To extend the proposed antenna configuration and beam focusing scheme to handle scenarios with imperfect channel knowledge, we can incorporate robust optimization techniques. By introducing robust optimization into the design process, we can account for uncertainties in the channel state information. This involves formulating the optimization problem with a focus on worst-case scenarios, ensuring that the system's performance is guaranteed even under imperfect channel knowledge. Techniques such as robust beamforming and robust precoding can be employed to mitigate the effects of channel uncertainties. Additionally, adaptive algorithms that continuously update the beamforming weights based on real-time channel feedback can also enhance the system's robustness in the face of imperfect channel knowledge.