Patent Description:
Distributed sensor networks use a set of spatially scattered sensors designed to obtain measurements from the environment. A central node connected to the sensors collects the data, which is used to extract relevant information about the environment.

Conventional network types, such as the RS-<NUM> network, allow the implementation of linear bus topologies (e.g., in-line serial drop communication links). However, such networks have bandwidth/data rate limitations that constrain the quantity of and the physical spacing between sensors employed. Data rates (baud rates) are typically governed by cable length and physical signaling protocols. Electrical cables have an inherent low-pass filtration characteristic (due to intrinsic inductance, resistance, and capacitance), which leads to lower data rates for longer spans of the electrical cable. Data protocols attempt to optimize signal integrity and may limit the bit error rate for a given design parameter. Extending length and number of distributed sensors may require additional busses or cables running at slower baud rates. Manufacturability may become increasingly more expensive as additional cables are added to accommodate sensor bandwidth, which can lead to solutions that may not be realistic in terms of cost. Some semiconductor manufacturers have developed RS-<NUM> transceiver devices with built-in cable equalization (e.g., high-frequency gain circuits) that extends the range of an RS-<NUM> network. While these devices may succeed in lengthening the range of such networks, they still have a limit to their maximum range. Further, these devices do not attempt to address the concept of synchronization.

Other network types such as Ethernet and USB have existing methods for extending their range; however, these methods often impose high power consumption, cost, and even size making them unsuitable for many applications, such as long-distance sub-sea surveillance.

What is desired is an extendable synchronous low power telemetry system for distributed sensor networks that is low cost, reliable, and readily scalable.

<CIT> discusses a method of start/stop synchronous data transmission that allows stable start/stop synchronous communication with a clock signal generated by an oscillator which has a relatively low level of oscillation frequency accuracy. The start/stop synchronous data transmission is carried out between a master station having a high-accuracy oscillating circuit adapted to a baud rate matching transmission line characteristics and at least one slave station having a Low accuracy oscillating circuit. The master station sends a predetermined dummy message at a predetermined period. The slave station counts clock pulses from the Low accuracy oscillating circuit for a time interval between edges of a first bit frame of the dummy message. A baud rate clock signal is generated from the count of clock pulses according to a predetermined algorithm for start/stop synchronous communication.

<CIT> discusses a plurality of data acquisition and transceiver units that are connected in series to a central signal processor through a common telemeter link. The telemeter link includes a data channel, an interrogation channel and a control channel. The signal propagation velocity through the control channel may, for example, be greater than the signal propagation velocity through the interrogation channel. The central signal processor sends an interrogation signal through the interrogation channel to the data acquisition units. After a selected delay, a control pulse is transmitted. The delay between transmissions of the two signals is proportional to the differential travel time of the signals in the two channels. Accordingly the signal through the control channel will overtake and intercept the signal propagating through the interrogation channel, at a selected data acquisition unit. When any selected data acquisition unit receives a control signal through the control channel at the same time that it receives an interrogation signal through the interrogation channel, that unit is activated and a desired function is performed. The control signal is a square wave pulse having a width which is adjustable by integral multiples of the differential travel time. By adjusting the width and transmission-time delay of the control pulse, any selected subset of one or more consecutive units may be activated. Each data acquisition unit may have two or more input channels, which are connected in turn through common electronics to the data transmission channel by means of a channel selector or multiplexer. The interrogation signal may exist in one of two or more states. In the first state, in combination with a control pulse, the interrogation signal resets the multiplexer. In the second state, the interrogation signal advances the multiplexer to the next input channel in sequence.

Additionally, document <CIT> discloses an application that relates to integrated circuit chips (DRAM), and, more particularly, to daisy chained chips including a strobe signal and clock signal with a fixed phase relationship.

