All Analogue Full-duplex Dual-receiver Radio for Wideband Mm-wave Communications

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Smartphones, tablets and laptops are widely used for multi-user video conferencing, watching video and TV, playing video game, downloading/uploading large files and applications. Data exchanged over wireless networks is significantly increasing annually, and hence the data speed needs to be increased with the demand to keep users happy. Radio network designers and spectrum regulators are facing the daunting task of efficient resource planning to meet the growing demand. Considering spectrum limitation, providing ultra-speed wireless systems can only come through some breakthrough technologies. The full-duplex (FD) radio is one technology with the potential to double the speed and if planned at mm-wave bands, it can offer a huge bandwidth.The massive benefits of broadband mm-wave FD in HetNets are well-known including very fast Gbit inter-operation between small cells in wireless networks. The availability of low-cost mm-wave MMIC-based subsystems together with the simple infrastructure setups for FD radios would place broadband mm-wave FD radios ahead of its rival, namely, the complicated low frequency broadband massive multi-input multi-output (MIMO) systems operating in multiple channels. Indeed, the low-cost broadband infra-structure networks based on FD would be very attractive to mobile operators continuously looking for cheap solutions to provide very high-speed communication coverage in complex environments like underground tunnels, large/high-story buildings, and busy densely populated city areas. Indeed, millions of femtocells of wideband mm-wave FD radios can be envisaged to operate worldwide on the mature of the broadband mm-wave FD technology, ensuring substantial revenue (of the order of billions of pounds) for contributors to the technology.A FD radio uses one channel to transceive and hence self-interference (SI) is its major problem. In FD radios, the required SI cancellation (SIC) depends on transmitter power and signal bandwidth. Typically, a SIC of 60 dB to 110 dB is necessary for a reliable FD system. In low frequency FD radios, this large suppression is normally achieved in multiple stages; ie: in antenna system, in receiver front-end, and in baseband with digital signal processing (DSP).Assuming 10% fractional bandwidth, mm-wave carrier frequencies have the potential to modulate fast signals of a few GHz bandwidth; eg: 3 GHz bandwidth becomes available at 30 GHz carrier. For such a wide baseband, the DSP-based SIC cannot be an option, since no miniaturised power conscious DSP unit for implementation in small mobile/fixed devices is available presently to deal with fast signals of a few GHz bandwidth. To remove the DSP constraint, several promising techniques have been proposed to mitigate the SI in mm-wave FD radios, but they are still under research with limited practical results presented so far in the literature.Recently under an EPSRC grant we have developed a new SIC technique free from DSP. Based on this, we demonstrated a narrow band (60 MHz) FD radio at 3.2 GHz microwave carrier. Our demonstrator achieved a total of 81.5 dB SIC at -5.6 dBm transmit power. Our new system owes its digital-free performance to a two-receiver architecture purging the need for the DSP stage. This property is anticipated to be extremely suitable/important for realising all analogue broadband mm-wave FD systems.The novelty of this proposal, distinguishing it from and indeed levitating well above the work in the literature, is unlocking the potential of our new narrow band FD radio architecture to exploit its several advantages including an analogue baseband SIC solution (i.e., free from DSP) and a self-mutipath reflection interference cancellation via a three-port dual antenna system with a high isolation between transmitter and the dual-receiver. In this work we are to put to test our experiences in developing our new dual-receiver microwave FD radio to realise a unique DSP-free broadband mm-wave FD radio.