Cross Layer Based Cooperative Communication Protocol for Improving Network Performance in Underwater Sensor Networks

For underwater sensor networks (USNs), cooperative communications have been introduced to improve network performance with the help of relay nodes. The previous cooperative communications select the best relay node on a hop-by-hop basis. Therefore, they have limitations in improving performance. In order to get better performance, a cooperative communication protocol based on  the cross layer is proposed in this paper. The proposed protocol uses the information provided by a routing protocol at the network layer for the erroneous data packet delivery. It selects one with the minimum routing cost among relay candidate nodes. The routing protocol in the selected relay node provides the MAC layer with the address of the next hop node on the path to the sink node. Then, the MAC layer in the selected relay node forwards the erroneous data packet to the next hop node rather than a receiver node. Performance studies are carried out through simulation. Simulation results show that the proposed protocol has about 21.8% lower average delay and about 14.4% lower average number of nodes passed than the previous protocol, regardless of the maximum transmission range

Dual Polling Protocol for Improving Performance in Wireless Ad Hoc Networks

An ad hoc network is based on a distributed coordination function (DCF) to transmit data packets through channel contentions. In DCF, when the number of stations increases, performance degrades considerably because of extremely high collision probability. To improve performance, a distributed point coordination function (DPCF) protocol was proposed. In this protocol, stations operate as in DCF to obtain channel access rights. When a station obtains access rights, it polls all neighboring stations by using point coordination function (PCF). The polled stations then transmit their data packets without channel contentions. However, this protocol aggravates the issue of hidden terminals and causes channel wastage. To solve these problems, we propose a protocol in which a station polls stations in limited areas as opposed to every station in its transmission range. In addition, it polls only stations with data packets. The proposed protocol lowers the probability of collision and improves network performanc

Fair Share Scheme of Delay Margin for Real-Time Multimedia Delivery in Wireless LANs

Abstract: Multimedia traffic is expected to be one of the most important traffic types in wireless LANs. However, delivering real-time multimedia traffic over wireless LANs faces many challenges since the traffic has strict quality of service (QoS) requirements on delay and loss. Especially, guaranteeing the delay bound is critical for real-time multimedia traffic. Multimedia data packets in the queue of stations may have different delay bounds. If a station uses much channel time to transmit a data packet with long delay bound, the other packets in the queue are delayed since in the IEEE 802.11 medium access control (MAC) protocol, the scheduling of packet transmissions is first in first out (FIFO). Therefore, data packets with short delay bound would be discarded due to breaking their delay bound. This results in network performance degradation. Also, data flows with long delay bound have higher performance than data flows with short one. To overcome these limitations, we propose a fair share scheme based on delay bound. It is a strategy that the residual delay bound is equally distributed among data packets. The proposed scheme limits the number of retransmissions attempts of data packets by considering the residual delay bounds of all the data packets in the queue. Performance of the proposed scheme is investigated by simulation. Our results show that the proposed scheme is more effective and alleviates the limitations

MPT-MAC: Multi-Packet Transmission MAC Protocol in UWASNs

Recently, there are lots of ongoing researches for underwater acoustic sensor networks (UWASNs). Unlike terrestrial wireless sensor networks which use radio waves, UWASNs communicate by using acoustic waves. The acoustic waves have long propagation delay. Therefore, media access control (MAC) for terrestrial wireless sensor networks does not operate appropriately. Most of recent researches for UWASNs are targeting simple network topology which consists of a single gateway and a number of nodes. However, there are mobile objects, such as autonomous underwater vehicles (AUVs) or multiple gateways, to guarantee reliability of the system in practical UWASNs. Therefore, data transmission with various routes from each node happens. Under this network environment, we propose a new MAC protocol, which can reduce frequent channel contentions among nodes arose by various transmission routes. A Sender transmits single RTS packet to multiple receivers, in order to reserve channel with them, and then it transmits data to them. Therefore, channel contention time for data transmission decreases and network performance improves. In this paper, we evaluate the proposed protocol, by comparing it to existing MAC for UWASNs through the simulatio

Efficient Multicast Scheme based on Hybrid ARQ and Busy Tone for Multimedia Traffic in Wireless LANs

Multicast in wireless LANs (Local Area Networks) is very useful for transmitting multimedia traffic from a sender to a group of receivers. The IEEE 802.11 WLAN MAC (Medium Access Control) layer does not support reliable multicast since, for multicast transmissions, it has no control packets such as the RTS, CTS, and ACK, which are used for unicast transmissions. Several protocols have been proposed to provide reliable multicast transmissions. However, they are not efficient for IEEE 802.11 WLANs due to the large number of packet transmissions and the excessive control overhead caused by the use of a large number of control packets in the error recovery process. In this paper, we propose a simple and effective scheme. The proposed scheme combines FEC (Forward Error Correction) and ARQ (Automatic Repeat reQuest) to reduce a large number of packet transmissions and to provide data reliability in the IEEE 802.11 WLANs multicast environment. It then uses busy tones to improve efficiency by reducing the excessive control overhead. Performance evaluation is conducted using both numerical analysis and simulation. The results show that the proposed scheme has good performance in terms of normalized throughput and average delay

Efficient Multicast Scheme based on Hybrid ARQ and Busy Tone for Multimedia Traffic in Wireless LANs

Abstract: Multicast in wireless LANs (Local Area Networks) is very useful for transmitting multimedia traffic from a sender to a group of receivers. The IEEE 802.11 WLAN MAC (Medium Access Control) layer does not support reliable multicast since, for multicast transmissions, it has no control packets such as the RTS, CTS, and ACK, which are used for unicast transmissions. Several protocols have been proposed to provide reliable multicast transmissions. However, they are not efficient for IEEE 802.11 WLANs due to the large number of packet transmissions and the excessive control overhead caused by the use of a large number of control packets in the error recovery process. In this paper, we propose a simple and effective scheme. The proposed scheme combines FEC (Forward Error Correction) and ARQ (Automatic Repeat reQuest) to reduce a large number of packet transmissions and to provide data reliability in the IEEE 802.11 WLANs multicast environment. It then uses busy tones to improve efficiency by reducing the excessive control overhead. Performance evaluation is conducted using both numerical analysis and simulation. The results show that the proposed scheme has good performance in terms of normalized throughput and average delay