# ABORt: Acknowledgement-Based Opportunistic Routing Protocol for High Data Rate Multichannel WSNs
## 1 Introduction  
Wireless sensor networks (WSNs) are a very attractive solution for their ease of deployment and auto-configuration. A wide range of needs can be answered using WSNs in environmental, medical, industrial or military applications [1]. This technology has attracted a lot of researchers and intensive work has been done on energy efficiency communication protocols [2; 3], and has also been considered for high data rate applications [4; 5]. The most successful standard to define physical and link layers for this domain is the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 [6]. It has paved the way for other Internet Engineering Task Force (IETF) standards such as the Routing Protocol for low-power and Lossy networks (RPL) [7] and industrial standards such as ZigBee [8], WirelessHART [9] and ISA100.a [10]. In this paper, we focus on enhancing the network efficiency in high data rate scenarios in terms of packet delivery ratio, throughput, and end-to-end delay by investigating the use of an adaptive routing protocol over a multichannel MAC (Medium Access Control) protocol.  
The use of multiple channels helps to mitigate some issues encountered in single channel communications like interference and collisions caused by high contention. With more bandwidth, less interference and less collisions, the network performances will be enhanced and the traffic load in the network will increase. Nodes will have more data to transmit towards the sink and intermediatenodes will have to cope with the traffic rate and find a way to balance the traffic load among them. This is typically the role of a load balancing routing protocol.  
Routing in multichannel WSNs has been extensively studied [11; 12]. However, having a routing protocol that permits reaching a high data rate in multichannel WSNs remains an open research topic. The constrained resources (computation, memory, energy and communication range) of sensor nodes coupled with a shared wireless medium makes the issue more complex. In single channel WSNs, the interference level is high under high data rate scenarios, which leads to higher risks of collisions and packet loss. Multichannel communication has been introduced in order to reduce the interference level and improve the data delivery ratio. In multichannel protocols, nodes do not listen on the same channel all the time like in single channel protocols. This makes topology and routing information diffusion more challenging. To overcome this issue, some protocols introduce a synchronization phase where all nodes in the network have to tune their radio on the same channel for exchanging control traffic. However, synchronization is time and energy consuming in addition to the fact that it is hard to achieve in large scale networks.  
In this paper, we propose an alternative approach for routing information sharing in multichannel communication by using MAC layer acknowledgements in an opportunistic way. ABORt, or Acknowledgement-Based Opportunistic Routing, is our contribution. It is a routing protocol designed for high data rate multichannel WSNs. ABORt does not rely on periodic control messages for exchanging the routing information. Hence, it avoids costly synchronization periods during the operational phase of the network for exchanging control traffic and enhances throughput and access delay by doing so. The routing metric used by ABORt is based on the average queueing delay of data packets. In addition, ABORt uses multiple next hop nodes towards the destination whenever possible and efficient to do so in order to achieve load balancing.  
The remainder of the paper is organized as follows. In Section 2, we present the main contributions in the related work on joint channel selection and routing protocols in multichannel WSNs. In Section 3, we present a detailed description of ABORt. In Section 4, we discuss the simulation results. Section 5 concludes the paper and presents our future work.