HEINZ NIXDORF INSTITUT Universität Paderborn Schaltungstechnik Prof. Dr.-Ing. Ulrich Rückert Robot Communication over Wireless Ad Hoc Network M.Sc. Feng.

HEINZ NIXDORF INSTITUTUniversität Paderborn

SchaltungstechnikProf. Dr.-Ing. Ulrich Rückert

Robot Communication over Wireless Ad Hoc NetworkRobot Communication over Wireless Ad Hoc Network

M.Sc. Feng Xu

03.02.2005

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Agenda

• Why communication among robots is necessary• 3 examples• Two categories network: centralized network and ad hoc network• Properties of ad hoc network, and examples• Current Main Stream Techniques• Hardware structure for the communication node• Constrains for portable devices: energy, space, computing ability• MAC protocol, CSMA/CA• Current two hot research directions on MAC layer• Directional communication• Dynamic multi-channel allocation• 3 means to close the gap between theory and realization• Summary

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Why communication among Robots

• Goal of RoBoCup: To fully develop autonomous humanoids that can win against human world champion soccer team by 2050 Each robot player should have more powerful individual ability over human

player Communication among robots is necessary for the high level coordination

(deliberation-based high level behavior control!)

• In special robot application scenarios like war field and emergency field, communication among robots can significantly enhance their ability

• Contrariwise, robots with wireless communication module can help simulate or experiment the wireless network

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Example 1, AIBO

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Example 2, BiM-2

Receiver on a PCB

Receiver unit on a robot

Seattle University RoboCup Team, USA

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Example 3, Khepera

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Two Categories of Network

Centralized Network

Mobile Ad Hoc Network (MANET)

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Properties of Ad Hoc Network, examples

• MANET is a decentralized wireless network without pre-built infrastructure• Each node acts as host and router simultaneously, and signals may be

transmitted via multi hop to the destination• The network topology may change rapidly and unpredictably due to

movements, joining and leaving of nodes at any moment

• MANET may operate in a standalone fashion, or may be connected to other existent network as its extension

Properties:

Examples:• Conferencing and home networking• Wireless sensor network• Multi-hop extensions for cellular telecommunication systems• And networks of vehicles, robots

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Current Main Stream Techniques

• Bluetooth• WLAN: IEEE 802.11 b,g,a• HiperLAN/II• ZIgBee• WiMax (near future)

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Hardware Structure, different network layers

RF transceiver Baseband Processor

physical

MAC controller

MAC

Host

other high layers

OSI/ISO Reference Model

Hardware structure for each node

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Constrains for Portable Devices

• Physical space• Limited energy (battery powered devices)• Limited computing power

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CSMA/CA

• MAC protocol: carrier sense multiple access with collision avoidance• Prerequisites: Omnidirectional communication on single frequency channel

A B

C

D

E

F

RTS, CTS, data and NAV setting

Basic media access process

Resulted space allocation condition

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Current hot research topics

Goals:• Increase resource efficiency, the resource

mainly means frequency band• Make the communication link more robust

Means:• Directional communication to increase the

space reuse factor• Multi-channel dynamic allocation scheme

A B

C

D

E

F

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Smart Antenna, directional antenna

Smart Antenna•Realized by antenna array and additional array signal processing unit•Enable various advantages on network, but also consume much additional resource like space, energy and computing power

Directional Antenna•The directivity is attributed to the directional property of the antenna element itself•With the mechanical turning assistance, or multiple directional antennas equipped on each node with proper orientation, each node can communicate on the direction it wishes•Less additional resource is needed comparing to SM, however, less improvement is anticipated

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Multi-channel scheme: CDMA, OFDM

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Theoretical Research, Practical application, 3 means close the gap

Theoretical research:•New schemes are firstly put forward on the physical layer•Higher layers (MAC, network layers) need adapting to the modifications•Cross-layer optimization

Close the gap between theoretical research and practical application•In practice, many constrains are imposed•Rely on the chip layer improvement•Use the simplified scheme to make it more practical•The combination of aforementioned 2 means

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Summary

• To reach the goal of RoBoCup, the communication ability among robots is necessary

• To communicate efficiently and effectively, a network called mobile ad hoc network is meaningful for the robot team

• Contrariwise, robot team with communication ability can help contribute to the network system improvement

• Many constrains are imposed on the portable devices due to its limited resource

• Numerous new schemes are put through on the physical layer to increase transmission data rate and communication link robustness

• Cross-layer optimization is important for the whole system performance• 3 means to close the gap between theoretical research and practical

application



Heinz Nixdorf InstitutUniversität PaderbornSchaltungstechnikProf. Dr.-Ing. Ulrich RückertFürstenallee 1133102 Paderborn

Feng XuTel.: 0 52 51/60 6396Fax.: 0 52 51/60 6351Email: [email protected]://wwwhni.upb.de/sct

Thank you for your attention!Thank you for your attention!

HEINZ NIXDORF INSTITUT Universität Paderborn Schaltungstechnik Prof. Dr.-Ing. Ulrich Rückert Robot Communication over Wireless Ad Hoc Network M.Sc. Feng.

Documents

wireless network slide

network manet slide

ulrich rckert properties

ulrich rckert example

node slide

ulrich rckert agenda

network properties of

ulrich rckert smart