Joint Resource Allocation and Trajectory Optimization with QoS in UAV-based NOMA Wireless Networks
Abstract : Replacing base stations with unmanned aerial vehicles (UAVs) to serve the communication of ground users has attracted a lot of attention recently. In this paper, we study the joint resource allocation and UAV trajectory optimization for maximizing the total energy efficiency in UAV-based non-orthogonal multiple access (NOMA) downlink wireless networks with the quality of service (QoS) requirements. To handle the user scheduling problem, a heuristic algorithm based on matching and swapping theory is proposed first to allocate users that access UAV in each subperiod, then the transmit power allocation problem which considers the maximum transmit power and minimum user date rate is transformed to a convex optimization problem using logarithmic approximation. Meanwhile, the successive convex optimization is used in UAV trajectory optimization problem and a joint optimization algorithm is presented with the algorithm’s convergence and computational complexity. Finally, numerical results are provided to support the rationality of the proposed algorithm.
? This paper presents a user pairing and power allocation technique for energy efficient and quality of service (QoS) aware NOMA transmission for cellular-connected mobile UAVs.
? The research challenges discussed earlier, has motivated us to investigate cellular connected UAVs as mobile aerial users.
? Hence, unlike existing literature, this work exploits NOMA in the cellular-connected UAV network, where UAVs are considered as mobile NOMA users.
? Pairing and unpairing of all KT mobile UAVs at each time instant (t) during mobility is more complex and cumbersome at the BS; its complexity becomes too high.
? Due to the non-convexity of the formulated problem, it is decomposed into two subproblems and a joint resource allocation and trajectory design algorithm is proposed by alternative optimization.
? To tackle this issue, we decompose P1 into two subproblems and then propose an alternative optimization algorithm to solve the formulated problem.
? Due to the non-convexity of the formulated problem, we decompose it into two subproblems.
? Then, by leveraging the sequential convex approximation (SCA) technique, an alternative optimization algorithm is proposed to solve the formulated problem.
• An energy efficient trajectory optimization technique is proposed in for a mobile UAV considering the point-to-point wireless communication.
• While the proposed technique can be extended to mixed pairing between mobile aerial and ground users, such an approach is subject to our future research works.
• In the technique proposed in, the negotiation process between proposers and selectors for a suitable power allocation creates an extra overhead, especially when applied to mobile UAVs as in our case.
• In this paper, a fast convergence power optimization algorithm is proposed to find minimum optimal transmit powers of the mobile UAVs that guarantee the required target rate without performing the exhaustive search.
? The performance of the proposed UAV pairing is better than the conventional NOMA pairing techniques throughout the flight duration due to the power optimization performed before pairing.
? More importantly, the proposed algorithm yields better performance than the fixed bandwidth allocation scheme, since the flexible bandwidth allocation in our algorithm fully explores the diverse channel gains and can reduce the offloading energy consumption.
? High energy efficiency of the proposed UAV pairing technique with increasing difference shows its performance gain compared to the conventional fixed pairing techniques.
? Moreover, the performance comparison for large number of aerial users shows the performance gain of the proposed technique.
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