A University of Waterloo engineering research team led by Amir K. Khandani, the Canada Research Chair in Wireless Systems, has developed new technology that enables wireless signals to be sent and received at the same time on a single radio channel frequency. Their website notes:
Current wireless systems are one-way (similar to walkie-talkies), meaning that disjoint time or frequency segments are used to transmit and to receive. Realization of two-way wireless has challenged the research community for many years, generally believed to be impossible. This talk establishes the theory and presents practical realization of two-way wireless. In contrast to the widely accepted beliefs, it is shown that two-way wireless is not only possible, but is fairly simple, with virtually no degradation in signal-to-noise-ratio. More importantly, it is shown that two-way wireless can do much more than just doubling the rate. The innovation is in the antenna design and multiple levels for cancelling self-interference. Methods are developed to support multiple antenna (MIMO) two-way transmission, and asynchronous two-way links (useful in networking applications). These findings are expected to have a profound impact on wireless transmission, networking and security in the near future, more significant than other major breakthroughs in the last few decades.
The website also includes several videos demonstrating their system.