This document discusses various anti-interference features of Huawei's GSM technology: 1. Interference Cancellation Combining (ICC) reduces uplink interference by evaluating and eliminating interference based on spatial correlations between receive antennas. 2. Enhanced ICC (EICC) builds upon ICC by also considering temporal correlations to better suppress interference. 3. Multi-dimensional ICC (MICC) further improves evaluation accuracy by considering multiple dimensions such as multiple sample points and virtual antennas. 4. Robust Air Interface Signaling improves signaling reliability under interference through techniques like repeated FACCH and SACCH transmissions. 5. Um Adaptive Interference Suppression enables the BTS

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HUAWEI TECHNOLOGIES CO., LTD.
GSM Anti-interference Features

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Index
Feature Index
1ICC
2EICC
3MICC
4Robust Air Interface Signaling
5Um Adaptive Interference Suppression

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ICC Reduce Uplink Interference
Introduction
The GSM system uses the receive diversity technique to eliminate various types of fading. With receive diversity,
the receive (RX) end receives the same signal from multiple diversity antennas and combines the received signal
into a strong wanted signal. This improves the receive quality of uplink signals.
the interference on the GSM system, such as inter-symbol, co-channel, and adjacent-channel interference,
increases the bit error rate (BER), resulting in deteriorated speech quality and even call drops. To counteract the
negative effects of receive diversity and GSM interference, Huawei introduces the Interference Cancellation
Combining feature when the GSM system uses receive diversity. This feature provides interference cancellation
combining algorithms to evaluate and eliminate interference based on the spatial and time correlations of the
interference. This feature therefore increases the anti-interference capability of the GSM system and further
improves the receive quality of uplink signals.
The interference cancellation combining algorithms consist of:
•ICC
•EICC
•MICC

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The ICC algorithm, is a multi-antenna combining technique based on MRC. Without considering interference
correlations, MRC is ideal for networks with limited noises but without interference. However, on live networks,
especially when a tight frequency reuse pattern is used, interferences on different antennas may be caused by the
same interfering signal. Therefore, they are correlated. ICC uses this correlation to eliminate certain interference
when signals from two antennas are combined.
As shown in Figure above, both signal and interference are considered as vectors. The MRC algorithm combines the
target signals to obtain a high-power signal without considering interfering signals. The ICC algorithm considers
interfering signal correlations and performs interfering signal cancellation to minimize the power of the combined
interfering signal, thereby improving the overall carrier-to-interference ratio (CIR) of receive signals.
Activation
1.On the BSC LMT, run the SET GCELLSOFT command with Interference Cancel Mode Selection set to ICC(ICC) and
both Interference Cancel Mode Adaptation and Enhanced Interference Cancel Mode Adaptation set to ON(On).
2.Run the SET GCELLOTHEXT command with IC Adaptive Scenario Identify Optimize Switch set to ON(On).

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EICC Reduce Uplink Interference
Activation
Introduction
The EICC algorithm, is developed based on ICC. Generally, the interfering signals received from multiple antennas have
spatial correlations in terms of antennas and have time correlations in terms of sampled points. ICC considers only
spatial correlations to eliminate interference. As EICC considers both spatial and time correlations and combines
signals by structuring the multidimensional combining coefficient matrix based on the maximum SNR criterion. This
effectively suppresses or even eliminates interference, thereby helping operators provide high-quality uplink signals.
• One signal received by different antenna has spatial
correlation and temporal correlation
• ICC uses spatial correlation, EICC combines both spatial
and temporal correlation
• Obvious gain in bad condition: HQI increased compared with ICC.
1.On the BSC LMT, run the SET GCELLSOFT command with EICC
Allowed set to YES(Yes) and both Interference Cancel Mode
Adaptation and Enhanced Interference Cancel Mode Adaptation
set to ON(On).
2.Run the SET GCELLOTHEXT command with IC Adaptive Scenario
Identify Optimize Switch set to ON(On).

