# Reliability Improved Cooperative Communication over Wireless Sensor Networks
## 1 Introduction  
The Internet of Things (IoT) [1; 2; 3; 4] uses smart equipment such as sensor-based devices [5; 6; 7; 8; 9; 10; 11], smartphones [12] and vehicle sensor devices [13] to gathering information and give a different method for carrying out complex data-sensing-based tasks to satisfy the significant demands of critical infrastructures [14; 15; 16; 17; 18], such as environmental and weather monitoring systems [19; 20; 21; 22; 23]. Wireless Sensor Networks (WSNs) has large numbers of sensor nodes, it has huge potential to solve military and civilian domains [24; 25; 26; 27; 28; 29]. Portable devices usually operate on their own to solve a single or multiple signal processing tasks (such as communications) in a non-cooperative fashion. Having the ability to achieve superior performance without a dedicated and power-hungry central device, distributed and cooperative processing techniques over WSNs have received much attention [28; 30; 31]. Recently, multi-input-multi-output (MIMO) systems has higher promising to improve transmissionreliability [25; 28; 32]; in WSNs, this feature can be obtained by receiving new versions of program codes that are disseminated from a sink node. For data collection, some sensing applications have the strict requirement. The arrival ratio of data packet should be high [32]. Studies revealed that only the number of hop from source to the sink is 5, the end-to-end reliability is less than 73.51%, its reliability is less [32]. Due to the inherent characteristic of constrained resources, data packet is transmitted to the sink, the energy consumption in the area near to the sink is higher than other areas, the energy left of other nodes can be used to improve network performance [3; 4; 6; 30; 31; 32]. In WSNs, the packet can be lost by malicious nodes. [PERSON] et al. proposed a communication scheme named the Network Coding-based Cooperative Communications scheme (NCCC) as shown in Figure 1[31], which achieves high reliability through the cooperation of multi-nodes, where the data transmission reliability can be evaluated by Message Fail delivering Ratio (MFR). Generally, increasing the data transmission power of a node is an effective method to improve the data reliability. However, this method will increase the energy consumption of the node, thereby shortening its lifetime [10]. Numerous studies have shown that there is a trade-off between energy efficiency and data reliability [25; 28; 30; 32]. Determining how to guarantee the data transmission reliability while maintaining the lifetime of the node is a challenging issue. In this paper, based on a WSDN in which software inside the sensors can help them construct clusters to perform the data collection task, a data collection scheme named Reliability Improved Cooperative Communications (RICC) is proposed to increase the network reliability and energy utilization ratio without harming the network lifetime. The invitations are as follows:  
1. A Reliability Improved Cooperative Communications (RICC) with adjustable data transmission power [31] is proposed, in which the residual energy in non-hotspots is fully utilized to increase the transmission power of nodes to improve the data transmission reliability, whereas in hotspot areas, the transmission power is unchanged to maintain the previous network lifetime. For cooperative communications, the higher the transmission power of the nodes is, the shorter the lifetime of the nodes is. Thus, if the data transmission reliability is kept the same as before, the network lifetime is damaged. Due to different nodes load different amount of data, the energy consumption of different nodes is different, the non-hotspots area has much energy left. Therefore, in this paper, RICC adopts higher transmission power in non-hotspot regions, while using the same transmission power in hotspots areas as in previous schemes. Because most nodes are in non-hotspot areas, RICC can effectively improve the data transmission reliability.