Low Earth Orbit (LEO) satellite network is a cost-efficient way to achieve global covering for wide-area Internet of Things (IoT). As more and more IoT applications require large amounts of computing resources, cloud computing paradigm becomes one of the IoT's main enablers. Abundant resources can be used to execute computation-intensive IoT applications in the cloud. Moreover, edge computing has emerged to alleviate the high latency and low bandwidth problem of cloud computing. The integration of edge computing into LEO networks (which is called LEC in this paper) can improve satellite IoT network's performance. In addition, it is an effective way to support delay-sensitive and resourcehungry wide-area IoT applications. However, there are many technical challenges for LEC, which is different from edge computing in terrestrial networks. Therefore, we study LEC in depth and a novel system architecture is proposed. A LEC prototype system is implemented which verifies our design. The simulation result demonstrates that LEC can improve system performance compared with cloud computing in LEO networks.

No abstract

Power domain non-orthogonal multiple access (PD-NOMA) has been widely recognized a spectrum-efficient multiuser transmission method when the channel gains across different users vary obviously. Due to the long travel distance between the space and the Earth in satellite communication scenarios, the advantages from PD-NOMA will disappear since the signals experience almost the same path loss. However, in hybrid satellite networks, terrestrial users equipped with different size antennas may lead to various receiving gains, which are equivalent to diverse channel gains. In this paper, by deeply exploiting such a characteristic, we propose a power domain multiplexing based co-carrier transmission method in a hybrid satellite network. Superposing a weak signal on a strong one, two signals are enabled to be transmitted on the same carrier with the bandwidth of the strong signal. To guarantee the signals are decodable at both sides, a user pairing strategy is investigated in detail, and the performance gain of the new method is further analyzed. Simulation results show that a carrier resource can be saved in the proposed method with the sacrifice of a marginal bit-error-rate performance. INDEX TERMS Bit-error-rate, co-carrier transmission, hybrid satellite networks, power domain multiplexing.

No abstract

Satellite communication networks have gradually been recognized as an effective way to enhance the ground-based wireless communication. Considering the weight restriction of payloads, multi-antenna technologies have recently come into use on satellite platforms, and are capable of generating beams flexibly to provide services. To avoid incurring interferences, adjacent beams are designed to take different spectral resources. Unfortunately, this may limit the simultaneously accessed terminals since the spectrum cannot be fully used. In this paper, we propose a spectrum-saving transmission method in a satellite star network, where terminals communicate with each other through the hub station. Taking advantage of the great transmission capability differences of the hub station and terminals, we could allocate them the same spectral resources. Specifically, it is not necessary to use exclusive frequency bands for terminals.The proposed method can play a significant role when large numbers of users need to access the system with limited spectrum resource. To give a deep insight into the spectrum-saving method, the expressions of ergodic sum-rate are provided, and the impact of the number of accessed terminals is further analyzed. Simulation results validate the advantage of the proposed method in terms of bit error rate and ergodic sum rate.