Carrier Aggregation Handover in LTE Networks
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Solution Overview
Problem
Current LTE handover procedures are inefficient and cause delays when carrier aggregation is used, leading to buffering of data during handover in 3GPP LTE networks, as they require reducing activated component carriers to a single carrier before handover, resulting in significant inefficiencies and data transfer interruptions.
Innovation Solution
A method for handover during carrier aggregation that allows the UE to configure and activate specific component carriers upon handover, with the target eNB generating a handover command to signal the set of carriers to be configured and activated, enabling seamless data transfer by allowing multiple carriers to remain active during the handover process, and using activation messages to activate additional carriers post-handover.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the network reduces activated component carriers to a single carrier before handover, then handover can be performed according to current LTE procedure, but data transfer efficiency deteriorates and significant delays occur
Solution Approach 1:
The target eNB pre-configures the set of component carriers that will be activated after handover, preparing the carrier configuration in advance so that multiple carriers can be immediately activated upon handover completion, eliminating the need to reduce to single carrier before handover
Solution Approach 2:
The handover command includes parameters indicating the set of component carriers to be configured and activated, changing the handover procedure to carry additional carrier configuration information, enabling multiple carriers to remain active during handover
2Productivity
If multiple component carriers are activated during handover, then data transfer efficiency improves, but the current handover procedure cannot be followed
Solution Approach 1:
The handover command is enhanced to serve multiple functions: it not only directs the handover but also configures the set of component carriers to be activated, combining handover instruction and carrier configuration into a single universal command structure
Solution Approach 2:
The target eNB acts as an intermediary that prepares and signals the carrier configuration through the handover command, mediating between the source eNB and UE to enable seamless carrier activation during handover without requiring complex coordination
3Reliability
If activated carriers are reduced to single carrier before handover, then handover can proceed with current procedure, but significant buffering of data occurs at source eNB and target eNB
Solution Approach 1:
The target eNB pre-configures and readsies the set of component carriers before handover occurs, so that upon handover completion, data transfer can immediately resume on multiple carriers without buffering delays at either source or target eNB
Data Source
AI summary
Methods for performing handovers and addition of carriers during carrier aggregation operation are described. A mobile station can indicate failure to perform downlink synchronization to some but not all cells of a target eNB, in response to a handover command. The mobile station can activate carriers based on various combinations of transmission of random access preambles, reception of random access response messages and transmission of handover complete messages. A base station can activate carriers based on various combinations of reception of random access preambles, transmission of random access response messages and reception of handover complete messages.