Resource Allocations (Custom OFDM)
This property is only valid when Resource Interface = Type2.
specifies the allocation ID value mapped to each subcarrier and symbol OFDM Orthogonal Frequency Division Multiplexing: OFDM employs multiple overlapping radio frequency carriers, each operating at a carefully chosen frequency that is Orthogonal to the others, to produce a transmission scheme that supports higher bit rates due to parallel channel operation. OFDM is an alternative tranmission scheme to DSSS and FHSS. Resource Unit (RU RU is an abbreviation for Resource Unit, where one resource unit is a single subcarrier at a single symbol time. The value displayed is the total number of resource units occupied by subcarriers of the specified Resource Type.) in the signal. If N is the number of active Transmitter Antennas, the Resource Allocations array contains N sets of "per RU" (Resource Unit) associated values. Each set of "per RU" values is applied successively to each of the active Transmitter Antennas.
About Resource Allocations
A "resource unit" (RU) is a single subcarrier at a single symbol time. The Resource Allocations array specifies the allocation ID mapped to each of RU comprising the defined signal. If N is the number of active Transmitter Antennas, the number of entries in the Resource Allocations array should be equal to N times the number of subcarriers (FFT Length - Guard Upper Subcarriers - Guard Lower Subcarriers) times the number of symbols to analyze.
Each value in the array represents the allocation ID mapped to a specific resource unit (RU) on a specific active Transmitter Antennas. If no valid allocation ID is mapped to a specific RU, then the corresponding per RU value should be set to -1 value instead. The allocation ID value can then be used to index into the following per Allocation array properties to configure associated information for each allocation.
The frame part ID value for each allocation, can then be used to index into the following per Frame Part array properties to configure associated information for each frame part.
Each data subcarrier type (Resource Type Per Allocation) is detected based on the modulation format (Modulation Per Allocation) assigned to that subcarrier.
Each known pilot subcarrier type (Resource Type Per Allocation) is assumed to have a value specified in the Reference Pilot IQ Values array. Each unknown pilot subcarrier type (Resource Type Per Allocation) is detected, like a data subcarrier, based on the modulation format (Modulation Per Allocation) assigned to that subcarrier. Both pilot and unknown pilot subcarriers are used for pilot tracking.
Each preamble subcarrier is assumed to have a value specified in the Reference Preamble IQ Values array.
Each null subcarrier type (Resource Type Per Allocation) is assumed to be unused and have a nominal signal level of zero.
Each unspecified subcarrier type (Resource Type Per Allocation) is assumed to be completely unknown - it could have some other signal on it so the analyzer makes no assumptions about what value it may have.
The user ID (User ID Per Allocation) allows the subcarriers to be split into logically separate groups for reporting of Data Burst Info "per User" (Name Per User) results.
For subcarriers that have modulation format (Modulation Per Allocation) value of 0 (meaning unknown), each user ID separately determines the modulation format. EVM Error vector magnitude (EVM): A quality metric in digital communication systems. See the EVM metric in the Error Summary Table topic in each demodulator for more information on how EVM is calculated for that modulation format. and power levels are computed separately for each user ID.
MIMO Analysis
The RU allocation's associated active antenna port (Active Ports Per Allocation) mappings are used when doing MIMO Multiple Input, Multiple Output: A physical layer (PHY) configuration in which both transmitter and receiver use multiple antennas. analysis. Valid port index range is between 0 and Transmitter Antennas - 1.
The data and idle subcarrier types (Resource Type Per Allocation) can be mapped to any subset range of the available antenna ports.
The preamble and pilot subcarrier types (Resource Type Per Allocation) can only be mapped to a single antenna port per allocation.
For pilot, unknown pilot, and preamble subcarrier types, if they are mapped to 2 or more unique active ports (Active Ports Per Allocation) for a given RU mapping, then it is assumed that these reference signals are broadcast simultaneously on all antennas using the associated frame part’s configured Code Domain Multiplex (CDM) pattern (defined by CDM Group Subcarrier Count Per Frame Part and CDM Group Symbol Count Per Frame Part property combination).
For known pilot subcarriers, the Reference Pilot IQ Values array can contain values for the pilots on the first antenna, followed by values for the pilots on the second antenna, and so on. Alternatively, if all pilots broadcast the same value on all antennas, then the Reference Pilot IQ Values array need not contain values after the first antenna. Similarly, for preamble subcarriers, the Reference Preamble IQ Values array can contain values for the preambles on the first antenna, followed by values for preambles on the second antenna, and so on. Alternatively, if all preambles broadcast the same value on all antennas, then the Reference Preamble IQ Values array need not contain values after the first antenna.
For pilot, unknown pilot, and preamble subcarrier types, if they are mapped to only 1 unique active ports (Active Ports Per Allocation) for a given RU mapping, then it is assumed that only one transmitter antenna broadcasts this pilot or preamble. For that specific RU, it is assumed that all other antennas broadcast nothing.
If the Resource Allocations array is shorter than the number of used subcarriers times the Result Length, the analyzer will loop back and re-use entries in the array. The Resource Repeat Index property specifies the number of symbols from the start of the array to loop back to.
See Also
