Heterogeneous Network Handover Coordination via Cell Range Expansion
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Solution Overview
Problem
Current technologies lack coordination mechanisms for using Cell Range Expansion (CRE), Almost Blank Subframes (ABS), and Reduced Power SubFrames (RPSF) techniques across different eNBs in heterogeneous wireless networks, leading to inefficient handover processes and increased interference in heterogeneous wireless networks.
Innovation Solution
Implementing a system where first and second base stations communicate CRE information, including protected communication times, to coordinate handovers and reduce interference, by evaluating and adjusting CRE offsets for user equipment (UE) measurements and determining appropriate handover requests based on CRE information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If Cell Range Expansion (CRE) is used to extend the coverage area of smaller cells, then the coverage area is improved, but interference from macro cells increases
Solution Approach 1:
The patent segments the network into macro cells and smaller cells with distinct functions. Macro cells provide wide area coverage while smaller cells provide capacity in specific areas. The segmentation is further applied by dividing time into protected subframes where macro cells reduce transmission, allowing smaller cells to serve CRE UEs with reduced interference.
Solution Approach 2:
The patent implements periodic action through Almost Blank Subframes (ABS) where macro cells periodically reduce or stop transmissions during specific subframes. This periodic reduction of macro cell activity creates protected time windows that allow smaller cells to communicate with CRE UEs with minimal interference, thus resolving the interference issue while maintaining extended coverage.
2Reliability
If coordinated handover evaluation is implemented between base stations, then handover success probability is improved, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by having the first base station receive and evaluate CRE information from the second base station before the handover decision is made. The target base station prepares by providing CRE information including protected communication times, allowing the serving base station to evaluate potential handover targets in advance and make more reliable handover decisions.
Solution Approach 2:
The patent uses an intermediary approach where CRE information acts as a mediator between base stations. Instead of complex direct coordination for every handover decision, the system uses pre-exchanged CRE information about protected subframes and cell range expansion parameters to enable informed handover evaluations, reducing the complexity of real-time coordination.
Data Source
AI summary
A first base station provides radio communication service to user equipments, UEs, and a second base station that provides radio communication service to UEs in adjacent cell service area. The first base station receives cell range expansion, CRE, information from the second base station for expanding the size of the first cell and evaluates handover of one or more UEs with respect to the second cell based on the CRE information. In one embodiment, the second base station determines a CRE related configuration that includes the CRE information with respect to the first cell, sends the CRE information to the first base station. For example, the second base station may send a handover request including the CRE information to the first base station. The second base station also may consider CRE information in handover evaluation.