CUPERTINO, Calif. — Broadband Physics Inc. has been awarded another patent by the U.S. Patent Office extending its novel approach of using wavelet mathematics for sub-band division multiplexing (SDM), a signal transmission modulation method announced by the fabless start-up earlier this month.
Patent No 6,523,256, "Method and Apparatus for Signal Transmission And Reception," is the sixth awarded to the company since 1994.
SDM is a multi-band approach which divides the frequency spectrum into sub-bands that are inherently highly independent from each other. The processing is at baseband and can be applied to both wired and wireless media.
The company, formerly known as Rainmaker Technologies Inc., said SDM is an efficient, robust and highly flexible scheme for "delivering digital channel capacities well in excess of today's methods at today's or better prices." It claimed the modulation scheme can turn a 30 Mbit/s pipe into one capable of operating at 180 Mbit/s or even higher data rate.
Though the technique has applications in wireless networks as well, the initial focus is on broadband and cable communications.
The company demonstrated working laboratory silicon prototypes last year and has now entered a "technical execution" phase, which includes testing the technology in the field. Field trials are planned with unnamed equipment suppliers and service providers in the near future.
"Broadband Physics is committed to standardize SDM for applications that select SDM as the preferred signal transmission method", said chief executive Mark Launch.
The technique used at Broadband Physics is based on the novel application of wavelet mathematics for information signaling. The underlying principle of using wavelet math produces an inherent multi-sub-band system. The transmitter for each sub-band is a filter that takes digital data and spreads the information over a wavelet impulse. Each sub-band receiver is an equivalent filter which converts the wavelet impulse back to digital data.
In this way, one filter is used per sub-band to generate the transmission wavelet impulse signal and a corresponding filter is used to decode the impulse.
Each sub-band operates in the same manner, but with an offset frequency which is orthogonally related to the other sub-bands. One signaling symbol consists of the sum of the wavelet impulses from all active sub-bands.
At the receiver, each sub-band is initially recovered by use of a finite impulse response (FIR) filter. Each sub-band's FIR filter can be constructed from digital logic or through the use of a passive surface acoustic wave filter. From there, a digital equalizer and other logic reconstructs the original data.
The company says sub-band widths are sized depending on the application, be it for last mile access networks, cable or WLANs. With software control of sub-bands, both passbands and notches can be provisioned at deployment time to meet any regulatory requirements.
Changes in regulations can be accommodated with a simple software change rather than costly hardware alterations.
