Abstract:
A method for providing information by optimizing the data rate to a vehicle over a three-phase power line utilized to provide power to the vehicle is described. The method includes generating carrier signals in three separate frequency bands, modulating various data onto the three carrier signals to generate three transmission signals, switching the three transmission signals onto respective conductors of the three-phase power line, demodulating the various data within the vehicle, and providing the various data to one or more vehicle systems. The three transmission signals are dynamically monitored such that the three frequency bands are controlled to optimize a data rate of the transmission.

Description:
BACKGROUND 
     The field of the disclosure relates generally to methods and systems for data communication and more particularly, to methods and systems for increasing data transmission rates in communications across a three-phase power system. 
     Vehicles such as commercial aircraft, and the various systems thereon, generate and consume considerable amounts of data. For example, engines are monitored at every stage of operation, which results in generation of significant amounts of data. Such engine monitoring data includes, for example, but not limited to compression ratios, rotation rate (RPM), temperature, and vibration data. In addition, fuel related data, maintenance, Airplane Health Monitoring (AHM), operational information, catering data, In-flight Entertainment Equipment (IFE) updates and passenger data like duty free shopping are routinely and typically generated onboard the aircraft. 
     At least some of these systems wirelessly connect to a ground system through a central airplane server and central transceiver for data transmission and reception. However, certain systems are not configured for wireless transfer of data. 
     Therefore, when an aircraft arrives at a gate, much of the data is downloaded manually from the aircraft. Specifically, data recording devices are manually coupled to interfaces on the aircraft and the data is collected from the various data generators or log books for forwarding and processing at a back office. In addition, the back office function transmits updated datasets, for example data related to a next flight(s) of the aircraft, to the aircraft. 
     Demand for additional communication channels and data transfer is driving rapid change in connection with such communications. Such increased demand is due, for example, to increasing reliance by ground systems upon data from the aircraft, as well as increased communication needs of the flight crew, cabin crew, and passengers. In addition, data diversity along with an increasing number of applications producing and consuming data in support of a wide range of aircraft operational and business processes puts additional demand on communications. 
     The electrical energy used to power commercial airplanes on the ground is 115Vac, 400 Hz, three-phase power, and includes a neutral line. It has been possible to transfer at least a portion of the data referred to above over these power lines. In one such system, a data transfer rate across a single phase (conductor) of the three-phase system up to about 65 Mbps has been accomplished. Transferring data on all three conductors of the three-phase system could triple the date rate. However, these “power stingers” used on flight lines around the world generally are fabricated using unshielded conductors. Attempting to transfer data over all three conductors, at a data rate considered to be useful for such application results in a noisy coupling between the conductors of the three-phase system. More specifically, the reduction in data rate caused by inductive and capacitive coupling of the signal and noise between the three phases on the 400 Hz ground power system results in an adverse effect on the data rate for a broadband over power line (BPL) communication system. 
     BRIEF DESCRIPTION 
     In one aspect, a method for providing information by optimizing the data rate to a vehicle over a three-phase power line utilized to provide power to the vehicle is provided. The method includes generating carrier signals in three separate frequency bands, modulating various data onto three carrier signals to generate three transmission signals, switching the three transmission signals onto respective conductors of the three-phase power line, demodulating the various data within the vehicle, and providing the various data to one or more vehicle systems. 
     In another aspect, a data communication system is provided that includes a transmission medium comprising a three-phase power line comprising a conductor associated with each respective phase, a controller, and an electrical interface to couple modulated data packages onto a plurality of conductors for transmission. The controller is operable to generate multiple carrier frequencies, separate data for transmission across the transmission medium into a plurality of separate data packages, and modulate the plurality of separate data packages with a respective one of the carrier frequencies. 
