Call Admission Control for Wi-Fi Networks
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Solution Overview
Problem
Existing wireless network technologies, such as IEEE 802.11e, fail to guarantee quality of service for user sessions as Wi-Fi devices move between access points, leading to potential call drops due to insufficient resource reservation across the Wi-Fi infrastructure.
Innovation Solution
A call admission control scheme that uses a service controller to manage access points, evaluating probabilities of active session mobility and idle device activation to reserve resources across the network, issuing 'call admission credits' to ensure seamless service continuity as devices move between access points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If basic CAC function is used to determine airtime for new flows, then local bandwidth utilization is optimized, but call continuity is not guaranteed when user devices move between access points
Solution Approach 1:
The patent applies preliminary action by reserving bandwidth resources in advance across multiple access points based on predicted user movement patterns. The system calculates probability functions for user device mobility and proactively allocates bandwidth at neighboring access points before handover occurs, ensuring call continuity without waiting for actual movement events.
Solution Approach 2:
The service controller acts as an intermediary between individual access points and user devices. It coordinates bandwidth reservation across multiple access points, managing the complex interactions between local bandwidth utilization and global call continuity requirements. The controller uses probability-based predictions to mediate resource allocation decisions that balance local efficiency with overall service reliability.
2Reliability
If bandwidth is reserved for entire call duration across all access points, then call continuity is guaranteed during mobility, but network resource overhead increases
Solution Approach 1:
The patent implements partial action by reserving bandwidth for only the most critical portions of call duration based on mobility probability assessments. Instead of reserving resources for the entire call duration unconditionally, the system selectively reserves bandwidth at access points where handover is predicted to occur, achieving call continuity while minimizing unnecessary resource overhead at access points with low mobility probability.
Solution Approach 2:
The system dynamically adjusts bandwidth reservation parameters based on calculated probability functions. The reservation amount and duration are modified according to real-time assessments of user mobility patterns, network load conditions, and service type requirements. This parameter adaptation allows the system to optimize the balance between call continuity guarantee and resource overhead minimization.
3Ease of operation
If CAC determines admission based on current AP load only, then local service quality is maintained, but seamless mobility between access points cannot be supported
Solution Approach 1:
The service controller provides universal management functionality that serves multiple access points simultaneously. It performs both local service quality monitoring and global mobility coordination functions, enabling each access point to maintain local service standards while participating in network-wide handover coordination. The controller aggregates information from multiple access points to make holistic admission control decisions.
Solution Approach 2:
The patent extends the CAC decision-making from a single access point dimension to a multi-dimensional network view. The service controller considers spatial relationships between multiple access points, user device mobility trajectories, and temporal patterns across the network. This dimensional expansion allows admission control decisions to account for both local service quality and future mobility requirements simultaneously.
Data Source
AI summary
Call admission control within a wireless network is implemented using a service controller that manages a set of access points. The call admission control (CAC) function for a given access point determines whether the access point has sufficient unused bandwidth to handle an additional call. The service controller makes this determination by monitoring the access points and evaluating certain probability functions and load conditions. In one embodiment, a determination of whether the access point has sufficient unused bandwidth to handle an additional call is a function of two (2) independent probabilities: (i) a probability of an active session moving to the access point from one or more neighbor access points, and (ii) a probability of an idle mobile device already associated with the access point entering into a new active session by initiating an inbound or outbound call. According to another aspect, the service controller issues and manages “call admission credits” among the set of access points, where a call admission credit value indicates a number of calls that idle mobile devices associated with the access point may initiate from the AP. The call admission credits value is a function of a determined load on the AP, and a mobility probability, which is a probability of an active call moving to the access point from one or more neighbor access points. The call admission credit value for the access point is adjusted as a function of a change of the load or in the mobility probability.