Contention based MAC protocols

Contention based MAC protocols

1. contention based mac protocols Darwin Nesakumar A, M.E, ( P.hD ) Assistant Professor Department of ECE R.M.K. Engineering College

2. Agenda Review of previous session Contention based protocols in WSN PAMAS Protocol Low duty Cycle and Wake up Concepts SPIN -Sensor Protocols for Information via Negotiation Quizzes 2 Contention based protocols Tuesday, 01 September 2020

3. Review of previous session Joinmyquiz.com 3 Contention based protocols Tuesday, 01 September 2020

4. Question Upon each periodic wakeup, a node transmits a _______ query beacon, indicating its node address and its willingness to accept packets from other nodes. Short Medium Long Contention based protocols 4 Tuesday, 01 September 2020

5. Answer for the Question Short Contention based protocols 5 Tuesday, 01 September 2020

6. Question What is the purpose of Mediation device? Contention based protocols 6 Tuesday, 01 September 2020

7. Answer for the Question Dynamic synchronization Contention based protocols 7 Tuesday, 01 September 2020

8. Question Mediation device is power constrained. TRUE FALSE Contention based protocols 8 Tuesday, 01 September 2020

9. Answer for the Question FALSE Contention based protocols 9 Tuesday, 01 September 2020

10. Question When the MD registers collisions, it might start to emit a dedicated reschedule control frame to ________ nodes. All Neighboring Colliding Contention based protocols 10 Tuesday, 01 September 2020

11. Answer for the Question Colliding Contention based protocols 11 Tuesday, 01 September 2020

12. Question Mediation device is energy _____________ Constrained Unconstrained Contention based protocols 12 Tuesday, 01 September 2020

13. Answer for the Question Unconstrained Contention based protocols 13 Tuesday, 01 September 2020

14. Question S-MAC protocol provides mechanisms to avoid/ to bypass idle listening, collisions, and overhearing. Contention based protocols 14 Tuesday, 01 September 2020

15. Answer for the Question True Contention based protocols 15 Tuesday, 01 September 2020

16. Question S-MAC adopts a periodic wakeup scheme True False Contention based protocols 16 Tuesday, 01 September 2020

17. Answer for the Question True Contention based protocols 17 Tuesday, 01 September 2020

18. Question S-MAC attempts to coordinate the schedules of neighboring nodes True False Contention based protocols 18 Tuesday, 01 September 2020

19. Answer for the Question True Contention based protocols 19 Tuesday, 01 September 2020

20. Question S – MAC requires two different channels TRUE FALSE Contention based protocols 20 Tuesday, 01 September 2020

21. Answer for the Question FALSE Contention based protocols 21 Tuesday, 01 September 2020

22. Question In S-MAC, the __________________is used to reduce collisions of data packets due to hidden-terminal situations. RTS/CTS handshake RTS/CTS Milkshake RTS/CTS legshake Contention based protocols 22 Tuesday, 01 September 2020

23. Answer for the Question RTS/CTS handshake Contention based protocols 23 Tuesday, 01 September 2020

24. Question What are the three phases of listen period? Contention based protocols 24 Tuesday, 01 September 2020

25. Answer for the Question Synchronization Phase RTS Phase CTS Phase Contention based protocols 25 Tuesday, 01 September 2020

26. IMPORTANT POINTS TO BE REMEMBER MAC Protocols MAC – Medium Access Control They coordinate the times where a number of nodes access a shared communication medium . Main requirement – Energy efficiency Energy waste due to – Overhead, Overhearing, Collisions and idle listening Switch the transceiver into Sleep Mode – Energy saving approach There are trade offs between energy expenditure and delay, throughput MAC is first protocol above the Physical layer (PHY) Fundamental task is to regulate the access of number of nodes to a shared medium Few traditional criteria are delay, throughput, fairness Energy conservation is an issue in MAC MAC is apart of Data Link Layer (DLL) – OSI reference model MAC protocol determines for a node the points in time when it accesses the medium to try to transmit a data, control, or management packet to another node (unicast) or to a set of nodes (multicast, broadcast ). 26 Contention based protocols Tuesday, 01 September 2020

