Intentional Emissions Test Cases
1. Effective Isotropic Radiated Power (EIRP)
- The measurements for RF output power shall be performed at both normal environmental conditions and at the extremes of the operating temperature range.
- The measurement shall be performed at the lowest, the middle, and the highest channel on which the equipment can operate.
- The RMS power is measured through an RF power sensor with sample speed and specifications as mentioned by the respective standards.
- The RF output power must be measured when Equipment Under Test (EUT) is transmitting at 100% duty cycle, if a lower duty cycle is used then the duty cycle factor will be added to the measured RF output power.
P = A + G + Y + 10 × log10 (1 / X) (dBm), where
P = Calculated final RF output power in dBm
A = Measured RF power in dBm with path loss compensated
G = Antenna gain in dBi
Y = Beamforming gain in dBi
X = Duty cycle
- In the case of conducted measurements on smart antenna systems operating in a mode with multiple transmit chains active simultaneously, the output power of each transmit chain will be measured separately to calculate the total power for the UUT.
- In the case of equipment intended for use with an integral antenna and where no antenna connectors are provided, a test fixture can be used, for NFC and RFID devices electric and magnetic field probes will be used to find the electric and field strengths.
2. Power Spectral Density (PSD)
Density is a measure of how much mass is contained in a given volume.
Power Spectral Density (PSD) is a measure of how power (or variance) of a signal is distributed with frequency. It provides insight into the frequency components of a signal and how the power of the signal is distributed across those frequencies.
PSD is expressed as power per unit frequency (e.g., watts per hertz, W/Hz).
The Power Spectral Density (PSD) is the mean equivalent isotropically radiated power (e.i.r.p.) spectral density in a specified bandwidth during a transmission burst.
- These measurements shall only be performed in normal test conditions.
- The measurement shall be repeated for the equipment being configured to operate at the lowest, the middle, and the highest frequency of the stated frequency range.
- The transmitter shall be connected to a spectrum analyzer which shall be configured as per the standard to measure the power associated with a specified resolution bandwidth of frequency.
3. Duty Cycle
Duty cycle refers to the percentage of one period in which a signal or system is active. It is commonly used to describe the fraction of time a system, such as an electrical device or a wireless transmitter, spends in an active state versus an idle state within each cycle.
Duty Cycle is defined as the ratio of the total transmitter 'on'-time to a total observation period.
- These measurements shall only be performed in normal test conditions.
- The transmitter shall be connected to a spectrum analyzer which shall be configured as per the standard in zero span mode (time domain) to calculate the transmitter on and off period in a cycle to calculate the duty cycle.
4. Frequency Hopping
A hopping frequency is considered to be occupied when the equipment selects that frequency from the Hopping Sequence.
FHSS equipment may be transmitting, receiving or stay idle during the dwell time spent on that hopping frequency.
- Test case is applicable only for equipment operating in Frequency Hopping Spread Spectrum (FHSS).
- The transmitter shall be connected to a spectrum analyzer which shall be configured as per the standard.
- Accumulated transmit time is measured in zero span mode in the time domain while frequency occupation and hopping sequence will be measured in frequency domain with specified resolution bandwidth.
5. Adaptivity
Energy Detect (ED) Threshold: The device continuously monitors the energy level on the channel to detect any interfering signals. The ED threshold determines the sensitivity of the radio to these signals
Energy Detection Threshold for 2.4GHz
TL = -70 dBm/MHz + 10 × log10 (100 mW / Pout) (Pout in mW e.i.r.p.)
Energy Detection Threshold for 5GHz
Energy Detection Threshold for 6GHz
The total time during which an equipment has transmissions on a given hopping frequency without re-evaluating the availability of that hopping frequency is defined as the Channel Occupancy Time.
Clear Channel Assessment (CCA) is a mechanism used in wireless communication to determine whether a communication channel is free for transmission. It's a key part of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) protocol, which helps prevent data collisions in a network.
