To meet stringent service requirements in 5G at reasonable CapEx/OpEx, multi radio unit (RU) joint transmission has gained great attention. Optimal precoding design is a main concern in multi-RU joint transmission. In...
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To meet stringent service requirements in 5G at reasonable CapEx/OpEx, multi radio unit (RU) joint transmission has gained great attention. Optimal precoding design is a main concern in multi-RU joint transmission. In this paper, a new multi-RU joint precoding scheme is newly designed for sum-r ate-maximization with a minimumrate guarantee constraint under imperfect channel estimation. Owing to non-convexity of minimumrate guarantee constraints which causes huge computational complexity, we decouple the non-convex rate guarantee constraint into two convex constraints;desired signal constraint and interference constraint. And then, we propose a computationally efficient algorithm to find the suboptimal solution by iteratively solving two convex suboptimization problems. Through intensive simulations, the performance of the proposed scheme is evaluated and found to be superior compared with two previous schemes as well as the small-cell base station (SBS) transmission scheme.
Cognitive radios emerged as a solution to spectrum scarcity problem. The integration of cognitive radios and wireless sensor networks enables a new paradigm of communication, in which the sensor nodes can avoid heavil...
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Cognitive radios emerged as a solution to spectrum scarcity problem. The integration of cognitive radios and wireless sensor networks enables a new paradigm of communication, in which the sensor nodes can avoid heavily-crowded transmission bands by tuning their transmission parameters to less-crowded bands. The authors consider the problem of spectrum assignment for cognitive radio sensor network (CRSN) under coverage, interference, minimumdatarate and power budget constraints. A mixed-integer non-linear programming problem formulation that addresses optimal power allocation, channel selection and node scheduling is presented. Following a practical assumption, that any CRSN node can only access one channel for its transmission with the CRSN base station, the problem is transformed to a binary linear programming (BLP) problem. Using the relaxation techniques, the problem is transformed to a linear programming problem that is solvable in polynomial time, and has the same optimal solution of the BLP problem. Hence, the minimum power algorithm that achieves the optimal solution of our problem is proposed. To further reduce the complexity of the solution, three heuristic lower-complexity algorithms are proposed to solve the problem: random, greedy and two-stage (decoupled) algorithms.
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