     In still another aspect, a system for transmission of broadband signals over a three-phase power line is provided. The system includes a three-phase power system and a three-phase power line comprising a plurality of conductors, where the power line is operable for transfer of three-phase power generated by the three-phase power system to a load via the conductors. The system further includes a data source, a controller communicatively coupled to the data source and programmed to configure data received from the data source into data packages for transmission along the three-phase power line, a modulation signal source. The controller may be further configured to associate a modulation frequency range with each conductor, a different modulation frequency range for each of conductors, and a modulation device (e.g., processing device) operable for modulating data packages from the controller onto one or more of the conductors using the modulation signal associated with the conductor. The controller is programmed to assign the data packages for modulation onto a specific one of the conductors based on a data rate associated with the three-phase power line. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments or may be combined in yet other embodiments, further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram of a power and digital communication transmission system. 
         FIG. 2  is a block diagram illustrating dynamic frequency selection within a power and digital communication transmission system. 
         FIGS. 3A, 3B, and 3C  are a flowchart illustrating a broadband over power line data transmission process. 
     
    
    
     DETAILED DESCRIPTION 
     The described embodiments are related to variable carrier frequency segregation between the three conductors of a broadband over power line system. Variable modulation frequency segregation overcomes the issues described herein with respect to cross coupling between the three conductors, and allows for filtering and signal separation for a tripling of the data rates as compared to current BPL systems. 
     More specifically, the described embodiments utilize frequency separation to improve signal to noise ratio in a wider range of frequency bands. Dynamic frequency selection on different phases is utilized along the different sections of the power distribution system to optimize the power rating that can be used without cross interference or interfering with other systems in physical proximity of the system. 
       FIG. 1  is a block diagram of a power and digital communication transmission system  100  in accordance with an exemplary embodiment of the disclosure. In the exemplary embodiment, power and digital communication transmission system  100  includes an electrical aircraft umbilical  102  comprising a supply end  104 , a plug end  106 , and an electrical conductor  108  extending there between. Plug end  106  is configured to mate with a vehicle such as an aircraft  110  such that electrical power is supplied to aircraft  110  through electrical conductor  108  from supply end  104 . In the exemplary embodiment, supply end  104  couples to a ground power system  112  at an airport terminal gate  114 . Ground power system  112  is configured to receive electrical power from a power supply through a power supply conduit  115 . In other embodiments, ground power system  112  is located on a pier to couple to a boat, barge, or ship (not shown). In still other embodiments, ground power system  112  is positioned at a garage or service facility and is configured to couple to a wheeled vehicle, for example, but not limited to a car, a recreational vehicle (RV), or a train. Additionally, ground power system  112  may comprise another vehicle, such as a space vehicle, undersea or sea surface vehicle wherein one or both vehicles are moving with respect to each other and/or their surroundings while coupled through umbilical  102 . 
     Power and digital communication transmission system  100  also includes a first interface device  116  electrically coupled to supply end  104 . In the exemplary embodiment, interface device  116  is electrically coupled to supply end  104  through power supply conduit  115  and ground power system  112 . In an alternative embodiment, interface device  116  is electrically coupled to supply end  104  downstream of ground power system  112 . In one embodiment, ground power system  112  is a distributed power system operating at voltages that are incompatible with aircraft  110 . In such embodiments, a point of use power system  117  is utilized to step the voltage to a level that is compatible with aircraft  110 . In another alternative embodiment, interface device  116  is electrically coupled to electrical conductor  108  internal to ground power system  112 . Interface device  116  is also coupled to a network  118  through a wired network access point  120  or a wireless communication link  122 . 
     Power and digital communication transmission system  100  also includes a second interface device  124  electrically coupled to plug end  106  when umbilical  102  is coupled to aircraft  110 . In the exemplary embodiment, interface device  124  is electrically coupled to an onboard power bus  125  through plug end  106  through an umbilical plug  126  penetrating a fuselage  128  of aircraft  110 . Interface device  124  is also coupled to an onboard network  129  through an onboard wired network access point  130  or an onboard wireless communication link  132 . 