Aspects of embodiments of the invention are directed toward a method for connecting a large number of distributed synchronized sensors and a telemetry system implementing the same. Aspects of embodiments of the invention permit the product of data transmission length multiplied by bandwidth to be extended to significantly higher values than previously attainable while maintaining precise timing synchronization between sensors. Thus, embodiments of the present invention allow both the physical spacing and quantity of sensors to be extended beyond the typical limits of standard distributed sensor networks (DSNs) and to be arbitrarily scalable.

Aspects of embodiments of the invention are directed toward a low power, low cost telemetry system architecture that couples multiple distributed sensors to a common node using off-the-shelf transceiver devices. The system comprises a gateway node, a multi-wire cable, one or more repeaters, and a common digital interface on each sensor. Sensors are placed along the cable and receive the synchronization signal which allows them to sample their measurements simultaneously. The sensors then transmit their data samples to the gateway. node using time division multiplexing (TDM). The Repeaters capture and retransmit the uplink data samples to the gateway node.

According to an embodiment of the invention, there is provided a bidirectional repeater according to claim <NUM>.

According to an embodiment of the invention, there is provided a synchronous telemetry system according to claim <NUM>.

According to an embodiment of the invention, there is provided a method according to claim <NUM>.

These and other features and advantages of the invention will be better understood by reference to the following detailed description when considered in conjunction with the following drawings, in which like elements are referenced with like numerals. These drawings should not be construed as limiting the invention, but are intended to be illustrative only.

The detailed description set forth below in connection with the appended drawings is intended as a description of illustrative embodiments of a system and method for repeating signals in a distributed sensor network (DSN) and a synchronous telemetry system using the same in accordance with the invention, and is not intended to represent the only forms in which the invention may be implemented or utilized. The description sets forth the features of the invention in connection with the illustrated embodiments. It is to be understood, however, that the same or equivalent functions and structures may be accomplished by different embodiments that are also intended to be encompassed within the spirit and scope of the invention. As denoted elsewhere herein, like element numbers are intended to indicate like elements or features. The terms "substantially," "about," and similar terms are used as terms of approximation and not as terms of degree, and are intended to account for the inherent deviations in measured or calculated values that would be recognized by those of ordinary skill in the art. Furthermore, when a component is referred to as being "coupled" to or "connected" to another component, it can be directly attached to the other component or intervening components may be present therebetween.

Some embodiments of the invention are directed toward a low power, low cost synchronous telemetry system architecture that couples multiple distributed sensors to a gateway node (e.g., central node) using off-the-shelf transceiver devices (e.g., RS-<NUM> transceiver devices such as the <NUM>-pin RS-<NUM> transceiver integrated chip). In an embodiment, the system comprises a gateway node, a cable (e.g., a multi-wire cable such as a <NUM>-wire cable), one or more repeaters, and one or more sensors having a common digital interface. Sensors may be placed along the cable and receive a synchronization signal, which allows them to sample their measurements simultaneously. The node, one or more repeaters, and the one or more sensors are coupled together (e.g., electrically connected in series) through the cable. In an embodiment, the downlink synchronization signal is passed down the cable through one or more repeaters to the one or more sensors. The one or more sensors then may transmit their data samples to the gateway node using time division multiplexing (TDM). The one or more repeaters capture and retransmit the uplink data samples to the gateway node.

Embodiments of the present invention permit the cable length-bandwidth product to be extended to significantly higher values than previously attainable while maintaining precise timing synchronization between sensors. For example, when the cable length reaches the physical limit for a given segment of an in-line serial drop communication link, integration of a repeater allows another segment to be added. Repeaters may be added to extend the distance to any arbitrary length.

<FIG> is a block diagram of a synchronous telemetry system <NUM> utilizing a repeater <NUM>, according to an illustrative embodiment of the present invention.

