Abstract: In transmitting information over a cellular communications channel to an opposite endpoint, a modem's autorating routine is "data-driven." In particular, when the amount of information to transmit to the opposite endpoint is low, the modem's data rate is low e.g., 4800 bps, and the modem's ability to autorate upwards, i.e., fallforward, is disabled. However, when the amount of information to transmit to the opposite endpoint is high the modem's ability to fallforward is enabled so that the modem's data rate can increase to the highest permissible data rate for the cellular channel in order to transmit large blocks of information.

Abstract: A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). The hybrid DFE structure is designed so that one form of tap values dominates over the other. This allows only the dominate tap values to be used by the transmitter during precoding and reduces the transmitter complexity. In particular, a hybrid DFE is designed so that the I(z) coefficient values dominate over the N(z) coefficient values, where the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively. A respective Tomlinson precoding scheme in the transmitter uses only the I(z) values. Since only the I(z) values are used in the precoder of the transmitter, the NP-DFE of the receiver is kept active during the communications phase.

Abstract: Intersymbol interference and precoding loss are minimized by combining the precoding and coding operations. An intersymbol interference coder uses a feedback loop to apply a dither sequence to a sequence of input signal points. The dither signal applied to each input signal point is a function of the previous signal points in the sequence. The intersymbol interference coder implements, for example, a trellis coding operation by selecting one of several different modulo operations to determine the magnitude of the dither signal, the selection being made in response to the current trellis state. The sequence of signal points output from the intersymbol interference coder generates a valid sequence of the trellis code input to the Viterbi decoder.

Abstract: A mobile phone includes a modem, hereinafter referred to as a cellular radio modem. This cellular radio modem supports two modes of operation--an analog mode, where the cellular radio modem provides an analog signal for transmission; and a digital mode, where the cellular radio modem provides a digital bit stream for transmission. During operation, i.e., the existence of a data connection to a far-end modem, the cellular radio modem is alerted by the cellular network to switch to the appropriate mode--analog or digital. The cellular radio modem then switches and continues transmission in the new mode. In this embodiment, the far-end modem is part of a modem-pool located within the Mobile Telecommunications Switching Office of the cellular network. The far-end modem automatically detects this switch by the cellular radio modem and itself switches to the appropriate mode.

Abstract: Some data communications networks employ the use of both a leased line and a dial-up line between two modems. Typically, the dial-up line provides a backup capability when the leased line causes a degradation in the signal quality of the data signal. This degradation of the signal quality of the data signal is detected by one of the two modems, which then automatically establishes a data connection over the dial-up line. However, it is preferable to switch back to the leased line as soon as possible since the leased line usually costs less than the dial-up line. Therefore, in order to test the leased line, the entire data signal is simultaneously transmitted on both the dial-up line and the leased line. The use of the existing data signal to test the leased line's effect on signal quality allows the modem to perform a more complete analysis of the returned data signal so that a premature transition back to the leased line does not occur.

Abstract: A simultaneous voice and data modem performs "voice-activated" data rate changes to improve the transmission quality of the voice signal. In particular, when the simultaneous voice and data modem detects that a local telephone set has gone "off-hook," the simultaneous voice and data modem selects a signal space with a lower symbol density, which, although resulting in fewer bits per symbol, provides for a higher quality voice transmission.

Abstract: In a simultaneous voice and data communications system, a voice signal is mapped into an N-dimensional signal space constellation as a vector, and added to a reference signal point, i.e., a data symbol, where the data symbol is selected from a constellation of data symbols every signaling interval as a function of a data signal. The constellation signal space is further divided into a number of shaped regions, where each region is associated with a different one of the data symbols. The shape of each region is selected as a function of the characteristics of the voice, or audio, signal. In particular, each region illustratively has a rectangular shape.

Abstract: A monolithic array of surface emitting lasers is used in a printer engine to illuminate a photosensitive surface.

Abstract: In a mobile data communications system, a near-end modem initiates a data connection to a far-end modem at the highest permissible data rate, e.g., at 9600 bits per second (bps). If the communications channel subsequently degrades, either the near-end modem, or the far-end modem, initiates an autorate, or fallback sequence, e.g., to 4800 bps. However, if channel performance is still poor at 4800 bps, then one, or both, of the modems initiate a fallback to 1200 bps--skipping over the data rate of 2400 bps, which is not included within the fallback sequence.

Abstract: In a multidrop data communication system operating at a first bit rate using the High-Level Data Link Control (HDLC) protocol, dial restoral of communications with a particular tributary at a second, lower bit rate is accomplished without requiring the system as a whole to back down to that lower bit rate. Specifically, the outgoing data is buffered in the dial restoral modem, which discards the data stored in the buffer upon receipt of the HDLC frame which follows any frame in which the so-called "poll" bit is set.

