With the ongoing congestion of wireless spectrum in the forthcoming 5G era, spectrum sharing has received significant attention in the past years. Besides employing a very large number of antennas at the base station in 5G, modern wireless communication systems also require more spectrum resources beyond current spectrum allocations to achieve higher data rates. As such, it will increase the possibility of success for 5G communication systems.

In addition to the advancement in cognitive radio, more recently, communication systems attempted to use the spectrum resources initially allocated to radar systems. Fortunately, the problem of spectrum competition between radar and communications has been addressed by the coexistence or joint transmission. The former requires to minimize the mutual interference between radar and communications while they use the same frequency bands. The latter performs the primary radar function and the secondary communication function in the same spectrum resources.

Among various joint transmission applications, dual-function radar-communications is a typical one. The synthesized beamforming problem for dual-function radar-communications can be formulated as

$\begin{array}{rcl} &\min\limits_{\boldsymbol{w}_{\ell}}\ \max\limits_{\theta_{m}}& \left\vert e^{j \psi(\theta_{m})} - \boldsymbol{w}_{\ell}^{\mathrm{H}} \boldsymbol{a}(\theta_{m})\right\vert, \theta_{m} \in \Theta, \nonumber \\ &\mbox{subject to}& \left\vert \boldsymbol{w}_{\ell}^{\mathrm{H}} \boldsymbol{a}(\theta_{p}) \right\vert \le \varepsilon, \theta_{p} \in \bar{\Theta}, \nonumber \\ & & \left\vert \boldsymbol{w}_{\ell}^{\mathrm{H}} \boldsymbol{a}(\theta_{r}) \right\vert = \Delta_{r}, 1 \le \ell \le L, 1 \le r \le R, \nonumber \end{array}$

is the complement set of $\Theta$ representing the sidelobe region, $\boldsymbol{a}(\theta)$ is the response vector of the transmitting antenna array at the angle $\theta$, $\varphi(\theta)$ is the phase profile of user’s choice, $\boldsymbol{w}_{\ell}$ is the desired beamforming vector which achieves the sidelobe level $\Delta_{\ell}$

at all the communication receivers located at angles $\theta_{r} \in \bar{\Theta}$, $R$ is the number of communication receivers located in the sidelobe region, and $L$ denotes the number of allowable sidelobe levels.

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VOCAL Technologies offers custom designed spectrum sharing solutions, between radar and communications applications, between communications and radio astronomy, or others. Our custom implementations of such systems are meant to deliver optimum performance for your specific signal processing task. Contact us today to discuss your solution.