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34
Choosing the packet size in multi-hop underwater networks
- in Proceedings of IEEE OCEANS 2010
, 2010
"... Abstract—Two MAC layer protocols are considered for multi-hop underwater acoustic networks: Pure CSMA, suitably configured to perform over a long-delay channel, and the Distance-Aware Collision Avoidance Protocol (DACAP), a protocol specifically designed for collision avoidance via a distributed coo ..."
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Abstract—Two MAC layer protocols are considered for multi-hop underwater acoustic networks: Pure CSMA, suitably configured to perform over a long-delay channel, and the Distance-Aware Collision Avoidance Protocol (DACAP), a protocol specifically designed for collision avoidance via a distributed coordination function à la IEEE 802.11. We investigate the impact of packet size on the performance of these two protocols. A comparative analysis, conducted via ns-2 simulations, quantifies throughput efficiency, end-to-end delay and energy-per-bit consumption as functions of the packet size. The results clearly indicate the existence of an optimal packet size for each scenario. The optimal packet size depends on the protocol characteristics, on the offered load, and is heavily influenced by the bit error rate. The results also reveal performance sensitivity to the choice of the packet size for the different protocols (CSMA and DACAP), emphasizing how a wrong selection of the packet size can result in a higher cost to performance. I.
Spatial Reuse in Underwater Acoustic Networks using RTS/CTS MAC Protocols
, 2010
"... Abstract—Using analytic models and simulation results, we examine spatial reuse and the effectiveness of RTS/CTS MAC protocols in underwater acoustic networks. We are not looking at the question of network throughput, which is affected mostly by propagation delay, but rather the protocol’s ability t ..."
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Abstract—Using analytic models and simulation results, we examine spatial reuse and the effectiveness of RTS/CTS MAC protocols in underwater acoustic networks. We are not looking at the question of network throughput, which is affected mostly by propagation delay, but rather the protocol’s ability to prevent collisions. RTS/CTS-based collision-avoidance protocols require successful detection of the handshake packets in order to be effective. This criterion leads to an RTS/CTS effectiveness metric which depends upon channel characteristics such as spreading loss, attenuation, and ambient noise, as well as communication parameters such as the detection threshold and type of modulation. The relatively low spreading losses in underwater acoustic channels allows increased interference from distant interferers,
Remotely Powered Underwater Acoustic Sensor Networks
- IEEE Sensors Journal
, 2012
"... sor Networks (SPUASN) refers to a special configuration within ..."
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sor Networks (SPUASN) refers to a special configuration within
ROPA: A MAC Protocol for Underwater Acoustic Networks with Reverse Opportunistic Packet Appending
"... Abstract—In most existing sender-initiated handshaking based underwater Media Access Control (MAC) protocols, only the initiating sender is allowed to transmit data packets to its intended receiver after the channel has been reserved; none of the potentially backlogged neighbors of the sender can tr ..."
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Abstract—In most existing sender-initiated handshaking based underwater Media Access Control (MAC) protocols, only the initiating sender is allowed to transmit data packets to its intended receiver after the channel has been reserved; none of the potentially backlogged neighbors of the sender can transmit in the duration after the current handshake. Therefore, each of those neighbors must initiate their own handshakes, which incur additional overheads and potentially result in poor channel utilization. In this paper, we present a novel approach to increase the channel utilization by allowing a sender to invite its one-hop neighbors (appenders) to opportunistically transmit (append) their data packets. After the sender finishes transmitting its packets to its own receiver, it can immediately switch its role to receive the incoming appended data packets, which arrive in a packet train manner. This greatly reduces the relative proportion of time spent on control signaling. We refer to this MAC protocol as ROPA – Reverse Opportunistic Packet Appending. From our extensive simulations and comparisons with existing protocols, we show that ROPA significantly increases the channel utilization and offers performance gains in terms of throughput and delay. I.
Unified Simulation and Implementation Software Framework for Underwater MAC Protocol Development
"... Abstract—MAC protocol development for underwater acoustic modem has been an active research area for many years. The primary mode of investigation is through network simulations. Subsequent implementation in modems for testing in sea trials typically involves porting of simulation code into the appr ..."
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Abstract—MAC protocol development for underwater acoustic modem has been an active research area for many years. The primary mode of investigation is through network simulations. Subsequent implementation in modems for testing in sea trials typically involves porting of simulation code into the appropriate programming language and software environment in a modem. Correct porting is critical since, if the modem implementation differs from the simulation code, comparison of sea trial results with simulation results become misleading and the performance observed in simulations might be compromised. One of the challenges associated with the above porting process is to maintain exact algorithmic match in the modem implementation and the simulation code as in many protocols, minor variations in the logic can have significant effects on the protocol behavior. Apart from programming errors in porting, this task can be made difficult if the modem hardware have additional complexities which make one-to-one translation difficult. We have developed a software framework to address this. In this structured framework, identical C code for the MAC protocol runs in both the simulator and the modem. The simulator captures the essential behavior of the modem and uses the same software interfaces as the modem. Since the same code is used with no change, performance comparisons between simulations and sea trials become meaningful. We present a case study using the ARL OFDM modem operating in the 31.25 kHz centre frequency, where one MAC protocol is simulated and also operated with no code changes in the modem. The authors aim to make this framework publically available, whereby other researchers can develop MAC protocols that will run in an underwater modem with no modifications. This framework makes a modem trial an easy step after simulation study. The aim of this paper is to provide an overview of the key aspects of this framework. Index Terms—Underwater, medium access control, MAC, standardization, simulation, implementation I.
