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Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. Mode Selection Criteria in MANETs using Heterogeneous Antenna.

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Presentation on theme: "Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. Mode Selection Criteria in MANETs using Heterogeneous Antenna."— Presentation transcript:

1 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. Mode Selection Criteria in MANETs using Heterogeneous Antenna Technologies Vivek Jain, Nagesh Nandiraju, Dharma P. Agrawal University of Cincinnati

2 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 2 Outline Introduction Mobile Ad hoc Networks (MANETS) Antennas Multiple Access Protocols Mode Selection Criteria Motivations Assumptions Node Model Antenna Pattern Simulation Parameters Performance Evaluation Applicability of Mode Selection Criteria to Multiple Beam Antennas Conclusions Future Work

3 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 3 Mobile Ad Hoc Networks (MANETs) Peer-to-peer connectivity Lack of fixed infrastructure relays Absence of centralized authority Multi-hop forwarding to ensure network connectivity Applications Military.. Combat Systems, reconnaissance Rescue, medical emergency, telemedicine

4 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 4 Antenna Types Omni-directional antenna Transmits power equally in all directions Directional antenna Concentrates power in a directed zone Smart Antenna Has the in-built intelligence to change direction according to requirement (steer the beam) Multiple-Beam Smart Antenna Simultaneous transmission/reception in more than one directions Multiple Input Multiple Output (MIMO) Multiple streams of data in same channel.

5 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 5 Smart Antenna System

6 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 6 Antennas and MANETs Omni-directional communication suffers from poor spatial reuse Directional communication leads to better spatial reuse, reduces co-channel interference and provides range extension

7 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 7 Multiple Access Protocols MAC Proposals differ based on How RTS/CTS transmitted (omni, directional) Transmission range of directional antennas Channel access schemes Omni or directional NAVs Antenna Model Two Operation modes Omni & Directional Omni Mode: Omni Gain = Go Idle node stays in Omni mode Directional Mode: Capable of beamforming in specified direction Directional Gain = Gd (Gd > Go) --> Range Extension Directional Gain = Gd (Gd = Go) --> Spatial Reuse Range Extension Spatial Reuse

8 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 8 Directional vs. Omni-directional The Problem of utilizing directional antennas to improve the performance of ad hoc networks is non-trivial Pros Higher gain (Reduced interference) Spatial Reuse Cons Potential possibility to interfere with communications taking place far away Hidden Terminal Deafness

9 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 9 Motivations Which mode? Omni-directional or directional Analyze various topologies involving neighboring transmissions or receptions Formulate mode selecting criteria for medium access control (MAC) for MANETs with heterogeneous technologies

10 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 10 Assumptions Two modes of operation: omni and directional Directional transmission of RTS/CTS/DATA/ACK in directional mode Transmission range of directional antennas is same as that of omni-directional ==> Spatial Reuse 4-Way CSMA for medium access control The channel is symmetric

11 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 11 Node Model The node model of advance MANET available in OPNET is modified to facilitate directional mode of communication In directional mode, the antenna (tx_rx_ant) points in the desired direction with the help of antenna pointing processor (tx_rx_point)

12 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 12 Antenna Pattern Conical directional antenna pattern of main lobe having beam-width of 45 degrees and a gain of 0 dBi. The gain in remaining spherical side-lobe is confined to -20dBi

13 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 13 Simulation Parameters ParameterValue Data rate2 Mbps Data packet size1500 bytes Packets Inter-arrival timeConstant (0.005 seconds) Directional gain0 dBi (main lobe) -20 dBi (side lobes) Transmit Power0.5 mW Packet reception-Power Threshold-95 dBm Buffer size32 Kbytes (~21 Packets) Simulation Time100 seconds Packets generated = 200 packets/sec/transmitter Maximum achievable throughput ~ 130 packets/sec/receiver (non-overlapping communication) ~ 65 packets/sec/receiver (two overlapping transmissions)

14 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 14 Performance Evaluation – Deaf Deaf communicating pair scenario Receivers in same beam of the transmitter Transmitters in same beam of the receiver Both the transmitters are deaf to each other communication Omni-directional mode performs better

15 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 15 Performance Evaluation – Deaf Degradation of throughput (~15%) in directional mode of communication as compared to omni-directional mode

16 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 16 Performance Evaluation – Deaf Retransmission attempts are higher (~12 times) in directional communication due increased collisions at the receiver. However, average delay is nearly same in both cases

17 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 17 Performance Evaluation – Common Receiver Common receiver scenario Two or more transmitters with common receiver Usually both the transmitters are deaf to each other communication Omni-directional mode performs better

18 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 18 Performance Evaluation – Common Receiver Degradation of throughput (~15%) in directional mode of communication as compared to omni-directional mode

19 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 19 Performance Evaluation – Common Receiver Retransmission attempts are higher (~12 times) in directional communication due increased collisions at the receiver.

