Millimeter-Wave Cellular Wireless Networks: Potentials and Challenges

TLDR

Millimeter‑wave (mmW) frequencies between 30 and 300 GHz promise orders‑of‑magnitude bandwidth gains through beamforming and spatial multiplexing with multielement antenna arrays. The paper surveys mmW measurements and capacity studies for small‑cell urban deployments and discusses technologies such as adaptive beamforming, multihop relaying, heterogeneous networks, and carrier aggregation to address the challenges. The study highlights that mmW systems require highly directional, adaptive transmissions with strong isolation and can suffer outages, impacting multiple access, channel structure, synchronization, and receiver design, and proposes solutions such as adaptive beamforming, multihop relaying, heterogeneous networks, and carrier aggregation. Measurements in New York City show that mmW can provide up to ~200 m NLOS street‑level coverage and, according to statistical channel models, can deliver more than tenfold capacity over 4G at current densities, though substantial redesign of cellular systems is required to realize these gains.

Abstract

Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.