Modified Medium Access Control Protocol Research Articles

MCA-MAC: Modified Cooperative Access MAC Protocol in Wireless Sensor Networks

Throughput, energy efficiency and average packet delivery delay are some of the most crucial metrics that should be considered in Wireless Sensor Networks (WSNs). This paper proposes a modified Medium Access Control (MAC) protocol for WSNs, called (MCA-MAC). MCA-MAC aims to improve the previous metrics and thus the overall performance of WSNs through using cooperative communication. It enables source nodes from using intermediate nodes as relays to send their data through them to the access point. MCA-MAC protocol is also acting as a cross layer protocol where the best end-to-end path between the source and destination is found through an efficient algorithm. Mathematical analysis demonstrates that MCA-MAC protocol can determine the optimal relay node that has the minimum transmission time for the given source-destination pair. Using Multi-Paradigm Programming Language (MATLAB) simulation environment, this paper estimates MCA-MAC protocol performance in terms of system throughput, energy efficiency and delay. The results show that MCA-MAC protocol outperforms the existing scheme called Throughput and Energy aware Cooperative MAC protocol (TEC-MAC) protocol under ideal and dynamic channel conditions. Under ideal conditions, MCA-MAC protocol achieved throughput, and energy efficiency improvements of 12%, and 50% respectively, more than TEC-MAC protocol. While the packet delay through using MCA-MAC has been decreased by about 48% less than TEC-MAC protocol.

Exploiting anomalous slots for multiple channel access in IEEE 802.11 networks

The execution process of the IEEE 802.11 distributed coordination function (DCF) exhibits non-accessible time slots preceded by transmissions (successful and collision). Those slots are “anomalous” due to the inaccessibility of channel for transmission. For improving network performance, a station attempts to successfully transmit more frames in less time, which, in turn, increases the number of anomalous slots. Consequently, increased number of anomalous slots results in reduced performance improvement. In this paper, we exploit the anomalous slots for improving the performance of the DCF protocol. The anomalous slots allow the stations to know the channel status much ahead of the slot's actual time of occurrence. By leveraging the channel status, each station schedules anomalous transmissions during anomalous slots. We integrate the concept of anomalous transmission with the DCF protocol for designing a modified medium access control protocol, namely ANT, for wireless local area networks (WLANs). Following Felemban and Ekici's modeling approach, we analyze the theoretical performance of the ANT protocol in WLANs. Analytical results show that the ANT protocol decreases the average medium access delay by 80% and 65%, respectively, under the basic and the RTS/CTS access modes compared with that in the DCF protocol, while it increases the network throughput as well.

An Evolutionary MAC Protocol based on FPRP for Decreasing Delay

Five-Phase Reservation Protocol (FPRP) is a single channel, Time Division Multiplex Access (TDMA) based broadcast scheduling protocol for Ad Hoc network. A modified Medium Access Control (MAC) protocol based on FPRP for decreasing packet delay is proposed in this paper. In FPRP, There are quite a lot of reservation cycles in slots is not fully used, especially in latter slots, for the reason that the number of contention nodes decrease in latter slots. By modifying the frame structure of the Five Phase Reservation Protocol (FPRP), the time of slots assignment can be greatly decreased in the modification FPRP (MFPRP). The simulation results reveal that the reduction in reservation cycles doesn’t affect the throughput in network obviously.

A MAC protocol to support hybrid antennas in a wireless LAN

Hybrid Distributed Coordination Function (HDCF), a modified medium access control protocol of IEEE 802.11 standard, is proposed in this paper to support both smart adaptive array antennas and normal omni-directional antennas simultaneously in one wireless LAN. Omni-directional antennas follow the standard Distributed Coordination Function (DCF) and smart antennas follow the Directional DCF (DDCF). The proposed DDCF is based on Hybrid Virtual Carrier Sense (HVCS) mechanism, which includes Omni-directional Request-To-Send/Clear-To-Send (ORTS/OCTS) hand-shake mechanism and directional data transmission. HDCF is compatible with DCF. When a node transmits in a directional beam, the other nodes can multiplex the physical channel. Hence, HDCF supports Space Division Multiple Access (SDMA). Simulation results show that HDCF can support hybrid antennas effectively and provide much higher network throughput and lower delay and jitter than DCF does.

Directional distributed co-ordination function – a medium access control protocol to simultaneously support both omni-directional and smart antennas in a same WLAN cell

Directional distributed co-ordination function (D-DCF), a modified medium access control protocol of IEEE 802.11, is proposed to support hybrid antennas such as smart adaptive array antennas and normal omni-directional antennas, in one wireless local area network cell. Nodes equipped with smart antennas follow D-DCF and nodes equipped with normal antennas follow DCF. D-DCF based on a hybrid virtual carrier sense mechanism maintains compatibility with DCF. In D-DCF, before sending any data-frames, the sender and receiver node transmit a pilot sequence by means of an omni-directional request-to-send/clear-to-send handshake mechanism. Based on the pilot, the directional beam can be formed by the smart antenna. Then the node can transmit its data-frame in the directional mode. The other nodes save the transmission time between the sender and receiver in the omni-directional mode in their network allocation vectors. When the sender and receiver communicate in the directional mode, the other nodes can access the channel to send their data-frames. Hence, D-DCF supports space division multiplexing. Moreover, D-DCF fully supports time division duplex, namely both the forward and backward transmission in one access period. Simulation results show that D-DCF can support the hybrid antenna system effectively and provide much higher network throughput, lower delay, jitter and packet-loss-rate than DCF does.