Auction-Based Secondary Relay Selection on Overlay Spectrum Sharing in Hybrid Satellite-Terrestrial Sensor Networks  
[PERSON]  
1 College of Communications Engineering, Army Engineering University, Nanjing 210007, China; [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (B.Z. ); [EMAIL_ADDRESS] (Z.C. );  
2  
[PERSON]  
1 College of Communications Engineering, Army Engineering University, Nanjing 210007, China; [EMAIL_ADDRESS] (X.Z. ); [EMAIL_ADDRESS] (B.Z. ); [EMAIL_ADDRESS] (Z.C. );  
2  
[PERSON]  
However, satellite sensor links mainly depend on the line-of-sight (LOS), which are vulnerable to be blocked by heavy shadowing or obstacles, such as buildings, bushes, etc., [13]. Besides, the unique features, such as low energy consumption, spectrum scarcity and implementation cost, limit the wide scope of usage. Fortunately, the quality of services (QoS) about terrestrial wireless sensor nodes can be augmented with the development of the relay within seamless connectivity and broadband access to mobile users [14]. To enhance coverage area and obtain highly reliable data rate services for satellite sensor networks, deployments of terrestrial relays in hybrid satellite-terrestrial sensor networks (HSTSNs) are proposed [15; 16; 17; 18; 19; 20; 21]. Various works have analyzed the performance of the HSTSNs by using the decode-and-forward (DF) and amplify-and-forward (AF) relay protocols [22; 23; 24]. On the other hand, the terrestrial networks are suffering from the spectrum scarcity. One of the available solutions is the cognitive radio (CR) in the hybrid framework, including interweave, underlay and overlay paradigm [25; 26; 27]. Inspired by the combination of CR and HSTSNs, the author in [28] firstly proposed the overlay paradigm in hybrid satellite-terrestrial networks (HSTNs), in which the secondary terrestrial users assist the primary satellite transmission through cooperative relaying techniques in exchange for spectrum access. Besides, the relay selection scheme is based on globe channel state information (CSI) from the perspective of the statistical channel model, where overheads include a huge time delay and the calculated amount for the onboard processing satellite or ground network control center (NCC). To further increase the system capacity, the author in [29] combined non-orthogonal multiple access (NOMA) and the overlay paradigm HSTNs. The works in [30; 31] investigated the overlay paradigm into the holistic 5G system. However, those two works mainly focus on the terrestrial network, which is unable to apply in the HSTNs directly. In this paper, we investigate the Vickery auction-based secondary relay selection for cooperative overlay spectrum sharing in HSTSNs. Especially, the potential relay would be the base-stations (BS) of the 5G, device-to-device (D2D) nodes or other ad-hoc networks, which are capable of applying the unlicensed frequency band. The main contributions of this paper are summarized as follows:  
* First of all, we analyze both the DF and AF relay protocols on the spectrum sharing mechanism for primary user's (PU's) message in HSTSNs. In addition, the advantages and disadvantages of the traditional relay selection algorithm are also analyzed. * Then, the Vickery auction mechanism is introduced to achieve the efficient and fairness secondary relay selection by one shot in a distributed manner, where the bids of the potential relay are the assistance transmission capacity by the different sub-time slot allocation in the entire time slot. * Numerical simulations are provided to compare the proposed auction-based algorithm with the maximum satellite-relay and relay-destination link and maximum satellite-relay link, which validate the effectiveness of the auction mechanism on cooperative spectrum sharing in HSTSNs for secondary relay selection. Besides, the effects of key factors on the performance of the auction mechanism are analyzed. The rest of this paper is organized as follows. Some related work is introduced in the Section 2.