## 1 Introduction
By extracting the geographic location of the colliding packet signals, the K-means clustering algorithm is used to cluster the adjacent access points of the colliding terminal based on the shortest distance. According to the feature of large-scale fading, the packet signal in the access point of the adjacent cluster of the colliding IoT is stronger, while the power of the interfering packet signals in this cluster may be weaker due to long distance, so that the power difference between the packet signal of this collided terminal and the interfering terminal can be used to demodulate the collided packet. In practice, however, the large number of IoT terminals will allow for a wide variety of collisions so that packet collisions may be generated by adjacent terminals. Based on large-scale fading only is insufficient to solve the performance problems caused by collisions, and on the other hand, a strictly synchronous regime is difficult to implement in the IoT system. The literature [23] proposes a cooperative beamforming ALOHA scheme (CBA) based on LEO, but this scheme only considers the cooperation scenario of dual satellites. In the future, it will be possible for multi-satellite co-view in the giant LEO constellation. We find that for the demodulation of desired signals, the cooperation performance of LEO satellites with poor channel quality will be reduced. In this paper, we consider a network composed of IoT terminals, LEO satellites and ground gateway stations. Adjacent satellites collaborate to address the problem of collision in uplink transmission packets within the common coverage area at the gateway station. Due to the large number of LEO satellites in the co-visibility area, an optimized selection is made for participating satellites to maximize collaboration gain and reduce system power consumption. An SC-ACRDA scheme is proposed that maximizes throughput by addressing packet collision avalanche problems in LEO IoT uplink transmissions. The main contributions of this paper are as follows:  
* When the signal transmitted by satellite is subjected to beamforming processing by the gateway station, the participation of some channel nodes with poor channel quality in collaboration processing will reduce system performance. To address this issue, we proposed a collaborative multi-satellite selection algorithm based on maximum SINR. The algorithm solves the satellite selection problem in multi-satellite cooperative beamforming by constructing and solving a non-convex optimization problem. In order to make the optimization problem solvable, we use the Charnes-Cooper transformation to convert the non-convex problem into a convex optimization problem with optimization parameters. The optimized parameter determines the number of satellites selected. For the selection of optimized parameters, we design an iterative binary search algorithm to obtain optimal values;
* Regarding the problem of packet collision caused by the massive concurrent access of IoT terminals in LEO IoT network traffic surge. Under the ACRDA retransmission mechanism, an asynchronous collision-tolerant ACRDA scheme based on satellite-selection collaboration-beamforming is proposed by combining the proposed algorithm and SIC technology. The collided packets can be successfully demodulatedthrough the power difference generated by the collaborative multi-satellite selection algorithm based on the maximum SINR algorithm. The demodulated packets can be reused for SIC. Simulation results show that the proposed scheme effectively solves the deadlock problem of packet collision under medium to high loads and improves system throughput. The rest of this paper is organized as follows. Section 2 describes the system model. In order to solve the multi-satellite selection problem, the corresponding algorithm is designed in Section 3. In Section 4, the SC-ACRDA scheme is designed, and its performance is deduced. In Section 5, simulations and analysis are presented. Section 6 concludes this paper.