Research challenges


 * Dense deployment of femtocell can address the exponential rise of mobile data traffic generated from indoor. However, dense deployment gives rise to interference which may reduce the capacity of the network. We can think of two different interference scenarios:


 * Cross layer-interference: Interference between femtocell and macrocell
 * co-layer interference: Interference between neighboring femtocells

It is a challenging task to develop effective interference mitigation techniques especially considering the following two aspects:
 * where the deployment of femtocell is tightly controlled by the operators
 * where the deployment of femtocell is loosely controlled by the operators (or have no control)

The later deployment scenario is envisioned for mass deployment of femtocells. But the question is how to control and coordinate for example the frequency assignment for femtocell if user controls the deployment and configuration of femtocells. How to control Interference for mass deployment of UMA-enabled Femtocell AP.

For the later deployment scenario, mobility management presents a big challenge. In mobility management, cell selection/reselection and handover in two-tier femto-macro networks are major issue to resolve.


 * Femtocell-based services use public Internet for connectivity and thereby integrate to core network. Conventional core network is not designed to integrate thousands (or millions) of femtocell access points. Scalability is a concern here.


 * Security:
 * All threat to public Internet
 * Unauthorized access to core network infrastructure via IP access could result in theft or modification of data, unauthorized eavesdropping, illicit spamming/packet injection, launch of denial of service attacks, etc. (Mitigation: Femtocell access point traffic should be secured using IPSEC VPN over, put security gateways at the edge of the core network)
 * The security solution should efficiently handle multiple simultaneous calls over the backhaul.
 * Maliciously modify radio parameters (can jeopardize radio quality)
 * Unlawful interception capability
 * MoM attack
 * DoS attack (affect overall customer experience)
 * Threat analysis
 * Investigate & develop startegies & techniques to Mitigate ever-evolving threats (with loosely controlled set-up operator cannot install patch remotely)
 * Running the Iu-b interface over the Internet requires a new security layer to protect the RNC and mobile network from Internet attacks. (is it? taken from a report published in 2007)'

Reference:
 * Jie Zhang and Guillaume de la Roche, Femtocells Technologies and Deployment, WILEY, 2010.