27. IMPORTANT POINTS TO BE REMEMBER MAC Protocols MAC is a part of Data Link Layer (DLL) DLL Responsibilities are Error Control – used to ensure correctness of transmission and to take appropriate actions in case of transmission errors F low control - regulates the rate of transmission to protect a slow receiver from being overwhelmed with data Main approach to conserve energy – Put nodes in sleep state whenever possible Low duty cycle, Wake up concepts Two types of MAC Protocols are Contention based and schedule based Contention based – It is a communication protocol for operating wireless telecommunication equipment that allows many users to use same radio channel without pre coordination Schedule based - A schedule exists, regulating which participant may use which resource at which time 27 Contention based protocols Tuesday, 01 September 2020

28. SCHEDULE- VS. CONTENTION-BASED MAC Schedule-based MAC A schedule exists, regulating which participant may use which resource at which time (TDMA component) Typical resource: frequency band in a given physical space (with a given code, CDMA) Schedule can be fixed or computed on demand Usually: mixed – difference fixed/on demand is one of time scales Usually, collisions, overhearing, idle listening no issues Needed: time synchronization! Contention-based protocols Risk of colliding packets is deliberately taken Hope: coordination overhead can be saved, resulting in overall improved efficiency Mechanisms to handle/reduce probability/impact of collisions required Usually, randomization used somehow 28 Contention based protocols Tuesday, 01 September 2020

29. IMPORTANT POINTS TO BE REMEMBER LEACH Protocol Given: Dense network of nodes, reporting to a central sink, each node can reach sink directly Group of nodes – Cluster, controlled by clusterhead Clusterheads organize CDMA code for all member transmissions, TDMA schedule to be used within a cluster CHs collect & aggregate data from all cluster members, aggregates the data from members and forwards to sink using CDMA About 5% of nodes become clusterhead , Role of clusterhead is rotated to share the burden Two phases – Set up phase and steady state phase Set up phase – Election of Clusterhead , advertisement of Clusterhead to the members via broadcasting Setup phase – CH assigns TDMA for members, CDMA for transmitting the data to sink TDMA – Intra Cluster CDMA – Inter Cluster 29 Contention based protocols Tuesday, 01 September 2020

30. IMPORTANT POINTS TO BE REMEMBER LEACH Protocol Steady State Phase : CHs collect & aggregate data from all cluster members, report aggregated data to sink using CDMA The cluster-head is maintained when data is transmitted between nodes. CH is responsible for creating and maintaining a TDMA schedule; all the other nodes of a cluster are member nodes. To all member nodes, TDMA slots are assigned, which can be used to exchange data between the member and the clusterhead . With the exception of their time slots, the members can spend their time in sleep state. The clusterhead aggregates the data of its members and transmits it to the sink node or to other nodes for further relaying. Since the sink is often far away, the clusterhead must spend significant energy for this transmission. For a member, it is typically much cheaper to reach the clusterhead than to transmit directly to the sink There is no peer-to-peer communication. 30 Contention based protocols Tuesday, 01 September 2020

31. IMPORTANT POINTS TO BE REMEMBER LEACH Protocol Advantages Increases the lifetime of the network, Even drain of energy Distributed, no global knowledge required Energy saving due to aggregation by CHs TDMA- Nodes assigned with time slot for transmission and let them sleep at all other times. Transmission schedules achieve no collisions occur at receivers and hence no special mechanisms are needed to avoid hidden-terminal situations. 31 Contention based protocols Tuesday, 01 September 2020

