Patent Publication Number: US-2011058515-A1

Title: Data and telephony satellite network with multiple paths

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to satellite communication systems and methods and more specifically to satellite communication systems and methods for transferring data between local and remote users. 
     Satellite communication systems have become indispensable, and now find use in marine and automobile navigation, telephonic communication, television data distribution and the like. In telephonic communication, satellite systems can communicate with remote regions that are inaccessible to cellular towers, and can assist in emergencies such as natural disasters where other terrestrial telephonic systems have been disrupted. 
     A typical satellite consists of a constellation of satellites orbiting around the earth. Iridium, for example, consists of a constellation of 66 satellites rotating around the earth&#39;s orbit. Another well know satellite system is Globalstar. 
     One limitation of existing satellite telephonic systems is that it is cost prohibitive to place or receive satellite telephonic calls. In part, this cost prohibitive nature can be attributed to the high cost of deploying these communication satellites into orbit. The high cost can also be attributed to bandwidth utilization inefficiencies. Each satellite telephonic call uses a dedicated channel. This dedicated channel cannot be used by other users even when voice information is not being communicated, resulting in bandwidth inefficiencies that can increase overall costs. 
     A further limitation of existing satellite telephonic systems is that physical obstacles (mountains, buildings, etc.) can prevent signals from reaching their intended recipients. Users frequently experience dropped calls and other data losses since line-of-site access to satellites is usually required for continuous communication between such users. 
     Thus, there is a need to address one or more of the aforementioned problems and the present invention meets this need. 
     BRIEF SUMMARY OF THE INVENTION 
     Various aspects of a satellite communication network for communicating data packets during telephone communication between a local user handset and a remote user handset can be found in the present invention. 
     In one aspect, the satellite communication network includes the local user handset in communication with a first satellite referred to as the primary Low Earth Orbit (LEO) Satellite. This primary LEO satellite is configured to receive data packets from the local user handset. Here, the data packets can be the user&#39;s analog voice signal that is packetized and formatted for transmission during telephonic conversation. 
     Data packets might also include audio, video, text and the like. Upon receiving the data packets, the primary LEO satellite concurrently transmits the data packets in their entirety through each of a plurality of communication paths between the primary LEO satellite and the remote handset. By using a plurality of communication paths for data transmission, the present invention provides path diversity and redundancy so as to avoid dropped telephonic calls and data losses associated with conventional satellite systems. 
     The plurality of communication paths includes a first path from the primary LEO satellite through a second LEO satellite to the remote handset. A second communication path also extends from the primary LEO satellite through the second LEO satellite as well as a second Geostationary Earth Orbit (GEO) satellite to the remote user handset. Further yet, a third communication path extends also from the primary LEO satellite via a first GEO satellite through the second GEO satellite to the remote handset. Further yet, a fourth communication link extends also from the primary LEO satellite via the Internet through the second GEO satellite to the remote user handset. 
     Therefore, the present invention permits the entirety of all of the data packets to be streamed through each of a plurality of communication paths. Not only does this provide redundancy and path diversity in the event of data loss, it also allows for increased throughput for bandwidth intensive data. Moreover, because data packets are not streamed through dedicated channels, the overall cost of using the present invention for satellite telephonic communication is reduced. 
     A further understanding of the nature and advantages of the present invention herein may be realized by reference to the remaining portions of the specification and the attached drawings. Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, the same reference numbers indicate identical or functionally similar elements. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a satellite network according to an exemplary embodiment of the present invention. 
         FIG. 2  is a block diagram illustrating components of a local user handset in accordance with an exemplary embodiment of the present invention. 
         FIGS. 3A &amp; 3B  illustrate a communication method according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the embodiments of the invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with the preferred embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, numerous specific details are set forth in order to provide a thorough understanding. However, it will be obvious to one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well known aspects have not been described in detail as not to obscure aspects of the present invention. 
       FIG. 1  shows satellite network  100  according to an exemplary embodiment of the present invention. 
     In  FIG. 1 , local user handset  106  can utilize satellite network  100  to establish telephone communication with remote user handset  112  located in separate geographic location. Local user handset  106  might be in San Francisco while remote user handset  112  is located in Moscow, for example. Both user handsets, however, might be in the same geographic location and need not be in separate geographic locations. 
