A TTI having a time duration of 1 ms may be referred to as a “normal TTI” (TTI in LTE Rel. 8 to 12), a “l(fā)ong TTI,” a “normal subframe,” a “l(fā)ong subframe,” and so on. A TTI that is shorter than a normal TTI may be referred to as a “shortened TTI,” a “short TTI,” “a partial TTI (or a “fractional TTI”), a “shortened subframe,” a “short subframe,” a “minislot,” “a subslot” and so on.
Note that a long TTI (for example, a normal TTI, a subframe, etc.) may be replaced with a TTI having a time duration exceeding 1 ms, and a short TTI (for example, a shortened TTI) may be replaced with a TTI having a TTI duration less than the TTI duration of a long TTI and not less than 1 ms.
A resource block (RB) is the unit of resource allocation in the time domain and the frequency domain, and may include one or a plurality of consecutive subcarriers in the frequency domain. Also, an RB may include one or more symbols in the time domain, and may be one slot, one minislot, one subframe or one TTI in length. One TTI and one subframe each may be comprised of one or more resource blocks. Note that one or more RBs may be referred to as a “physical resource block (PRB: Physical RB).” a “subcarrier group (SCG: Sub-Carrier Group),” a “resource element group (REG).” an “PRB pair,” an “RB pair” and so on.
Furthermore, a resource block may be comprised of one or more resource elements (REs). For example, one RE may be a radio resource field of one subcarrier and one symbol.