The brainwave control has been progressed from the wired connection to the wireless electromagnetic wave, which actually create the same effect.
The fundamental difference between the wired and wireless is located how to irradiate the wave. If the same electromagnetic wave is generated wirelessly, the same effect appears on the human body when wired. There originally exists a distance even though the electrode is attached to the brain, as it is actually outside the skull.
There is always a space between objects, which is essentially an issue whether they are close enough to flow an electrical current or not. The distance of 0.01 millimeter is attached enough to flow, but it fails at some point when increasing its distance. If the wired connection is failed, the electromagnetic wave loses its effect to the brain.
It is necessary to find out the effective way to send the wave wirelessly to the distant subject. The wave is composed of the frequency rather than the electric pulse, hence it is critical how to irradiate the specific frequency wirelessly.
The brainwave is a very low frequency wave, in other words, an ultra-long wave. For example, the alpha wave is a frequency around 10Hz, which means there are 10 strokes of the amplitude per second. This can be compared to a frequency used for the mobile communication, one of which is 2GHz, stroking 2 billion times per second. Both of them are called as electromagnetic waves, though there is an immense deviation. The frequency of radio is around 1000KHz, even stroking 1 million times per second, a lot more than the brainwave.
There are other types of the brainwave, such as a beta wave whose frequency is at the double-digit Hertz. On the other hand, there are lower frequencies than the alpha; the delta wave is at 1-3Hz and the theta wave is at 4-7Hz. These four segmentations of the wave is generated inside the brain.
It is quite difficult to irradiate these ultra-long waves wirelessly, as it requires an extremely long antenna, though that is the only problem. Once this is overcome physically, the next issue appears about its directivity.