We noticed recently the flood of job openings at the FDIC and have to surmise that they’re expecting the worst with the number of “problem banks” increasing again this year.
The link to the FDIC job listings is here:
https://jobs1.quickhire.com/scripts/fdic.exe/runuserinfo?Haveusedbefore=5
On August 14, 2009, First Mercury Financial Corporation (FMR) reported that they had purchased an
additional 72,246,560 million shares of Sirius/XM Radio representing a 15358.43 % increase
with their SIRI holdings.
You can review all of FMR Corp’s purchases at their latest SEC Edgar filing here:
http://www.sec.gov/Archives/edgar/data/315066/0000315066-09-003476.txt
On August 17, 2009, Morgan Stanley reported that they had purchased an additional 18,043,086 million
shares of Sirius/XM Radio.
You can review all of Morgan Stanley’s purchases at their latest SEC Edgar filing here:
http://www.sec.gov/Archives/edgar/data/895421/0000895421-09-000696.txt
| United States Patent | 7,577,519 |
| Adamczyk , et al. | August 18, 2009 |
| Inventors: | Adamczyk; Maria (Alpharetta, GA), Silver; Edward (Atlanta, GA) |
| Assignee: | AT&T Intellectual Property, I, L.P. (Wilmington, DE) |
| Appl. No.: | 11/868,585 |
| Filed: | October 8, 2007 |
| Application Number | Filing Date | Patent Number | Issue Date | ||
| 11022442 | Dec., 2004 | 7289903 | |||
| Current U.S. Class: | 701/207 ; 340/932.2 |
| Current International Class: | G01C 21/26 (20060101); G07C 1/30 (20060101) |
| Field of Search: | 701/200,207-208,213-215 340/988,991-992,932.2 |
| 4876540 | October 1989 | Berthon et al. |
| 5091727 | February 1992 | Mahmood |
| 5289369 | February 1994 | Hirshberg |
| 5414624 | May 1995 | Anthonyson |
| 5745052 | April 1998 | Matsuyama et al. |
| 7289903 | October 2007 | Adamczyk et al. |
Primary Examiner: Beaulieu; Yonel
Attorney, Agent or Firm: Cantor Colburn LLP
This application is a continuation of U.S. patent application Ser. No. 11/022,442, filed Dec. 22, 2004, now U.S. Pat. No. 7,289,903, the entire contents of which are incorporated herein by reference.
1. A method for implementing a locator service, comprising: receiving, at a computer system, object identification information and location identification information from a vehicle, the location identification information indicating the presence of the vehicle at a parking space; creating an occupancy record that includes the object identification information and the location identification information; and collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record; wherein the location identification information is received at the computer system via a radio frequency identifier associated with the parking space, the radio frequency identifier detecting the presence of the vehicle at the parking space.
2. The method of claim 1, wherein the object identification information includes at least one of: the operator of the vehicle; an identification associated with the operator; and a description of the vehicle.
3. The method of claim 1, further comprising: receiving a request to locate the vehicle during the exiting process, the request including at least a portion of the objection identification information; retrieving the location identification information from the occupancy record associated with the object identification information; and presenting the location identification information of the parking space to the operator.
4. The method of claim 1, wherein collecting fees includes: tracking, in the occupancy record, an amount of time the vehicle occupies the parking space; and associating the amount of time with an occupancy fee.
5. The method of claim 1, wherein the location identification information is received at the computer system, over a wireless network, via a global positioning system on the vehicle, the global positioning system receiving the location identification information from the radio frequency identifier.
6. The method of claim 1, wherein collecting fees comprises: flagging the object identification information in the occupancy record to distinguish the vehicle, and a service package provided to the operator of the vehicle, from other vehicles; and implementing payment services for the occupancy based upon terms of the service package.
7. The method of claim 1, further comprising: assigning a unique code to the location identification information to distinguish the corresponding parking space from other parking spaces; and reserving the parking space having the unique code for preferred customers.
8. A system for implementing a locator service, comprising: a computer system executing a locator application; and a storage device in communication with the computer system, the storage device housing occupancy records generated via the locator application, the locator application performing: receiving, at the computer system, object identification information and location identification information from a vehicle, the location identification information indicating the presence of the vehicle at a parking space; creating an occupancy record that includes the object identification information and the location identification information; and collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record; wherein the location identification information is received at the computer system via a radio frequency identifier associated with the parking space, the radio frequency identifier detecting the presence of the vehicle at the parking space.
9. The system of claim 8, wherein the object identification information includes at least one of: the operator of the vehicle; an identification associated with the operator; and a description of the vehicle.
10. The system of claim 8, wherein the locator application further implements: receiving a request to locate the vehicle during the exiting process, the request including at least a portion of the objection identification information; retrieving the location identification information from the occupancy record associated with the object identification information; and presenting the location identification information of the parking space to the operator.
