About IEEE 802.16 OFDMA Measurements

89601B7RC IEEE Institute of Electrical and Electronics Engineers. A US-based membership organisation that includes engineers, scientists, and students in electronics and related fields. The IEEE developed the 802 series wired and wireless LAN standards. Visit the IEEE at http://www.ieee.org 802.16 OFDMA measurement analysis supports single permutation zone, uplink and downlink subframe data analysis implemented through two measurement analysis modes: uniform zone analysis and data burst analysis:

Uniform Zone Analysis mode performs data analysis for signals that contain a uniform uplink and downlink subframe zone definition.
Data Burst Zone Analysis mode performs uplink and downlink subframe multiple-burst zone analysis (zones definitions containing multiple bursts or data regions).

Topics:

Configuring the VSA (Permutation Zone Definitions)

Measurement TIPS

MIMO Measurements

Configuring the VSA (Permutation Zone Definitions)

Before a OFDMA Enable Burst Analysis mode measurement can be made, the VSA must know the test signal permutation zone definition information. Zone definitions contain the subchannelization information for each data burst (or data region) within the permutation zone. The VSA provides three methods for setting up zone definitions:

"Manual" mode (uses a manually defined zone definition),
"Map Files" mode (uses a predefined zone definition file), or
"Auto" mode (uses an auto-detected zone definition).

Manual mode quickly creates a zone definition and perform a measurement using that definition. Manual mode may be quicker for one-time measurements by eliminating the overhead of creating map file, see Zone Definition Editor. Map Files are stored zone definition configuration files used to automatically set up the VSA for a measurement. The Map File mode easily and repeatably configures the VSA using an existing zone definition map file. This feature allows to create map files manually or automatically using the current measurement in "Auto" mode.. Auto mode makes a measurement without having to pre-configure the VSA zone definition settings. The VSA auto-detects the zone definition information and configures the VSA zone definition settings from the current measurement, see Auto Zone Definition mode). The auto-detected zone definition can be stored as a map file and used over and over to repeat a measurement.

The VSA zone definition settings can be configured using the Zone Definition Editor. The Bursts in Selected Zone list box is located on the "IEEE 802.16 OFDMA IEEE 802.16 OFDMA Demod Properties" dialog box. The data burst signal characteristics (name, data tone modulation, symbol length/offset, etc.) are specified and then the data burst region can be specified by specifying the symbol and subchannel interval and offset values in the Allocation Geometry box. When all the data bursts for the zone have been defined, save the completed zone definition to a map file. A map file contains all the signals uplink and downlink zone definitions for a particular measurement. Zone definition Map Files can be recalled to quickly and repeatable set up the VSA to repeat a measurement. Map files can also be transferred to other users to make similar measurements.

Measurement TIPS

It is recommended that to read the Measurement TIPS information before making an IEEE 802.16 OFDMA measurement. The following information provides VSA setup information and measurement limitations for IEEE 802.16 OFDMA signal analysis.

