7.7 Intermodulation characteristics
3GPP51.021Base Station System (BSS) equipment specificationRadio aspectsRelease 17TS
7.7.1 Test Purpose
This test measures the linearity of the receiver RF parts. It expresses the capability of the receiver to receive a wanted modulated signal without exceeding a given degradation due to the presence of two or more unwanted signals with a specific frequency relationship to the wanted signal frequency.
7.7.2 Test Case
If SFH is supported by the BSS, it shall be disabled during this measurement. The measurement is performed only under static conditions. The measurement shall be performed for the radio frequency channels B, M and T and for the supported channels in table 7.7-1. As a minimum, one time slot shall be tested on one TRX to be tested.
Three signals shall be applied to the receiver via a combining network. The powers of the signals are measured at the receiver antenna connector.
The wanted signal shall have a power level as defined in table 7.7-1. Only wanted signals with BTTI and no PAN need to be tested.
The second signal is an interfering signal, GMSK modulated by a pseudo‑random bit sequence, and shall be 1.6 MHz above the wanted signal frequency. During the useful part of the burst of the wanted signal, the modulation of this interfering signal shall be any 148‑bits subsequent of the 511‑bits sequence, defined in CCITT Recommendation O.153 fascicle IV.4., and the power shall be ‑43 dBm for GSM 400, GSM 700, GSM 900, ER-GSM 900, GSM 850 and MXM 850 and ‑49 dBm for DCS 1800, PCS 1900 and MXM 1900.
NOTE: This signal can be a continuous signal modulated by the 511‑bits sequence.
The third signal is an interfering signal and shall be unmodulated. It shall be 800 kHz above the wanted signal frequency, and the power shall be ‑43 dBm for GSM 400, GSM 700, GSM 900, ER-GSM 900, GSM 850 and MXM 850 and ‑49 dBm for DCS 1800, PCS 1900 and MXM 1900.
The various signals are illustrated in figure 7.7-1.
In case of a multicarrier BTS with multicarrier receiver, the two interfering signal levels shall be adjusted by 0 dB, [+2] dB and [+5] dB, for the Wide Area, Medium Range and Local Area classes, respectively.
If BSS supports both EGPRS and ECSD, it is not necessary to perform testing in both modes. If ECSD channel other than E-TCH/F43.2 NT is to be measured a wanted signal level 3 dB above the test signal level specified in subclause 7.3 shall be used. If TCH/FS is not supported, the highest supported of PDTCH/MCS-1 to MCS-4 shall be measured using a wanted signal level 3 dB above the test signal level specified in subclause 7.3.
Table 7.7-1: Wanted signal level for testing of Intermodulation Characteristics
|
BTS Type |
Power level of Wanted Signal |
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|
TCH/FS |
E-TCH/ F43.2 NT |
PDTCH/ MCS-5 |
PDTCH/ MCS-6 |
PDTCH/ MCS-7 |
PDTCH/ MCS-8 |
PDTCH/ MCS-9 |
|
|
GSM 400/GSM 850/GSM 900/ER-GSM 900/GSM 700/DCS 1800/PCS 1900/MXM 850/MXM 1900 BTS |
-101 dBm |
-94 dBm |
-98 dBm |
-96.5 dBm |
-93 dBm |
-90 dBm |
-88.5 dBm |
|
GSM 900/ER-GSM 900/GSM 700/GSM 850/MXM 850 micro‑BTS M1 |
-94 dBm |
-87 dBm |
-91 dBm |
