k reference signals are based on prime-length Zadoff-Chu sequences that are cyclically extended to the desired length. The same set of base sequences is used for demodulation and sounding reference signals. Multiple reference signals can be created either based on different Zadoff-Chu sequence from the same set of Zadoff-Chu sequences or from different shifts of the same sequence. 3.5.4.3 Procedures The PHY layers procedures are as follows [14]: Link Adaptation: Uplink link adaptation is used in order to guarantee the required minimum transmis- sion performance of each UE such as the user data rate, packet error rate, and latency, while maximizing the system throughput. Three types of link adaptation are performed according to the channel con- ditions, the UE capability (such as the maximum transmission bandwidth, maximum transmission power, and SO on), and the required QoS (such as the data rate, latency, and packet error rate, and SO on). These three link adaptation methods are Adaptive transmission bandwidth, Transmission power control and Adaptive modulation and channel coding rate. 11 A Zadoff-Chu sequence is a complex-valued mathematical sequence which, when applied to radio signals, gives rise to an electromagnetic signal of constant amplitude, whereby cyclically shifted versions of the sequence comprising the signal do not cross-correlate with each other when the signal is recovered at the receiver. A generated Zadoff-Chu sequence that has not been shifted is known as a root sequence. Next Generation Mobile Communications Ecosystem Table 3.4 Random access preamble parameters Preamble format 3168 Ts 24 576 Ts 21024 Ts 24 576 Ts 6240 Ts 2 24 576 Ts 21024 Ts 2 24 576 Ts 448 Ts 4096 Ts Source: 2009 3GPP [13] Uplink Power Control: The power spectral density of the uplink transmissions can be influenced by the eNB in the case of intra-cell power control. Uplink Timing Control: The timing advance is derived from the UL received timing and sent by the eNB to the UE which the UE uses to advance/delay its timings o