Handover Ranging Code Allocation in Wireless Systems
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Solution Overview
Problem
In broadband wireless access systems, existing handover methods face inefficiencies in allocating additional ranging opportunities and utilizing dedicated ranging codes, leading to potential code collisions and delays during the handover process.
Innovation Solution
A method is introduced where a mobile station receives index information from a serving base station to allocate additional ranging opportunities, allowing it to transmit a ranging code to a target base station, and includes an option to reuse dedicated CDMA ranging codes based on a reuse indicator, enabling efficient handover operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If additional ranging opportunities are allocated to mobile stations during handover, then handover efficiency is improved, but the complexity of managing ranging opportunities and codes increases
Solution Approach 1:
The patent segments the handover process into distinct phases: preparation phase (where SBS and TBS exchange information and allocate ranging opportunities) and execution phase (where MS performs ranging). This segmentation allows additional ranging opportunities to be allocated and managed systematically without overwhelming complexity during the actual handover execution.
Solution Approach 2:
The patent applies preliminary action by having the serving base station and target base station complete information exchange and ranging opportunity allocation before the mobile station actually performs handover. The MS receives handover information including ranging opportunity details from the SBS in advance, preparing everything needed for smooth transition.
2Reliability
If dedicated ranging codes are reused, then code collision probability is reduced, but the risk of using invalid or expired codes increases
Solution Approach 1:
The patent implements feedback mechanisms where the target base station sends ranging response messages to the mobile station, indicating whether the dedicated ranging code was successfully received and validated. This feedback loop allows the MS to understand which codes are valid and have been properly processed by the TBS, preventing reuse of invalid or expired codes.
Solution Approach 2:
The patent applies dynamics by making the ranging code allocation and reuse policy adaptive rather than fixed. The system dynamically determines whether to allocate new codes or reuse existing ones based on real-time conditions, code validity status, and handover requirements, optimizing the balance between code collision avoidance and validity management.
3Adaptability or versatility
If handover information is broadcast through MOB_NBR-ADV messages, then neighbor BS information is disseminated, but information about non-IEEE 802.16e BSs cannot be effectively shared
Solution Approach 1:
The patent applies universality by enabling the serving base station to broadcast heterogeneous network information through multiple message types (both MOB_NBR-ADV for IEEE 802.16e BSs and SII-ADV for other types) so that mobile stations can acquire comprehensive neighbor BS information regardless of the target BS's technology type, making the handover system universally applicable across different network standards.
Data Source
AI summary
A method for performing effective handover (HO) in a broadband wireless access system is disclosed. The method for controlling a mobile station (MS) to perform handover in a broadband wireless access system includes receiving a first message including at least one of first index information and second index information from a serving base station (SBS), wherein the first index information indicates a subframe to which an additional ranging opportunity for the mobile station (MS) is allocated from a target base station (TBS) and the second index information indicates a frame to which the additional ranging opportunity is allocated, and transmitting a ranging code to the target base station (TBS) through the additional ranging opportunity indicated by the first index information and the second index information.