Implementation of Backpressure Collection Protocol for Zigbee (IEEE 802.15.4) on Qualnet

1
Implementation of Backpressure Collection
Protocol for Zigbee (IEEE 802.15.4) on Qualnet

• By
• Pramit Choudhary, Balaji Raao Ravindra Bhanot
• CS 234 - Advanced Networks Graduate Course
• Instructor Prof. Nalini Venkatasubramanian
• (Initial draft of the presentation - 6/6/2012)

2
Problem Statement

• How to implement backpressure routing in
  practical wireless sensor networks considering
  concerns related to packet looping, link losses,
  end-to-end packet delays and scalability?

3
Motivations for defining the problem statement

• Real world sensing applications require high data
  rate with a capacity lt 4 KBps (Collection
  throughput)
• Most collection protocols in sensor networks are
  based on minimum-cost routing trees.
• Theoretical work on backpressure not implemented
  in practical systems.
• Need for superior delivery performance in noisy
  and extreme external interference environments.

4
How backpressure routing works?
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BCP Routing Packet Header
Type (1 bit) P (1 bit) C (1 bit) A (1 bit) Reserved (4 bits) Queue length (16 bits) Source ID Sequence No. (32 32 bits) Dest ID Sequence No. (32 32 bits) ETX (8 bits)
Type of Packet supported Currently, these are
the packet type supported by the implementation
of BCP on Qualnet namely, Beacon Packet, Data
Packet, ACK Packet P Pull (request for more
beacon packets from neighbors to be delivered to
obtain network topology update and estimation of
link metrics) C Congested bit ( P and C form
the control bits) A Acknowledgement bit (If
this bit is set high, then its an ACK
packet) Queue Length Information about the queue
backlog containing no. of data pkts Source and
Destination IP addresses Node IPv4
addresses Source and Destination sequence
numbers We use 32 bits as used in AODV protocol
in Qualnet ETX Expected number of transmission
for link calculation estimation NOTE The size
of the header is 20 bytes and is chosen based on
the implementation aspects in Qualnet. Bits for
each of the fields can be varied accordingly if
needed.
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Data Structures
typedef struct // Next 32-bit variable will
be used as // First 8-bits for type //
next bit is P-bit // next bit is C-bit //
next bit is A-bit // next bit is D1-bit
// next bit is D2-bit // next 11-bits are
reserved for the queue length // last 8-bits
for storing the ETX value. UInt32
typeBitInfo UInt32 floodingId
netLearningRreqPacketInfo // Part of the Beacon
Packet

• typedef struct
• netLearningRreqPacketInfo info
• // destination address and sequence
• netLearningAddrSeqInfo destination
• // source address and sequence
• netLearningAddrSeqInfo source
• netLearningREQUESTPacket

typedef struct NodeAddress address
UInt32 seqNum netLearningAddrSeqInfo
typedef struct NodeAddress address
UInt32 seqNum netLearningAddrSeqInfo
Beacon Packet contained in BCP
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Routing Table for BCP
Destination IP Address Link weights (w_(i -gt j)) ETX_(i -gt j) Link Rates R_(i-gt j)
Neighbor 1
Neighbor 2
Neighbor 3
Neighbor 4
Neighbor 5
The above table is maintained at every node in
the sensor network to update the one-hop
estimated metrics and calculation of the link
weights for all the links towards the connected
neighboring nodes.
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Message flow and module interactions
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LIFO Queue

• LIFO queue used in BCP for better efficiency in
  delivering data.
• LIFO queue implemented in Qualnet by Inheriting
  FIFO queue methods and properties.
• Initially Head and Tail point to the same
  location.
• The Head pointer increments as packets are
  added to a queue.

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LIFO in BCP

• Whenever LIFO becomes half full, a congestion
  bit set.
• A beacon message delivered back which indicates
  back pressure.
• Thus, efficient load balancing achieved across
  the network.

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BCP Algorithm

• Sink along with other intermediate nodes send
  out a beacon message (Beacon packet broadcasted)
• Each node except the Sink node is generating
  data packets to be sent across to the sink either
  directly or via intermediate node. Till a flow
  gradient is established, all generate packets are
  stacked in a LIFO queue maintained at each node.
• Each node is transmitting at different
  transmission rate based on gradient established.
• When an intermediate node receives a beacon
  from another node or the sink node, packet header
  is updated by setting the ACK (A flag) and
  returns the packet to the source (ACK packet
  sent).
• Before sending the ACK packet, the intermediate
  node updates its routing table with the source
  and destination IP addresses.
• On receiving the ACK packet, the source node
  estimates link rate (R) and expected number of
  transmissions (ETX) for all the links to its
  surrounding neighbors to get the back pressure
  weight. The back pressure weight, along with the
  ETX and R info helps in determining the flow
  gradient, hence the selection of the path.
• Assumption All nodes are considered to be static
  for the implementation of the protocol and its a
  single-hop broadcast to all the neighboring nodes.

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Phase1 - Contribution

• Played around with Qualnet to understand how to
  configure topologies, important to verify any
  kind of implementation - Balaji, Pramit, Ravi
• Good understanding of the Qualnet framework and
  how the different network layers interact with
  each other - Balaji, Pramit, Ravi
• Successful setting up of the system and the debug
  environment
• Successful addition of BCP as a new protocol to
  the existing Qualnet framework - Pramit
• Successful implementation of the generation of
  the beacon packets to search for the routes -
  Balaji, Pramit
• Successful implementation and addition of the
  LIFO queue to the Qualnet framework - Ravi
• Successful designing of the Packet header data
  structure for the BCP packet Balaji, Ravi
• Successful designing of the Routing table data
  structure for each node of the Routing protocol -
  Balaji
• As we speak, work is progressing on the
  implementation of the RREP message send by the
  receiver to the sender - Pramit, Balaji

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SnapShot of Routing Protocol in Qualnet
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SnapShot of Network Topology in Qualnet
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Phase 2 - Contribution

• Failure / Recovery Model If time permits
• Data Loss Resolved using if the ACK packet is
  not received within the Time to Live (TTL)
  defined for the data packet.
• Link failure The intermediate nodes are required
  to issue HELLO_I_AM_ALIVE message to the source.
  If the source does not receive this message
  within the time frame defined, then it will
  re-broadcast the beacon packet again.

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Evaluation

• For the final evaluation of the implementation,
  we plan to come up with measurements of the
  performance metrics and evaluating them. Metrics
  evaluations that we have thought of are
• Data Packet delivery Ratio
• Average Transmission/Packet
• Comparison of BCP with respect to LIFO and FIFO
  queues
• (This slide needs to be updated with results
  later)

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Related work

• Collection Tree Protocol (CTP) by O. Gnawali, R.
  Fonseca, K. Jamieson, D. Moss P. Levis
  implemented and tested on several testbeds like
  Tutornet, Motelab, etc and also on TinyOS 2.x.
• Collection Tree Protocol for the Castalia
  Wireless Sensor Networks Simulator by U.
  Colesanti and Silvia Santini.
• Backpressure Collection Protocol implementation
  on TinyOS 2.x by S. Moeller, A. Sridharan, B.
  Krishnamachari O. Gnawali This is the main
  paper that we have followed in the project.

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Conclusion

• Understanding of backpressure routing for
  collection protocols in sensor networks.
• Familiarizing and hands-on experience of using
  Qualnet network simulator.
• BCP routing algorithm design and development for
  a Zigbee (IEEE 802.15.4) protocol stack on
  Qualnet.