Agilent Measurement Journal - Issue 4 - 2008 - (Page 25)

To conclude SC-FDMA signal generation, the process follows the same steps as for OFDMA. Performing an inverse FFT converts the frequency-shifted signal to the time domain and inserting the CP provides OFDMA’s fundamental robustness against multipath. If we now return to Figure 2’s representation of OFDMA and SC-FDMA, we can consider how each signal would look depending on the analysis bandwidth. Table 1 summarizes the differences between the modulation formats. When analyzed one subcarrier at a time, OFDMA resembles the original data symbols. At full bandwidth, however, the signal looks like Gaussian noise in terms of its PAR statistics and the constellation. The opposite is true for SC-FDMA. Its relationship to the original data symbols is evident when analyzing the entire signal bandwidth whereupon the constellation (and hence low PAR) of the original data symbols can be observed rotating at N times the SC-FDMA symbol rate (ignoring the seven percent rate reduction due to adding the CP). When analyzed at the subcarrier bandwidth, the SC-FDMA PAR and constellation are meaningless because these are N times narrower than the information bandwidth of the data symbols. Table 1. Analysis of OFDMA and SC-FDMA at different bandwidths Modulation OFDMA format Analysis 15 kHz Signal BW bandwidth (N x 15 kHz) Peak-to-average Same as High PAR power ratio data symbol (Gaussian) Observable Same as Not meaningful IQ data symbol at (Gaussian) constellation 66.7 µs rate SC-FDMA 15 kHz Not meaningful (< data symbol) Not meaningful (< data symbol) Signal BW (N x 15 kHz) Same as data symbol Same as data symbol at N x 66.7 µs rate LTE at a glance November 2004 LTE/SAE High-level requirements • • • • • Reduced cost per bit More lower-cost services with better user experience Flexible use of new and existing frequency bands Simpliﬁed lower-cost network with open interfaces Reduced terminal complexity and reasonable power consumption Flexible channel bandwidths Bandwidth MHz 1.4 3 5 10 15 20 Access mode FDD and TDD FDD and TDD FDD and TDD FDD and TDD FDD and TDD FDD and TDD Speed Downlink peak data rates (64QAM) Antenna conﬁguration SISO 2x2 MIMO Peak data rate (Mbps) 100 172.8 Uplink peak data rates (single antenna) Modulation depth QPSK 16QAM Peak data rate (Mbps) 50 57.6 4x4 MIMO 326.4 64QAM 86.4 The 1.6 MHz and 3.2 MHz TDD bandwidths have recently been deleted, and the six remaining bandwidths apply to both FDD and TDD. Mobility Optimized: 0 to 15 km/h High performance: 15 to 120 km/h Functional: 120 to 350 km/h Under consideration: 350 to 500 km/h Services Packet-switched voice and data. No circuit-switched services supported. Spectral Efﬁciency 3-4x Rel-6 HSDPA (downlink) 2-3x Rel-6 HSUPA (uplink) Latency Idle to active < 100 ms Small packets < 5 ms Agilent Measurement Journal 25

Table of Contents Feed for the Digital Edition of Agilent Measurement Journal - Issue 4 - 2008

Agilent Measurement Journal - Issue 4 - 2008 Delivering Confidence through Compliance with Standards Contents Emerging Innovations Trying Early Device Implementations at the IEEE 1588 PlugFest Achieving Greater Confidence in Measurement Accuracy through Consistency in Calibration Services Overcoming the Challenges of RFID Component Testing 3GPP LTE: Introducing Single- Carrier FDMA Ensuring Reliable Operation and Performance in Converged IP Networks Testing Storage Area Networks and Devices at 8.5-Gb/s Fibre Channel Rates Choosing an Appropriate Calibration Method for Vector Network Analysis Making Traceable EVM Measurements with Digital Oscilloscopes Exploring Terahertz Measurement, Imaging and Spectroscopy: The Electromagnetic Spectrum’s Final Frontier Interpreting Quoted Specifications when Selecting Digitizers

Agilent Measurement Journal - Issue 4 - 2008

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