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In this paper, we propose a new media access protocol for single hop Wavelength Division Multiplexing (WDM) networks with a passive star topology. In the conventional protocols, when the control packets collided with other ones or the packets didn't get a data channel from the channel reservation mechanism, these packets should be retransmitted. But, when transmission distance becomes long, it takes a long time to transmit the control packets and the propogation dalay time will be long. We propose a new protocol that can allocate data channels without retransmitting control packets except the collided ones. By using the proposed protocol, it is possible to reduce the transmission delay time and to get high throughput because the number of retransmitted control packets is reduced. The simulation results show that the proposed protocol has good performance comparied with conventional protocols.

Existing TDMA-based MAC protocols for wireless sensor networks are not specifically built to consider communication channels that are prone to fading. We describe the impact of periodically changing environment on small-scale fading effects in industrial indoor wireless networks. Using a site-specific ray tracer, we show that the position of nodes and the periodic movements of objects with constant velocities in the environment have significant impact on signal fading. Finding that fading is approximately periodic, we propose a TDMA-based MAC protocol for wireless sensor networks built for industrial applications that uses link state dependent scheduling. In our approach, nodes gather samples of the channel quality and generate prediction sets from the sample sets in independent slots. Using the prediction sets, nodes only wake up to transmit/receive during scheduled slots that are predicted to be clear and sleep during scheduled slots that may potentially cause a transmitted signal to fade. We simulate our proposed protocol and compare its performance with the well published Z-MAC protocol. We found that our protocol significantly improves packet throughput and energy consumption as compared to Z-MAC. We also found that in conditions which are not perfect under our assumptions, the performance of our protocol degrades gracefully.

This paper presents a distributed and concurrent multiple access-based collision avoidance MAC scheme to increase spatial reuse and hence the overall throughput of wireless networks. We make use of location information and power capture techniques to realize this protocol. While other wireless MAC protocols have used power capture technique in a general manner to reject the interfering signals during the entire reception of a packet, we exploit the additional capability of power capture to "lock-on" to the intended packet during a period known as "capture time" to admit other parallel transmissions. Simulation results show that our protocol can outperform the IEEE 802.11 throughput performance by a factor of 2 or more when there are short and medium range transmissions within a given area.

Broadcast is a efficient method that allows the nodes in the wireless networks share the data among other nodes. Because the transmissions of broadcast packet are related to receive of multi-nodes, it is difficult to ensure the reliable transmission of broadcast packet. In the wireless sensor networks, due to limitation of battery power in sensor nodes, it is more difficult to ensure the reliable transmission of broadcast. In the paper, a new synchronous MAC protocol, termed the Evolutionary Reliable Broadcast Protocol (ERBP), is introduced. In existing MAC protocols for WSN, the transmission of the broadcast packet consumes much energy, but the transmission reliability is low. In ERBP, we design a novel receiver-based conflict detecting mechanism and simple four-handshake process of the control packet to solve the problem. By simplifying the handshake process of the control packet, using the periodic sleep scheme and the collision avoidance measures, it reduces the energy consumption. Through study of Energy-efficiency of the protocol, it is proved that the ERBP not only has high transmission reliability of broadcast, but energy-efficiency is better.

Wireless local area network (LAN) is based on the IEEE 802.11 protocol standard and defines the MAC protocol, which can be used to solve the problem of the sharing of wireless LAN channels between competing nodes. The basic way of accessing the MAC protocol is through the distributed coordination function (DCF), which uses carrier sense multiple access with collision avoidance (CSMA/CA), as well as the Request to Send / Clear to Send (RTS/CTS) mechanism, which reduces frame collisions introduced by avoidable hidden node and exposed node problems. This article discusses the hidden node and exposed node problems. NS2 simulation software is used to study and analyse the hidden node problem, and the results are subsequently analysed so as to determine how they may be applied to improve network performance.

Due to the large propagation delay and low data rates of underwater acoustic channel, the design of media access control (MAC) protocols in underwater acoustic sensor networks (UWASNs) faces many challenges. In these circumstances, MAC protocols designed for terrestrial networks cannot be directly used in UWASNs. Moreover, the large propagation delay causes a serious hidden terminal problem for MAC protocols. In this paper, we proposed a novel MAC protocol based on the MACA-BI protocol, which uses receiver driven handshaking mechanism. It is shown that by using adaptive transmission time and adaptive back-off time, our protocol can solve the hidden terminal problem and improve the channel utilization. The results of simulation are given, which shows that our protocol outperforms in network throughput and end to end delay.