Applications for Opportunistic Large Arrays
Aravind Kailas, Lakshmi Thanayankizil and Mary Ann Ingram
- The Two-Hop OLA
- The first hop is initiated by the source to recruit nodes in to an OLA.
- The second hop is a cooperative transmission from the newly formed OLA to a distant source which provides range extension.
- An Opportunistic Large Array (OLA)  can be used whenever a collection of nodes have to do a long-range or obstructed communication to a distant receiver; this is the reach back problem
- OLAs provide diversity and thereby extend the range of communication or reduce the transmit power for a given range
- No overhead, centralized control or scheduling algorithm, therefore especially appropriate for high-mobility channels
- BIOSENSING IN FARM ANIMALS 
- Implanted sensors help farmers to detect contagious diseases in early stages and prevent spreading
- Detect time of ovulation for artificial breeding programs
- State of the art: readers must be near the animals to read the implanted tag
- Proposed Solution: Two Hop OLA transmission enables communication between implanted biosensors in a herd of animals to a distant Access Point
- TELEHEALTH 
- Remote Patient Monitoring obtained from patches of sensors on human body.
- Challenge: Energy efficient Body Area Network (BAN) and reliable reception of thesignal by an off-body hub
- Proposed Solution: Two hop cooperative solution is proposed
- First hop from an on-body source sensor to recruit more on-body sensors to form OLA
- Second hop from the OLA to the off-body hub.
- Multi-Hop OLAs in a Strip Network
- When the network is in the form of a strip many nodes wide, OLAs propagate down the strip rather than outward in concentric rings.
Figure 2. Planar Network Architecture (Source is the black dot at the center of the disc).
- STRUCTURAL HEALTH MONITORING
- Detecting early signs of structural stress in buildings/bridges with periodic monitoring
- State of art is monitoring using sensors which are connected using coaxial cables
- The Tsing Ma Bridge in Hong Kong has about 800 permanently installed sensors – installation is very expensive
- Proposed Solution: Multi-hop OLA to hub off bridge
- OLA transmission saves precious battery energy; coupled with energy harvesting, may achieve self-powerd sensors
Figure 1. CDF for the total transmit power for cooperative transmission for the range that achieved 97% reliability for (a) High Density High reliability and (b) Low Density High Reliability
Figure 3. Comparing received power for the Cooperative TX relative to Direct Transmission from the 1st antenna. Four on-body sensors and shadowing-only are assumed. Shows the reduction in fade margin that is possible.
- Preliminary results showed thattwo-hop OLA cooperative transmission schemes showpromise for enabling long range and energy efficient communication in bio-sensing and tele-health applications.
 A. Scaglione and Y.-W. Hong, “Opportunistic Large Arrays: Cooperative Transmission in Wireless Multihop Ad Hoc Networks to Reach Far Distances,” IEEE Trans. Signal Processing, Vol. 51, No. 8, August 2003.
 M. A. Ingram, M. Prasad, A. Kailas, and R. Prasad, “An Investigation of Cooperative Transmission Applied to Agriculture,” Proc. WPMC, Jaipur, India, Dec. 3-6, 2007.
 A. Kailas and M. A. Ingram, “A Cooperative Transmission Technique for Telehealth,” Proc. WPMC, Jaipur, India, Dec. 3-6, 2007 (Invited Paper).
 L. Thanayankizil, A. Kailas, and M. A. Ingram, “Two Energy-Saving Schemes for Cooperative Transmission with Opportunistic Large Arrays,” Proc. IEEE GLOBECOM, Washington, DC, Nov. 26-30, 2007.
- Future Work
- Analysis will be extended to include more realistic channel models
- A complete synchronization model will be developed
- To obtain further energy savings, OLA-T  will be applied to these networks
OLA 4 takes the signal off the bridge