QoS-aware MAC protocols for wireless sensor networks: A survey <s> Q-MAC <s> The problem of allocating network resources to the users of an integrated services network is investigated in the context of rate based flow control. The authors propose the use of a packet service discipline at the nodes of the network that is based on a multiplex scheme called generalized processor sharing (GPS). This service discipline is combined with leaky bucket rate admission control to provide flexible, efficient and fair use of the links. A single server GPS system is analyzed exactly, and tight bounds on worst case packet delay, output burstiness and backlog are derived for each session, when the sources are constrained by leaky buckets. The analysis yields a simple resource assignment scheme that allows the server to make worst case delay and rate guarantees to every session in the system. Extensions of this work to arbitrary topology networks are also discussed.<<ETX>> <s> BIB001 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> Q-MAC <s> We present an innovative MAC protocol (Q-MAC) that minimizes the energy consumption in multi-hop wireless sensor networks (WSNs) and provides quality of service (QoS) by differentiating network services based on priority levels. The priority levels reflect application priority and the state of system resources, namely residual energy and queue occupancies. The Q-MAC utilizes both intra-node and inter-node arbitration. The intra-node packet scheduling is a multiple queuing architecture with packet classification and weighted arbitration. We also introduce the power conservation MACAW (PC-MACAW) - a power-aware scheduling mechanism that, together with the loosely prioritized random access (LPRA) algorithm, govern the inter-node scheduling. Performance evaluation are conducted between Q-MAC and S-MAC with respect to two performance metrics: energy consumption and average latency. Simulation results indicate that the performance of the Q-MAC is comparable to that of the S-MAC in non-prioritized traffic scenarios; when packets with different priorities are present, Q-MAC supiors in average latency differentiation between the classes of service, while maintaining the same energy level as that of S-MAC <s> BIB002
Q-MAC BIB002 utilizes intra-node scheduling to select the next serviced packet from five different priority queues and inter-node scheduling to coordinate the medium access among multiple neighboring nodes as seen in Fig. 3 . The priority of an incoming packet is determined by two factors. Application layer perspective gives priorities based on the content of the packet and MAC layer does based on traversed hop count. In this way, packets are mapped into predefined five different priority queues including one instant queue that any packet in this queue is served immediately. Within the context of intra-node scheduling, MAX-MIN fairness algorithm [63] is used to control the rate and packetized Generalized Processor Sharing BIB001 algorithm is used to select the next transmitted packet. For inter-node scheduling, a novel protocol named Loosely Prioritized Random Access (LPRA) is proposed for coordinating the medium access based on the transmission urgencies of the nodes which have packets to send. There are four factors determining the transmission urgency of a node: packet criticality from application point of view, traversed hop count of the packet, remaining energy of the sensor node and queue's proportional load. A frame represents single RTS-CTS-DATA-ACK packet exchange and consists of contention period (CP) and transmission period (TP). CP is divided into five smaller contention portions which are exclusive to sensor nodes that have certain level of transmission urgency. As congestion control mechanisms, doubling the CW size is proposed for decreasing the probability of collision and decreasing the packet deadline for alleviating the traffic load. For energy efficiency, sensor nodes follow sleep-listen schedules with fixed duty cycles. Advantages and disadvantages: Dynamic priority assignment provides robustness against changing conditions of the sensor network. However, calculation of the transmission urgency of a node is relatively complex. Integration of the increasing geometric probability for CW selecting may decrease the collision rate but also may result in higher latencies.