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A novel link scheduling method based on CAZAC sequence for device-to-device communication system

In this paper, link scheduling process for device-to-device (D2D) communication system is presented, which is essentially performed in order to sense the interference condition and to decide whether each device performs the data transmission or not. Among the typical D2D communication systems, FlashLinQ developed by Qualcomm considers single-tone communication based link scheduling method. In this method, each link has a unique pair of sub-carriers, so the devices can easily estimate signal-to-interference power ratio (SIR) of links by calculating the ratio between received tone powers. In practical multi-path channel environment, however, the single-tone based SIR estimation causes a critical scheduling error problem because a wide difference between ideal full-band SIR and estimated SIR can occur due to the influence of frequency selective fading. In order to overcome this problem, we propose a novel link scheduling method based on constant-amplitude zero-auto-correlation (CAZAC) sequence for D2D communication system. In the proposed method, each link has a unique offset value set for the generation of circular shifted CAZAC sequences. The circular shifted CAZAC sequences are transmitted using multiple sub-blocks in the whole bandwidth, and then each device can obtain nearly full-band SIR using sub-band-wise circular cross correlation operation.