Masaki Bandai

A MAC Protocol with Directional Antennas for Deafness Avoidance in Ad Hoc Networks

Directional antennas are expected to provide significant improvements over omni-directional antennas in wireless ad hoc networks. Directional MAC protocols, however, introduce new kinds of problems arising from directivity. One major problem is deafness, caused by a lack of state information from neighbor nodes (i.e., idle or busy). This paper proposes DMAC/DA (Directional MAC with Deafness Avoidance) to overcome the deafness problem. In DMAC/DA, WTS (Wait To Send) frames are transmitted by the transmitter and the receiver after the successful exchange of directional RTS (Request To Send) and CTS (Clear To Send) to notify the on-going communication to potential transmitters that may experience deafness. Furthermore, DMAC/DA is enhanced by the next packet notification to distinguish transmitters from neighbors. We evaluate our protocol through extensive simulation study with different values of parameters such as the number of flows, data size and beamwidth. The experimental results show that DMAC/DA outperforms existing directional MAC protocols, such as DMAC (Directional MAC) and MDA (MAC protocol for Directional Antennas), in terms of throughput, RTS failure ratio, and control overhead.

A Receiver-Initiated Directional MAC Protocol for Handling Deafness in Ad Hoc Networks

Recently, several MAC protocols using directional antennas, typically referred to as directional MAC protocols, have been proposed for wireless ad hoc networks. Although directional transmissions are expected to provide significant improvements, directional MAC protocols introduce new kinds of problems. One such problem is deafness. Deafness is caused when a transmitter repeatedly attempts to communicate with its intended receiver, but it fails because the receiver has its beam pointed towards a direction away from the transmitter. This paper proposes RI-DMAC (Receiver-Initiated Directional MAC) to address the issue of deafness in directional MAC protocols. RI-DMAC is a combination of sender-initiated and receiver-initiated operations. The sender-initiated mode is the default mode and the receiverinitiated mode is triggered when the transmitter experiences deafness. In RI-DMAC, each node maintains a polling table and polls a potential deafness node using the RTR (Ready To Receive) frame after the completion of every dialog. The experimental results show that RI-DMAC improves throughput and fairness performance compared to existing directional MAC protocols.

Tradeoffs among Delay, Energy and Accuracy of Partial Data Aggregation in Wireless Sensor Networks

Due to the Recent development in wireless technology, wireless sensor networks attract researchers’ attention because of their applicability in many fields for effective collection of sensing data with low cost. Wireless sensor networks have many applications; some of the applications are military application, environmental application and flood detection. For example, in an environmental application for forest fire detection, the sensor nodes sense the fire information, then transmit or relay the information to base station in a multi-hop way. In wireless sensor networks, energy saving is critical issue as sensor nodes are battery-powered. Here we propose, partial data aggregation as one of the energy saving technique. In this paper, we analyze the tradeoffs among communication delay, energy consumption, and data accuracy of the partial data aggregation technique and discuss the results. First, we analyze the partial data aggregation with Markovian chain; analytical result shows that, non-aggregation method suffers large energy consumption while full aggregation suffers long transmission delay. From the analysis results, we find that the proposed partial aggregation method WRP (Waterfalls Random partial aggregation) can trade off energy consumption and transmission delay. Thus, we discuss the tradeoffs among data accuracy, transmission delay and energy consumption with different criteria and parameters. The results show that we could control the significance of transmission delay, energy consumption and data accuracy by tradeoffs index (TOI). We also analyze the several applications of wireless sensor networks with different significance based on the TOI. From the observed results, we found that we could set the significance of transmission delay, energy consumption and data accuracy for different applications based on different criteria TOI. Thus, by evaluating and comparing the criteria with different data generation rate as well as aggregation factor, we get the least TOI value, which denotes the desired tradeoffs among them.

A directional hidden terminal problem in ad hoc network MAC protocols with smart antennas and its solutions

Smart antennas are expected to enhance scalability in ad hoc networks. This paper describes the evaluations of three directional MAC protocols, DMAC, MMAC, and SWAMP, as well as the IEEE 802.11 DCF omni-directional protocol in a multi-hop transmission environment. These evaluations address the problem that performance strongly depends on the route topology between the source and destination, referred to as the directional hidden terminal problem. After analyzing this problem, we propose three MAC level solutions. The MAC solutions are NAV indicators, i.e. HCTS, BRTS, and RCTS, which indicate on-going communications to a directional hidden terminal to set NAV. Based on simulated results, we show that all the proposed MAC solutions could improve the throughput performance

RI-DMAC: a receiver-initiated directional MAC protocol for deafness problem

Although the use of directional antennas in ad hoc networks is expected to provide significant improvements, directional MAC protocols inherently introduce new kinds of problems. Deafness is one of the major problems caused when a transmitter repeatedly attempts to communicate with its intended receiver, but it fails because the receiver has its beam pointed away from the transmitter. This paper proposes Receiver-Initiated Directional MAC (RI-DMAC) to handle the deafness problem. RI-DMAC is a combination of sender- and receiver-initiated operations. The sender-initiated mode is the default mode and the receiver-initiated mode is triggered when the transmitter experiences deafness. Each node maintains a polling table and polls a deafness node using the Ready to Receive (RTR) frame after the completion of every dialogue. Simulation results show that RI-DMAC outperforms other directional MAC protocols (e.g. Basic DMAC and Circular RTS MAC) in terms of throughput, fairness, overhead and packet drop ratio.

