OFDMA Femtocells

There could be upto 70 million Femtocells by 2012 in world. If this happens the big problem would be the interfacerence between Macro and Femtocells and also between Femtos. OFDMA (used in LTE and WiMAX both) Femtocells can handle the interference better than CDMA Femtocells duo to is Intracell interference avoiding properties and robustness to multipath.

Interfere analysis will definitely play an important part in the rollouts. If not properly manged, could result in dead zones within Macro. Power control Algorithms and Radio Resource Management strategy will help but effective Spectrum allocation technique is needed as well. The diagram above shows different approaches for subchannel allocation in OFDMA femtocells.



The Femtocells would need to be self-configurable and self-optimising. Self-configuration comes into picture when the Femto is switched on. Once the parameters are adjusted then Self-Optimisation tries to optimise these defaults into something better and more suited to the current environment. Sensing of the environment plays an important part. This diagram above shows different approaches being used by different Femtocells. The cheapest approach would of course be the measurement report approach where the phone is made to report the environment. The only problem being that whichever phone was used (automatically selected) will have considerable amount of its battery power used up.

参考：3g and 4g wireless blog