Internet DRAFT - draft-rashid-eerrd-sensornetwork

draft-rashid-eerrd-sensornetwork



Networking Working Group                  	 Md. Mamun-Or-Rashid                                                                                
Internet-Draft                                      Choong Seon Hong
Expires: April 16 , 2006                        Kyung Hee University 
                                                        Dongjin Kwak
                                          KT Advanced Technology Lab

                                                       October, 2005                                                    
                                                
  Energy Efficient Routing for Highly Dense Sensor Network Based on 
                  Residual Energy and Distance
              draft-rashid-eerrd-sensornetwork-00.txt
                    
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Abstract

   Efficient energy utilization and prolonged lifetime are two most 
   covetable targets for sensor network. For increased lifetime,each
   node must conserve energy as much as possible.  In this paper we 
   propose a protocol in which energy is conserved by amortizing the 
   energy cost of superfluous packets and idle state energy consumption
   To achieve our goal we have exercised well-known periodic sleep 
   protocol and reduce redundant transmission by creating broadcast 
   tree based on residual energy and distance based communication cost. 
   Wasteful energy consumption of sensor nodes (e.g. idle listening, 
   retransmission due to packet collision, overhearing etc) can be 
   minimized by selecting minimum number of forwarding nodes. Our 
   proposed algorithm selects minimum number of forwarding while 
   creating broadcast tree. All intermediate nodes acts as forwarding 
   node (non-leaf) while all the other nodes acts as a non-forwarding 
   (child)  reduces wasteful energy consumption by keeping radio 
   transceiver off. Simulation shows our algorithm is better in terms 
   of energy conservation and network lifetime
   

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				Table of Contents


  1.  Introduction . . . . . . . . . . . . . . . . . . . . . . .     2  


  2.  Related Energy Saving Protocols. . . . . . . . . .. . . . .    2 


  3.  Energy Consumption Analysis. . . . . . . . . . . .. . . . .    3   


  4.  Protocol Description. . . . . . . . . . . . . . . . . . . .    5


  5.  Conclusion . . . . . . . . . . . . . . . . . . . . . . . .     6











1. Introduction 
  
  Sensor network has received great magnitude of attention due to its
  diverse application area specially, in hostile environment where 
  human intervention is grueling or inopportune and sometimes 
  impossible. While the exact application of sensor network is 
  speculative, certain properties are typically assumed. First, sensors
  are static after initial deployment. Second, energy is scarce and it 
  is inconvenient or impossible to replenish the energy source 
  frequently. Sensors are deployed in a highly dense fashion. Effect of
  high density instigates the major problem of collision, overhearing 
  and redundant transmission. While deployment with less density is 
  contradictory as sensors are deployed in hostile environments and 
  also they are energy constrained so sensor nodes are porn to failure.
  Such constraints combined with a typical deployment of large number of
  sensor nodes have posed many challenges to the design and management 
  of sensor networks. These challenges necessitate energy-awareness at 


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  all layers of networking protocol stack. The issues related to 
  physical and link layers are generally common for all kind of sensor
  applications, therefore the research on these areas has been focused 
  on system-level power awareness such as dynamic voltage scaling, 
  radio communication hardware, low duty cycle issues, system 
  partitioning, energy aware MAC protocols [6][7][8]. At the network 
  layer, the main aim is to find ways for energy efficient route setup 
  and reliable relaying of data from the sensor nodes to the sink so 
  that the lifetime of the network is maximized. Energy consumption in 
  a sensor node can be due to either useful or wasteful sources. Useful
  energy consumption can be due to (i) transmitting/receiving data, 
  (ii) processing query requests, and (iii) forwarding queries/data to 
  neighboring nodes. Wasteful energy consumption can be due to (i) idle
  listening to the media, (ii) retransmitting due to packet collisions,
  (iii) overhearing, and (iv) generating/handling control packets. 
  While radios typically have four power levels corresponding the 
  following states (i) transmit (ii) receive (iii) idle and (iv) sleep.
  Our idea is to minimize wasteful energy consumption by reducing 
  redundant traffic and optimizing control message transmission while
  creating the sink rooted broadcast tree. 
    Our work minimizes redundant traffic transmission and collision 
  using sink rooted broadcast tree. The nodes will be having two status
  forwarding (non-leaf) and non-forwarding (Leaf) based on residual 
  energy and distance towards sink. Non-forwarding (Leaf) nodes are in 
  charge of sensing the vicinity and transfer sensed data through 
  forwarding (non-leaf) nodes. Our proposed algorithm tries to select 
  one forwarding node with in the transmission range. We also 
  introduced a timer parameter to control the transmission while 
  creating the tree and thus reduce collision and also reduce control 
  message transmission required to generate the tree.