20 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 20 Performance Evaluation – Linear_Pair_SameBeam Another communicating pair in the same beam of the transmitter Throughput of C-D pair suffers due to interference from A-B ongoing communication in directional mode For optimal performance C switches to omni mode while other remains in directional mode

21 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 21 Performance Evaluation – Linear_Pair_SameBeam Switching C to omni-directional mode while remaining nodes in directional mode gives optimal throughput

22 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 22 Performance Evaluation – Linear_Pair_SameBeam Delay is less in directional mode as all newly generated packets are transmitted while packets in queue are dropped after maximum retransmission attempts

23 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 23 Performance Evaluation – Linear_Pair_SameBeam Retransmission attempts by node C are much higher in directional mode owing to higher BER (i.e. collisions) at node D

24 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 24 Performance Evaluation – Tx_0 Another node transmitting in same direction Again switching the mode of intermediate transmitting node to omni- directional mode while remaining with directional mode yields optimal performance

25 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 25 Performance Evaluation – Tx_0 Average throughput in directional mode is about 15% lower than in omni-directional mode

26 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 26 Performance Evaluation – Tx_0 BER is much higher in directional mode due to interference from transmitters as they are deaf to each other

27 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 27 Performance Evaluation – Tx_90 and Rx_90 Another non-interfering transmitter or receiver in the communicating beams Omni-mode restricts simultaneous transmissions, hence directional mode is recommended Tx_90Rx_90

28 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 28 Performance Evaluation – Tx_90 and Rx_90 Directional communication achieves maximum possible throughput in all cases owing to better spatial reuse

29 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 29 Performance Evaluation – Tx_90 and Rx_90 Delay is more in omni-directional communication due to increased media access delay at the transmitters

30 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 30 Performance Evaluation – Tx_90 and Rx_90 Due to increased channel contention at the transmitters packet retransmission attempts are more in omni-directional mode

31 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 31 Performance Evaluation – Linear, Parallel and X topologies Only the intended receiver or transmitter in the communicating beams Both the transmitters are deaf to each other communication No other communicating node in those beams Directional mode outperforms omni-directional mode of communication Linear Parallel X

32 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 32 Performance Evaluation – Linear, Parallel and X topologies Traffic Received (packets/sec) vs. time

33 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 33 Mode Selection Criteria All nodes in omni-directional mode in the following cases: Deaf communicating pair scenario Receivers in same beam of the transmitter Transmitters in same beam of the receiver Both the transmitters are deaf to each other communication Common receiver scenario Two or more transmitters with common receiver Intermediate transmitting node in omni-directional mode while other nodes in directional mode for the following cases: Another communicating pair in the same beam of the transmitter Another node transmitting in same direction All nodes in directional mode, in the remaining cases including: Another non-interfering transmitter or receiver in the communicating beams Only the intended receiver or transmitter in the communicating beams

34 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 34 Applicability of Mode Selection Criteria to Multiple Beam Antennas Multiple beam antennas Can either transmit or receive multiple packets simultaneously. This requires: Packet receptions in different beams at the node to commence at the same time Packet transmissions by a node in multiple beams to begin simultaneously A node cannot both send and receive data at the same time Can simulate omni-directional mode by transmitting in all possible beams simultaneously Can multiple beam antennas achieve optimal performance by transmitting control packets in beams having transmitters and receivers only ???

35 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 35 Conclusions Directional mode Better spatial reuse Enhances system capacity Deafness and hidden terminal problems However there are some cases where omni-directional mode performs better Deaf communicating pair scenario Interference from side-lobes cannot be ruled out Common receiver scenario Mode Selection Criteria forms the basis of developing MAC protocols for MANETs using heterogeneous antenna technologies Dynamically switching a node from directional to omni-directional or vice versa depending on the neighboring nodes

36 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 36 Future Work Work needs to be extended for multi-hop topologies Extensive study needs to be done with more communicating pairs within the vicinity so that performance varies with the node density Game Theoretic approach for mode selection criteria in such scenarios Performance of multiple beam antennas transmitting control packets in beams having transmitters and receivers only, need to be evaluated

37 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 37

38 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 38 IEEE 802.11 IEEE 802.11 DCF – RTS/CTS access scheme Physical Carrier Sense Physical Carrier Sensing Virtual Carrier Sensing

39 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 39 Antenna System Phased Array Antenna

40 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 40 Direction of Arrival Estimation

41 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 41 Beam Formation Beam Forming Technique in which the gain pattern of an adaptive array is steered to a desired direction through either beam steering or null steering signal processing algorithms Adaptive beam forming algorithms can provide substantial gains (of the order of 10log(M) dB, where M is number of array elements) as compared to omni directional antenna system Antenna Pattern of 7-element uniform equally spaced circular array.

42 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 42 Smart Antenna System Switched Beam Consists of a set of predefined beams. Allows selection of signal from desired user. Beams have narrow main lobe and small side-lobes. Signals received from side-lobes can be significantly attenuated. Uses a linear RF network, called a Fixed Beam-forming Network (FBN) that combines M antenna elements to form up to M directional beams.

43 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 43 General Smart Antenna Architecture Source: Chris Loadman, Zhizhang Chen and Dylan Jorgensen, An Overview of Adaptive Antenna Technologies For Wireless Communications, In Proc. o Communication Networks and Services Research Conference (CNSR), pp 15-19, 2003.

44 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 44 Features and Benefits of Smart Antenna Systems Source: http://hosteddocs.ittoolbox.com/MI102204.pdf

45 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 45 The global market for smart antennas growth Source: US analyst firm Visant Strategies

46 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 46 A terminal with 16 antennas mounted on a laptop Source: Alexiou, A.and Haardt, M., Smart antenna technologies for future wireless systems: trends and challenges, IEEE Communications Magazine, Vol. 42, pp. 90-07, Sept. 2004

47 Copyright © 2005 OPNET Technologies, Inc. Confidential, not for distribution to third parties. 47 MIMO PC Card Source: http://www.airgonetworks.com/pdf/Farpoint Group 2003-242.1 MIMO Comes of Age.pdf


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