3com Corporation

Texas Instruments Corporation

A Joseph Mueller

Richard G C Williams

Vlad Mitlin

John R Rosenlof

Richard G Williams

Yaqi Cheng

R John Rosenlof

George F Landsburg

The present invention includes methods and devices to compensate for gain and phase imbalance for OFDM and other multi-carrier symbol transmission systems. More particularly, methods and devices for determining compensation parameters are provided. This invention may be applied to a variety of standards utilizing OFDM technology, including IEEE 802.11a, Hiperlan/2 and MMAC. Further description of the invention and its embodiments are found in the figures, specification and claims that follow.

Gain and phase imbalance compensation for OFDM systems

System and method for enabling the low power detection of a transmitted sequence. A preferred embodiment comprises the replacement of a portion of a preamble (after the application of any needed scrambling) with an expected sequence field (such as the expected sequence field). The expected sequence field may contain a sequence of values known at a receiver or a periodic sequence. The addition of the expected sequence field does not affect the length of the preamble and is compatible with existing receivers. The detection of the expected sequence field may be performed with analog circuitry, allowing receivers to place digital circuitry to sleep and reduce power

Enhanced preamble to enable low power detection

The present invention includes a method for selecting appropriate forward error correction and automatic repeat request parameters for protection of a multicarrier communication channel. The multicarrier communication channel may be wired or wireless. Particular aspects of the present invention are described in the claims, specification and drawings.

Method and apparatus for selection of ARQ parameters and estimation of improved communications

A method and system for analytically and dynamically generating a repeatable digital probing signal representing an answer tone. The probing signal may conveniently be used by a modem to determine whether characteristics of the communication path between the modem and another end are sufficiently similar to these of a previous communication path, such that a shortened training sequence can be employed between two ends. When the modem initiates communication, the modem applies a predefined algorithm to dynamically generate a sequence of samples representing an answer tone signal. Next, the modem encodes the generated sequence of samples into a sequence of codewords and sends it to a second modem via a transmission path. When the second modem receives each codeword of the sequence, the second modem dynamically generates a respective codeword and compares it to the received codeword. Using the received sequence of codewords and the dynamically generated sequence of codewords, the second modem may determine whether a shortened training sequence may be employed.

Method and system for analytically computing and using an ANSpcm signal

A system and method for providing a local area network utilizing discrete multitone transceivers includes at least two discrete multitone transceivers each of which may be capable of communicating with the central office and with other discrete multitone transceivers in communication with the local area network. The local area network utilizes a set of carriers coordinated between the first discrete multitone transceiver and the second discrete multitone transceiver providing a communication link between the first discrete multitone transceiver and the second discrete multitone transceiver.

System and method for providing a local area network utilizing remote transceivers

The present invention includes methods and devices to apply predistortion to correct nonlinearities of a power amplifier in an OFDM symbol transmission system. More particularly, predistortion is patterned to take into account clipping of symbols and to match an effective input range of the predistorter with an average power output of the power amplifier. This invention may be applied to a variety of standards utilizing OFDM technology, including IEEE 802.11a, Hiperlan/2 and MMAC.

Cubic spline predistortion, algorithm and training, for a wireless LAN system

A system and method for a handshake protocol for digital subscriber line (DSL) and similar telecommunication systems that makes beneficial use of aliasing to select and decode signaling tones. In particular, the invention carefully selects signaling tones at frequencies such that higher frequency tones would alias down and coincide with specific base tones after sub-sampling. Thus, rather than filtering out higher frequencies to avoid aliasing, aliasing is exploited to use these higher frequencies. This technique would allow a receiver to detect and decode the higher frequency tones at lower frequency tone locations or bands. A related innovation is a band set, which includes one or more tones within a particular frequency band, where typically each tone in a band set corresponds to a different tone set. Exploiting the effects of aliasing eliminates the need to search for compatible spectrum, simplifies receiver design, provides flexibility, scalability and future-proofing, and allows handshaking sessions to be established across mutually exclusive spectrums. The invention is particularly useful for DSL systems, and in particular is well suited for the proposed G.hs standard.

Controlled aliasing to simplify service selection

A system and method for allowing multiple digital subscriber line modems to access a telephone line. The embodiments employ additional signaling protocols to enable equipped modems to distinguish between initiating and responding signals from initiating customer premise modems and telephone company central office devices. The additional signaling can take many forms that can be detected and used to distinguished signals. Preferably, the signal is a stealth signal as to not interfere with existing communication devices. A variety of application and embodiments are disclosed to enable a solution allowing multiple modems to access a telephone line.

Method and system for connecting multiple DSL modems to a telephone line

A method and system for escaping from a fast retrain sequence in an ADSL system, particularly in a splitterless ADSL system. In one aspect of the invention, in order to minimize the impact of needing to complete nearly all of a fast retrain sequence, particularly when the sequence is unnecessary, the invention allows a responding transceiver unit to reply to a fast retrain request from an initiating transceiver unit with an &ldquo;initialization&rdquo; response. This response, not part of any standard ADSL fast retrain protocol, aborts a fast retrain sequence, and permits initialization to commence without the delay caused by waiting for completion of the fast retrain sequence. In another aspect of the invention, a fast retrain sequence is allowed to proceed up to a certain point, and then truncated by sending a command between a responding transceiver unit and an initiating transceiver unit. In particular, whenever initialization and power cut-back are both required (a typical case in ADSL systems), a fast retrain sequence is initiated, acknowledged, and executed until the end of the power cut-back section of the conventional fast retrain sequence, at which time a digital message is exchanged between the initiating transceiver unit and responding transceiver unit indicating the desire to escape from the fast retrain sequence prematurely. Thus, the fast retrain sequence can be truncated to improve performance while still maintaining the benefits of the conventional power cut-back function.

Digital modem fast retrain escape mechanism

A system and method for generating and repetitively transmitting a single modulated symbol during idle periods in user data in a digital subscriber line (DSL) communication system. The modulated symbol to be transmitted is selected such that its spectral properties match those of user data modulated symbols. For an asynchronous DSL system, and variants thereof, a preferred idle symbol is the 'superframe' synchronization symbol. A separate modulated symbol would indicate the end of the idle state. In the preferred embodiment, the end-of-idle symbol is the idle symbol shifted by a 180.degree. phase shift. In a preferred embodiment, the transmitter in a DSL modem would calculate the idle state modulated symbol once at the start of the idle period and then simply repeat this symbol until the end of the idle period, in which case the transmitter would invert the final idle symbol. At the receiver, an idle state modulated symbol detector and phase detector are implemented. Symbol detection can be performed in the time-domain for faster and easier detection, requiring little processing power. Upon detection of a 180.degree. phase shift of the idle symbol, the receiver would exit the idle mode. The invention includes method, apparatus, and computer program implementations.

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San Diego, CA, United States of America

A Joseph Mueller