Electronic Design

GSM Gets A Lift From Single-Antenna Interference Cancellation Software

It may be hard to believe, but software—not hardware—can bring huge gains in cell-phone performance and efficiency. Philips Semiconductors recently started rolling out its own version of a new software technology known as single-antenna interference cancellation (SAIC).

Called mono interference cancellation (MIC), it consists of new DSP software that's added to the baseband part of the handset. It mitigates co-channel interference, which occurs when a handset receives an unwanted signal from a neighboring cell on the same channel. The unwanted signal reduces speech quality, causes dropouts, and reduces data-transfer rates with GPRS. This problem is common in GSM systems where traffic is heavy.

While GSM provides methods like frequency hopping, power control, discontinuous transmission, and adaptive multirate coding, these techniques have come up short in completely solving the co-channel interference problem. Multiantenna, multitransceiver systems have been developed to fix the problem, but there's a price penalty when changing the system.

To fix the problem, MIC adds software to the handset. A MIC handset uses DSP software that can distinguish between the desired signal and the interfering signal, as well as select the correct one even if both desired and interfering signals are equal in strength. The DSP algorithm essentially subtracts out the interfering signal.

Fixing the co-channel interference problem results in enhanced voice quality, fewer dropped calls, and more GSM system voice capacity. MIC also works with all GPRS modes and the lower four coding schemes of EDGE. This creates higher download speeds for e-mail and Internet access.

In recent tests with wireless carrier Cingular, MIC showed a 20% increase in voice capacity and GPRS throughput. Philips expects SAIC to be included in Release 6 of the 3GPP standards. 3GPP is an international standards organization that's developing evolving solutions for GSM to UMTS 3G systems. Philips is open to licensing all interested parties.

TAGS: Digital ICs
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