Underwater Wireless Sensor Networks: How Do Acoustic Propagation Models Impact the Performance of Higher-Level Protocols?

This work introduces a Medium Access Control (MAC) protocol designed to allow a group of underwater robots that share a wireless communication channel to effectively communicate with each other. The goal of the Underwater Multirobot Cooperative Intervention MAC (UMCI-MAC) protocol presented in this work is to minimize the end to end delay and the jitter. The access to the medium in UMCI-MAC follows a Time Division Multiple Access (TDMA) strategy which is arbitrated by a master, which also has the capability to prioritize the transmission of some nodes over the rest of the network. Two experiments have been carried out with a team of four Autonomous Underwater Vehicles (AUV) in order to compare this protocol with Aloha-CS and S-FAMA MAC protocols used in Underwater Wireless Sensor Networks (UWSN). In the first experiment, the communications and the AUVs have been simulated using UWSim-NET. The objective of this experiment was to evaluate all three protocols in terms of delay, jitter, efficiency, collisions and throughput depending on the size of the data packet and the rate of packet delivery in the application layer for each robot. The results of this experiment proved that UMCI-MAC successfully avoids packet collisions and outperforms the other two protocols in terms of delay, jitter and efficiency. The second experiment consisted of a Hardware In The Loop (HIL) teleoperation of a team of four robots. One of the AUVs was a real BlueROV in a water tank, while the remaining AUVs and the communications were simulated with UWSim-NET. It demonstrates the impact of the MAC protocols in underwater acoustic links. Of the three MAC protocols evaluated in this work, UMCI-MAC was the only one which succeeded in the proposed teleoperation experiment. Thus demonstrating its suitability as a communications protocol in underwater cooperative robotics.

In the realm of underwater wireless communication, vast oceanic expanses often demand large-scale deployment of Underwater Wireless Sensor Networks (UWSNs). UWSNs rely on acoustic communication channels, presenting distinct challenges like prolonged propagation delays, restricted bandwidth, and dynamic topologies. Furthermore, the far-reaching and multi-path nature of acoustic signals results in significant hidden terminal problems and ubiquitous interference between neighboring nodes. Therefore, an efficient medium access control (MAC) protocol is crucial for optimizing UWSN performance. This article proposes IC-MAC, a MAC protocol tailored for UWSNs to avoid collisions and improve network performance. IC-MAC employs distributed clustering to group sensor nodes and the cluster head degree is defined for each node, which is a coefficient that accentuates nodes characterized by a higher incidence of collision associations. To identify interfering nodes and construct an interference-free graph, an interference identification algorithm is proposed. In addition, a heuristic graph coloring technique, guided by particle swarm optimization, allocates time slots efficiently to achieve collision-free transmission scheduling and enhanced spatial reuse. Simulations demonstrate the effectiveness of the IC-MAC protocol in enhancing throughput, reducing delay, and improving packet delivery ratio and energy efficiency. This is achieved through efficient spatial resource utilization and robust management of collisions and interference, specifically tailored for underwater acoustic channels, outperforming existing MAC protocols.

In this paper we propose a simple relay enabled medium access (SRMAC) protocol that enables cooperative relay transmissions. Due to the wireless signal power attenuation with distance, using a relay in a wireless network can make wireless networking more bandwidth efficient at the expense of requiring multiple transmissions for a single packet. Standard MAC protocols such as the IEEE 802.11 MAC protocol, while useable with relaying, however are not designed explicitly for relay communication. When IEEE 802.11 MAC protocol is used for cooperative communication such a relaying, each packet transmission would need to separately contend for the channel via a channel access procedure which can use significant resources (both energy and bandwidth). Because using a single relay requires two transmissions, an efficient medium access control (MAC) protocol that supports two hop transmission is needed. We introduce a protocol, SRMAC, which is a simple cooperative MAC protocol that utilizes information from the physical layer for the MAC operation of relay networks. We consider the bandwidth efficiency of SRMAC protocol considering both the physical layer and MAC layer. The SRMAC protocol includes the possibility of both cooperative transmission and direct transmission. With SRMAC, cooperative transmission (relaying) can be dynamically chosen when it is more beneficial than direct transmission. The SRMAC protocol can improve the throughput by up to 20% compared to conventional MAC protocols.

