QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Recent advances in wireless technology have brought us closer to the vision of pervasive computing where sensors/actuators can be connected through a wireless network. Due to cost constraints and the dynamic nature of sensor networks, it is undesirable to assume the existence of base stations connected by a wired backbone. In this paper, we present a network architecture suitable for sensor networks along with a medium access control protocol based on earliest deadline first. <s> BIB001 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Large-scale wireless sensor networks represent a new generation of real-time embedded systems with significantly different communication constraints from traditional networked systems. This paper presents RAP, a new real-time communication architecture for large-scale sensor networks. RAP provides convenient, high-level query and event services for distributed micro-sensing applications. Novel location-addressed communication models are supported by a scalable and light-weight network stack. We present and evaluate a new packet scheduling policy called velocity monotonic scheduling that inherently accounts for both time and distance constraints. We show that this policy is particularly suitable for communication scheduling in sensor networks in which a large number of wireless devices are seamlessly integrated into a physical space to perform real-time monitoring and control. Detailed simulations of representative sensor network environments demonstrate that RAP significantly reduces the end-to-end deadline miss ratio in the sensor network. <s> BIB002 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> The traffic-adaptive medium access protocol (TRAMA) is introduced for energy-efficient collision-free channel access in wireless sensor networks. TRAMA reduces energy consumption by ensuring that unicast, multicast, and broadcast transmissions have no collisions, and by allowing nodes to switch to a low-power, idle state whenever they are not transmitting or receiving. TRAMA assumes that time is slotted and uses a distributed election scheme based on information about the traffic at each node to determine which node can transmit at a particular time slot. TRAMA avoids the assignment of time slots to nodes with no traffic to send, and also allows nodes to determine when they can become idle and not listen to the channel using traffic information. TRAMA is shown to be fair and correct, in that no idle node is an intended receiver and no receiver suffers collisions. The performance of TRAMA is evaluated through extensive simulations using both synthetic- as well as sensor-network scenarios. The results indicate that TRAMA outperforms contention-based protocols (e.g., CSMA, 802.11 and S-MAC) as well as scheduling-based protocols (e.g., NAMA) with significant energy savings. <s> BIB003 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> A wireless sensor network consists of many energy-autonomous microsensors distributed throughout an area of interest. Each node monitors its local environment, locally processing and storing the collected data so that other nodes can use it. To optimize power consumption, the Swiss Center for Electronics and Microtechnology has developed WiseNET, an ultralow-power platform for the implementation of wireless sensor networks that achieves low-power operation through a careful codesign approach. The WiseNET platform uses a codesign approach that combines a dedicated duty-cycled radio with WiseMAC, a low-power media access control protocol, and a complex system-on-chip sensor node to exploit the intimate relationship between MAC-layer performance and radio transceiver parameters. The WiseNET solution consumes about 100 times less power than comparable solutions. <s> BIB004 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> This paper proposes S-MAC, a medium access control (MAC) protocol designed for wireless sensor networks. Wireless sensor networks use battery-operated computing and sensing devices. A network of these devices will collaborate for a common application such as environmental monitoring. We expect sensor networks to be deployed in an ad hoc fashion, with nodes remaining largely inactive for long time, but becoming suddenly active when something is detected. These characteristics of sensor networks and applications motivate a MAC that is different from traditional wireless MACs such as IEEE 802.11 in several ways: energy conservation and self-configuration are primary goals, while per-node fairness and latency are less important. S-MAC uses a few novel techniques to reduce energy consumption and support self-configuration. It enables low-duty-cycle operation in a multihop network. Nodes form virtual clusters based on common sleep schedules to reduce control overhead and enable traffic-adaptive wake-up. S-MAC uses in-channel signaling to avoid overhearing unnecessary traffic. Finally, S-MAC applies message passing to reduce contention latency for applications that require in-network data processing. The paper presents measurement results of S-MAC performance on a sample sensor node, the UC Berkeley Mote, and reveals fundamental tradeoffs on energy, latency and throughput. Results show that S-MAC obtains significant energy savings compared with an 802.11-like MAC without sleeping. <s> BIB005 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Energy conservation is a primary concern in sensor networks. Several MAC protocols have been