     First interface device  116  is configured to transmit and receive data carrier signals though electrical conductor  108  while power is supplied to aircraft  110  through electrical conductor  108 . First interface device  116  is also configured to convert the data carrier signals from and to a predetermined data format on the network. Second interface device  124  is electrically coupled to plug end  106  when umbilical  102  is coupled to aircraft  110 . Second interface device  124  (e.g., a receiver and a transmitter, onboard transceiver) is configured to transmit and receive the data carrier signals between first interface device  116  and onboard network  129  while power is supplied to aircraft  110  through electrical conductor  108 . In the exemplary embodiment, each of first interface device  116  and second interface device  124  are configured to detect a communication link established through the electrical conductor and report the link to system  100 . Interface units  116  and  124  are electrically matched with the characteristics of umbilical  102  including but not limited to wire size, shielding, length, voltage, load, frequency, and grounding. 
     In the exemplary embodiment, the predetermined data format is compatible with various network protocols including but not limited to, Internet network protocol, gatelink network protocol, Aeronautical Telecommunications Network (ATN) protocol, and Aircraft Communication Addressing and Reporting System (ACARS) network protocol. 
     In the exemplary embodiment, high-speed network service to aircraft  110  while parked in a service location such as an airport terminal gate is provided through a conductor of the aircraft ground power umbilical using for example, but not limited to Broadband over Power Line (BPL), X10, or similar technology. Use of this technology permits the airports and airlines to add a simple interface to the aircraft umbilical at the gate and for aircraft manufacturers to provide a matching interface within the aircraft to permit broadband Internet service to the aircraft through an aircraft power link in the umbilical. 
     Broadband over Power Line (BPL) is a technology that allows Internet data to be transmitted over power lines. (BPL is also sometimes called Power-line Communications or PLC.) Modulated radio frequency signals that include digital signals from the Internet are injected/added/modulated onto the power line using, for example, inductive or capacitive coupling. These radio frequency signals are injected into the electrical power conductor at one or more specific points. The radio frequency signals travel along the electrical power conductor to a point of use. Little, if any, modification is necessary to the umbilical to permit transmission of BPL. The frequency separation in the umbilical substantially minimizes crosstalk and/or interference between the BPL signals and other wireless services. BPL permits higher speed and more reliable Internet and data network services to the aircraft than wireless methods. Using BPL also eliminates the need to couple an additional separate cable to aircraft  110  because it combines aircraft electrical power and Internet/data services over the same wire. System  100  uses for example, an approximately 2.0 MHz to approximately 80.0 MHz frequency or X10 similar ranges with the exact frequency range use defined and engineered by the characteristics and shielding of umbilical  102  and the allowable RFI/EMI levels in that particular environment. 
     In an embodiment, symmetrical hi-broadband BPL is used in umbilical  102  to transmit at communication speeds with aircraft  110  at rates in the tens or hundreds of megabits per second (Mbps). Because the BPL link is dedicated to only one aircraft  110  and not shared as wireless is, actual throughput can be from two to ten times the wireless throughput in the same environment. In addition, the throughput is stable and reliable in airport environments, whereas the existing wireless Gatelink services vary with the amount of RF interference and congestion at each airport. 
     However, and as described above, such systems are limited to a data transfer across a single phase (conductor) of the three-phase system due to, for example, crosstalk that occurs between the conductors of the tree-phase electrical conductor  108 . More specifically, each of the three wires running together in electrical conductor  108 , which is sometimes referred to as a three-phase stinger, is susceptible to RF energy from the other conductors running parallel to them. This cross noise results in a higher noise floor, results in a lower signal to noise ratio and therefore reduced data rates. This cross noise coupling results in an adverse effect on the data rate for a Broadband over Powerline Communication (BPL) system. 
     The following paragraphs describe the use of frequency separation to improve the signal to noise ratio in a wider range of frequency bands. Specifically, dynamic frequency selection is utilized on each conductor (e.g., each different phase of the three-phase system) and along the different sections of the power distribution system to optimize the power rating that can used without cross interference or interfering with other systems in physical proximity of the system. 
