The RFmx LTE spectral emission mask (SEM) measurement uses the configurations and masks specified by the 3GPP standard. This topic explains the configurations and masks used by the RFmx LTE Downlink SEM measurement.

Refer to the SEM Overview topic for a general overview of single and multicarrier SEM measurement concepts.

Offset Segments

The offset segments are the channels adjacent to the carrier channels and are specified by their start and stop frequencies (Δf) relative to the nearest edge of the closest E-UTRA carrier. This applies to a single carrier, intraband contiguous, intraband non-contiguous, and multiband operations. The offset segment frequencies, bandwidths, and limits are defined by 3GPP specification.

The power of any offset segment is measured with the measurement filter defined in section 6.6.3 of the 3GPP 36.141 specification. Unlike uplink, the masks of downlink depend on the operating band as well. The masks are defined from a few MHz below the lowest frequency of each supported downlink operating band, up to 10 MHz above the highest frequency of each supported downlink operating band. The limit requirements apply inside any subblock gap and the inside inter-RF bandwidth gap, if any. These cumulative evaluation requirements are not applicable, where the multiple bands are mapped on separate antenna connectors, in such case the requirements of a single band is applied to each of the bands.

The RBW filter for all offset segments are Gaussian, and the resolution bandwidths are set according to the measurement bandwidth defined in 3GPP specification.

According to the 3GPP specification, the resolution bandwidth of the measuring equipment should be equal to the measurement bandwidth. However, to improve the measurement accuracy, sensitivity, and efficiency, the resolution bandwidth the measuring equipment may be smaller than the measurement bandwidth. When the resolution bandwidth is smaller than the measurement bandwidth, the result is integrated over the measurement bandwidth to obtain the equivalent noise bandwidth of the measurement bandwidth.

The measurement improves the resolution of the spectrum by using bandwidth integrals, which specifies the resolution of the spectrum to compare with spectral mask limits as an integer multiple of the RBW filter bandwidth. The measurement acquires the spectrum with a narrow resolution and processes it digitally to get a wider resolution that is equal to the product of the bandwidth integral and the RBW filter bandwidth. When resolutions of the overlapping masks are different, the lowest resolution is used to compute the composite mask.

Masks

The power of any base station (BS) emission must not exceed the levels specified for a mask type for different offset segments. As per the 3GPP specification, the measurement passes if all the offset segments are less than this limit.

The masks are specified based on the eNodeB categories, E-UTRA BS operating band, and Edge carrier bandwidths. The unlicensed TDD band 46 is used for LAA or license assisted operation and is a special case with different test requirements than other bands.

There are few additional requirements mentioned for certain regions and bands defined by 3GPP Specification.

You can choose the SEM Downlink Mask Type property and eNodeB Category property to specify test requirements defined by 3GPP specification.

Home Base Station

Masks for Home Base Station are dependent on the SEM Aggregated Max Pwr property. The aggregated maximum power is defined as the total power of all transmitted antenna ports.

Medium Base Station

The table for masks is selected based on configured SEM CC Max Output Power property as specified by 3GPP specification. The maximum output power is defined as the mean power level per carrier measured at the antenna connector during the transmitter ON period. Masks for Medium Base Station are dependent on measured carrier power(s).

Occasionally, the emission masks may overlap for BS capable of transmitting in multiple bands or multiple subblocks. In such scenarios, the limit mask requirement is defined as a composite emission masks, which is a combination of carriers’ general emissions masks, and is as stated below:

  • Masks within 10 MHz (20 MHz for band 46) from the edges for some frequency out of band, the cumulative sum of the spectral emission masks specified at the edges on each side of the overlap will be applicable. Here, the edge refers to the carrier edge, the subblock edge, or the RF bandwidth edge.
  • Masks beyond 10 MHz (20 MHz for band 46) from the edges for some frequency out of band, the spectrum emission mask with the higher power spectral density applies for these frequencies.

The mask does not apply for frequency, where the sub-block spectrum emission mask overlaps with the sub-block bandwidth of another sub-block. The masks are defined in multiple tables in the section 6.6.3 of 3GPP specification.

For example, the following image shows the carrier channel and the offset channel configurations for DL SEM with two operating bands (X, Y) and three subblocks (A, B, C).

  • Subblock A is comprised of 2 contiguous component carriers (CC-A0 and CC-A1). Subblock B is comprised of 3 contiguous component carriers (CC-B0, CC-B1, and CC-B2). Subblock C is comprised of 2 contiguous component carriers (CC-C0 and CC-C1).
  • Offset segments are denoted as OA and OB.
  • The Δfmax is the frequency separation between the carrier edge or subblock edge (in case of multicarrier) and the nominal -3 dB point of last measurement bandwidth filter.

    Configure the Δfmax using the SEM Delta F_Max property. When you specify the SEM downlink mask type property as Custom, the SEM measurement ignores this parameter.



The cumulative regions are present in the inter subblock gap with a span of 10 MHz. The cumulative region for Band 46 is 20 MHz wide.

  • If the multiple masks belonging to the adjacent subblocks overlap in this region, the sum of PSD of the limits is used for those overlapping frequencies.
  • If the multiple masks belonging to the adjacent subblocks overlap within inter subblock gap but outside cumulative regions, the maximum of the PSD of limits is used for those overlapping frequencies.

All masks are defined with respect to the closest carrier.

If you set the SEM Downlink Mask Type property to Custom, the following parameters are ignored:

  • Delta F_Max (Hz)
  • Aggregated Maximum Power (dBm)
  • Max Output Power (dBm)
  • eNodeB Category