a port. An antenna port is defined by its associated reference signal. The antenna ports are logical entities and there is no one-to-one mapping to the physical antennas. The physical antennas are dynamically mapped to the antenna ports per slot in the time-domain. The set of antenna ports supported depends on the reference signal configuration in the cell and are as follows: 1. Cell-specific reference signals support 1, 2, or 4 antenna ports where the antenna port number p, p = 0 for one transmit antenna, p = 0,1 for two transmit antennas, and p = 0,1,2,3 for four transmit antennas; 2. MBSFN reference signals are transmitted on antenna port p = 4; 3. UE-specific reference signals are transmitted on antenna ports p = 5, p = 7, p = 8, or p = 7,8; 4. Positioning reference signals are transmitted on antenna port p = 6. The cell-specific reference signals and UE-specific reference signals cannot be simultaneously used; rather, they are time-multiplexed across subframes. A virtual resource block is defined as the same size as a physical resource block. There are two types of virtual resource blocks: virtual resource blocks of localized type; and virtual resource blocks of distributed type. For each type of virtual resource block, a pair of virtual resource blocks over two slots in a subframe is assigned together by a single virtual resource block number NVRB Virtual resource blocks of the localized type are mapped directly to physical resource blocks such that virtual resource block NVRB corresponds to physical resource block NPRB = NVRB. Virtual resource blocks are numbered from 0 to N VRB DL - 1, where NDL VRB = In the localized allocations, there is a one-to-one mapping between virtual and physical resource blocks, whereas in the distributed case of resource allocation, the virtual resource block numbers are mapped to physical resource block numbers 9.15 3GPP LTE physical layer protocols according to the rule specified in reference [107], and inter-slot hopping is utilized. In the latter, the first part of a virtua