2. Related Energy Saving Protocols
   
    Routing protocols of sensor network can be classified into two 
  according to network structure and protocol operation. According to
  network structure proposed protocols can be further classified into
  (i) Flat [5][10][11], (ii) Hierarchical [1]-[4][9][14] and (iii) 
  Location based [13]. While based on protocol operation is further 
  classified into (i) Negotiation based (ii) Multipath, (iii) Query 
  based, (iv) QoS based and (v) Coherent based.
    We focus on hierarchical routing protocols. In a hierarchical 
  architecture, higher energy nodes can be used to process and send 
  the information while low energy nodes can be used to perform the 
  sensing in the proximity of the target. This means that creation 
  of clusters and assigning special tasks to cluster heads can 
  greatly contribute to overall system scalability, lifetime, and 
  energy efficiency. Hierarchical routing is an efficient way to 
  lower energy consumption within a cluster and by performing data 
  aggregation and fusion in order to decrease the number of 
  transmitted messages to the BS. 


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   Heinzelman, et. al. [1] introduced a hierarchical clustering 
  algorithm for sensor networks, called Low Energy Adaptive Clustering 
  Hierarchy (LEACH). LEACH randomly selects a few sensor nodes as 
  clusterheads (CHs) and rotates this role to evenly distribute the 
  energy load among the sensors in the network. Protocol assumes that 
  all nodes can transmit with enough power to reach the BS if needed 
  and that each node has computational power to support different MAC 
  protocols. Therefore, it is not applicable to networks deployed in 
  large regions. It also assumes that nodes always have data to send, 
  and nodes located close to each other have correlated data. It is not
  obvious how the number of the predetermined CHs is going to be 
  uniformly distributed through the network. Hierarchical Power-aware 
  Routing (HPAR) protocol [15] finds the path with the least power 
  consumption by using the Dijkstra algorithm and maximizes the minimal
  residual power in the network. But wasteful energy consumption due to
  idle listening is not considered in the protocol. Energy Aware Data-
  centric (EAD) protocol [9] was proposed by Boukerche et. al. EAD 
  consider residual energy as a parameter to construct the broadcast 
  tree. The idea is to produce more non-leaf nodes to save energy as 
  well as reduced transmission. Our work differ form EAD as we have 
  considered distance as parameter. Emphasis on only residual energy 
  may generate longer paths which is undesirable as longer path 
  requires more energy to transmit.  
    Our work also generates sink rooted tree in which non-leaf and leaf
  nodes are considered as forwarding and non-forwarding nodes. In our 
  proposed tree construction we emphasize both residual energy and 
  distance which ensure a optimal forwarding node selection in terms of
  routing cost and thus achieve energy efficiency

3. Energy Consumption Analysis
  
    Sensor network is usually very dense. Certain amount of redundancy 
  is introduced for the robustness of the network. In this section we 
  will show the effect of idle nodes on per packet energy cost for 
  single hop and multi hop transmission. 

    A. Single Hop Based Analysis
       In simple case, the energy consumed by the network interface 
       when a host sends receives or discards a packet can be 
       represented using a linear equation
 	
                    Energy = P x Size + f        		  	        
      
       Trivially, there is a fixed component associated with device 
       state changes and channel acquisition overhear and an 
       incremental component which is proportional to the size of the 
       packet.  Here in the equation coefficient P represents the 
       variable cost and f is the fixed cost associated with the 
       transmission. Note that the equation does not consider about the
       media contention cost. The relative magnitude of the various P 
       and f coefficients also indicate the amount of per packet energy 
       consumption overhead.


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       A packet may be sent as broadcast or point-to point traffic. 
       Broadcast traffic received by all hosts within transmission 
       range and point-point case traffic will be discarded by non-
       destination hosts. Sensor network operates in promiscuous mode 
       and any sensed data is normally broadcast to the neighbors and 
       destined for the sink. It is very evident that  some of the 
       neighbor will be useful for forwarding the data towards the sink
       and some other will not (as sensor network is highly dense and 
       good number of redundant nodes are deployed to increase the 
       robustness of the network). So in promiscuous mode of operation 
       there will be three (broadcast, point-to-point receive and 
       discard traffic) types of energy consumption. Node sensing any 
       event will broadcast the data, nodes responsible to forward data 
       towards sink will receive data and finally nodes other than 
       receiving or sending will discard the data. Energy consumption 
       for three kinds of operation can be presented by

            Ebsend = Pbsend * Size + bsend (for broadcast send)      

