Femtocell Radio Technology

In this section:
Interference Management in Femtocells
- Interference Avoidance Through Frequency Planning
- Interference Mitigation in Co-Channel Femtocell Deployments
Seamless Mobility Across Femtocell-Macrocell Boundaries
Mobility in Standby Mode & Access Control
- Handoffs at Femtocell Coverage Boundaries

Femtocell Access Control

Femtocells support flexible access control mechanisms.
In restricted access, the femtocell owner can restrict femtocell usage to members of the household and frequent visitors and avoid sharing Internet backhaul with others. CDMA femtocells implement restricted access by having its beacon redirect only authorized mobile devices, thus leaving unauthorized mobile devices continue to operate normally on other radio channels and attached to the macrocell. Unauthorized mobile devices on the same radio channel as the femtocell who detect the femtocell are allowed to camp on the femtocell and when they turn active they are handed out to the macrocell on a different radio channel. This approach ensures that no unauthorized active user is allowed to use the femtocell and they are moved away from the femtocell radio channel to avoid interference.

UMTS femtocells implement access control by sending an appropriate “rejection” message, which causes the mobile device to switch to another radio channel on the macrocell network.

Mobile operators may choose to provide commercial incentives to femtocell owners to have them configure their femtocells in open access mode, where any mobile device can receive service from the femtocell. Open access not only makes the femtocell experience available to more users, it also avoids many of the interference scenarios discussed in the previous section. In open access, the femtocell beacon will redirect all mobile devices within its coverage area to the femtocell radio channel.

Hybrid access is similar to open access except here certain mobile devices selected by the femtocell owner are given preferential treatment over other mobile devices that can use the femtocell on a best-effort basis.[source]
Figure 3 Simplified CDMA2000 1x Circuit-switched Services Femtocell Architecture


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