Abstract: Embodiments describe synchronizing access routers with wireless terminal state information. According to an embodiment is a wireless terminal that transmits a message that includes an address for at least two access routers. State change information can optionally be included in the message. According to another embodiment is an access router that receives a state change notification from a wireless device or another access router. The state change notification is updated in the access router. An acknowledgment confirming the updated state change may be sent to the wireless terminal. Dynamic state synchronization is provided with minimal communication with wireless terminal.

Abstract: Scheduling of regular signal transmissions, e.g., between a plurality of wireless terminals and a base station in a cellular network in a manner designed to reduce or minimize recurring periodic interference encountered by individual wireless terminals from transmission in neighboring cells is described. Signal transmissions of wireless terminals in each cell are scheduled on a group slot basis. A group slot comprises a number of time slots. Each wireless terminal serviced by a particular base station is assigned a time slot in a group slot used by the particular base station. A given wireless terminal is assigned different time slots in successive group slots as specified by a hopping function. Adjacent, base stations e.g., base stations of physically neighboring or overlapping cells, use distinct, i.e., different, hopping functions for the scheduling purpose thereby avoiding correlation of slots between overlapping or adjacent cells during consecutive group slots.

Abstract: Methods and apparatus for performing amplitude and phase imbalance correction operations on in-phase and quadrature phase signal components corresponding to a received signal are described. The imbalance correction operations relay on the use of relatively simple to implement feedback loops. The phase imbalance feedback loop relies on the tendency of transmitted symbols to be distributed uniformly around the origin of the I/Q plane if proper phase balance is present in the processed signal. Phase correction coefficients are generated over time as a function of the negated product of the processed in-phase and quadrature phase signal components. Amplitude correction coefficients are generated over time as a function of the difference in the squared values of the I and Q processed signal components.

Abstract: More efficient utilization of available bandwidth is implemented in an OFDM wireless communication system. The partitions of bandwidth may be of different sizes and may be different from the original system design parameters. Basic system structure such as the number of tones used and the number of OFDM symbol times in a slot is maintained throughout the system. Bandwidth is varied by adjusting the inter-tone spacing or bandwidth associated with a single tone. As the inter-tone spacing is increased, the OFDM symbol transmission time is decreased following an inverse proportional relationship. A first base station transmitter transmits signals on a first number of tones distributed uniformly in a first frequency band, and a second base station transmitter transmits signals on a second number of tones distributed uniformly in a second frequency band which is wider than the first frequency band, the second number of tones being the same as the first number of tones.

Abstract: More efficient utilization of available bandwidth is implemented in an OFDM wireless communication system. The partitions of bandwidth may be of different sizes and may be different from the original system design parameters. Basic system structure such as the number of tones used and the number of OFDM symbol times in a slot is maintained throughout the system. Bandwidth is varied by adjusting the inter-tone spacing or bandwidth associated with a single tone. As the inter-tone spacing is increased, the OFDM symbol transmission time is decreased following an inverse proportional relationship.

Abstract: Improved beacon signaling methods are described. Beacon signals are transmitted on the same tone in at least two consecutive symbol periods facilitating accurate energy measurements over a symbol period even if timing synchronization with the transmitter is not maintained. A low power wideband signal is also combined with the beacon signal to facilitate channel estimation and other operations such as timing synchronization operations.

Abstract: Scheduling of regular signal transmissions, e.g., between a plurality of wireless terminals and a base station in a cellular network in a manner designed to reduce or minimize recurring periodic interference encountered by individual wireless terminals from transmission in neighboring cells is described. Signal transmissions of wireless terminals in each cell are scheduled on a group slot basis. A group slot comprises a number of time slots. Each wireless terminal serviced by a particular base station is assigned a time slot in a group slot used by the particular base station. A given wireless terminal is assigned different time slots in successive group slots as specified by a hopping function. Adjacent, base stations e.g., base stations of physically neighboring or overlapping cells, use distinct, i.e., different, hopping functions for the scheduling purpose thereby avoiding correlation of slots between overlapping or adjacent cells during consecutive group slots.

