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AIC group: Networking Protocols and agent methodology research for Sensor Networks. Antonio G. Ruzzelli School of Informatics and Computer Science University College Dublin Dublin, Ireland [email protected] www.adaptiveinformation.ie. 1: Dual channel multiple access. Background. - PowerPoint PPT Presentation
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UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
AIC group:Networking Protocols and agent
methodology research for Sensor Networks
Antonio G. Ruzzelli
School of Informatics and Computer ScienceUniversity College Dublin
Dublin, [email protected]
www.adaptiveinformation.ie
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
1: Dual channel multiple access
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Background
• Traditional low cost radios for wireless sensors operate with one frequency channel at any given time, e.g Tr1001, CC1000, CC1010
• A profusion of MAC protocols focus on energy efficiency over one frequency channels
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Unique frequency channel issues• MACs like IEEE802.11, SMAC, TRAMA or BMAC suffer from:
– High latency (e.g. due to RTS/CTS/ACK in CSMA/CA)
– Low flexibility (Difficult to release slots unused in TDMA)
– Inefficient usage of the wireless channel(e.g. the ETP problem in CSMA/CA)
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Advances in WSNs• Novel transceivers can operate with two
channels simultaneously with a relative small increase of energy consumption e.g. nRF2401
Supply current one channel in receive 18 mASupply current two channels in receive 23 mA
• nRF2401 is effectively mounted on the motes developed at the University of Cork (Ireland)
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
DCMA/AP: Dual channel multiple access with adaptive preamble
• Usage of 2 frequency channels– Data channel Cd for data – Control channel Cc for notifications
Pros• No table of neighbours required • No handshake mechanisms like RTS/CTS• Reduced idle listening at the receiver• Adaptive wake-up node preamble
Cons• Small increase of current consumption in dual channel reception
mode (18ma23mA)
• Suitable for:– Nodes working at very low duty cycle– Dual channel transceiver
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
The minimum wakeup concept LCCA• Nodes alternate long period of inactivity to tiny period of
channel assessment;• The Least Clear Channel Assessment LCCA is the shortest
time period needed for nodes to sense any activity on the channel (~2.5msec in BMAC)
• LCCA time period is much shorter than the time required for a packet transmission (e.g. 35msec for 5byte transmission with Tr1001)
• LCCA can reduce node duty cycle to less than 1%
• Wakeup period : longest period of consecutive node activity when a signal is detected (Sensing time)
Wakeup period Ts Sleep periodLCCA
Time
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
DCMA communication mechanism (1)
• Node are unsynchronized asynchronous transmission
• All nodes apply LCCA periodically on the data channel Cd only
• A node with data to transmit apply LCCA on control channel Cc firstly.
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
The transmitter• If the channel is
clear then the transmitter starts sending the adaptive preamble Pa
on Cd
• At the same time TX keeps on listening to Cc
DCMA communication mechanism (2)
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
DCMA communication mechanism (3)The receiver• During regular
CCA, the receiver can sense channel activity on Cd then reply with a TIP packet on Cc
TIP =transmission / reception in progress
• TIP contains (1)the receiver ID, (2) next Rx ID, (3) packet length
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
• In case of error, the notification is transmitted on Cc
• The error packet contain the PackID
• In case of error the packet is rescheduled
DCMA communication mechanism (4)
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
The exposed terminal problem removal
• TIP is sent by the receiver only nodes around the receiver refrain from transmitting
The communication mechanism removes the ETP!
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Adaptive Preamble mechanism• In case of multiple
transmission, asynchronous packets help the receiver to obtain the node ID of the later transmitter Tx2.
• Consequently Tx2 can be enabled by means of a RIP packet
• The Preamble transmission stops as soon as the RIP packet is received adaptive!
Transm. adaptive Preamble
Transmitter1
Cd
Receiver
Cd
Cc
Cc
CCA
Tx D A T A
Transmitter2
Cd
Cc
Tc
Transm. Adapt. Pr.
CCA
CCA
L i s t e n
L i s t e n
L i s t e n
Tx RIP
Tp
Note: RIP content = TIP contentDifference: RIP is used to identify multiple Tx
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Opportunistic Crossover mechanism• During periodical LCCA, if activity
is sensed, nodes switches to Cc to get the TIP/RIP packet
• TIP/RIP packet contains info about the next scheduled RX node (nextRx) and ongoing packet length
• The nextRx is in the position to set up a NAV alarm to wake up right after the packet is transmitted.
• Other nodes set up a double NAV to wake up just before the packet has been forwarded
TX RX Next RX
Channel Cd Channel Cc
Note: Opportunistic crossover needs the next receiver to sense the channel busy (not only the case)
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Implementation• DCMA/AP
has been coded within the OmNet++ based on the object oriented C++.
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Preliminary results• Decrease of transmission packet delay
• Increase of network flexibility in terms of access to the channel and node scalability.