32. IMPORTANT POINTS TO BE REMEMBER LEACH Protocol The setup and maintenance of schedules involves signaling traffic. If a TDMA variant is employed, time is divided into comparably small slots Such schedules are not easily adapted to different load situations on small timescales. The schedule of a node (and possibly those of its neighbors) may require a significant amount of memory, which is a scarce resource in several sensor node designs. Disadvantages LEACH assumes all nodes can transmit with enough power to reach BS if necessary (e.g., elected as CHs) Each node should support both TDMA & CDMA Need to do time synchronization Nodes use single-hop communication LEACH would not be able to cover large geographical areas of some square miles or more, because a clusterhead two miles away from the sink likely does not have enough energy to reach the sink at all. 32 Contention based protocols Tuesday, 01 September 2020

33. IMPORTANT POINTS TO BE REMEMBER Mediation Device Protocol To transmit packets after wake up period When a node wants to transmit a packet to a neighbor, it has to synchronize with it. One option would be to have the sender actively waiting for query beacon, but this wastes considerable energy for synchronization purposes only. The dynamic synchronization approach achieves this synchronization without requiring the transmitter to be awake permanently to detect the destinations query beacon. To achieve this, a mediation device (MD) is used. We first discuss the case where the mediation device is not energy constrained and can be active all the time. It allows each node in a WSN to go into sleep mode periodically and to wake up only for short times to receive packets from neighbor nodes. There is no global time reference , each node has its own sleeping schedule, and does not take care of its neighbors sleep schedules. To receive packets after wake up period Upon each periodic wakeup, a node transmits a short query beacon , indicating its node address and its willingness to accept packets from other nodes. The node stays awake for some short time following the query beacon, to open up a window for incoming packets. If no packet is received during this window, the node goes back into sleep mode. 33 Contention based protocols Tuesday, 01 September 2020

34. IMPORTANT POINTS TO BE REMEMBER S-MAC Protocol A node x’s listen period is subdivided into three different phases - Synchronization Phase , RTS Phase, CTS Phase Synchronization Phase In this phase node x accepts SYNCH packets from its neighbors. In these packets, the neighbors describe their own schedule and x stores their schedule in a table (the schedule table). Node x’s SYNCH phase is subdivided into time slots, each neighbor y wishing to transmit a SYNCH packet picks one of the time slots randomly and starts to transmit if no signal was received in any of the previous slots. S-MAC stands for Sensor – Medium Access Control S-MAC protocol provides mechanisms to avoid/ to bypass idle listening, collisions, and overhearing. It does not require two different channels. S-MAC adopts a periodic wakeup scheme , that is, each node alternates between a fixed-length listen period and a fixed-length sleep period according to its schedule. The listen period of S-MAC can be used to receive and transmit packets. S-MAC attempts to coordinate the schedules of neighboring nodes such that their listen periods start at the same time. 34 Contention based protocols Tuesday, 01 September 2020

35. IMPORTANT POINTS TO BE REMEMBER S-MAC Protocol In general, when competing for the medium, the nodes use the RTS/CTS handshake, including the virtual carrier-sense mechanism , whereby a node maintains a NAV variable. The NAV ( Network Allocation Vector – Virtual Carrier Sensing) mechanism can be readily used to switch off the node during ongoing transmissions to avoid overhearing. If we can arrange that the schedules of node x and its neighbors are synchronized, node x and all its neighbors wake up at the same time and x can reach all of them with a single SYNCH packet. RTS Phase In this second phase x listens for RTS packets from neighboring nodes. In S-MAC, the RTS/CTS handshake is used to reduce collisions of data packets due to hidden-terminal situations. Again, interested neighbors contend in this phase according to a CSMA scheme with additional backoff . CTS Phase In the third phase node x transmits a CTS packet if an RTS packet was received in the previous phase. After this, the packet exchange continues, extending into x’s nominal sleep time. 35 Contention based protocols Tuesday, 01 September 2020