According to an embodiment of the present invention, the synchronous telemetry system <NUM> includes a gateway node (e.g., a central node or a sink node) <NUM> and a plurality of field nodes coupled together (e.g., electrically connected to one another) via a cable <NUM>. The field sensors include a plurality of sensors <NUM> and one or more repeaters (e.g., bidirectional repeaters) <NUM>, which may be distributed along the length of the cable <NUM> at regular or irregular intervals. The sensors <NUM> measure one or more parameters of interest in the environment and may be any combination of acoustic sensors, optical sensors, temperature sensors, vibration sensors, and/or the like. The sensor measurements are synchronized by way of a synchronization signal (e.g., downlink synchronization signal) provided by the gateway node <NUM> and carried by a telemetry bus of the cable <NUM> to each of the sensors <NUM>. Upon making a measurement, sensors <NUM> write their data samples to a data signal (e.g., an uplink data signal or multiplexed data signal) using time division multiplexing (TDM), which is transmitted back to the gateway node <NUM>. The synchronization signal and the data signal may be carried by the same telemetry bus of the cable <NUM>. The telemetry bus may be a single electrical conductor (e.g., single wire), or may be a differential balanced line having two electrical conductors (as in a twisted pair cable), which may offer improved signal to noise ratio as compared to a single conductor line.

In an embodiment, the one or more repeaters <NUM> receive both the synchronization signal and the data signal (e.g., the multiplexed data signal), and regenerate one or more of the signals to correct for distortions (e.g., attenuation as a result of traversing the cable <NUM>) and improve their signal to noise ratio (SNR), and retransmit the signals down or up the telemetry bus of the cable <NUM>. As such, for a given bit rate, a series of sensors (comprising a segment) may be extended as far as allowed by the signaling protocol, and a repeater <NUM> may be used to serially couple the series of sensors to a further segment. In this manner, an arbitrary number of segments may be serially coupled together to form a chain <NUM> of an arbitrary length.

In an embodiment, the gateway node <NUM> provides electrical power to the field nodes through a power bus line of the cable <NUM>. The power bus line may include two electrical conductors for carrying a power signal and a reference (e.g., ground) signal. In an embodiment, some or all of the field nodes may each have a local power source (such as a battery) to power the corresponding node. The local power sources may be operated in tandem with, or in lieu of, a central power source at the gateway node <NUM>. Thus, in some embodiments, the local power source line may obviate the need for a power bus line at the cable <NUM>.

<FIG> is a block diagram of a synchronous telemetry system <NUM>-<NUM> utilizing a repeater <NUM>, according to an illustrative embodiment of the present invention.

The synchronous telemetry system <NUM>-<NUM> utilizes a multi-chain, parallel, in-line distributed sensor architecture (also referred to as a star topology). Each chain <NUM> may be substantially similar to that of the synchronous telemetry system <NUM> of <FIG>.

According to an embodiment, one or more gateway nodes <NUM> and/or <NUM>-<NUM> may be coupled together to form a telemetry system having a mesh topology.

While many of the examples and embodiments described herein may refer to the telemetry system <NUM> and/or the gateway node <NUM>, the concepts described are not topology specific and may be equally applicable to, for example, the telemetry system <NUM>-<NUM> and/or the gateway node <NUM>-<NUM>.

<FIG> is a schematic diagram of a repeater <NUM>, according to an illustrative embodiment of the present invention. <FIG> is a timing diagram showing the effect of the operation of the repeater <NUM> on the signal carried by the cable <NUM>, according to an embodiment of the present invention.

According to an embodiment, the bidirectional repeater <NUM> includes first and second transceivers (e.g., bidirectional transceivers) 200a and 200b for receiving and transmitting the downlink and uplink signals (e.g., the downlink synchronization signal and the uplink data signal), and a repeater circuit <NUM> for repeating the downlink and uplink signals received by the transceivers 200a/b. In an embodiment, the repeater circuit <NUM> includes a synchronization controller <NUM> for locking into the periodicity of the synchronization signal, a pass-through gate <NUM>, and a data regenerator <NUM>.

