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Cluster Head Architecture for Seamless Reconfiguration of BSNs

Cluster Head Architecture for Seamless Reconfiguration of BSNs. Ayan and Sidharth. Cluster Heads (CHs) in Wireless Sensor Networks (WSNs). WSNs have a large number of sensors spread over a wide area, collecting data and transferring it to a central, base station.

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Cluster Head Architecture for Seamless Reconfiguration of BSNs

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  1. Cluster Head Architecture for Seamless Reconfiguration of BSNs Ayan and Sidharth

  2. Cluster Heads (CHs) in Wireless Sensor Networks (WSNs) • WSNs have a large number of sensors spread over a wide area, collecting data and transferring it to a central, base station. • Generally, base station is far away from most sensors. • Hence, sensors form clusters and elect a Cluster Head (CH). All the sensors in a cluster communicate with the CH, and it relays this data to the base station.

  3. Base Station Sensors

  4. Cluster Head Architecture • Advantages: • Most sensors spend lesser power since they communicate with the nearby cluster head, rather than the far away base station. • Medium Access is simpler since all sensors are not contending for channel to base station. • Disadvantages: • Cluster Head spends much more power, and hence runs out of battery sooner -> Solved by rotation of Cluster Head role. • Cluster Head needs enough memory to aggregate packets from all sensors -> Use data-packing algorithm

  5. Body Sensor Networks – Current Architecture • N wearable/implantable sensors on a person’s body. Unlike WSNs, sensors are heterogeneous. • Base station is generally in the form of a mobile phone/PDA. • Base station assumed to be resource-rich while the sensors are constrained in terms of energy and computational power.

  6. Body Sensor Networks – Functions • Collect medical measurement data. (Sensors) • Aggregate data from all sensors. (Base Station) • Collect data from other contextual sensors (GPS,etc.) (Base Station) • Support high-level applications, queries and actuation. (Base Station) • Issue real-time remote alerts/requests (e.g. Contacting physician when patient faints) (Base Station)

  7. Need for new architecture • Cell-phone/PDA style device is not always carried on the body. (e.g. sleeping, eating, playing sports) • If distance of base station from a sensor is greater than the MIN radio power range, the sensor will have to expend greater energy to communicate directly with the base station. • MehulMotani, et al. have shown that a star topology doesn’t give good PDR in outdoor environment at low sensor radio power. • ?? (more ideas/motivation)

  8. Cluster Head Architecture for BSNs • A subset of M nodes, out of the N sensor nodes is defined as a Council, and the cluster head role is rotated among these. • All sensors communicate with the cluster head and only the cluster head communicates with the Base Station. • Typically, wearable devices with larger memory and battery are part of the Council.

  9. Re-configurable BSNs BSN Use Cases Outdoor Indoor, with phone Indoor without phone C.H. -> Phone B.S. -> Phone C.H. -> Sensor B.S. -> Phone C.H. -> Sensor B.S. -> ?? If phone is out of range, the Base Station can be chosen as a “Friend Device”, which is defined in the next slide. If no internet capable device is in radio range, Cluster Head will collect and store data in compressed form.

  10. Friend Device • A Friend Device is an internet-capable device, such as a laptop, desktop or wireless Access Point. • Properties: • Within max radio range of the sensors (100 m.) • Is aware of the BSN and shares pre-coded secret with the sensors. • Is trusted by the patient, with respect to privacy of data.

  11. Seamless Re-configuration • Goal: BSN should reconfigure its network architecture seamlessly, without requiring intervention of the user. • Use cases: • Phone on body: Traditional BSN architecture. • Phone far away but within max radio range (100m): One sensor becomes Cluster Head, phone acts as BS. • Phone out of max radio range: One sensor becomes Cluster Head, searches for Friend Device and make it a Base Station. • Outdoor: One sensor becomes Cluster Head, communicates with Base Station (phone) using high power. • Outdoor and no internet device: One sensor becomes Cluster Head and stores the collected data.

  12. Body Sensor Networks – Functions (revisited) • Collect medical measurement data. (Sensors) • Aggregate data from sensors. (Cluster Head) • Collect data from other contextual sensors (GPS,etc.) (Cluster Head) • Support high-level applications, queries and actuation. (Base Station + Cluster Head) • Issue real-time remote alerts/requests (e.g. Contacting physician when patient faints) (Base Station)

  13. Pros and Cons of CH Architecture

  14. Rotation of CH • Is rotation of CH role required? • Costs: (for each sensor in the council) • Increased hardware, size, cost. • Restrictions on the location of the sensor – reachable from all other sensors. • Benefits: • Uniform energy consumption among council nodes. • Uniform thermal dissipation among council nodes.

  15. Questions • Is it possible to support multiple communication protocols on a sensor? (802.15.4 and Bluetooth) • If not, how does a 802.15.4 sensor talk to a 802.11 Friend Device? • Is it possible to make sensors internet capable? • How to support remote alarm reports when no base station? • Visual/Audio alerts??

  16. Thank You!

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