proposed to address this concern. However, the tradeoff between power consumption and latency has not been thoroughly studied. In this paper, we propose a sensor medium access control protocol with dynamic duty cycle, DSMAC, which achieves a good tradeoff between the two performance metrics without incurring much overhead. Moreover, DSMAC is able to adjust its duty cycle with varying traffic conditions without assuming any prior knowledge of application requirements. Both analytical and simulation results have been presented in this paper. <s> BIB006 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Most of the MAC protocols proposed for wireless sensor networks assume sensors to be stationary after deployment. This usually provides very bad network performance in scenarios involving mobile sensors. Handling mobility in wireless sensor networks in an energy-efficient way is a new challenge. Techniques developed for other mobile networks, such as mobile phone or mobile ad hoc networks, cannot be applicable, as in these networks, energy is not a very critical resource. The paper presents a new adaptive mobility-aware MAC protocol for sensor networks (MS-MAC). The protocol uses any change in received signal level as an indication of mobility and, when necessary, triggers the mobility handling mechanism. In this way, the new mobility-aware MAC protocol can work in a very energy-efficient way when the network is stationary, whereas it can maintain some level of network performance when there are mobile sensors. <s> BIB007 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> In this paper, we propose TA-MAC, a traffic load adaptive Medium Access Control protocol for wireless sensor network. TA-MAC modified the contention window mechanism of S-MAC. It adjusts the initial contention window according to the current traffic load to reduce the collision probability and employs a fast backoff scheme to reduce the time for idle listening during backoff procedure, which both reduce the energy consumption. Simulation results show that TA-MAC outperforms S-MAC. <s> BIB008 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Numerous MAC protocols have been proposed for stationary wireless sensor networks (WSNs). However, there have been very few approaches proposed to make the MAC layer in WSNs suitable for mobile scenarios. We propose a new MAC layer protocol called MOBMAC to support mobility in WSNs. MOBMAC uses an adaptive frame size approach to overcome the effect of frame losses caused by the Doppler shifts in mobile scenarios. An extended Kalman filter (EKF) is used to predict the frame size for each transmission, which enhances the energy efficiency of the system and minimizes latencies. Our study shows that under mobile scenarios, the MOBMAC reduces energy consumption by 60% and shows decrease of 25% in latency in comparison with the well known base protocol $SMAC. Our study also includes the contribution of a more realistic physical layer implementation model in ns-2, which processes the received frame based not only on the fading characteristics of the signal but also on the SNR and relative velocity between the communicating sensor nodes. <s> BIB009 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> A significant amount of research efforts have been done to improve the energy efficiency of wireless sensor network (WSN). However, not much has been done to optimize the Quality of Services (QoS) of WSN. Actually, energy efficiency should be jointly optimized with QoS to make WSN useful. In this paper, we develop an integrated adaptive wireless transmission system for WSN to meet the QoS requirements in an energy-aware fashion. The QoS requirements in the application layer, the modulation and transmission schemes in the data link layer and physical layer are jointly analyzed and integrated into a single framework. In this framework, the cluster-based protocol is used, where the cluster heads form a multi-hop backbone. The intra-cluster QoS performance and inter-cluster QoS performance are both analyzed. Based on the results, the overall energy consumption and QoS in terms of BER performance, end-to-end transmission latency and packet loss ratio are modelled by the communication parameters of the cluster heads including the modulation level (bits per symbol) and transmit power. According to the model, a centralized off-line protocol is designed in the integrated framework to adjust the communication parameters of the cluster heads for fixed QoS provisioning. And a distributed online protocol is also designed for dynamic QoS provisioning. Extensive simulation results under various experimental settings demonstrate the energy-saving performance of the proposed integrated system. The ability to adapt to time-varying delivery quality requirements is also tested. <s> BIB010 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Envisioning a new generation of sensor network applications in healthcare and workplace safety, we seek mechanisms that provide timely and reliable transmissions of mission-critical data. Inspired by the physics in magnetism, we propose a simple diffusion-based data dissemination mechanism, referred to as the magnetic diffusion (MD). In that, the data sink, functioning like the magnet, propagates the magnetic charge to set up the magnetic field. Under the influence of the magnetic field, the sensor data, functioning like the metallic nails, are attracted towards the sink. We compare MD to the state-of-the-art mechanisms and find that MD: (1) performs the