What happens if UE report wrong CQI?

Specs & Protocol Testing
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In LTE (Long Term Evolution) networks, Channel Quality Indicator (CQI) is a crucial feedback metric that the User Equipment (UE) provides to the eNodeB (evolved Node B, which is the base station).

What happens if UE report wrong CQI?
What happens if UE report wrong CQI?883×738 155 KB

CQI is used to indicate the quality of the downlink channel and helps the eNodeB make decisions about the most efficient modulation and coding scheme (MCS) to use for data transmission.

If the UE sends inaccurate CQI values, several issues can arise:

  1. Suboptimal Resource Allocation: The eNodeB relies on CQI to allocate radio resources efficiently. If the CQI value is inaccurate, the eNodeB may either overestimate or underestimate the channel quality. This can lead to suboptimal allocation of resources, where the UE might receive too much or too little data, affecting overall performance.

  2. Reduced Throughput: An inaccurate CQI may lead to the use of inappropriate modulation and coding schemes. For instance, if the CQI indicates a higher channel quality than what actually exists, the eNodeB might use a more complex modulation scheme (like 64-QAM) that the UE cannot handle effectively. This can lead to increased error rates and reduced throughput.

  3. Increased Retransmissions: If the CQI is too optimistic, the transmission may be done using higher-order modulation schemes or higher coding rates, leading to more errors if the actual channel quality is poor. This will result in more retransmissions and reduced overall data throughput.

  4. Poor User Experience: Users might experience slower data rates, increased latency, or poor call quality if the
    network cannot adjust transmission parameters appropriately due to inaccurate CQI feedback.

  5. Network Inefficiency: The overall efficiency of the LTE network can suffer if multiple UEs send inaccurate CQI
    values. The eNodeB might have to make frequent adjustments or compensations, which can lead to increased
    signalling overhead and reduced network performance.
    In summary, accurate CQI reporting is essential for maintaining efficient and high-performance LTE networks.
    Inaccuracies can degrade both individual user experience and overall network efficiency.

LinkedIn: :point_down:

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Same as underfitting or overfitting will do with ML model.

Erroneous CQI reporting may result into higher BLER or lower TBS, resulting into lower spectral efficiency and poor system performance.

Lower throughput, higher latency and more power usage can be expected.

Vendors are offering AI/ML features to reach the optimum system performance by adjusting CQI/PMI/RI feedback and to set BLER target dynamically.