11. The system of claim 8, wherein collecting fees includes: tracking, in the occupancy record, an amount of time the vehicle occupies the parking space; and associating the amount of time with an occupancy fee.
12. The system of claim 8, wherein the location identification information is received at the computer system, over a wireless network, via a global positioning system on the vehicle, the global positioning system receiving the location identification information from the radio frequency identifier.
13. The system of claim 8, wherein collecting fees comprises: flagging the object identification information in the occupancy record to distinguish the vehicle, and a service package provided to the operator of the vehicle, from other vehicles; and implementing payment services for the occupancy based upon terms of the service package.
14. A computer program product for implementing locator services, the computer program product including instructions for causing a computer system to implement a method, comprising: receiving, at the computer system, object identification information and location identification information from a vehicle, the location identification information indicating the presence of the vehicle at a parking space; creating an occupancy record that includes the object identification information and the location identification information; and collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record; wherein the location identification information is received at the computer system via a radio frequency identifier associated with the parking space, the radio frequency identifier detecting the presence of the vehicle at the parking space.
15. The computer program product of claim 14, wherein the object identification information includes at least one of: the operator of the vehicle; an identification associated with the operator; and a description of the vehicle.
16. The computer program product of claim 14, further comprising instructions for performing: receiving a request to locate the vehicle during the exiting process, the request including at least a portion of the objection identification information; retrieving the location identification information from the occupancy record associated with the object identification information; and presenting the location identification information of the parking space to the operator.
17. The computer program product of claim 14, wherein collecting fees includes: tracking, in the occupancy record, an amount of time the vehicle occupies the parking space; and associating the amount of time with an occupancy fee.
18. The computer program product of claim 14, wherein the location identification information is received at the computer system, over a wireless network, via a global positioning system on the vehicle, the global positioning system receiving the location identification information from the radio frequency identifier.
19. The computer program product of claim 14, wherein collecting fees comprises: flagging the object identification information in the occupancy record to distinguish the vehicle, and a service package provided to the operator of the vehicle, from other vehicles; and implementing payment services for the occupancy based upon terms of the service package.
20. The computer program product of claim 14, further comprising instructions for performing: assigning a unique code to the location identification information to distinguish the corresponding parking space from other parking spaces; and reserving the parking space having the unique code for preferred customers.
Exemplary embodiments relate generally to wireless communications, and more particularly, to methods, systems, and computer program products for implementing a locator service.
Wireless technologies have grown in popularity for a variety of applications. For example, in the personal consumer market, wireless home networking devices provide configurable internetworking solutions for various types of home devices such as communications, computing, and entertainment devices.
On a larger scale, wireless technologies such as global satellite communications offer global positioning services for mobile devices. For example, GPS services provide mapping and direction assistance to travelers. Global positioning services are also utilized to track the location of vehicles in an effort to minimize theft. Another popular market relating to global satellite technology is the satellite radio and programming industry. Many vehicles are now equipped with wireless receivers that pick up satellite music and programming from all over the world (e.g., services provided by XM Satellite Radio, Inc. of Washington, D.C. as well as SIRIUS Satellite Radio of New York City, N.Y.). These types of applications typically involve a subscription service to a service provider.
In addition to personal consumer applications, business applications relating to wireless technologies have also enjoyed great advancements (e.g., wireless area networks, cellular communications for field activities, etc.).
As wireless technologies continue to advance, consumers, business entities, government, military, and other organizations will continue to look for ways to exploit them.
SUMMARY OF THE INVENTION
Exemplary embodiments relate to methods, systems, and computer program products for implementing a locator service. A method includes receiving, at a computer system, object identification information and location identification information from a vehicle. The location identification information indicates the presence of the vehicle at a parking space. The method also includes creating an occupancy record that includes the object identification information and the location identification information. The method further includes collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record. The location identification information is received at the computer system via a radio frequency identifier associated with the parking space.
Systems for implementing a locator service include a computer system executing a locator application and a storage device in communication with the computer system. The storage device houses occupancy records generated via the locator application. The locator application implements a method. The method includes receiving, at the computer system, object identification information and location identification information from a vehicle. The location identification information indicates the presence of the vehicle at a parking space. The method also includes creating an occupancy record that includes the object identification information and the location identification information. The method further includes collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record. The location identification information is received at the computer system via a radio frequency identifier associated with the parking space.
Computer program products for implementing a locator service include instructions for causing a computer system to implement a method. The method includes receiving, at the computer system, object identification information and location identification information from a vehicle. The location identification information indicates the presence of the vehicle at a parking space. The method also includes creating an occupancy record that includes the object identification information and the location identification information. The method further includes collecting fees from an operator of the vehicle during an exiting process based upon information in the occupancy record. The location identification information is received at the computer system via a radio frequency identifier associated with the parking space.