• Some increase of partial overlapping transmissions on the control channel Cc following an increase of packet generation rate
• In general, initial results follow our expectation that an improved performance could compensate for the increase of energy consumption due to two channel utilization
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
The MERLIN architecture:
The TDMA/CSMA hybrid approach, the MERLIN protocol as an example
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Scheduling tables: V-schedule vs. X- Schedule
gate
Zone 1
Zone 6
Zone 2
Zone 3
Zone 4
Zone 5
Zone 7
Zone 8
Zone 9
Time
Spa
ce
gate
Zone 1
Zone 6
Zone 2
Zone 3
Zone 4
Zone 5
Zone 7
Zone 8
Zone 9
SlotF R A M E
CSMA / Transmit / Listen
Receive
Idle
•Frame is divided in 8 slots;
•Nodes in the same zone transmit simultaneously
•The X scheduling is obtained by super positioning 2 V-sched one of which upside-down
•Nodes go into sleep immediately after the transmission
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
0
1
2
3
4
5
6
7
1 2 3 4 5 6 7 8 9
Hop count number
Ave
rage
late
ncy
X-scheduling V-scheduling
Average end-to-end packet delay
X-scheduling vs V-scheduling
0
50
100
150
200
250
300
0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2Frametime (sec)
Network Lifetime (days)
X Scheduling
V-Scheduling
1 Gateway 100 Nodes rand. Distributed.800*500 area network Min signal strength(12 m)50 msg/min sent by 5 rand. nodes Static networkDelay calculated in the worst case scenario: 2 sec frametime
Operational network lifetime
The X scheduling used for applications in which some energy can be traded off for a decrease of latency of messages and for applications in which latency is a tighter constraint;
V-scheduling used for low data traffic applications where the need for saving energy is of paramount importance.
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
What about an augmented intelligence of decision
making?…A multi agent systems to:• Planning to take long term decisions (not only if the-else based) • Migrate to an area affected by an anomalous event• To improve the adaptivity of the networks • Decision based on information from different layers• Better cope with dynamic changes of the network conditions.• To take local decision between neighbouring nodes rather than
at the gateway. Hence:– Energy saving– More accurate and faster response to network changes– Increase of preciseness of the action taken
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Multi agent system
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Possible solution:
Multiple Notification messages
High energy consuming
Application: Dynamic scheduling change due to localized anomaly
Our proposed solution:
Migrating agent
Moderate energy consuming
An example:
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Disadvantages
• Accommodate BDI agents is very challenging due to devices computationally limited
• Debugging agent systems during ongoing applications is very challenging (sensors have only 3 leds provided)
• Traditionally Multi agent systems (MAS) are java oriented -> JVM needed
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Debugging:Agents-nodes mapping at the BS• One-to-One
– Each node is controlled by one agent that deliberates accordingly
– Nodes can be seen as agent perceptors• Many-to-One
– Many agents map to an individual node– E.g. useful when nodes have several sensory modalities
• One-to-Many– A single agent map to a group of neighbouring nodes– E.g. useful when decision may be taken by analysing a
group of nodes locally placed
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Methodology phase 1: Centralised Base station implementation
•A single agent placed at the BS
•The agent receives raw data from nodes then analyse them
•The agent identifies and solve anomalous behaviour of the network or part of it.
•The agent communicate to the BS what action to take.
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Methodology phase 2: Distributed Base station implementation
•The second phase transforms the centralised solution in a distributed agent-base implementation
•The key point of this phase is to have a mapping between agents of a MAS and sensor nodes
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Methodology phase 3: Distributed agents implementation•Agents on the nodes can be modelled through the agents at the BS
•Hence, agents on the nodes can be easily debugged at the BS
•The distributed implementation can be achieved by mapping the statements that govern the agents behaviour (such as commitment rules) to the language of the device .
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Power managementthrough network coverage:
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Integrated Sensor and Routing Coverage Agents
Definitions:
•Sensing Coverage: If any node within the sensed area is covered by at least 1 sensor
•Redundant node: It can be switched off without affecting the level of coverage provided by the network;
•Routing Coverage: It exists at least one communication path from any node within the network to the gateway
gateway
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Opportunistic Power Management
•Disconnecting sensors based on solely sensing coverage may lead to a disconnected network; for example:
•Interpolation for sensing Coverage can be used when nodes does not have a well defined sensing radius e.g sensing temperature
•A Time-Zones network division for Routing coverage can be used when nodes does not have a well defined transmitting radius e.g channel irregularities
Redundant based on routing and sensing coverage
•Hibernating redundant sensors, must be decided based on both routing and sensing connectivity!u
Zone n+1
Zone n-1
Zonen
Redundant based on sensor coverage
Gateway
Disconnected
Transmission radius
Integrated Sensor and Routing Coverage Agents
UNIVERSITY COLLEGE DUBLIN DUBLIN CITY UNIVERSITYSMI || NCSR || CDVP
Ruzzelli, O’Hare, Jurdak, Tynan
Questions and comments are welcome
Thank you for your kind attention!