In this article, a multichannel preamble sampling MAC protocol, MCPS, especially tailored for wireless sensor networks, is proposed and thoroughly evaluated. MCPS is a low-power MAC protocol operating on multichannel using carrier sensing for collision avoidance. Specifically, MCPS exploits all the non-overlapping channels provided by IEEE 802.15.4 physical layer. Basically, MCPS uses one dedicated common control channel to wake up an intended receiver using a preamble sampling technique. However, data transmission takes place in a dedicated data channel. Indeed, MCPS allocates to every pair of sensor nodes a unique data channel that aims at being 2-hop conflict free. Hence, the probability of collision is highly reduced and even completely mitigated in some scenarios. Moreover, MCPS allows each sensor node to dynamically adjust its transmission power when sending strobed preamble or periodically generated data. Indeed, for each possible distance separating a pair of communicating nodes, MCPS adapts the appropriate transmission power and selects the appropriate data channel. Using multiple channels, MCPS allows multiple simultaneous data communications along with handshaking on the common control channel, hence reducing the end-to-end delay and improving the throughput while being energy efficient. MCPS has been implemented using OMNET++ simulator under INET framework, on top of the IEEE 802.15.4 physical layer, which was improved to support the multichannel communication. The authors compare the performance of MCPS with McMAC and X-MAC. Simulation results show that MCPS greatly improves the network performance especially in terms of throughput, waiting time, end-to-end delay, and energy per bit.

Wireless Sensor Networks (WSNs) are witnessing a momentum spread especially with the growth of the Internet of Things (IoT) paradigm. Indeed, WSNs are considered as the main enabling infrastructure for IoT networks. Nowadays, the emerging WSNs applications require not only long network lifespan but also considerably high data rate. Consequently, conceiving Multichannel MAC protocols that save the scarceenergy budget of sensor nodes while providing high network throughput is crucial for the emerging WSNs applications. In this paper, a thorough review of recent multichannel MAC protocols is provided along with a classification framework to deeply understand the design aspects for each protocol.

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In this paper, we introduce Sensitivity-Aware LoRa Configuration (SAL), a new algorithm for efficient autonomous and distributed selection of LoRa physical layer transmission parameters. The aim is to address the limitations of the currently adopted MAC algorithm in LoRaWAN networks (i.e., Adaptive Data Rate -ADR). The selection of the transmission parameters in ADR is done randomly by the gateway node, an approach that may result in the gateway reaching its Duty Cycle Limit, consequently hindering it from sending the configuration information to the end points under large-scale networks negatively affecting the network performance. Unlike ADR, SAL uses a decentralized approach to select node's transmission parameters without any need for gateway's control packets and it only considers a combination of parameters that is guaranteed to be received successfully by the gateway. The performance of the proposed algorithm is validated through extensive simulation experiments under different scenarios and operation conditions. In particular, SAL is compared to LoRaWAN configuration algorithm in terms of Packet Error Rate (PER), Capture effect Probability, Collision Probability, End-to-end Delay, Packet Delivery Ratio (PDR), Throughput and Energy Consumption showing promising results in this context.

Time-Slotted Medium Access Control protocols bring advantages to the scalability of LoRa networks as an alternative to the ALOHA access method. However, such Time-Slotted protocols require nodes synchronization and schedules dissemination under stringent duty cycles likely resulting in improper performance and limited scalability. One possible solution is to adopt decentralized approaches where nodes autonomously determine their schedules and other transmission parameters. Thus, this paper proposes a novel Time-Slotted MAC protocol, named Autonomous Adaptive Frame Size (AAFS-LoRa) protocol, that allows nodes to individually determine their transmission parameters without extensive downlink transmissions from the gateway. The proposed protocol can configure nodes by maintaining information, such as their location and the gateway location. The main contribution of the proposed protocol is the adoption of adaptive frame sizes that are large enough to accommodate nodes with common transmission parameters to mitigate collisions among them. The proposed protocol has been investigated under different operating conditions, and the experiments demonstrates that our protocol can effectively improve the network performance, in terms of latency as well as the capacity.