Private Femtocells for Indoors

It is essential that femtocells implement proper transmit power calibration primarily to achieve a good tradeoff between downlink coverage and interference to other macrocells and femtocells. It is, however, challenging to develop a practical transmit power calibration scheme that provides excellent performance in different deployment scenarios.

UltraSON™ Transmit (Tx) power calibration suite consists of the following features:

• Network Listen Based Transmit Power Calibration (NLPC): This feature enables location aware self-calibration of transmit power after a femtocell is installed. It uses the Network Listen Module present in the femtocell to sense the surrounding RF conditions.
• Mobile Assisted Range Tuning (MART): This feature implements optimized transmit power calibration based on mobile reports and registrations for residential settings.
• Supervised Mobile Assisted Range Tuning (SMART): This feature is designed for enterprise settings deploying multiple femtocells. It ensures optimized transmit power calibration based on mobile reports utilizing a simple and effortless technician walk.
• Guest Mobile Protection (GUMP): This feature helps femtocells to dynamically throttle transmit power based on uplink pilot power measurements to protect nearby active guest mobiles.

Tx power calibration algorithms essentially use mobile feedback to learn key information such as required coverage range, surrounding RF environment and impact of interference. Power calibration algorithms are developed for two different deployments: residential and enterprise.

Residential femtocell deployment typically refers to single-femto deployment in a consumer’s home or apartment, whereas enterprise femtocell deployment generally refers to multi-femto deployments such as enterprise buildings, small offices, and shopping malls.

For enterprise femtocell deployments, a framework of coverage planning and Tx power calibration based on technician assistance is developed. A distributed algorithm for multi-femto transmit power calibration has been designed to provide good femtocell coverage indoors and within the enterprise with minimal leakage to outdoors and outside the enterprise.

For residential deployments, an adaptive scheme to calibrate Tx power using feedback from home and macro users is developed. Further, to protect nearby active macro users, an algorithm has also been developed to throttle femtocell Tx power in real-time by detecting the presence of such users.