     Specifically,  FIG. 2  is a block diagram  200  illustrating dynamic frequency selection. The three conductors  202 ,  204 , and  206  represent the three conductors of electrical conductor  108  described above as providing power and data to aircraft  110 . A controller  210  receives data  212  from a data source  214  for transmission to aircraft  110  via conductors  202 ,  204 , and  206 . The controller is programmed to divide the data into three sets of data messages which are indicated as data  1  ( 220 ), data  2  ( 222 ) and data  3  ( 224 ). Three separate frequency generators  230 ,  232 , and  234  are also controlled in operation by controller  210  and correspond to data  1  ( 220 ), data  2  ( 222 ) and data  3  ( 224 ). Data  1   220  is modulated with an output  240  of frequency generator  230  by modulator  242  to create a data transmission message. An output  244  of modulator  242  is then further modulated with one phase  246  of the three-phase power from ground power system  112  by modulator  248 , to produce a first data transmission on power line signal  202  to be conducted to aircraft by electrical conductor  108 . 
     Similarly, data  2   222  is modulated with an output  250  of frequency generator  232  by modulator  252  to create a data transmission message. An output  254  of modulator  252  is then further modulated with one phase  256  of the three-phase power from ground power system  112  by modulator  258 , to produce a second data transmission on power line signal  204  to be conducted to aircraft by electrical conductor  108 . Likewise, data  3   224  is modulated with an output  260  of frequency generator  234  by modulator  262  to create a data transmission message. An output  264  of modulator  262  is then further modulated with one phase  266  of the three-phase power from ground power system  112  by modulator  268 , to produce a third data transmission on power line signal  206  to be conducted to aircraft by electrical conductor  108 . 
     To overcome the problems described above, each of the frequency generators  230 ,  232 ,  234  operate over a different frequency spectrum. Further, controller  210  is programmed to determine a data rate associated with the three separate data transmission units and dynamically adjust the carrier frequencies generated by the three frequency generators  230 ,  232 ,  234  such that the conductors for all three phases of the three-phase power system are usable for data transmission with managed frequency segregation. 
     In the described embodiments, carrier frequencies that do not interfere with aircraft systems are utilized in the areas above ground near the aircraft  110 . In this way, the described system embodiments are managed with a focus of being compatible in an airplane environment, to avoid disrupting avionics systems and communications. Carrier frequencies up to 80 MHz are utilized for BPL in the described embodiments, which are separated in frequency from critical airplane frequencies, and which allow for use of more energy and results in higher data rates. In a specific embodiment, frequency generator  230  is configured to provide a carrier frequency ranging between about 2 MHz to about 30 MHz (e.g. single signal, single data signal), frequency generator  232  is configured to provide a carrier frequency ranging between about 30 MHz to about 55 MHz, and frequency generator  234  is configured to provide a carrier frequency ranging between about 55 MHz to about 80 MHz which therefore provides the frequency separation described herein. 
     Those skilled in the art will understand that at aircraft  110 , a similar configuration is provided for the separation of data and power from the separate conductors, and that the three separate data transmission packages may be combined for output to a single system on board the aircraft. Several scenarios are possible including using the three separate conductors (e.g., multiple conductors) and three data transmission packages (e.g., multiple data packages, multiple modulated data packages) to transmit data that is completely unrelated, with the data packages (e.g., specific data package) ultimately intended for receipt by three separate systems on board the aircraft  110 . 
     In embodiments, the carrier frequencies on each of the phases are dynamically adjusted to accommodate any physical changes in the BPL system that might impact the characteristic of the conductor  108 . As an example, measurements have shown that an airline mechanic, by simply putting his hand close (within 3 inches) to the conductor  108 , can have a dramatic effect on the impedance characteristics and the frequency response of the conductor  108 . Controller  210  provides a sense and control system that allows these changes to be managed and further optimized. To accomplish the above, the carrier frequencies can be controlled and changed in both the primary and secondary elements of the power distribution system. Further, controller  210  is programmed to monitor and track data trends across the three-phase conductors and provide predictive control changes based on one or more of use patterns, aircraft type, weather and electrical load. 
