| 9 | | Physical-layer (PHY) cooperation is a technique for achieving MIMO-like performance improvements on small devices that cannot support antenna arrays. Devices in a network transmit on behalf of their neighbors to act as "virtual MIMO" antennas. Since small devices are typically battery constrained, PHY cooperation immediately leads to the following question related to the energy efficiency (bits-per-joule) of devices -- is the performance improvement worth the extra energy costs of transmitting for others? Through an in-depth hardware testbed study, we find that PHY cooperation can improve energy efficiency by as much as 320% or it can reduce energy efficiency by as much as 25% depending upon topology. With this performance gap in mind, we propose the Distributed Energy-Conserving Cooperation (DECC) protocol. DECC tunes the amount of effort each device dedicates to providing cooperative assistance for others so that the energy spent on cooperation is commensurate with the personal benefits from it. With DECC, users can tune their level of cooperation with completely node-localized decision making. Thus, DECC allows nodes to tap into a large energy efficiency benefit when available and a bounded, preset loss when not available. |
| | 7 | Physical layer (PHY) cooperation is a technique for achieving MIMO-like performance improvements on small devices that cannot support antenna arrays. Devices in a network transmit on behalf of their neighbors to act as “virtual MIMO” antennas. Since small devices are typically battery constrained, PHY cooperation immediately leads to the following question related to the energy efficiency (bits-per-joule) of devices – is the performance improvement worth the extra energy costs of transmitting for others? Through an in-depth hardware testbed study, we find that PHY cooperation can improve energy efficiency by as much as 320% or it can reduce energy efficiency by as much as 25% depending upon topology. With this performance gap in mind, we propose the Distributed Energy-Conserving Cooperation (DECC) protocol. DECC tunes the amount of effort each device dedicates to providing cooperative assistance for others so that the energy each device spends on cooperation is commensurate with the personal benefits received by that device. With DECC, users can tune their level of cooperation with completely node-localized decision making. Thus, DECC allows nodes to tap into a large energy efficiency benefit, suffering only a bounded, preset loss when this benefit is not available. |
