# A Multi-Node Detection Algorithm Based on Serial and Threshold in Intelligent Sensor Networks
In reference [32], a direct sequence code division multiple access (DS-CDMA) based communication system is proposed, which becomes the wireless interface of an integrated sensor micro system and improves the limitation of power and area in the communication system of a miniaturized sensor network. In reference [33], a heuristic CDMA multiuser detection scheme based on the harmony search (HS) algorithm is proposed. The multi-user detection scheme based on the harmony search (HS) algorithm reduces the complexity of the algorithm by searching a group of nearly optimal candidate vectors, but it still has high algorithm complexity and bit error ratio (BER). In reference [34], a threshold based MPA algorithm is proposed, which uses a threshold to control the algorithm, so as to reduce the complexity of the detection algorithm. An MPA algorithm based on a serial strategy is proposed in [35]. In reference [36], an improved serial scheduling based MPA (ISS-MPA) detection scheme is proposed. The maximum number of new message updating in the corresponding factor graph is used to select the scheduling order of user nodes, so as to maintain good BER performance and reduce the complexity of the detection algorithm. Although the above algorithms have obvious changes in the algorithm complexity and transmission accuracy compared with the traditional multi-node passing algorithm, the disadvantages of high algorithm complexity and low transmission accuracy still exist simultaneously in IWSN. In the multi-node detection algorithm, the original MPA has good performance and low complexity, but because of the exponential (EXP) algorithm, the complexity of the multi-node detection algorithm is very high. The approximate and the maximum calculation are used in the maximum logarithm message passing algorithm (Max-log-MPA), which results in the loss of some information and poor system accuracy. The T-MPA algorithm adopts the hard decision mechanism, which reduces the complexity of the system algorithm, but has the problem of high accuracy when the threshold is low. The sensor node information updating is integrated into the resource node information updating in the S-MPA algorithm, which effectively reduces the complexity of the system multi-node detection algorithm, but the transmission accuracy of sensor node information is poor. Therefore, in order to further improve the transmission accuracy and complexity of the multi-node detection algorithm in the IWSN, a maximum logarithm message passing algorithm based on serial and threshold (S-T-Max-log-MPA) for multi-mode detection in IWSN is proposed in this paper. In this algorithm, the exponential operation is reduced to the additive operation by using the operation of the logarithmic field, and by reducing the storage space of the sensor node codebook. The serial algorithm and threshold algorithm are used to reduce the code storage time in the iterative process, improve the accuracy of information transmission of sensor nodes, reduce the message loss in the updating process, and reduce the number of iterations of sensor nodes. Therefore, the proposed algorithm in this paper reduces the computational complexity to a large extent while maintaining good accuracy of the wireless sensor network system, especially improving the poor accuracy of data transmission at low threshold in IWSN.