In this section, the performance of the proposed transmission audio signal through ACL link over correlated and uncorrelated Rayleigh fading channels is studied through simulation. For the comparison purpose, using different scenarios, non-interleaving, bit-level interleaver, convolutional interleaver, and the proposed chaotic randomizing techniques are also simulated. In the case of correlated Rayleigh fading channel, the Jakes' model is used in the simulation.
In this section, there are many simulation scenarios devoted for evaluating the proposed scenarios of the audio signal transmission.
5.1. Short classic packets DH1
This simulation studies the interleaving effects on the received waveform of audio signal over Rayleigh fading channel. The file-2 is transmitted over uncorrelated Rayleigh fading channel using the DH1 packets. Figure 6 illustrates the waveform of received audio signal at SNR = 25 dB. It is clear that using the interleaving improves received waveform at the same SNR value.
As shown in Figure 6, the bit-level interleaving scenario performs better than other scenarios in this simulation over an uncorrelated Rayleigh fading channel.
The previous computer simulation is repeated over a correlated fading channel. This simulation is devoted to indicate the velocity (V
c
) of the mobile terminal on the waveform of the received audio signals. The simulation utilized the Jakes' model communication channel. The result of this simulation is given in Figure 7, this figure shows the waveform of the received audio signal with assuming the velocity of the mobility is 3 and 10 mile/h.
The result of this simulation reveals that the mobility of the transmitter increases the distortion of the received audio signal. Also, the audio signal transmission needs strong interleaving technique to spread the errors and reduce the bad mobility effects.
In the following simulation, the interleaving effect on the received waveform of audio signal over uncorrelated fading channel is studied. The file-1 is transmitted using the uncoded classic DH1 packets. Figure 8 illustrates the waveform of received audio signal at SNR = 20 dB. It is clear that using the interleaving improves received waveform at the same SNR value. The audio file-1 characteristics match the Bluetooth specifications as mentioned previously. As shown in this simulation results, the waveforms of the received audio signals clear that the bit-level interleaver performs better than the convolutional interleaver. Figure 8 also reveals that the convolutional interleaver enhances the waveform of the received audio signal more than the no interleaving scenario.
In the last simulation of this section, the audio file-2 is transmitted over a correlated Rayleigh fading channel [V
c
= 10 mile/h] using the DH1 packets. Figure 9 illustrates the waveform of received audio signal at SNR = 20 dB. It is clear that the convolutional interleaver scenario performs better than other scenarios over a correlated fading channel.
In the previous simulation, the performance of the audio signals transmission is studied over uncorrelated and correlated fading channels with different mobility velocities. These simulation scenarios indicated that there are bad effects of the mobility on the received audio signal waveforms. Also, it reveals that the interleaving techniques improve the audio waveforms. In the following section, the simulation evaluates the proposed interleaving technique which is the chaotic randomizing technique, based on the chaotic Baker map.
5.2. Randomizing technique
In this section, the simulation results of the proposed technique are presented. The simulation senarios have been carried out for different types of Bluetooth packets; 2DH1 and 2DM1 with the different signal-to-noise ratios (SNRs). The peak SNR, the absolute number of lost frames (NLF), NLF percentage (NLF %), bit error rate (BER), and the correlation coefficient (Cr) are employed for measuring the correlation between the original and the received images; the mean square error (MSE) and the throughput (T) are used for performance evaluation of the Bluetooth network in the different simulation scenarios [26]. The MSE is the cumulative squared error between the received audio signal and the original signal. The mathematical formula for MSE is given in Equation 4 [27].
(5)
The throuput is defined as [28]
(6)
where P
l
is the payload length, PER is the packet error rate, x is the number of time slots occupied by the Bluetooth packet, and t is the duration of the Bluetooth time slots.
In the following, the EDR Bluetooth packets are used for transmitting audio signal over mobile Bluetooth network. The proposed Bluetooth terminal velocity (V
c
) is 10 and 3 mile/h and the frequency carrier is 2.46 GHz. As shown in the following results, with increasing the velocity of Bluetooth terminal, the performance is degraded and the effect of channel on the transmitted signal is increased. Figure 10a gives the frame error rate (FER) of standard 2DH1 and proposed 2DM1 packets which is used for transmitting the audio signal with many proposed cases at V
c
= 3 mile/h. Figure 10b gives FER at V
c
= 10 mile/h. Figure 11 gives the comparison of NFL and FER with the velocity variations with the standard uncoded packets.
