Fair Initial Access Design for mmWave Wireless

Abstract

Millimeter-wave (mmWave) systems use highly directional beams with narrow beamwidths to overcome the high path loss associated with their frequency bands. The use of narrow beams complicates the link establishment process as the transmitter and receiver need to search for appropriate beams before they can communicate with each other. Existing mmWave standards address the beam search process as part of the initial access (IA), and use contention based schemes that let multiple clients train their beams in the same search interval. However, there exists a severe power imbalance among competing clients’ beams, as clients naturally have different orientations and are at different distances from the same access point. This beam power imbalance coupled with poor contention protocols results in poor IA fairness in dynamic systems with multiple clients. We propose a joint power control and contention adaptation protocol (coined JPOC) that addresses this unfairness problem. JPOC uses an open-loop and client-side power control mechanism that reduces the beam power imbalance among competing clients. It also uses a model-driven contention adaptation protocol that optimally adjusts the duration of the contention time according to the system dynamics. Comprehensive evaluation through a mixture of experiments and simulations show that compared to existing 802.11 ad/ay standards, JPOC substantially reduces the contention overhead and increases the IA fairness.