SR). The CQI informs the scheduler about the current channel conditions as seen by the UE. If MIMO transmission is used, the CQI includes necessary MIMO-related feedback. The HARQ feedback in response to downlink data transmission consists of a single ACK/NAK bit per HARQ process. PUCCH resources for SR and CQI reporting are assigned and can be revoked through RRC signaling. An SR is not necessarily assigned to UEs acquiring synchroniza- tion through the RACH (i.e., synchronized UEs may or may not have a dedicated SR channel). PUCCH resources for SR and CQI are lost when the UE is no longer synchronized [14]. Table 3.3 Supported PUCCH formats Number of bits per PUCCH format Modulation scheme subframe, Mbit QPSK + BPSK QPSK + QPSK Source: C 2009 3GPP [13] 3GPP Evolved Packet System (EPS) Sequence Figure 3.10 Random access preamble format. Reproduced with permission from © 2009 3GPP [13] 3.5.4.1.3 PRACH The physical layer random access preamble, illustrated in Figure 3.10, consists of a cyclic prefix of length Tcp and a sequence part of length TSEQ The random access preambles are generated from Zadoff- Chu sequences with zero correlation zone, ZC-ZCZ, generated from one or several root Zadoff-Chu sequences [14]. The parameter values are listed in Table 3.4 that depend on the frame structure and the random access configuration. The preamble format is controlled by higher layers. Note: For preamble format 4 is only applicable with frame structure type 2 and special subframe configurations with UpPTS lengths 4384 and 5120.Ts. 3.5.4.2 Reference Signals Two types of uplink reference signals are supported: Demodulation reference signal, associated with transmission of PUSCH or PUCCH. Sounding reference signal, not associated with transmission of PUSCH or PUCCH. Uplink reference signals (for channel estimation for coherent demodulation) are transmitted in the 4-th block of the slot (assumed normal CP). The uplink reference signals sequence length equals the size (number of sub-carriers) of the assigned resource. The uplin