September 29th summary : Node to Node Characterization

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      Experiment location: Node2 at Seattle Boat Company (SBC), Node3 at Pocock (Fig1.)

Figure 1: Experiment Location             

Figure 2 depicts the packet delivery ratio (PDR) for each mode. Expected behavior is to see improvement in PDR as transmission power(TXPWR) increases. The expectation was met from MODE1 to the second trial of MODE4, however, we see performance drop at 3^rd trial (-10dB) of MODE4 and failed to transmit at MODE5 all together.

Figure 2: Packet Delivery Ratio

Figure 3 presents the ESNR performance in this experiment (definitions can be found in Ref.1) Generally speaking, ESNRs increase with transmission power increment, until at certain points they reach constant levels. ESNR achieves constant level much earlier due to the limitation brought by channel estimation error. Overall, ESNR values in this test condition are low (average 9 dB), which indicates channel couldn’t handle high data rate (Ref. 2.) Ideal channel should consistently produce ESNR above 10 dB to enable high data rates (Mode4 and 5.) Moreover, ESNR seems to be mode independent.

Figure 3: ESNR as a function of TXPWR, seems mode independent.

CIR results consistently show a delay spread of around 28ms (Figure 4.)

Figure 4: Example CIR reading

Figure 5 shows CIR in frequency domain between to different CIRs, one taken in the morning with a “good behaving channel” and the other in the afternoon with “harsh channel conditions.” It seems noise levels in magnitude response in the afternoon CIR is larger than the morning one. This can be a good reason for lower ESNR despite transmitting signals with considerably higher TXPWR. Moreover, phase change seems to be faster in the afternoon, which is the main influence factor of the performance.

Figure: Comparison between CIR taken in morning and afternoon