Lucent Technologies Inc.

At&t Bell Laboratories

At+t Corp.

Agere Systems Inc.

Thomas W Goeddel

Mohsen Sarraf

Richard C Fuller

Subramanian Krishnamurthy

Martin Herzlinger

R B Heick

Robert Louis Cupo

Alex Matusevich

Tongtong Li

Sheng-Jen Tsai

Masoud Sajadieh

Jonathan Michael Tobias

Masood Yousefi

Nevio Benvenuto

Kevin K Whang

Bruce A Dautrich

David B Roe

'Reliability-related' values are assigned to received signal samples containing noise and distortion. The samples are then sent to a Viterbi decoder in order to regenerate originally transmitted messages.

Methods and devices for decoding signals containing noise and distortion

The performance of wireless devices is improved using methods and devices which comprise novel SPEED and NOISE metrics. The SPEED metric is generated from a mean value of a differential signal while the NOISE metric is generated from a variance value of a differential signal. The generation of both metrics assumes the use of a limited number of symbols used to generate the mean and variance values. One example of a signal used to generate the metrics comprises the 14 synchronization symbols which make up part of an IS-136 standard signal. The SPEED metric was discovered to comprise a value which is equal to the magnitude of the mean value of the differential signal while the NOISE metric was discovered to comprise a value which is approximately equal to twice the variance of noise in a received baseband signal, while at the same time being independent of the speed at which an object, such as a wireless device, moves. In the case where a Least Mean Square (&ldquo;LMS&rdquo;) method is used to estimate channel fading in a flat-faded channel, it was discovered that the logarithm of a ratio of the SPEED metric to the NOISE metric as plotted against optimum step sizes is a substantially linear relationship.

Methods and devices for improving the performance of wireless devices using speed and noise metrics

A phase-modulated signal such as a quadrature phase-shift-keyed (QPSK) signal in a wireless communication system is demodulated using sample timing based at least in part on frequency information generated by frequency demodulating the phase-modulated signal. The phase-modulated signal is separated into first and second portions, the first portion is phase demodulated to generate demodulated symbols, and the second portion is frequency demodulated to generate, e.g., a measure of the instantaneous frequency of the phase-modulated signal. The instantaneous frequency measure is processed to identify one or more symbol transitions, and the identified transitions are used to establish the sample timing such that proper sampling of the symbols is ensured.

Sample timing control for demodulation of phase-modulated signals

A computer implemented method and apparatus utilizing a multi-diversity synchronization technique for improving time synchronization in wireless applications, such as TDMA applications is disclosed. The multi-diversity synchronization technique utilizes cross-correlations between multiple diverse received signals to determine relative offsets between the signals. The signals are then time aligned. An absolute synchronization word location is determined using the time aligned signals and is used along with the relative offsets to determine respective synchronization word locations for each received signal in an accurate, efficient and improved manner.

Multi-diversity synchronization technique for improving synchronization performance in wireless applications over fading channels

A sequence of Quadrature Amplitude Modulated (&ldquo;QAM&rdquo;) data symbols is received and its' fading process estimated. The estimated fading process is then used to generate estimates of the identity of the symbols themselves. Instead of using the single, received sequence to complete the fading process estimates, multiple offset sequences are used. For a given signal-to-noise ratio, the resulting fading process estimates and data symbol estimates provide for reduced bit error rates.

Methods and devices for estimating QAM symbol sequences over flat fading channels using multiple offset sequences

An access platform pools a plurality of different signal processing resources, herein represented by different types of speech-coding algorithms. The access platform is coupled to the Internet, a local-exchange-carrier (LEC), and other communications facilities such as, but not limited to, a plurality of long-distance facilities provided by any one of a number of long distance carriers, e.g., AT&T. For each call through the access platform, one of the plurality of signal processing resources is allocated as a function of signal type either through signal detection or out-of-band signaling. For example, the access platform first determines if the call is an audio call or a non-audio (or data) call by detecting the type of signal. If the call is an audio call, the access platform switches in echo canceling resources. On the other hand, if the call is a data call, the access platform determines if a speech-coding algorithm is being used and, if necessary, switches in a compatible speech-coding resource.

Signal processing resource allocation for internet-based telephony

Non-intrusive monitoring and analysis of real-time facsimile transmissions is accomplished. Analog impairment measurements are made on the high speed page signal in those transmissions and protocol analysis is made on the low speed control messages in those transmissions. These measurements and analysis are a powerful tool for trouble shooting service problems afflicting facsimile transmissions. Real customer traffic can be monitored to detect circuit impairments and to evaluate service being provided. A selected incoming trunk of a central office switch is accessed and a monitoring function with respect to that trunk is established. A signal classification operation is performed, which identifies the presence of a facsimile transmission and what kind of facsimile transmission it is. When the classification operation has determined the presence and nature of a facsimile transmission, a series of non-intrusive impairment measurements is made using the page information sent in the course of the facsimile transmission. Analog transmission impairments are identified along with signal to noise performance. Echo and delay measurements are also taken and the protocols are tracked. The measurement data is collected and analyzed to ascertain whether or not the facsimile transmission was normal. A diagnostic module uses the measurements to determine why any given transmission was abnormal.

Non-intrusive network-based analysis of facsimile transmissions

Non-intrusive monitoring and analysis of real-time facsimile transmissions is accomplished. Analog impairment measurements are made on the high speed page signal in those transmissions and protocol analysis is made on the low speed control messages in those transmissions. These measurements and analysis are a powerful tool for trouble shooting service problems afflicting facsimile transmissions. Actual customer traffic can be monitored to detect circuit impairments and to evaluate service being provided. Customer complaints can be handled by providing them with a special phone number which may be called to provide the ability to have the facsimile transmission experiencing a problem specially directed through the facsimile analyzer and forwarded to the intended destination while it is being non-intrusively monitored by service personnel who then can quickly provide the customer with a diagnosis of the problem.

Subscriber initiated non-intrusive network-based analysis of facsimile

An unknown voiceband digital data modem signal is classified as being generated by one of a plurality of possible digital data modem signal sources, e.g., CCITT V.29, CCITT V.32, CCITT V.33 or the like digital data modems. Classification is achieved by employing a blind, i.e., self-recovering, adaptive equalizer to remove effects of linear channel impairments and to generate a sequence of magnitude estimates at the symbol rate of the unknown voiceband digital data modem signal. The sequence of magnitude estimates is compared to predetermined representations of known possible voiceband digital data modem signals and the results of the comparison are used to identify the digital data modem signal source of the signal. In one example, the predetermined representations are templates of conditional density functions of magnitude estimates obtained from known voiceband digital data modem signals generated by corresponding digital data modem signal sources. The symbol rate detector detects bit rate and type of modulation.

Classifier for high speed voiceband digital data modem signals

During a training sequence, a speaker-trained speech recognizer detects and signals the speaker when vocabulary word pairs are potentially confusing to the recognizer. Each vocabulary word is converted into feature signals and then parameters representing a predetermined reference model of that word. The feature signals of a subsequent potential vocabulary word are compared against the reference model of each vocabulary word previously stored in the recognizer memory. The speaker is signaled when the potential vocabulary word is confusingly similar to one of the existing vocabulary words.

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Fair Haven, NJ, United States of America

Thomas W Goeddel