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Efficient Geographic Routing in Multihop Wireless Networks

Efficient Geographic Routing in Multihop Wireless Networks. Seungjoon Lee, Bobby Bhattacharjee, Suman Banerjee MobiHoc, 2005 Jerry. Contents. Introduction Overview of NADV NADV New link metric for geographic routing Link cost types and estimation Simulation and results Conclusion.

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Efficient Geographic Routing in Multihop Wireless Networks

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  1. Efficient Geographic Routing in Multihop Wireless Networks Seungjoon Lee, Bobby Bhattacharjee, Suman Banerjee MobiHoc, 2005 Jerry

  2. Contents • Introduction • Overview of NADV • NADV • New link metric for geographic routing • Link cost types and estimation • Simulation and results • Conclusion Efficient geographic routing in multihop wireless networks

  3. Introduction • Geographic routing • Location information for packet delivery • Next hop node selection based on neighborhood and destination information • No route establishment • Popular strategy for geographic routing • To the neighbor geographically closest to the destination • Route around ‘voids’ problem • No neighbor closer to the destination than the current node d v w x y z Efficient geographic routing in multihop wireless networks

  4. Overview of NADV • NADV (normalized advance) • New link metric for geographic routing • Optimal trade-off between ‘proximity’ and ‘link cost’ • Adaptive routing • General scheme for efficient routing • Support a variety of different cost types • Different routing strategies depending on system objectives, message priority or applications Efficient geographic routing in multihop wireless networks

  5. New link metric for geographic routing(1/3) • ADV (advance) : background • Current node S greedily select the neighbor closest to destination T • Minimization the hop count between source and destination • Advance (ADV) of n • Amount of decrease in distance by a neighbor n • Demerit • No consideration of link cost • Use of poor quality links, unnecessarily high communication cost D(x) : distance from node x to T Large advance Good link quality vs Efficient geographic routing in multihop wireless networks

  6. New link metric for geographic routing(2/3) • NADV (normalized advance) • Normalized advance of neighbor n -> Expected advance per transmission Psucc(n) probability of success in transmitting data to n Efficient geographic routing in multihop wireless networks

  7. New link metric for geographic routing(3/3) • Optimality of NADV in an idealized environment • Link costs along the found path by NADV is minimum • Assumptions • We can find a node at an arbitrary point • Link cost is an unknown increasing convex function of distance • Process • DIST : distance from source S and destination T (relatively large) • Optimal path : straight line between S and T • Sum of link costs : minimized when all links have the same distance • Optimal interval T S Efficient geographic routing in multihop wireless networks

  8. Link cost types and estimation (1/7) • Wireless integration sublayer extension (WISE) • Three types of link cost • Packet error rate • Link delay • Energy consumption • For efficient link cost estimation • Additional control messages available -> WISE extract relevant link cost info. • Otherwise -> WISE exploits MAC-specific info. Efficient geographic routing in multihop wireless networks

  9. Link cost types and estimation (2/7) • Packet error rate (PER) • Four PER estimation methods for • Using probe messages • Using signal-to-noise ratio • Neighborhood monitoring • Self monitoring Efficient geographic routing in multihop wireless networks

  10. Link cost types and estimation (3/7) • PER estimation 1: Using probe messages • Link error probability • Probe message • Reception ratio from periodic message exchange • Adjusting PER depending on the data packet length • l-bit probe messages • Infer bit error rate from observed PER(l) • L-bit data frame [ Observed and estimated PERs for five experiments with varying distance ] Efficient geographic routing in multihop wireless networks

  11. Link cost types and estimation (4/7) • PER estimation 2: Using signal-to noise ratio (SNR) • Bit error rate – Assuming white gaussian noise and BPSK modulation • PER estimation 3: Neighborhood monitoring • Passive monitoring to infer link PERs • Node A monitor frames sent by neighbors • Using the MAC sequence number, A count frames missed from neighbor B • A infer PER of link from B to A • A needs to inform B of the PER estimation Efficient geographic routing in multihop wireless networks

