Interference-Free Probing for Relay-Assisted Cross-Channel Gain Estimation in Two-Tier Networks

In frequency division duplex (FDD) two-tier networks, the probing technique has recently been introduced into the cross-channel gain estimation, which requires the tier-two user to act as a relay for the tier-one user. Then the tier-two user can autonomously estimate the cross-channel gain. However, the improper location of the tier-two user, i.e., the relay, may cause severe interference to the tier-one user. In this paper, we analyze the impacts of the probing on the tier-one user and find two location regions, in which the probing does not cause interference. Based on that, we develop a detection method to let the tier-two user autonomously identify its located region. Then the interference caused by the probing can be avoided. Simulation results demonstrate that the proposed method has about 90% correct detection probability.