36. CONTENTION-BASED PROTOCOLS Tuesday, 01 September 2020 Contention based protocols 36

37. CONTENTION-BASED PROTOCOLS If only one neighbor tries its luck, the packet goes through the channel. If two or more neighbors try their luck, these have to compete with each other and in unlucky cases, for example, due to hidden-terminal situations, a collision might occur, wasting energy for both transmitter and receiver. T wo important contention based protocols: (slotted) ALOHA and CSMA, along with mechanisms to solve the hidden-terminal problem. We discuss variations of these protocols with the goal to conserve energy. As opposed to some of the contention-based protocols having a periodic wakeup scheme T he protocols described in this section have no idle listening avoidance and make no restrictions as to when a node can receive a packet. 37 Contention based protocols Tuesday, 01 September 2020

38. The PAMAS protocol (Power Aware Multi-access with Signaling) Originally designed for ad hoc networks. It provides a detailed overhearing avoidance mechanism while it does not consider the idle listening problem. The protocol combines the busy-tone solution and RTS/CTS handshake similar to the MACA protocol A distinctive feature of PAMAS is that it uses two channels : Data channel (while the data channel is reserved for data packets) Control channel . (All the signaling packets (RTS, CTS, busy tones) are transmitted on the control channel. 38 Contention based protocols Tuesday, 01 September 2020

39. Question PAMAS Protocol provides a detailed _____________ avoidance mechanism Overhearing Over head Collision Contention based protocols 39 Tuesday, 01 September 2020

40. Answer for the Question Overhearing Contention based protocols 40 Tuesday, 01 September 2020

41. Question What are the two channels that PAMAS protocol uses? Contention based protocols 41 Tuesday, 01 September 2020

42. Answer for the Question Data Channel Control Channel Contention based protocols 42 Tuesday, 01 September 2020

43. Question The protocol combines the _________solution and RTS/CTS handshake similar to the MACA protocol Ring -tone Busy-tone Contention based protocols 43 Tuesday, 01 September 2020

44. Answer for the Question Busy-tone Contention based protocols 44 Tuesday, 01 September 2020

45. Question RTS, CTS packets, busy tone are transmitted through Data Channel Control Channel Contention based protocols 45 Tuesday, 01 September 2020

46. Answer for the Question Control Channel Contention based protocols 46 Tuesday, 01 September 2020

47. PAMAS PROTOCOL Let us consider an idle node x to which a new packet destined to a neighboring node y arrives. First, x sends an RTS packet on the control channel without doing any carrier sensing. This packet carries both x’s and y’s MAC addresses. If y receives this packet, it answers with a CTS packet if y does not know of any ongoing transmission in its vicinity. Upon receiving the CTS, x starts to transmit the packet to y on the data channel. When y starts to receive the data, it sends out a busy-tone packet on the control channel. If x fails to receive a CTS packet within some time window, it enters the backoff mode, where a binary exponential backoff scheme is used (i.e., the backoff time is uniformly chosen from a time interval that is doubled after each failure to receive a CTS). Tuesday, 01 September 2020 Contention based protocols 47

48. Question If x fails to receive a CTS packet within some time window, it enters the ___________ Normal mode Synchronized mode Backoff mode Contention based protocols 48 Tuesday, 01 September 2020

49. Answer for the Question Backoff mode Contention based protocols 49 Tuesday, 01 September 2020

50. Question Backoff time is uniformly chosen from a time interval that is __________after each failure to receive a CTS Added Doubled Multiplied Contention based protocols 50 Tuesday, 01 September 2020

51. Answer for the Question Doubled Contention based protocols 51 Tuesday, 01 September 2020

52. PAMAS PROTOCOL Now, let us look at the nodes receiving x’s RTS packet on the control channel. There is the intended receiver y and there are other nodes; let z be one of them. If z is currently receiving a packet, it reacts by sending a busy-tone packet, which overlaps with y’s CTS at node x and effectively destroys the CTS. Therefore, x cannot start transmission and z’s packet reception is not disturbed. Since the busy-tone packet is longer than the CTS, we can be sure that the CTS is really destroyed. We consider the intended receiver y. If y knows about an ongoing transmission in its vicinity, it suppresses its CTS, causing x to back off. Tuesday, 01 September 2020 Contention based protocols 52

