Abstract: In order to achieve reliable and efficient communication over public switched telephone networks (PSTN), voice-band modems utilize sophisticated start-up procedures. This invention involves a start-up procedure that allows an analog modem and a digital modem to establish a dial-up connection that utilizes PCM modulation in both upstream and downstream directions for data transmission.

Abstract: In a PCM modem system, a method and apparatus for optimizing the fractional sampling phase offset in the upstream direction to maximize the upstream data rate utilizes a probing signal from the analog modem generated during startup and having at least two distinct phases of a pure tone, with the probing signal being detected at the digital modem where an optimum sampling phase value is calculated. From this calculated value, a signal representing the appropriate amount to delay the input data stream is transmitted back to the analog modem for adjustment of the fractional sampling phase so that the fractional sampling phase offset at the central office quantizer is optimized.

Abstract: A method and apparatus is provided that dynamically allocates processor resources to data transfer-related operations, minimizing the processor resources used for data transfer-related operations and maximizing the processor resources available for other applications. The apparatus comprises a communication device (104), comprising a processing unit (204) and a complexity controller (206), which communication device (104) is capable of executing multiple data transfer-related operations and is highly configurable. The complexity controller (206) monitors a condition of a communication channel (102) and determines the best configuration of communication device (104) in regard to processor resource utilization to meet a given Quality of Service requirement for the condition of channel (102) and to maximize the processor resources available for other applications, such as data terminal equipment user applications (108) or signal processing by other communication devices using the same host processor.

Abstract: In a PCM modem system in which equivalence classes are used to communicate information from a transmitter to a receiver, a method is provided to solve the problem of 180° phase reversals in the communications channel which result in a garbled transmission. This is accomplished by remapping the equivalence classes into a form that can be differentially encoded and decoded such that equivalence class identity is not lost during a phase reversal of the channel.

Abstract: In a full duplex PCM modem system, a method and apparatus is provided for robust measuring of the communications channel in which the digital modem's transmitter is silenced during generation of training signals by the analog modem, with the silencing of the digital modem's transmitter eliminating problems associated with echo during channel measurement at the digital modem. The above method thus eliminates echo during channel estimation and removes any dependencies on the performance of the echo canceller normally used.

Abstract: A method and apparatus for achieving the fastest possible data transmission rate, symmetric, near symmetric, or a specific data transmission rate between multiple analog modems. The invention comprises a multimedia unit comprising of two (or more) digital modems and a controller section. The controller provides the interface between the two (or more) digital modems. When a user attempts to send data from a first analog modem to a second analog modem, the user calls the first digital modem in the network. Next, the first digital modem establishes a connection with the second digital modem through the controller section which is partitioned in two segments. Controller segments may be co-located or located in different locations and connected through either Internet or PSTN. Then, the second digital modem dials up the second analog modem under direction of the controller.

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.