6.12 Wideband noise and intra BSS intermodulation attenuation in multicarrier operation

3GPP51.021Base Station System (BSS) equipment specificationRadio aspectsRelease 17TS

6.12.1 Test purpose

To verify that the level of wideband noise and intermodulation products produced inside the relevant TX bands for a BTS belonging to a multicarrier BTS class do not exceed the specified limit when multiple carriers are active. The test is not applicable for MXM 850 and MXM 1900.

6.12.2 Test case

If SFH is supported by the BSS, it shall be disabled during this measurement.

a) The tests shall be performed per antenna connector for the declared maximum number of carriers transmitting on equal maximum power according to the power declaration. In addition the test shall be performed for the test case with unequal power distribution according to subclause 4.10.10 for the declared maximum number of carriers.
The equipment shall be operated at minimum carrier frequency spacing specified for the BSS configuration under test. The test is performed for carriers located around M.

b) The multicarrier BTS shall be configured to operate with the lowest supported numbers of carriers (≥ 2) and the declared maximum number of carriers transmitting on equal maximum power according to the power declaration for each configuration and distributed as described below over the corresponding declared maximum Base Station RF bandwidth, configured to include B. The test is repeated in a configuration where maximum Base Station RF bandwidth includes T.
In addition, if no third order intermodulation product at any of these configurations can occur outside the group of carriers and within the relevant TX band or the maximum Transmit Filter bandwidth, whichever is smallest, the carrier frequency spacings shall be equally reduced until one of the third order intermodulation product closest to the group of carriers occurs on one of the band edges of the applicable bandwidth, and the test is repeated. When reducing the spacings, both carrier frequency configurations shall be tested for the two cases: one where the lowest frequency is kept at B and as close as possible to the lower band edge and one where the highest frequency is kept at T and as close as possible to the upper band edge of the relevant transmit band.

c) If the multicarrier BTS equipment according to the vendor declaration supports non-contiguous frequency allocation as defined in subclause 4.10.10 and four or more carriers, tests shall be performed per antenna connector with maximum number of carriers as equally as possible distributed between two sub-blocks, each with a sub-block edge at the edge of the maximum Base Station RF bandwidth. The sub-blocks are located around M, with a sub-block gap of at least 5 MHz and sub-block bandwidth according to table 6.12-1. The carriers shall be operating at equal declared maximum power for this configuration.

Table 6.12-1: Sub-block bandwidth for non-contiguous frequency allocation

Maximum number of carriers

Sub-block bandwidth [MHz]

Maximum possible equal frequency spacing (Deq) [MHz]

4

4

3.6

5-6

4

1.8

7-8

4

1.2

9-10

4.4

1

11-12

4.4

0.8

13-14

5.2

0.8

15-16

6

0.8

For every further increase of 2 more maximum number of carriers, the sub-block bandwidth is increased by 0.8 MHz while Deq remains 0.8 MHz.

To distribute the carriers in test case b) and within a sub-block in test case c), the difference between adjacent carrier spacings, between the carrier center frequencies, shall be maximum ±200kHz and the third order IM products, generated by any combination of two or three frequencies, shall coincide within 400 kHz, measured at the center frequencies of the IM products. Any combination fulfilling these criteria can be used, but the same carrier frequency configuration shall be used when B or T respectively is included in the measurement.
The following procedure applies in test case b):

1 Calculate the maximum possible equal frequency spacing (Deq) within the declared maximum Base Station RF bandwidth (RF-BWmax). Note that the center frequencies of the outermost carriers shall be 200 kHz inside the band edges of RF-BWmax and that Deq is a multiple of 200 kHz.

2 Allocate one carrier at lowest and one at highest frequency possible within the RF-BWmax.

3 Allocate the remaining carriers at frequencies shifted from one of the outermost carriers by a multiple of Deq with altering offsets. These offsets may be chosen freely to be either 0, + 200 kHz or – 200 kHz but the difference between two adjacent spacings shall be no more than 200 kHz. It is not allowed to set all offsets to 0. In addition the IM spread limits (IM3 to coincide within 400 kHz) shall be fulfilled.

As an exception, if above conditions cannot be fulfilled, the frequency spacing between the outermost carriers defined in step 2 is reduced by 200 kHz through either reallocation of the uppermost carrier if B is included in the measurement or reallocation of the lowermost carrier if T is included in the measurement.

The following procedure applies in test case c):

1 Note the maximum possible equal frequency spacing (Deq) from table 6.12-1.

2 In each sub-block, allocate one carrier at lowest and one at highest frequency possible within the sub-block bandwidth.