53. Question Busy tone packet is shorter than CTS True False Contention based protocols 53 Tuesday, 01 September 2020

54. Answer for the Question False Contention based protocols 54 Tuesday, 01 September 2020

55. PAMAS PROTOCOL Node y can obtain this knowledge by either sensing the data channel or by checking whether there was some noise on the control channel immediately after receiving the RTS. This noise can be an RTS or CTS of another node colliding at y. In the other case, y answers with a CTS packet and starts to send out a busy-tone packet as soon as x’s transmission has started. Furthermore, y sends out busy-tone packets each time it receives some noise or a valid packet on the control channel, to prevent its neighborhood from any activities. Tuesday, 01 September 2020 Contention based protocols 55

56. PAMAS - Power Aware Multi access with Signaling Idea: C ombine busy tone with RTS/CTS Results in detailed overhearing avoidance, does not address idle listening Uses separate data and control channels Procedure Node A transmits RTS on control channel, does not sense channel Node B receives RTS, sends CTS on control channel if it can receive and does not know about ongoing transmissions B sends busy tone as it starts to receive data Time Control channel Data channel RTS A ! B CTS B ! A Data A ! B Busy tone sent by B 56 Contention based protocols Tuesday, 01 September 2020

57. PAMAS – Already ongoing transmission Suppose a node C in vicinity of A is already receiving a packet when A initiates RTS Procedure A sends RTS to B C is sending busy tone (as it receives data) CTS and busy tone collide, A receives no CTS, does not send data A B C ? Time Control channel Data channel RTS A ! B CTS B ! A No data! Busy tone by C Similarly: Ongoing transmission near B destroys RTS by busy tone 57 Contention based protocols Tuesday, 01 September 2020

58. PAMAS - Power Aware Multi access with signaling Node X Node y RTS CTS Busy Tone First, x sends an RTS packet on the control channel without doing any carrier sensing. This packet carries both x’s and y’s MAC addresses If y receives this packet, it answers with a CTS packet if y does not know of any ongoing transmission in its vicinity. Upon receiving the CTS, x starts to transmit the packet to y on the data channel. When y starts to receive the data, it sends out a busy-tone packet on the control channel. If x fails to receive a CTS packet within some time window, it enters the backoff mode, where a binary exponential backoff scheme is used (i.e., the backoff time is uniformly chosen from a time interval that is doubled after each failure to receive a CTS) 58 Contention based protocols Tuesday, 01 September 2020

59. Node X Node y RTS CTS Busy Tone If y knows about an ongoing transmission in its vicinity, it with a CTS packet and starts to send out a busy-tone packet as soon as x’s transmission has started. suppresses its CTS, causing x to back off. Node y can obtain this knowledge by either sensing the data channel or by checking whether there was some noise on the control channel immediately after receiving the RTS. This noise can be an RTS or CTS of another node colliding at y. In the other case, y answers Furthermore, y sends out busy-tone packets each time it receives some noise or a valid packet on the control channel, to prevent its neighborhood from any activities. 59 Contention based protocols Tuesday, 01 September 2020

60. Question PAMAS refers to Contention based protocols 60 Tuesday, 01 September 2020

61. Answer for the Question PAMAS - Power Aware Multi access with Signaling Contention based protocols 61 Tuesday, 01 September 2020

62. When can a node put its transceivers (control and data) into sleep mode? Any time a node knows that it cannot transmit or receive packets because some other node in its vicinity is already doing so. This decision is easy if a node x knows about the length of an ongoing transmission, for example from overhearing the RTS or CTS packets or the header of the data packets on the data channel. However, often this length is unknown to x, for example, because these packets are corrupted or a foreign data transmission cycle starts when x is just sleeping. Additional procedures are needed to resolve this 62 Contention based protocols Tuesday, 01 September 2020