-89.5 dBm |
-86 dBm |
-83 dBm |
-81.5 dBm |
|
GSM 900/ER-GSM 900/GSM 700/GSM 850/MXM 850 micro‑BTS M2 |
-89 dBm |
-82 dBm |
-86 dBm |
-84.5 dBm |
-81 dBm |
-78 dBm |
-76.5 dBm |
|
GSM 900/ER-GSM 900/GSM 700/GSM 850/MXM 850 micro‑BTS M3 |
-84 dBm |
-77 dBm |
-81 dBm |
-79.5 dBm |
-76 dBm |
-73 dBm |
-71.5 dBm |
|
GSM 900/ER-GSM 900/GSM 700/GSM 850/MXM 850 pico-BTS P1 |
-85 dBm |
-78 dBm |
-82 dBm |
-80.5 dBm |
-77 dBm |
-74 dBm |
-72.5 dBm |
|
DCS 1800/PCS 1900/ MXM 1900 micro‑BTS M1 |
-99 dBm |
-92 dBm |
-96 dBm |
-94.5 dBm |
-91 dBm |
-88 dBm |
-86.5 dBm |
|
DCS 1800/PCS 1900/ MXM 1900 micro‑BTS M2 |
-94 dBm |
-87 dBm |
-91 dBm |
-89.5 dBm |
-86 dBm |
-83 dBm |
-81.5 dBm |
|
DCS 1800/PCS 1900/ MXM 1900 micro‑BTS M3 |
-89 dBm |
-82 dBm |
-86 dBm |
-84.5 dBm |
-81 dBm |
-78 dBm |
-76.5 dBm |
|
DCS 1800/PCS 1900/ MXM 1900 pico-BTS P1 |
-92 dBm |
-85 dBm |
-89 dBm |
-87.5 dBm |
-84 dBm |
-81 dBm |
-79.5 dBm |
|
GSM 400/GSM 850/GSM 900/ DCS 1800/PCS 1900/GSM 700 Wide Area multicarrier BTS |
-101 dBm |
-94 dBm |
-98 dBm |
-96.5 dBm |
-93 dBm |
-90 dBm |
-88.5 dBm |
|
GSM 400/GSM 850/GSM 900/ DCS 1800/PCS 1900/GSM 700 Medium Range multicarrier BTS |
-95 dBm |
-88 dBm |
-92 dBm |
-90.5 dBm |
-87 dBm |
-84 dBm |
-82.5 dBm |
|
GSM 400/GSM 850/GSM 900/ DCS 1800/PCS 1900/ GSM 700 Local Area multicarrier BTS |
-87 dBm |
-80 dBm |
-84 dBm |
-82.5 dBm |
-79 dBm |
-76 dBm |
-74.5 dBm |
|
NOTE: TCH/FS and E-TCH/F43.2 are not applicable for MXM850 and 1900 |
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The unprotected class II bits obtained from the BSS receiver after channel decoding and before any extrapolation shall be compared with the unprotected class II bits originating from the BSSTE.
The RBER of the TCH/FS class II bits and BLER of one supported PDTCH/MCS-x with lowest number x and 8PSK modulation (x=5, if the BSS supports all coding schemes) and E-TCH/F43,2 NT or BLER (or BER) of the highest supported data speed and, if TCH/FS is not supported, the BLER for the tested PDTCH/MCS-1 to MCS-4 shall be measured.
The measurement shall be repeated with the unwanted signal frequencies below the carrier frequency of the wanted signal.
Figure 7.7-1: Example of RX intermodulation rejection
7.7.3 Void
7.7.4 Conformance requirement
Test Environment:
Test Environment: Each TRX shall be tested
Minimum Requirement
The RBER of TCH/FS Class II shall not exceed 2.0 %.
The BLER of E-TCH/F43.2 NT shall not exceed 10 % or BLER (or BER) of the highest supported data speed shall not exceed the values given in table 7.3-6.
The BLER of PDTCH/MCS-5
or, if not supported, of PDTCH/MCS-x
with the next higher supported number x shall not exceed 10 %.
For packet-switched channels, the tests and requirements apply for BTTI without PAN
If TCH/FS is not supported the BLER of the tested PDTCH/MCS-1 to MCS-4 shall not exceed the values given in table 7.3-6.
NOTE: This minimum requirement together with conformance to subclause 7.5 (Reference Interference Level) is sufficient to demonstrate compliance to 3GPP TS 45.005 subclause 5.3 for all logical channel types.
7.7.5 Requirement Reference
3GPP TS 45.005 subclause 5.3.