     It is mentioned above that the data to be transmitted can be either originate from a single data source and be divided into three portions, or that the data originates from more than one data source and is subsequently routed to the separate conductors of the three-phase power line.  FIGS. 3A, 3B, and 3C  are a flowchart  300  that illustrates intelligent phase and frequency selection utilizing the above described embodiments. For example, and beginning with  FIG. 3A , for a pending transmission  302  to be routed on phase A, it is determined  304  whether the transmission application/operation requires a high throughput. If the determination  304  is that the transmission application/operation does not require a high throughput, a time delay occurs  306 , for example for 20 seconds (e.g., a predetermined period), to allow for any prior transmissions on the three conductors (e.g., multiple conductors) to be completed and the transmission  302  occurs on the phase A conductor (e.g., single conductor). 
     If the transmission application/operation requires a higher throughput, the phase B conductor is added  310  (e.g., additional conductor) to the transmission (e.g., now two conductors). If it is determined  312  that the transmission application/operation does not require still higher throughput, a time delay occurs  314 , for example for 20 seconds, to allow for any prior transmissions on the three conductors to be completed and the transmission  310  occurs on the phase A and phase B conductors. If the transmission application/operation requires a still higher throughput, the phase C conductor is added  320  to the transmission. Moving to  FIG. 3B , as the three conductors of the three-phase power line are being utilized  322  for transmission, the system repeatedly verifies  323  whether the data rate is optimized for the three phases and verifies  324  whether the transmission is completed. Once completed, transfer is stopped  326 , and now moving to  FIG. 3C , data related to the transfer is utilized  328  for statistical trending. If the transmission data rate was not within the optimal data rate, parameters are modified  330  from an alpha set of parameters 
     With regard to trending, if all three conductors were used  340  for a transmission, the system determines  342  if the transmission data rate was at least, for example, 93% of an optimal data rate, the optimal data rate being selected by a user or determined from statistical results. The empirical data can be utilized in a variety of methods. For example, the historical performance can be averaged or used in a weighted running average or other advanced statistical method for trending optimization. If the transmission data rate was within the range of the optimal data rate (either mathematical, models or empirical, an existing phase-data balance is maintained  344 ). 
     If all three conductors were not used  340  for a transmission, the system applies  350  pulses to the unused conductors to determine one or more of an electrical load, noise and capacity, with the results being utilized  328  in the statistical trending. If the transmission data rate was not within the optimal data rate, parameters are modified  360  from an alpha set of parameters. For example and as described herein, the carrier frequencies associated with each conductor may be adjusted in an attempt to provide an increase to the data rate across the conductors. As would be applied to the example frequencies mentioned above, the carrier associated with phase A would be adjusted to a different frequency within the 2 MHz to 30 MHz band, the carrier associated with phase B would be adjusted to a different frequency within the 30 MHz to 55 MHz band, and the carrier associated with phase C would be adjusted to a different frequency within the 55 MHz to about 80 MHz band to determine which carrier frequency combinations, for example, provide the best throughput. 
     Although described with respect to an aircraft broadband power line application, embodiments of the disclosure are also applicable to other vehicles such as ships, barges, and boats moored at a dock or pier and also wheeled vehicles parked in a service area. 
     The above-described methods and systems for transmitting power and digital communication to provide high speed Internet service support directly to the aircraft while at the gate are cost-effective, secure and highly reliable. The methods and systems include integration and use of BPL or X10 similar technology into the aircraft and airport infrastructure to support broadband Internet and data services to the aircraft with minimal infrastructure impacts and cost. The integration of BPL, X10, or similar technology into the airport and aircraft permit using the existing aircraft gate umbilical to provide the aircraft with high-speed and high reliability Internet and data services from the airport gate. Accordingly, the methods and systems facilitate transmitting power and digital communication in a cost-effective and reliable manner. 
     This written description uses examples to disclose various embodiments, which include the best mode, to enable any person skilled in the art to practice those embodiments, including making and using any devices or systems and performing any incorporated methods. The patentable scope is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.