US Patent & Trademark Office
`
` US 6,240,073
` USPTO Transaction Information*
`
`SEQ.δ
`
`DATE
`
`DESCRIPTION
`
`1
`2
`3
`4
`5
`
`6
`7
`8
`9
`10
`11
`12
`13
`14
`15
`16
`17
`18
`19
`20
`21
`22
`23
`24
`25
`26
`27
`28
`29
`30
`31
`32
`
`Information Disclosure Statement (IDS) Filed
`15 Apr 1998
`08 May 2014 Mail-Petition Decision - Granted
`08 May 2014
`Petition Decision - Granted
`11 Mar 2014
`Petition Entered
`23 Oct 2012
`Correspondence Address Change
`Applicant Has Filed a Verified Statement of Small Entity Status in Compliance
`04 Oct 2004
`with 37 CFR 1.27
`25 Jan 2001 Workflow - File Sent to Contractor
`29 May 2001 Recordation of Patent Grant Mailed
`11 May 2001
`Issue Notification Mailed
`26 Apr 2001
`Application Is Considered Ready for Issue
`04 Apr 2001 Workflow - Drawings Received at Contractor
`04 Apr 2001
`Issue Fee Payment Verified
`04 Apr 2001 Workflow - Drawings Finished
`04 Apr 2001 Workflow - Drawings Matched with File at Contractor
`04 Apr 2001 Workflow - Drawings Sent to Contractor
`23 Apr 2001 Workflow - Complete WF Records for Drawings
`03 Jan 2001 Mail Notice of Allowance
`03 Jan 2001
`Notice of Allowance Data Verification Completed
`26 Dec 2000
`Date Forwarded to Examiner
`15 Dec 2000
`Response after Non-Final Action
`15 Dec 2000
`Request for Extension of Time - Granted
`06 Oct 2000
`Case Docketed to Examiner in GAU
`19 Jul 2000
`Mail Non-Final Rejection
`17 Jul 2000
`Non-Final Rejection
`09 Jun 1999
`Preexamination Location Change
`15 Apr 1998
`Information Disclosure Statement (IDS) Filed
`15 Apr 1998
`Information Disclosure Statement (IDS) Filed
`14 Nov 1997
`Preliminary Amendment
`30 Apr 1998
`Case Docketed to Examiner in GAU
`12 Mar 1998
`Application Dispatched from OIPE
`25 Feb 1998
`IFW Scan & PACR Auto Security Review
`05 Dec 1997
`Initial Exam Team nn
`
`*
`
`δ
`
` Document generated on 04/13/2015 by PATENTEC from official USPTO records, external to this file.
` Information deemed accurate, but not Certified.
` Transaction Sequence Number (SEQ.) is unrelated to Paper Number in File Table of contents.
`
` Page 1 of 1
`
`Quality Patent Documents
`
`TM
`
` 2001 Jefferson Davis Hwy, Arlington, VA 22202
` 1-703-418-2777 (cid:122) www.patentec.com (cid:122) info@ patentec.com
` © 2015 PATENTEC
`
`