63. When can a node put its transceivers (control and data) into sleep mode? Suppose that x wakes up and finds the data channel busy. There are two cases to distinguish: Case 1 E ither x has no own packet to send or x wants to transmit. In the first case, x desires to go back into sleep mode and to wake up exactly when the ongoing transmission ends to be able to receive an immediately following packet. Waking up at the earliest possible time has the advantage of avoiding unwanted delays. However, since x may not have overheard the RTS, CTS, or data packet header belonging to the ongoing transmission, it runs a probing protocol on the control channel to inquire the length of the ongoing packet. 63 Contention based protocols Tuesday, 01 September 2020

64. Question A node runs a _____________on the control channel to inquire the length of the ongoing packet. Probing protocol Problem solving protocol Contention based protocols 64 Tuesday, 01 September 2020

65. Answer for the Question Probing protocol Contention based protocols 65 Tuesday, 01 September 2020

66. When can a node put its transceivers (control and data) into sleep mode? Case 2 x wakes up during an ongoing transmission and wants to transmit a packet. Therefore, x has not only to take care of ongoing transmissions but also of ongoing receptions in its vicinity. To find the time for the next wakeup, x runs the described probing protocol for the set of transmitters, giving a time t when the longest ongoing transmission ends. Tuesday, 01 September 2020 Contention based protocols 66

67. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS Tuesday, 01 September 2020 Contention based protocols 67

68. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS Low duty cycle protocols try to avoid spending (much) time in the idle state and to reduce the communication activities of a sensor node to a minimum. In an ideal case, the sleep state is left only when a node is about to transmit or receive packets. Periodic wake up scheme In this approach, nodes spend most of their time in the sleep mode and wake up periodically to receive packets from other nodes. Specifically, a node A listens onto the channel during its listen period and goes back into sleep mode when no other node takes the opportunity to direct a packet to A. Tuesday, 01 September 2020 Contention based protocols 68

69. Question Low duty cycle protocols try to avoid spending (much) time in the _______________ Idle state Wake up state Sleep state Contention based protocols 69 Tuesday, 01 September 2020

70. Answer for the Question Idle state Contention based protocols 70 Tuesday, 01 September 2020

71. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS Method 1 Transmitter B must acquire knowledge about A’s listen periods to send its packet at the right time, this task corresponds to a rendezvous. Node A transmit a short beacon at the beginning of its listen period to indicate its willingness to receive packets. Tuesday, 01 September 2020 Contention based protocols 71

72. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS Method 2 This method is to let node B send frequent request packets until one of them hits A’s listen period and is really answered by A Tuesday, 01 September 2020 Contention based protocols 72

73. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS Method 1 – B knows A’s listen time and send packets at right time Method 2 – B sends RTS to A’s listen period untill A answers (B does not know A’s listen time) However, in either case, node A only receives packets during its listen period. If node A itself wants to transmit packets, it must acquire the target’s listen period. A whole cycle consisting of sleep period and listen period is also called a wakeup period. The ratio of the listen period length to the wakeup period length is also called the node’s duty cycle . Tuesday, 01 September 2020 Contention based protocols 73

74. Question Sleep period + Listen period = Idle period Wakeup period Transmission period Contention based protocols 74 Tuesday, 01 September 2020

75. Answer for the Question Wakeup period Contention based protocols 75 Tuesday, 01 September 2020

76. Question The ratio of listen period length to wakeup period length is also called the node’s_________ Sleep period Duty cycle Time period Contention based protocols 76 Tuesday, 01 September 2020

77. Answer for the Question Duty cycle Contention based protocols 77 Tuesday, 01 September 2020

78. LOW DUTY CYCLE PROTOCOLS AND WAKEUP CONCEPTS By choosing a small duty cycle , the transceiver is in sleep mode most of the time , avoiding idle listening and conserving energy. By choosing a small duty cycle, the traffic directed from neighboring nodes to a given node concentrates on a small time window (the listen period) and in heavy load situations significant competition can occur. Choosing a long sleep period (Small duty cycle) induces a significant per-hop latency, since a prospective transmitter node has to wait an average of half a sleep period before the receiver can accept packets. In the multihop case, the per-hop latencies add up and create significant end-to-end latencies. Sleep phases should not be too short lest the start-up costs outweigh the benefits. Tuesday, 01 September 2020 Contention based protocols 78