Abstract: Methods and apparatus for allocating tones for communications purposes in adjoining cells of an OFDM system are described. Tones used in each cell are allocated to tone hopping sequences according to a tone to tone hopping sequence allocation function. Different cells use different tone to tone hopping sequence allocation functions to minimize the number of collisions between hopping sequences of neighboring cells. Tone hopping sequence to communications channel allocation functions are used to allocate tone hopping sequences to communications channels. Communications channels are used by wireless terminals, e.g., mobile nodes, to transmit data. Over time, a wireless terminal uses the tones included in the tone hopping sequences corresponding to communications channels it is authorized to use. Accordingly, tones are assigned to communications devices by a multi-function, e.g., two level, mapping operation.

Abstract: A system and method for adjusting the phase of the analog signal produced by an analog modem connected to a digital modem over a telephone network. The digital portion of the telephone network is locked to the network clock, and the modems have no control over the sampling timing or rate as the analog signal is sampled and quantized by a codec. If the analog signal is shifted in phase relative to the network clock, then the codec may be sampling at unresolvable points on the analog signal, thereby causing errors and a decrease in the usable bandwidth for transmitting data. The analog modem symbol frequency is locked to the clock of the digital network using loop-back timing. A phase estimate is computed using the quantized samples of a known reference signal. Next, a “phase offset” is calculated by comparing the phase estimate to an optimum phase value. Then the digital modem sends the calculated phase offset information to the analog modem.

Abstract: Methods and apparatus for performing amplitude and phase imbalance correction operations on in-phase and quadrature phase signal components corresponding to a received signal are described. The imbalance correction operations relay on the use of relatively simple to implement feedback loops. The phase imbalance feedback loop relies on the tendency of transmitted symbols to be distributed uniformly around the origin of the I/Q plane if proper phase balance is present in the processed signal. Phase correction coefficients are generated over time as a function of the negated product of the processed in-phase and quadrature phase signal components. Amplitude correction coefficients are generated over time as a function of the difference in the squared values of the I and Q processed signal components.

Abstract: Frames including a packet boundary information field indicator and, optionally, packet boundary information field in addition to packet data are described. Methods and apparatus for generating and using such frames are also described. The packet boundary indicator indicates the presence or absence of at least one packet boundary information field in the frame. Frames with a payload that is fully occupied with data corresponding to a single packet do not include a packet boundary information field. The packet boundary information field indicates the location of a corresponding packet boundary and the type of boundary. One packet boundary information field is included in a frame for each boundary separating the data corresponding to different packets. By using packet boundary information fields to specify the location of packet boundaries, the need to parse an entire packet to identify the location of a packet boundary is avoided.

Abstract: Scheduling of regular signal transmissions, e.g., between a plurality of wireless terminals and a base station in a cellular network in a manner designed to reduce or minimize recurring periodic interference encountered by individual wireless terminals from transmission in neighboring cells is described. Signal transmissions of wireless terminals in each cell are scheduled on a group slot basis. A group slot comprises a number of time slots. Each wireless terminal serviced by a particular base station is assigned a time slot in a group slot used by the particular base station. A given wireless terminal is assigned different time slots in successive group slots as specified by a hopping function. Adjacent, base stations e.g., base stations of physically neighboring or overlapping cells, use distinct, i.e., different, hopping functions for the scheduling purpose thereby avoiding correlation of slots between overlapping or adjacent cells during consecutive group slots.

Abstract: Symbol timing synchronization in OFDM communication systems where multiple wireless terminals communicate with a single base station is described. Base station transmitter and receiver symbol timing is fixed. Each wireless terminal operates to independently adjust its transmitter timing. Transmitter timing synchronization at the wireless terminal is slaved to the terminal's receiver timing synchronization. Each wireless terminal first corrects its receiver symbol timing based on a signal received from the base station. The wireless terminal then adjusts its transmitter symbol timing as a function of its receiver symbol timing. When the receiver symbol timing is to be advanced or delayed by some amount, the transmitter symbol timing is also advanced or delayed, respectively, by the same, or substantially the same, amount. Symbol timing adjustment can be made by adding or deleting digital samples from the first or last symbol in a dwell.

Abstract: A method and apparatus for determining the correct decision regions in a PCM communication receiver utilizing a public Digital Telephone Network (DTN). A receiver receives samples from an analog loop of the DTN and quantizes the samples according to a reference lattice. The reference lattice defines a set of decision levels representing the quantization level for each PCM codeword. The receiver sets the reference lattice by scaling the lattice to account for the characteristics of the communication channel, which typically includes distortions of the digital data resulting in nonlinear behavior of the channel. The scaling and re-scaling thus accounts for PCM codeword translations or other channel distortion.