Other systems, methods, and/or computer program products according to exemplary embodiments will be or become apparent to one with skill in the art upon review of the following drawings and detailed description. It is intended that all such additional systems, methods, and/or computer program products be included within this description, be within the scope of the present invention, and be protected by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Referring now to the drawings wherein like elements are numbered alike in the several FIGURES:
FIG. 1 is a block diagram of an environment in which the locator service system functions may be implemented in exemplary embodiments;
FIG. 2 is a flow diagram of a process for implementing a locator service in exemplary embodiments; and
FIG. 3 is a sample database of occupancy records generated via the locator service system in exemplary embodiments.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION
In accordance with exemplary embodiments, locator services are provided. Locator services provide the ability to detect and track the location of objects via wireless communications systems. The locator services also provide the ability to manage identifying information relating to the object being tracked and may enable service fees to be implemented for the locator service. While described herein with respect to an automobile locator service, it will be understood by those skilled in the art that the functions described with respect to the locator service may be applied to any type of object that is mobile for which tracking services are desired.
Turning now to FIG. 1, an environment in which the locator service activities may be implemented will now be described. In accordance with exemplary embodiments, the system 100 of FIG. 1 refers to an area, such as a parking area (e.g., garage, lot, etc.). The parking area of system 100 may be, e.g., a parking facility for an amusement park, an office complex, a shopping mall, a sports area, an airport, or other similar type of complex facility that provides substantial parking services to its clientele. The parking area of system 100 may be an indoor, outdoor, or combination of parking facilities and may further provide value-added services such as valet parking. It should be appreciated that the invention is not limited to tracking mobile/portable devices in parking areas but is applicable to tracking occupancy of any type of mobile or portable device within any location.
According to an exemplary embodiment, the entity providing the locator services for parking area of system 100 includes a computer system 102 (processor device) that executes a locator application 104 and a reader 106. The locator services may be managed by a third-party provider system on behalf of the entity managing the parking area 100, which provides the locator services to the parking area entity for a fee. In exemplary embodiments, the locator services are provided directly by the parking area entity of system 100 and, in particular, by the computer system 102. The computer system 102 may handle sending and receiving information to and from other entities in the parking area of system 100 and may perform associated tasks.
In alternative embodiments, the computer system 102 may be in communication with one or more additional computer systems that, together, provide locator service activities over a network 109 to multiple locations (e.g., multiple parking garages owned by a business enterprise in New York City or an airport parking lot providing information regarding location to one or more area hotels). If the locator services are provided jointly by multiple entities, the locator service processing may be shared by their respective computer devices over the network 109 as further described herein.
According to an exemplary embodiment, locator application 104 receives location identification information from mobile or portable objects (e.g., mobile device 116) via, e.g., a wireless fidelity (WiFi) network. While the description that follows refers to mobile devices, in particular vehicles, for illustrative purposes, it will be appreciated that the invention may also be applicable to tracking of other types of portable devices. The WiFi network comprises base stations 114, WiFi card 118, and reader 106. These components are described further herein. The locator application 104 associates location identification information to corresponding mobile object identifiers (identification information) for objects (e.g., 116) that occupy a location 110. The locator application 104 tracks these associations for multiple objects and locations in occupancy records that are stored in storage device 108. The locator application 104 may also include a timing device (e.g., a timestamp function) that tracks occupancy duration and may further provide payment services for an occupancy based upon the duration of the occupancy or other criteria. The functions provided by the locator application 104 are further described in the flow diagram of FIG. 2.
Reader 106 receives transmissions from automatic identifiers 112 via the WiFi network as described further herein. The transmissions comprise a serial number or other identification as described further herein with respect to the automatic identifiers 112. Reader 106 converts the radio waves reflected back from the automatic identifier 112 into digital information that may be used by the locator application 104. The reader 106 may comprise a device that includes signal conditioning, parity error checking, and correction. The reader 106 receives signals from the WiFi network, verifies the signals, and decodes them. An algorithm may also be applied to determine if a signal is a repeat transmission. In this manner, the reader 106 would then send a signal to the appropriate automatic identifier 112 to cease signaling.
In exemplary embodiments, the system 100 shown in FIG. 1 includes a storage device 108. Storage device 108 is in communication with computer system 102 and may be implemented using a variety of devices for storing electronic information. It is understood that the storage device 108 may be implemented using memory contained in the computer system 102 or it may be a separate physical device. If the locator services are provided over a network (e.g., 109), the storage device 108 may be logically addressable as a consolidated data source across a distributed environment that includes the network. Information stored in the storage device 108 may be retrieved and manipulated via the computer system 102. The storage device 108 houses one or more databases of occupancy information. Sample database information is shown and described in FIG. 3.