There are two types of channel access mechanisms categorized as Frame Based Equipment (FBE) and Load Based Equipment (LBE).
The device using Quality of Service (QoS) based on the access category of traffic are classified as Load Based Equipment (LBE).
Frame Based Equipment (FBE) uses Distributed Inter-Frame Spacing (DIFS) mechanism, which is a non QoS feature. Whereas Load Based Equipment (LBE) uses Arbitrary Inter-Frame Spacing mechanism (AIFS).
Frame Based Equipment (FBE) uses a single channel access engine whereas Load Based Equipment (LBE) uses four channel access engines based on the four types of traffic access categories (Voice, Video, Best-Effort and Background).
DIFS = SIFS + 2 x Slot Time
AIFS = SIFS + Slot Time x CWmin
Priority class dependent channel access parameters for supervising devices (AP) | ||||||
Priority Class | Access Category | Description | Prioritization Period (Back-off Counter) | Contention-Window minimum (CWmin) | Contention-Window maximum (CWmax) | Maximum Channel Occupancy Time (ms) |
4 | AC_VO | Voice (highest priority) | 1 | 3 | 7 | 2 |
3 | AC_VI | Video | 1 | 7 | 15 | 4 |
2 | AC_BE | Best Effort | 3 | 15 | 63 | 6 |
1 | AC_BK | Background (lowest priority) | 7 | 15 | 1023 | 6 |
Priority class dependent channel access parameters for supervised devices (STA) | ||||||
Priority Class | Access Category | Description | Prioritization Period (Back-off Counter) | Contention-Window minimum (CWmin) | Contention-Window maximum (CWmax) | Maximum Channel Occupancy Time (ms) |
4 | AC_VO | Voice (highest priority) | 2 | 3 | 7 | 2 |
3 | AC_VI | Video | 2 | 7 | 15 | 4 |
2 | AC_BE | Best Effort | 3 | 15 | 1023 | 6 |
1 | AC_BK | Background (lowest priority) | 7 | 15 | 1023 | 6 |
Medium Utilization (MU) factor
The Medium Utilization (MU) factor is a measure to quantify the number of resources (Power and Time) used by non-adaptive equipment. The Medium Utilization factor is defined by the formula:
MU = (Pout / 100 mW) × DC
where: MU is Medium Utilization.
Pout is the RF output power expressed in mW.
DC is the Duty Cycle expressed in %.
Channel Access Mechanism (LBE):
- Load Based Equipment (LBE) can operate up to 4 channel access engines, each with a different priority class.
- Before a transmission or a burst of transmissions on a channel or group of adjacent or non-adjacent channels, the initiating device shall operate at least one channel access engine to sense the RF energy and to perform Clear Channel Assessment (CCA).
- The channel access engine shall set CW to CWmin to select a random number q from a uniform distribution over the range 0 to CWmin and shall set the prioritization period according to the priority class and wait for a period of at least 14 µs to perform to perform Clear Channel Assessment (CCA).
- During a single observation slot the channel access engine shall determine if the channel or combination of channels are occupied channel(s). For the channel(s) that have been detected as occupied, the channel access engine shall initiate a new prioritization period and for r the channels that have been determined as unoccupied channels the prioritization period will be decremented by 1 for each time slot and once it reaches 0, back off procedure will be performed based on the contention window value.
- During the contention window period, the channel access engine shall perform a CCA on the channel. During a single observation slot the channel access engine shall determine if the channel or combination of channels are occupied channel(s) or unoccupied channel(s) same as the channel availability assessment done during the prioritization period. For the channel(s) that have been determined as occupied channel(s), the channel access engine set new prioritization period and starts the assessment from the beginning and for channel(s) that have been detected as unoccupied channel(s) the contention window value will be decremented by 1 for each time slot and once it reaches 0, the channel access engine is ready for a transmission.
