Commit 6adab4e2 authored by Tran Huy Vu's avatar Tran Huy Vu

update multi-device charging (microbenchmark)

parent 43513104
......@@ -134,9 +134,17 @@ How increasing number of antennas changes the harested power
\caption{Time-multiplexing of narrow beam to 2 devices at 1.7m separation.}
\label{fig:multiplexfar}
\end{figure}
\begin{figure}
\centering
\includegraphics[scale=0.5]{2device2beams.pdf}
\caption{Time-multiplexing of narrow beam to 2 devices at 1.7m separation.}
\label{fig:edev2beam}
\end{figure}
We continue to evaluate our system to support multiple device concurrently. We placed 2 devices on the table with two different spacing of 30cm and 1.7m respectively. We then run the beamforming algorithm with two operational mode: time multiplexing and concurrent beams.
In time multiplexing mode, the AP schedule the beam switching at 3 different periods of 10 seconds, 30 seconds and 90 seconds. Although the efficiency of 2 devices are different because of the hand-tuning of the harvester. We can see clearly that the total residual power of the 2 devices is much higher when the 2 device are placed next to each other with 30cm separation. This can be applied to power several items in an wearhouse or mall within the beamwidth.
2 devices - time multiplexing (8-antenna beam). 2 devices -
concurrent 2 4-antenna beams
On contrast, in concurrent beams mode, the separated spacing shows significantly better total residual power. Although in the separated spacing mode, one device is moved to the corner closer to the AP, the other device is moved further away from the AP. In general, this experiment suggest that if the devices are close to each other, the system should use time multiplexing, and if they are widely separated, the concurrent beams seems working better.
\subsection{Transfer Energy at Maximum Tx Power}
\begin{figure}
......
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