Network 109 may be any type of known network including, but not limited to, a wide area network (WAN), a local area network (LAN), a global network (e.g. Internet), a virtual private network (VPN), and an intranet. The network 109 may be implemented using a wireless network or any kind of physical network implementation known in the art. The computer system 102 may be connected to the network 109 in, e.g., a wireless fashion.
Locations 110 refer to a defined area or space for which the presence or occupancy of a mobile object is tracked. For illustrative purposes, locations 110 are referred to in this description as parking spaces in a parking area.
Automatic identifiers 112 may comprise a radio frequency identification (RFID) transponder (also referred to as RFID tag) that utilizes radio waves for identifying objects, as one skilled in the art would appreciate. Each of automatic identifiers 112 may include a microchip that stores a serial number or other means of identifying a corresponding location 110. The automatic identifier 112 may also include an antenna attached to the microchip. The antenna enables the microchip to transmit the location identification information to reader 106 and/or mobile object 116.
As shown in FIG. 1, base stations 114 are dispersed throughout the parking area of system 100. Base stations 114 receive and transmit wireless signals between one another as well as between automatic identifiers 112, mobile object 116, and reader 106.
Mobile objects 116 may be, for example, a vehicle such as an automobile, motorcycle, bus, truck, to name a few. For purposes of illustration, the mobile object 116 will be described herein with respect to a WiFi- and GPS-enabled automobile.
According to an exemplary embodiment, mobile object 116, depicted for illustrative purposes in FIG. 1 as an automobile, includes a WiFi card 118 that enables the object 116 to communicate over any type of 802.11 network. The WiFi card 118, base stations 114, and reader 106 are collectively referred to herein as a WiFi network.
Mobile object 116 further includes a GPS card/application 120 that provides tracking and navigation assistance to the operator of automobile 116. The GPS card 120 may comprise a commercial application such as Garmin Quest GPS Navigator.TM. provided by Garmin International of Olathe, Kans.
Turning now to FIG. 2, a flow diagram of a process for implementing locator services will now be described with respect to an automobile. As indicated above, the locator services provide the ability to detect and track the location of objects via wireless communications systems. For example, consider a mobile object 116 that enters the parking area of system 100 and parks in one of locations 110. At step 202, GPS application 120 in the mobile object 116 detects a signal being emitted by the automatic identifier 112. The signal emitted provides the identification of the location 110 that has been accessed by the mobile object 116.
At step 204, the mobile object 116 passes the location identification information, as well as the mobile object identifiers, to the reader 106 via the GPS application 120 and the WiFi network. This may be accomplished by transmitting the location identification information and mobile object identifiers to one of base stations 114 which, in turn, passes the signals in a wireless fashion to either another base station 114 (depending upon the distance between mobile object 116 and the reader 106, or directly to the reader 106. The mobile object identifiers may include the name of an operator of the mobile object, an operator identification (e.g., social security number, drivers license number, etc.), a description of the mobile object (e.g., make, model, color, etc.), or any other type of desired indicia. The reader 106 converts the signals received into a digital form that is understood by the locator application 106.
The locator application 104 receives the converted signals and associates the mobile object identifiers with the automatic identifier information (i.e., location identification information) at step 206 and stores the results in occupancy database of storage device 108. A sample database 300 is shown in FIG. 3.
Database 300 of FIG. 3 includes a record for each of locations 110 as shown in column 302. Database 300 further includes a column 304 for associating the mobile object identifier with a corresponding location 110. If desired, the database 300 may include a column 306 for tracking the duration of time a location 110 is occupied by a mobile device. Column 308 displays any fees charged for the occupation of the location 110. A sample record 310 is shown in database 300 and includes a sampling of mobile object identifiers 312 that may be utilized by the locator application 104, particularly when responding to operator requests to retrieve location information as will be described further herein.
This information is retained in the occupancy database of storage device 108 of FIG. 1 until the operator of the mobile device activates an exit process. At step 208, the operator enters identification information into reader 106 of FIG. 1. The identification information required may include all, or a portion of, the mobile object identifier information transmitted to the locator application 104 in step 204. Utilizing the mobile object identifier information, the locator application 104 retrieves the associated automatic identifier information (i.e., location identification information) from the occupancy database of storage device 108 at step 210. The automatic identification information is presented to the operator at step 212. This information may be displayed to the operator on, e.g., a computer monitor associated with computer device 102, or may be printed out for the operator.
Optionally, any fees that may have accrued may be handled via the locator application 104, if desired, at step 214. For example, the operator may be provided with the option to pay for any parking fees based upon, e.g., the amount of time the mobile device 116 has been parked in the location 110. In further embodiments, the locator application 104 may include a service for preferred customers (e.g., repeat business) or for customers who purchase inclusive packages (e.g., season tickets at an amusement park or ball park include free parking), such that the identifier information transmitted to the locator application 104 may include a special code or flag that distinguishes these types of individuals from the general public. Alternatively, the location 110 itself may be reserved for preferred customers such that the automatic identification information includes a unique code that distinguishes the location’s occupant from others (e.g., the first row of each parking section is reserved for preferred customers).
