Maximizing Utilization of Finite 3G Spectrum by Adding a 9th Carrier

The Situation

The wireless industry is transitioning again, moving from 3G to 4G. All major operators have strategies to deploy new higher speed 4G network architectures, with many already underway deploying LTE and WiMAX. At the same time 3G networks will continue to carry voice traffic and provide coverage where 4G is yet to be deployed. This will be the case for a few more years.

The capital investment needed to implement 4G is enormous, and wireless operators must balance building new networks against support and maintenance of existing 3G networks. Investment in 3G is purposely limited while 4G is deployed, so getting more use out of finite 3G spectrum is essential for wireless operators today. Maximizing 3G networks through optimization means more capital will be available for 4G.

The evolution of networks from analog to digital has resulted in the following challenges:

  • A and B adjacent channel interference has become more acute
  • CDMA and W-CDMA must coexist in the allocated spectrum
  • Legacy GSM, EDGE and GPRS need to fit as well

The Resolution

The use of intelligent, adaptive spectrum conditioning on the base station transceivers, with the ability to selectively reject interfering uplink signals, can substantially reduce the amount of spectrum wasted due to ingress, roll-off and interference, and can instead be used to permit more carriers, more calls, and more data throughput. These capabilities are features of ISCO's Proteus® with PurePass® RF Digital Signal Processing.

A major U.S. wireless company used Proteus® to add a 9th carrier. RF energy from a competing operator's adjacent GSM traffic was suppressed and additional cross border in-band co-channel GSM hopping interference was mitigated. The 9th carrier was turned up and immediately started carrier traffic at similar levels to the other 8 carriers. During peak business hours, capacity was increased by 12%.

Infrastructure Details

Proteus® sits on the receive path digitizing 25MHz of defined RF spectrum. The digitized representation of the RF signal is analyzed by the PurePass® proprietary signal processing algorithm. After processing, the clean signal and conditioned 25MHz block of spectrum is converted back to RF and passed on to the base station. The operator uses the LCD touch screen or web interface to configure the unit. Configuration parameters adjust center frequencies, bandwidth of the band reject filter and the state of adaptive interference mitigation.

Through the use of PurePass® features — Carrier Select Conditioning, Adaptive Interference Mitigation and User Defined Band Rejection — adjacent RF power is canceled, in-band co-channel interference is mitigated and base station selectivity is improved. Proteus® adds capacity, recovers lost capacity, and improves performance.