`
` Patent Assignment Abstract of Title
`
`
`Total Assignments: 2
`Patent #: 6240073 Issue Dt: 05/29/2001
`Filing Dt: 11/14/1997
`Application #: 08970922
`Publication #: NONE
`Pub Dt:
`Intl Reg #:
`PCT #: NONE
`Inventors: ARIE REICHMAN, SHAUL LAUFER, AVI BARDA, SORIN GOLDENBERG
`Title: REVERSE LINK FOR A SATELLITE COMMUNICATION NETWORK
`
`
`
`Assignment: 1
`Reel/Frame: 009126
`/ 0684
`
`Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS).
`
`Assignors: REICHMAN, ARIE
`
`
`
`
`Exec Dt: 03/30/1998
`
`Received: 04/30/1998 Recorded: 04/20/1998 Mailed: 06/24/1998 Pages: 3
`
`LAUFER, SHAUL
`
`BARDA, AVI
`
`
`
`
`
`
`
`
`
`Exec Dt: 03/30/1998
`
`Exec Dt: 03/29/1998
`
`Exec Dt: 03/30/1998
`
`GOLDENBERG, SORIN
`
`
`
`
`Assignee: SHIRON SATELLITE COMMUNICATIONS (1996) LTD.
`14 KIRYAT SEFER STREET
`TEL AVIV, ISRAEL 65277
`
`
`Correspondent: DARBY & DARBY P.C.
`S. PETER LUDWIG
`805 THIRD AVENUE, 27TH FLOOR
`NEW YORK, NEW YORK 10022-7513
`
`
`
`
`Assignment: 2
`Reel/Frame: 024294
`/ 0787
`
`Conveyance: ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS).
`
`Assignor: SHIRON SATELLITE COMMUNICATIONS (1996) LTD.
`
`
`Assignee: ELBIT SYSTEMS LAND AND C4I - TADIRAN LTD.
`5 HAGAVISH STREET
`NATANIA, ISRAEL 42507
`
`Received: 04/28/2010 Recorded: 04/28/2010 Mailed: 04/28/2010 Pages: 2
`
`Exec Dt: 12/31/2009
`
`
`
`
`Correspondent: MARTIN D. MOYNIHAN
`P.O. BOX 16446
`PRTSI, INC.
`ARLINGTON, VA 22215
`
`
`
`
`
`
`
`

`
` US Patent & Trademark Office
`
` US 6,240,073
` Maintenance Fee Statement*
`
`Fee Description
`
`Amount
`
`Surcharge
`
`Small
`Entity
`
`Attorney
`Docket No.
`
`4th yr. Maintenance Fee
`
`455.00
`
`0.00
`
`SMALL
`
`0866/OD811
`
`8th yr. Maintenance Fee
`
`12th yr. Maintenance Fee
`
`1,180.00
`
`2,365.00
`
`0.00
`
`SMALL
`
`0866/OD811
`
`0.00
`
`SMALL
`
`0866/OD811
`
`1
`
`2
`
`3
`
`Status
`
`PAID
`
`PAID
`
`PAID
`
`*
`
` Document generated on 04/13/2015 by PATENTEC from official USPTO records, external to this file.
` Information deemed accurate, but not Certified.
`
` Page 1 of 1
`
`Quality Patent Documents
`
`TM
`
` 2001 Jefferson Davis Hwy, Arlington, VA 22202
` 1-703-418-2777 (cid:122) www.patentec.com (cid:122) info@ patentec.com
` © 2015 PATENTEC
`
`

`
`7
`
`L‘
`
`A
`
`EXAMINER
`
`.‘
`
`V PATEN DAT
`MAY 2, 9 mm
`
`’
`
`PATENT
`NUMBER
`
`UTILITY
`EWQER
`
`SN
`
`SERIAL NUMBER
`‘
`
`FILING DATE
`-
`
`‘
`
`APPLICANTS
`
`\
`
`-
`
`Foreign priority claimed
`35 USC 119 conditions met
`
`_
`
`/
`
`STATE nR SHEETS
`COUNTEY DRWGIS.
`
`CLAIMS
`
`Eli:-g\1E?VEE)E
`
`fl)
`0)
`LL!
`DZ
`
`DD<
`
`PARTS OF APPLICATION
`FILED SEPARATELY
`
`;
`
`A _
`
`ations
`
`BATCH
`NUMBER
`
`WARNING: The information disclosed herein may be restricted. Unéiuthorized disciosure may be prohibited
`by the United States Code Titie 35, Sections 122, 181 and 368. Possession outside the U.S.
`Patent & Trademark Office is restricted to authorized employees and contractors only.
`-
`
`Form PTO-436A
`
`(Rem 8/921
`
`Format f3rawinw{
`
`snag; gm
`
`(I=AcE)”]. A
`
`