best in timely delivery of data, (2) achieves high data reliability in the presence of network dynamics, and yet (3) works as energy efficiently as the state of the art. These suggest that MD is an effective data dissemination solution to the mission-critical applications. <s> BIB011 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> In this paper, we present a novel packet delivery mechanism called Multi-Path and Multi-SPEED Routing Protocol (MMSPEED) for probabilistic QoS guarantee in wireless sensor networks. The QoS provisioning is performed in two quality domains, namely, timeliness and reliability. Multiple QoS levels are provided in the timeliness domain by guaranteeing multiple packet delivery speed options. In the reliability domain, various reliability requirements are supported by probabilistic multipath forwarding. These mechanisms for QoS provisioning are realized in a localized way without global network information by employing localized geographic packet forwarding augmented with dynamic compensation, which compensates for local decision inaccuracies as a packet travels towards its destination. This way, MMSPEED can guarantee end-to-end requirements in a localized way, which is desirable for scalability and adaptability to large scale dynamic sensor networks. Simulation results show that MMSPEED provides QoS differentiation in both reliability and timeliness domains and, as a result, significantly improves the effective capacity of a sensor network in terms of number of flows that meet both reliability and timeliness requirements up to 50 percent (12 flows versus 18 flows). <s> BIB012 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Long propagation delays and low bit rates of underwater acoustic networks make these systems fundamentally different from the packet radio networks. As a consequence, many of the network protocols designed for radio channels are either not applicable, or have extremely low efficiency over underwater acoustic channels. These facts necessitate a dedicated design of protocols for an underwater acoustic network. A medium access control (MAC) protocol suitable for an underwater acoustic network is proposed and analyzed. The protocol is based on a channel access discipline called floor acquisition multiple access (FAMA) which combines both carrier sensing (CS) and a dialogue between the source and receiver prior to data transmission. During the initial dialogue, control packets are exchanged between the source node and the intended destination node to avoid multiple transmissions at the same time. Special attention is paid to the networks that are not fully connected, in which nodes can be hidden from each other. The new protocol uses time slotting and is thus called slotted FAMA. Time slotting eliminates the need for excessively long control packets, thus providing savings in energy. Protocol performance in throughput and delay is assessed through simulation of a mobile ad hoc underwater network, showing the existence of optimal power level to be used for a given user density. <s> BIB013 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Wireless sensor networks have been widely used in many important fields. Medium Access Control (MAC) protocols have a significant effect on the function and performance of sensor networks. At present, most MAC protocols use the same transmission power when sensor nodes send packets. However, the deployment of the sensor nodes is asymmetrical in wireless sensor networks, which will bring more energy consumption and unnecessary collisions. By jointing the MAC layer and physical layer of the senor nodes, and based on Sensor MAC (SMAC) [1] protocol, we propose a transmission power control MAC protocol in wireless sensor networks (transmission Power control in SMAC, PSMAQ. The simulation results show that, compared with the SMAC protocol, our protocol has improved a lot in the delay of packets, reception rate, energy consumption and throughput of the networks. <s> BIB014 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> With more and more wireless devices being mobile, there is a constant challenge to provide reliable and high quality communication services among these devices. In this paper, we propose a link availability-based QoS-aware (LABQ) routing protocol for mobile ad hoc networks based on mobility prediction and link quality measurement, in addition to energy consumption estimate. The goal is to provide highly reliable and better communication links with energy-efficiency. The proposed routing algorithm has been verified by NS-2 simulations. The results have shown that LABQ outperforms existing algorithms by significantly reducing link breakages and thereby reducing the overheads in reconnection and retransmission. It also reduces the average end-to-end delay for data transfer and enhances the lifetime of nodes by making energy-efficient routing decisions. <s> BIB015 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Radio transceivers for wireless sensor networks are typically cheap devices offering low bandwidth communication only. When physical events in the real world trigger spontaneous communication in many nodes the single communication channel is under heavy load and many messages are lost due to collisions. CSMA/CA schemes are well suited to spontaneous communication, but do not provide a high channel utilization under heavy load. TDMA protocols have some conceptual advantage here, but in the case of mobile sensor nodes they need to be adaptive and establish TDMA