LTE FDD/TDD Signal Analyzer Measurement Guide : LTE Analyzer (Option 883) : LTE UL/DL Interference
 
LTE UL/DL Interference
To select UL/DL interference measurement go to main menu and press MEASURE > MEASUREMENT >UL/DL Interference. The UL/DL Interference measurements are set up using the SETUP Menu (LTE UL/DL Interference). LTE communication systems carry data in frames and sub-frames. The LTE UL/DL Interference measurement provides a power vs. time view of the frame, sub-frames, and slots in an LTE signal. Two types of LTE frame structures are used:
• Type 1 is used in LTE frequency division duplex (FDD) and has an overall length of 10 ms with 10 sub-frames and a total of 20 individual slots. FDD uses different uplink and downlink frequencies.
• Type 2 is used in LTE time division duplex (TDD) and has an overall length of 10 ms with two half frames (each 5 ms long) that are divided into 5 sub-frames (each 1 ms long). TDD uses the same uplink and downlink frequency that is separated in time.
A UL/DL Interference measurement using time domain duplex type is shown in Figure: LTE UL/DL Interference TDD Measurement. The example is showing the complete 10 ms frame power vs. time.
LTE UL/DL Interference TDD Measurement

1. LTE UL/DL Interference Status Panel: Each measurement features a unique status panel that displays settings and information relevant to the current measurement and view settings. This panel provides quick access to the measurement frequency and band configuration. See Status Panel (LTE UL/DL Interference).
2. Gated Spectrum of Uplink/Downlink time slots: Shows trace data of the total frame or sub-frame power measurement in the frequency domain.
3. SETUP Menu: The UL/DL Interference measurement settings are configured in the SETUP menu. See SETUP Menu (LTE UL/DL Interference).
4. PCI SUMMARY: This area shows the physical cell ID, including the sector ID, cell group number, frequency error, time offset, cyclic prefix, and sync status. Sync status can indicate if there is a PSS or SSS failure, a Full Sync, or an Unknown condition. Also noted is the instrument’s reference clock accuracy of Internal, External, or GNSS (GPS) high accuracy (requires GPS).
5. Sub-Frame Power Summary: This area shows the frame power measurement summary data. Power measurements are expressed in dBm.
• The power of each subframe, each of two slots in the subframe, and the total frame power is measured.
• For TDD duplex type, the downlink pilot time slot (DwPTS), uplink pilot time slot (UpPTS), and transmit off power is measured. (see note below)
6. UL/DL Interference vs. Time Display: Shows trace data of the total frame or sub-frame power measurement in the time domain.
Note 
DwPTS carries reference signals, primary synchronization signal, control information, and data.
UpPTS is typically the sounding reference signal transmission from user equipment and is used for the random access channel to setup and synchronize the transmission.
SETUP Menu (LTE UL/DL Interference)
The UL/DL Interference SETUP menu is available in MEASURE > MEASUREMENT > UL/DL Interference > SETUP. Once the UL/DL Interference measurement is selected, the SETUP menu can be quickly accessed by tapping on the summary display area below the trace display.
 
LTE SETUP Menu (UL/DL Interference)
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ANALYSIS
Selects the analysis time of full frame, sub-frame, or individual slot.
SSF CONFIG
Selects the special sub-frame configuration as Auto or one of 10 manual configurations. The slots/sub-frame configuration choices are outlined below:
• 0: 3 downlink, 10 guard period, 1 uplink
• 1: 9 downlink, 4 guard period, 1 uplink
• 2: 0 downlink, 3 guard period, 1 uplink
• 3: 11 downlink, 2 guard period, 1 uplink
• 4: 12 downlink, 1 guard period, 1 uplink
• 5: 3 downlink, 9 guard period, 2 uplink
• 6: 9 downlink, 3 guard period, 2 uplink
• 7: 10 downlink, 2 guard period, 2 uplink
• 8: 11 downlink, 1 guard period, 2 uplink
• 9: 6 downlink, 6 guard period, 2 uplink
SUB-FRAME
Enables limit checking at the specified frequency. The limit test results show as a green PASS or a red FAIL in the measurement table.
SLOT
Selects either slot 0 or slot 1.
ANTENNA
Sets the MIMO antenna number (0 to 3, or AUTO) to use during a measurement. AUTO will use the antenna with the highest received signal power.
GATED SPEC TYPE
Sets the gated spectrum type to uplink, downlink, guard period, all or none. Note that in FDD, only All and None options are available.
GATED DURATION
Sets the gated duration to either Frame or Coupled. If frame is selected all the slots and symbols of the selected gated spec type in the entire frame is measured, whereas if Coupled is selected all the slots and symbols of the selected Gated Spec Type in the selected analysis subframe or slot period is measured.
TIME LEVEL OFFSET
Adjusts the time domain display reference level as an offset from the spectrum reference level. Sets the time level offset in the range from -150 dB to 150 dB.
FRAME START TIME
Choose frame start time from the list of available options:
• Auto: Performs cell search and frame synchronization for every measurement.
• Sync Once: Performs cell search once at the start to obtain frame start time to be used for successive frames.
• UTC: UTC is Coordinated Universal Time. 3GPP specifications refer to UTC for network timing measurements. UTC and GNSS(GPS) time are both derived from the same atomic clocks and for the purposes of 3GPP network measurements can be used interchangeable.Represents a TDD start frame start time which corresponds with the coordinated universal time.
• Custom: Represents a Custom frame time offset value that ranges from -5 ms to 5 ms. ­
 
