QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> We present a suite of algorithms for self-organization of wireless sensor networks in which there is a scalably large number of mainly static nodes with highly constrained energy resources. The protocols further support slow mobility by a subset of the nodes, energy-efficient routing, and formation of ad hoc subnetworks for carrying out cooperative signal processing functions among a set of the nodes. <s> BIB001 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> Recent advances in wireless sensor networks have led to many new routing protocols specifically designed for sensor networks. Almost all of these routing protocols considered energy efficiency as the ultimate objective in order to maximize the whole network lifetime. However, the introduction of video and imaging sensors has posed additional challenges. Transmission of video and imaging data requires both energy and QoS aware routing in order to ensure efficient usage of the sensors and effective access to the gathered measurements. In this paper, we propose an energy-aware QoS routing protocol, which can also run efficiently with best-effort traffic. The protocol finds a least-cost, delay-constrained path for real-time data in terms of link cost that captures nodes' energy reserve, transmission energy, error rate and other communication parameters. Moreover, throughput for non-real-time data is maximized by adjusting the service rate for both real-time and non-realtime data at sensor nodes. Simulation results have demonstrated the effectiveness of our approach. <s> BIB002 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> Many new routing and MAC layer protocols have been proposed for wireless sensor networks tackling the issues raised by the resource constrained unattended sensor nodes in large-scale deployments. The majority of these protocols considered energy efficiency as the main objective and assumed data traffic with unconstrained delivery requirements. However, the growing interest in applications that demand certain end-to-end performance guarantees and the introduction of imaging and video sensors have posed additional challenges. Transmission of data in such cases requires both energy and QoS aware network management in order to ensure efficient usage of the sensor resources and effective access to the gathered measurements. In this paper, we highlight the architectural and operational challenges of handling of QoS traffic in sensor networks. We report on progress make to-date and outline open research problems. <s> BIB003 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <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> BIB004 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> Sensor nodes are densely deployed to accomplish various applications because of the inexpensive cost and small size. Depending on different applications, the traffic in the wireless sensor networks may be mixed with time-sensitive packets and reliability-demanding packets. Therefore, QoS routing is an important issue in wireless sensor networks. Our goal is to provide soft-QoS to different packets as path information is not readily available in wireless networks. In this paper, we utilize the multiple paths between the source and sink pairs for QoS provisioning. Unlike E2E QoS schemes, soft-QoS mapped into links on a path is provided based on local link state information. By the estimation and approximation of path quality, traditional NP-complete QoS problem can be transformed to a modest problem. The idea is to formulate the optimization problem as a probabilistic programming, then based on some approximation technique, we convert it into a deterministic linear programming, which is much easier and convenient to solve. More importantly, the resulting solution is also one to the original probabilistic programming. Simulation results demonstrate the effectiveness of our approach. <s> BIB005 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> A wireless sensor/actuator network (WSAN) is a group of sensors and actuators that are geographically distributed and interconnected by wireless networks. Sensors gather information about the state of physical world. Actuators react to this information by performing appropriate actions. WSANs thus enable cyber systems to monitor and manipulate the behavior of the physical world. WSANs are growing at a tremendous pace, just like the exploding evolution of Internet. Supporting quality of service (QoS) will be of critical importance for pervasive WSANs that serve as the network infrastructure of diverse applications. To spark new research and development interests in this field, this paper examines and discusses the requirements, critical challenges, and open research issues on QoS management in WSANs. A brief overview of recent progress is given. <s> BIB006 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> The increasing demand for real-time applications in Wireless Sensor Networks (WSNs) has made the Quality of Service (QoS) based communication protocols an interesting and hot research topic. Satisfying Quality of Service (QoS) requirements (e.g. bandwidth and delay constraints) for the different QoS based applications of WSNs raises significant challenges. More precisely, the networking protocols need to cope up with energy constraints, while providing precise QoS guarantee. Therefore, enabling QoS applications in sensor networks requires energy and QoS awareness in different layers of the protocol stack. In many of these applications (such as multimedia applications, or real-time and mission critical applications), the network traffic is mixed of delay sensitive and delay tolerant traffic. Hence, QoS routing becomes an important issue. In this paper, we propose an Energy Efficient and QoS aware multipath routing protocol (abbreviated shortly as EQSR) that maximizes the network lifetime through balancing energy consumption across multiple nodes, uses the concept of service differentiation to allow delay sensitive traffic to reach the sink node within an acceptable delay, reduces the end to end delay through spreading out the traffic across multiple paths, and increases the throughput through introducing data redundancy. EQSR uses the residual energy, node available buffer size, and Signal-to-Noise Ratio (SNR) to predict the best next hop through the paths construction phase. Based on the concept of service differentiation, EQSR protocol employs a queuing model to handle both real-time and non-real-time traffic. By means of simulations, we evaluate and compare the performance of our routing protocol with the MCMP (Multi-Constraint Multi-Path) routing protocol. Simulation results have shown that our protocol achieves lower average delay, more energy savings, and higher packet delivery ratio than the MCMP protocol. <s> BIB007 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS support at MAC layer <s> Achieving Quality of Service (QoS) objective in Wireless Sensor Network (WSN) handling the multimedia information has significantly gained the importance lately besides energy efficient hardware designing. Transport layer of the WSN communication protocol stack plays a significant role in meeting the QoS objective of WSN. This paper presents a light weight transport protocol for WSN that can handle packets from a numbers of sources having different sensed information and having different priority levels. The protocol assigned middle motes are intelligent enough to achieve prioritization in transmission based on the priority level and packet's Time-To-Live (TTL) information. Extensive simulation is carried out for the three different modes of the envisaged protocol having no prioritized enabled storage, complete prioritized enabled storage and distributed prioritized enabled storage. The results reveal that the significant improvement is observed in case of distributed prioritized enabled storage, approximately 3% data loss occurred, in comparison to 7% data loss for without prioritized enabled storage mode. <s> BIB008
Although collective effort of all the communication protocol stack entities is essential for QoS provisioning, MAC layer possesses a particular importance among them since it rules the sharing of the medium and all other upperlayer protocols are bound to that. QoS support in the network or transport layers cannot be provided without the assumption of a MAC protocol which solves the problems of medium sharing and supports reliable communication. Besides, the MAC layer handles the additional challenges of the WSNs such as severe energy constraints by duty cycling and unpredictable environmental conditions by methods such as retransmissions or transmission power control. Therefore, the MAC layer plays a key role for QoS provisioning and dominates the performance of the QoS support. The reader can refer to BIB003 BIB001 BIB002 BIB004 BIB005 BIB007 for QoS support at the network layer, and to BIB006  BIB008  at the transport layer and to  for different layers.