In an embodiment, each of the transceivers 200a/b may function as a switch (e.g., a three-way switch) configured to couple (e.g., electrically couple or electrically connect) the cable telemetry bus 120a to either of the downlink line <NUM> or the uplink line <NUM>. The first transceiver 200a may be coupled to the cable telemetry bus 120a via the first port (e.g., the first input-output port) 201a, and the second transceiver 200b may be coupled to the cable telemetry bus 120a via the second port (e.g., the second input-output port) 201b. In an example, the transceivers 200a/b couple the cable telemetry bus 120a to the downlink line <NUM> when a control signal (e.g., a timing signal SYNC_GATE) is at a logical high, and couple the cable telemetry bus 120a to the uplink line <NUM> when the control signal (e.g., the timing signal SYNC_GATE) is at a logical low.

The synchronization controller <NUM> is configured to generate the timing signal SYNG_GATE that matches the periodicity and phase of the synchronization signal SYNC_IN. In so doing, the repeater <NUM> may utilize a phase lock loop (PLL) having a phase detector and a voltage control oscillator (VCO). At initial power on, the timing signal SYNC_GATE may be at a logic high, thus coupling the cable telemetry bus 120a to the downlink line <NUM> and allowing synchronization signal SYNC_IN to reach the synchronization controller <NUM>. After one or more cycles of the synchronization signal SYNC_IN, the synchronization controller <NUM> may lock onto (i.e., "learn" the periodicity and phase of) the synchronization signal SYNC_IN and generate the timing signal SYNC_GATE (shown in <FIG>), which may be slightly wider than the synchronization signal SYNC_IN. The wider width may be desired to accommodate for any nominal delays at the synchronization pass-through gate <NUM>. In an example, this additional width may be a few nanoseconds (ns) to a few microseconds (µs) long. In an embodiment, the width of the timing signal SYNC_GATE extends beyond the synchronization signal SYNC_IN to cover a superframe bit and a command bit (discussed in greater detail below with reference to <FIG>).

In an embodiment, the repeater <NUM> passes the synchronization signal SYNC_IN through without any regeneration (e.g., without any distortion), in order to reduce (e.g., minimize) delays in the downlink transmission of synchronization signal and to improve synchronicity of the telemetry system <NUM>. In an embodiment, the repeater <NUM> also passes the superframe bit and the command bit through without any regeneration. As such, the pass-through gate <NUM> performs a logical AND operation on the signal on the downlink line <NUM> (which may include a synchronization pulse and sensor data) and the timing signal SYNC_GATE, ensuring that only the synchronization pulse is passed-through and outputted from the repeater <NUM> at the second port 201b.

The data regenerator <NUM> resynchronizes, i.e., re-clocks and regenerates, the data signal (which is in the form of one or more multiplexed data blocks) from the sensors <NUM> that follow the repeater <NUM> down the chain <NUM>. When the timing signal SYNC_GATE is low, the transceivers 200a/b couple the cable telemetry bus 120a to the uplink line <NUM> allowing the data regenerator <NUM> to receive sensor data blocks DATA_IN from sensors <NUM>. The data regenerator <NUM> may include two or more shift registers and a data controller <NUM> for controlling the operation of the shift registers. In an embodiment, the data regenerator <NUM> includes a first shift register (e.g., a serial-to-parallel or serial-in/parallel-out shift register) <NUM>, a second shift register (e.g., a parallel-to-parallel shift register) <NUM>, and a third shift register (e.g., a parallel-to-serial or parallel-in/serial-out shift register) <NUM>. The data controller <NUM> may provide a clock signal matching the bitrate of the sensor data blocks DATA_IN. The clock signal may have a frequency that is the multiple of the frequency detected for the synchronization signal SYNC_IN (or timing signal SYNC_GATE). The first shift register <NUM> clocks in the data bits from the sensor data blocks DATA_IN one bit at a time, the second shift register <NUM> copies all of the bits of the sensor data blocks DATA_IN at the same time, and the third shift register <NUM> sends out the bits one bit at a time, which together form the repeated data block DATA_OUT. The data controller <NUM> controls the timing of the operation of the shift registers such that the repeated data block DATA_OUT is aligned with the synchronization signal SYNC_IN (or the timing signal SYNC_GATE). (Alignment will be discussed in greater detail in the description of <FIG>). In shifting the data bits, the shift registers (e.g., shift registers <NUM>, <NUM>, and <NUM>) also recreate the bits, thus correcting any distortions that the data bits may have experienced as a result of noise or cable transmission characteristics. As such, the repeated data block DATA_OUT may be a delayed and regenerated version of the sensor data block DATA_IN as shown in <FIG>.

