Information Technology Reference
In-Depth Information
R
ESULTS
Figures 4 and 5 show the results obtained for the different packet types with fading
parameter
m=∞
(AWGN channel). For each channel condition, a different packet has the best
performance. Bluetooth specification does not suggest any scheme indicating how to select
packet type during communication. Each link can employ different packet type to transmit
data information. Due to the different packet length, error-check and error correcting
schemes, each packet has the different retransmission probability when it has the different
average SNR [15]. From the results, the following adaptive packet selection scheme can be
observed: when SNR > 15.2 dB, the 3-DH5 packet achieves the highest throughput and can
be selected. For 10.5dB < SNR < 15.2dB, select the 2-DH5 packet, for 9.7dB < SNR < 10.5
the 2-DH3 is the best packet and finally, for SNR < 9.7 dB, select the 2-DH1 packet [15].
In the evaluation of energy efficiency a sensor sends 100.000 packets to the sink
(
n
pac
=100.000), considering different number of hops [7]. The value of the Nakagami fading
parameter is
m
=1. The data is some variable that could be transmitted with few bytes of data.
The data size to be transmitted was chosen to be 17 bytes. Although other data sizes could be
used, this value may indicate a tendency of the packet performance. The value of 17 bytes
was chosen because it is the maximum number of data bytes that the DM1 and BCH packets
can transmit. Figures 6 to 8 show the results obtained for the energy efficiency of some
packets as a function of signal-to-noise ratio, for different number of hops. Only the main
packets are shown in the graphs. For a single hop network (Figure 6) the AUX1 packet has
the best efficiency for SNR values higher than 15 dB, approximately. When the SNR is below
this value, the BCH3 packet is the best.
Figure 4. Throughput for basic rate data packets.
