Visible Light Communication (VLC) has emerged as a promising technology for high-speed wireless communication, which employs the visible spectrum to transmit information. As the title indicates, IEEE 802.15.7 is a new standard dedicated to VLC networks that introduces specializations that match the characteristics and needs of this medium. In VLC networks, one of the key challenges is scheduling Guaranteed Time Slots (GTS) efficiently for better network performance and minimum end-to-end delay while delivering reliable data. The aim of this review paper is to give a detailed overview of the state-of-the-art, in terms of different types GTS allocation strategies within IEEE 802.15.5 network by performing an exhaustive analysis and discussion on each broad category. We investigate, at first, the basic concepts of GTS allocation and then how it plays an important role in increasing the Quality of Service (QoS) level for various VLC applications. In our paper, we explore current GTS allocation methods and evaluate their effectiveness in dynamic network conditions based on how scalable and adaptive they are. In addition, we study how different network parameters like throughput delay and energy consumption are affected by the choice of allocation. Challenges and limitations in practical implementations, such as interference management, mobility support, and synchronization issues are discussed. Besides, we also focus on some more advanced algorithms and optimal solutions that have been suggested to overcome these issues in order to improve the overall performance of VLC networks. This paper consolidates the recent advances and ongoing research in this area, to serve as a useful source of information for researchers/practitioners interested in designing effective GTS allocation mechanisms over IEEE 802.15.7 based VLC networks that are both reliable, and energy efficient. This study then offers some future research directions, including how to use machine learning techniques in an integrated manner and realize cross-layer optimization for better efficiency and adaptability on GTS allocation over VLC-based networks.