QoS-aware MAC protocols for wireless sensor networks: A survey <s> EQ-MAC <s> The low-energy characteristics of wireless sensor networks (WSNs) pose a great design challenge for MAC protocol design. Recent studies have proposed different cluster-based MAC protocols. In this paper, we propose an intra-cluster communication bit-map-assisted (BMA) MAC protocol for large-scale cluster-based WSNs. BMA is intended for event-driven applications, where sensor nodes transmit data to the cluster head only if significant events are observed. In addition, we provide the energy and packet latency analytical models for BMA, conventional TDMA, and energy efficient TDMA (E-TDMA) when used as intra-cluster MAC schemes. Our results show that BMA is superior for the cases of low and medium traffic loads, relatively few sensor nodes per cluster, and relatively large data packet sizes. In addition, BMA performs better than the TDMA-based MAC schemes in terms of average packet latency. <s> BIB001 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> EQ-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 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> EQ-MAC <s> This paper presents a general framework for adaptive Energy and QoS Aware (EQoSA) MAC protocol for wireless sensor networks. It is a scheduling based MAC protocol assuming a steady state network behavior. Similar to previous works, the time is divided into rounds and each round starts with a setup phase followed by a number of sessions. Each session starts with a contention window followed by a number of slots reserved for those users who expressed their wishes to transmit packets and the cluster head approved their assignment. The proposed protocol has two unique features; the dynamic size of each session and the ability to accommodate bursty sensors by allocating more than one data slot in each session. EQoSA is so general to accommodate a wide range of wireless sensor networks applications. A discrete event driven simulation is extensively run to evaluate the proposed protocol. The proposed protocol is examined against Bit-Map MAC protocol (a modified LEACH) and it shows an outstanding improvement both in end-to-end packet delay as well as the total consumed energy. These important results make EQoSA a viable MAC protocol for real time applications such as video and imaging applications. <s> BIB003 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> EQ-MAC <s> Enabling quality of service (QoS) applications over battery-constrained wireless sensor networks (WSNs) poses significant challenges, because of the special characteristics of such networks. Developing real-time applications for WSNs necessitates the development of new communication protocols capable of achieving application-specific QoS and at the same time save energy. In this paper, we continue our previous work on developing and improving our EQ-MAC protocol, which is designed specifically for WSNs to reduce energy consumption and provides QoS guarantees through the use of the service differentiation concept. The proposed protocol consists of two subprotocols: Classifier MAC (C-MAC) and Channel Access MAC (CA-MAC). C-MAC is responsible of classifying gathered data at sensor nodes based on its importance. The CA-MAC is an energy conserving medium access mechanism which uses a hybrid scheduling technique. CA-MAC saves energy by differentiating between control and data messages. Data messages are assigned scheduled slots with no contention (here we have to emphasize that slots are assigned only to those nodes that have data to send, this allows an efficient energy use of the Time Division Multiple Access (TDMA) slots), whereas short periodic control messages are assigned random access slots. To study the performance of the EQ-MAC protocol, we have conducted several simulation experiments on Network Simulator (NS-2) to evaluate and compare the performance of our protocol against S-MAC and Q-MAC protocols. Simulation results demonstrate that EQ-MAC outperforms the other two protocols and achieves a significant improvement in terms of the energy expenditure and delivery ratio. Under prioritized traffic, EQ-MAC is comparable to Q-MAC in average latency, while achieving less energy consumption. Copyright © 2010 John Wiley & Sons, Ltd. <s> BIB004
EQ-MAC BIB004 is designed to provide QoS support for cluster based single-hop sensor networks by service differentiation and uses a hybrid medium access scheme. The protocol is composed of two parts: Classifier MAC (C-MAC) and Channel Access MAC (CA-MAC). C-MAC classifies the received data packets into four priority levels according to the importance of the packet assigned by the application layer and uses a queueing architecture similar to Q-MAC BIB002 . This architecture includes an instant queue and packets stored in that queue are served immediately. CA-MAC is responsible for medium sharing and consists of four phases repeated in each frame: Synchronization, Request, Receive Scheduling and Data Transfer. During Synchronization, Request and Receive Scheduling phases; sensor nodes get synchronized, contend to send their channel requests to cluster head and receive scheduling massages broadcast from cluster head. Only control messages are exchanged in these first three phases and medium is shared based on CSMA/CA. In the last phase of CA-MAC which is Data Transfer, each sensor node follows the transmission schedule received from cluster head and accesses to the medium without contention. Sensor nodes that have no data to send or could not manage to acquire a transmission slot go to sleep state during this phase for power saving. Advantages and disadvantages: Probability of collisions and energy consumption are reduced by using contention based medium access for short periodic control messages and by scheduled medium access for long data packets. However, authors try to overcome classical synchronization problem of TDMA scheme by employing a SYNC phase at the beginning of each frame which brings an extra overhead to the protocol. Moreover, EQ-MAC is designed for single-hop cluster based sensor networks and cannot handle multi-hop transmissions. Also, clustering algorithm is not included in the MAC protocol itself. 6.2. Application-specific protocols 6.2.1. EQoSA EQoSA BIB003 is a hybrid MAC protocol which is designed to provide QoS support especially for video and image transmission over sensor networks. Basically, EQoSA modifies the fixed session size of the BMA BIB001 protocol and uses dynamic session sizes regarding the number of active sensor nodes and their traffic loads. During the contention period, each node reports whether it has data to transmit or not. The cluster head then performs the slot assignment and broadcasts to all sensor nodes. In this way, EQoSA accommodates bursty traffic by allocating the required number of data slots for each sensor node in each session. Advantages and disadvantages: EQoSA suffers from the traditional time synchronization problem of TDMA based schemes and only has the ability to accommodate bursty traffic load rather than a proper service differentiation mechanism. Moreover, it needs more powerful cluster heads within the sensor network to perform and announce the slot assignment.