3 Allocate the remaining carriers of each sub-block at frequencies shifted from the outermost carriers of each sub-block by a multiple of Deq with altering offsets. If the number of carriers in the two sub-blocks is unequal, one multiple of Deq will need to be unoccupied in the sub-block with fewer carriers. The offsets may be chosen freely to be either 0, + 200 kHz or – 200 kHz but the difference between two adjacent spacings shall be no more than 200 kHz.

As an exception if above conditions cannot be fulfilled, the procedure may be modified:

i) Above procedure may be used with a smaller sub-block bandwidth if the maximum Base Station RF bandwidth is not sufficient, with the maximum possible equal frequency spacing (Deq) being the next lower multiple of 200 kHz.

ii) If i) is not sufficient, above procedure may be used with minimum carrier spacing if the maximum Base Station RF bandwidth is not sufficient. In that case altering offsets shall not be used, as described in step 3.

iii) If i) or ii) is not sufficient, above procedure may be used when declaring a lower maximum number of carriers for non-contiguous frequency allocation.

For frequency offsets from the centre frequency of the uppermost and lowermost active carrier of more than 6 MHz the average power shall be measured over sufficient time slots to ensure conformance according to methodology of annex A.1.

– Within a 600 kHz band centered at the centre frequencies of the intermodulation components the measurements shall be performed with the center frequencies of the measurement bandwidth in the frequency band ± 150 kHz around the centre frequencies of the intermodulation components, using a measurement bandwidth of 300 kHz. The reference power for relative measurements shall be the power measured in a bandwidth of 300 kHz for one of the carriers under test.

– For offsets outside the 600 kHz bands around the centre frequencies of the intermodulation components, the measurements shall be performed with the center frequencies of the measurement bandwidth starting at ± 350 kHz around the centre frequencies of the intermodulation components, using a measurement bandwidth of 100 kHz. The reference power for relative measurements in a bandwidth of 30 kHz for one of the carriers under test.

For frequency offsets from the centre frequency of the uppermost and lowermost active carrier of1.8 MHz up to and including 6 MHz the average power shall be measured in a frequency scan mode, with a minimum sweep time of 75 ms and averaged over 200 sweeps.

– Within a 600 kHz band centered at the centre frequencies of the intermodulation components , the measurements shall be performed with the center frequencies of the measurement bandwidth in the frequency band ± 250 kHz around the centre frequencies of the intermodulation components, using a RF and video filter bandwidth of the measuring instrument of 100 kHz. The reference power for relative measurements shall be the power measured in a bandwidth of 100 kHz for one of the carriers under test.

– For offsets outside the 600 kHz bands around the centre frequencies of the intermodulation components, the measurements shall be performed with the center frequencies of the measurement bandwidth starting at ± 350 kHz around the centre frequencies of the intermodulation components, using a measurement bandwidth of 100 kHz. The reference power for relative measurements shall be the power measured in a bandwidth of 30 kHz for one of the carriers under test.

For frequency offsets from the centre frequency of the uppermost and lowermost active carrier of less than 1.8 MHz the average power shall be measured selectively using video averaging over 50 to 90 % of the useful part of the time slot excluding the mid‑amble. The averaging shall be over at least 200 time slots and only active bursts shall be included in the averaging process. The RF and video filter bandwidth of the measuring instrument shall be 30 kHz. The reference power for relative measurements shall be the power measured in a bandwidth of 30 kHz for one of the carriers under test.

The measurement conditions for the Continuous Modulation Spectrum regarding frequency offsets and detector settings shall be the same as defined in subclause 6.5.1 for multicarrier BTS.

6.12.3 Void

6.12.4 Conformance requirement

Test Environment

Normal.

Minimum requirement

For multicarrier BTS when more than one carrier is active, in the relevant transmit band, the unwanted emission power shall be measured at offsets between 0.4 MHz from the uppermost and lowermost wanted signal carrier frequency and 10 MHz outside the edge of the relevant transmit band.

At frequency offsets higher than or equal to 1.8 MHz from the centre frequency of the uppermost and lowermost active carrier up to 10 MHz outside the edge of the relevant transmit band, the unwanted emission for the multicarrier BTS shall not exceed the less stringent of the following requirements:

– in a frequency band of 600 kHz centered at the centre frequencies of the intermodulation components, the average power measured over a timeslot shall not exceed -70 dBc or the limit in table 6.12-2, whichever is less stringent.

Table 6.12-2 Intermodulation lower limit

Maximum output power
per carrier

Intermodulation
power

> 33 dBm

-36 dBm

> 24 dBm
and ≤ 33 dBm

-41 dBm

≤ 24 dBm

-46 dBm

– in addition, in a frequency band of 600 kHz centered at the third order intermodulation centre frequencies, the average power of the measured intermodulation components over a timeslot may increase up to -60 dBc.