`
`_
`
`V
`
`V PATENTV!iP§5L|CAT|GN*:» K’
`’ii|i|4i!|llllllllllllllillilH||l%|l|||lIl|
`Iii
`os97n922{
`
`Vi
`
`-APPRCXVED FOR LICENSE D
`lNlT}ALS
`%
`Egg 9 2 9 r5, Q; g
`
`-_j..._
`
`I
`
`Date
`
`_Received
`Mzfilrecg Cf‘;
`
`E"t:r"¢d
`Counted
`
`‘ ______ 1.
`__.__
`
`/ipplicati
`
`G)“ TKYIL K
`._.j_._.___ papers.
`
`EM
`
`,
`///I 4 I
`
`

`
`er.eH.w.S,..9
`.USEbyD.at8
`
`POSITION
`
`CLASSIFIER
`
`VERIFIER
`
`CORPS CORR.
`
`SPEC. HAND
`
`FILE MAINT.
`
`DRAFTING
`
`INDEX OF CLAIMS
`
`mC
`
`
`
`uuI
`
`.,umEmmW“mmmmn__m.mnmmmmmmmmmmm$mmmam......
`IIIIIIIIIIIIIIII
`ugamaaammmmmgmmmmmmmmmaamammmmnnmmgmwmnuIwwaw
`-m-2nununuum«munmmmmmmmmmmmmmmmmnmmmmmmmamunnI
`
`¢__.+NIA0
`
`mi:HH“H"
`
`dmwn
`teiea
`EdamWI
`..u..ne
`snap
`
`.0
`
`HNIA
`BOMB.
`
`I:3.m.__m__m_____.__m__._mfig”...
`23B27Egamaanamummyammamnmmmmaamamnmmmmmmmmm
`
`-EEIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIIII
`
`
`
`,.HwayI.Em
`
`..
`
`

`
`DEVHCDnAES
`
`néncam oursnoa
`
`

`
`
`
`
`
`I
`
`o
`
`there yo I %n"e*d’ate indicated above]
`deposltedithllsfpapifif-16,9with the U.s.PostaI service
`& that It waaadflresaed tordeuve
`£$ie31‘Bfi%5§¢’,Vt‘.‘.§l‘,”§’11au1 LAUFER, Avi BARDA, Sorin GOLDENBERG
`of Patents 8: Trademarks. Wham
`“Express Ma
`Oftlca to Adar as
`“ sen/Ice.
`, ¢°A< FIELD OF THE INVENTION
`
`Name (Print)
`
`signature
`
`The present
`
`invention relates generally to satellite communications and more
`
`particularly relates to a satellite based multiple access reverse communication link suitable for
`
`8.11 IIIICITICI EICCCSS I‘lCtWOI‘l{.
`
`BACKGROUND OF THE INVENTION
`
`Currently, communication systems around the world are growing rapidly due to the
`
`increasing need for data communication bandwidth.
`
`In particular, satellite communication
`
`systems are currently experiencing rapid growth due to growing customer demand for
`
`satellite based data communications. Most of the current demand and estimated future
`
`demand will be for Internet and other network based data communication applications. A
`
`major factor in these communication systems is the bandwidth capacity demanded by the
`
`user. Applications in widespread use today, such as video conferencing, LAN/WAN and
`
`document delivery require high speed forward and return link data capacities. Currently,
`
`however, these capabilities are not provided by present day Internet via satellite systems.
`
`It is currently estimated that there are approximately 13 million hosts and 16 million
`
`users on the Internet. The growth rate has been approximately 10 million new users a year
`
`for the past four years. At the same time, the number of Intranets (Internet network protocols
`
`applied within an enterprise or company for sharing information) are growing at an even
`
`faster rate. Currently, accessing the Internet via satellite has gained recognition as a fast and
`
`reliable solution for fast Internet access. Current commercially available Internet via satellite
`
`solutions such as DirecPC are based on an asymmetrical approach in which the data link to
`
`5 2
`
`0
`
`the user is via satellite while the return link to the user is via telephone lines using
`
`25
`
`commercially available telephony modems.
`
`The disadvantages of these asymmetrical
`
`systems is outlined below.
`
`The asymmetric approach via satellite,
`
`in which the user receives data from the
`
`Internet via satellite, yet sends data to the Internet via telephone lines, does not
`
`take
`
`advantage of a major feature of satellite pommunications: wide area coverage.
`
`The
`
`30
`
`asymmetric link is based on a terrestrial connection and therefore limits the ability of the fast
`
`P-1254-US
`
`l
`
`Q
`
`, Vy;ADnfllLJ<'/1jA41j\j4I’j%l4-"I .uw%mwmmmawu4wwmt’yammM;-. #»A
`
`.a......‘»a»asi-u»a»\»x;..m.»..mavm»-»«a..._.~ -«—-V » ~
`
`