     Note that as used herein both local user handset  106  and remote user handset  112  are stand alone wireless communication devices. Once telephonic communication is established between the user handsets, data packets can be streamed and exchanged between both user handsets via satellite network  100 . Among other advantages, the present invention permits all information including voice, images video, audio, textual and the like to be streamed as data packets. 
     In  FIG. 1 , satellite network  100  comprises primary Low Earth Orbit (LEO) satellite  108 . Primary LEO satellite  108  is configured to receive data packets from local user handset  106 , and is configured to concurrently communicate said data packets via a plurality of communication paths A, B, C, D and E to remote user handset  112 . As implied by its name, primary LEO satellite  108  is part of a constellation of low earth orbiting satellites, with an orbit range of about 500 miles above the earth&#39;s surface. 
     Preferably, every position on the earth&#39;s surface is locatable by any one or more of the LEO satellites. Primary LEO satellite  108  has multiple spot beams for transmitting and receiving, and each spot beam covers a predetermined geographic region. Local user handset  106  can be found within one such spot beam and is able to communicate with primary LEO satellite  108  via an appropriate frequency band (e.g. C band) within the spot beam. 
     Primary LEO satellite  108  is itself communicably linked to secondary LEO satellite  110  along communication paths A and B. Secondary LEO satellite  110  is also a low earth orbiting satellite orbiting at about 500 miles above the earth&#39;s surface. Secondary LEO satellite  110  is the closest LEO satellite to remote user handset  112  and is thus configured to deliver data packets received from primary LEO satellite  108  to remote user handset  112  along communication path A as shown. Although not shown, both LEO satellites have a switching means for establishing intersatellite link (communication path A) between primary LEO satellites  106  and secondary LEO satellite  110 . 
     Secondary LEO satellite  110  is also configured to communicate data packets from primary LEO satellite  108  to gateway  118  along communication path B as shown. Gateway  118  comprises a hub and applicable computer software and hardware for receiving and translating data packets between applicable protocols as well as routing the data packets. As shown, gateway  118  which also includes a transmitter is communicably coupled to secondary Geosynchronous Earth Orbiting (GEO) satellite  104  also along communication paths B and D. 
     Secondary GEO satellite  104  is part of a constellation of satellites orbiting the earth at about 22,000 miles above the earth&#39;s surface. Secondary GEO satellite  104  is configured to forward data packets received from gateway  118 &#39;s transmitter to the intended recipient namely remote user handset  112  along communication path B. Typically, secondary GEO satellite  104  is the closest GEO satellite to remote user handset  112 . Preferably, secondary GEO satellite  104  is compliant with the standards set forth in DVB-S, developed by ETSI (European Telecommunications Standards Institute). 
     Many conventional satellite communications systems are being made compliant with DVB-S. Although originally intended for digital satellite broadcasting, the DVB-S standard is increasingly being utilized for IP (Internet Protocol) and TCP/IP more specifically. The DVB-S standard employs MPEG-2 (Motion Pictures Expert Group), which is another digital standard. MPEG-2 allows digital data carried by DVB-S communication systems to be compressed and packetized. Use of DVB-S thus allows for easy transfer of signals between mediums that would otherwise be incompatible. If signals can be digitized, DVB-S is capable of delivering such signals. 
     To transfer information, data packets or datagrams are placed within the payload sections of one or more MPEG-2 packets after which the MPEG-2 packets are transported using DVB-S. The portion of DVB-S that allows such packetization using a DVB carrier is referred to as MPE (Multi Protocol Encapsulation). MPE can be employed for transmitting IP packets for satellite-based communications as well as Voice Over IP communications. 
     Referring now to  FIG. 1 , primary LEO satellite  108  is also communicably linked to gateway  114  along communication paths C and D. Gateway  114  comprises a hub and applicable computer software and hardware for receiving and translating said data packets between applicable protocols as well as routing the data packets. As shown, gateway  114  is capable of routing data packets received from primary LEO satellite  108  along communication path D. The data packets are routed thorough Internet  116 , gateway  118 , secondary GEO satellite  104  to the intended recipient remote user  112 . 
     Referring now to  FIG. 1 , primary LEO satellite  108  is also communicably linked to primary GEO satellite  102  along communication path E. Primary GEO satellite  102  is a part of the satellite constellation that includes secondary GEO satellite  104 . Primary GEO satellite  102  is configured to receive data from LEO  108  and deliver said data packets to secondary GEO satellite  104  that is closest to the intended recipient remote wireless handset user  112  along communication path C. 
