US 2018/0254935 A1 · METHOD AND APPARATUS FOR LOW COMPLEXITY TRANSMISSION AND RECEPTION OF CONSTANT OR QUASI-CONSTANT ENVELOPE CONTINUOUS PHASE MODULATION WAVEFORMS

Abstract

To reflect advantages of continuous phase modulation (CPM), the invention provides a low complexity transmitter and receiver to transmit and receive CPM signals. CPM is a spectrum-efficient digital modulation scheme, which enables constant or quasi-constant envelope communication, leading to significant battery savings on top of bandwidth and energy savings. Despite the desirable properties of CPM, the complexity of an optimum CPM demodulator can be very high, due to the inherent memory nature of CPM. Specifically, the number of states in an optimum CPM demodulator is exponentially dependent on the length of the frequency pulse, L. The present invention addresses a significant reduction in the CPM demodulator complexity, and is especially well-suited for large values of L, e.g., L≥3. The invention utilizes a linear filter front end as an integral part of the CPM demodulation process so as to reduce the ISI inherent in CPM transmit signal, and minimizes the influence of L in the reception process. To that end, the invention renders the complexity of a CPM demodulator non-exponentially dependent on L, and L only has a weak impact on the number of coefficients of the linear front end filters. Moreover, the invention provides a simple way of forming CPM signals for a digital communication transmitter using parallel Time Invariant Phase Encoders, which simplifies the production of CPM waveforms on software or hardware.

Claims20

Dependent claims

A demodulator for performing low complexity coherent demodulation of constant or quasi-constant envelope Continuous Phase Modulation (CPM) signals for a baseband received signal to generate desired modulation symbol estimates, wherein the demodulator comprises:

a noise reduction filter for filtering the baseband received signal to generate received samples which are sampled at symbol time;
a bank of K linear Minimum Mean Square Error (MMSE) filters for producing CPM pseudosymbol estimates;
and
a symbol detector for performing symbol detection on the CPM pseudosymbol estimates to generate the desired modulation symbol estimates,
wherein the demodulator is compatible with all alphabet lengths (M), all modulation indexes (h), all pulse lengths (L), and all pulse types, K>1 when M>2 and the K linear MMSE filters are in parallel and combat interference for M>2 or L>1.

2 more elements

A method for low complexity coherent demodulation of constant or quasi-constant envelope Continuous Phase Modulation (CPM) signals for a baseband received signal to generate desired modulation symbol estimates, wherein the method comprises:

filtering the baseband received signal using a bank of K noise reduction filters to generate received samples which are sampled at symbol time;
performing linear filtering on the received samples using a bank of K linear Minimum Mean Square Error (MMSE) filters to produce CPM pseudosymbol estimates;
performing symbol detection on the CPM pseudosymbol estimates to generate the desired modulation symbol estimates,
wherein the method is compatible with all alphabet lengths (M), all modulation indexes (h), all pulse lengths (L), and all pulse types, K>1 when M>2 and the K linear MMSE filters are in parallel and combat interference for M>2 or L>1.

1 more element

Dependencies are inferred from the claim text.

Method and apparatus for low complexity transmission and reception of constant or quasi-constant envelope continuous phase modulation waveforms

Life of this patent

Method and apparatus for low complexity transmission and reception of constant or quasi-constant envelope continuous phase modulation waveforms

Life of this patent

Abstract

Claims20