# A Multi-Node Detection Algorithm Based on Serial and Threshold in Intelligent Sensor Networks  
[PERSON]  
1 School of Electrical Engineering and Information, Northeast Petroleum University, Daqing 163318, China; [EMAIL_ADDRESS] (G.Z. ); [EMAIL_ADDRESS] (Z.G. ); [EMAIL_ADDRESS] (Q.Z.) [PERSON]  
1 School of Electrical Engineering and Information, Northeast Petroleum University, Daqing 163318, China; [EMAIL_ADDRESS] (G.Z. ); [EMAIL_ADDRESS] (Z.G. ); [EMAIL_ADDRESS] (Q.Z.) [PERSON]  
1 School of Electrical Engineering and Information, Northeast Petroleum University, Daqing 163318, China; [EMAIL_ADDRESS] (Z.G. ); [EMAIL_ADDRESS] (Q.Z.) [PERSON]  
1 School of Electrical Engineering and Information, Northeast Petroleum University, Daqing 163318, China; [EMAIL_ADDRESS] (G.Z. ); [EMAIL_ADDRESS] (Z.G. ); [EMAIL_ADDRESS] (Q.Z.) [PERSON]  
2 Communication Research Center, Harbin Institute of Technology, Harbin 150080, China; [EMAIL_ADDRESS] 2  
[PERSON]  
3 College of Information Engineering, Zhejiang University of Technology, Hangzhou 310014, China; [EMAIL_ADDRESS] 3  
Footnote 3: email: {hangjun.zhangj. large-scale antenna arrays, ultra-dense networks, millimeter wave communication, non-orthogonal multiple access and new network architecture, etc. [11; 12; 13; 14]. Therefore, it can well meet the needs of current communication networks and wireless sensor networks. Sparse code multiple access (SCMA) is a new multiple access technology of 5G [15]; it synthesizes the ideas of code division multiple access (CDMA) and orthogonal frequency division multiple access (OFDMA) [16], realizes the frequency domain non-orthogonal multiple access (NOMA) [17], and provides a reliable technical method for multiuser access and detection in 5G application. SCMA has the characteristics of large capacity, low delay, multi-connection and strong anti-multipath ability [18; 19; 20], which can better meet the needs of 5G for higher spectral efficiency [21; 22]. SCMA technology is an improvement over the basis of low density multiple access technology; its application greatly improves the performance of multi-user access and detection [23; 24]. In order to get the codebook, SCMA technology combines spread spectrum technology and constellation mapping technology to realize the operations of displacement, rotation and conjugation of high-dimensional constellation [25; 26; 27; 28; 29]. When the SCMA technology is used in IWSN, the following steps are adopted to realize the processing of the sensor nodes at the sending end: (i) The sparse spread spectrum sequences are assigned to every sensor node. (ii) The sparse spread spectrum technology is applied to sparse the data of sensor nodes. (iii) The data of all sensor nodes are mapped into an n-dimensional codebook through a multi-dimensional constellation, and then these data are superimposed on the same time-frequency resources of each transmission layer. (iv) These data are sent to the same channel for transmission. The sensor nodes can get better mapping gains with this scheme [30; 31]. At the receiving end, the message passing algorithm (MPA) decoder is used for multi-user detection, and then the received signal, mapping mode and channel coefficient are used to decode the signal. However, when the number of sensor nodes in SCMA system is much larger than the number of resource nodes, the complexity of the MPA algorithm will be very high. The application of 5G not only brings high-speed data transmission, but also promotes the development of multiple access and detection technology, such as the original MPA, the MPA based threshold (T-MPA) and the MPA based serial (S-MPA). However, the existing multi-node detection algorithm still cannot solve the problem of low transmission accuracy and high algorithm complexity in wireless sensor networks, so how to reduce the algorithm complexity and improve the message transmission accuracy is the key research objective in IWSN.