## 4 Congestion Mitigation Algorithms for WSNs
### Previous Work on WSN Congestion Mitigation Schemes
#### 4.1.3 Game Theory-Based Algorithms for Congestion Mitigation in WSN  
[PERSON] and [PERSON] proposed a congestion control algorithm for a tree-based network in [69] using non cooperative game theory. In this technique, the data transmission rate of each leaf node is optimized. The main objective of this work is to identify a unique Nash equilibrium point for the best data transfer rate of each leaf node, which prevents congestion at the parent destination until the service rate for the destination node remains the same. The throughput of the entire network is, thus, optimized. The author of this paper believes that the main causes of packet loss are channel congestion and buffer overflow. NGTCC (Non-cooperative Game Theory-based Congestion Control) is the name of the proposed work to reduce traffic. The simulation results of the proposed work show that it performs better than the alternatives in terms of throughput and data transfer rate. The optimization-based hybrid congestion mitigation (OHCA) strategy for 6 LoWPAN was proposed in [66]. It uses both resource management and traffic control strategies. When congestion occurs, OHCA uses Gray Relational Analysis (GRA) [65] to find another route that is not congested. In the absence of an alternate route, OHCA implements a traffic management strategy using a \"game theory-based congestion control framework (GTCCF)\" [70] and modifies the transmit data rates of the associated leaf nodes. However, the currently proposed congestion mitigation strategy ignores the above problem and instead emphasizes only network throughput or delay. Non-cooperative Gaming for Energy-efficient Congestion Control (NGECC), a unique approach, was proposed in [71]. In this work, the energy parameter of the 6 LoWPAN network is considered for the first time. Moreover, the real-time simulator Cooja and the operating system Contiki are used to test this work. In IoT, WSNs play an important role [58]. The Internet integrates 6 LoWPANs and WSNs. An Internet Protocol (IP) stack is used to implement the sensor nodes, but it is designed for wired networks [59] However, using the Transmission Control Protocol IP (TCP/IP) standard in 6 LoWPAN networks and WSNs presents a number of issues and challenges, including buffer and energy resources and bandwidth limitations. In addition, TCP requires additional resources for connection establishment and termination, while User Datagram Protocol (UDP) has no congestion control mechanism at the end of data transmission. In [72] [PERSON] et al. developed the Duty Cycle-Aware Congestion Control (DCCC6) method to reduce congestion in 6 LoWPAN networks. This method determines the radio duty cycle and changes the operation as needed. It uses a modified \"Additive-Increase Multiplicative-Decrease AIMD\" method to reduce network congestion and dynamic buffer allocation for congestion detection. Fuse, Gripping, and Deaf are three different congestion avoidance strategies that were developed by [PERSON] et al. in [42]. They are used in CoAP/6 LoWPAN networks to regulate both unidirectional and bidirectional data flows. The basic ideas behind these proposed algorithms are distributed backpressure. The missing acknowledgment packet and buffer occupancy strategies both use gripping. In the AIMD scheme, Fuse and Deaf are used for both congestion detection and congestion mitigation. Congestion mitigation reduces incoming packets by adjusting the transmission rate. For CoAP/6 LoWPAN networks, [PERSON] and [PERSON] [41] presented a technique for congestion mitigation. The concept of flocking birds serves as the basis for this algorithm. To avoid congested paths, this concept is implemented by routing packets through congestion-free zones. Moreover, the proposed method uses the buffer occupancy technique to identify congested nodes and manage resources by selecting the least congested paths to reduce congestion. An RPL-based algorithm called \"Queue Utilization Based RPL (QU-RPL)\" was proposed by [PERSON] et al. in [35]. This algorithm makes use of the queue.