At step 216, the locator application 104 purges the occupancy record from the database of storage device 108 (FIG. 1) indicating that the location 110 is unoccupied. The process returns to step 202 each time a location 110 becomes occupied.
As indicated above, the locator services provide the ability to detect and track the location of objects via wireless communications systems. The locator services also provide the ability to manage identifying information relating to the object being tracked and may enable service fees to be implemented for the locator service.
As described above, embodiments may be in the form of computer-implemented processes and apparatuses for practicing those processes. In exemplary embodiments, the invention is embodied in computer program code executed by one or more network elements. Embodiments include computer program code containing instructions embodied in tangible media, such as floppy diskettes, CD-ROMs, hard drives, or any other computer-readable storage medium, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. Embodiments include computer program code, for example, whether stored in a storage medium, loaded into and/or executed by a computer, or transmitted over some transmission medium, such as over electrical wiring or cabling, through fiber optics, or via electromagnetic radiation, wherein, when the computer program code is loaded into and executed by a computer, the computer becomes an apparatus for practicing the invention. When implemented on a general-purpose microprocessor, the computer program code segments configure the microprocessor to create specific logic circuits.
While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.
On July 15, 2009, Goldman Sachs reported that they had purchased an additional 9 million shares of Sirius/XM Radio.
You can review all of Goldman Sach’s purchases at their latest SEC Edgar filing here:
http://www.sec.gov/Archives/edgar/data/886982/0000769993-09-000863.txt
Systems, methods and apparatus are described to interleave LDPC coded data for reception over a mobile communications channel, such as, for example, a satellite channel. In exemplary embodiments of the present invention, a method for channel interleaving includes segmenting a large LDPC code block into smaller codewords, randomly shuffling the code segments of each codeword and then convolutionally interleaving the randomly shuffled code words. In exemplary embodiments of the present invention, such random shuffling can guarantee that no two consecutive input code segments will be closer than a defined minimum number of code segments at the output of the shuffler. In exemplary embodiments of the present invention, by keeping data in, for example, manageable sub-sections, accurate SNR estimations, which are needed for the best possible LDPC decoding performance, can be facilitated based on, for example, iterative bit decisions.
| U.S. Current Class: | 714/752; 714/E11.032 |
| U.S. Class at Publication: | 714/752; 714/E11.032 |
| Intern’l Class: | H03M 13/27 20060101 H03M013/27; G06F 11/10 20060101 G06F011/10 |
2. The method of claim 1, wherein said convolutionally interleaving achieves at least a defined minimum time dispersion.
3. The method of claim 1, wherein the subsections are some small percentage of the large code block’s size.
4. The method of claim 1, wherein said convolutional interleaving includes applying an entire subsection to each arm of a convolutional interleaver.
5. A system, comprising:a transmitter comprising:an LDPC encoder;a random shuffler; anda convolutional interleaver; anda receiver comprising:a de-interleaver;a de-shuffler; andan LDPC decoder.
6. The system of claim 5, wherein the convolutional interleaver has one branch for each subsection of data.
7. The system of claim 5, wherein the random shuffler is an S-random shuffler.
8. The system of claim 7, wherein said S-random shuffler is designed to guarantee that no two consecutive input segments of a subsection will be closer than Y segments at the output of the shuffler, where Y is approximately equal to [Sqrt (X)]/2, where X=total number of segments.
9. A transmitter, comprising:an LDPC encoder;a random shuffler; anda convolutional interleaver.
10. The transmitter of claim 9, wherein the convolutional interleaver has one branch for each segment of data.
11. The transmitter of claim 9, wherein the random shuffler is an S-random shuffler.
12. The transmitter of claim 11, wherein said S-random shuffler is designed to guarantee that no two consecutive input segments will be closer than than Y segments at the output of the shuffler, where Y is approximately equal to [Sqrt (X)]/2, where X=total number of segments.
13. The system of claim 5, wherein the readout order of said random shuffler is at least one of controlled by a lookup table and different for each code block within a transmission frame.
14. The system of claim 13, wherein said lookup table can repeat itself after every transmission frame.
15. A receiver comprising:a de-interleaver;a de-shuffler; andan LDPC decoder.
16. The receiver of claim 15, wherein in operation the LDPC decoder first estimates a noise variance for each code segment based on traditional noise variance cluster estimates.
17. The receiver of claim 16, wherein the noise variance for each code segment is re-calculated on every iteration of the LDPC decoder.