79. Question What are the three periods available in periodic wakeup scheme? Contention based protocols 79 Tuesday, 01 September 2020

80. Answer for the Question Wake up period Sleep Period Listening Period Contention based protocols 80 Tuesday, 01 September 2020

81. Question For small duty cycle, the sleep time of the node is very long. TRUE FALSE Contention based protocols 81 Tuesday, 01 September 2020

82. Answer for the Question TRUE Contention based protocols 82 Tuesday, 01 September 2020

83. Question Sleep phase should be short or long ? Contention based protocols 83 Tuesday, 01 September 2020

84. Answer for the Question Short Contention based protocols 84 Tuesday, 01 September 2020

85. Question The ratio of the listen period length to the wakeup period length is also called Contention based protocols 85 Tuesday, 01 September 2020

86. Answer for the Question Node’s duty cycle Contention based protocols 86 Tuesday, 01 September 2020

87. Sensor Protocols for Information via Negotiation (SPIN) A Negotiation-Based Protocols for Disseminating Information in Wireless Sensor Networks. Dissemination is the process of distributing individual sensor observations to the whole network , treating all sensors as sink nodes Replicate complete view of the environment Enhance fault tolerance Broadcast critical piece of information SPIN -Sensor Protocols for Information via Negotiation 87 Contention based protocols Tuesday, 01 September 2020

88. Question The process of distributing individual sensor observations to the whole network, treating all sensors as sink nodes is called Determination Distribution Dissemination Contention based protocols 88 Tuesday, 01 September 2020

89. Answer for the Question Dissemination Contention based protocols 89 Tuesday, 01 September 2020

90. Flooding is the classic approach for dissemination Source node sends data to all neighbors Receiving node stores and sends data to all its neighbors Disseminate data quickly Deficiencies Implosion Overlap Resource blindness SPIN -Sensor Protocols for Information via Negotiation 90 Contention based protocols Tuesday, 01 September 2020

91. Question Which approach is used for dissemination ? Flooding Distributing Contention based protocols 91 Tuesday, 01 September 2020

92. Answer for the Question Flooding Contention based protocols 92 Tuesday, 01 September 2020

93. Negotiation Before transmitting data, nodes negotiate with each other to overcome implosion and overlap Only useful information will be transferred Observed data must be described by meta-data Resource adaptation Each sensor node has resource manager Applications probe manager before transmitting or processing data Sensors may reduce certain activities when energy is low SPIN -Sensor Protocols for Information via Negotiation 93 Contention based protocols Tuesday, 01 September 2020

94. SPIN : A three-stage handshake protocol for point-to-point media ADV – data advertisement Node that has data to share can advertise this by transmitting an ADV with meta-data attached REQ – request for data Node sends a request when it wishes to receive some actual data DATA – data message Contain actual sensor data with a meta-data header Usually much bigger than ADV or REQ messages SPIN -Sensor Protocols for Information via Negotiation 94 Contention based protocols Tuesday, 01 September 2020

95. SPIN -Sensor Protocols for Information via Negotiation 95 Contention based protocols Tuesday, 01 September 2020

96. EECDA (Energy Efficient Clustering and Data Aggregation) Protocol After the CHs election, a path with maximum sum of residual energy would be selected for data communication instead of the path with minimum energy consumption. Therefore, each CH first aggregates the received data and then transmits the aggregated data to the Base Station (BS). The main contributions of EECDA protocol is to provide longest stability and improves the network lifetime 96 Contention based protocols Tuesday, 01 September 2020