FRAME TIME OFFSET
Sets the frame time offset, if Custom frame start time is chosen.
CYCLIC PREFIX
Sets the cyclic prefix (or guard time interval) to Normal, Extended, or Auto. The cyclic prefix is a duplication of a fraction of the symbol end. This setting affects the OFDM symbol sensitivity to time dispersion.
DUPLEX TYPE
Selects either frequency division duplex (FDD) or time division duplex (TDD).
UL/DL CONFIG
Available only in TDD duplex type. Sets the uplink/downlink (UL/DL) configuration, or Frame Format. This selection determines which sub-frames are uplink sub-frames and which are downlink sub-frames, and where the transitions between uplink and downlink sub-frames occur.
NG: Selects the NG parameter of 1/6, 1/2, 1, or 2. NG is a parameter that determines the number of PHICH (Physical Hybrid ARQ Indicator Channel) groups in an LTE sub-frame (this number is constant for all sub-frames).
PRESET SETUP
Presets the SETUP menu to default settings.
Status Panel (LTE UL/DL Interference)
The status panel illustrated in this section is unique to the current analyzer and to the particular measurement and view that is selected.
Figure: Status Panel with Minimized Status Panel Icons (LTE UL/DL Interference Measurement) shows the LTE status panel with minimized status panel icons that covers the LTE UL/DL Interference measurement.
Status Panel with Minimized Status Panel Icons (LTE UL/DL Interference Measurement)
 
COLOR LEGEND: Shows the number of uplink and downlink symbols and slots in a transmission period, and their corresponding color designations.
SPEC TRACE TYPE: Selects any one of the trace type such as Normal, Min Hold, Max Hold, Average, Rolling Max Hold, Rolling Min Hold or Rolling Average. Refer to spectrum analyzer measurement guide (10580-00447).
TIME TRACE TYPE: Selects any one of the trace type such as Normal, Min Hold, Max Hold, Average, Rolling Max Hold, Rolling Min Hold or Rolling Average. When set to Normal mode the individual traces show the instant slot power that depends on the data traffic during that time. Set the TIME TRACE TYPE to max hold to see the difference between uplink and downlink slot power.
TIME LEVEL OFFSET
Adjusts the time domain display reference level as an offset from the spectrum reference level. Sets the TIME LEVEL OFFSET in the range from -150 dB to 150 dB. See Figure: Time Trace Type - Max Hold.
MIMO ANTENNAS: Toggles the current MIMO antenna setting between AUTO or to select one of the available antennas. When a single antenna is selected, a blue underscore will appear below the antenna icon. The antenna icon is highlighted green when receiving a signal.
NG: Selects the NG parameter of 1/6, 1/2, 1, or 2. NG is a parameter that determines the number of PHICH (Physical Hybrid ARQ Indicator Channel) groups in an LTE sub-frame (this number is constant for all sub-frames).
SWEEP: Toggles the current sweep setting between continuously or sweep once.
SWEEP ONCE
When sweep is set to single sweep, SWEEP ONCE updates the measurement display. Data continues to be captured in the background.
REF LEVEL
Sets the reference level of the top graticule line in the selected units. If the reference level offset is not zero, OFFSET REF LEVEL is displayed at this location. Refer to Setting Amplitude.
 
 
 
 
SCALE/DIV
Sets the graticule scale/division for log-based units. This setting does not apply to linear units.
CHANNEL BW
Sets the measurement channel bandwidth. The available bandwidth settings depend on the selected band and bandwidth option installed in the instrument.
CENTER FREQUENCY
Sets the center frequency of the measurement channel.
DETECTOR TYPE
Selects one of three detector types. Several detection methods tailor the function of the instrument to meet specific measurement requirements. There are often more measurement points across the screen than display points. The various detection methods are different ways of dealing with how measurement points will be shown at each display point.
• Peak: This method causes the highest amplitude measurement point to be shown for each display point, assuring that a narrow peak is not missed.
• RMS/Avg: In the default case, when the VBW/AVERAGE type is set to Linear, this method detects the average power of measurement points that go into the display point. When VBW/AVERAGE type is set to Log, the traditional average of log (power), such as dBm, is displayed for the detector, as well as for VBW and trace average.
• Negative: This method causes the lowest amplitude measurement point to be shown for each display point. This method is also useful when looking at modulated signals, to see if some frequencies are not being used.
• Sample: Shows the transient amplitude of the center of sampled data for each display point. This method is useful when measuring low-level signals and noise measurements. Only available in zero span and RSSI measurements. When Sample detector is selected, all traces must use sample detection.
• Normal: Shows random noise and signal data depending on the nature of the sampled data. If the signal both rises and falls during the sampling interval (random noise), then odd-numbered sampling intervals display the maximum value and even-numbered sampling intervals display the minimum value. Odd-numbered sampling intervals will display the peak value of the previous even-numbered sampling interval when the peak there is higher. If the signal only rises or only falls during the sampling interval (signal), then only the peak value is displayed, and Normal detection is then equivalent to Peak detection.
ATTEN LEVEL
When auto attenuation is off, sets input attenuation.
PRE AMP
Toggles the low-noise front-end preamplifier on or off. Refer to Setting Amplitude.
TRACES
Displays the current status of up to six traces in a quick-view summary. The summary information includes the trace number, type, mode, and detector type. The active trace will show a highlighted background with the mode and detector type restated under the table. Pressing a trace in the summary panel activates the pressed trace and opens the TRACE menu, which allows you to select and set up an individual trace as desired. Refer to Setting Trace Parameters.
FREQ REFERENCE
Indicates the current frequency reference source of Internal, External, or GNSS (GPS) Hi Accuracy (requires GPS). The instrument automatically selects the frequency reference in the following order of priority: external, GNSS (GPS), then the internal time base.
 
Time Trace Type - Max Hold