Inter-Frequency Handover Control for IEEE 802.16e Systems
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Solution Overview
Problem
Current broadband wireless access systems lack an effective method for inter-frequency handover within one cell and between different cells when multiple frequency allocations are used, particularly in the IEEE802.16e system, leading to inefficiencies in multimedia service provision due to unutilized frequency bands and unclear handover procedures.
Innovation Solution
A handover control method that involves a serving base station receiving a handover request from a mobile subscriber station, notifying a target base station, and performing a network reentry procedure based on supported frequency allocations, enabling seamless handovers between different frequency allocations within and across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple frequency allocations are allocated to one base station to increase subscriber accommodation and transmit data more efficiently, then data transmission efficiency and subscriber accommodation are improved, but handover control complexity and system management difficulty increase
Solution Approach 1:
The patent segments the handover control process into distinct phases: measurement phase (where the mobile station measures signal strength of multiple FAs), decision phase (where the base station decides which FA to handover to), and execution phase (where the actual frequency allocation change occurs). This segmentation reduces the complexity of managing multiple FAs by breaking down the handover control into manageable steps with clear responsibilities.
Solution Approach 2:
The patent implements preliminary action by having the mobile station measure and report signal strength of multiple frequency allocations before the handover decision is made. The base station receives these measurement reports in advance and uses them to pre-determine the optimal target FA, ensuring that when handover is needed, the decision is already informed by comprehensive measurements, thus simplifying the real-time control process.
2Adaptability or versatility
If inter-FA handover is performed to enable multimedia service when first frequency band resource is occupied, then service availability is improved, but handover procedure clarity and system implementation are worsened
Solution Approach 1:
The patent creates a universal handover procedure that applies to all frequency allocation transitions within the system. The same measurement-report-decision-execution framework works whether the handover is within one cell or between different cells, whether moving between FAs or between base stations. This universality simplifies implementation by providing a single clear procedure that handles multiple scenarios.
Solution Approach 2:
The patent introduces measurement reports as an intermediary mechanism between the mobile station and the base station. These reports contain standardized information about signal strength and availability of multiple FAs, serving as a clear communication bridge that enables the base station to make informed handover decisions without complex real-time calculations, thus clarifying the handover procedure.
3Ease of operation
If handover is performed from serving base station to target base station with multiple FAs, then subscriber mobility and service continuity are improved, but frequency allocation selection uncertainty and service interruption risk increase
Solution Approach 1:
The patent implements feedback by having the mobile station continuously measure and report signal strength of available frequency allocations to the base station. This feedback loop ensures that the base station has real-time information about the actual signal conditions, enabling it to select the optimal target FA that guarantees service continuity and minimizes interruption during handover.
Solution Approach 2:
The patent performs preliminary measurement and evaluation of multiple frequency allocations before the actual handover execution. The mobile station measures signal strength in advance, and the base station evaluates which FA would provide the best service continuity. This preliminary action ensures that when handover is executed, the selected FA is already optimized for maintaining service continuity, reducing uncertainty and interruption risk.
Data Source
AI summary
A method for transitioning communications of a mobile subscriber station from a serving base station to a target base station includes receiving from the mobile subscriber station a transition request message having an identifier which identifies the mobile subscriber station, and transmitting a transition request notification message having the identifier to the target base station. The method further includes receiving a transition request notification response message having information relating to capabilities of the target base station, and transmitting a transition response message having the information to the mobile subscriber station.