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N9080A LTE FDD and Technical Overview N9082A LTE · PDF file3 Multiple access technology Downlink and uplink transmission in LTE are based on the use of multiple access technologies:

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  • N9080A LTE FDD and N9082A LTE TDD

    Measurement Applications

    Technical Overview with Self-Guided Demonstration

    Agilent X-Series Signal Analyzers (PXA/MXA/EXA)

    N9080A and N9082A LTE measurement applications provide LTE FDD and TDD signal analysis with hardkey/softkey manual

    user interface and familiar SCPI programming.

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    The complexity of LTE systems requires signal analysis with in-depth modulation analysis as well as RF power measurements. The Agilent X-Series signal analyzers (PXA/MXA/EXA), in combination with the N9080A LTE FDD and N9082A LTE TDD measurement applications, measure complex LTE signals with world-class accuracy and repeatability. Its hardkey/softkey manual user interface plus SCPI programming capability is ideal for speedy design validation and/or early manufacturing.

    High-quality modulation analysis measurement for both FDD and TDD frame structure signals according to 3GPP TS 36.211 v 8.6.0 (2009-03) Support for all TDD uplink- downlink configurations (0-6) and special subframe lengths (0-8) Downlink (OFDMA) and uplink (SC-FDMA) measurement capability in a single option All uplink and downlink channels and signals plus all bandwidths and modulation formats Comprehensive transmit signal quality measurements including frequency error, EVM (composite EVM, data EVM, RS EVM), Reference Signal Tx Power (RSTP), OFDM Symbol Transmit Power (OSTP), time alignment between transmitter branches, DL RS power plus more Support for E-UTRA Test Models (E-TMs) for transmit signal quality measurements as well as RF power measurements as defined in 3GPP TS 36.141 V8.2.0 (2009-03)

    One button RF power measurements with pass/fail per 3GPP TS 36.141 V8.2.0 and 3GPP TS 36.521-1 V8.1.0. Measurements including channel power, transmit ON/OFF power (for TDD), ACP, spectrum emission mask (SEM), spurious emissions, occupied bandwidth and more Analysis of Tx diversity encoded signals Analysis of timing and phase offset for both Tx diversity and spatial multiplexing MIMO signals Auto detection of both uplink and downlink signals Flexible measurements let you view your signal in multiple ways: by resource block, sub-carrier, slot, or symbolselect all or a specific region for analysis Color coding by channel type highlights signal errors Add/delete users and edit parameters for each user for realistic testing Support for 3GPP-compliant equalization and EVM minimization The automatic resource block detection or manual user allocation using graphical resource allocation tool simplifies measurement setup Error and frame summary tables provide at-a-glance presentation of key measurement parameters Common tracking error, equalizer frequency, and impulse response let you view the channel from your signals perspective

    Accelerate Your Time to Market with the LTE Measurement Application

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    Multiple access technology

    Downlink and uplink transmission in LTE are based on the use of multiple access technologies: specifically, orthogonal frequency division multiple access (OFDMA) for the downlink, and single-carrier frequency division multiple access (SC-FDMA) for the uplink.

    Transmission bandwidth

    In order to address the international wireless market and regional spectrum regulations, LTE includes varying channel bandwidths selectable from 1.4 to 20 MHz, with sub-carrier spacing of 15 kHz. In the case of multimedia broadcast multicast service (MBMS), a sub-carrier spacing of 7.5 kHz is also possible. Sub-carrier spacing is constant regardless of channel bandwidth. To allow for operation in different sized spectrum allocation, the transmission bandwidth is instead altered by varying the number of OFDM sub-carriers as shown in Table 1.

    Frame structure

    There are two radio frame structures for LTE: frame structure type 1 (FS1) for full duplex and half duplex FDD, and frame structure type 2 (FS2) for TDD. The frame structure for full duplex FDD is shown in Figure 1.

    This structure consists of ten 1 ms sub-frames, each composed of two 0.5 ms slots, for a total duration of 10 ms. The FS1 is the same in the uplink and downlink in terms of frame, sub-frame, and slot duration although the allocation of the physical signals and channels is quite different. Uplink and downlink transmissions are separated in the frequency domain.

    Background Information

    This background information will provide a quick review of some of the physical layer characteristics of an LTE signal. For in-depth LTE technical information, please visit http://www.agilent.com/find/lte

    Transmission bandwidth [MHz] 1.4 3 5 10 15 20

    Number of sub-carriers 72 180 300 600 900 1200

    Table 1. Number of sub-carriers for the different transmission bandwidths

    Figure 1. LTE frame structure type 1 (TS 36.211 V8.6.0)

    One radio frame, Tf = 307200Ts = 10 ms

    One slot, Tslot = 15360 x Ts = 0.5 ms

    One subframe

    #0 #1 #2 #3 #18 #19

    Subframe 0 Subframe 1

    , ,Subframe 9

    ,

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    FS2 is defined for TDD mode. Two switching point periodicities are supported 5 ms and 10 ms, each with an overall length of 10 ms and divided into 10 subframes. The 5 ms switch-point periodicity TDD frame structure is shown in Figure 2.

