 itself or implemented as separate hardware entities that are independently designed, built, and deployed. 96 Open Radio Access Network (O-RAN) Systems Architecture and Design Form factor, environmental and power requirements Besides (3GPP centric) functional requirements, O-RAN system have additional system level requirements associated with them that are needed for successful commercial deployment. We cover a few items here as an example. Referred to "trust architecture" or "secure boot" implies the requirement for the binary image that executes the application code to be unmodified and from a trusted source. This trusted source validation is typically done by boot and application image validation by com- parison to a hash/signature validation against a public key. Starting from low-level boot mechanisms, this allows a "chain of trust" to be established where each application (includ- ing the operating system itself) validates the image of the applications that are loaded subse- quently (including the CU/DU/RU applications itself). A set of Ingress Protection (IP, not to be confused with the "other IP" (Internet Protocol)) codes are defined in the IEC standard 60529. They classify the physical enclosure with regards to protection from intrusion from accidental damage, dust, and water. IP standards define a two-digit number that defines solid particle (first digit) and liquid (second digit) pro- tection as follows (Table 2-5). Some equipment is defined by NEMA ratings rather than IP ratings. NEMA ratings expand beyond IP ratings by inclusion of icing conditions, hazardous areas, and more. Initial translation from NEMA to IP can be found using standard tables, for example in Ref. 8 Fanless operation is required for more stringent IP-rated products. This dictates the use of components (processors, DSPs, FPGAs) with reduced power consumption of 10-30 W instead of the typical ~ 100 W power consumption associated with desktop and server pro- cessors. Both the component-level and board-level power consumption need to 