MAC Protocols that Exploit Propagation Delay in Underwater Networks
"... Abstract—This paper discusses novel medium access control (MAC) protocols for underwater acoustic networks that utilize propagation delay to increase the network throughput. Traditional MAC design considers propagation delay as undesirable and attempts to mitigate its impact on throughput. The essen ..."
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Abstract—This paper discusses novel medium access control (MAC) protocols for underwater acoustic networks that utilize propagation delay to increase the network throughput. Traditional MAC design considers propagation delay as undesirable and attempts to mitigate its impact on throughput. The essential idea in this paper is to do simultaneous pairwise transmissions and utilize the propagation delay to avoid collisions at the receiver. The throughput and queueing delay performance of the protocols proposed here is superior compared to the corresponding traditional protocols. We discuss static and dynamic variations of time division multiple access (TDMA) based protocols we call Twin-TDMA and Twin-DTDMA. We shall also see how the same concept can be utilized in an ALOHAlike protocol, which we term Twin-ALOHA. The protocols are primarily designed to have utility in large propagation delay underwater networks, where the performance of traditional MAC protocols is significantly degraded due to the large propagation delays. I.
A Multi-band Noise-aware MAC Protocol for Underwater Acoustic Sensor Networks
"... Abstract-We present a MAC protocol for underwater acoustic sensor networks (UASN) able to overcome the shortcomings induced by the temporary presence of noise sources within, or close-by, the region covered by the UASN. Our solution, named NAMAC for Noise-aware MAC protocol, exploits the ability of ..."
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Abstract-We present a MAC protocol for underwater acoustic sensor networks (UASN) able to overcome the shortcomings induced by the temporary presence of noise sources within, or close-by, the region covered by the UASN. Our solution, named NAMAC for Noise-aware MAC protocol, exploits the ability of nodes equipped with multi-band modems to rapidly switch the frequency band used for communications upon detecting an increase of the in-band noise. Neighboring nodes may collectively decide to migrate to a different band and, as soon as the noise source is no longer impairing communications, to switch back to the default one. NAMAC also ensures connectivity across regions operating on different frequency bands induced by a different impact of noise at different locations. Additionally, if nodes are equipped with acoustic sensors able to monitor low frequencies, i.e., in the range from 0 to 5 kHz, NAMAC can exploit this capability to detect the approaching of a noisy vessel in advance, since noise at low frequencies is audible at larger distances. In this way, nodes can be pre-alerted for a band switch. We perform an extensive comparative performance evaluation of NAMAC based on ns-2 MIRACLE simulations. The noise frequency spectrum used in our simulations reproduces that of existing powerboats. Our performance evaluation shows that NAMAC is able to significantly outperform existing noise unaware MAC protocols that use a single band, increasing the network reliability in the presence of temporary noise sources like passing-by noisy vessels.
IEEE JOURNAL OF OCEANIC ENGINEERING 1 Throughput of Networks with Large Propagation Delays
"... Abstract—Propagation delays in underwater acoustic networks can be large as compared to the packet size. Conventional medium access control protocol design for such networks focuses on mitigation of the impact of propagation delay. Most proposed protocols to date achieve, at best, a throughput simil ..."
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Abstract—Propagation delays in underwater acoustic networks can be large as compared to the packet size. Conventional medium access control protocol design for such networks focuses on mitigation of the impact of propagation delay. Most proposed protocols to date achieve, at best, a throughput similar to that of the zero propagation delay scenario. In this paper, we systematically explore the possibility that propagation delays can be exploited to make throughput far exceed that of networks without propagation delay. Under the assumptions of the protocol model in a single collision domain for a half-duplex unicast network, we show that the upper bound of throughput in an N-node wireless network with propagation delay is N/2. We illustrate network geometries where this bound can be achieved and study transmission schedules that help achieve it. We show that for any network, the optimal schedule is periodic and present a computationally efficient algorithm to find good schedules. Finally, we show that N-node network geometries that achieve throughput close to the N/2 bound exist for any N and present a lower bound on achievable maximum throughput for bounded geometries. This paper chiefly endeavors to explore the impact and potential of nonzero propagation delays on network throughput. We believe that the novel observations in this paper could motivate further research into this area, especially random access networks with large propagation delay, with a fundamentally changed outlook on maximum achievable throughput. This could lead to novel scheduling and network configuration approaches with applications in underwater and satellite networks. Index Terms—Underwater networks, large propagation delays, throughput bounds, network geometry, interference alignment by delay, transmission schedules. I.
Short Paper: A Reservation MAC Protocol for Ad-Hoc Underwater Acoustic Sensor Networks ABSTRACT
"... In this paper we propose a new MAC protocol for ad-hoc underwater acoustic sensor networks that segregates the available bandwidth into a (small) control channel and a (majority bandwidth) data channel. Reservations for main channel time are made by transmission of Request-to-Send(RTS) packets on th ..."
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In this paper we propose a new MAC protocol for ad-hoc underwater acoustic sensor networks that segregates the available bandwidth into a (small) control channel and a (majority bandwidth) data channel. Reservations for main channel time are made by transmission of Request-to-Send(RTS) packets on the control channel. The effects of channel segregation are explored and simulation results are presented. We find that such a reservation MAC generally achieves good channel utilization with an optimal control channel bandwidth for a given data bandwidth. Categories and Subject Descriptors
