Pctel, Inc.

Other

Vital Wireless, LLC

Ic Tel Inc.

Vitaly Drucker

Yuri Goldstein

Yuri Okunev

Qin Wang

Oin Wang

William Hanna

Yuri Okuney

An improved Interrogator (and method of operation) for use in a radio frequency identification system wherein at least one tag modulates a radio frequency signal by modulated backscatter operations.

RFID interrogator with improved symbol decoding and methods based thereon

An improved RFID Tag, Interrogator, and system wherein at least one tag modulates a radio frequency signal by modulated backscatter operations.

RFID tag, interrogator and system with improved symbol encoding and decoding

An improved Interrogator for use in a radio frequency identification system wherein at least one tag modulates a radio frequency signal by modulated backscatter operations.

RFID interrogator with improved symbol decoding and systems based thereon

Distinguishing between final coding of received signals in a PCM modem

A DSL modem with a receiver and a transmitter includes an LDPC encoder which utilizes a generation matrix G which is derived from a substantially deterministic H matrix in order to generate redundant parity bits for a block of bits. The H matrix is determined by assigning &ldquo;ones&rdquo; of a first column N randomly or deterministically. Then, beginning with the second column, assignment of &ldquo;ones&rdquo; is carried out deterministically with each &ldquo;1&rdquo; in a previous ancestor column generating a &ldquo;1&rdquo; in the next descendant column based on the rule that a descendant is placed one position below or above an ancestor. As a result, descending or ascending diagonals are generated. When distributing &ldquo;ones&rdquo; in any given column, care is taken to ensure that no rectangles are generated in conjunction with other &ldquo;ones&rdquo; in the current column and previous columns. By avoiding generation of rectangles, diagonals are interrupted.

DSL modem utilizing low density parity check codes

The receiver of a PCM modem utilizes the V.90 TRN training signal for detecting whether any of the six slots of the received signal may be subject to alternating robbed bit signaling (ARBS), and what the alternating robbed bit signaling pattern may be. This is accomplished by accumulating the received level over a plurality of frames for each slot and by comparing the received levels for each slot to an average level for that slot. If the difference between the received levels and the average levels exceeds a threshold, the slot is determined to be subject to ARBS. Where a slot is subject to ARBS, DIL sequence signals for frames of the alternating robbed bit signaling slot having LSB&equals;0 and LSB&equals;1 are accumulated separately (if available) in order to generate two translation tables (TRT , TRT ) for that slot. Where the DIL sequence is found only in the frames having the alternating robbed bit signaling slot having LSB&equals;0 or having LSB&equals;1, only one translation table can be generated. Different algorithms are provided for designing a constellation for the alternating robbed bit signaling slot depending on (a) whether two translation tables were generated for the slot, (b) whether the frame-to-TRT correspondence is known, and (c) where only one translation table is generated, whether the translation table generated was TRT or TRT

Translation table and constellation design for a PCM modem subjected to alternating robbed bit signaling

Methods are provided for determining whether any slots of a modem frame are subject to robbed bit signaling (RBS), and whether the robbed bit signaling is &bgr;-codec robbed bit signaling. From an obtained DIL sequence, an ordered table of level values for each slot is generated. In determining whether any slots are RBS slots, distances between adjacent levels of the table for each slot are obtained and are compared to a &ldquo;zero distance&rdquo; threshold value in order to determine the number of distances which exceed the &ldquo;zero distance&rdquo; value. For each slot, the number of zero distances are compared to a threshold value, and if the number of zero distances exceeds the threshold value, the slot is declared to be a RBS slot. Zero distance thresholds for each slot are generated by finding a function of a maximum distance for that slot among the adjacent levels. In determining whether any RBS slots are &bgr;-codec slots, distances are found between corresponding levels of the ordered tables. If substantially more than half of the distances from one slot to the others are found to be greater than a zero distance threshold value, the slot is determined to be a &bgr;-codec slot.

Robbed bit signaling identification in a PCM modem

A method of providing a high bit rate DMT signal includes providing information on a plurality of DMT tones, with at least two of the plurality of DMT tones sending information in parallel. Of the tones sending information in parallel, at least one has a SNR too low to be individually used for the number of bits it is transmitting. Accordingly, the tones are coherently &ldquo;combined&rdquo; at the receiver in order to generate a SNR sufficient together to carry, at the desired BER, the number of bits being transmitted in parallel. Two or more tones which alone cannot carry a single bit of information may be used together to provide a sufficient SNR at the receiver to transmit one or more bits. Similarly, two or more tones which alone cannot carry two bits of information, may be used together via parallel transmission to provide a sufficient SNR at the receiver. Further, the bit-carrying capacity of a first tone which can carry one or more bits may be increased by transmitting an increased number of bits in parallel with one or more additional tones which cannot carry any bits of information. According to another embodiment of the invention, rather than sending two or more DMT tones in parallel, one or more DMT tones are repeated over a plurality of DMT symbols, and &ldquo;combined&rdquo; coherently in order to generate a SNR sufficient together to carry the number of bits being carried by the repeated tone.

Method and apparatus for data transmission using discrete multitone technology

Methods are provided for generating at least one translation table for a modem having a frame having a plurality of slots. DIL sequence information from another modem is used to generate ordered table of levels, and distances between adjacent levels of the ordered table for found for each slot. The distances are used to distinguish between slots subject to robbed bit signaling (RBS) and slots not subject to RBS, and the ordered tables are used to make a determination as to whether the DIL sequence information is A-law or &mgr;-law information. Scaling factors are generated from the A-law/&mgr;-law determination as well as from a PAD estimation, and the scaling factors are utilized in generating translation tables. A PAD estimation function is utilized in finding the PAD estimation.

Translation table design for a PCM modem

A method in a modem having a frame having a plurality of slots, for determining whether incoming DIL sequence information contains A-law or &mgr;-law information is provided. From the DIL sequence information, an ordered table of levels for each slot is generated. The levels of all non-robbed-bit slots are averaged, and average levels are subjected to an A-law/&mgr;-law separation function. The separation function

Distinguishing received A-law and &mgr;-law signals in a PCM modem

Modem constellations are designed by independently optimizing for each slot of a frame, the distances between constellation points used for that slot. A maximum number of points N(,) are chosen having at least the minimum distance d,without exceeding a power limitation Plim. Using N(,), an attempt is made to increase the d,in the constellation without exceeding Plim. Constellations may be further optimized by, where possible, decreasing N(,) in a particular constellation without affecting the total data rate of the frame. Thus, a maximum potentially achievable data rate Rmax is calculated given the number of points which are in each of the six constellations, and comparing Rmax to a standards-permitted data rate DR; and then, if Rmax exceeds DR, by decreasing N(,) in one or more constellations, provided the decrease in the number of points does not cause a recalculated Rmax to drop below DR. Further optimization is obtained by attempting to increase d,in one or more slots by permitting that slot(s) to exceed Plim, provided the average power of the frame is not exceeded. This is accomplished by finding the slot with the maximum error probability, increasing d,for that slot (while maintaining N(,)) to thereby exceed frame power limitations for that slot, and checking to see whether the changes to the constellation in that slot violates the average frame power limitations. A simple system for checking average constellation power is also provided.

Growing community of inventors

Stamford, CT, United States of America

Vitaly Drucker