Subscriber Station Handover in Broadband Wireless Access Systems
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Solution Overview
Problem
Current broadband wireless access communication systems, such as IEEE 802.16a, do not consider mobility of subscriber stations, leading to a lack of handover operations in multi-cell environments, which is essential for maintaining connectivity as users move between cells.
Innovation Solution
A system and method for performing handover operations in a BWA communication system by receiving handover requests from subscriber stations, measuring Carrier to Interference and Noise Ratios (CINRs) of neighboring base stations, selecting a target base station, and performing a handover function to ensure seamless mobility across cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single cell structure is used in BWA communication system, then system complexity is reduced, but mobility support and handover capability are lost
Solution Approach 1:
The patent divides the communication system into multiple cells, each managed by a separate base station. This segmentation enables the system to handle mobile subscriber stations by assigning them to different cells based on their location, thereby supporting mobility while maintaining manageable system complexity through modular cell structures.
Solution Approach 2:
The patent implements dynamic cell selection and handover mechanisms where the serving base station can change based on the subscriber station's movement. The system dynamically adjusts which cell the SS serves by evaluating signal quality metrics like CINR, enabling adaptive mobility support without requiring complex reconfiguration of the entire network.
2Adaptability or versatility
If handover operation is implemented in multi-cell environment, then mobility and connectivity are improved, but system complexity and handover management difficulty increase
Solution Approach 1:
The patent implements self-service handover mechanisms where the subscriber station autonomously measures signal quality from multiple base stations and generates handover requests based on predefined criteria. The SS monitors its own connection quality and initiates handover when necessary, reducing the burden on the network to manage every handover detail centrally.
Solution Approach 2:
The patent employs feedback mechanisms where the subscriber station reports signal quality measurements (CINR) to the serving base station, which then makes informed handover decisions. This feedback loop enables intelligent handover management based on real-time channel conditions, simplifying the control logic compared to open-loop approaches.
3Reliability
If initial ranging process is required for handover, then connection establishment is ensured, but data communication interruption time increases
Solution Approach 1:
The patent performs preliminary actions by having the subscriber station continuously measure signal quality from multiple base stations in the background, even before a handover is needed. The SS maintains a list of candidate base stations with their signal characteristics, so when handover becomes necessary, the target base station is already prepared and the SS can be quickly reassigned without requiring a full initial ranging process.
Solution Approach 2:
The patent enables the handover process to skip the time-consuming initial ranging steps by establishing a pre-configured connection to the target base station. The SS can be quickly handed over to a pre-selected target base station that has already been evaluated and is ready to accept the connection, rushing through the handover process without unnecessary delays.
4Measurement precision
If multiple neighbor base stations are monitored, then handover decision accuracy is improved, but measurement and processing time increase
Solution Approach 1:
The patent applies partial action by having the subscriber station monitor signal quality from a limited number of neighboring base stations rather than all possible base stations in the network. The SS focuses measurements on the most relevant neighbors based on geographic location and signal strength, achieving sufficient accuracy for handover decisions without the time cost of monitoring every possible base station.
Data Source
AI summary
A system and method for performing a handover operation in a broadband wireless access (BWA) communication system. The BWA communication system includes a serving BS (Base Station), (Subscriber Station), and a plurality of neighbor BSs adjacent to the serving BS. The SS handover method upon receiving a handover request from the SS in the BWA communication system includes the steps of: a) receiving from the serving BS information of the plurality of neighbor BSs; b) measuring CINRs (Carrier to Interference and Noise Ratios) of pilot signals transferred from the neighbor BSs upon receipt of the neighbor BSs information; c) transmitting to the serving BS a handover request signal along with pilot signal CINR information of the neighbor BSs; d) upon receipt of the handover request signal, receiving from the serving BS information of a handover enable target BS contained in the neighbor BSs; and e) performing a handover function from the serving BS to the target BS.