18. A program storage device readable by a processing unit, tangibly embodying a program of instructions executable by the processing unit to implement a method of interleaving Low Density Parity Check (LDPC) codes over mobile satellite channels, said method comprising:segmenting a large LDPC code block into smaller subsections, each subsection having multiple segments;randomly shuffling the segments in each subsection;convolutionally interleaving the subsections; andtransmitting the interleaved subsections over a satellite channel to a mobile receiver.
19. The program storage device of claim 18, wherein said convolutionally interleaving achieves at least a defined minimum time dispersion.
20. The program storage device of claim 18, wherein the subsections are some small percentage of the large code block’s size.
21. The program storage device of claim 18, wherein said convolutional interleaving includes applying an entire subsection to each arm of a convolutional interleaver.
[0001]This application claims the benefit of and hereby incorporates by reference U.S. Provisional Patent Application No. 60/963,043, entitled METHOD AND APPARATUS FOR INTERLEAVING LOW DENSITY PARITY CHECK (LDPC) CODES OVER MOBILE SATELLITE CHANNELS, and filed on Aug. 1, 2007.
TECHNICAL FIELD
[0002]The present invention relates to satellite broadcast communications, and more particularly to systems and methods for interleaving LDPC coded data over mobile satellite channels.
BACKGROUND INFORMATION
[0003]Mobile receivers of satellite broadcast communications are often faced with signal fades of long duration in particular locations and at particular times. This can be more or less egregious depending upon a given channel’s fading characteristics. It is well known that time interleaving a communication signal can be a very effective method to transform a time fading channel into a memory-less channel.
[0004]What is thus needed in the art are systems and methods to interleave LDPC coded data for better reception over a mobile satellite channel.
SUMMARY OF THE INVENTION
[0005]Systems, methods and apparatus are described to interleave LDPC coded data for reception over a mobile communications channel, such as, for example, a satellite channel. In exemplary embodiments of the present invention, a method for channel interleaving includes segmenting a large LDPC code block into smaller codewords, randomly shuffling the code segments of each codeword and then convolutionally interleaving the randomly shuffled code words. In exemplary embodiments of the present invention, such random shuffling can guarantee that no two consecutive input code segments will be closer than a defined minimum number of code segments at the output of the shuffler. In exemplary embodiments of the present invention, by keeping data in, for example, manageable sub-sections, accurate SNR estimations, which are needed for the best possible LDPC decoding performance, can be facilitated based on, for example, iterative bit decisions.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006]FIG. 1 depicts an exemplary system according to an exemplary embodiment of the present invention;
[0007]FIG. 2 depicts an exemplary transmission frame format according to an exemplary embodiment of the present invention;
[0008]FIG. 3 depicts an exemplary S-Random Physical Frame shuffler according to an exemplary embodiment of the present invention;
[0009]FIG. 4 illustrates an exemplary channel interleaver structure according to an exemplary embodiment of the present invention;
[0010]FIG. 5 illustrates an exemplary dispersion of coded LDPC data according to an exemplary embodiment of the present invention;
[0011]FIG. 6 illustrates an exemplary dispersion of faded received data according to an exemplary embodiment of the present invention; and
[0012]FIG. 7 depicts plots of exemplary initial and final adaptive noise estimates according to an exemplary embodiment of the present invention.
[0013]It is noted that the patent or application file contains at least one drawing executed in color. Copies of this patent or patent application publication with color drawings will be provided by the U.S. Patent Office upon request and payment of the necessary fees.
DETAILED DESCRIPTION
[0014]It is well known that time interleaving a communication signal can be a very effective method for transforming a time fading channel into a memory-less channel. The amount of interleaving that needs to be performed is typically a function of the channel’s fading characteristics and system delay tolerance. In a broadcast channel, delay is generally not of major concern. In exemplary embodiments of the present invention this allows for the dedication of large amounts of hardware memory to interleave over as much time as possible.
[0015]FIG. 1 depicts an exemplary system for implementing a method of interleaving large LDPC code blocks over mobile channels according to an exemplary embodiment of the present invention. The method disclosed is independent of the specific details of a given LDPC encoder, and can be applied to any LDPC code block size and code rate. With reference to FIG. 1, on the transmit side 102 at the left of the figure, data 105 is input to LDPC encoder 110. From there it is sent to Random Shuffler 120, and from there to Convolutional Interleaver 130. From the output of Convolutional Interleaver 130 the data is transmitted over a communications channel to a receiver. At the receive side 142, essentially the inverse set of operations are performed. Thus, the received data is input to De-interleaver 140, then to De-shuffler 150, and from there to LDPC decoder 160, which outputs the decoded data 170.
[0016]In exemplary embodiments of the present invention a LDPC code can originate as a large block code (e.g., thousands of bits) using low coding rates. Again with reference to FIG. 1, in exemplary embodiments of the present invention an LDPC encoder 110 can be fed into a shuffler 120 that breaks the large code block into smaller subsections and randomly permutes these subsections within each code block. The random subsections can then, for example, be applied to a convolutional interleaver 130, with an entire subsection applied to each interleaving arm. A convolutional interleaver 130 is the preferred module or component for this task due its ability to achieve large spreading times with minimal memory usage.