The repeater <NUM> may further include a power unit <NUM> for providing power to the circuit blocks within the repeater <NUM>. In some embodiments, the power unit <NUM> may draw power from a cable power bus 120b of the cable <NUM> (as shown in <FIG>) and/or draw upon a local power source (such as a battery).

<FIG> illustrates the waveform diagram of a frame <NUM> of a downlink synchronization signal <NUM> transmitted by the gateway node <NUM>, according to an illustrative embodiment of the present invention. <FIG> illustrates a waveform diagram of a frame <NUM> of the uplink data signal <NUM> received by the gateway node <NUM>, according to an illustrative embodiment of the present invention. <FIG> illustrates a waveform of a data sample of the uplink data signal <NUM> received by the gateway node <NUM>, according to an illustrative embodiment of the present invention.

According to an embodiment, the waveform of the signal (e.g., a downstream synchronization signal <NUM> or uplink data signal <NUM>) carried by the telemetry system <NUM> may be divided into a number of frames (e.g., time frames) <NUM>, which may be subdivided into a plurality of slots (e.g., time slots). In the examples illustrated in <FIG>, a frame <NUM> includes <NUM> equal slots (Slots <NUM>-<NUM>), a first of which contains a synchronization pulse (e.g., SYNC Pulse at Slot <NUM>). A second slot (Slot <NUM>) may be partially occupied by a command bit and a superframe marker. The command bit may be used to transmit a downlink command (e.g., a command from the gateway node <NUM> to the sensors <NUM>), while the superframe marker may become active (e.g., go high) every preset number of frames (e.g., every <NUM> frames) to mark the beginning of a superframe (of, e.g., <NUM> frames). The following slot (Slot <NUM>) may, in some examples, be reserved; however, it may also be used as a data slot. In an example, a frame <NUM> may represent <NUM> of time, and a superframe of <NUM> frames may have a duration of about <NUM>.

A frame <NUM> may include a preset number of data slots (e.g., <NUM> data slots), each of which may contain the data imprint of either the sensor <NUM> or the repeater <NUM>. Each data slot may occupy a portion of the slot (e.g., % of a slot) to leave sufficient spacing (e.g., ¼ of a slot) between data from adjacent slots. A first data slot (e.g., Slot <NUM>) may carry a repeater serial number, which uniquely identifies the repeater <NUM> among other repeaters that may be present in the synchronous telemetry system. The serial number may allow each repeater to be uniquely programmed by the gateway node <NUM> at the time of system initialization. The information programmed into the repeater <NUM> may include a slot number. The repeater <NUM> may retransmit all slots up to the programmed number, then turn off its output so that upstream field sensors (e.g., sensors lying between the gateway node <NUM> and the repeater <NUM>) may take control of the cable telemetry bus 120a. The repeater serial number may be retransmitted by the repeater <NUM>. In an embodiment in which more than one repeater are integrated onto the cable <NUM>, each repeater may shift the serial number of the preceding repeater by two slots, to leave two slots available to insert its own serial number. A frame <NUM> may also include a preset number of unused slots (e.g., <NUM> unused slots) to accommodate for delays in the uplink data signal (or return signal) from the sensors <NUM>. Delays in the return signal will be further explained with reference to <FIG>.

