1. Luis E. Palafox and J.Antonio Garcia-Macias CICESE – Research Center 2009 Proceedings of the 4 th international conference on Wireless pervasive computing 박 유 진

2.  Introduction  Implementation ◦ Node selection criteria ◦ Security Features ◦ Counter Synchronization Protocol ◦ Speech recognition  Experiments and Result ◦ Scenario ◦ Traffic analysis ◦ Energy consumption  Conclusions

3.  Voice Command Capture System  Wireless Sensor Network ◦ Resource limitation  Energy  Memory space  Etc…

4.  UC Berkeley’s MicaZ motes ◦ 2.4 GHz IEEE 802.15.4, Tiny Wireless Measurement System ◦ 250 kbps, High Data Rata Radio ◦ Light, Temperature, RH, Barometric Pressure, Acceleration… ◦ Pair of AA-sized batteries ◦ RF power : -24dBm to 0 dBm ◦ Power consumption  TX : 11 mA(-10 dBm), 14 mA(-5dBm), 17.4 mA(0 dBm)  RX : 19.7 mA

5.  Cluster ◦ 3 Sensor node  2KHz sampling frequency (sense signal intensity exceed a threshold)  HFS(High Frequency Sampling) mode (8.192 kHz, 3 seconds audio sampling) ◦ 1 Clusterhead node  Node selection  Base station ◦ Speech recognition task(VR Stamp Toolkit)

6.  Manage work load → Increase System lifetime ◦ Audio Operation(ADC, Store EEPROM, Tx) ◦ Energy limitation  Data Recollection Protocol ◦ Report Event Message(Sensor Node) ◦ Node Selection Message → High Frequency Sample state

7.  RC5 algorithm ◦ Very low memory requirement ◦ Fast encryption/decryption ◦ Flexible data block and key size ◦ 12 round, 16-byte cryptographic key ◦ Encrypt Synchronization Counter

8.  Cluster Synchronization ◦ Counter Update Beacon(Random Counter Value) ◦ Coordinated by the Cluster-Head(CH)  Speech recognition ◦ VR Stamp Toolkit ◦ RSC-4128 speech processor ◦ Attached to the base station via USB port

9.  Scenario ◦ 2 Clusters(4 nodes : 3 Sensor nodes, 1 Cluster header node) ◦ 1 Main Server  recognize voice command ◦ 1) Simple capture-and-send  Detect human voice starts  Record 3 second of audio data ◦ 2) Data Recollection Protocol  Detect voice event  Select recording Node

10.  Simple capture-and-send  800 audio data messages for each recognized nodes  Data recollection Protocol  1 Event Report Message for each recognized nodes  1 Node Selection Message  800 audio data messages

11.  Simple capture-and-send  Life Time is reduced by 17% (Worst case)  Data recollection Protocol  Low dependent of the number of recognized nodes  Depend on the selection criteria in the Clusterhead

12.  Voice capture sensor network for ubiquitous home environments ◦ Speech recognition ◦ Counter Synchronization Protocol ◦ Security functions  Improve system lifetime ◦ Node Selection Protocol  More small traffic  Load balancing scheme