rol/data transmission) that are associated with transmission of PUSCH or PUCCH; and sounding reference signals (located in last symbol of a subframe and which can be configured by the network to support uplink frequency-domain scheduling and channel sounding for downlink transmissions, especially for TDD mode; it uses interleaving in frequency-domain to provide additional support for multiple users transmitting sounding signals in the same bandwidth), which is not associated with transmission of PUSCH or PUCCH. The same set of base sequences is used for demodulation and sounding reference signals. Uplink demodulation reference signals are used for channel estimation in coherent demodulation and are transmitted in the 4th SC-FDMA symbol of the slot assuming normal CP length. The uplink 9.15 3GPP LTE physical layer protocols l = 6 1=0 l = 6 l =0 Even-numbered Slots Odd-numbered Slots Even-numbered Slots Odd-numbered Slots Antenna Port 0 Antenna Port 2 l = 6 l = 0 l = 6 l = 0 Even-numbered Slots Odd-numbered Slots Even-numbered Slots Odd-numbered Slots Antenna Port 1 Antenna Port 3 FIGURE 9-71 Mapping of downlink reference signals, antenna ports 0, 1, 2, and 3 with 4 transmit antennas [107] CHAPTER 9 The IEEE 802.16m Physical Layer (Part I) 1=51=0 1=61=01 Even-numbered Slots Odd-numbered Slots Even-numbered Slots Odd-numbered Slots Antenna Port 4 Antenna Port 5 R7 R7 R8/R8 R7 R7 R7 R7 R8 R8 R8/R8 R7 R7 R8/R8 R8/Rg 1=61=0 1=61=0 Even-numbered Slots Odd-numbered Slots Even-numbered Slots Odd-numbered Slots Antenna Port 8 Antenna Port 7 FIGURE 9-72 Mapping of downlink reference signals, antenna ports 4 (MBSFN), 5, 7, and 8 (UE-specific single-layer and dual- layer transmission) [107] 9.15 3GPP LTE physical layer protocols reference signals' sequence length equals the size (number of sub-carriers) of the assigned resource. The uplink reference signals are based on prime-length Zadoff-Chu sequences that are cyclically extended to the desired length. Multiple reference signals can be created either based on different Zado