schedules on demand. MLMAC is a novel TDMA based MAC protocol that can react on changing radio neighborhoods in mobile networks. In this paper we introduce the MLMAC protocol and present the results of real experiments with a group of mobile sensor nodes based on RCX robots. <s> BIB016 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> In this paper, we propose a distributed, scalable, energy-efficient media access control (MAC) protocol that works despite long, unknown propagation delays of the underwater acoustic medium. This protocol can be used for delay-tolerant applications such as underwater ecological sensor networks between energy-limited nodes. Our protocol differs significantly from ALOHA, multiple access with collision avoidance (MACA), and the media access protocol for wireless LANs (MACAW) in that energy is the main performance metric in our case rather than bandwidth utilization. We show that under a realistic underwater sensor network scenario, our MAC protocol wastes only 4% of the transmit energy and only 1.5% of the receive energy due to collisions, when the average number of neighbors is four, and the duty cycle is 0.004. This distributed, scalable MAC protocol has the potential to serve as a primer for the development of energy-efficient MAC protocols for future underwater sensor networks. <s> BIB017 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> This paper proposes a channel access protocol for ad-hoc underwater acoustic networks which are characterized by long propagation delays and unequal transmit/receive power requirements. The protocol saves transmission energy by avoiding collisions while maximizing throughput. It is based on minimizing the duration of a hand-shake by taking advantage of the receiver's tolerance to interference when the two nodes are closer than the maximal transmission range. Nodes do not need to be synchronized, can move, are half-duplex, and use the same transmission power. This protocol achieves a throughput several times higher than that of the slotted FAMA, while offering similar savings in energy. Although carrier sensing ALOHA offers a higher throughput, it wastes much more power on collisions. <s> BIB018 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Unlike terrestrial networks that mainly rely on radio waves for communications, underwater networks utilize acoustic waves, which have comparatively lower loss and longer range in underwater environments. However, the use of acoustic waves pose a new research challenge in the networking area. While existing network schemes for terrestrial sensor networks are mainly designed for negligible propagation delay and high data rate, underwater acoustic communications are characterized by high propagation delay and low data rate. These terrestrial schemes, when directly applied to the underwater channel, will under-utilize its already limited capacity. We investigate how the underwater channel's throughput may be enhanced via medium access control (MAC) techniques that consider its unique characteristics. Specifically, we study the performance of Aloha-based protocols in underwater networks, and propose two enhanced schemes, namely, Aloha with collision avoidance (Aloha-CA), and Aloha with advance notification (Aloha-AN), which are capable of using the long propagation delays to their advantage. Simulation results have shown that both schemes can boost the throughput by reducing the number of collisions, and, for the case of Aloha-AN, also by significantly reducing the number of unproductive transmissions. <s> BIB019 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Recent technological advances in microelectronics and nano-systems technologies have made it feasible to equip wireless sensor nodes with small low-cost cameras to capture and transmit video. Wireless video sensor networks are gaining popularity due to numerous potential applications such as video surveillance, environmental and habitat monitoring, and so on. However, due to the limited battery available in wireless video sensor nodes, provisioning of QoS in such a network is a challenging task. We provide a survey on the major issues related to QoS provisioning in wireless video sensor networks and possible solution approaches. A dynamic power management framework is proposed for a wireless video sensor node to improve energy saving performance so that the lifetime of the sensor node can be increased. This framework considers the video traffic arrival process in the sensor node, the sleep and wakeup processes in the camera and wireless transceiver electronics, the queue status, and the wireless channel condition. Performance analysis results show that the proposed mechanism can achieve considerable energy saving in a sensor node while providing a target level of QoS performance. <s> BIB020 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> In contrast to traditional wireless sensor networks, where energy conservation is the main objective, next-generation wireless sensor networks will additionally demand guarantees in terms of delay, reliability and bandwidth. However, current sensor network protocols offer very limited QoS support. Moreover, the current research does not take into account the growing heterogeneous nature of sensor nodes and applications. Therefore, we present in this paper an adaptive modular QoS architecture (AMoQoSA), which uses several QoS techniques that can be activated according to the nodes' capabilities. This enables the network to dynamically adapt itself to the current