# Design and Analysis of a Low Latency Deterministic Network MAC for Wireless Sensor Networks
## 2 Related Works  
A general approach to evaluate the IEEE 802.15.4 performance of slotted the CSMA/CA protocol for only the unsaturated traffic condition is designed in [5]. By considering both saturated and unsaturated traffic to predict the energy consumption, as well as throughput, the authors in [6] have presented an analytical model for the IEEE 802.15.4 MAC protocol. A Markov chain-based analytical model is introduced in [7] to evaluate the impact of throughput and energy consumption on the probability of delivering a packet. However, these protocols did not talk about how to allocate the retransmission slots in case of packet failures. The authors in [8] have designed one analytical model for the guaranteed time slot (GTS) allocation mechanism during the contention-free period (CFP). The authors in [9] have proposed a methodology to analyze the GTS mechanism in the CFP. The performance of IEEE 802.15.4 MAC is analyzed in [10] for both CFP and the contention access period (CAP). However, these works did not address transmission failures due to interference or collision, which is an important issue for the low latency applications. The authors in [11] have designed one additional carrier sensing algorithm to get information from the busy channel due to data or acknowledgment (ACK) transmissions during the second CCA. However, the power consumption will be more if the second CCA is found busy due to data/ACK transmissions. A new MAC protocol is designed in [12] to avoid the channel being busy due to acknowledgment packet transmission without any additional CCA. To increase the probability of data transmission by ignoring the first CCA channel busy condition due to ACK transmissions, the authors in [13] propose one segmented CCA mechanism. However, there is no improvement in the case that a node transmits a data packet instead of an ACK. The effects of different _macSuperframeOrder_ (SO) values on the total network throughput, delay and energy consumption through simulation have been studied in [14]. However, the work entirely focuses on the ideal channel condition, which is not realistic because the channel condition oscillates between good and poor in the wireless environment. The contention-based protocols are widely used in WSN applications to reduce delay and collisions. The authors [15] have studied the stability and accuracy of the wireless technology by using the IEEE 802.15.4/ZigBee technology in monitoring human body temperature. However, the authors have not considered any retransmission opportunity for transmission failure. A mathematical model is designed in [16] based on stochastic geometry, which is used for performance evaluations of success probability in transmitting packets from nodes to the coordinator. However, the authors have not done the performance analysis such as delay and energy, which are crucial factors for some WSN applications. The impact of fading statistics on the MAC performance in terms of reliability, delay and power consumption by varying traffic rates, inter-nodes distances, carrier sensing range and the signal-to-interference-plus-noise ratio (\(SINR\)) threshold have been studied in [17]. However, all of these works are based on the IEEE 802.15.4 standard. The major requirements of industrial application are very low latency communication. Hence, the LLDN MAC mechanism of the IEEE 802.15.4e [2] standard is most suitable for these requirements. Comparisons of different technical parameters between Bluetooth, ZigBee and Wi-Fi are given in [18], where the received signal strength indicator (RSSI) value, round trip delay (RTD) time and latency are analyzed. The performance of the network considering both high and low data rate is analyzed in [19]. The impact of retry limit, backoff, network lifetime under all different data rates and traffic loads is also analyzed in the same work. However, they have not taken the priority into account for the transmission failure by the nodes.