Blockage and directivity in 60 GHz wireless personal area networks: from cross-layer model to multihop MAC design

TLDR

Millimeter‑wave WPANs rely on directional links to overcome high path loss, yet they are highly vulnerable to blockage from obstacles such as humans and furniture. We present a cross‑layer modeling and design approach for multi‑Gigabit indoor WPANs using the 60 GHz band. We develop a diffraction‑based model to predict link connectivity amid stationary and moving obstacles and design a multihop MAC protocol that exploits directional links to sustain high network utilization with low overhead. The results show that adding a small number of relay nodes enables multihop communication to preserve connectivity in outage‑prone scenarios, and the proposed MAC protocol achieves high utilization with low overhead.

Abstract

We present a cross-layer modeling and design approach for multiGigabit indoor wireless personal area networks (WPANs) utilizing the unlicensed millimeter (mm) wave spectrum in the 60 GHz band. Our approach accounts for the following two characteristics that sharply distinguish mm wave networking from that at lower carrier frequencies. First, mm wave links are inherently directional: directivity is required to overcome the higher path loss at smaller wavelengths, and it is feasible with compact, low-cost circuit board antenna arrays. Second, indoor mm wave links are highly susceptible to blockage because of the limited ability to diffract around obstacles such as the human body and furniture. We develop a diffraction-based model to determine network link connectivity as a function of the locations of stationary and moving obstacles. For a centralized WPAN controlled by an access point, it is shown that multihop communication, with the introduction of a small number of relay nodes, is effective in maintaining network connectivity in scenarios where single-hop communication would suffer unacceptable outages. The proposed multihop MAC protocol accounts for the fact that every link in the WPAN is highly directional, and is shown, using packet level simulations, to maintain high network utilization with low overhead.