Many Medium Access Control Research Articles

Machine Learning Prediction Based Adaptive Duty Cycle MAC Protocol for Solar Energy Harvesting Wireless Sensor Networks

The dynamic nature of energy harvesting rate, arising because of ever changing weather conditions, raises new concerns in energy harvesting based wireless sensor networks (EH-WSNs). Therefore, this drives the development of energy aware EH solutions. Formerly, many Medium Access Control (MAC) protocols have been developed for EH-WSNs. However, optimizing MAC protocol performance by incorporating predicted future energy intake is relatively new in EH-WSNs. Furthermore, existing MAC protocols do not fully harness the high harvested energy to perform aggressively despite the availability of sufficient energy resources. Therefore, a prediction-based adaptive duty cycle (PADC) MAC protocol has been proposed, called PADC-MAC, that incorporates current and future harvested energy information using the mathematical formulation to improve network performance. Furthermore, a machine learning model, namely nonlinear autoregressive (NAR) neural network, is employed that achieves good prediction accuracy under dynamic harvesting scenarios. As a result, it enables the receiver node to perform aggressively better when there is sufficient inflow of incoming harvesting energy. In addition, PADC-MAC uses a self-adaptation technique that reduces energy consumption. The performance of PADC-MAC is evaluated using GreenCastalia in terms of packet delay, network throughput, packet delivery ratio, energy consumption per bit, receiver energy consumption, and total network energy consumption using realistic harvesting data for 96 consecutive hours under dynamic solar harvesting conditions. The simulation results show that PADC-MAC provides lower average packet delay of the highest priority packets and all packets, energy consumption per bit, and total energy consumption by more than 10.7%, 7.8%, 81%, and 76.4%, respectively when compared to three state-of-the-art protocols for EH-WSNs.

Echo state neural network-assisted mobility-aware seamless handoff in mobile WSNs

Strong mobility in Wireless Sensor Networks (WSNs) may disrupt an existing link between two communicating nodes. Because many Medium Access Control (MAC) protocols cannot adapt to the strong mobility of nodes, facing a decaying link, a node usually chooses to continue its data communication until the current link is terminated, and then searches for a new relay node to build a better connection. However, this will cause serious transmission latency. To tackle this problem, this paper proposes an echo state neural network-assisted mobility-aware seamless handoff method, which enables a node to handoff communication seamlessly to a more reliable link while maintaining communication over the current connection, and the current connection will be interrupted only after a new link is set up. To demonstrate the superiority of handoff, by taking the cattle monitoring as an example where nodes move at a constant speed, this paper designs a static-oriented Beacon-Initiated MAC (BI-MAC) protocol, develops a distance threshold as the handoff initiation signal, predicts future locations of nodes with a machine learning-based Echo State Network (ESN), formulates a mobility-aware seamless handoff module on top of the BI-MAC, and compares the data communication latency using and not using the handoff. Both the analytical and NS2 simulation results show that the time to set up a new link is much longer than the handoff latency. The one-hop latency can be reduced by at least 42% with the handoff support. This figure can further grow with the increase in duty cycle, network density, and size of multi-hop links.

A Mac Protocol with Dynamic Allocation of Time Slots Based on Traffic Priority in Wireless Body Area Networks

In a wireless body area network (WBAN), wireless biomedical sensors are placed around, on, or inside the human body. Given specific requirements, WBANs can significantly improve healthcare, diagnostic monitoring, and other medical services. However, the existing standards such as IEEE 802.11 and IEEE 802.15.4 have some limitations to meet all the requirements of WBANs. Many medium access control (MAC) protocols have been studied so far, most of which are derived from the IEEE 802.15.4 superframe structure with some improvements and adjustments. However, the MAC protocols do not provide the required quality of service (QoS) for various types of traffic in a WBAN. In this paper, a traffic-aware MAC (TA-MAC) protocol for WBANs is proposed, in which time slots are dynamically allocated on the basis of traffic priority, providing the required QoS. According to the performance evaluation results, the proposed TA-MAC is better than IEEE 802.15.4 MAC and the conventional priority-based MAC in terms of transmission time, system throughput, energy efficiency, and collision ratio.

A Mac Protocol With Dynamic Allocation of Time Slots Based on Traffic Priority in Wireless Body Area Networks

In a wireless body area network (WBAN), wireless biomedical sensors are placed around, on, or inside the human body. Given specific requirements, WBANs can significantly improve healthcare, diagnostic monitoring, and other medical services. However, the existing standards such as IEEE 802.11 and IEEE 802.15.4 have some limitations to meet all the requirements of WBANs. Many medium access control (MAC) protocols have been studied so far, most of which are derived from the IEEE 802.15.4 superframe structure with some improvements and adjustments. However, the MAC protocols do not provide the required quality of service (QoS) for various types of traffic in a WBAN. In this paper, a traffic-aware MAC (TA-MAC) protocol for WBANs is proposed, in which time slots are dynamically allocated on the basis of traffic priority, providing the required QoS. According to the performance evaluation results, the proposed TA-MAC is better than IEEE 802.15.4 MAC and the conventional priority-based MAC in terms of transmission time, system throughput, energy efficiency, and collision ratio.

A Priority-Based Adaptive MAC Protocol for Wireless Body Area Networks.