  12. Link cost types and estimation (5/7) • PER estimation 4: Self monitoring • Condition • Additional control messages : not possible • Modification of beacon message format : not possible • Technique • Node transmits a data frame to neighbor n • Mac-layer informs the WISE whether transmission was successful or not F=1 (fail), F=0 (success) • PER of wireless link to neighbor n Efficient geographic routing in multihop wireless networks

  13. Link cost types and estimation (6/7) • Delay • Two types of link delay • Medium time • Time spent in sending a packet over the link • WISE can easily retrieve the current value of transmission rate from the MAC layer and calculate the necessary medium time to the neighbor • Total delay • Time from the packet insertion into the interface queue until the notification of successful transmission • Queuing delay, backoff time out, contention period, retransmissions due to errors or collisions Efficient geographic routing in multihop wireless networks

  14. Link cost types and estimation (7/7) • Power consumption • Assumptions • Control mechanism for transmission power adjustment to save battery • Appropriate transmission power level Ptx • WISE retrieve Ptx and calculate actual system power consumption Cpower Efficient geographic routing in multihop wireless networks

  15. Simulation model (1/2) • Environment • Ns-2 simulation • Node placement • Uniformly at random on a 1000m by 1000m square • Static source at (50, 500), destination at (50+D, 500) • Geographic routing : simulation code for GPSR • 802.11 auto rate fallback ARF (1M, 2M, 5.5M, 11Mbps) • IEEE 802.11b standard for the underlying MAC layer protocol • Error model • Random packet error model • Performance of NADV in the presence of randomness in packet errors • Error models obey SNR equations • Rivals: Blacklisting • Fixed threshold • Node excludes neighbors with low-quality link based on the threshold Efficient geographic routing in multihop wireless networks

  16. d : distance, n: path loss exponent (2 - 6) Smin: minimum required signal strength at receiver In simulation n=4, Simulation model (2/2) • Power consumption model • Transmission power for successful reception at a receiver • Transmission power • Energy each packet forwarding consumes • C is hardware specific variable Efficient geographic routing in multihop wireless networks

  17. Simulation results (1/5) • Experiments with perfect estimation of link errors • NADV vs ADV • Data transmission overhead of ADV increases abruptly • NADV vs blacklisting • Blacklisting : different threshold values lead to best results • NADV : adapt to the changing network • Number of retransmission • Network bandwidth, resources • Packet delay • GPSR retransmit option on • 802.11 ARF off Efficient geographic routing in multihop wireless networks

  18. Simulation results (2/5) • Experiments using proposed PER estimation techniques • Changing noise power • Use SNR induced error distribution • Start with high noise • After 300 sec, low noise • After 700 sec, medium noise • ( ) : Packet delivery ratio • GPSR retransmission off • 802.11 ARF off Efficient geographic routing in multihop wireless networks

  19. Simulation results (3/5) • Simulation under mobile environments • 100 nodes, source and sink are fixed nodes, others are mobile • Moving rate 1m/s – 10m/s, pause time ranges from 1000s – 0s Efficient geographic routing in multihop wireless networks

  20. Simulation results (4/5) • Using power consumption as link cost [ Average power consumption with different schemes ] Efficient geographic routing in multihop wireless networks

  21. Simulation results (5/5) • Experiments with generic cost • Link cost • Experiment scenario • Source and destination are 900meters apart • Source starts to send data packets after 10 seconds • At 30 seconds, environment of some part of the network changes • We randomly select 50% of links and increase their link costs by 50% r : uniformly distributed random number d : distance between two nodes R : maximum transmission range [ Average path quality of each scheme before and after the link cost change ] Efficient geographic routing in multihop wireless networks

  22. Conclusion • NADV • New link metric for geographic routing in multihop wireless networks • Adaptive, general and useful for various link cost types • Combination of NADV and cost estimation techniques outperforms the current geographic routing schemes • NADV finds paths whose cost is close to the optimum Efficient geographic routing in multihop wireless networks

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