Sana Ullah

The integration of wireless sensor networks with Internet of Things (IoT) have revolutionized many applications like health-care, industrial automation, transportation, and agriculture sectors. Such integration requires efficient utilization of resources in order to maximize bandwidth efficiency. This paper presents a dynamic Time Division Multiple Access (TDMA) MAC protocol for IoT-assisted WSNs. The proposed protocol improves bandwidth utilization by allocating slots based on data volume of the nodes. Unlike the conventional TDMA that assigns slots statically, the proposed protocol dynamically allocates slots to nodes according to their requests incorporating criticality, traffic load, and residual energies of the nodes. Such dynamic allocation enhances network performance by reducing delay and increasing throughput. Performance of the proposed protocol is evaluated using the state-of-the-art network simulator NS-3. For different number of nodes, packet sizes, and arrival rates, the proposed protocol outperforms the conventional TDMA in terms of delay and throughput. Overall, the proposed protocol reduces delay by 25% and improves throughput by 26% compared to the conventional TDMA for IoT-assisted WSN.

Applications of wireless sensor networks have significantly increased in the modern era. These networks operate on a limited power supply in the form of batteries, which are normally difficult to replace on a frequent basis. In wireless sensor networks, sensor nodes alternate between sleep and active states to conserve energy through different methods. Duty cycling is among the most commonly used methods. However, it suffers from problems like unnecessary idle listening, extra energy consumption, and packet drop rate. A Deep Reinforcement Learning-based B-MAC protocol called (RL-BMAC) has been proposed to address this issue. The proposed protocol deploys a deep reinforcement learning agent with fixed hyperparameters to optimize the duty cycling of the nodes. The reinforcement learning agent monitors essential parameters such as energy level, packet drop rate, neighboring nodes’ status, and preamble sampling. The agent stores the information as a representative state and adjusts the duty cycling of all nodes. The performance of RL-BMAC is compared to that of conventional B-MAC through extensive simulations. The results obtained from the simulations indicate that RL-BMAC outperforms B-MAC in terms of throughput by 58.5%, packet drop rate by 44.8%, energy efficiency by 35%, and latency by 26.93%

The IEEE 802.15.6 standard has the potential to provide cost-effective and unobtrusive medical services to individuals with chronic health conditions. It is a low-power standard developed for wireless body area networks and enables wireless communication inside or near a human body. This standard utilizes a Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol to improve network performance under different channel access priorities. However, the CSMA/CA proposed in the IEEE 802.15.6 standard has poor throughput performance and link reliability when some of the nodes deployed on a human body are hidden from each other. We employ the RTS/CTS scheme to solve hidden node problems in IEEE 802.15.6 networks over a lossy channel. To improve performance of the RTS/CTS scheme, we adjust transmission power levels of the nodes according to transmission failures. We estimate throughput and energy consumption of the proposed model by differentiating several parameters, such as contention window size, values of bit error ratios, number of nodes in different priority classes. The performance results are obtained through analytical approximations and simulations. We observe that the proposed model significantly improves performance of the IEEE 802.15.6 CSMA/CA by resolving hidden node problems.

The Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) procedure of IEEE 802.15.6 Medium Access Control (MAC) protocols for the Wireless Body Area Network (WBAN) use an Alternative Binary Exponential Backoff (ABEB) procedure. The backoff algorithm plays an important role to avoid collision in wireless networks. The Binary Exponential Backoff (BEB) algorithm used in different standards does not obtain the optimum performance due to enormous Contention Window (CW) gaps induced from packet collisions. Therefore, The IEEE 802.15.6 CSMA/CA has developed the ABEB procedure to avoid the large CW gaps upon each collision. However, the ABEB algorithm may lead to a high collision rate (as the CW size is incremented on every alternative collision) and poor utilization of the channel due to the gap between the subsequent CW. To minimize the gap between subsequent CW sizes, we adopted the Prioritized Fibonacci Backoff (PFB) procedure. This procedure leads to a smooth and gradual increase in the CW size, after each collision, which eventually decreases the waiting time, and the contending node can access the channel promptly with little delay; while ABEB leads to irregular and fluctuated CW values, which eventually increase collision and waiting time before a re-transmission attempt. We analytically approach this problem by employing a Markov chain to design the PFB scheme for the CSMA/CA procedure of the IEEE 80.15.6 standard. The performance of the PFB algorithm is compared against the ABEB function of WBAN CSMA/CA. The results show that the PFB procedure adopted for IEEE 802.15.6 CSMA/CA outperforms the ABEB procedure.

This paper introduces a hybrid and secure MAC protocol (PMAC) for WBAN. The PMAC protocol uses two contention access periods (CAPs) for accommodating normal and life-critical traffic and one contention-free period (CFP) for accommodating large amount of data packets. The priority-guaranteed CSMA/CA procedure is used in the CAP period, where different priorities are assigned to WBAN nodes by adjusting the backoff window size. In addition, a set of security keys is used to prevent illegal access to the network. Analytical expressions are derived to analyze the average delay, power consumption, throughput, and packet loss probability of the PMAC protocol. Results derived from these expressions are validated by computer simulations.

IEEE 802.15.6 is the first international Wireless Body Area Network (WBAN) standard that supports communications in the vicinity of or inside a human body to serve a variety of medical and nonmedical applications. The standard defines a Medium Access Control (MAC) layer that supports several Physical (PHY) layers. In this paper, the key features of the IEEE 802.15.6 standard are presented. The MAC, PHY, and security specifications of the standard are explained in detail. Different communication modes and access mechanisms are presented. The Narrowband (NB), Ultra-wideband (UWB), and Human Body Communications (HBC) specifications are reviewed in terms of frame structure, modulation, and other important parameters. Finally, the security paradigm and services of the standard are highlighted.