[0017]FIG. 2 depicts an exemplary Transmission Frame Format according to an exemplary embodiment of the present invention. For purposes of illustration it will be assumed that there is a transmission frame 210 with 26 codewords (said codewords labeled as “CW” in FIG. 2). It is further assumed that each LDPC codeword 220 is composed of 49 code segments (each said code segment labeled “CS” in FIG. 2), where each code segment 230 has N bits. For an example where N=100 bits, there are thus 49 code segments (CSs) of 100 bits each making 4,900 bits per segment (CS), and 26 total code words (CWs) forming one transmission frame 210, thus comprising 26 CW*49 CS/CW*10 bits/CS=127,400 bits. It is understood that the systems and methods disclosed herein can equally apply to any LDPC code block size, any number of code blocks per transmission frame and any selected sub section size. In exemplary embodiments of the present invention, to achieve good time diversity the number of subsections can be on the order of 2% of the code block size, or less.
[0018]As shown in FIG. 1, after encoding, a first task, for example, is to randomize each subsection of a large LDPC code. This process is illustrated, for example, in FIG. 3, by use of, for example, a S-random block interleaver (shuffler). FIG. 3 depicts one of the code words (CWs) 220 of FIG. 2, which has 49 code segments (CSs), as shown therein. In FIG. 3 an exemplary code word is indexed as 310. FIG. 3 illustrates how these 49 code segments can be randomly shuffled, according to an exemplary embodiment of the present invention. The S-random shuffler can ensure that any two consecutive code segments (CSs) of a code word (CW) will be randomly permuted to have a defined minimum output time separation. For a code word CW divided into, for example, 49 code segments CS, an S-random shuffler can be designed to guarantee, for example, that no two consecutive input subsections will be closer than 4 subsections at the output of the shuffler. Such a process can be performed, for example, by first loading the entire code word 310 (i.e., all 49 subsections) into a buffer and then reading out each of the 49 code segments of code word 310 in a random order. In general an S-random shuffler can guarantee that given a code word with a total of X subsections or code segments (here 49) to be shuffled, no two consecutive input code segments will be closer than Y subsections, where X is the next integer greater than [sqrt(Y)]/2, here [sqrt(49)]/2=7/2=3.5, and thus X=4.
[0019]The readout order from the S-random shuffler can, for example, be controlled by a lookup table 320 (labeled “Permutation Table” in FIG. 3) and can, for example, be different for each code block (codeword) within a transmission frame (the terms “codeword” and “code block” are synonymous as used in this description, and will both be used herein). Moreover, in exemplary embodiments of the present invention, the table can repeat itself after every transmission frame 310. Thus, in the example depicted in FIG. 3, there are 26 permutation tables 320 that can be used, one for each code block (codeword CW) in a transmission frame. Codeblock CB Count 325 thus stores the number of which code block (of the available 26 in this example) is being operated upon, and inputs that value to Permutation Table 320.
[0020]Such S-random shuffling operation can, for example, ensure that random portions of each LDPC code are applied to the convolutional interleaver. This can, for example, minimize the possibility of consecutive data or parity bits being erased due to long fading. It is understood, of course, that this functionality depends upon the length of the fade condition. Thus, if a fade is longer than the convolutional interleaver’s time duration, then consecutive data and/or parity bits can be erased by the channel. The output 340 of the S-random shuffler is thus the code block 310 with its various code segments CS now in a very different, randomly permuted order. (It is noted that in FIG. 3 the code segments are labeled as “Physical Frames”, which refers to the same thing as CS in FIG. 2).
[0021]FIG. 4 depicts an exemplary interleaver according to an exemplary embodiment of the present invention. The depicted structure is a well known convolutional interleaver (CI). The CI’s arms move in sync with each other, so as to, for example, each process one whole S-random permuted segment of data, having, as noted, N bits. In the example described above, as noted, N=100. The interleaver can have, one branch for each segment of data in a codeword (here for example, 49 branches), that can be, for example, synchronized to the transmission frame boundary. Hence, the CI arms can perform, for example, exactly 26 revolutions per transmission frame, each lasting one codeword’s time duration per revolution.
[0022]In exemplary embodiments of the present invention each branch of a CI can, for example, be passed an entire code segment of data (100 bits), with each arm of the CI being of varying length. The effect of such a CI operation is to time disperse each of the code segments of data (as noted, in the depicted example of FIGS. 3-4, there are 49 such code segments, each having 100 bits). Naturally, the time dispersion achieved is a function of CI size, and is a system defined value, with a preferred minimum time dispersion on the order of, for example, 2.5 seconds or more.