The availability of low-cost network interface cards (NICs) has made the IEEE 802.11 medium access control (MAC) protocol the de facto MAC standard for wireless mobile ad-hoc networks. Although the IEEE 802.11 MAC protocol is designed to have stations share a single channel in a network, many of the IEEE 802.11 physical (PHY) layer standards define multiple channels and allow the simultaneous, non-interfering use of some of these channels. Therefore, simultaneous communications can occur through different channels, offering the opportunity to increase effectivenetwork capacity. We present an innovative routing protocol that utilizes multiple channels to improve performance in a mobile ad hoc network. The key feature of the protocol is that nodes can effectively use multiple channels for simultaneous useful transmissions, thus improving networkcapacity. The proposed scheme requires minor changes to existing proactive or table-driven routing protocols and no modifications to current the IEEE 802.11 MAC protocol. To mitigate the overhead of periodic updates in proactive routing protocols, the proposed scheme divides the network layer into control and data planes. To demonstrate the multi-channel routing scheme, we extend the OSPFMCDS routing protocol to a multi-channel version, OSPFMCDS- MC or, more simply, OMM. Simulation and experimental results indicate OMM successfully exploits multiple channels to increase network capacity. The protocol allows the network goodput to increase in proportion to the number of available channels, even as the number of nodes and network load increase, in both single-hop and multiple-hop networks. We also present a prototype implementation for experimental validation of the proposed multi-channel routing protocol scheme. The implementation includes the multi-channel routing protocol and a virtual interface module, which acts as a buffer for outgoing packets and performs channel-related functions, such as channel selection and switching, while ensuring portability.

In this paper, we propose a detailed energy survey of the physical, data link, and network layer by analytical techniques. We also show the impact of regular sleep periods on node energy consumption and present a comparison analysis of single-hop vs. multi-hop communications in the energy realm. A detailed energy expenditure analysis of not only the physical layer but also the link and network layer provides a basis for developing new energy efficient wireless sensor networks. Regular, coordinated sleeping extends the lifetime of sensor nodes, but systems can only benefit from sleeping in terms of transmitted packets if the data arrival rate to the system is low. Energy efficiency is the driving motivation for it can be considered the most important factor for wireless sensor networks because of the power constraints set by battery operation. Radio solutions in the lower ISM bands are attractive because of their relatively easy implementation and low power consumption. However, the data rates of these commercial radios are also relatively low, limiting transmittable frame sizes to a few tens of octets along with strict duty cycle requirements. From the analysis we extract key parameters of selected MAC protocols and show that some traditional mechanisms, such as binary exponential backoff, have some inherent problems. We also argue that single-hop communications has up todo% lower energy consumption than multi-hop forwarding within the feasible transmission distances of an ISM radio. Index Terms-Energy efficiency, Wireless sensor net- works, Medium access control (MAC) protocols, multi-hop communications a duty cycIe (Z), (3), which is normally 10% for the 434MHz band and 1% for the 868MHz band. The duty cycle is defined as the ratio, expressed as a percentage, of the maximum transmitter on-time, relative to a one hour period. When a sensor network is expected to work continuously, this duty cycle has to be taken into account and it can affect the energy efficiency of a network. In this paper we perform cross-layer analysis by pre- senting topology, medium access control (MAC) and ra- dio transceiver energy consumption models that work in unison. The hear topology model represents a common network after network layer route discovery has been accomplished. We use an energy consumption model for the transmission and reception of MAC frames originally presented in (4), develop a coordinated sleep group energy consumption model, and analytically investigate the effect of sleep on sensor networks using three MAC protocols. From the analysis we show that although in an ideal scenario multi-hop communications perform better than single-hop communications, realistic energy models and especially the MAC protocol design have a significant impact. We propose a multi-group sleep model for our nanoMAC protocol, and show that reg- ular sleep periods have a significant, energy reducing impact on node energy consumption with low traf!fic rates. The radio transceiver energy model takes into account several important radio parameters and we use the RFM TRlOOO and RFM radio designers guide (5) for realistic transceiver parameters. The main metric used is absolute energy, consumption per useful transmitted bit. This means only the MAC or thc network protocol data unit (PDU) will be considered and all the other communicated bits, headers, control frames, preambles, etc. are considered as overhead. The rest of the paper is organized as follows. Some related work is discussed in Section IT and in Section 111 we look at the radio propagation energy model. Section TV presents the network topology and energy

