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Analog-Digital Hybrid Modulation
for improved efficiency over Broadband Wireless Systems
This paper seeks to present ways to eliminate the inherent quantization
noise component in digital communications, instead of conventionally
making it minimal. It deals with a new concept of signaling called the
Signal Code Modulation (SCM) Technique. The primary analog signal is
represented by: a sample which is quantized and encoded digitally, and an
analog component, which is a function of the quantization component of the
digital sample. The advantages of such a system are two sided offering
advantages of both analog and digital signaling. The presence of the
analog residual allows for the system performance to improve when excess
channel SNR is available. The digital component provides increased SNR and
makes it possible for coding to be employed to achieve near error-free
transmission.
we introduce the concept of Signal Code Modulation (SCM) which utilizes
both the analog, as well as, digital modulation techniques. The primary
analog input signal is sampled at the appropriate rate and quantized. The
digital samples are denoted by symbols D. The resulting D symbols are then
transmitted using digital transmission techniques (like QAM) optimized for
that channel. Those D symbols represent N bits per analog input sample.
The quantization residual, which is not left behind, is transmitted over
the noisy channel as an analog symbol A, corresponding to the digital
symbol D,To produce the quantization error A, the quantized data is
converted back into analog form and subtracted from the original analog
input signal. This symbol A, for noise immunity, is amplified by a gain of
2N (or any proportional factor that will optimize the voltage swing of the
signal with that of the channel).
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