     Gateway  114  is capable of translating received data packets into IP format for transmission via Internet  116 . Gateway  114  is also communicably coupled to primary GEO satellite  102  along communication path C. Primary GEO satellite  102  is part of the satellite constellation that includes secondary GEO satellite  104 . Primary GEO satellite  102  is configured to receive data packets from gateway  114  and to deliver said data packets to secondary GEO satellite  104  that is closest to the intended recipient remote user handset  112  along communication path C. 
     In use, to establish telephone communication, local user handset  106  uses the handset keypad (not shown) to initiate a telephone call with user  112 . Once the telephone call is setup, data packets are streamed from local user handset  106  to primary LEO satellite  108 . In turn, primary LEO satellite  108  streams the entirety of all of the data packets through each one of the plurality of communication paths A, B, C, D and E as more fully described with reference to  FIG. 3 . 
     Once all of the data packets are received by remote user handset  112 , duplicate data packets are identified and discarded as appropriate. Another advantage of the present invention is that the entirety of all of the data packets is streamed through each of a plurality of communication paths A, B, C, D and E. Not only does this provide redundancy and path diversity in the event of data loss, it allows for increased throughput for bandwidth intensive data. 
     Although not shown, other type communication links might be utilized as well. The indicated communication paths shown in  FIG. 1  are not intended to limit the applicability of the present invention. Further, although not shown, the return communication path from remote user handset  112  to local user handset  106  is the reverse of the communication links indicated in  FIG. 1 . For example, data packets from remote user handset  112  might be streamed to secondary LEO satellite  110 , which becomes the primary LEO satellite from which all of the data packets from remote user handset  112  are streamed through the various multiple paths to local user handset  106 . 
       FIG. 2  is a block diagram illustrating components of local user handset  106  in accordance with an exemplary embodiment of the present invention. 
     In  FIG. 2 , local user handset  106  comprises ADC (Analog to Digital Converter)  202 . ADC  202  performs a sample and hold operation preferably by sampling the user&#39;s voice signal at a rate of 64 kbps, and then thereafter performing quantization as well. The bit stream output from ADC  202  is passed to speech encoder  204  to produce digitally encoded speech that is then forwarded to packetizer  206 . Packetizer  206  packetizes the voice signals into data packets having headers to which source and destination addresses are added. In addition to voice, audio, video, text and the like can all be packetized into a single composite data channel. 
     Error detection information is added by FEC (Forward Error Correction) circuitry  208 . Thereafter, a multi-access protocol  209  scheme is applied to the data packets to efficiently allocate bandwith resources of primary LEO satellite  108  to which the data packets are sent. Any multi-access protocol such as FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access), etc. consistent with the spirit and scope of the present invention can be utilized. 
     Preferably, TCDMA (Time Code Division Multiple Access) is employed by the present invention. After the appropriate access protocol is applied, the data packets are transmitted by transmitter  210  in conjuction with framing and bit timing circuitry  213  and antenna  212 . Here, as shown, processor  215  coordinates and controls the various handset component operations. 
     Similarly, data packets can be received by local user handset  106 . The data packets from a LEO or GEO satellite are received by antenna  214  communicably coupled to receiver  216 . After processing, receiver  216  passes the data packets to address decoder  218 , which extracts identifier data in conjunction with processor  215  and framing and bit timing  213 , and then forwards the data packets for error detection by error detection  219 . 
     Header decoder  222  examines all of the data packet headers for decoding, and thereafter signalling packets are sent to processor  215  while data packets with the voice payload are resequenced and forwarded to speech decoder  226  for decoding. The digital data packets are then converted to analog voice signals by DAC  228  so that the voice signals can be perceived by the user. 
     Although not shown, processor  215  may be a dual processor. In this case, one processor (and associated components such as dual transmitters and receivers, not shown) is dedicated to processing LEO packets while the other processor is dedicated to processing GEO packets. In this manner, each one of the dual processors can independently process GEO or LEO packets thus achieving both download and upload speeds not attainable by conventional communication systems. 
       FIGS. 3A and 3B  illustrate communication method  300  according to an exemplary embodiment of the present invention. 
     In  FIGS. 3A and 3B , communication method  300  is preferably used by satellite network  100  of  FIG. 1  to communicate data packets between local user handset  106  and remote user handset  112 . 
