Abstract
Long Range (LoRa) has become one of the most promising physical layer technologies for the Internet of Things (IoT) ecosystem. Although it manifests low-power consumption and long-distance communication, LoRa encounters a large number of collisions in the IoT environment, which severely affects the system’s throughput and delay performance. In this paper, a code division carrier sense multiple access (CD/CSMA) protocol that resolves the traditional channel collision problem and implements multi-channel transmission is proposed for the LoRa medium access control (MAC) layer. To reduce data transmission delay and maximize the throughput of the system, the adaptive p-persistent CSMA protocol divides the channel load into four states and dynamically adjusts the data transmission probability. Then, to reduce channel collisions significantly, the code division multiple access (CDMA) protocol is performed on different channel states. Moreover, the combination of the proposed adaptive p-persistent CSMA protocol and the CDMA successfully reduces the number of data retransmissions and makes LoRa more stable. The simulation results demonstrate that the proposed adaptive p-persistent CD/CSMA protocol can achieve near-optimal and occasionally even better performance than some conventional MAC protocols, especially in a heavy load channel.
Highlights
With the development of wireless sensor networks, the emergent Internet of Things (IoT) uses machines and networks to provide people with convenient services, such as health monitoring, environmental testing, smart appliances and so on. These services have created a new demand for wireless networks, so the improvement of performance of IoT systems has become an interesting topic of research
The above formula indicates that the selection of the probability p should be to solve the heavy load problem, we propose an adaptive p-persistent code division carrier sense multiple access (CD/carrier sense multiple access (CSMA)) protocol, in which based on the load G so that we can obtain the optimal system throughput
As the limits of the adaptive p-persistent CSMA protocol are much closer to being optimal, the load is spread more uniformly over the channels at high traffic
Summary
With the development of wireless sensor networks, the emergent Internet of Things (IoT) uses machines and networks to provide people with convenient services, such as health monitoring, environmental testing, smart appliances and so on. The authors investigated the use of adaptive p-persistent CSMA scheme for long term evolution in unlicensed (LTE-U) bands in [19], only specific traffic and load condition was considered, which is unable to provide a flexible trade-off between the system overall throughput performance and the network offered traffic or the channel load when the deployment varies. This system uses a fixed probability to transmit data packets, which will make the system channel utilization insufficient with changing load Another case that has been considered in [21] is a multiple access system with multiple-packet reception capability that formulates the generalized p-persistent CSMA as a parameterized Markov decision process, in which the characteristics of such CSMA are modeled and transmission probabilities are designed to achieve maximum throughput. We propose an adaptive p-persistent CD/CSMA MAC layer protocol algorithm for improving the performance of the LoRa protocol.
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