network situation in order to continuously deliver optimal QoS guarantees in heterogeneous sensor networks. <s> BIB021 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Energy efficiency is a critical issue for sensor network. In this paper we propose an energy efficient context adaptive MAC protocol for wireless sensor networks. The existing approaches improve energy efficiency by controlling the duty cycle of transmission period. The proposed protocol achieves that by letting each node stay in the sleep mode if the number of packets in the buffer is smaller than the threshold, while the threshold value is decided according to the distance of the node to the sink node. The variable threshold for each switch node, however, may cause increased latency. This problem is solved by immediately transmitting the packets of high priority context data. Computer simulation using OMNeT++ reveals that the proposed protocol significantly reduces the energy consumption compared with the existing S-MAC and T-MAC protocol. <s> BIB022 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> WSNs usually combine periodic readings with messages generated by unexpected events. When an event is detected by a group of sensors, several notification messages are sent simultaneously to the sink, resulting in sporadic increases of the network load. Additionally, these messages sometimes require a lower latency and higher reliability as they can be associated to emergency situations. Current MAC protocols for WSNs are not able to react rapidly to these sporadic changes on the traffic load, mainly due to the duty cycle operation, adopted to save energy in the sensor nodes, resulting in message losses or high delays that compromise the event detection at sink. In this work, two main contributions are provided: first, the collective QoS definitions are applied to measure event detection capabilities and second, a novel traffic-aware Low Power Listening MAC to improve the network response to sporadic changes in the traffic load is presented. Results show that the collective QoS in terms of collective throughput, latency and reliability are improved maintaining a low energy consumption at each individual sensor node. <s> BIB023 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> In wireless sensor network, it is essential to find effective means for power control of randomly distributed nodes. In this paper, based on diverse receiving QoS parameters, a fuzzy algorithm for peer to peer power control of wireless sensor nodes is proposed. Simulation results show that the proposed algorithm reduces packet error rate (PER) and prolongs survival time of network, compared with fixed transmission power method. Thus, this fuzzy algorithm could realize reliable data transmission with low power consumption. <s> BIB024 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Sensor networks are deployed in remote locations with limited processor capabilities, memory capacities, and battery supplies. Wireless Sensor Networks (WSN) detects environmental information with sensors in remote settings. One problem facing WSNs is the inability to resupply power to these energy-constrained devices due to their remoteness. Therefore to extend a WSN's effectiveness, the lifetime of the network must be increased by making them as energy efficient as possible. An energy-efficient medium access control (MAC) can boost a WSN's lifetime. This paper focuses on a protocol stack solution that deals with MAC layer, that minimizes the energy consumption and delay required to transmit packets across the network. It is based on Sensor Medium Access Control (S-MAC) called Adaptive SMAC protocol designed for sensor networks. It enables low duty cycle operation in a multi-hop network and common sleep schedules to reduce control overhead and enable traffic adaptive wakeup. To reduce control overhead and latency, introduces coordinated sleeping among neighboring nodes. It is a contention based protocol based on CSMA/CA mechanism. This protocol is simulated in NS-2 and performance evaluated using various topologies under various traffic conditions. In addition with this we tried to improve the energy efficiency of Adaptive SMAC with the help of a new design called Adaptive Cross MAC protocol <s> BIB025 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> This paper proposes and analyzes a Quality of service enhanced Base station Controlled Dynamic Clustering Protocol (QBCDCP), suitable for the support of video and imaging traffic over resource constrained wireless sensor nodes. The protocol achieves energy efficiency through a rotating head clustering approach and delegation of energy-intensive tasks to a high-power base station, while providing quality of service (QoS) support by including delay and bandwidth parameters in the route selection process. A Time Division Multiple Access (TDMA) scheme is used for intra- and intercluster communication, providing bandwidth reservation. Performance of QBCDCP is evaluated in terms of energy consumption and end-to-end image delay via analytical and discrete-event simulation techniques. Numerical results provide insights on the selection of network parameters such as number of clusters that improve the sensing node lifetime while maintaining high quality of service. The results also demonstrate the trade-off between end-to-end image delay and sensor node lifetime. <s> BIB026 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> As the wireless sensor network (WSN) technology evolves towards higher