## 5 Experimental Tests  
Experimental tests of DSSS communication were carried out in the model pool of the Gdarsk Tech. The pool is 40 m long, 4 m wide, and 3 m deep. The location of the transmitting and receiving hydrophone is shown in Figure 10 and corresponds to the system configuration assumed during the simulation tests using measurement pool simulator. Transducers were immersed at a depth of 1.5 m.  
Both the transmitter and receiver of the UAC system's laboratory model use laptop computers with the Matlab environment for digital signal generation and analysis. Laptop computers communicate with underwater HTL-10 telephones from Sonel Sp. z o.o., developed for the needs of the Polish Navy. It performs the generation of the communication signal and an analysis of the received signals using digital signal processors by Texas Instruments: a 16-bit TMS320 VC5416 fixed-point processor and a TMS320C6713B (DSP) 32-bit floating-point processor. It contains multichannel analog-to-digital converters with a 16-bit resolution and a maximum sampling frequency of 250 kHz. The source of the sampling frequency is an AD9834 direct digital synthesis circuit from Analog Devices. The underwater telephone works with an NI-USB636 external recording and generating device from National Instruments. The HTL-10 devices pass the analog signal to a hydroacoustic transducer and receive the signal from a receiving transducer. Both the transmitting and receiving transducers are omnidirectional transducers with a resonant frequency of 34 kHz.  
Figure 10: The dimensions of the model pool and the location of the transmitting (projector) and receiving transducers.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Spreading** & **BER** & **Transmission** & **BCH Code** & **Transmission** & **BCH Code** & **Transmission** \\
**Sequence** & **No ECC** & **Rate** & **Rate** & **Rate** & **Rate** & **Rate** \\  & & **No ECC** & **BER \textless{} 0.01** & **BER \textless{} 0.01** & **BER \textless{} 0.001** & **BER \textless{} 0.001** \\ \hline \multicolumn{8}{c}{**Bandwidth = 1 kHz**} \\ \hline m-sequence & \textless{}0.001 & 3.92 bps & — & 3.92 bps & — & 3.92 bps \\ \hline Kasami code & \textless{}0.001 & 3.92 bps & — & 3.92 bps & — & 3.92 bps \\ \hline Gold code & \textless{}0.001 & 3.92 bps & — & 3.92 bps & — & 3.92 bps \\ \hline \multicolumn{8}{c}{**Bandwidth = 2 kHz**} \\ \hline m-sequence & 0.007 & 7.84 bps & — & 7.84 bps & 5/7 & 4.48 bps \\ \hline Kasami code & 0.02 & 7.84 bps & 4/7 & 4.48 bps & 5/15 & 2.61 bps \\ \hline Gold code & 0.02 & 7.84 bps & 4/7 & 4.48 bps & 5/15 & 2.61 bps \\ \hline \multicolumn{8}{c}{**Bandwidth = 4 kHz**} \\ \hline m-sequence & 0.35 & 15.69 bps & 13/4095 & 0.05 bps & \textless{}13/4095 & \textless{}0.05 bps \\ \hline Kasami code & 0.26 & 15.69 bps & 12/20147 & 0.09 bps & \textless{}13/4095 & \textless{}0.05 bps \\ \hline Gold code & 0.35 & 15.69 bps & 13/4095 & 0.05 bps & \textless{}13/4095 & \textless{}0.05 bps \\ \hline \hline \end{tabular}
\end{table}
Table 8: Results of simulation tests using Watermark software; KAU2 channel.  
Using such a laboratory model of the UAC system, DSSS communication tests were carried out, preceded by the measurement of the UAC channel transmission parameters, determining the degree of multipath propagation.