Over the past few years, mobile networks have emerged as a promising approach for future mobile IP applications. With limited frequency resources, designing an effective MAC (Medium Access Control) protocol is a hot challenge. IEEE 802.11b/g/a/n networks are currently the most popular wireless LAN products on the market [1]. The conventional IEEE 802.11b and 802.11g/a specification provide up to 11 and 54 Mbps data rates, respectively. However, the MAC protocol that they are based upon is the same and employs a CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) protocol with binary exponential back-off. IEEE 802.11 DCF (Distributed Coordination Function) is the de facto MAC protocol for wireless LAN because of its simplicity and robustness [2,3]. Therefore, considerable research efforts have been put on the investigation of the DCF performance over wireless LAN [2]. With the successful deployment of IEEE 802.11a/b/g wireless LAN and the increasing demand for real-time applications over wireless, the IEEE 802.11n Working Group standardized a new MAC and PHY (Physical) layer specification to increase the bit rate to be up to 600 Mbps [3]. The throughput performance at the MAC layer can be improved by aggregating several frames before transmission [3]. Frame aggregation not only reduces the transmission time for preamble and frame headers, but also reduces the waiting time during CSMA/CA random backoff period for successive frame transmissions. The frame aggregation can be performed within different sub-layers. In 802.11n, frame aggregation can be performed either by A-MPDU (MAC Protocol Data Unit Aggregation) or A-MSDU (MAC Service Data Unit Aggregation). Although frame aggregation can increase the throughput at the MAC layer under ideal channel conditions, a larger aggregated frame will cause each station to wait longer before its next chance for channel access. Under errorprone channels, corrupting a large aggregated frame may waste a long period of channel time and lead to a lower MAC efficiency [4]. On the other hand, wireless LAN mobile stations that are defined as the stations that access the LAN while in motion are considered in this chapter. The previous paper analyzed the IEEE 802.11b/g/n MAC performance for wireless LAN with fixed stations, not for wireless LAN with mobile stations [5, 6, 7, 8, 9, 10]. On the contrary, Xi Yong [11] and Ha Cheol Lee [12] analyzed the MAC performance for IEEE 802.11 wireless LAN with mobile stations, but considered only IEEE 802.11 and 802.11g/a wireless LAN specification. So, this chapter summarizes all the reference papers and analyzes the IEEE 802.11b/g/a/n MAC performance for wireless LAN with fixed and mobile stations. In other words, we will present the analytical evaluation of saturation

Power efficient ultra-wideband based wireless communication for wireless body area network applications

A joint MIMO-OFDM transceiver and MAC design for mobile ad hoc networking

Large-sized underwater testbed deployments still pose a number of challenges, first of all the cost of the nodes and of the deploying ships. Therefore, simulation becomes an important tool for the assessment of network performance, and a precious aid to protocol, topology, and deployment design. However, simulations are significant only if the reproduction of acoustic propagation is accurate. To this end, we have joined two well known tools for simulation, namely Bellhop (for acoustic propagation modeling through ray tracing) and ns2-MIRACLE (an event-based network simulator). These tools, together, provide a flexible and customizable environment, fostering more realistic reproduction of propagation, PHY-level behavior, as well as the detailed specification of medium access control, routing, and higher-level protocols. In this paper, we describe our tool, and give an example of its employment in the comparison of three MAC protocols for underwater networks over different kinds of physical layers. The protocols have been specifically chosen to shed some light on the relationship between the complexity of a protocol and the amount of coordination it enables among nodes: in other words, our results show when it is better to rely on plain random access, and when on some form of handshaking (despite the usually greater complexity of handshake-based protocols).

Compared with electromagnetic wave, acoustic wave has great advantages in underwater sensing, which attracts great attention on how it propagates in underwater environment. A variety of types of underwater acoustic propagation models (APMs) have been developed, where the closest to actual underwater acoustic propagation should be selected as in most sensing cases, accurate APM are needed, like matched field processing, geoacoustic inversion, etc. However, selecting by experience is not reliable enough and matching the measured field with the modeled one is time-consuming. In this paper, a convolutional neural network (CNN) classifier is proposed to select appropriate underwater acoustic propagation model (APM) according to sound field collected by a horizontal line array (HLA). The simulated data are generated by five different APMs and the classification accuracy on testing set reaches 95.3%. The correlation and difference between the performance of this CNN-based classifier and the correlation coefficient (CC) of the classified data are discussed, which demonstrate that the CNN-based classifier outperforms the correlation-based classifier. We also validate the performance of the CNN classifier by the data measured in shallow water environment.

