Abstract
In a millimeter wave (mmWave) communication system with transmit/receive (Tx/Rx) beamforming antennas, small variation in device behavior or an environmental change can destroy beam alignment, resulting in power loss in the received signal. In this situation, the beam-tracking technique purely based on the received signal is not effective because both behavioral changes (rotation, displacement) and environmental changes (blockage) result in power loss in the received signal. In this paper, a motion sensor based on microelectromechanical systems (MEMS) as well as an electrical signal is used for beam tracking to identify the cause of beam error, and an efficient beam-tracking technique is proposed. The motion sensors such as accelerometers, gyroscopes, and geo-magnetic sensor are composed of an attitude heading reference system (AHRS) and a zero-velocity detector (ZVD). The AHRS estimates the rotation angle and the ZVD detects whether the device moves. The proposed technique tracks a beam by handling the specific situation depending on the cause of beam error, minimizing the tracking overhead. The performance of the proposed beam-tracking technique is evaluated by simulations in three typical scenarios.
Highlights
In recent years, the millimeter wave band has attracted great interest for next-generation mobile communication systems that may require up to 1000 times over 4G cellular systems
An analog beamforming design is considered over digital beamforming at both the base station (BS) and mobile station (MS) in mmWave communication systems because multiple analog chains at mmWave frequencies are costly, and sampling an analog signal at the GHz rate consumes a substantial amount of power [4]
We use an attitude heading reference system (AHRS), which provides the roll, pitch, and yaw of the MS using microelectromechanical systems (MEMS) devices, and a zero-velocity detector (ZVD), which discerns whether the MS has moved using information only from the accelerometer
Summary
The millimeter wave (mmWave) band has attracted great interest for next-generation mobile communication systems that may require up to 1000 times over 4G cellular systems. The beam alignment can be destroyed by even small variation in device behaviors such as rotation and displacement Environmental changes such as link blockage by a foreign object may result in a significant drop in the signal power level [9,10]. Techniques handling a specific type of error, such as switching to the secondary path when blockage occurs, have been proposed [13] It will be more effective if we can identify the cause of power loss and handle the specific situation depending on the cause of beam error. An efficient beam-tracking technique for an MS in mmWave communication systems is proposed by utilizing both mechanical and electrical signals.
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