Research On Feedback And Resource Configuration For 5G Air Interface

With the ever-increasing demand for wireless data traffic and data rate,the improvement of network capacity has become the major challenge for network operators.In order to meet the exploding user communication requirement,and solve the problem of scarcity of spectrum resource and low utilization ratio of spectrum resource,5G air interface technology has become one of the research hotspots in the field of wireless communications.This thesis researches issues about power allocation optimization for non-orthogonal multiple access systems,UL non-orthogonal multiple access in mMTC,and UL non-orthogonal multiple access in unlicensed band.The main research contents are as follows:For the issue about power allocation optimization for non-orthogonal multiple access systems,uplink and downlink are discussed respectively.Firstly,the sum-throughput maximization problem is formulated as a convex optimization problem under the constraints of the total transmission power within a non-orthogonal multiple access group and the minimum rate requirements of the users.Then,the closed-form solution of the optimal power allocation is derived using the KKT condition.At last,the numerical results show that compared with orthogonal multiple access system,the sum-throughput performance of non-orthogonal multiple access system with the proposed power allocation scheme has significant improvement,and could adapt to more various channel conditions and users' data rate requirements.For the issue about UL non-orthogonal multiple access in mMTC,a scheme of group feedback is proposed,which combines many users'ACK/NACK feedbacks into one packet so as to reduce the overhead for downlink caused by a large amount of ACK/NACK feedbacks.Then,a scheme of semi-statically nonhomogeneous frequency-domain resource grouping is proposed,with the group index of the resource used for the transmission of an UL data packet corresponding to its transmission number,thus we solve the problem that BS cannot identify the transmission number of a received UL data packet for UL grant-free transmission.In addition,a kind of subcarrier allocation algorithm is designed,in order to maximize the spectral efficiency under the limitation on the number of users on each subcarrier.For the issue about UL non-orthogonal multiple access in unlicensed band,propose a basic idea that the first UE of cellular system that occupies a certain sub-channel in unlicensed band broadcasts information on that sub-channel to other UEs of cellular system.Based on this idea,two feasible schemes are further designed to realize UL non-orthogonal multiple access in unlicensed band.