LTE Handover Source eNB Determining HeNB Type via E-CGI Bit
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Solution Overview
Problem
In LTE mobile communication systems, the inability to determine the type of handover destination radio base station (eNB or HeNB) based on the E-CGI in Measurement Reports leads to difficulties in deciding the length of the Global eNB ID in the HO Required message, preventing successful S1 handovers when radio base stations with different eNB IDs coexist.
Innovation Solution
A mobile communication method that determines whether a handover destination candidate radio base station is a macro cell eNB or a small cell HeNB using a predetermined bit in the Cell ID of the E-CGI, allowing the handover source radio base station to set the appropriate length for the Global eNB ID in the HO Required message, and the mobile switching center to manage and route the handover requests accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the handover source radio base station uses E-CGI in Measurement Report to identify handover destination candidate radio base station, then it can acquire Global eNB ID and TAI information, but it cannot determine the type (eNB/HeNB) of the handover destination candidate radio base station
Solution Approach 1:
The invention extracts the critical distinguishing bit from the Cell ID field within E-CGI to determine radio base station type. By taking out this specific bit (most significant bit) that differs between eNB and HeNB, the system can identify the base station type without requiring additional signaling or information elements.
Solution Approach 2:
The invention adds a new dimension of analysis by examining the bit structure of Cell ID within E-CGI. Instead of treating E-CGI as a single opaque identifier, the system breaks it down into its constituent fields (PLMN ID, Cell ID) and further analyzes the bit-level structure of Cell ID to extract type information.
2Productivity
If the handover source radio base station transmits HO Required message with Target ID to mobile switching center MME, then it can initiate handover procedure, but the MME cannot properly route the handover request when eNB ID length is not correctly identified
Solution Approach 1:
The handover source radio base station performs preliminary determination of the handover destination candidate's type (eNB or HeNB) by analyzing the E-CGI before transmitting the HO Required message. This preliminary action ensures that the Global eNB ID is formatted with the correct length (20 bits for eNB, 28 bits for HeNB) before the handover request is sent to MME, enabling proper routing.
Solution Approach 2:
The system uses the Measurement Report containing E-CGI as feedback information about the handover destination candidate. The handover source radio base station analyzes this feedback (E-CGI bit structure) to determine the destination type and accordingly formats the HO Required message with the appropriate Global eNB ID length.
3Device complexity
If the mobile station UE transmits Measurement Report with only PCI information, then the report structure remains simple, but the handover source radio base station cannot extract identification information of handover destination candidate radio base station
Solution Approach 1:
The invention makes the E-CGI field serve multiple functions: it continues to provide the traditional cell identification function while simultaneously encoding the radio base station type information through its bit structure. This allows the Measurement Report to maintain its simple structure while carrying additional useful information for handover processing.
Data Source
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AI summary
Even when radio base stations including radio base station identification information eNB IDs having different lengths are coexistent, it is possible to perform an S1 handover. A mobile communication method according to the present invention includes a step of determining, a handover source radio base station eNB#0, whether a handover destination candidate radio base station is a macro cell radio base station eNB or a small cell radio base station HeNB with reference to a predetermined bit set in Cell ID included in E-CGI included in Measurement Report received from a mobile station UE.