# Edge-Aided Reliable Data Transmission for Heterogeneous Edge-IoT Sensor Networks
## 1 Introduction
As a result, when an edge server transmits a packet to a certain number of sensor nodes, it causes interference to other sensor nodes which do not need those transmissions. Whether it is beneficial or harmful for the overall performance of data transmissions is the key to deciding whether we should employ edge servers or not. Second, for the poor links in sensor networks, error recovery from sensor nodes may cost a large number of retransmissions. At the same time, if we use edge servers to recover those packet errors, much overhead is saved. A key challenge for retransmissions of edge servers is that edge servers are not aware of the real-time status of packet receptions/losses. The acknowledgments from sensor nodes cannot be delivered to the edge servers due to the limited communication range of sensor nodes. To overcome the above challenges, we propose an edge-aided reliable data transmission scheme for heterogeneous sensor networks. First, we devise a fast estimation scheme to help edge servers to evaluate how many sensor nodes are requiring the current packet. On the basis of the estimation, we further estimate the potential benefits of using edge servers for data transmission. If the improved packet reception rate (PRR) for target sensor nodes is larger than the degraded PRR for other sensor nodes, the edge server starts forwarding the data. Otherwise, the edge server drops those packets until the above condition is met. Second, we propose a PRR-based reception estimation scheme to find out how many sensor nodes have missed packet transmissions multiple times with poor links. When the number of missing packets exceeds a given threshold, the edge servers start packet retransmissions to avoid endless packet retransmissions on poor wireless links. On the basis of the above two novel schemes, we design a framework of edge-aided reliable data transmission and implement it in simulations. The evaluation results show that with the help of edge computing servers, the efficiency of data transmissions in sensor networks can be largely improved. The major contributions include:  
1. The identification of the opportunity of exploiting edge servers to increase the reliability of data transmissions in sensor networks. 2. The proposal of an adaptive approach to employ edge servers for data transmissions. The edge servers are involved in data transmissions only when it is beneficial and the overall reliability of data transmissions in the sensor network can be improved. 3. The proposal of an edge-aided retransmission scheme to further increase the reliability of _poor_ links in sensor networks, with which the number of retransmissions can be significantly reduced. The remainder of this paper is organized as follows. Section 2 presents the related works of data transmissions in sensor networks and recent advances in edge computing. Section 3 presents the main design of the edge-aided data transmissions in heterogeneous sensor networks. Section 4 evaluates edge-aided data transmission with simulation experiments. Section 5 concludes this work and discusses future directions.