CCE Aggregation Level Adjustment for Robust Handover Signaling
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Solution Overview
Problem
The handover performance in wireless communications networks is negatively affected by interference from frequency-shifted Cell Specific Reference Signals (CRS) between cells, leading to increased loss of service, especially during voice services, due to disturbances in Physical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH) symbols.
Innovation Solution
Increasing the Control Channel Element (CCE) aggregation level in Orthogonal Frequency Division Multiplexing (OFDM) subframes during handover procedures to enhance the robustness of the PDCCH against interference, thereby improving the quality of the connection and reducing unsuccessful handovers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If frequency-shifted Cell Specific Reference Signals (CRS) are used between cells, then cell coverage and signal synchronization are improved, but interference on Physical Downlink Control Channel (PDCCH) and Physical Downlink Shared Channel (PDSCH) symbols increases, leading to degraded handover performance
Solution Approach 1:
The patent applies local quality by differentiating the CCE aggregation level based on the specific service type. For voice services, a higher aggregation level (e.g., level 4 or 8) is applied locally to the PDCCH to provide enhanced protection against CRS interference, while data services can use lower aggregation levels to maintain spectral efficiency. This localized adaptation of quality parameters resolves the contradiction by providing targeted protection where needed without universally degrading system performance.
Solution Approach 2:
The patent changes the CCE aggregation level parameter dynamically based on service type and interference conditions. By adjusting this parameter from standard levels (1, 2, 4, 8) according to whether the service is voice or data-oriented, the system adapts to varying interference scenarios. This parameter change allows the PDCCH to maintain robustness against frequency-shifted CRS interference for critical voice handovers while preserving overall network efficiency.
2Reliability
If Control Channel Element (CCE) aggregation level is increased to enhance PDCCH robustness against interference, then handover reliability is improved, but spectral efficiency decreases
Solution Approach 1:
The patent applies local quality by differentiating the CCE aggregation level based on the specific service type. For voice services, a higher aggregation level (e.g., level 4 or 8) is applied locally to the PDCCH to provide enhanced protection against CRS interference, while data services can use lower aggregation levels to maintain spectral efficiency. This localized adaptation of quality parameters resolves the contradiction by providing targeted protection where needed without universally degrading system performance.
Solution Approach 2:
The patent applies partial action by increasing the CCE aggregation level only for specific service types (voice services) and specific conditions (handover scenarios), rather than applying it universally to all transmissions. This selective application means that the robustness enhancement is applied partially - only where the interference from frequency-shifted CRS is most problematic - thereby maintaining spectral efficiency for other services while still improving handover reliability for voice communications.
3Productivity
If minimum control region size is maintained to maximize data region size, then data transfer rate is improved, but robustness of PDCCH against interference is reduced
Solution Approach 1:
The patent applies local quality by differentiating the CCE aggregation level based on the specific service type. For voice services, a higher aggregation level (e.g., level 4 or 8) is applied locally to the PDCCH to provide enhanced protection against CRS interference, while data services can use lower aggregation levels to maintain spectral efficiency. This localized adaptation of quality parameters resolves the contradiction by providing targeted protection where needed without universally degrading system performance.
Solution Approach 2:
The patent applies partial action by increasing the CCE aggregation level only for specific service types (voice services) and specific conditions (handover scenarios), rather than applying it universally to all transmissions. This selective application means that the robustness enhancement is applied partially - only where the interference from frequency-shifted CRS is most problematic - thereby maintaining spectral efficiency for other services while still improving handover reliability for voice communications.
Data Source
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AI summary
A method performed by a network node 110, for improving the performance of a handover of a user equipment (UE) 120, wherein the network node 110 serves a first cell 130 comprising one or more UEs 120. When the network node 110 has detected that a Signaling Radio Bearer (SRB) is determined to be scheduled for a UE 120 in handover from the first cell 130 to a second cell 131, the network node 110 increases the Control Channel Element (CCE) aggregation level in an OFDM-subframe to be sent to the UE 120 in a TTI related to the handover. By increasing the CCE aggregation level during a handover procedure, the effective coding rate of the PDCCH is increased, which leads to a more robust coding and reliability. Thereby the number of unsuccessful handovers and lost service is effectively reduced.