       Let S be the source and N(s) be the number of nodes within one 
       hop of S. Out of N(s) neighbors let Nfrd(s) are the required 
       number of nodes for forwarding data towards sink and Nidl(s) are
       the number of idle nodes are discarding traffic. For a single 
       source scenario total energy consumption can be represented by

            Etotal = Ebsend + Nfrd(s) * Erecv + Nidl(s) * Edisc
       
       Total energy cost per bit can be calculated by
 						       
	Ebit = Ebsend + Nfrd(s) * Erecv + Nidl(s) * Edisc / Psize
       
       where Psize represents the packet size

       It is clear form the equation that bit packet energy consumption
       will increase depending on number nodes receiving and discarding
       packets. Another significant consideration is to identify the 
       required forwarding nodes for reliable delivery of data to the sink.	

    B. Multi-hop Based Analysis
       Transmission of data from source to destination may require 
       multiple hops. Energy consumption of each hop can be obtained 
       from the single hop analysis and finally the total cost of data 
       transmission from source to sink will be an additive matrix of 
       each hop. 
       
       Based on analysis energy efficient routing protocol should have 
       the following properties
	    i. Balance energy consumption among the nodes to ensure uniform 
	       failure rate.
	    ii. Energy balanced path based on residual energy and distance 
	        towards sink
	    iii. Optimal number of forwarding node selection


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4. Protocol Description
    In this section we will describe sink rooted tree (SRT) construction 
  process and routing using the tree. Control message for tree 
  construction consists of following four fields 
      i. Node ID 
      ii. Residual Energy 
      iii. Distance up to sink 
      iv. Type of the message: Type 1 indicates forwarding node 
         selection message and type 0 means notification of 
         individual energy and distance information. 

   We define three different statuses of nodes depending on operation 
   
      i. Non-forwarding: Each sensor node is having a sensing circuit and
         a radio transceiver. In this status nodes will turn off their 
         radio transceiver and continue to sense for events within the 
         sensing rage. If any node senses any stimuli, will turn on their 
         radio and transmit to the nearest forwarding node.
      ii. Forwarding: Both the circuitry will  remain on for the nodes 
         in forwarding status. 
      iii. Active: While constructing the tree all nodes will remain in
         active status. There is node major difference between forwarding
         and active status. We need this status to differentiate from 
         normal operational state and tree construction state 

    Initially all nodes will be in status 0 (active status). Sink node 
  initiates tree construction with a type 0 message indicating s as 
  node ID, 0 as distance toward sink and  as the amount of residual 
  energy. Nodes within the 1-hop of sink will receive the message and 
  calculate parameter Tactive and Twait. Each node upo receiving 
  type 0 message will check whether the node has selected  forwarding 
  node. If the forwarding node is not selected the node will store the 
  node ID, residual energy and distance towards sink. Then sense the channel, 
  if the channel is idle it will wait for another Twait time and if 
  the channel is still idle it will transmit type 0 and type 1
  message consecutively noticing its residual energy and distance towards
  sink and its forwarding node. Each node will select forwarding node 
  based on the neighbor’s residual energy and distance towards sink. It
  should be noted that for each round of tree construction each node will
  transmit the messages once.  Any node receiving type 1 message will 
  check the incoming message node ID. If the node ID matches with own ID 
  the node will change its status to forwarding node. It means any of the
  neighbor need the node to relay the data towards sink. If any node does
  not receive type 1 message with matching with its own ID with in Tactive
  time, the node will change its status to non-forwarding node. After the 
  construction of the tree all nodes will be either in forwarding or 
  non-forwarding state. Nodes settled in non-forwarding state will turn 
  off their radio transceiver while keeping the sensing circuitry turned 
  on. On the other hand forwarding nodes will keep both radio and sensing
  circuitry turned on. All nodes will continue to sense within the 
  vicinity and if any stimuli detected for non-forwarding node, it will 
  turn its radio on and transmit data to the pre-defined sink while 


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  forwarding node having radio turned on will transmit to its forwarding 
  node. After tree construction each node will dynamically set 
  transmission range according to the distance of the parent or 
  forwarding node. Tree construction algorithm will be executed every 
  after T time where T is an application dependent parameter. T depends 
  on amount of events and event generation rate as well on the load of 
  the network. Each node participating in tree construction must have 
  threshold energy. It is obvious that nodes with higher ratio of 
  residual energy and distance will transmit first. Which ensures the 
  chance to choose the best forwarding node among the neighbors. A. Timer
  parameter for Tree construction and message Transmission All the nodes 
  will be in active status while constructing the tree. But the question 
  is how long the nodes will be in active status? Another important 
  consideration is transmission of control message for constructing the 
  tree. As the nodes participate in a competition to notify residual 
  energy and status to the neighbors, good scheduling among the neighbor 
  for control message transmission is needed to reduce collision. 
  Considering these two points we define two timer parameters for 
  determining each node’s active status time and control message 
  transmission time. 
  
