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11:27 @ AD NEA ll 26%0, , DECODE Wireless Sen..., x a kopykitab.com H <, , O Notes @ BY 48 -of 164, , , , Radio Communication, , , , , , , , , , , , , , , , , , , , Wireless Sensor Networks 2-27 and Link Management, Fixed-length round, seeseeeeeeee Setup phase Steady-state phase, Time sioi]rime slo] [Time slot Time slot, “to 2_ |" Q 1, , , , , , , , , , , , , , , , , , , , Advertisement phase] Cluster setup phase | Broadcast schedule, , f, , , , , , , , , , , , Clusterheads Members, Self-election of compete with compete with, clusterheads CSMA CSMA, , Fig. Q.14.2 LEACH round organization, , ¢ The first phase is setup phase. The setup phase consists of two, steps, cluster-head selection and cluster formation., ¢ The second phase is the steady-state phase. The steady-state, phase focuses on data collection, aggregation, and delivery to, the base station., ¢ In steady state operation:, CHs collect & aggregate data from all cluster members, © Report aggregated data to sink using COMA, ¢ The duration of the setup is assumed to be relatively shorter, than the steady-state phase to minimize the protocol overhead., , 2. Self Organizing Medium Access Control for Sensor Networks, (SMACS), , *« SMACS is a schedule based medium access control protocol, for the wireless sensor network., , e¢ This MAC protocol uses a combination of TDMA and FDMA, or CDMA for accessing the channel., , e In this protocol the time slots are wasted if the sensor node, does not have data to be sent to the intended receivers. This is, one of the drawbacks of this MAC scheme., , e, @ Less than PHOTOCOPY Price, , , , , , I O <

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11:26 fl AD NEA ll 26%0, , DECODE Wireless Sen... :, x @ kopykitab.com H < °, , O Notes @ BY vel, , , , , , Radio Communication, Wireless Sensor Networks 2-26 and Link Management, , , , e LEACH network model is shown in Fig. Q14.1., , (‘y"), A Data sink, at, , , , (e) © Cluster member, © Cluster head, Fig. Q14.1 LEACH network, «The cluster head forwards to the base station messages, received from its cluster nodes., , e A transmitter-based code assignment scheme is used to reduce, inter-cluster interference., , ¢ Direct - Sequence Spread Spectrum (DSSS) technique is used, to communicate between node and its cluster head., , « A fixed spreading code and CSMA is used to communicate, between a cluster and a base station., , *¢ LEACH distributes the cluster-head role to all nodes; they, tend to die at about the same time. The protocol is organized, in rounds and each round is subdivided into a setup phase, and a steady-state phase., , Fig. Q.14.2 illustrates organization of LEACH rounds., , , , , , Il O <

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11:26 a AO NES ll 26%0, , DECODE Wireless Sen..., * a kopykitab.com H <, , O Notes @ BY 46 ~of 1, , , , , , Radio Communication, , , , , , , , , , , , , , , , , , , , , , , , , , Wireless Sensor Networks 2-25 and Link Management, If medium idle,, Arrival, wait for transmit, tight moment, Source WalT [WI Data | Sampling, - schedule, Tp information, O DOZE, Destination Tw G Rx, Oo oO Wake up, om, Wake up, Wake up, medium busy, = T) = Ty To, medium idle = mediumidle receive message, Fig. Q.13.5, , ¢ In WiseMAC protocol, nodes are not synchronized to wake up, simultaneously and this reduces the synchronization overhead., , ¢ On the other hand, since a receiving node turns on its radio for a, short period (<T,,), the transmitting node should transmit along a, signal of size equal to T,,., , Q.14 Explain various schedule based protocols., Ans. : Scheduled based protocols are :, 1. LEACH 2. SMACS 3. TRAMA, , 1. Low-Energy Adaptive Clustering Hierarchy (LEACH), , « A WSN is dense network of nodes, reporting to a central sink,, each node can reach sink directly., , ¢ Group nodes are divided into clusters, which are controlled by, clusterhead (CH)., , e About 5 % of nodes become clusterhead (depends on, scenario)., , ¢ Role of clusterhead is rotated to share the burden., , ¢ Clusterheads advertise themselves, ordinary nodes join CH, with strongest signal, , ¢ Clusterheads organizes :, , © CDMA code for all member transmissions, , ° TDMA schedule to be used within a cluster, , , , , , @, DECODE ) @ Less than PHOTOCOPY Price, , III O <

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11:26 a AO NES He ll 26% 0, , DECODE Wireless Sen..., * a kopykitab.com H <, , 00 Notes @€ FY cle, EE, , , , Radio Communication, Wireless Sensor Networks 2-24 and Link Management, , Pete tbtt ct, , active sleep, , suc tt 1 {, , , , , , , , , , , , , , , , , , , , Pets tht pitt, , , , , , , , , , , , , , , , , , active sleep, TA [TA\ A,, me (HRA, Fig. Q.13.3, , ¢ The following equation defines the minimum value of TA, as, shown in Fig. Q.13.3., TA > C+T+R, C : Contention time, R : Propagation time for RTS packet, T : Transmission time for RTS packet, , 5, , 3. Wireless Sensor MAC (WiseMAC) Protocol, , ¢ WiseMAC is a protocol where all nodes in the network wake up, periodically with period Tw, to check for any activity of the, medium, as shown in Fig. Q.13.5., , @ Less than PHOTOCOPY Price, III O <, , cevenen RTS CTS_ Data ACK, , |, , active sleep, H, , Fig. Q.13.4

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11:26 a AO NES He ll 26% 0, , DECODE Wireless Sen..., x a kopykitab.com H <, , O Notes @ BY 44 ~0f 16#, , , , Radio Communication, Wireless Sensor Networks 2-23 and Link Management, , , , ¢ Listen interval is divided into two parts: one for receiving, SYNC packets and the other for receiving RTS (Request To, Send). Look at the Fig. Q.13.2 for more information., , c) Collision Avoidance, , e¢ SMAC uses a mechanism similar to the one used in IEEE, 802.11 for medium contention, where all immediate nodes of, both the transmitter and receiver will go to sleep upon, receiving RTS (Ready To Send) or CTS (Clear To Send), packets., 2. Timeout-MAC (TMAC) Protocol, ¢ The basic idea of T-MAC is to reduce idle listening by, introducing, © a dynamic duty cycle, © transmitting all messages in bursts of variable size in, active periods and sleeping between active periods, ¢ To maintain an optimal active period under variable traffic, load, T-MAC dynamically determines the length of an active, period by simply timing out if nothing is heard., ¢ An active period will end and the node will go to sleep if no, activation event occurred such as1) the timing out of a periodic frame timer, 2) the reception of a data packet on the radio, 3) the sensing of communication on the radio, , 4) the end of transmission of a node's own data packet or, acknowledgment, , 5) the end of transmission of a neighbour's data packet., , ¢ TMAC protocols try to enhance the energy savings in SMAC, by reducing the idle time. A node in the listen mode will go, back to sleep after time TA as shown in Fig. Q.13.3., , e If there is no activation event, the choice of TA is critical for, the performance of TMAC., , =, @ Less than PHOTOCOPY Price, , , , , , III O <