Abstract: A Hybrid IMMSE-LMMSE receiver processing technique predicts performance of and selects between iterative and non-iterative decoding of symbols based on an intelligent metric. Based on a pre-specified criterion, the receiver determines if a correct first-stage decision is made or not. If a correct decision is made, then it follows iterative processing like in BLAST. Alternatively, if a wrong decision is found to have occurred, the receiver resorts to LMMSE estimation processing.

Abstract: Systems and methods for transmitting packets and controlling packet flow are provided in wireless communication systems. A time stamping technique synchronizes timers/and clocks between one or more senders and receivers in a wireless communication system. Additionally, a global acknowledgement frame carries a plurality of acknowledgement messages, such as one for each services identification (SID).

Abstract: A method of communicating across a channel includes receiving information having a known bandwidth and a known spectrum. The information is preferably in the form of a multicarrier modulated signal, e.g., a DMT signal. In one aspect, this information is received at a receiver having a reduced channel bandwidth. An aliasing spectrum can be calculated based on the known spectrum and the frequency difference between the known bandwidth and the reduced-channel bandwidth. The received information can then be modified based upon the aliasing function to compensate for alias distortion. For example, the received information can be modified by modifying the noise component or signal-to-noise ratio of the received information.

Abstract: A system for synchronizing sender sliding windows and receiver sliding windows employed in wireless packet communication is provided. The sender sliding window buffers outgoing packets to be sent to a receiver that employs a receiver sliding window to buffer incoming packets. A sender window manager manages the sender sliding window through positive acknowledgement, negative acknowledgement and/or timeout processing to facilitate synchronizing the sender sliding window with the receiver sliding window without employing synchronization messages or master/slave control. Similarly, a receiver window manager manages the receiver sliding window through sequence number analysis to facilitate synchronizing the receiver sliding window with the sender sliding window without employing synchronization messages or master/slave control.

Abstract: A resynchronization method for use in a data communication system having a first device configured to transmit data at a symbol rate to a second device. The second device includes a Reed Solomon (RS) decoder having a RS lock indicator and a Moving Picture Experts Group (MPEG) Protocol Interface (MPI) having a MPI lock indicator, wherein the RS and the MPI lock indicators are monitored. Four different states, defined by the values of the RS and MPI lock indicators, determine whether the data communication system will wait for the RS decoder and the MPI hardware block to resynchronize, whether an intermediate-subset of the channel acquisition algorithm is performed or whether the entire channel acquisition algorithm is performed. The method for resynchronization described herein recovers synchronization within a predetermined time without the layers above the physical link layer having knowledge.

Abstract: For use with a multiple-input, multiple-output (MIMO) transmitter, a signal field controller, a method of controlling signal fields and a MIMO transmitter incorporating the controller or the method. In one embodiment, the controller includes: (1) a primary signal field mode indicator configured to cause a primary signal field to indicate a presence of a supplemental signal field and provide the primary signal field to the MIMO transmitter for transmission thereby and (2) a supplemental signal field generator coupled to the primary signal field mode indicator and configured to provide a supplemental signal field to the MIMO transmitter for further transmission thereby only when the primary signal field indicates the presence.

Abstract: An apparatus (100) for computing the absolute value of a complex number includes separate squaring units (110, 115) for the real and imaginary parts. A square root unit (130) extracts the square root of the sum (120) of these squares, which is absolute value of the complex number. Each squaring unit includes one unsigned multipliers for respective least significant and two signed multipliers for respective most significant bits and a cross term. The products are aligned by shifting and summed. The square root unit employs identical processing elements, each considering two bits of the input and forming one root bit and a remainder. Each processing element compares two intermediate test variables, and selects a “1” or “0” for the root bit and the next remainder based upon this comparison. A chain of processing elements enables computation of the root to the desired precision. Alternatively, the same processing elements may be used in a recirculating manner.

Abstract: A transceiver (100) such as used in Discrete Multitone (DMT) modulation of digital signals for communication, such as in a DSL modem communications system, is described. The transceiver (100) includes a function (119) by way of which unloaded subchannels are encoded with a clip prevention signal. The clip prevention signal is derived to avoid clipping by an amplifier (18) after modulation into the time domain, upsampling, and filtering. The effects of the upsampling and filtering are considered in deriving the clip prevention signal, by considering the upsampling and filtering as a polyphase combination, and using the filter response for each phase. Frequency domain and time domain update alternatives are disclosed.

Abstract: A system for data communication is disclosed that comprises a hybrid circuit (220) that receives a signal. A switched gain circuit (204) coupled to the hybrid circuit (220) receives the signal from the hybrid circuit (220). A receiver circuit (206) coupled to the switched gain circuit (204) receives the signal from the switched gain circuit (204). The switched gain circuit (204) adjusts the power of the signal transmitted to the receiver circuit (206). More specifically, the switched gain circuit (204) detects the power of the signal received from the hybrid circuit (220), and adjusts the power of the signal transmitted to the receiver circuit (206) based upon the power of the signal received from the hybrid circuit (220). A method for data communication is disclosed. A signal is received using a hybrid circuit (220). The signal is transmitted to a switched gain circuit (204) coupled to the hybrid circuit (220). The power of the signal is adjusted using the switched gain circuit (204).

