Wireless Networking Performance in IoT Using Adaptive Contention Window

Abstract

Internet of Things (IoT) network contains heterogeneous resource-constrained computing devices which has its unique reputation in IoT environments. In spite of its distinctiveness, the network performance deteriorates by the distributed contention of the nodes for the shared wireless medium in IoT. In IoT network, the Medium Access Control (MAC) layer contention impacts the level of congestion at the transport layer. Further, the increasing node contention at the MAC layer increases link layer frame drops resulting in timeouts at the transport layer segments and the performance of TCP degrades. In addition to that, the expiration of maximum retransmission attempts and the high contentions drive the MAC retransmissions and the associated overheads to reduce the link level throughput and the packet delivery ratio. In order to deal with aforementioned problems, the Adaptive Contention Window (ACW) is proposed, which aims to reduce the MAC overhead and retransmissions by determining active queue size at the contending nodes and the energy level of the nodes to improve TCP performance. Further, the MAC contention window is adjusted according to the node's active queue size and the residual energy and TCP congestion window is dynamically adjusted based on the MAC contention window. Hence, by adjusting the MAC Adaptive Contention Window, the proposed model effectively distributes the access to medium and assures improved network throughput. Finally, the simulation study implemented through ns-2 is compared with an existing methodology such as Cross-Layer Congestion Control and dynamic window adaptation (CC-BADWA); the proposed model enhances the network throughput with the minimal collisions.

Priority and Traffic-Aware Contention-Based Medium Access Control Scheme for Multievent Wireless Sensor Networks

“…But under interference, this approach becomes less efficient in terms of throughput than the conventional low-performance MAC schemes like Sensor-MAC (S-MAC) [24] and T-MAC [25]. On the other hand, an effective approach for performance enhancement is to implement the contention windows adaptively [21], [22]. Authors in [21] offered an adaptive contention window backoff mechanism to improve the network performance by adjusting the backoff time according to the number of active stations in each access category.…”

“…Authors in [21] offered an adaptive contention window backoff mechanism to improve the network performance by adjusting the backoff time according to the number of active stations in each access category. Similarly, the work in [22] introduced a MAC Adaptive Contention Window (ACW), that changes adaptively according to the node's active queue size and remaining energy. Although these works show a lot of potential for achieving better network performance, they have not taken the priority of data packets into account.…”

“…RTS with 𝑝 4 is the first to reach the sink before the ending time of 𝑇 𝑤 , then in the next cycle, RTS with 𝑝 3 reaches sink before 𝑇 w runs out, and the sink sends CTS at the end of 𝑇 w . So even with the best case, the numerical expression of TMPQ-MAC average access delay of priority 4 and 3 is respectively given by: 𝑡 accessTMPQ= 4 𝑡 start +𝑡 p +𝑡 RTS (5) (6) in which 𝑡 p is the probabilistic delay time which depends on the number of sows and in case 𝑀 = 2 or 𝑝 = 1/2 (as analyzed in [22], [36].…”

“…However, most of these protocols have limited considerations in supporting packet priority level, and the impacts of the contention window on average packet delay and energy consumption. On the other hand, various scheduling schemes have been presented for improving the performance of MAC protocol, especially by adjusting the size of the contention window size [21], [22]. These works imply that adjusting the contention window size adaptively can help to enhance network throughput and lessen the MAC overhead and retransmissions.…”

Capacity utilization based on contention window management in mobile ad hoc network

“…Bhavadharini et al proposed the adaptive CW (ACW) intended to reduce the overhead and the retransmission problems in then MAC layer. In this method, for every unsuccessful frame transmission, the node waits for a random back off time and determine the channel state.…”