## 1 Introduction  
Due to the limitation of infrastructure construction, the traditional terrestrial mobile network cannot cover some areas, such as remote and non-land regions and stricken areas. The satellite communication system has the advantage of not being limited by geographical environment, so it is an effective solution to provide global coverage. The Geostationary Earth Orbit (GEO) satellites are located 35,786 km above the equator line and move synchronously with the Earth [1]. A GEO satellite covers almost one-third of the Earth's surface [2] (excluding polar regions). Low Earth Orbit (LEO) satellites are generally located at an altitude between 300-1500 km [1]. Due to the altitude, the inevitable propagation delay of GEO satellite cannot meet the requirements of delay-sensitive services [3]. The rapid movement of LEO satellites causes frequent handovers. When users are about to leave the coverage of one LEO satellite, they need to switch to another satellite to avoid communication termination [4]. Moreover, a single LEO satellite covers a small area, and some regions cannot be covered by LEO satellites when the size of the LEO constellation is small. Subject to issues such as funding and technology, not every country and every institution can provide a large enough LEO constellation. Using small-scale LEO constellations combined with GEO satellites is a feasible and more economical solution. The integration of GEO satellites and LEO satellites can also maximize their respective technological advantages to meet the demands of different types of services. Users need to consider the decision making of handover when they use the GEO/LEO heterogeneous network to communicate. The handover decision is the core stage of the handover process, which requires determining the satellite next connected. The newly generated services also need to select the access satellite at the beginning of communication. In order to guarantee user requirements and network load balancing, a rational and practical access and handover decision strategy needs to be proposed to further improve the performance of GEO/LEO heterogeneous satellite systems. The key point of access and handover decision under multi-satellite coverage is selecting the access point for new calls and handover calls. The decision methods of handover for heterogeneous networks generally include the decision function approach (including simple decision functions [5] and MADM [6]) and the decisions based on complex mathematical models. In [5], authors use the instantaneous received signal strength (RSS) and the average RSS of user equipment to determine the necessity of handover. The simple decision function strategy is easy to implement but does not take full advantage of the information available. The MADM method can effectively and flexibly deal with complex problems [7], so it is often used in heterogeneous networks selection. The Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method is one of the MADM methods with good performance and wide application. Some researchers also use complex mathematical models to design handover decisions, such as strategies based on the Markov decision process [8], the potential game [9], the graph theory [10], etc. Soft sets, rough sets, and fuzzy sets can also be used in decision making [11]; [PERSON] et al. introduce the novel concept of the linear Diophantine fuzzy set (LDFS) to help the multi-attributes decision making [12]. These model-based methods are highly accurate, but computationally complex, and have high requirements on the computing power or storage capacity of the device. Considering the limitation of equipment capability, we use TOPSIS to design an access and handover strategy, which can better solve the goal of users to make handover decisions independently. In this paper, we propose a new strategy to solve the access and handover problems of GEO/LEO heterogeneous satellite networks. The strategy we proposed consists of two steps.