Abstract: A signal for exception processing is provided. The signal includes a first sequence of PCM codewords. Each PCM codeword in the sequence has a magnitude corresponding to a maximum point within an active constellation. The signal further includes a timing mark following the first sequence. In addition, a client device is provided. The client device includes a receiver and a detector coupled to the receiver. The receiver is coupled to an analog subscriber loop and has a decision feedback equalizer. The receiver provides a decision corresponding to data sent by a digital data source. The detector monitors the decision of the receiver to determine when an exception has been requested by the digital data source. Further, a method of requesting a change in a mode of operation of a client device when the client device is operating in a data mode is provided. The data mode includes receiving signal points selected from an active constellation and deciding which points have been received to thereby recover data.

Abstract: Apparatus and methods of compensating for distortions introduced in communication signals received over a telephone network. An adaptive linear equalizer (LE) pre-filter is used for filtering incoming sampled communication signals received via the telephone network transmission medium. An adaptive decision feedback equalizer (DFE) is used in conjunction with the LE to provide error filtering as a hybrid equalizer system to determine which of a plurality of communication states of the sampled communication signals as an accurate estimate of the originally transmitted signals over the transmission medium, responsive to the filtered communication signals from the LE. An error signal is generated relative to the difference between the determined states of the decision mechanism of the DFE and the filtered communication signals from the LE.

Abstract: A system and method for shifting the relative phases of a PCM data frame and a network RBS frame by one or more symbols is disclosed. The method includes determining whether or not RBS is present. If RBS is present, the slots affected by RBS are identified. Next it is determined what data slots, if any, are affected by encoding. The PCM data frame is shifted so the RBS constraint and the encoding constraint do not coincide at any particular data slot. For one particular PCM upstream modulation scheme, the digital modem adjusts the relative phases of the data-mode frame and network RBS frame such that a minimum number of trellis-modified symbols fall on network RBS affected slots. This information is transmitted to an analog modem. The amount of shift can be conveyed to an analog modem in the same data sequence used to send upstream constellation sets and mapping parameters during an initial training sequence.

Abstract: The present invention provides a method of generating a signal that may be used to determine the characteristic response of a communication channel that utilizes the public Digital Telephone Network (DTN). The channel includes the DTN, which may have Network Digital Attenuators (NDA) and/or Robbed Bit Signalling (RBS), and a Digital-to-Analog Converter (DAC), (also known as a codec), as well as the analog characteristics of the local loop, typically a twisted pair of copper wires. The present invention provides a method and apparatus to determine the optimal sampling instant of the received data stream. The present invention provides a probing signal that is well-suited for use in determining the channel's response to a known sequence of PCM codes used as data symbols. This is especially useful in so-called PCM modulation schemes that utilize the DTN, where knowledge of network and DAC distortion predicates the selection of available PCM codes used to represent data.

Abstract: The present invention provides a method of generating a signal that may be used to determine the characteristic response of a communication channel that utilizes the public Digital Telephone Network (DTN). The channel includes the DTN, which may have Network Digital Attenuators (NDA) and/or Robbed Bit Signalling (RBS), and a Digital-to-Analog Converter (DAC), (also known as a codec), as well as the analog characteristics of the local loop, typically a twisted pair of copper wires. The present invention provides a method and apparatus to determine the optimal sampling instant of the received data stream. The present invention provides a probing signal that is well-suited for use in determining the channel's response to a known sequence of PCM codes used as data symbols. This is especially useful in so-called PCM modulation schemes that utilize the DTN, where knowledge of network and DAC distortion predicates the selection of available PCM codes used to represent data.

Abstract: The present invention provides a method of generating a signal that may be used to determine the characteristic response of a communication channel that utilizes the public Digital Telephone Network (DTN). The channel includes the DTN, which may have Network Digital Attenuators (NDA) and/or Robbed Bit Signalling (RBS), and a Digital-to-Analog Converter (DAC), (also known as a codec), as well as the analog characteristics of the local loop, typically a twisted pair of copper wires. The present invention provides a method and apparatus to determine the optimal sampling instant of the received data stream. The present invention provides a probing signal that is well-suited for use in determining the channel's response to a known sequence of PCM codes used as data symbols. This is especially useful in so-called PCM modulation schemes that utilize the DTN, where knowledge of network and DAC distortion predicates the selection of available PCM codes used to represent data.