Systems and methods for double data rate communication via power cable
Systems and methods for communicating messages over a three-phase power cable between surface equipment and downhole equipment in a well. A transmitter parses messages into data bit pairs and generates a parity bit for each pair (a triplet). The bits of each triplet are concurrently but separately transmitted over the power cable. Each triplet is received from the power cable by a receiver and is decoded to identify the data bits. The receiver may verify the received bits and/or recover a lost bit in each triplet. The data bits are then reconstructed into the original message. Since each triplet has two bits, the effective data rate is twice the data rate of transmitting a single bit at a time. The parity bit enables recovery of data with a bit error rate of up to 1 in 3.
1. A system for communicating comms on power messages between surface equipment and downhole equipment in a well, the system comprising:
surface equipment positioned at the surface of a well;
downhole equipment positioned downhole in the well;
a power cable coupled between the surface equipment and the downhole equipment,
wherein the power cable has three conductors configured to transmit three-phase power from the surface equipment to the downhole equipment;
at least one transmitter configured to
parse a comms on power message into one or more data bit pairs,
generate a parity bit for each of the one or more data bit pairs, thereby forming a triplet, and
for each of the triplets, concurrently transmit the bits of the triplet over the power cable, wherein each of the bits are transmitted on separate conductors of the power cable;
at least one receiver configured to
for each of the transmitted triplets, decode the triplet and thereby identify the data bits of the triplet, and
reconstruct the data bits of one or more triplets into the comms on power message.
2. The system of claim 1 , wherein decoding the triplet comprises verifying that the triplet conforms to one of a set of predetermined patterns.
3. The system of claim 1 , wherein decoding the triplet comprises recovering a lost bit and thereby conforming the triplet conforms to one of a set of predetermined patterns.
4. The system of claim 1 , wherein the surface equipment comprises a control system at the surface of the well.
5. The system of claim 1 , wherein the downhole equipment comprises a gauge package.
6. The system of claim 5 , wherein the downhole equipment further comprises an electric submersible pump (ESP); wherein the ESP is powered by three-phase power transmitted from the surface equipment over the power cable.
7. The system of claim 6 , wherein the surface equipment comprises a variable speed drive that generates three-phase power which is transmitted over the power cable to the ESP.
8. The system of claim 1 , wherein the at least one transmitter includes a first one of the transmitters incorporated into the surface equipment and a second one of the transmitters incorporated into the downhole equipment; and wherein the at least one receiver includes a first one of the receivers incorporated into the surface equipment and a second one of the receivers incorporated into the downhole equipment; wherein the system is capable of bidirectional communications.
9. The system of claim 1 , wherein the system is configured to synchronize the at least one transmitter and the at least one receiver prior to communicating the comms on power message.
10. The system of claim 9 , wherein synchronizing the at least one transmitter and the at least one receiver comprises: the at least one transmitter transmitting one or more predetermined bit patterns on the three conductors of the power cable to the at least one receiver; and the at least one receiver decoding the predetermined bit patterns and determining based on the decoded predetermined bit patterns which of the three conductors carries a first data bit of each triplet, which of the three conductors carries a second data bit of each triplet, and which of the three conductors carries the parity bit of each triplet.
11. An apparatus for use in communicating comms on power messages between surface equipment and downhole equipment in a well, the apparatus comprising:
a transmitter;
wherein the transmitter is configured to be coupled to a three-phase power cable;
wherein the transmitter is configured to
receive a to-be-transmitted comms on power message,
parse the to-be-transmitted comms on power message into one or more data bit pairs, and
generate a parity bit for each of the one or more data bit pairs, thereby forming a triplet,
for each of the triplets, concurrently transmit the bits of the triplet over the power cable,
wherein each of the bits are transmitted on separate conductors of the power cable.
12. The apparatus of claim 11 , wherein the apparatus comprises a transceiver that includes the transmitter and a receiver; wherein the receiver is configured to be coupled to the three-phase power cable, wherein the receiver is configured to: receive one or more triplets from the three-phase power cable; for each of the received triplets, decode the received triplet and identify the associated data bit pair; and reconstruct the data bit pairs of the received triplets into a received comms on power message.
13. The apparatus of claim 11 , wherein the transmitter is configured to generate the parity bit by summing the data bits and using the least significant bit of the sum as the parity bit.
14. The apparatus of claim 11 , wherein the transmitter is configured to transmit one or more predetermined bit patterns on the power cable prior to transmitting data associated with the comms on power message.
15. An apparatus for use in communicating comms on power messages between surface equipment and downhole equipment in a well, the apparatus comprising:
a receiver;
wherein the receiver is configured to be coupled to a three-phase power cable;
wherein the receiver is configured to
receive triplets from the three-phase power cable, wherein each triplet includes a data bit pair and a parity bit, wherein for each of the triplets, the bits of the triplet are concurrently received on separate conductors of the power cable,
for each of the received triplets, decode the triplet and thereby identify the data bit pair of the triplet, and
reconstruct the data bit pairs of one or more triplets into a comms on power message.
16. The apparatus of claim 15 , wherein the apparatus comprises a transceiver that includes the receiver and a transmitter; wherein the transmitter is configured to be coupled to the three-phase power cable, wherein the transmitter is configured to: receive a to-be-transmitted comms on power message; parse the to-be-transmitted comms on power message into one or more data bit pairs; generate a parity bit for each of the one or more data bit pairs, thereby forming a triplet; and for each of the triplets, concurrently transmit the bits of the triplet on separate conductors of the power cable.
17. The apparatus of claim 15 , wherein decoding the triplet comprises verifying that the triplet conforms to one of a set of predetermined patterns.
18. The apparatus of claim 15 , wherein decoding the triplet comprises recovering a lost bit and thereby conforming the triplet conforms to one of a set of predetermined patterns.
19. The apparatus of claim 15 , wherein the receiver is configured to receive one or more predetermined bit patterns on three conductors of the power cable; decoding the predetermined bit patterns; and determining based on the decoded predetermined bit patterns which of the three conductors carries a first data bit of each triplet, which of the three conductors carries a second data bit of each triplet, and which of the three conductors carries the parity bit of each triplet.