Abstract: Echo cancellation in data communication between modems utilizes analog echo cancellation to lessen reduction of usable dynamic range of the received signal at the input to the analog-to-digital converter (DAC) in the receiver. Two digital-to analog (D/A) conversions are provided in the modem's analog front end (AFE). One generates the analog signal for transmission. The other generates an analog representation of a cancellation signal that is used to electronically cancel the echo before analog-to-digital (A/D) conversion of the received signal. A preferred embodiment utilizes multiplexed DAC architecture to emulate two DACs by sharing DAC circuitry between data paths of the two D/A conversions.

Abstract: A decimated and interleaved multiplication table for finite fields as is useful in Reed-Solomon encoding computations. The generator polynomial coefficients determine the multiplication table content and ordering.

Abstract: A digital subscriber line modem (30) capable of operating with multiple transmission line profiles depending on the current transmission line characteristics of a wire line pair (20) includes an interface (212, 292) to the wire line pair (20) and a signal converter (214, 290) with a terminal coupled to the interface. An on/off-hook detector(300) drives an impedance analyzer function (304) that is able to measure transmission line parameters based on the current line characteristics of the wire line pair (20). A control logic block (310) performs the actions required to adapt to a new line conditions of the wire line pair (20) and rapidly adapt to the new on/off hook condition.

Abstract: A system for synchronizing sender sliding windows and receiver sliding windows employed in wireless packet communication is provided. The sender sliding window buffers outgoing packets to be sent to a receiver that employs a receiver sliding window to buffer incoming packets. A sender window manager manages the sender sliding window through positive acknowledgement, negative acknowledgement and/or timeout processing to facilitate synchronizing the sender sliding window with the receiver sliding window without employing synchronization messages or master/slave control. Similarly, a receiver window manager manages the receiver sliding window through sequence number analysis to facilitate synchronizing the receiver sliding window with the sender sliding window without employing synchronization messages or master/slave control.

Abstract: Systems and methods for transmitting packets and controlling packet flow are provided in wireless communication systems. A time stamping technique synchronizes timers/and clocks between one or more senders and receivers in a wireless communication system. Additionally, a global acknowledgement frame carries a plurality of acknowledgement messages, such as one for each services identification (SID).

Abstract: A method of a communicating across a channel includes receiving information having a known bandwidth and a known spectrum. The information is preferably in the form of a multicarrier modulated signal, e.g., a DMT signal. In one aspect, this information is received at a receiver having a reduced channel bandwidth. An aliasing spectrum can be calculated based on the known spectrum and the frequency difference between the known bandwidth and the reduced-channel bandwidth. The received information can then be modified based upon the aliasing function to compensate for alias distortion. For example, the received information can be modified by modifying the noise component or signal-to-noise ratio of the received information.

Abstract: A telecommunications system using DSL modems (36, 38) detects on-hook or off-hook states of a local loop telecommunications line (18). If the local loop (18) is in an off-hook state, the normal data communication rates are used. If the local loop is in an on-hook state, the unused voice band is allocated to either the upstream band and/or downstream band of the DSL modems, in order to increase data communication rates.

Abstract: A transceiver (100) such as used in Discrete Multitone (DMT) modulation of digital signals for communication, such as in a DSL modem communications system, is described. The transceiver (100) includes a function (119) by way of which unloaded subchannels are encoded with a clip prevention signal. The clip prevention signal is derived to avoid clipping by an amplifier (18) after modulation into the time domain, upsampling, and filtering. The effects of the upsampling and filtering are considered in deriving the clip prevention signal, by considering the upsampling and filtering as a polyphase combination, and using the filter response for each phase. Frequency domain and time domain update alternatives are disclosed.

Abstract: An apparatus (100) for computing the absolute value of a complex number includes separate squaring units (110, 115) for the real and imaginary parts. A square root unit (130) extracts the square root of the sum (120) of these squares, which is absolute value of the complex number. Each squaring unit includes one unsigned multipliers for respective least significant and two signed multipliers for respective most significant bits and a cross term. The products are aligned by shifting and summed. The square root unit employs identical processing elements, each considering two bits of the input and forming one root bit and a remainder. Each processing element compares two intermediate test variables, and selects a “1” or “0” for the root bit and the next remainder based upon this comparison. A chain of processing elements enables computation of the root to the desired precision. Alternatively, the same processing elements may be used in a recirculating manner.

Abstract: In a splitterless Digital Subscriber Line (DSL) modem 30, a receiver architecture (100) that permits monitoring of harmonics within the upstream channel of a DSL connection. The receiver (100) can detect the harmonics by monitoring the harmonics in some empty tones or specified tones. A threshold can be set to differ the normal noise power and harmonics power in those empty or specified tones. When a POTS device (10) coupled to same wire line pair (20) as the DSL modem (30) goes off-hook, the DSL modem (30) can switch from the normal state to an off-hook state in which the harmonics are reduced to minimum by transmitting only the upper sub-band tones of the upstream transmission channel at reduced power levels.

Abstract: A modem (55) including receive circuitry (30) implemented by way of a digital signal processor (32, 32′) is disclosed. The receive circuitry (30) operates according to a receive clock (CLKr) that is based upon the output of a free run oscillator (50). An incoming frequency multiplexed signal (f(t)) is sampled by an analog-to-digital converter (31) and demodulated by way of a Fast Fourier Transform function (36). After such demodulation, a phase rotation function (40) applies a phase shift to the demodulated signal corresponding to an estimated phase offset (&tgr;) between the receive clock (CLKr) and a pilot signal (P) transmitted by the transmitting modem; a finite impulse response filter function (42) applies a digital filter to the demodulated signal to correct for phase error based upon an estimated frequency offset (&Dgr;).