6.8 Intra Base Station System intermodulation attenuation
3GPP51.021Base Station System (BSS) equipment specificationRadio aspectsRelease 17TS
6.8.1 Test purpose
To verify that the level of intermodulation products produced inside the RX and TX bands (due to the leakage of RF power between transmitters that are operating in close vicinity of each other inside the BSS, or are combined to feed a single antenna) do not exceed the specified limit. The test is not applicable for GSM 700, GSM 850, MXM 850, PCS 1900 and MXM 1900.
6.8.2 Test case
If SFH is supported by the BSS, it shall be disabled during this measurement.
The BSS shall be configured with a full compliment of transceivers. Each RF transmit equipment shall be operated at the maximum power specified (Highest Static Power Control Level subclause 6.3) and with modulation of a pseudo random sequence applied.
For multicarrier BTS the tests shall be performed per antenna connector for the lowest supported number of carriers (≥ 2) and the declared maximum number of carriers transmitting on equal maximum power according to the power declaration for each configuration.
In the relevant transmit band, the intermodulation components shall be measured at frequency offsets above the uppermost and below the lowermost carrier frequencies.
All intermodulation product frequencies in the relevant TX band and operating RX band shall be identified and measured according to the process below.
For the measurement in the operating RX band
The equipment shall be operated with ARFCNs such that the lowest order intermodulation product falls into the operating receive band. The measurement shall be carried out at the antenna connector of the BSS, using a frequency selective instrument.
A possible measurement set‑up for this test is shown in annex B.2.
For measurements in the RX band the following is the test set up:
A filter and video bandwidth of 100 kHz.
Frequency scan mode.
Minimum sweep time of 75 ms and averaged over 200 sweeps.
For measurements in the relevant TX band
i) For BTSs not belonging to a multicarrier BTS class
The equipment shall be operated at equal and minimum carrier frequency spacing specified for the BSS configuration under test.
For frequency offsets of more than 6 MHz the peak power of any intermodulation components shall be measured with a bandwidth of 300 kHz, zero frequency span, over a time slot period. This shall be measured over sufficient time slots to ensure conformance according to methodology of annex A.1. The reference power for relative measurements is the power measured in a bandwidth of at least 300 kHz for the TRX under test.
For frequency offsets 1.8 MHz or less the intermodulation product power shall be measured selectively using video averaging over 50 to 90 % of the useful part of the time slot excluding the midamble. 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.
For frequency offsets in the range 1.8 to 6 MHz the intermodulation product power shall be measured in a frequency scan mode, with a minimum sweep time of 75 ms and averaged over 200 sweeps. The RF and video filter bandwidth of the measuring instrument shall be 100 kHz.
ii) For BTS belonging to a multicarrier BTS class
The tests are performed according to subclause 6.12.
6.8.3 Void
6.8.4 Conformance requirement
Test Environment
Normal.
Minimum requirement
For measurements in the operating RX band
In the operating receive band the measured intermodulation components shall never exceed the values given in table 6.8-1 under normal test conditions.
Table 6.8-1: Maximum intra‑BSS Receive Band transmitter intermodulation limits
|
GSM 400, GSM 700, GSM 850 and GSM 900, ER-GSM 900 (dBm) |
DCS 1800 and PCS 1900 (dBm) |
|
|
Normal BTS |
‑98 |
‑98 |
|
Micro‑BTS M1 |
‑91 |
‑96 |
|
Micro‑BTS M2 |
‑86 |
‑91 |
|
Micro‑BTS M3 |
‑81 |
‑86 |
|
Pico‑BTS P1 |
‑70 |
‑80 |
|
R‑GSM 900 BTS |
‑89 |
n/a |
|
ER-GSM 900 BTS |
-89 |
n/a |
|
Wide Area multicarrier BTS |
-98 |
-98 |
|
Medium Range multicarrier BTS |
-91 |
-91 |
|
Local Area multicarrier BTS |
-84 |
-84 |
|
NOTE: Micro and pico-BTS is not defined for GSM400. |
||
For measurements in the relevant TX band
i) For BTSs not belonging to a multicarrierBTS class
In the relevant transmit band, at offsets greater than 0.6 MHz and up to 6 MHz, the requirements are those specified in subclause 6.5.1, Continuous Modulation Spectrum. The exceptions given there shall also apply.
At frequencies offset from the wanted signal carrier frequency by more than 6 MHz and up to the edge of the relevant transmit band, the intermodulation components measured shall not exceed ‑70 dBc or ‑36 dBm, whichever is the higher. 1 in 100 time slot periods may fail the requirement by up to 10 dB.
ii) For BTS belonging to a multicarrier BTS class
In the relevant transmit band, the requirements in subclause 6.12.4 apply.
6.8.5 Requirement reference
3GPP TS 45.005 subclause 4.7.2.