Section: 5.2.2 Resource elements
Content: Each element in the resource grid is called a resource element and is uniquely defined by the index pair in a slot where and are the indices in the frequency and time domains, respectively. Resource element on antenna port corresponds to the complex value . When there is no risk for confusion, or no particular antenna port is specified, the index may be dropped. Quantities corresponding to resource elements not used for transmission of a physical channel or a physical signal in a slot shall be set to zero.