As shown in <FIG>, when a gateway node <NUM> transmits a synchronization signal <NUM>, a frame <NUM> of the signal may only include a synchronization pulse (e.g., Sync Pulse at Slot <NUM>) and a command bit and superframe marker. As the signal is returned, the data slots may be occupied by measurement data (e.g., sensor data or data blocks <NUM>) from the sensors <NUM>, as is shown in the ideal waveform <FIG>.

As shown in <FIG>, a sensor data (or data block) <NUM> includes a start bit, a number of data bits (e.g., binary data bits D0-D15), and one or more code bits (e.g. even parity bits) for error detection. In an example, each of the start bit, data bits, and parity bits have a duration of <NUM>/<NUM> of the sensor data occupies <NUM>/<NUM> of a data slot. In an embodiment, the signal is in a high impedance state during the unoccupied portion of the data slots (e.g., ¼ of a data slot). In the data signal (e.g., the multiplexed data signal) <NUM>, the arrival of each successive data block is marked by a lull (e.g., a high impedance state) followed by the start bit.

<FIG> is a waveform diagram 400a illustrating waveforms of signals received and transmitted by the gateway node <NUM>, sensors <NUM>, and the repeater <NUM> in a multi-sensor synchronous telemetry system <NUM>, according to an embodiment of the present invention.

For simplicity of illustration, it is assumed here that the synchronous telemetry system <NUM> includes only a single repeater <NUM> and N sensors (N being an even integer greater than <NUM>) half of which appear before the repeater <NUM>; however, embodiments of the present invention are not limited thereto and the operations described herein are equally applicable to a telemetry system including any (non-zero) number of repeaters <NUM> and sensors <NUM>.

Here, the sensor <NUM> furthest away from the gateway node <NUM> is labeled as Sensor <NUM> as it is the first sensor <NUM> in the chain of N sensors <NUM> to transmit data back to the gateway node <NUM> despite the fact that it is the last sensor in the chain to receive the synchronization signal. In the same manner, the closest sensor <NUM> to the gateway node <NUM> is labeled as Sensor N as it is the last in a chain of N sensors <NUM> to transmit data back to the gateway node <NUM>. For simplicity of illustration, it is assumed that the repeater <NUM> and Sensor <NUM> are located at distances L<NUM> and L<NUM>, respectively from the gateway node <NUM> (where L<NUM> is greater than L<NUM>).

The gateway node <NUM> generates and transmits a synchronization signal to the field nodes (e.g., sensors <NUM> and repeater <NUM>) through the cable <NUM>. The synchronization signal arrives at the repeater <NUM> with a delay of Δt, corresponding to the length L<NUM>. In the embodiments according to the claimed invention, the repeater <NUM> passes the synchronization signal (e.g., SYNC pulse) through without re-clocking for transmission to the sensors <NUM> down the line. In an embodiment, the repeater <NUM> also passes the superframe bit and the command bit through without any re-clocking. The signal is further delayed as it arrives at Sensor <NUM> and then Sensor <NUM>. Sensor <NUM> receives the repeated synchronization signal with a further delay of Δt<NUM> corresponding to the length L<NUM>-L<NUM>. In an example in which L<NUM> and L<NUM> are about <NUM> and about <NUM>, respectively, Δt<NUM> and Δt<NUM> may equal about <NUM>.

