Femto Base Station SID Alternation for Mobile Retention
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Solution Overview
Problem
Mobile stations in areas of overlap between multiple base station systems may prefer higher-priority networks, leading to undesirable service from a femto base station due to priority listing in the Preferred Roaming List (PRL), resulting in ping-ponging between femto and macro base stations and inefficient battery usage.
Innovation Solution
A base station system alternates between broadcasting different System Identifiers (SIDs) on its control channel, determining which timeslots a mobile station monitors, and broadcasting a specific SID in those timeslots to attract and retain mobile stations, ensuring they connect to the femto base station by matching or exceeding the priority listed in the mobile station's PRL.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a base station system broadcasts a single fixed SID, then the system configuration is simple, but mobile stations with lower-priority SIDs in their PRL will not connect to the desired femto base station
Solution Approach 1:
The base station dynamically changes its broadcasted SID over time, alternating between a first SID and a second SID in different timeslots. This dynamic behavior allows the base station to adapt to different mobile station PRL configurations without requiring complex per-mobile-station customization, resolving the contradiction between adaptability and simplicity.
Solution Approach 2:
The base station employs periodic alternation of SIDs in a cyclic manner, where the first SID is broadcast in certain timeslots and the second SID is broadcast in other timeslots. This periodic action ensures that mobile stations with either SID in their PRL can eventually connect, achieving high adaptability through a simple periodic broadcasting pattern.
2Reliability
If a mobile station continuously monitors for higher-priority networks, then the mobile station can find the best available network, but the mobile station experiences ping-ponging between femto and macro base stations causing battery drain
Solution Approach 1:
The base station preemptively broadcasts SIDs that match what mobile stations expect to find in their PRLs. By having the mobile station connect to the base station using a SID it already has in its PRL, the system prevents subsequent disconnections and re-searches, thereby stabilizing the connection and reducing the energy-consuming ping-ponging behavior.
3Area of stationary object
If a femto base station uses a SID that is lower priority in the PRL than a macro base station SID, then the macro base station can provide broader coverage, but the mobile station will prefer the macro base station over the femto base station in overlap areas
Solution Approach 1:
The femto base station achieves universal compatibility with mobile stations by broadcasting multiple SIDs that are likely to be present in various mobile station PRL configurations. This allows the femto base station to serve as a universal access point for mobile stations regardless of their specific PRL contents, enabling it to function effectively in coverage overlap areas despite using a lower-priority SID.
Data Source
AI summary
A method and system for controlling broadcast of system identification. A base station may broadcast in one or more timeslots of a control channel, as a System Identifier (SID) of the base station, a particular SID, but may broadcast in one or more other timeslots of the control channel, as a SID of the base station, a different SID. In addition, when a mobile station registers to be served by the base station, the base station may determine which slot(s) of the control channel the mobile station will monitor and may broadcast in the determined slot(s) a SID that may help to keep the mobile station from transitioning to be served by a different base station.