     At block  302  of  FIG. 3A , local user handset  106  sends a request for telephonic communication with remote user handset  112  to primary LEO satellite  106 . Primary LEO satellite uses an established signalling scheme (known to both handsets) to signal remote user handset  112 . 
     At block  304 , once the telephone call is established, local user handset  106  packetizes speech data for transmission to primary LEO satellite  108 . Other types of data namely audio, video, text, etc. can be packetized as well. 
     At block  306 , the data packets from local user handset  106  are received by primary LEO satellite  108 . Preferably, the data packets are packetized using a format compatible with primary LEO satellite  108 , primary GEO satellite  102  and Internet  116 . The data packets may be packetized according to DVB-S standards, for example, as discussed with reference to  FIG. 1 . The data packets can also be encapsulated in a format compatible with primary LEO  108  (and LEO satellite  110 ). In that case, translations into protocol formats appropriate for the next hop is performed by gateways  114  and  118 . 
     At block  308 , primary LEO satellite  108  uses the appropriate transponders to transmit the data packets in their entirety to LEO satellite  110  via communication paths A and B of  FIG. 1 . Contemporaneously, the same data packets are also transmitted to gateway  114  (communication paths C and D) and the same data packets are also transmitted to GEO satellite  102  via path E. 
     At block  310 C, gateway  114  sends the data packets to primary GEO satellite  102 . Although not shown, gateway  114  includes a routine for ensuring that data packets received are compatible with primary GEO satellite  102 . If the data packets are incompatible as received, the routine in conjunction with appropriate hardware translates the data packets to a compatible format. For example, if primary GEO satellite  102  is DVB-S compatible, the routine translates incompatible data packets to DVB-S format before the data packets are transmitted to primary GEO satellite  102 . 
     At block  312 C of  FIG. 3B , primary GEO satellite  102  transmits the data packets to secondary GEO satellite  104 . 
     At block  314 C, secondary GEO satellite  104  then forwards the data packets to the intended recipient namely remote user handset  112 . Depending on when data packets routed through other communication paths arrive, the data packets from secondary GEO satellite  104  are either received for processing or are discarded as duplicate packets. 
     Returning to block  310 D of  FIG. 3A , having received the data packets from primary LEO satellite  108 , gateway  114  transmits said data packets via Internet  114  to gateway  118 . 
     At block  312 D of  FIG. 3B , gateway  118  sends the data packets to secondary GEO satellite  104 . 
     At block  314 D, secondary GEO satellite  104  then transmits the data packets to remote user handset  112 . Depending on when data packets routed through other communication paths arrive, the data packets from secondary GEO satellite  104  can be either received for processing or are discarded as duplicate packets. 
     Returning to block  310 B of  FIG. 3A , having received the data packets from primary LEO satellite  108 , secondary LEO satellite  110  transmits the data packets to gateway  118 . 
     At block  312 B of  FIG. 3B , gateway  118  transmits the data packets to secondary GEO satellite  104 . 
     At block  314 B, secondary GEO satellite  104  then transmits the data packets to remote user handset  112 . Depending on when data packets routed through other communication paths arrive, the data packets from secondary GEO satellite  104  can be either received for processing or are discarded as duplicate packets. 
     Returning to block  310 A of  FIG. 3A , having received the data packets from primary LEO satellite  108 , secondary LEO satellite  110  transmits the data packets to the remote user handset  112 . Depending on when data packets routed through other communication paths arrive, the data packets from secondary LEO satellite  110  can be either received for processing or are discarded as duplicate packets. 
     Returning to block  310 E of  FIG. 3A , having received the data packets from primary LEO satellite  108 , primary GEO satellite  102  transmits the data packets to the secondary GEO satellite  104 . 
     At block  312 E of  FIG. 3B , secondary GEO satellite  104  then transmits the data packets to remote user handset  112 . Depending on when data packets routed through other communication paths arrive, the data packets from secondary GEO satellite  104  can be either received for processing or may be discarded as duplicate packets. 
     In this manner, the present invention streams the entirety of all of the data packets through each of a plurality of communication paths A, B, C, D &amp; E. Not only does this provide redundancy and path diversity in the event of data loss, it allows increased throughput for bandwidth intensive data. 
     While the above is a complete description of exemplary specific embodiments of the invention, additional embodiments are also possible. Thus, the above description should not be taken as limiting the scope of the invention, which is defined by the appended claims along with their full scope of equivalents.