Hidden Cell-Blocking via Access Network Call Rejection
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Solution Overview
Problem
Existing cell-blocking mechanisms in cellular communications networks are detectable, incomplete in blocking communications, and can prevent emergency calls, making them unsuitable for targeted communication disruptions.
Innovation Solution
A 'hidden' cell-blocking method that selectively disconnects active calls and blocks incoming/outgoing calls on the access-network side without broadcasting specific signals, allowing emergency calls to proceed while other communications are blocked, and can be configured to target specific access classes and call causes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cell-barring or cell-reservation mechanisms are used to block communications in a target cell, then access control is achieved, but the blocking mechanism becomes detectable by users through broadcast signals
Solution Approach 1:
The patent extracts the blocking function from the broadcast domain and implements it in the access network side through call setup rejection and handover rejection mechanisms. This removes the detectable broadcast signals while maintaining blocking effectiveness through direct access network control.
Solution Approach 2:
The access network acts as an intermediary that silently blocks calls and handovers without informing UEs. The network nodes (eNodeB, RNC, NodeB) mediate between the UE access attempts and the core network, rejecting them without broadcasting blocking status to users.
2Reliability
If cell-barring or access restriction mechanisms are implemented, then some access control is achieved, but communications are not fully blocked as calls-in-progress and handovers continue
Solution Approach 1:
The patent implements preliminary blocking by rejecting call setups and handovers before they can be established. The access network proactively prevents call establishment and handover execution, ensuring complete blocking before communications begin or continue in the target cell.
Solution Approach 2:
The blocking mechanism is segmented into multiple independent functions: call setup rejection, handover rejection, and active call termination. Each function operates independently to ensure complete blocking across all communication types without requiring a single complex mechanism.
3Reliability
If cell-barring mechanisms are used to block communications in a target cell, then access control is implemented, but emergency calls are also prevented
Solution Approach 1:
The patent applies different blocking characteristics to different call types. Normal calls are completely blocked through rejection mechanisms, while emergency calls are identified and permitted to proceed. This local differentiation of blocking quality enables selective control based on call nature.
Solution Approach 2:
The system changes the blocking parameter based on call establishment cause. By detecting the establishment cause indicator, the access network dynamically adjusts whether to reject or permit the call, allowing emergency calls (specific parameter value) to bypass blocking while maintaining blocking for normal calls.
4Loss of information
If broadcast signals are used to indicate cell-barring or access restriction, then UEs can recognize the blocking status, but malicious persons can deduce that communications are being blocked
Solution Approach 1:
The patent removes the broadcast notification component from the blocking mechanism. Blocking status is no longer transmitted via broadcast signals to UEs, eliminating the information source that malicious persons could exploit to detect blocking operations.
Solution Approach 2:
The patent converts the potential harm of detectable blocking into a benefit by using the same access network infrastructure that normally provides service to silently enforce blocking. The blocking mechanism leverages existing network control capabilities to achieve both security (undetectable blocking) and functionality (complete communication control).
Data Source
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AI summary
In a cellular communications network comprising user equipment and an access network, a cell-blocking method involves designating a cell in the network that is to be blocked and activating a cell-blocking operating mode of a node of the access network of the cellular communications network. According to the cell- blocking method, upon activation of the cell-blocking mode of the access-network node, active calls in the designated cell are detected and disconnected. The disconnection of active calls may be performed selectively based on an access class or establishment cause associated with the call. The cell-blocking may be hidden because the access-network node may not broadcast any data that is indicative of cell-blocking and, when a user equipment in the affected cell attempts to set-up a call, the access-network node may reject the call using an admission control mechanism or may send back a spoofed message from the core network.