In an embodiment, each of the Sensors <NUM>-N performs its measurements when it detects the SYNC pulse of the synchronization signal. However, the Sensors <NUM>-N are configured to (e.g., preprogrammed to) transmit their data signals encapsulating the collected data (which appears in the form of data blocks) during preset data slots in a staggered manner (also referred to as time-division multiplexing). For example, Sensor <NUM> may transmit during what it perceives as Slot <NUM>, Sensor <NUM> may transmit during its perceived Slot <NUM>, and so forth. However, due to signal transmission delays, when each of the transmitted data blocks reaches the repeater <NUM>, it may be misaligned (e.g., not line up with) the data slots as perceived by the repeater <NUM>. For example, as illustrated in <FIG>, the data signal (e.g., data block) <NUM> from Sensor <NUM> may occupy about one half of Slot <NUM> at the repeater <NUM> and part of Slot <NUM>. In an embodiment, the repeater <NUM> re-clocks the data signals received by shifting the data signals in time to align with (e.g., begin at) the next data slot. For example, the repeater <NUM> may re-clock the data signal <NUM> from Sensor <NUM> to start at the beginning of Slot <NUM> as data signal <NUM>'. In so doing, the repeated data signals from Sensors <NUM>-N/<NUM> may be shifted by, for example, two data slots. The repeated data signals arrive at the gateway node <NUM> after a further transmission delay of Δt<NUM>. The gateway node <NUM> differentiates the data blocks using the start bit at the beginning of each data block and the lull period that follows the end of a data block.

In addition to re-clocking (e.g., performing timing alignment) of data signals, the repeater <NUM> also regenerates (e.g., reconditions) the constituent bits of the data block as appropriate to compensate for any transmission degradation and noise due to the cable <NUM> and/or environmental factors. In so doing, the repeater <NUM> extends the range that the data signals can traverse while maintaining an acceptable bit error rate. According to an embodiment, the repeater <NUM> may also perform a parity check using the one or more parity bits of the data signal received.

<FIG> illustrates a waveform diagram 400b of data blocks transmitted from sensors <NUM> to the gateway node <NUM> in a multi-sensor synchronous telemetry system <NUM>, according to an embodiment of the present invention.

In the example illustrated in <FIG>, the synchronous telemetry system <NUM> includes <NUM> sensors <NUM> distributed at regular intervals along a <NUM> long cable <NUM>, and a repeater <NUM> located at the middle of the cable at about <NUM>. The gateway node <NUM> transmits a synchronization signal having a number of frames, each marked by a SYNC pulse. The SYNC signal prompts Sensors <NUM>-<NUM> to nearly concurrently perform measurements of one or more environmental parameters. The repeater <NUM> passes the SYNC pulse through without re-clocking to preserve timing synchronization. Upon detecting the SYNC pulse, the Sensors <NUM>-<NUM> transmit data signals <NUM>-<NUM> corresponding to their measurements at predetermined times (e.g., at beginnings of successive data slots). For example, Sensors <NUM>-<NUM> may sequentially transmit data signals <NUM>-<NUM> during the first time block T<NUM>, and Sensors <NUM>-<NUM> may sequentially transmit data signals <NUM>-<NUM> during the second time block T<NUM>. Upon receiving each of the data signals <NUM>-<NUM> from Sensors <NUM>-<NUM>, the repeater <NUM> repeats (e.g., resynchronizes) the received stream Rx(Rep) by re-clocking and regenerating (e.g., reconditioning) each of the data signals <NUM>-<NUM> to generate data signals <NUM>'-<NUM>', which make up the transmit stream Tx(Rep). The transmit stream Tx(Rep) may be shifted in time from the received stream Rx(Rep) by a period of time greater than a data slot and less than two data slots. The transmission time of Sensor <NUM> may be set (or configured) such that data signal <NUM> occupies the data slot immediately following that of the last data signal of the transmit stream Tx(Rep), that is, data signal <NUM>'. Sensors <NUM>-<NUM> may sequentially transmit data signals <NUM>-<NUM>, as show in <FIG>. After a period of time corresponding to a transmission delay of <NUM>, the gateway node <NUM> receives the data signals <NUM>'-<NUM>' and <NUM>-<NUM>, which together form the received stream Rx(GN). The received stream Rx(GN) represents the uplink data signal as detected by the gateway node <NUM>.

