## 4 Congestion Mitigation Algorithms for WSNs
### Previous Work on WSN Congestion Mitigation Schemes
#### 4.1.1 Conventional Algorithms for Congestion Mitigation in WSN  
A method for optimizing the use of network resources was proposed in a paper by [PERSON] [31]. The proposed method facilitates the allocation of time-constrained uplink resources with contention. Achieving maximum resource utilization leads to a reduction in congestion, energy consumption, access latency, and blocking probability. This study also examines the variables that cause the degradation of IoT devices with a backlog in WSN. Compared with the strategy of the dynamic banning of access classes, the proposed method performs better and is more effective. The results of the previous work, where a binary integer programming scenario was created, show that the proposed strategy achieves a desirable access delay value. Back-off (BO) and distributed queuing (DQ) are two commonly used computer network techniques. Collision-Free Full-Duplex Communication for MAC (CFFD-MAC) is a proposal discussed by [PERSON] et al. in [32] that attempts to increase the throughput of IoT networks by leveraging full-duplex transmission in existing wireless sensor networks (WSNs). The proposed strategy uses a slotted-time contention protocol within the MAC architecture to achieve the desired purpose. With minimal control overhead, this protocol allows devices to randomly access the communication channel. Devices use a queue for efficient use and send data in contention-free time slots with non-colliding neighboring nodes to achieve the lowest number of hops possible. [PERSON] and [PERSON] in [33] introduced Fast Adaptive Slotted ALOHA (FASA) to manage random access IoT devices when traffic is bumpy. Observing the data of consecutive colliding and unused slots is critical to optimize the S-ALOHA. The estimated active number of IoT devices under FASA quickly converges towards the true number  
Figure 2: An overview of congestion mitigation AI algorithms in the literature for WSN. thanks to the drift analysis-based architecture. Moreover, the authors showed that the proposed system is stable until the average arrival rate is less than e(-1) by studying the drift of the slots. The simulation results show that the proposed system outperforms more established methods such as Pseudo Bayesian ALOHA (PB-ALOHA) and achieves near-ideal performance in reducing access delay. In addition, FASA performs better in delay and is robust to bursty traffic. In [34], [PERSON] and [PERSON] proposed a novel group-based paging for wireless IoT base networks to reduce congestion. Group-based paging allows the eNodeB to coordinate with the network, and this system manages congestion RACH. The proposed technique differs from traditional paging methods in that it does not require each IoT device to attempt to establish a network connection. However, the proposed paging strategy gives the selected IoT device, referred to as a group, authority over the RACH procedure of IoT devices in the form of an access group. The authors also proposed signaling techniques that facilitate resource allocation at the access group level for data messages directly and group-based connectivity through group delegation. Numerical results show that the group access technique achieves significantly lower access delay compared to the standard access scheme. It also supports signaling protocols based on the number of group delegates rather than the number of IoT devices, where the signaling overhead is proportional to the number of group delegates. The proposed system can increase the number of IoT devices that can be offloaded simultaneously without incurring congestion management, overhead, and access latency. It also promotes resource reuse by effectively utilizing data transfer resources. The channel resource usage, in an efficient manner, depends on the reassignment of the channel. Software-Defined Networking based on IoT (SDN-IoT) is a promising methodology for channel reassignment.