Analysis and design of data transmission protocol for 1024-channel retinal prosthesis

Epiretinal prostheses deliver electrical pulses through a great number of stimulation electrodes to generate visual perception. Since a large amount of stimulation parameters have to be sent into the eye wirelessly, the transmission efficiency and data loss are critical design factors. While the error rate of wireless transmission might not be perfect due to the limited power dissipation allowed in the eyeball, data loss can be reduced by altering the size of data packets. In this paper, the correlation between packet length and data loss are analyzed, and we find that more than 10 times of reduction in data loss can be achieved by shortening the data packets. The costs and benefits of using error-correcting codes (ECC) are also evaluated. A data packet protocol for 1024-channel retinal prosthesis as well as the corresponding receiver circuitry are then designed based on the results of the analyses. The circuit occupies 330 μm × 262 μm using 0.18 μm CMOS technology. With the flexibility provided by the protocol and receiver circuitry, data packet configuration (size and ECC on/off) can be adaptively adjusted to optimize for real-time wireless channel error conditions.