  Determining Active Status Time: Let be a node and is the set of 1-hop 
  neighbor of for a particular transmission range r. We define   as 
  the round trip time for data propagation between any two
  pairs within the one hop neighbors. Active status time for node v is 
  given by the following equation 

 			Tactive = Trtt+N1(v)
  It should be noted that, within nodes will be able to determine its 
  necessity to be a forwarding node. If a node does not receive any 
  message from any of the neighbor to become as forwarding node within 
  time, the node will change its status to non-forwarding 
  
  Determining Control Message Transmission Time: 
  Tree construction algorithm will be initiated by sink and nodes within 
  in the transmission range will receive the message first. Waiting time 
  before further transmission can be obtained using the following 
  equation 

		Twait = Er / Ds

  Each node receiving the message will sense the channel and if the 
  channel is idle, it will wait until  time and then transmit own
  status and residual energy.   mainly depends on  and  which prioritize 
  the node with better energy and transmission cost towards sink. B . 
  

5. Conclusion

    Our proposed protocol high lightens wasteful energy consumption due
  to idle listening. We propose a hierarchical routing protocol which 
  creates a sink rooted tree with two different statuses (forwarding 


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  and non-forwarding) for each sensor node. Nodes in non-forwarding 
  status turn off their radio and conserves idle energy consumption and
  reduce redundant transmission. Simulation shows our algorithm is 
  better in terms of efficient energy consumption and network lifetime. 
  Sink mobility, very attractive feature for many applications of sensor 
  network is not included in our work. We intend to introduce sink 
  mobility in future. Significant amount of data aggregation is possible 
  at the forwarding nodes as same stimuli may be detected by more than 
  one node and transmitted to one forwarding node. In future we would 
  like to focus on data aggregation also

REFERENCES
[1] W. Heinzelman, A. Chandrakasan and H. Balakrishnan, "Energy- 
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[2] A. Manjeshwar and D. P. Agarwal, "TEEN: a routing protocol for 
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   Workshop on Parallel and Distributed Computing Issues in Wireless 
   Networks and Mobile Computing, April 2001.

[3] A. Manjeshwar and D. P. Agarwal, "APTEEN: A hybrid protocol for 
    efficient routing and comprehensive information retrieval in 
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[4] S. Lindsey, C. Raghavendra, PEGASIS: Power-Efficient Gathering in 
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[5] C. Intanagonwiwat, R. Govindan, and D. Estrin, "Directed diffusion: a 
   scalable and robust communication paradigm for sensor networks," 
   Proceedings of ACM MobiCom '00, Boston, MA, 2000, pp. 56-67.

[6] W. R. Heinzelman, et al., "Energy-Scalable algorithms and protocols 
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[7] R. Min, et al., "An Architecture for a power aware distributed 
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[8] A. Woo and D. Culler. "A Transmission Control Scheme for Media 
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[9] Azzedine Boukerche,Xiuzhen Cheng,Joseph Linus,"Energy-aware data
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[10] J. Hill, R. Szewczyk, A. Woo, S. Hollar, D. Culler, and K. Pister. 
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[11] W. Heinzelman, J. Kulik, and H. Balakrishnan, "Adaptive Protocols 
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[12] J. Kulik, W. R. Heinzelman, and H. Balakrishnan, "Negotiation-based
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[13] Y. Xu, J. Heidemann, D. Estrin, Geography-informed Energy 
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[14] Q. Li and J. Aslam and D. Rus, Hierarchical Power-aware Routing 
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AUTHOR'S ADDRESS


   Questions about this document can also be directed to the author:


   Md. Mamun-Or-Rashid     
      Department of Computer Engineering
      Kyung Hee University
      1 Seocheon, Giheung, Yongin, Gyeongi-Do, 449-701, Korea       
      Email: joon@networking.khu.ac.kr

   Choong Seon Hong
      Department of Computer Engineering
      Kyung Hee University
      1 Seocheon, Giheung, Yongin, Gyeongi-Do, 449-701, Korea 
      E-mail : cshong@khu.ac.kr
   Dongjin Kwak
      KT Advanced Technology Lab
      Woomyun, Secho, Seoul, Korea
      E-mail : djk@kt.co.kr
  

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