi-Fi) in LTE unlicensed spectrum (LTE-U) with optimal spectrum splitting ratio. We derive coverage probabilities and average achievable rates for each radio access technologies (RATs) based on the conditions of user equipment (UE) association in multi-RAT wireless network system. Then the optimal unlicensed spectrum splitting ratio can be obtained by maximizing HetNet capacity under the derived constraints on respective coverage probabilities. Simulation results reveal effectiveness of the proposed scheme, where both the spectrum splitting ratio and transmit power ratio are key parameters. This analysis can be easily extended to HetNets with multiple RATs
Optimal Resource Allocation for Packet Delay Minimization in Multi-Layer UAV Networks
No full textResearch and development of heterogeneous small cell in cellular network accommodates the proliferation of data-hungry devices and applications. Meanwhile, for challenges in providing high-data-rate transmission in poor coverage area, utilizing unmanned aerial vehicles (UAVs) provides a promising solution attracting tremendous attention. However, tight integration of UAVs creates an obstruction in existing network to acquire high efficient resource utilization, which needs investigation in 3D network architecture. In this letter, we propose a resource allocation optimization mechanism to minimize mean packet transmission delay in 3D cellular network with multi-layer UAVs. Numerical results demonstrate effectiveness of the proposed algorithm, where optimal spectrum and power allocation can provide minimum packet transmission delay.
An opportunistic channel quality feedback scheme for proportional fair scheduling
No full textIn this paper, we propose a channel quality information (CQI) feedback load reduction scheme for proportional fair scheduling (PFS) in wireless systems. The proposed scheme induces select users to feed back CQI only when the probability of selection is high. It is shown that the proposed scheme achieves system throughput comparable to the conventional scheme, where each and every user feeds back its CQIs, with significant feedback load reduction for each of the users
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