ALOHA protocol and its variations are commonly deployed Medium Access Control (MAC) protocols in environments where multiple transmitting devices compete for a medium. Idealized Slotted ALOHA protocol is the most deploy variation in Mobile Ad Hoc Networks (MANETs) environment for example in digital cellular systems such as GSM, RFID and underwater wireless sensor network. In this research paper, the analysis and studies were made with simulation tools to get an illustration of how the Idealized Slotted ALOHA protocol works and to get mathematical results in graphical form in term of throughput and average time delay. These results are then used to compare with the performances of non-persistent CSMA protocol, another MAC protocol that happened to fell under the same category as ALOHA protocols to prove that Idealized Slotted ALOHA protocol outperforms non-persistent CSMA protocol. However, the throughput of Idealized Slotted ALOHA protocol is improvable with the right approaches. In this research paper, the approaches that are used to improve the performance made primarily are by amending the Idealized Slotted ALOHA protocol with capture effect and by increasing the CNR possibility values.

In Underwater Wireless Sensor Network (UWSN); the sensor node is responsible to extract the valuable application based information from underwater environment. The application based information covers the applications like: tactical surveillance, assisted navigation, disaster prevention, offshore exploration, pollution monitoring and oceanographic data collection. The design of routing protocol in underwater environment is one of the challenging issues for researchers. This research article focuses the designing issues of the data forwarding routing protocols based on single path. In this article the designing of 2D and 3D architecture of routing protocols are discussed with their different issues. This article also focuses the analytical approach of proposed routing protocols with different parameters, the simulation scenarios of the single path routing protocols with critical analysis; and the open research issues; will help the researchers to further research in the field of routing protocols for UWSN.

Since cognitive wireless network (CRN) has the characteristic of secondary use, it can enable the device to dynamically access available spectrum without interference to primary users (PUs), which can effectively alleviate contradiction between the lack of spectrum resources and the growing demand for wireless access. However, Medium Access Control (MAC) protocol as CRN core components, can achieve competition access of the licensed spectrum and coordination control, which will maximize spectrum utilization efficiency and network throughput. The contribution of this survey is threefold. First, we analyze the characteristics of the existed multi- channel MAC protocol in CRN; Second, according to the different ways of spectrum access in CRNs, the multi-channel MAC protocols are classified into time-slotted based MAC protocol, control channel based MAC protocol and hybrid MAC protocol, and the paper emphatically analyzed the advantages and disadvantages of these multi-channel MAC protocols; Finally, the paper explores the difficulties and the challenges of multi-channel MAC protocols design in cognitive wireless network.

Cognitive Radio (CR) exploits underutilized licensed spectrums to improve its bandwidth availability. Using CR technology, a node is able to adapt its transmission and reception radio parameters including channel frequency dynamically according to local spectrum availability. For channel access between wireless nodes, a cognitive Medium Access Control (MAC) protocol is necessary to coordinate the CRs. Multi-channel MAC protocol extensions have been proposed in IEEE802.11 to enable a node to operate in multiple channels in order to improve network-wide throughput. These multi-channel MAC protocols have several functions that can be leveraged by cognitive MAC protocols due to their similarities in certain aspects, though the CR has an additional requirement to cope with the existence of licensed users that have higher authority over the channels. Current research in cognitive MAC protocols assumes the availability of a common control channel at all times, which is an approach in the multi-channel MAC protocols. This approach has certain hardware requirements that may not be readily available at CR nodes. Hence, other approached may be necessary. In this paper, various types of multi-channel MAC protocols are reviewed, followed by discussion of their merits and demerits in multi-channel environments. The purpose is to show the additional functionalities and challenges that each multi-channel MAC protocol has to offer and address in order to operate in multihop CR networks. By providing discussion on possible technology leverage from multi-channel to cognitive MAC protocols, we aim to establish a foundation for further research and discussion.

Two important criteria of wireless body area networks (WBANs) are low power consumption and delay. These criteria can be met by designing efficient medium access control (MAC) protocols. In this paper, two TDMA-based MAC protocols are proposed. The first protocol, TM–MAC makes use of only a main radio. The second proposed protocol, TWM–MAC makes use of a WUR alongside the main radio. The two proposed protocols are compared with different categories of standard MAC protocols and it is shown that they outperform the standard ones by improving the power consumption and delay. The TWM–MAC consumes 55% less power consumption than the Scheduled Channel Polling MAC (SCP–MAC) protocol for a high traffic scenario on the high-rate platform while the TM-MAC consumes 85% less power consumption than the SCP–MAC. For a low traffic scenario, the TWM–MAC performs 53.5% better than the SCP–MAC protocol and 77.5% better than the very low power MAC (VLPM) protocol on the high and low-rate platforms respectively. An improvement in delay was observed with the TWM–MAC protocol for high traffic situations. The TWM–MAC protocol surpasses the VLPM protocol by 81.1% in terms of latency for a high traffic scenario and 3.2% for a low traffic scenario.