S. H. Lee et al. propose AMAC: a traffic-adaptive sensor network MAC protocol
through variable duty cycle operations [10]. In AMAC when the network is idle,
Request to Send / Clear to Send (RTS/CTS) messages are not performed for energy saving. In order to achieve variable duty cycle operations, two basic com- ponents are used in this work: a) a clock synchronisation algorithm. Each node synchronising its wake-up time with its neighbours in a similar way to S-MAC. b) a schedule synchronisation mechanism. This mechanism is responsible for the synchronisation of wake-up times between neighbour nodes when AMAC nodes have adapted their cycle times.
J. Jeon propose DCA: A duty cycle adaptation algorithm for 802.15.4 beacon-
enabled WSNs [11]. DCA assumes that beacon order (BO) is constant and adapts
superframe order (SO) according to the superframe estimations. In this protocol, the control field in MAC protocol data unit (MPDU) is modified in order to gather traffic information from the end devices. After all the data are collected, the DCA coordinator estimates the number of packets being queued in the end devices and adjusts the SO accordingly.
WSN [12]. In this work, each node adjusts its duty cycle based on the traffic intensity measured by the queue length in its child nodes. A parent node will enter listen state and remain in this state until all the packets from its child nodes have been received. This protocol adds some additional overhead for the exchange of the traffic intensity between child and parent nodes. Furthermore, in order for this protocol to be functional, all packets in the WSN must be of the same size and traffic must be unidirectional (from the edges of the network towards the sink).
N. Saxena propose a dynamic duty cycle and adaptive contention window
based on QoS-MAC protocol for wireless multimedia sensor networks [13]. This
protocol periodically measure the number of transmitted packets and calculates the probability of transmission failure based on the success-failure packet trans- mission ratio. When a probability of transmission failure is high a node will adjust its contention window (CW) and wait for its neighbour nodes to adjust their CW accordingly. Each node will keep adjusting its own CW until it achieves its CW- target. This protocol also suggests a scaling factor for the different traffic classes. The scaling factor is used by the CW increase and decrease algorithm for service differentiation between the different traffic classes. In this protocol, duty cycle times are also based on the class of the traffic. Depending on the dominating traffic class (which traffic class had the most transmitted packets), the algorithm selects the active time and adjusts the duty cycle.
TA-MAC [14] is an adaptive duty cycle protocol for WSN. In TA-MAC, all
nodes must be synchronised. In order to achieve node synchronisation, all nodes keep their radio on until they receive a SYNC packet. The SYNC packets is first broadcasted by the sink and then further propagated with broadcast messages by the rest of the nodes. In contrast to this protocols name, duty cycle is not altered under any network conditions; instead two or more packets may be transmitted in a single cycle through a two-way hand shaking mechanism (DATA/ACK).
R.D.P. Alberola propose DCLA: a duty cycle learning algorithm for IEEE
802.15.4 beacon-enabled WSN [15]. In DCLA one node will operate as the co-
ordinator. The coordinator node need to employ some estimation of the end
devices traffic requirements in order to calculate an optimal duty cycle. In order to achieve this, the coordinator calculates the number of received messages dur- ing an active period. On the other side, end-devices embed their transmit queue occupation and delay values in the MAC header of sent data frames. When a coordinator node has no knowledge regarding the end devices the optimal duty cycle is calculated by the DCLA agent. The technique used for the calculation of the optimal duty cycle in that case is known as Q-Learning.
L. Dongho propose ADCC: an adaptive duty cycle based on congestion control
time based on the information received from the incoming packets, then makes a decision of whether this node is congested. Two mechanisms are implemented in this protocol in order to alleviate congestion. First, congestion is detected based on the required packet service time. After congestion is detected, each node will increase the duration of their active state based on the calculated congestion degree. Then a congestion notification message is broadcast by the congested node. When a node receives a congestion notification message, it will adjust its transmission rate. The rate reduction on a node is equal to the required service time over the maximum duty cycle active state in that node.
M. Anwander propose BEAM: a burst aware energy efficient adaptive MAC
protocol for WSN [17]. The BEAM protocol is designed as an improvement upon
X-MAC. The BEAM protocol comprises two different operational modes to op- timise receiver sleep time dependent on the payload size. Both modes rely on positive acknowledgments of MAC frames upon reception. The two operational modes of this protocol are: a) basic operation mode, b) short preambles mode. In the first mode, the receivers wake-up and listen to the channel. If the receiver’s address matches the address in the preamble an ack frame is transmitted. A sender node will continuously transmit a short preamble with payload frame until a positive acknowledgment is received. In the second mode, the receiver listens to the channel for preamble frames. If the address in the preamble matches the receiver’s address an ack frame is transmitted. Upon the reception of an ack frame the sender is informed that the receiver is awake and transmits the data frame. BEAM’s switching between these two states depends in the payload size (for pack- ets with more than 40 byte payload, basic operation mode is used). Furthermore, BEAM can transmit more than one frame to the same neighbour (packets can be aggregated) if there is enough space for both packets in a single MAC frame. During a strong traffic increase, BEAM uses 1 bit information (traffic indicator) in the frame control field (FCF) of every transmitted frame in order to inform its parent node about the traffic increase. Upon the reception of a frame with the traffic indicator bit set, a node will adapt its listen cycle by calculating an earlier time to wake-up.
H. Hu et al. propose ADC-SMAC [81]: an improvement of S-MAC based on
dynamic duty cycle. In ADC-SMAC, each node periodically calculate its utilisa- tion and sleeping delay. This information is then used for the calculation of a new duty cycle. After the calculation of the new duty cycle, nodes will share the in- formation with their neighbours. In ADC-SMAC the information sharing between neighbour nodes is performed through the transmission of broadcast frames.
H. Yoo et al. propose DSR [82]: duty cycle scheduling based on residual energy.
up. The duty cycle at each node is then calculated based on the residual energy. The algorithm used for the duty cycle calculation in DSR can is:
Idci = Idcmax− (Imax dc × Ei r− Eth Emax− Eth ) (2.1) were Ii
dc is the current duty cycle, Idcmax is the maximum duty cycle, Eri is
the nodes residual energy, Emax is the maximum residual energy and Eth is the
residual energy threshold.