Sub-band Division Multiplexing for Wired, Wireless High-Speed Data Transmission
August 24, 2005
Broadband Physics demonstrated native 100-Mbps transmission over cable using 12 MHz of spectrum and its SDM technology at CableLabs' annual Summer Conference., according to a recent news release. SDM, (sub-band division multiplexing) is an interesting technology. It appears it could be a competitor to OFDM for cable, DSL and even wireless applications. SDM is based on the application of wavelet mathematics for multi-sub-band signaling. SDM works by transmitting wavelet filtered impulses in a large number of specific sub-bands. The multiple sub-bands of impulses can be overlapped and combined to efficiently make use of available spectrum. Individual sub-bands, however, can be turned off when needed to avoid interference. Broadband Physics reports that SDM competes favorably with QAM, DMT and OFDM modulation, as the impulses are orthogonal in both frequency and time, can handle real-world non-linearity without an equalizer, and do not require a cyclic prefix or raised cosine filter. See the online SDM Wavelet University for an animated presentation of how the system works. This is very interesting technology with many potential applications for both wired and wireless systems. The Web site notes that the company has no products for sale at this time, but reports that its silicon systems architecture is 100 percent compatible with that used by QAM systems today and should not cost any more to manufacture than QAM systems. Broadband Physics, whose motto is "Innovation through Mathematics" was formerly called Rainmaker Technologies. The initial focus of the company is to provide fiber optic speeds over existing last mile broadband access network infrastructure.
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