Constant envelope modulation for splitterless DSL transmission
First Claim
1. A digital subscriber line modem adapted to be coupled directly to a subscriber line, the modem being capable of simultaneous access to the subscriber line with other telephone equipment operating in a first frequency band, the modem comprising:
- a terminal for directly coupling to the subscriber line without a splitter; and
a modulator connected to the terminal, the modulator configured to provide a constant envelope modulation for a signal, the signal being transmitted over the subscriber line in a second frequency band greater than the first frequency band, wherein the constant envelope modulation technique corresponds to a non-amplitude modulation technique and utilizes frequency modulation or phase modulation, whereby the constant envelope modoulation technique is consistent enough so that intermodulation product distortion in the first frequency range does not interfere with voice communication in the first frequency band.
11 Assignments
0 Petitions
Accused Products
Abstract
A digital subscriber line (DSL) communication system that utilizes the high frequency band of a standard telephone line does not require the use of a plain old telephone service (POTS) splitter in the resident'"'"'s home, which provided isolation between the POTS frequency band (0 to 4 kHz) and the DSL frequency band. Digital signal processing techniques are utilized to adapt to varying subscriber line conditions due to POTS telephone equipment. The digital signal processing techniques eliminate the need for a splitter by reducing susceptibility to distortion due to varying subscriber line characteristics. The digital subscriber line modem utilizes constant envelope modulated signals and frequency division multiplexing, where the constant envelope modulations lessens the intermodulation distortion products due to DSL signals that are transmitted by the modem and which may result in audible noise at the POTS telephone equipment due to non-linearities of the POTS telephone equipment.
188 Citations
27 Claims
-
1. A digital subscriber line modem adapted to be coupled directly to a subscriber line, the modem being capable of simultaneous access to the subscriber line with other telephone equipment operating in a first frequency band, the modem comprising:
-
a terminal for directly coupling to the subscriber line without a splitter; and
a modulator connected to the terminal, the modulator configured to provide a constant envelope modulation for a signal, the signal being transmitted over the subscriber line in a second frequency band greater than the first frequency band, wherein the constant envelope modulation technique corresponds to a non-amplitude modulation technique and utilizes frequency modulation or phase modulation, whereby the constant envelope modoulation technique is consistent enough so that intermodulation product distortion in the first frequency range does not interfere with voice communication in the first frequency band. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A telephone communication system includes a subscriber line between a telephone central office and a remote location, the remote location being capable of transmitting and receiving both POTS signals within a first frequency band and DSL signals within a second frequency band over the subscriber line at the same time without using a splitter at the remote location, the system comprising:
-
a terminal adapted to connect to the subscriber line without a splitter; and
a modulator connected to the terminal, the modulator configured to provide a constant envelope modulation for the DSL signals, the DSL signals being transmitted over the subscriber line in the second frequency band so as to lessen an amount of interference with the POTS signals created due to non-linearities causing demodulation of the DSL signals into the first frequency band whereby the constant envelope modulation has a substantially constant envelope so that intermodulation distortion is not audibly apparent in the first frequency band. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
-
-
19. A method of providing simultaneous communication over a telephone subscriber line, the simultaneous communication including at least a first signal in a first frequency band that is either being sent to or received from a telephone, and a second signal in a second frequency band that is higher than the first frequency band, the second signal being sent from a modem, the method comprising the step of:
-
providing, by the modem, a constant envelope modulation for the second signal in the second frequency band, wherein the constant envelope modulation limits an amount of audible noise heard at the telephone, the audible noise being due to a nonlinearity in the telephone that demodulates the second signal into the first frequency band wherein the constant envelope modulation is a frequency modulation or phase modulation having a substantially constant envelope. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27)
-
Specification