LTE Radio Network
This chapter presents the LTE radio interface and related topics. First, an LTE spectrum is described in theory and practice. Then, the LTE multiplex in the downlink and the uplink—that is, OFDM and SC-FDMA—is described. Frequency Division and Time Division variants of LTE are both shown. The LTE link budget is explained with practical examples. The hardware solutions of eNodeB and the antenna systems are explained in detail, as well as practical issues concerning hardware reuse in LTE deployment.
7.2 LTE Radio Interface
The LTE radio interface is based on the frequency division multiplexing technique. Orthogonal Frequency Division Multiplex (OFDMA) is used in the downlink direction whereas Single Carrier Frequency Division Multiple Access (SC-FDMA) is used in the uplink direction. OFDMA provides good protection against the rapidly varying radio conditions, including fast-fading and multi-path propagated radio components. It is not a very efficient solution, though, as the peak-to-average power ratio PAPR behavior causes difficulties in the equipment's circuit design. For that reason, SC-FDMA is selected in the uplink as the terminal can handle these challenges easier .
Long-Term Evolution supports both FDD (Frequency Division Duplex) and TDD (Time Division Duplex). In the FDD mode, the uplink and downlink transmission happens in separate ...