97. Energy-Aware Unequal Clustering with Fuzzy (EAUCF) EAUCF is a distributed competitive unequal clustering algorithm. It makes local decisions for determining competition radius and electing cluster-heads. In order to estimate the competition radius for tentative cluster-heads, EAUCF employs both residual energy and distance to the base station parameters. EAUCF aims to decrease the work of the cluster-heads that are either close to the base station or have low remaining battery power. A fuzzy logic approach is adopted in order to handle uncertainties in cluster-head radius estimation. 97 Contention based protocols Tuesday, 01 September 2020

98. Question EAUCF aims to decrease the work of the cluster-heads that are either close to the base station or have low remaining battery power. True False Contention based protocols 98 Tuesday, 01 September 2020

99. Answer for the Question True Contention based protocols 99 Tuesday, 01 September 2020

100. Routing protocol is based on ANT colony highly adaptive, efficient and scalable ANTS travel through the WSN looking for path between sensor nodes and a destination node that are both short in length and energy efficient An Energy Efficient ANT Based Routing algorithm (EEABR) 100 Contention based protocols Tuesday, 01 September 2020

101. Forward ANTS (FANT) and backward ANTS (BANT). A forward ANT is launched periodically from every node ANT stores the identifiers of all the nodes it visits S election probability is a trade-off between visibility(Energy) and actual trail intensity BANT sent back along the path stored An Energy Efficient ANT Based Routing algorithm (EEABR)-con 101 Contention based protocols Tuesday, 01 September 2020

102. Active query routed Resolves query partially in each node Next node can be selected randomly or selected intelligently based on other information Query gets resolved as quickly as possible Last active node answers the last remaining piece of the original query ACtive QUery forwarding In sensoR nEtworks (ACQUIRE) 102 Contention based protocols Tuesday, 01 September 2020

103. Natural information gradient Gradient is known as fingerprint f ( d ) = t / d2. Regions Flat region Gradient region RoUting on finGerprint Gradient in sEnsor networks (RUGGED) 103 Contention based protocols Tuesday, 01 September 2020

104. there could be multiple gradient regions active A query may be initiated at any arbitrary node If the node is in a flat region, It uses flooding to forward the query It sets the query mode to flat region mode The query doesn’t switch to the gradient mode unless gradient information is found RoUting on finGerprint Gradient in sEnsor networks (RUGGED)-con 104 Contention based protocols Tuesday, 01 September 2020

105. If the node is in gradient information region Uses a greedy forwarding approach well suited for broad range of applications time gradient based target tracking, event boundary detection. RoUting on finGerprint Gradient in sEnsor networks (RUGGED)-con 105 Contention based protocols Tuesday, 01 September 2020

106. Three categories Data-centric Hierarchical Location based routing Classification of WSN routing protocols 106 Contention based protocols Tuesday, 01 September 2020

107. Demand Assignment Protocols Resources are allocated on a short term basis Centralized and distributed versions are possible Central Nodes request a reource (e.g. time slot) from a central server Waits for ACK and then trans mits Polling by central station is possible Central server to be switced on always Central node requires a lot of energy Central node may be rotated (LEACH) 107 Contention based protocols Tuesday, 01 September 2020

108. Centralized medium access Idea: Have a central station control when a node may access the medium Example: Polling, centralized computation of TDMA schedules Advantage: Simple, quite efficient (e.g., no collisions), burdens the central station Not directly feasible for non-trivial wireless network sizes But: Can be quite useful when network is somehow divided into smaller groups Clusters, in each cluster medium access can be controlled centrally – compare Bluetooth piconets , for example ! Usually, distributed medium access is considered 108 Contention based protocols Tuesday, 01 September 2020

109. Preamble Sampling So far: Periodic sleeping supported by some means to synchronize wake up of nodes to ensure rendez-vous between sender and receiver Alternative option: Don’t try to explicitly synchronize nodes Have receiver sleep and only periodically sample the channel Use long preambles to ensure that receiver stays awake to catch actual packet Example: WiseMAC Check channel Check channel Check channel Check channel Start transmission: Long preamble Actual packet Stay awake! 109 Contention based protocols Tuesday, 01 September 2020

110. THANK YOU 110 Contention based protocols Tuesday, 01 September 2020