- The channel access engine may start transmissions belonging to the corresponding or higher priority classes, on one or more channels to avoid internal collisions. The channel access engine may grant up to ten authorizations to transmit on the current channel to each of one or more responding devices providing the gap in between such transmissions does not exceed 18 µs for FBE and 27 µs for LBE.
- During the back-off stage when the channel is busy, FBE and LBE are allowed to have Short Control Signaling (SCS) transmissions on the channel to send management and control frames without sensing the channel for the presence of other signals.
- The UUT shall connect to a companion device during the test with a unidirectional traffic source based on a specific priority class. The signal generator, the spectrum analyzer, the UUT, the traffic source and the companion device are connected using a set up equivalent to the above figure. The spectrum analyzer is used to monitor the transmissions of the UUT in response to the interference signal. The traffic source might be part of the UUT itself.
- The received signal level (wanted signal from the companion device) at the UUT shall be sufficient to maintain a reliable link for the duration of the test. A typical value for the received signal level which can be used in most cases is -50 dBm/MHz.
- The spectrum analyzer settings shall be done as per the standards in zero span (time domain) mode.
- An interference signal (Additive White Gaussian Noise (AWGN) test signal, OFDM test signal 1 and OFDM test signal 2) as defined by the standard is injected on the current channel of the UUT with a power level equal to applicable Energy Detection Threshold (EDT).
- The spectrum analyzer shall be used to monitor the transmissions of the UUT on the selected channel after the interference signal was injected. Apart from Short Control Signal (SCS) transmissions there are no subsequent transmissions while the interfering signal is present.
- To verify that the UUT is not resuming normal transmissions as long as the interference signal is present, the monitoring time may need to be 60 s or more. Once the test is completed and the interference signal is removed, the UUT may start transmissions again on this channel.
- For measuring idle or silent periods, count the number of consecutive data points identified as resulting from a single transmitter off period on the channel being investigated and multiply this number by the time difference between two consecutive data points.
6. Occupied Channel Bandwidth and Frequency Error
The occupied channel bandwidth is the bandwidth within the nominal channel bandwidth containing 99 % of the power of the signal.
Frequency error is the difference between the nominal channel center frequency and the actual channel center frequency.
- The measurement shall be performed on the lowest and the highest Operating Frequencies within the stated frequency range.
- If the equipment can operate with different Nominal Channel Bandwidths (e.g. 20 MHz and 40 MHz), then each channel bandwidth shall be tested separately.
- EUT is connected to the spectrum analyzer and the analyzer settings are configured as the standard in frequency domain mode to capture the frequency bandwidth occupied during normal operation.
- The 99 % occupied bandwidth function of the spectrum analyzer shall be used to measure the occupied bandwidth of the signal.
7. Unwanted Emissions
Transmitter unwanted emissions in the spurious domain are emissions outside of the operating band and outside of the out-of-band domain when the equipment is in transmit mode.
Receiver spurious emissions are emissions at any frequency when the equipment is in receive mode.
- The measurement shall be performed at the lowest and the highest channel on which the equipment can operate.
- The equipment shall be configured to operate in its worst-case situation with respect to output power.
- If the equipment can operate with different Nominal Channel Bandwidths (e.g. 20 MHz and 40 MHz), then each channel bandwidth shall be tested separately.
- The applicable mask for out of band emissions is defined by the occupied channel bandwidth.
- Transmitter and receiver spurious emissions must be performed both in conducted mode and in radiated mode.
- Pre-scans and final scans will be performed with different receiver settings as defined by the standards and different antennas will be used for different frequency range coverage.
Frequency Range (MHz)
Antenna Used
FCC
ETSI
0.009 to 30
Loop
Loop
30 to 300
Bi-conical
Bi-log periodic
300 to 1000
Log periodic
Bi-log periodic
1000 to 40000
Horn
Horn
8. Receiver Blocking and Receiver Selectivity
Receiver blocking is a measure of the capability of the equipment to receive a wanted signal on its usable channels without exceeding a given degradation due to the presence of an unwanted input signal (blocking signal) on frequencies other than those of the operating bands.