The gateway node <NUM> may be coupled to the processing unit for analyzing the sensor data from the received stream Rx(GN). The processing unit may further control the operation of the gateway node <NUM>. A user may interact with the processing unit through a graphical user interface (GUI).

<FIG> illustrates a graphical user interface (GUI) <NUM> of the processing unit including control and monitoring panels, according to an embodiment of the present invention.

The GUI <NUM> may include a control panel <NUM> for controlling various aspects of the synchronous telemetry system <NUM>, such as toggling the system power, operating in diagnostic mode, etc. The GUI may further include a monitor panel <NUM> for monitoring various aspects of the data received from the each of the sensors <NUM>. In the example of <FIG>, the monitor panel depicts the power levels of signals received from a synchronous telemetry system <NUM> having <NUM> sensors <NUM>. An alarm panel <NUM> may provide a running tally of warnings or errors generated during the course of operation of the synchronous telemetry system <NUM>.

<FIG> is a block diagram of a process <NUM> of repeating signals received by the repeater <NUM>, according to an embodiment of the present invention.

In block <NUM>, the repeater <NUM> receives a synchronization signal at the first input-output port 201a of the repeater <NUM>. The first transceiver 200a passes the synchronization signal to the synchronization controller <NUM>, which locks into the periodicity and phase of the synchronization signal and generates a timing signal SYNC_GATE for controlling the timing operation of the internal components of the repeater <NUM>.

In block <NUM>, the repeater <NUM> passes the synchronization signal through without re-clocking to the second input-output port 201b of the repeater <NUM> for downlink transmission to one or more sensors <NUM>. The repeater <NUM> (e.g., the pass-through gate <NUM>) may pass through the synchronization signal without regenerating the signal.

In block <NUM>, the repeater <NUM> receives a multiplexed data signal at the second input-output port 201b of the repeater <NUM>. The second transceiver 200b passes the multiplexed data signal, which due to line delays may be out of sync with the synchronization signal, to the data regenerator <NUM> for resynchronization.

In block <NUM>, the data regenerator <NUM> resynchronizes the multiplexed data signal to generate a resynchronized multiplexed data. The data generator <NUM> may utilize a number of shift registers to resynchronize the multiplexed data signal by re-clocking (e.g., delaying by an appropriate amount to align with a next time slot) and regenerating the data bits of the multiplexed data signal.

In block <NUM>, the repeater <NUM> transmits the resynchronized multiplexed data signal through the first input-output port 201a to the gateway node <NUM>. In an example, the resynchronized multiplexed data signal may pass through one or more sensors <NUM> that may be coupled between repeater <NUM> and the gateway node <NUM>.

The embodiments described herein have employed active-high signals, however as will be understood by a person of ordinary skill in the art, the embodiments of the present invention may also operate using active-low signals without departing from the scope of the present invention. For example, with suitable changes to their circuitry, the gateway node <NUM>, sensors <NUM>, and repeater <NUM> can operate based on signals that are the inverse of the signals shown in <FIG>, <FIG>, and <FIG>.

Claim 1:
A bidirectional repeater (<NUM>) for repeating an electrical signal traversing a conductive line coupled between a gateway node (<NUM>) and a sensor (<NUM>) in a distributed sensor network, the bidirectional repeater comprising:
a first input-output port (201a) coupled to the gateway node (<NUM>);
a second input-output port (201b) coupled to the sensor (<NUM>);
a first transceiver (200a) configured to receive a synchronization signal from the first input-output port (201a) and to transmit a resynchronized data signal to the first input-output port (201a);
a second transceiver (200b) configured to transmit the synchronization signal to the second input-output port (201b) and to receive a data signal from the second input-output port (201b); and
a repeater circuit (202a) coupled to the first and second transceivers (200a, 200b) and configured to pass through the synchronization signal without re-clocking the synchronization signal, and to resynchronize the data signal to generate the resynchronized data signal.