Single sideband and quadrature multiplexed continuous phase modulation

• US 20090279422A1
• Filed: 04/09/2009
• Published: 11/12/2009
• Est. Priority Date: 10/20/2005
• Status: Active Grant

• Current Assignee: Trellis Phase Communications, LP
• Original Assignee: Trellis Phase Communications, LP
• Inventors: Dowling, Eric Morgan, Fonseka, John P.
• Granted Patent: US 7,920,637 B2
• Time in Patent Office: Days
• US Class Current: 370/215
• CPC Class Codes: H04L 1/0054 Maximum-likelihood or sequential decoding, e.g. Viterbi, Fano, ZJ algorithms

Abstract

A class of bandwidth reduction techniques are used develop a broad class of modulation types collectively called SSB-FM. These signals can be used to construct communication systems that provide bandwidth-normalized performance gains of 10 dB or more when compared to popular prior art modulation methods. An aspect of the invention involves mapping trellis paths in a complex signal space onto corresponding real-valued trellis signals with desirable spectral properties. The invention can be used map continuous phase modulated (CPM) signals onto simpler amplitude-modulated trellis signals having double the channel capacity of prior art CPM signals. Multi-amplitude signaling and frequency division multiplexing may also be incorporated to further accommodate more information per symbol.

Claims

1. A transmitter apparatus, comprising:

a module that maps a first sequence of bits onto a first real valued envelope signal of the form m₁(t)=A₁ cos(α

₁(t)+θ

₁) and that maps a second sequence of bits onto a second real valued envelope signal of the form m₂(t)=A₂ cos(α

₂(t)+θ

₂), where α

₁(t) and α

₂(t) are real-valued digitized representations of continuous phase modulation phase functions, A₁, A₂, θ

₁, and θ

₂ are real numbers, and α

₁(t) and α

₂(t) are respectively related to the first and second sequences of bits and follow respective first and second sequences of phase states that are each constrained to be allowable sequences of phase states in accordance with a respective phase trellis; and

an I/Q modulator that maps the first real-valued envelope signal, m₁(t), into an in-phase channel, and maps the second real-valued envelope signal, m₂(t), into a quadrature-phase channel for transmission onto a communication channel.

2. The transmitter apparatus of claim 1, wherein the first and second real-valued envelope signals, m₁(t), m₂(t), correspond to component signals of a quadrature multiplexed continuous phase modulated (QM-CPM) signal.

3. The transmitter apparatus of claim 1, wherein transmitter apparatus is incorporated into a head end system and is used to transmit a downlink signal.

4. The transmitter apparatus of claim 3, wherein the downlink signal is a wireless signal that carries packet data.

5. The transmitter apparatus of claim 3, wherein the downlink signal is a wireline signal that carries packet data.

6. The transmitter apparatus of claim 1, wherein transmitter apparatus is incorporated into a subscriber terminal device and is used to transmit a subscriber uplink signal.

7. The transmitter apparatus of claim 6, wherein the subscriber uplink signal is a wireless signal that carries packet data.

8. The transmitter apparatus of claim 6, wherein the subscriber uplink signal is a wireline signal that carries packet data.

9. The transmitter apparatus of claim 1, wherein:

α

₁(t) is an approximation of

10. The transmitter apparatus of claim 1, wherein m₁(t) is an approximation of a real-valued envelope of a corresponding complex-valued CPM baseband signal of the form, x(t)=Ae^jα

^1(t)=A[cos(α

₁(t))+j sin(α

₁(t))].

11. The transmitter apparatus of claim 10, wherein α

₁(t) is a phase trellis signal that takes on M phase state values in the range [0,2π

] and these M phase states map to M/2 real-valued amplitude states in the signal m₁(t), where M is a positive even integer.

12. The transmitter apparatus of claim 1, wherein α

₂(t)=α

₃(t−

τ

), where τ

is a real number and α

₃(t) is computed using a same formula a used to compute α

₁(t), but with a different data sequence as input to the formula used to compute, (t).

13. A receiver apparatus, comprising:

an I/Q demodulator that receives in an in-phase channel a first real-valued envelope signal, z₁(t), and receives in a quadrature-phase channel a second real-valued envelope signal, z₂(t); and

a decoder that processes the first real-valued envelope signal, z₁(t), and performs trellis decoding thereon to discern a set of trellis paths that correspond to respective data sequences;

wherein the first and second real-valued envelope signals are respective received-signal approximations of transmitted real-valued envelope signals of the form m₁(t)=A₁ cos(α

₁(t)+θ

₁) and m₂(t)=A₂ cos(α

₂(t)+θ

₂), where α

₁(t) and α

₂(t) are real-valued digitized representations of continuous phase modulation phase functions that follow respective first and second sets of phase states, and A₁, A₂, θ

₁, and θ

₂ are real numbers.

14. The receiver apparatus of claim 13, wherein m₁(t) is a real-valued envelope representation of a corresponding complex-valued CPM baseband signal, x(t)=Ae^jα

^1(t)=A[cos(α

₁(t))+j sin(α

₁(t))].

15. A transmitter apparatus, comprising:

a first module that maps a first of set of input bits onto a first plurality of N digitized representations of real-valued continuous phase modulation phase functions, {α

_1,i(t);

i=1, . . . N}, and maps a second set of input bits onto a second plurality of N digitized representations of real-valued continuous phase modulation phase functions, {α

_2,i(t) i=1, . . . N} where N is a positive integer greater than one, and embedded into each phase function is a respective sequence of phase states that is constrained to conform to a respective allowable phase state sequence in accordance with a respective phase trellis;

a second module that maps the first and second sets of phase functions to respective first and second real valued envelope signals of the form

16. A receiver apparatus, comprising:

an I/Q demodulator that receives in an in-phase channel a first real-valued envelope signal, z₁(t), and receives in a quadrature-phase channel a second real-valued envelope signal, z₂(t); and

a decoder that processes the first real-valued envelope signal, z₁(t), and performs trellis decoding thereon to discern a set of trellis paths that correspond to respective data sequences;

wherein the first and second real-valued envelope signals are respective received-signal approximations of transmitted real-valued envelope signals of the form