IEEE standard – A-QL code for screen mode

A-QL (Asynchronous Quick-Link) is a Screen-2-Camera operating mode being standardized at the IEEE 802.15.7m.

This post introduces the BER measurement method and the performance of A-QL system.

See this video demo for the BER measurement scenario:

 

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Experimental Setup

The scenario for measuring BER is illustrated in Figure 1.

The bit rate is measured at three layers as illustrated in Figure 2.

The evaluation of BER under the impacts of distance and perspective distortion is made to verify the reliable performance of the A-QL system. The entire Tx size is set at 8cm×8cm for all the BER measurement. The PN sequence is typically used for the BER measurement; however, for a better monitoring purpose, the practical measurement of BER herein is based on a known data text message to transmit by A-QL code. The error measured results at three layers, layer one without error correction, layer two with a convolutional code, and layer three with RS and CC code.

 

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BER Measurement Results

The measurement results are shown in Table 1, Table 2, and Table 3.

Table 1 – The count of bit and error at A-QL receiver under the zero-angle viewing

Distance (m)	1.5	3	4.5
Bits received	1128240	1130400	139680
Count of error (layer 1)	151	17848	19757
Count of error (layer 2)	0	0	6627
Count of error (layer 3)	0	0	2935

Table 2 – The count of bit and error at A-QL receiver under the 30-degree viewing

Distance (m)	1.5	3	4.5
Bits received	1018080	1044000	493200
Count of error (layer 1)	67121	261495	91509
Count of error (layer 2)	3448	54659	22845
Count of error (layer 3)	0	0	7379

Table 3 – The count of bit and error at A-QL receiver under the 60-degree viewing

Distance (m)	1.5	3	4.5
Bits received	442080	615600	514600
Count of error (layer 1)	70162	111953	213950
Count of error (layer 2)	19526	33881	133486
Count of error (layer 3)	1935	5475	72145

 

 

 

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Conclusion

The measurements of BER under the impacts of communication distance and the perspective viewing angle are illustrated in Figure 3, Figure 4, and Figure 5. It is notable that the recorded performance of A-QL system is significantly reliable. The short conclusion from the BER measurement is:

• For BER 10^-5 requirement, A-QL operates reliably as far as a 3m distance within perspective angle 30-degree.
• For lower BER requirement (such as in between 10^-2 and 10^-3), A-QL can support as far as 4m with a wider perspective angle (60-degree view).