From the previous section, the following is concluded: Over mobile Bluetooth network, the quality of audio transmission is decreased with V
c
increasing. Traditional block interleaving of audio file is inefficient over mobile network. The proposed encoded EDR packets with block interleaving of encoded packet performs better than encoded packets (2DM1), which represents 2EV3 voice packets. The performance of standard packets (2DH1) is very bad compared with proposed cases.
Also in this section, the proposed different scenarios for studying the audio signal performance with the proposed randomize techniques are presented. The results of these scenarios are shown in Figure 12. The results of this simulation indicate the effects of the mobility on the audio signal. As shown in this figure in case of V
c
= 3 mile/h, the NFL of the whole simulation scenarios are much closed but with V
c
= 10 mile/h its performance became different.
As shown in the previous results, the randomize technique which is based on the chaotic Baker map concepts scenario performs better than other technique. From these results, the proposed chaotic interleaver packet by packet basis is presented as a novel efficient interleaver. The proposed technique is evaluated through two groups of simulations according to the type of packets which is employed for the proposed technique testing. These packets are the uncoded 2DH1 and encoded 2DM1 EDR packets.
5.3. The mobility effects on the audio transmission performance
This section is devoted for studying the effects of the mobility of the wireless ad hoc network device (V
c
) on the transmitted packets and the received audio signals. In this computer simulation, the v is 1 up to 20 miles/h. Figures 13, 14, and 15 show the NLF, Cr, and MSE variation with the channel SNR with the shortest EDR uncoded packets 2DH1, respecteively. It is clear that with increasing the V
c
of the terminal the NLF increased and the correlation between the original audio signal and the received signal is decreased. As shown in Figure 13, the MSE increased with the velocity increasing. Figure 16 gives the throughput variation with the different velocity of the mobility. So, these results indicate the mobility effects on the different metric of the perfromance evaluation.
The previous results reveal that it should be finding efficient technique for reducing the bad effect of the mobility on the audio signal transmission. In the following simulation scenarios, number of scenarios are proposed for this purpose. The proposed scenarios are applied on different packet lengths. These scenarios depend on that the interleaving technique is an efficient method for anti-fading, and is raised to solve serious long burst interference in some fading channels. The proposed scenarios are tested in two groups of the EDR packets with different velocities with employing the widely accepted Jakes' model to modelate the simulation environment. Figure 17 gives the waveforms of the received audio signal with different V
c
of the mobility.
5.4. Audio signal transmission using 2DH1 and 2DM1 packets
This section is devoted to test the efficiency of audio transmission using the short uncoded 2DH1 and encoded 2DM1 EDR packets with the different scenarios. In the first computer simulation, the audio signal has been transmitted over a correlated fading channel with an SNR = 15 dB. The results of this simulation are shown in Figure 18. From these results, it is clear that the effect of the proposed randomizing interleaving based on the chaotic Baker map is better than that of the other schemes. As shown in Figure 18, the waveform of the received audio signal is improved with the proposed scenarios. The proposed velocity of the mobility in this simulation is V
c
= 3 mile/h.
Figures 19 and 20 show the variation of the Cr and the MSE of the received audio signals with the channel SNR, respectively. These figures reveal that the proposed chaotic interleaver improves the quality of the received audio signal. It increases the correlation and decreases the error between the received and the original signals. Figure 21 indicates the effectiveness of the proposed scenarios on the error performance through the BER variation with the channel SNR. As shown in this figure, the error spreading capability of the proposed chaotic randomizing technique enhances the error performance over the mobile channel for the audio signal transmission. Figure 22 gives the NLF % variation with the channel SNR. The effect of the velocity on the dropped packets is indicated in Figure 15 for the uncoded 2DH1 EDR packets, in this simulation the dropped packets are calculated as percentage where the audio file is segmented and transmitted through uncoded and encoded packets.
In the previous simulation, the mobility effect is studied on the audio signal transmission in a fixed and mobile communication channels in many of scenarios. Also, it evaluates the proposed chaotic interleaver on the whole audio file and packet-by-packet basis. The simulation results reveal that the ACL link improves the throughput of the audio signal. Also, the interleaving techniques enhance the received audio signals. The proposed data randomizing tool performs better than traditional interleavers over the mobile Bluetooth network. As shown in the results, the MSE and Cr of the received audio signals are improved by applying the proposed scenario of the chaotic randomizing technique.