For IEEE 802.16 OFDMA uplink analysis the defined data burst is assumed to occur simultaneous to when the waveform turns “ON”. If other RF Radio Frequency: A generic term for radio-based technologies, operating between the Low Frequency range (30k Hz) and the Extra High Frequency range (300 GHz). energy is present prior to the data burst, the “Sync Search Offset” property may need to be adjusted to ensure proper synchronization, or the pulse search may be disabled and triggering conditions can be used instead.
Some IEEE 802.16 OFDMA downlink FDD Frequency Division Duplex: A duplex scheme in which uplink and downlink transmissions use different frequencies but are typically simultaneous. signals do not have on-off transitions between frames. To demodulate these signals pulse search (on the Time tab) must be disabled and the start of the frame positioned at the beginning of the acquired time record using external trigger.
Default values are used for DCD downlink channel descriptor: A MAC message that describes the PHY characterstics of a downlink channel. and UCD uplink channel descriptor: A medium access control message that describes the PHY characteristics of an uplink. burst profiles. When using Downlink auto-configuration mode these may need to be modified to ensure correct modulation formats are specified for saved MapFiles, and also to ensure the correct FEC Forward Error Correction: An encoding technique that allows a limited number of errors in digital stream to be corrected based on knowledge of the encoding scheme used. scheme is used for ULMAP decoding. These adjustments are available on the "Burst Profiles" tab of the demod properties dialog. Note if DLMAP decoding is enabled, the DIUC0 value in the parameter table will be ignored and the burst profile detected for DLMAP encoding will be used instead.
Uplink auto-configuration is designed for use with low-noise measurements (specifically transmitter testing situations). If the SNR Signal-to-Noise Ratio is <30dB, some signals may have difficulty using auto-configuration. In this case, manual configuration may be used instead.
Uplink auto-configuration attempts to detect CDMA Code Division Multiple Access: One of several digital wireless transmission methods in which signals are encoded using a specific pseudo-random sequence, or code, to define a communication channel. A receiver, knowing the code, can use it to decode the received signal in the presence of other signals in the channel. This is one of several "spread spectrum" techniques, which allows multiple users to share the same radio frequency spectrum by assigning each active user an unique code. CDMA offers improved spectral efficiency over analog transmission in that it allows for greater frequency reuse. Other characteristics of CDMA systems reduce dropped calls, increase battery life and offer more secure transmission. See also IS-95. region and FFB region geometry. The algorithm assumes a testing profile of Mobile WiMAX which locates the CDMA region starting with the first subchannel of the first slot, and the FFB region located in the remaining subchannels of the first slot, below the CDMA region. For the FFT1024 case this implies 6 subchannels of CDMA followed by 29 subchannelsof FFB region. The algorithm attempts to detect this profile, or an alternate profile with zero CDMA regions or FFB regions. Other configurations may not be detected correctly.
If a RNG burst is present in a CDMA region, the subcarriers may be shown on the traces, but they will not be included in any RCE Relative Constellation Error is the RMS level of the Error Vector Magnitude, averaged over all subcarriers and all detected OFDM symbols. or DataRCEmetrics, unless no other data bursts are available in the measurement. They can be removed from the traces by unselecting the “Include inactive subchannels” checkbox on the Advancedtab of the IEEE 802.16 OFDMA Demod Properties dialog. RNG codes detected as active are listed on the "Data Burst Info" trace, providing code value, power, and location information.
If there is power present in the waveform prior to the active portion of the UL Up Link (reverse link: from cell phone to base station) subframe, the auto-configuration algorithm may fail and present a “DATA?” indicator. If using pulse search, this may be improved by setting the “Manual Sync Search Offset” to a value equivalent to the length of the region between the first turn-on transient of the RF envelope and the start of the ON portion of the subframe. This is typically 1-3 symbols, depending on the configuration of the DUT Device under Test: An acronym used to describe some type of electrical apparatus connected to test instrumentation. The apparatus can range from a single component to a complex subsystem such as a mobile phone, base station or MSC..
When using pulse search and Uplink auto-configuration, the VSA may not be able to determine the location of the analyzed region within the Uplink zone. Because of this, the PRBS Pseudo-Random Binary Sequence seed value (and status results describing specific parameters that compose the PRBS seed value) may be computed for a symbol other than the first symbol in the zone. The possibility of this condition is indicated by a “sym_offset?” annotation presented next to the PRBS status result.
To compute the “Frame Summary” table accumulated metrics -- Mean, Peak, and StdDev -- averaging must be enabled from the MeasSetup > Average menu. The type of averaging does not matter, but the average count is used to compute the exponential weighting values for Mean and StdDevmetrics. The PCINR and RSSI Received signal strength indication metrics implement StdDevmatching the definition in IEEE 802.16-2009. The RCE metrics specify StdDev in dB relative to the Mean value.

MIMO Measurements

To learn about MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. measurements, see MIMO Measurements (802.16 OFDMA).