transmission rates, it makes sense to start considering sensing and transmission of real-time information, such as audio and video. These applications require quality of service (QoS) guarantees, not offered by current networks. The multi-hop nature of WSN makes QoS a challenging task. In addition, researchers have recently realized that cross-layer protocols achieve a far better performance than protocol layers working in isolation. These two ingredients are the focus of our work. In this paper we propose an architecture in which the MAC and routing protocols collaborate to discover and reserve routes, to organize nodes into clusters and to schedule the access to the transmission medium in a coordinated timeshared fashion. As a consequence, not only QoS is achieved but also great energy savings by eliminating collisions and considerably reducing idle listening. The resulting protocol is called QUATTRO: QUAlity-of-service-capable clusTer-based Timeshared ROuting-assisted MAC protocol. We evaluate our proposal using simulations by examining multiple scenarios in which different numbers and densities of nodes are considered. Our results show that the protocol overhead is reasonable. <s> BIB027 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> UnderWater Acoustic Sensor Networks (UW-ASNs) consist of sensors and Autonomous Underwater Vehicles (AUVs) performing collaborative monitoring tasks. In this article, UWMAC, a distributed Medium Access Control (MAC) protocol designed for UW-ASNs, is introduced. The proposed MAC protocol is a transmitter-based Code Division Multiple Access (CDMA) scheme that incorporates a novel closed-loop distributed algorithm to jointly set the optimal transmit power and code length. CDMA is the most promising physical layer and multiple access technique for UW-ASNs because it is robust to frequency-selective fading, it compensates for the effect of multipath at the receiver, and it allows receivers to distinguish among signals simultaneously transmitted by multiple devices. UW-MAC aims at achieving three objectives, i.e., guarantee i) high network throughput, ii) low channel access delay, and iii) low energy consumption. It is demonstrated that UW-MAC simultaneously achieves these three objectives in deep water communications (where the ocean depth is more than 100 m), which are usually not severely affected by multipath. In shallow water communications, which may be heavily affected by multipath, it dynamically finds the optimal trade-off among these objectives according to the application requirements. UW-MAC is the first protocol that leverages CDMA properties to achieve multiple access to the scarce underwater bandwidth, while other protocols tailored for this environment have considered CDMA merely from a physical layer perspective. Experiments show that UW-MAC outperforms many existing MAC protocols tuned for the underwater environment under different architecture scenarios and simulation settings. <s> BIB028 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Protocols with indirect QoS support <s> Data aggregation has been one of important key techniques to increase energy efficiency and bandwidth utilization in wireless sensor networks. There were many research works in this area, but most of them have a disadvantage that cannot optimally meet practical requirements, such as the heterogeneity of application data and latency requirements. In this paper, we propose a novel and simple data aggregation protocol, referred to as Lump, which enables to support QoS requirements of applications. For this purpose, it prioritizes packets for differentiated services and facilitates aggregation decision. Its architecture has a cross-layered design that mitigates overheads of in-network processing, and it is completely an independent module residing on between data-link layer and network layer so that it can be applicable to a variety of applications. Our experiments show that, when an intermediate node has four neighbors, Lump can reduce radio traffic up to 30% while satisfying QoS requirements. <s> BIB029
Although the previous sections summarize a variety of QoS-aware MAC protocols in the literature, there are still some other protocols that we need to mention. These protocols support QoS provisioning even though they are not designed to provide it as a primary objective. Most of these indirect-QoS-aware MAC protocols adapt themselves to the current network conditions and achieve better performance in QoS aspect. WiseMAC BIB004 tries to reduce the energy consumption by determining the length of the preamble dynamically. CA-MAC BIB022 adapts the duty cycle of the sensor nodes based on their buffer load and priority of the packets stored in the buffer where TRAMA BIB003 adapts the number of time slots reserved for each sensor node according to their current traffic rate. I-EDF BIB001 is a MAC protocol based on earliest-deadline-first and tries to provide latency requirements of delay-bounded data. LWT-MAC BIB023 responds effectively to sporadic changes in the event-based sensor networks by switching to unscheduled medium access under low traffic load and to scheduled medium access under high traffic load. Jiang et al. BIB024 propose a fuzzy algorithm which aims to reduce the packet error rate and prolong the network lifetime by adjusting the transmission power of the sensor nodes adaptively. Some protocols modified the S-MAC protocol BIB005 , which is a well-known sensor MAC protocol, and proposed dynamic versions of it. T-MAC BIB025 adapts