Abstract: The Transmission Control Protocol (TCP) is a connection-oriented transport layer protocol that offers a full duplex reliable virtual circuit connection between two endpoints. Each received TCP packet in an endpoint contains both control information and data. The complexity of processing this control information in an endpoint is reduced by only periodically processing the control information. In particular, control information in received packets are not processed in an endpoint until either a) a predetermined number of packets are received, or b) a timer expires, whichever occurs first. As a result, this overall decreases the amount of processing associated with the receipt of each TCP packet and improves the performance of the TCP protocol in a high-speed packet network.

Abstract: Announcements from a voice messaging system that either prompt a user for action or provide information to a user are constructed independent of the language in which the announcement is provided to the user. In particular, each announcement is treated as a "semantic expression" having an announcement identifier. This announcement identifier is mapped into a plurality of rules, each rule providing instructions on how to construct the announcement for a particular language. The rules can recursively call other rules to provide additional flexibility in constructing a particular announcement.

Abstract: The Electronic Industry Association (EIA) RS-232 interface signals are manipulated to additionally convey operating mode information from a piece of data communications equipment (DCE) to its respective data terminal equipment (DTE). In particular, in establishing a data connection, the data communications equipment may transmit information in either half-duplex mode or full-duplex mode. In order to convey which mode of transmission is being used, the data communications equipment manipulates the EIA RS-232 interface signals to provide a notification signal, which is representative of the particular mode, to the data terminal equipment. As a result of receiving this notification signal, the data terminal equipment can then switch to the same mode of operation.

Abstract: A high-speed convolutional decoder is constructed by performing the transition, or branch, metric calculations in reference to a subset of a constellation, which comprises a plurality of subsets. In addition, any subset can be chosen as the reference subset through the use of "modulo decoding." In a modulo decoder, the constellation space is folded into a modulo set area that is centered around the arbitrarily chosen reference subset. The branch, or transition, metrics are calculated within the modulo set area. As a result, the branch metric computations are only performed on a small area of the signal space, with the result that only one error is extracted, the branch metrics are easily computed, and one slicing is performed--thus reducing overall computation time.

Abstract: In many data communications systems, crosstalk is a significant channel impairment. If all transmitters in such a system must utilize the same shaping function, and if the transmitters are furthermore nominally Nyquist bandlimited, then the crosstalk generally cannot be mitigated by equalization. However, by extending the bandwidth of the transmitted signal in accordance with the principles of the invention, the resultant crosstalk can be efficiently mitigated by equalization. This extended bandwidth signal is produced by adding significant additional energy outside the traditional Nyquist band.

Abstract: In a time-division multiplexing communications system, which transmits information from various sources in different time-slots, additional information is transmitted by varying the pattern of time slot assignments in accordance with a set of rules. As a result, the assignment pattern by which time slots are assigned to each of the various sources of information, conveys additional information. Specifically, a High Definition Television (HDTV) transmission system is constructed in which picture information is transmitted by time-division-multiplexing between two different, and disjoint, signal point constellations. Additional information is conveyed by the rule for switching between the different signal point constellations.

Abstract: The data entry portion of a voice messaging system is constructed to be language, culture, or market segment independent. In particular, the design of the voice messaging system is based upon "semantic expressions," which are used to evaluate any language, culture, or market specific data that is entered by a user. In particular, each type of data entry is treated as a "semantic expression" having an identifier. This identifier is mapped into a plurality of rules, each rule providing instructions on how to interpret the input data for a particular language, culture, or market segment. The rules can recursively call other rules to provide additional flexibility in interpreting information that is entered by a user.

Abstract: A V.32 compatible modem provides a full-duplex mode of operation, while a 208B compatible modem provides a half-duplex mode of operation. The connect sequence of a V.32 compatible modem is modified so that it will automatically determine if the other modem, whether the originating modem or the answering modem, is a 208B type of modem or a V.32 type of modem. In one embodiment of the invention, the connect sequence of an originating V.32 modem is modified to detect either a 2100 Hz answer tone, which represents that the answering modem is a V.32 type of modem, or a 2021 Hz answer tone, which represents that the answering modem is a 208B type of modem. In another embodiment of the invention, the connect sequence of an answering V.32 modem is modified to transmit first a 2100 Hz answer tone and then, if no 1800 Hz V.32 signal "AA" is received from the originating modem, to transmit a 2021 Hz answer tone, thereby simulating a 208B modem has answered the data call.

Abstract: A business performs a credit check on a customer's credit card number by utilizing the D-channel of an Integrated Services Digital Network (ISDN) facility. The ISDN facility connects the business to a telecommunications network, which utilizes signaling system number 7 (SS7). Specifically, the ISDN Q.931 protocol is modified to allow the Q.931 FACILITY message to include: a) credit check request, b) a call reference number, and c) the customer's credit card number. This information is sent, via the ISDN D-channel, to the telecommunications network, which passes the information, via an SS7 Transaction Capability Application Part (TCAP) message, to a credit checking data base. A result from the credit checking data based is then passed back through the telecommunications network to the business on the D-channel of the ISDN facility.