Prototype Filter Designs for Maximizing Spectral Efficiency in Generalized Frequency Division Multiplexing Systems

• Main Authors: Lucien Bernard, 貝律祥
• Other Authors: Borching Su
• Format: Others
• Language: en_US
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/fqr88k

碩士 === 國立臺灣大學 === 電信工程學研究所 === 106 === Generalized frequency division multiplexing (GFDM) is a recent block filtered multicarrier modulation scheme featuring low out-of-band (OOB) radiation and low latency. By using a matrix-based characterization of GFDM transmitter matrices, opposed to traditional vector-based characterization with prototype filters, and deriving properties of GFDM (transmitter) matrices, one can design prototype filters that are found to correspond to the use of unitary GFDM matrices many scenarios, while avoiding the problem of noise enhancement, thereby showing the same MSE performance as orthogonal frequency division multiplexing (OFDM). In this thesis, a new problem related to bandwidth efficiency, and especially for OOB part, has been formulated in order to manage and design the number of used subcarriers and used subsymbols, so that the spectral efficiency can be maximized, regarding specifications needed by the prototype filters designers. A previous work introducing a filter optimization algorithm, originally introduced as a non-convex problem, tackled to an algorithm of two convex problems, that minimizes OOB radiation while maintaining good in-band performance is developed for GFDM is used in order to solve this problem, knowing that the spectral efficiency will be a main constraint. Since the main problem is about a maximization of sets of used subcarriers and used subsymbols, the resolution technique is however not well developed in the literature, while it is a known encountered problem. From that point on, the thesis proposes three methods to address this problem. The first introduces a raw force calculation, improved by a stopping criterion, knowing the non-decreasing nature of the function put into play under constraint. The two others methods propose an advanced algorithmic calculation in order to speed up the resolution of the maximization problem, by comparing the values already calculated, and knowing before the next calculation, which solution can potentially be better. The different simulations results show that the designer can choose a method and this number of subcarriers and subsymbols so that to treat the number of users, for the proper utilization of this characteristic GFDM system.