Relay When Blocked: A Hop-by-Hop mmWave Cooperative Transmission Protocol

Obstacles are generally treated as harmful objects for millimeter wave (mmWave) networks due to the directional transmission of mmWave signals and the blockage effects of the obstacles. In this letter, smart antennas are deployed at each blockage to exploit the directivity of the mmWave signal such that the blocked signal at each obstacle can be picked up and forwarded to the destination. Assuming a random Boolean model for the spatially distributed blocking obstacles, the joint distribution of the ordered blockage distances is first characterized, which is then used to develop the exact as well as the asymptotic outage probability conditioned on a given number of blockages. Both the theoretical analysis and numerical results show that the proposed protocol achieves full diversity order and can eliminate the error floor caused by the blocking effects, achieving thus superior performance to previous solutions.