    For the 5 ms switch-point periodicity case, subframe 6 is a special subframe identical to subframe 1. For the 10 ms switch-point periodicity, subframe 6 is a regular downlink subframe. Table 2 illustrates the possible UL/DL allocations which have been specified in the 3GPP standard for TDD mode.

    As show in Figure 2, the special subframe consists of special fields - downlink pilot timeslot (DwPTS), guard period (GP) and uplink pilot timeslot (UpPTS). Their total length is 1 ms. However, within the special subframe the length of each field may vary depending on co-existence requirement with legacy TDD systems and supported cell size. Table 3 provides the supported special configurations which are also specified in 3GPP.

    Figure 2. Type 2 TDD frame structure with 5 ms switch-point periodicity. (TS 36.211 V8.6.0)

    Table 2. Uplink-downlink confi gurations (TS 36.211 Table 4.2-2)

    Table 3. Confi guration of special subframe length (by Ts unit) (TS 36.211 Table 4.2-1)

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    Resource block

    The smallest time-frequency unit used for transmission is called a resource element, defined as one symbol on one sub-carrier. A group of contiguous sub-carriers and symbols form a resource block (RB). Data is allocated to each user in terms of RBs. For a Type 1 frame structure using normal cyclic prefix (CP), an RB spans 12 consecutive sub-carriers at a sub-carrier spacing of 15 kHz, and seven consecutive symbols over a slot duration of 0.5 ms. Even though an RB is defined as 12 sub-carriers during one 0.5 ms slot, scheduling is carried out on a sub-frame (1 ms) basis. Using normal cyclic prefix, the minimum allocation the base station uses for user equipment (UE) scheduling is 1 sub-frame (14 symbols) by 12 sub-carriers. The size of an RB is the same for all bandwidths, therefore, the number of available physical RBs depends on the transmission bandwidth as shown in Table 4.

    Transmission bandwidth [MHz] 1.4 3 5 10 15 20

    Number of resource blocks 6 15 25 50 75 100

    Number of sub-carriers 72 180 300 600 900 1200

    Table 4. Number of resource blocks (RB) and sub-carriers for the different uplink and downlink transmission bandwidths

    Physical layer channels and signals

    The LTE air interface consists of physical signals and physical channels. Physical signals are generated in Layer 1 and used for system synchronization, cell identification, and radio channel estimation. Physical channels carry data from higher layers including control, scheduling, and user payload.

    Physical signals are summarized in Table 5. In the downlink, primary, and secondary synchronization signals encode the cell identification, allowing the UE to identify and synchronize with the network. In both the downlink and the uplink there are RSs, known as pilot signals in other standards, which are used by the receiver to estimate the amplitude and phase flatness of the received signal.

    DL signals Full name Modulation sequence PurposeP-SS Primary

    synchronization signal

    One of 3 Zadoff-Chu sequences Used for cell search and identifi cation by the UE; carries part of the cell ID (one of 3 orthogonal sequences)

    S-SS Secondary synchronization signal

    Two 31-bit BPSK M-sequence Used for cell search and identifi cation by the UE; carries the remainder of the cell ID (one of 168 binary sequences)

    RS Reference signal (pilot)

    Complex I+jQ pseudo random sequence (length-31 Goldsequence) derived from cell ID

    Used for DL channel estimation; exact sequence derived from cell ID, (one of 3 * 168 = 504)

    UL signals Full name Modulation sequence PurposeDM-RS Demodulation

    reference signalZadoff-Chu Used for synchronization to the UE and UL channel

    estimationS-RS Sounding

    reference signalBased on Zadoff-Chu Used to monitor propagation conditions with UE

    Table 5. LTE physical signals

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    Alongside the physical signals are physical channels, which carry the user and system information. These are summarized in Table 6.

    DL channels Full name

    Modulation format Purpose

    PBCH Physical broadcast channel

    QPSK Carries cell-specifi c information

    PDCCH Physical downlink control channel

    QPSK Scheduling, ACK/NACK

    PDSCH Physical downlink shared channel

    QPSK, 16QAM, 64QAM

    Payload

    PMCH Physical multicast channel

    QPSK, 16QAM, 64QAM

    Payload for multimedia broadcast multicast ser