Cisco ' s Embedded Wireless Controller (EWC) architecture is the ideal solution for small deployments with strict budget constraints where only the access points can be replaced. EWC is a controller function that runs directly within the Cisco Catalyst 9100 Series access point itself — eliminating the need for a dedicated physical or virtual WLC appliance. The APs serve dual roles as both the wireless radio infrastructure and the controller platform. The unified model (Option B) requires a dedicated hardware WLC such as the 9800 series, exceeding the customer ' s budget. Fabric (Option C) requires Cisco DNA Center and SD-Access infrastructure, making it cost-prohibitive for a small deployment. Cloud (Option D) requires ongoing subscription fees that may not fit a fixed one-time budget. EWC provides enterprise-grade features including centralized SSID management, RRM, and client mobility within the AP cluster — all without additional controller hardware investment. This makes it the canonical solution for SMB migrations from autonomous deployments. Reference: WLSD Study Guide — Controller Deployment Models, Embedded Wireless Controller Architecture, SMB and Branch Wireless Design.