Merlin Technology, Inc.

Palm, Incorporated

Palmone, Incorporated

Hewlett-packard Development Company, L.p.

Gary Garrabrant

Rudolf Zeller

Timothy Bayliss

Scott Phillips

Katherine Elliott

John E Mercer

John Michael Brown

Edward Vertatschtisch

Edward Joseph Vertatschitsch

A transmitter for inground use controls a depth signal transmit power in relation to a data signal transmit power such that one reception range of the depth signal at least approximately matches another, different reception range of the data signal. A portable device can form a system with the transmitter in which the portable device scans a plurality of frequencies within at least one low frequency depth signal range to measure the electromagnetic noise at each one of the plurality of frequencies and identify at least one of the frequencies as a potential depth frequency for the transmitter. The portable device can include a dual mode filter having a rebar mode and a normal mode filter. The depth signal frequency is dynamically positionable in relation to low frequency noise.

Advanced passive interference management in directional drilling system, apparatus and methods

A system includes a transmitter for use in conjunction with a horizontal directional drilling system that transmits a multi-bit symbol stream that characterizes sensor symbols for receipt by an aboveground portable device. The portable device receives the symbol stream for aboveground recovery of the sensor signals. The transmitter can precisely place the symbol frequencies at least to avoid a noise environment, as well as to avoid powerline harmonics, and can utilize wave shaping for transmitted symbols at least to provide for transmission power control, spectral content control and wideband antenna matching. The receiver can measure the noise environment to identify the symbol frequencies used by the transmitter. The noise can be scanned at an incremental resolution across a wide frequency bandwidth for display or automatic symbol frequency selection.

Communication protocol in directional drilling system, apparatus and method utilizing multi-bit data symbol transmission

A property of a wireless signal over time is monitored while a processor is maintained in a first power state that utilizes less power than a second power state. While the processor remains in the first power state, a measure of the property is compared to a first threshold and to a second threshold. The processor can be transitioned from the first power state to the second power state if the measure crosses the first threshold and the second threshold, and otherwise the processor is maintained in the first power state.

Managing power consumption in a wireless device

A method and system of periodically measuring the signal strength fluctuations in a wireless connection between a portable computer system and a wireless network. The portable computer system has a main processor and a DSP (digital signal processor). The DSP receives instructions from the main processor for controlling the periodic measuring, and subsequent thereto is placed in low power mode. The main processor is placed into a low power mode after sending the instructions. The DSP periodically awakens to measure the signal strength fluctuations while the main processor remains in a low power mode. When the signal strength fluctuation is unacceptable, this triggers the DSP to awaken the main processor. When the signal strength fluctuation is acceptable, the DSP returns to a low power state until the next periodic measuring.

Digital signal processor update of single channel strength signal

A method is described for decoding a signal in a noise environment using maximum likelihood soft decision decoding for input streams containing known data. ISI problems are ameliorated, and decoding is implemented by palmtop computers and devices of limited computational capability. Decoded signals make use of the (12, 8) Hamming Code for a MOBITEX application. A table with predetermined ISI values is downloaded from a host processor to an on-board DSP at runtime. Known information in the frame header is utilized to help determine unknown data. Decoding proceeds in one embodiment by finding codewords that minimize a sum corresponding to data values extracted from header information. Other tables generated for use contain soft decision information and FEC words. Minimizing data translation by using known data and other embodiments advantageously minimize computational resources required to decode data by maximum likelihood soft decision decoding.

Maximum likelihood decoding for input streams containing known data

A method and system for encoding and decoding a sequence of K binary digits using reduced-size lookup tables. The sequence of K binary digits is separated into multiple segments (e.g., a first segment and a second segment). The first segment is used as an index into a first lookup table that contains an encoded version of all combinations of binary digits possible in the first segment. In a similar manner, the second segment is used as an index into a second lookup table that contains an encoded version of all combinations of binary digits possible in the second segment. Using the first lookup table, an encoded sequence is obtained for the first segment, and an encoded sequence is obtained for the second segment using the second lookup table. An encoded sequence for the entire sequence of K binary digits is obtained by combining the encoded sequences for the first and second segments. Two lookup tables are thus used to encode the sequence of K binary digits instead of a single lookup table having 2 entries. The sizes of the two lookup tables are such that, if combined, they would contain fewer than 2 entries, thereby saving memory space in devices with limited memory capacity.

Reduced table size forward error correcting encoder

A method for minimizing errors in a modulated signal transmitted over a transmission medium. The method is applied to the entire data block, thereby incorporating information about the parities of each row of data to fix and correct the errors in the row. Thereafter ISI removal is applied on a row by row basis, with such corrections being applied via soft decision coding. In particular, the data samples are first collected in a data block (or FEC block). A soft decision buffer is thereafter created by taking each sample involved. An FEC word is created by processing down each row of the soft decision buffer and creating a binary stream out of the sign bits for each table entry. This creates an estimate of the word by thresholding it around the zero level. A syndrome is generated via a comparison of the parity bits for each FEC word. The syndrome provides the most likely bit error positions, represented by an offset into the FEC word. The error positions map back into the array of soft decision buffer entries and the absolute value entries are summed for each corresponding position. This produces sets of numbers and the set with the smallest value is used to indicate the error pattern. The bits believed to be in error are flipped in the FEC word. ISI removal is applied to the soft decision buffer on a row-by-row basis (excluding the first row) to create an intermediate data frame, referred to as the Rx Frame. Upon completion, the process is repeated in the other direction for all of the rows except the last row, on a row-by-row basis. Upon completion, the data block errors will be minimized and the received block should match the transmitted block. The process therefore provides minimal data block errors, but at the same time uses less processing resources.

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Seattle, WA, United States of America

Gary Garrabrant