Advanced Air Mobility (AAM) is envisioned to bring a new mode of air transportation with promising benefits to the society, at large. AAM services such as air taxis and air ambulances are expected to bridge the digital divide between urban and rural/tribal regions. For AAM services to be deployed at large-scale, there are several technical challenges that need to be addressed. Reliable communications to support autonomous airspace operations is one such challenge. This paper presents a comprehensive architecture for ground-based communication support for AAM vehicles. The architecture includes: (1) air corridor design, (2) unit air cell that serves as a building block for air corridor, and (3) novel antenna designs for the base station and the AAM vehicle. Detailed analysis is presented for these architectural elements to demonstrate their viability for practical implementation.