In wireless body area networks (WBANs), various sensors and actuators are placed on/inside the human body and connected wirelessly. WBANs have specific requirements for healthcare and medical applications, hence, standard protocols like the IEEE 802.15.4 cannot fulfill all the requirements. Consequently, many medium access control (MAC) protocols, mostly derived from the IEEE 802.15.4 superframe structure, have been studied. Nevertheless, they do not support a differentiated quality of service (QoS) for the various forms of traffic coexisting in a WBAN. In particular, a QoS-aware MAC protocol is essential for WBANs operating in the unlicensed Industrial, Scientific, and Medical (ISM) bands, because different wireless services like Bluetooth, WiFi, and Zigbee may coexist there and cause severe interference. In this paper, we propose a priority-based adaptive MAC (PA-MAC) protocol for WBANs in unlicensed bands, which allocates time slots dynamically, based on the traffic priority. Further, multiple channels are effectively utilized to reduce access delays in a WBAN, in the presence of coexisting systems. Our performance evaluation results show that the proposed PA-MAC outperforms the IEEE 802.15.4 MAC and the conventional priority-based MAC in terms of the average transmission time, throughput, energy consumption, and data collision ratio.

Modeling and Performance Analysis of Channel Assembling in Multichannel Cognitive Radio Networks With Spectrum Adaptation

To accommodate spectrum access in multichannel cognitive radio networks (CRNs), the channel-assembling technique, which combines several channels together as one channel, has been proposed in many medium access control (MAC) protocols. However, analytical models for CRNs enabled with this technique have not been thoroughly investigated. In this paper, two representative channel-assembling strategies that consider spectrum adaptation and heterogeneous traffic are proposed, and the performance of these strategies is evaluated based on the proposed continuous-time Markov chain (CTMC) models. Moreover, approximations of these models in the quasistationary regime are analyzed, and closed-form capacity expressions are derived in different conditions. The performance of different strategies, including the strategy without assembling, is compared with one another based on the numerical results obtained from these models and validated by extensive simulations. Furthermore, simulation studies are also performed for other types of traffic distributions to evaluate the validity and the preciseness of the mathematical models. Through both analyses and simulations, we demonstrate that channel assembling represented by the investigated strategies can improve the system performance if a proper strategy is selected with appropriate system parameter configurations.

An energy-efficient, transport-controlled MAC protocol for wireless sensor networks

In wireless sensor networks (WSNs), one major cause of wasted energy is that the wireless network interface is always on to accept possible traffic. Many medium access control (MAC) protocols therefore adopted a periodic listen-and-sleep scheme to save energy, at sacrifice of end-to-end latency and throughput. Another cause is packet dropping due to network congestion, necessitating a lightweight transport protocol for WSNs. In this paper, we suggest a transport-controlled MAC protocol (TC-MAC) that combines the transport protocol into the MAC protocol with the aims of achieving high performance as well as energy efficiency in multi-hop forwarding. Although TC-MAC also works through a periodic listen-and-sleep scheme, it lowers end-to-end latency by reserving data forwarding schedules across multi-hop nodes during the listen period and by forwarding data during the sleep period, all while increasing throughput by piggybacking the subsequent data forwarding schedule on current data transmissions and forwarding data consecutively. In addition, TC-MAC gives a fairness-aware lightweight transport control mechanism based on benefits of using the MAC-layer information. The results show that TC-MAC performs as well as an 802.11-like MAC in end-to-end latency and throughput, and is more efficient than S-MAC in energy consumption, with the additional advantage of supporting fairness-aware congestion control.

Receiver-initiated collision avoidance in wireless networks

Many medium-access control (MAC) protocols for wireless networks proposed or implemented to date are based on collision-avoidance handshakes between sender and receiver. In the vast majority of these protocols, including the IEEE 802.11 standard, the handshake is sender initiated, in that the sender asks the receiver for permission to transmit using a short control packet, and transmits only after the receiver sends a short clear-to-send notification. We analyze the effect of making the collision-avoidance handshake, receiver initiated and compare the performance of a number of receiver-initiated protocols with the performance of sender-initiated collision avoidance protocols. Analytical and simulation results show that the best-performing collision avoidance MAC protocol based on receiver-initiated or sender-initiated collision avoidance is one in which a node with data to send transmits a dual-purpose small control packet inviting a given neighbor to transmit and asking the same neighbor for permission to transmit. The receiver-initiated protocols we present make use of carrier sensing, and are applicable to either baseband or slow frequency-hopping radios in which an entire packet can be sent within the same frequency hop (which is the case of frequency hopping spread spectrum (FHSS) commercial radios).

Performance of Single-Hop WDM LANs Supporting Real-Time Services

Optical wavelength division multiplexing (WDM) local area networks are capable of fulfilling the enormous bandwidth demands of present and future applications. Up to now, the WDM LAN world is primarily dominated by the passive-star coupler (PSC) based architectures, for which many medium access control (MAC) protocols have been proposed. However, an arrayed waveguide grating multiplexer (AWGM)-based single-hop WDM network seems to be a very promising alternative. One of the most critical issues in designing next generation photonic LANs is the support of real-time services for applications with different time constraints. In this paper, different basic access protocols for the PSC as well as AWGM-based single-hop WDM LANs are considered and their performance in supporting real-time traffic is analyzed by means of extensive computer simulations. For evaluation of real-time performance, packet drop rates and deadline missing rates are taken as performance measures. Furthermore, new real-time message scheduling schemes are proposed which improve the performance of protocols accommodating mixed traffic. They can be differentiated between message scheduling at the source nodes’ transmit queues and scheduling based upon control information from a control channel. It is shown that both types of priority scheduling significantly improve the overall real-time performance.