A Comparison of Clustered and Flat Architechtures for Tactical Adhoc Networks

Transcription

1 A Comparison of Clustered and Flat Architechtures for Tactical Adhoc Networks Mattias Sköld *, Yeongyoon Choi **, Jan Nilsson * *FOI (Swedish Defense Research Agency) **Korea Military Academy

2 Order of Presentation Introduction The Efficiency of Network Architecture Influence of Mobility Simulation and Results Conclusions

3 Introduction Purpose of Research Works The efficiency analysis of clustered architecture for small to medium sized ad hoc networks (up to 400 nodes)

4 Introduction Approaches Compare clustered architecture to non-clustered one from the routing point of view Simple reactive routing with flooding as route search As the measure of network efficiency, total amount of data bits to be transmitted for the delivery of data messages is used

5 Formation of Clusters Introduction ABCP(Access Based Clustering Protocol) Clusterheads elected by MAC procedure Rapidly deployed stable clusters for upper layer protocol Clients formed by ABCP are one single hop away from clusterheads CH

6 Two types of Clusters Introduction Type 1: Clusterhead is aware of nodes within the cluster and a route to neighboring clusters Type 2: Clusterhead is aware of nodes within the cluster and a route to neighboring clusters and also all links between nodes within the cluster CH

7 Efficiency of Network Architecture Route search procedure in different layer Flooding through every ordinary nodes for non-clustered network & selected clusterheads for clustered one For non-clustered architecture, the fastest route with the delivery of more route search messages For clustered architecture, less delivery of route search messages but longer delivery route for data messages The total amount of data bits required to be transmitted through a network should be compared for the analysis of network efficiency

8 A small example Source 1 3 Destination 2 4

9 A small example Clustered architecture Source 1 3 Destination 2 4

10 A small example Clustered architecture 1 Type Type 2 4 The source can now start transmitting data to the destination

11 Efficiency of Network Architecture Formula for the analysis of network efficiency C? B N? BL rms T T rms R C: Network load T rms : Time of Route search procedure T R : Life time of route found in the route search B rms : Number of bits in Route search message N: Number of transmissions of Route search message B R : Number of transmitted data bits on each link during T R. L: Number of hops of route found in the route search Brms? RT S, BR? RTR - T S : Time for transmission of RSM over a link.? R

12 Efficiency of Network Architecture Simplifying the formula We assume that T R is large compared to T rsm.? T? S C ; R? N? L?? TR? T S and B rms are fixed. We assume that N and 1/T R are independent.?? 1? 1? Ĉ???? A? Brms? E N E??? E L T T??? R? S?

13 Influence of mobility The time a route holds depends on node mobility. Instead of simulation of full scale mobile networks we model the time a route holds. We use the Gamma-2 (? 2 (?)) distribution as a simple model. 2?? t f T (t)?? te t? 0 L 2 2 E{T }? Var{T }??? L L 2 E[T L ]=20 E[T L ]= t

14 Influence of mobility We can now calculate the probability density function for the time a route holds. T R 2 L? 1? L? t f (t)?? tl1?? t e t? 0?? Based on this distribution we can calculate E{1/T R }????? 1 1 1? L L E??? f T (t)dt? L e? (L,L) R TR t 0???? t?? 1 (,x)? e t dt??? x

15 Real terrain DetVag-90 is applied for the connectivity check between any two pair of nodes (300MHz, 130dB) Simulated networks 50, 100, 200 and 400 nodes randomly distributed

16 DetVag-90 Data base with terrain heights and terrain types 2-dimensional model with knife-edges Calculates the basic path-loss between two nodes

17 Real terrain DetVag-90 is applied for the connectivity check between any two pair of nodes (300MHz, 130dB) Simulated networks 50, 100, 200 and 400 nodes randomly distributed Low connectivity A plan earth model is applied for the connectivity check between any two pair of nodes

18 Simulations We investigate when the networks load for the clustered architectures Type 1 and 2 are equal to the network load for the non-clustered architecture for different connection data rates and mobility. Connection data rate x Clusterd 0.5 architecture Non-clusterd architecture E[T L ] High <- Mobility -> Low

19 Simulation Results Real terrain networks

20 Simulation Results Low connectivity networks

21 Conclusions The main result is the analysis from which it can be determined if a clustered architecture is efficient given the mobility and connection data rate. Simulations with mobile nodes are not necessary Clustered architecture becomes better, when compared to a flat one, as the network size increases the connection data rate increases the mobility increases