– the requirements specified in subclause 6.5.1, Continuous Modulation Spectrum, increased by 10*LOG(N) dB where N is the number of active carriers. The dBc value specified in table 6.5-1 for the frequency offset of the centre frequency of the closest carrier to the measurement frequency point must be reduced by 5 dB to account for the bandwidth conversion from 100 kHz to 30 kHz.

In order to prove the compliance with the intermodulation requirements, the power of all third and fifth order intermodulation products shall be measured.

In the test case with unequal power distribution, the reference for the relative requirements is the power of the carrier with the highest power applied.

At frequency offsets of less than 1.8 MHz from the outermost carriers, the unwanted emissions must fulfil a mask that is defined in the following steps:

1) The dBc values of table 6.5-1 in subclause 6.5.1 (Aj with j=1 to N) are extracted for each carrier, taking into account the output power level of one carrier and the corresponding frequency offset between the measurement frequency point and the respective carrier. For carriers at offsets above 1.8 MHz from the measurement frequency point, the dBc value for the respective carrier must be reduced by 5 dB to account for the bandwidth conversion from 100 kHz to 30 kHz.

2) The dBc value (Aj with j=N+1) of the IM attenuation defined in sub-clause 6.12 for the multicarrier BTS has to be derived. In some configurations there might be no IM product falling onto the respective frequency. Then this contribution is ignored in the following.

3) The obtained N+1 dBc values are cumulated in the (following way) linear domain:

.

4) This procedure has to be done for the following frequency offsets above the uppermost and below the lowermost carriers: 400 kHz, 600 kHz and 1200 kHz.

5) For each of these measurement frequency points, the measured spectrum must not exceed the respective unwanted emission mask defined by Acumulated, dBc.

For test case c) the requirements above the uppermost carrier and below the lowermost carrier are the same as specified above with N being the total number of active carriers. In addition the test includes the measurement of the frequency range between the innermost carriers of the two sub-blocks, where the following requirements apply:

– For frequency offsets of less than 1.8 MHz above the centre frequency of the uppermost carrier A of the lower sub-block or below the centre frequency of the lowermost carrier B of the upper sub-block, the unwanted emission must not exceed a mask defined by the cumulation of the spectrum due to modulation and wideband noise from each of the N carriers and the IM products, as specified above in this subclause for frequency offsets of less than 1.8 MHz for the test of contiguous carrier allocations.

– For frequency offsets of equal or larger than 1.8 MHz above the centre frequency of the uppermost carrier A of the lower sub-block and for frequency offsets of equal or larger than 1.8 MHz below the centre frequency of the lowermost carrier B of the upper sub-block: the value of the spectrum due to modulation and wideband noise given for the measurement of carrier A or carrier B, whichever closest, may not increase by more than 10*LOG (N) dB, or fulfil the requirement given above for multicarrier BTS for frequencies where IM products are expected, whichever is the less stringent.

NOTE: The cumulated IM products are represented by respective Intra BSS intermodulation attenuation requirement, regardless if IM products originate from either or both sub-blocks.

The absolute lower limit in item 4) in subclause 6.5.1.3.2 shall apply for all numbers N of active carriers.

At offsets between 600 kHz above the uppermost and below the lowermost carrier, respectively, and 10 MHz outside the relevant transmit band, in bands of 200 kHz width centered on a frequency, which is an integer multiple of 200 kHz, in test case a) and b) exceptions are allowed for N active carriers at M= 18 + 3* (N-1) or up to 40 bands, whichever the lowest. All exceptions are measured in 100 kHz bandwidth, averaged over the 200 kHz band and may be up to the limit in table 6.12-3. In addition, all exceptions within the relevant transmit band and up to four exceptions at offsets up to 2 MHz from the respective band edges, may be up to -70 dBc relative to the carrier measured in a bandwidth of 100 kHz, or limit in table 6.12-3, whichever less stringent. For test case c) the same total number of exceptions M for N active carriers shall apply as given above for test case a) , including the range of frequency offsets between 0.6 MHz above the uppermost carrier of the lower sub-block and 0.6 MHz below the lowermost carrier of the upper sub-block. The 200 kHz bands, which centre frequency coincides with the centre frequency of third order IM products of any combination of two or three active carriers and corresponding adjacent channels (±200 kHz), shall not be included in counting the exceptions.

Table 6.12-3 Exception power level for wideband noise

Multicarrier BTS class

Exception level

Wide Area

-36 dBm

Medium Range

-42 dBm

Local Area

-50 dBm

6.12.5 Requirement reference

3GPP TS 45.005 subclauses 4.2.1 and 4.7.2.