the active time in S-MAC while DSMAC BIB006 adds a dynamic duty cycle feature to S-MAC. TA-MAC BIB008 modifies the static CW mechanism of S-MAC and adapts itself to the current traffic load. PSMAC BIB014 is a joint MAC and physical layer protocol and introduces a transmission power control mechanism to S-MAC. Although Lump BIB029 protocol operates between the link and the network layer, it can be considered as a MAC component rather than a complete MAC protocol. Lump utilizes a differentiated data aggregation technique to provide QoS support. The aim of the protocol is to reduce radio communication and minimize energy consumption while fulfilling the specific latency requirements of each traffic type. As mentioned in Section 5.5, clustering is a viable technique for QoS provisioning. QBCDCP BIB026 supports video and image transmission with dynamic clustering and provides QoS support in terms of delay and bandwidth. QUAT-TRO BIB027 proposes collaboration of MAC and network layers. It utilizes clustering and scheduled medium access to achieve QoS provisioning. Although there exist studies on addressing QoS challenges at the routing layer BIB015 BIB011 BIB012 , to the best of our knowledge, there is no QoS-aware MAC protocol designed for mobile wireless sensor networks. However, there exist a few MAC protocols that address the challenge of mobility with adaptive MAC protocols. For instance, in BIB016 , the TDMA-based LMAC protocol  , which is designed for static WSNs, is modified for mobility support. Different than the static LMAC protocol, in adaptive LMAC, nodes update their selected time slots for medium access whenever the neighborhood of a node changes due to mobility. However, adaptation of the frame lengths or number of time slots per frame for QoS support are not discussed or implemented in this study. In another study BIB007 , authors propose a modification of the S-MAC protocol BIB005 , called MS-MAC for mobile WSNs. In MS-MAC, nodes discover the presence of mobility within their neighborhood based on the received signal levels of periodical SYNC messages from the neighbors. If a node detects a change in the strength of a signal received from a neighbor, it concludes that the neighbor or the node itself are moving and adaptively changes the schedule that it is following according to the mobility patterns in the neighborhood. MOBMAC BIB009 , is another adaptive MAC protocol designed for mobile WSNs. MOBMAC addresses the problem of frame losses caused by the communication signals experiencing mobility induced effects such as Doppler Shifts. It introduces an adaptive frame size predictor, using an Extended Kalman Filter to predict an optimal frame size for every transmission. A smaller frame size is predicted when the signal characteristics are poor (i.e. when the signal is Doppler shifted) and larger frame sizes are predicted when the quality of the channel improves (i.e. when the nodes are stationary). By transmitting a small frame size in a bad channel, MOBMAC reduces the transmission power since smaller frames need lower transmission power compared to larger frames and also reduces the probability of error occurrence since it is less in a smaller frame than that of a large frame. Since underwater and underground sensor networks are not as practical and mature as traditional terrestrial WSNs, there is no noticeable QoS aware MAC protocol in the literature for UW-ASNs and WUSNs. However, there is a group of MAC layer proposals for underwater sensor networks which can be further improved for QoS support. UW-MAC BIB028 is a CDMA based MAC protocol for underwater sensor networks and it has three objectives, which are high throughput, low delay and low energy expenditure. UW-MAC achieves these objectives easily in deep waters while it tries to adaptively find the optimal tradeoff among the objectives in shallow waters. In BIB017 , authors propose UWAN-MAC for stationary underwater sensor networks that have to operate under long, unknown propagation delays and they select energy efficiency as their main performance metric. UWAN-MAC uses a CSMA based scheme and employs sleep/listen schedules to conserve energy. Local synchronization among neighboring sensor nodes is achieved by means of periodic SYNC messages. Although there are other MAC protocols proposed for ad hoc underwater acoustic networks such as BIB018 BIB013 BIB019 , we will not go into details of them in this work. However, reader may refer to  for an overview of networking protocols for underwater wireless communications. Some researchers approach QoS provisioning with a wider perspective and propose frameworks or architectures rather than constraining the problem to a single communication layer. RAP BIB002 is a real-time communication architecture for large-scale WSNs and introduces Velocity Monotonic Scheduling which forwards the packets to their destinations at requested velocity, hence tries to accurately fulfill the end-to-end deadline requirement of real-time traffic. Yuan et al. BIB010 proposed an integrated single framework to jointly optimize the energy efficiency and QoS. Fallahi and Hossain BIB020 derived a dynamic power management framework for wireless video sensor networks to achieve energy saving while providing QoS support. Troubleyn et al. proposed AMoQoSA BIB021 , which is an adaptive modular QoS architecture for heterogeneous sensor networks. Aim of this architecture is to continuously deliver QoS support by activating a set of QoS techniques according to capabilities of the sensor nodes.