Pulse or digital communications – Synchronizers
Reexamination Certificate
2000-01-26
2004-09-28
Chin, Stephen (Department: 2634)
Pulse or digital communications
Synchronizers
C375S327000
Reexamination Certificate
active
06798855
ABSTRACT:
The increasing user acceptance as well as technological progress in the development of new broad band services—also referred to as multimedia services—lead to an increasing need for broad band transmission sources in communication networks that already exist or are to be newly installed. In order to effectively and economically realize broad band applications, particularly multimedia services making use of high data transmission rates—for example, “video on demand”, video conference, toy shopping or telebanking—, a broad band communication network, particularly a broad band offering network is required. In currently installed offering networks, the network resources available are divided onto the network termination units connected to the communication network or onto the communication terminal devices connected to the network termination units. The access of the network termination units or of the communication terminal devices to the commonly used transmission medium—for example, light waveguides or radial channel—is thereby controlled such by a transmission method that respectively only one network termination unit or communication terminal device is at least temporarily granted the access authorization.
Given an offering network realized by wireless radio channels, a plurality of network termination units—also referred to as network terminations—are connected to a base station centrally arranged in a radial cell—also referred to as radial base station. The data transmission rate—for example, an aggregate bit rate of 155 Mbit/s—available in the offering network is thereby divided onto the network termination units currently connected to the base station. In current wireless offering networks, different transmission methods respectively adapted to the required data transmission rates are utilized for the data to be transmitted in the direction of the network termination units—also referred to as the downstream direction—and for the data to be transmitted from the network termination units to the base station—also referred to as the upstream direction. Time-division multiplex or time-division multiple access method—also referred to as TDMA method—represents one transmission method utilized for the data to be transmitted in the upstream direction or the data streams to be transmitted. In this transmission method, brief signal sequences—also referred to as signal bursts—are sent to the base station in alternation by the network termination units. Access onto the transmission medium or onto the radial channel is controlled by the base station such that respectively only the network termination unit sends information or, respectively, a signal burst to the base station.
In existing offering networks with light waveguide transmission, for example in a SOAP system—Siemens Optical Advanced PON—a signal burst covering 60 bytes of digitized data or, respectively, a data frame covering 60 bytes of data—also referred to below as SOAP data frame—is transmitted in the upstream direction by a respective termination unit. The preamble of each SOAP data frame comprises 7 bytes, or by 40 bits of the preamble covering 7 bytes are provided as synchronization bits for the determination of the signal parameters of the signal bursts arriving at the receiver side. The determination of the signal parameters, i.e. the determination of the amplitude as well as of the carry and clock phase within the time available for the synchronization—40 bits here—is also referred to as “Runin”. Different wireless offering networks comprising radial channels, the data to be communicated from the network termination units to the base station, i.e. the SOAP data frame to be transmitted, is advantageously modulated onto a carrier signal at a predetermined frequency with a coherent modulation method, usually by a phase modulation method that is also referred to as Phase Shift Keying PSK. Offset quadrature four phase keying—also referred to as Offset-Quadrature-Phase-Shift-Keying OQPSK—has proven to be an advantageous modulation method for the transmission of digitally existing data via radial channels. Since the individual network termination units respectfully sending a signal burst at different points in time have different distances from the base station, the amplitude as well as the carrier and clock phase during the “Runin” must be respectively identified for each signal burst arriving at the base station. Only a very brief time interval of 258 ns during the “Runin”—corresponding to the time duration of the transmission of the 40 synchronization bits of the SOAP data frame—are thus available for the realization of a radial system having an aggregate bit rate of, for example, 155 Mbit/s for determining the signal parameters of signal bursts arriving at the base station. In particular, the carrier phase of the carrier signal transmitted burst-like must be very exactly identified for an optimum demodulation of the data transmitted via a radial channel and a synchronization must be produced for the demodulation.
U.S. Pat. No. 4,095,187 discloses a demodulator for phase-modulated carrier signals wherein an incoming, first, analog, phase-modulated carrier signal is synchronized with a second analog carrier signal generated with the assistance of a voltage-controlled oscillator allocated to the demodulator. The phase-modulated carrier signal incoming at the demodulator is demodulated and, dependent on the demodulation result, the second carrier signal locally generated in the demodulator is modulated or “re-modulated”. The phase of the incoming, phase-modulated carrier signal is compared to the phase of the re-modulated carrier signal with the assistance of a phase comparator and the voltage-controlled oscillator is driven dependent on the comparison result.
Further, U.S. Pat. No. 4,757,272 discloses a demodulator for regeneration of an analog reference carrier signal and for demodulation of a phase-modulated, four-phase PSK modulation signal that is transmitted burst-like. The four-phase PSK modulation signal transmitted burst-like comprises a preamble, whereby the preamble is at least partially modulated with a predetermined modulation symbol at the transmission side. For reception-side generation of the reference carrier signal, the received four-phase PSK modulation signal is modulated with the predetermined modulation symbol during the reception of the preamble, i.e. is inversely modulated, whereby a regenerated, analog carrier signal without phase-modulated parts is formed. The regenerated carrier signal is subsequently supplied to what are referred to as AFC means that, among other things, realize a PLL circuit arrangement. With the assistance of the AFC means, the frequency-corrected and phase-corrected reference carrier signal is derived from the regenerated carrier signal, this being subsequently forwarded to an orthogonal demodulator for demodulation of the incoming four-phase PSK modulation signal.
SUMMARY OF THE INVENTION
The present invention is based on the object of improving the synchronization for the demodulation of information or data modulated onto a carrier signal transmitted burst-like.
This object is achieved in accordance with the present invention in a method for fast synchronization of a first analog carrier signal generated at a transmitter with a second carrier signal generated in a receiver, said method comprising the steps of: at least partially modulating a preamble of said first carrier signal with a predetermined phase position at said transmitter; modulating said second carrier signal with said same predetermined phase position at said receiver; identifying a phase difference between said modulated first carrier signal and said modulated second carrier signal; and following a phase difference recognition time, correcting a phase position of said second carrier signal by said identified phase difference.
This object is also achieved in accordance with the present invention in an arrangement for fast synchronization of a first analog-carrier signal generated in a transmitter with a secon
Chin Stephen
Staas & Halsey , LLP
Williams Lawrence
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