A MAC protocol for directional hidden terminal and minor lobe problems

Recently, several directional MAC (medium access control) protocols have been proposed for wireless ad hoc networks. Directional antennas have significant potentials to improve network performance. However, these directional MAC protocols also have problems which do not exist when using omni-directional antennas. One of the problems is the directional hidden terminal problem. This problem is caused by the difference of the antenna gain between the omni-directional antenna and directional antenna. In addition, a practical antenna has side and back lobes. These minor lobes have non-negligible effects on the interference in network nodes. In this paper, we propose a directional MAC protocol called DMAC-PCDR (directional MAC with power control and directional receiving) that mitigates the interference caused by directional hidden terminals and minor lobes. DMAC-PCDR has two features. First, the nodes rotate directionally receiving antenna beams in an idle state. Second, the proposed directional MAC protocol has three access modes and uses these modes depending on the location information. The simulation results show that DMAC-PCDR improves throughput performance.

Directional NAV indicators and orthogonal routing for smart antenna based ad hoc networks

Smart antennas are expected to enhance scalability in ad hoc networks. This paper at first evaluates three directional MAC protocols, DMAC, MMAC and SWAMP as well as the omni-directional protocol IEEE 802.11 DCF in multi-hop transmission environment. The evaluations address the problem that the performance strongly depends on the topology of routes between sources and destinations, referred to as a directional hidden terminal problem. After analyzing the problem, we propose three MAC level solutions and one routing level solution. The MAC solutions are directional NAV indicators, which are BRTS, RCTS and HCTS to indicate on-going communications to a directional hidden terminal to set directional NAV. On the other hand, the routing level solution is orthogonal routing protocol (ORP). ORP is a DSR based on-demand routing protocol and it prevents adjacent links to be in straight lines. As computer simulated results, we show that HCTS can improve the throughput performance.

Energy Efficient MAC Protocol with Power and Rate Control in Multi-Rate Ad Hoc Networks

In this paper, a novel medium access control (MAC) protocol with transmission power and transmission rate control in multi-rate ad hoc networks is proposed to realize high energy efficient data transmission. In the proposed protocol, each node prepares a table that includes energy efficiency in all combinations of transmission power and rate. By exchanging of control frames and looking up the transmission power and rate table, direct and relay transmission sequences are used arbitrarily. When relay transmission by intermediate node between sender and receiver is more effective in terms of power consumption, relay sequence is adopted instead of direct transmission. We show that the proposed protocol can realize high energy efficient data transmission via computer simulations.

DispersiveCast: Dispersive Packets Transmission to Multiple sinks for Energy Saving in Sensor Networks

This paper proposes two schemes for wireless sensor networks with multiple sinks in order to save battery energy and to improve network lifetime performance. In these schemes, each sensor node transmits sensing data to randomly chosen sink according to the sending rates. These schemes are referred to as DispersiveCast. The first decentralized scheme called B-DOP scheme (basic DispersiveCast of packet), enables each sensor node to derive locally the sending rate by the number of hops to sinks. The second one is O-DOP scheme (optimal DispersiveCast of packet) that is partially centralized than B-DOP. In O-DOP, sinks send the information to nodes so as for them to calculate the optimal sending rates. DispersiveCast is effective when the generate rate of sensing data at every sensor node geographical nonuniformity. In such a situation, batteries of nodes in the specific area deplete fast and others late, which causes partial depletion of the entire network. As a result, network lifetime can not be extended sufficiently. We evaluate the DispersiveCast schemes by simulations for several network topologies and show that DispersiveCast scheme prolongs the network lifetime compared with the conventional nearest sink scheme, especially O-DOP can achieve 1.5 times longer

Split Multi-Path Routing Protocol with Load Balancing Policy (SMR-LB) to Improve TCP Performance in Mobile Ad Hoc Networks

In this paper, we propose Split Multi-path Routing protocol with Load Balancing policy (SMR-LB) to improve TCP performance in mobile ad hoc networks. In SMR-LB, each intermediate node records how many primary paths are attempted to construct as well as which source nodes attempt to construct the primary path. Each intermediate node decides which primary path should be constructed by using the primary path and the source node ID information. As a result, SMR-LB can balance the loads and so reduce the probability of congestion and avoid the continuous link breakage time between the specific source and destination pair. Computer simulation results show that SMR-LB can improve TCP performance compared with the conventional protocols.