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MICC Reduce Uplink Interference
Introduction
Interference cancellation combining algorithms obtain interference characteristics by detecting and evaluating the
interference, and then eliminate interference based on its characteristics.
The MICC algorithm, uses multi-sampled points, virtual multi-antenna, and extended pilot techniques to
accurately evaluate interference in multiple dimensions. This significantly improves the evaluation accuracy,
thereby minimizing interference.
The benefits
• Compared with ICC, EICC,MICC can decreases more proportion of uplink receive quality ranks 6 to 7 when
networks are experiencing interference
Activation
Run the SET GCELLBASICPARA command with MICC Switch set to ON.

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Robust Air Interface Signaling
Introduction
On networks with tight frequency reuse, strong interference, and poor radio transmission performance, signaling
messages sent on the fast associated control channel (FACCH) or slow associated control channel (SACCH) may be lost
because of the high bit error rate (BER) on the Um interface. Huawei introduces the Robust Air Interface Signaling
feature to enable the BTS and MSs to repeatedly resend failed FACCH and SACCH messages. This makes FACCH and
SACCH links more immune to interference and the BSC and MSs more likely to successfully receive signaling messages.
Robust Air Interface Signaling consists of the following functions:
•Repeated Downlink FACCH If an MS supports Repeated Downlink FACCH and the receive quality in the downlink
measurement report (MR) sent by the MS is lower than a specified threshold, the BTS will retransmit FACCH messages
to increase the probability that the MS will receive signaling messages.
•Repeated SACCH
For the MSs supporting repeated SACCH, the BTS updates the counter based on the uplink SACCH decoding information.
If the counter exceeds a specified threshold, the BTS instructs the MS to retransmit the SACCH message that is last sent.
If the MS cannot correctly decode the SACCH message, the MS notifies the BTS of the information through signaling,
and the BTS updates the counter based on the downlink SACCH decoding information. If the counter exceeds a
specified threshold, the BTS retransmits the SACCH frame that is last sent.
Benefits

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Robust Air Interface Signaling
•Repeated Downlink FACCH increases the FACCH performance of common MSs by about 2 dB and the FACCH
performance of R6 MSs by about 4 to 5 dB.
•Repeated SACCH increases the SACCH performance of R6 MSs by about 4 to 5 dB.
•The improvements in FACCH and SACCH performance reduce the call drop rate and make handover and power control
decisions more accurate.
On the BSC LMT, run the SET GCELLCCBASIC command with its
parameters set as follows:
•Set ECSC to YES(Yes).
•Set Repeated Downlink FACCH to YES(Yes).
•Set Repeated Downlink FACCH Threshold to 5.
•Set Repeated SACCH to YES(Yes).
•Set Repeated SACCH DL Retransmission Threshold to 8.
•Set Repeated SACCH UL Retransmission Threshold to 8.
Activation

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Um Adaptive Interference Suppression
Introduction
User
Adjacent Channel
Interference
Co-channel
Interference
Co-channel
Interference
0.001
0.01
0.1
1
FER
C/I 1dB Interval
GMSK TCHFS ACI Typical Urban
UmAIS_ON
UmAIS_OFF
1.5dB
The Um Adaptive Interference Suppression feature enables the BTS to detect Um interface interference characteristics on each
timeslot used by MSs. Based on the detection result, the BTS selects an optimal interference suppression method to minimize th
interference in various scenarios. This protects wanted signals if possible and improves the anti-interference capability of the
network.
This feature also provides an enhanced interference suppression algorithm for CS services. With this algorithm, the BTS filters th
synchronization position on a timeslot used by an MS. This improves the network anti-interference capability and uplink receive
quality.
This feature applies to the tight frequency reuse pattern.
Benefits
Improves the uplink anti-interference capability during
refarming.
Improves the uplink receive quality for CS services.
Further improves the uplink receive quality by working with the
ICC and EICC features.
Increases uplink data upload rates for PS services.

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