# Location Information-Assisted Robust Beamforming Design for Ultra-Wideband Communication Systems
## 1 Introduction  
With the development of mobile connectivity and the Internet of Things (IoT), short-range communication has attracted a lot of attention. For financial and practical reasons, it is more attractive to integrate positioning functions into existing communication technologies than to have two separate communication and positioning systems [1]. To provide better communication services for users with different channel state information, the base station (BS) needs to allocate resources asymmetrically according to different CSI [2]. However, due to information asymmetry, it is difficult to obtain the perfect status information at the base station. Therefore, this paper will obtain the user's location information through the positioning algorithm at the base station to assist beamforming. However, positioning performance in indoor environments where a global positioning system (GPS) is unavailable is necessarily affected by multipath propagation and wall obstruction. The current commonly used positioning methods, such as Bluetooth low Energy (BLE), Wi-Fi, and Zig-Bee. It is difficult to meet the communication and location needs of the next generation Internet of things mobile system. Among them, BLE and Zig-Bee technology can greatly reduce the complexity and energy consumption of system design, but their main drawback is the limited data rate [3]. The latest Wi-Fi 6 is capable of reaching a maximum data rate of 9.6 Gb/s, but it suffers from high system complexity and high power consumption, and it may not be used in scenarios with high-precision positioning requirements [4]. Ultra-wideband (UWB) technology, with its significant characteristics [5] such as high transmission rate, low power consumption, and cost-efficiency, has become an indispensable technology in the field of the Internet of Things. Based on the Shannon channel capacity theory, conventional UWB systems can achieve extremely high data transmission rates under a huge system bandwidth by transmitting very narrow Gaussian pulses [6]. For UWB positioning performance, the wide bandwidth of the UWB signal can support centimeter-level ranging accuracy and can resolve multipath delay at nanosecond resolution, so it is very suitable for short-range accurate positioning, communication, and sensing [7; 8]. In addition, UWB technology possesses high robustness to multipath fading and good coexistence with other narrowband systems. UWB communication technology is a promising candidate for improving the data rate. Therefore, UWB is suitable for short-range indoor wireless communication and can be combined with cognitive radio technology, beamforming, and multiple-input multiple-output (MIMO) technology to achieve better system performance [2; 9; 10]. The main problem of UWB is the limited communication transmission range due to low power transmission, the multipath effect, and interference. The combination of MIMO and UWB technologies offers a feasible solution to the power limitation problem of UWB. The integration of UWB and MIMO enables wireless communication systems to increase data rates by transmitting signals over multiple channels without increasing the transmit power [11]. In indoor, dense multipath propagation environments, MIMO technology makes full use of array gain and spatial multiplexing gain to significantly improve spectral efficiency [12]. Beamforming, an important technology for MIMO, can increase the system's anti-interference capability in order to suppress interference, improve data rates, etc. UWB beamforming is different from narrowband signal beamforming. Compared with narrowband beamforming, UWB beamforming needs fewer sensors to obtain the same angle beam, and the uniform power allocation can provide a sidelobe-free beam mode [13; 14]. Through the design of a sparse array, the intercoupling between UWB antennas is effectively reduced. In [14], [PERSON], [PERSON] et al.