[0023]FIG. 5 depicts how a single codeword can be randomly dispersed over, for example, a time duration of 2.5 seconds, after shuffling. Thus, consistent with the descriptive example used above, FIG. 5 depicts 49 codeword segments 510 of N bits each in various LDPC Codewords 520. The Codewords 520 are randomly shuffled, as described above, thus becoming Shuffled Codeword Segments 530. Then, after interleaving, the various Interleaved Codeword Segments codewords are spread out in time well beyond one transmission frame’s temporal duration (FIG. 2 indictaes a Transmission Frame 220 duration of 347 msec, and FIG. 5 indictaes that CW1 has been spread over 2.5 seconds, with code segments from CW2 interspersed between the various code segments of CW1.
[0024]Similarly, FIG. 6 is a depiction of an isolated signal fade of fairly long duration (typically, for example, greater than 75 milliseconds). The received data experiences the fade by contiguous data subsections being attenuated into the noise floor (erased). After de-interleaving according to exemplary embodiments of the present invention, the same faded subsections can be dispersed over a much longer time duration. FIG. 6 shows how an exemplary de-interleaver has dispersed a single isolated fade so that each LDPC code block never contains more than two (2) subsections affected by the fade, as is seen for CW4 and CW5, for example.
[0025]In exemplary embodiments of the present invention, a LDPC decoder requires knowledge of the received noise variance in order to properly form log likelihood ratios. Log likelihood ratios are, as known, a measure of how likely a soft decision for a given received symbol is. It can be understood as an indication as to how far away a given received symbol is from the x-y axis in an I,Q plot. In general, a slicer can make a hard decision or can give a log likelihood ratio as to the quadrant a particular received symbol is in.
[0026]As a received signal is de-interleaved, each segment of that signal will generally have a different noise variance. Thus, in exemplary embodiments of the present invention, a noise variance for each segment can, for example, first be estimated based on traditional noise variance cluster estimates. If the LDPC code contains N segments, then N independent noise variances can, for example, be estimated (one representing the average for each subsection of data samples). It is this metric that allows an LDPC decoder to essentially soft weight the merit of each segment for an iterative decoding process. To simplify the noise estimate, each segment can, for example, be aligned with a physical frame transmission, with one noise variance estimate for each physical frame. The initial noise estimate can, for example, be based on raw sliced decisions, averaging the squared distance of the received signal to the targeted hard decision symbol.
[0027]Unfortunately, under low SNR conditions, initial decisions can have large numbers of errors, leading to inaccurate noise estimates. This can be especially true in COFDM reception where the subsection of a signal that is decoded is based on an entire physical frame. This approach does not take into account the fact that some symbols within a COFDM physical frame are in deep nulls or the fact that the COFDM sliced errors are weighted by the channel state information. To improve on the noise variance estimate (which improves the LDPC decoding ability via correct soft weighting of the LDPC codes subsections), in exemplary embodiments of the present invention, the noise variance of each segment can be, for example, re-calculated on every iteration of the LDPC decoder. The idea behind re-calculating at each iteration is that the LDPC decoder comes closer and closer to estimating the correct bit decisions, hence providing a new target hard bit decision for the noise power estimate. After each iteration, the noise estimate improves and the weighting for each segment can correspondingly be subsequently improved. This function allows for improvement in the decoder, particularly under COFDM reception where the initial noise estimates can be highly incorrect, as noted.
[0028]In exemplary embodiments of the present invention, if data is interleaved in a manageable fashion, then adaptive estimation of the noise variance can be implemented. Thus, for example, the performance of an exemplary adaptive noise estimator for an exemplary COFDM received signal is shown in FIG. 7. The top curve shown in FIG. 7 (the blue trace in the color version) is an initial exemplary noise variance estimate into an LDPC decoder, and the bottom curve of FIG. 7 (the red trace in the color version) is the final estimate of the noise variance after sixty (60) LDPC iterations. In general, under noisy conditions, the initial noise variance estimate can be off by 2-3 dB. This inaccuracy can be caused by incorrect sliced bit decisions, which can mask the true noise variance. It is thus noted that the noise variance estimate for code segment number 46 (seen at the far right of FIG. 7) is initially optimistically off by more than 7 dB. The plot of FIG. 7 shows the benefit of adaptively estimating the noise variance, which can only be performed if the data is interleaved in a manageable fashion.
[0029]The inventive method of interleaving described above has been seen to be every effective in combating severe satellite fading channels. Additionally, such method provides a manageable procedure to accurately obtain noise variance estimates under fading conditions, from either a satellite channel, for example, or from a terrestrial channel.
[0030]While the present invention has been described with reference to certain exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope.
[0031]Therefore, it is understood that the invention not be limited to any particular embodiment, but that the invention will include all embodiments falling within the scope of the appended claims.
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