Receiver selectivity is a measure of the capability of the equipment to receive a wanted signal on its channel without exceeding a given degradation due to the presence of an interfering signal in an adjacent channel or alternate adjacent channel within the operating band.
- The measurements shall only be performed in the normal test conditions.
- If the equipment can be configured to operate with different Nominal Channel Bandwidths (e.g. 20 MHz and 40 MHz) and different data rates, then the combination of the smallest channel bandwidth and the lowest data rate for this channel bandwidth which still allows the equipment to operate as intended shall be used.
- The Equipment Under Test (EUT) shall be connected to the companion device in a mode where the data packets transmission and reception shall be monitored to measure the minimum performance criteria. The physical connection for the test validation is as per the figure above.
- The attenuation of the variable attenuator shall be increased in 1 dB steps to a value at which the minimum performance criteria with packet error rate less than or equal to 10 %. The resulting level for the wanted signal measured at the interface between the UUT and its antenna assembly is Pmin.
- This signal level (Pmin) shall be increased by 6 dB resulting in a new level (Pmin + 6 dB) of the wanted signal at the UUT receiver input.
- The level of the blocking signal measured at the interface between the EUT and its antenna assembly shall be set to the level as specified by the standard and whether the performance criteria is met or not met when the blocking signal is injected.
9. Dynamic Frequency Selection (DFS)
Dynamic Frequency Selection (DFS) is a channel allocation scheme used in wireless LANs (Wi-Fi) to avoid interference with other systems, such as radar and satellite communications.
Radar detection shall be used when operating on channels whose nominal channel bandwidth falls partly or completely within the 5 GHz DFS band. The 5 GHz DFS band covers sub-band 2 (UNII-2A = 5.25 to 5.35 GHz) and sub-band 3 (UNII-2C = 5.47 to 5.725 GHz).
Channel Availability Check (CAC) is the process by which an RLAN device checks channels for the presence of radar signals.
Off-Channel Channel Availability Check is a technique used in wireless communication systems in which device periodically tunes its radio to a different channel to scan for radar signals. This scanning is done while the device is still operating on its current channel.
In-service monitoring is the process by which a Radio LAN device monitors each operating channel for the presence of radar signals. In-service monitoring shall start immediately after the Radio LAN device has started transmissions on a channel.
Channel shutdown is the process initiated by the Radio LAN device on an operating channel after a radar signal has been detected during in-service monitoring.
The primary device shall instruct all associated secondary devices to stop transmitting on this operating channel, which they shall do within the channel move time. The primary device shall also stop its own transmissions on that operating channel within the channel move time.
Non-occupancy period is the time during which the Radio LAN device does not transmit on a channel after a radar signal was detected on that channel.
For equipment having simultaneous transmissions on multiple (adjacent or non-adjacent) operating channels, only the channel(s) containing the frequency on which radar was detected is (are) subject to the non-occupancy period requirement. The equipment is allowed to continue transmissions on other operating channels.
Before the RLAN device may transmit on a channel after the non-occupancy period ended, the channel shall be again identified as an available channel.
Uniform spreading is a mechanism used to provide, on aggregate, a uniform loading of the spectrum across all devices.
The spreading can be achieved by various means. These means include network management functions controlling large numbers of RLAN devices as well as the channel selection function in an individual RLAN device.
Each of the channel plans shall make use of at least 60 % of the spectrum available in each band. Each of the usable channels shall be used with approximately equal probability.
Within the context of the operation of the DFS function, an RLAN device shall operate as either a primary device or a secondary device. RLAN devices operating as a secondary device shall only operate in a network controlled by an RLAN device operating as a primary device. A device which is capable of operating as either a primary device or a secondary device shall conform to the requirements applicable to the mode in which it operates.
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