`
`
`
`connection to the Internet to those places in which telephone lines and Internet service
`
`providers are available and have sufficient grade of service.
`
`The data rate of asymmetric Internet via satellite communication systems enables
`
`basically e-mail and browsing applications only.
`
`This structure is mainly targeted to
`
`consumer markets where the user is limited to sending data from their home at relatively low
`
`speeds. There are, however, many users such as small office/home office (SOHO) that desire
`
`high speed data communications in both directions yet cannot afford having dedicated lease
`
`lines for their Internet connection.
`
`In the United States alone there areapproximately 3.5
`
`million small businesses of which only 10% can justify an expensive leased line. Thus, there
`
`10
`
`are a large group of users looking for an on demand economical, fast and reliable connection
`
`to the Internet with a grade of service similar to that of a leased line.
`
`Typical applications that require high data rates in both directions include video
`
`conferencing, LAN/WAN systems,
`
`Internet
`
`applications, document delivery,
`
`audio
`
`applications such as Internet Phone, commercial web sites, net gaming, point of presence,
`
`15
`
`terminal equipment, Net Meeting and collaboration software. All
`
`the above mentioned
`
`applications are currently not adequately served by the currently available asymmetric
`
`satellite communication solutions.
`
`Spread spectrum communication systems have been used in a variety of fields for
`
`some time now.
`
`In spread spectrum communication systems,
`
`the bandwidth of the
`
`transmitted signal is much greater than the bandwidth of the information to be transmitted.
`
`The carrier signal in such systems is modulated by a function that serves to widen or spread
`
`the bandwidth of the signal for transmission. On the receive side, signal is remapped or
`
`decoded into the original information bandwidth to reproduce the desired output signal.
`
`Spread spectrum systems can be categorized into direct sequence systems, frequency
`
`25
`
`hopping systems, time hopping systems and hybrid systems which are combinations of the
`
`above three.
`
`In frequency hopping systems a carrier frequency is shifted or hopped in discrete
`
`increments in a pattern dictated by a predetermined code or sequence, e.g., a pseudo noise a
`
`sequence or code. The resulting consecutive and time sequential frequency pattern is called a
`
`30
`
`hopping pattern and the duration of each hop frequency is called a chip. The transmitted
`
`information is embedded in the codes or embedded within each frequency in the carrier wave
`
`
`
`by a modulation scheme such as PSK or FSK.
`
`P-1254-US
`
`3 .
`
`
`
`

`
`
`
`In reproducing the information signal of the receiver a synchronization acquisition
`
`process is performed in which the code pattern utilized by the receiver is synchronized with
`
`the code pattern generated and used in the transmitter. Using this, de-spreading and
`
`demodulation are performed on the spread spectrum signal to extract the transmitted data. A
`
`local reference signal is used that has a frequency corresponding to the same code pattern
`
`used in the transmitter for every chip. The received signal and the local reference are mixed
`
`in order to perform a correlation or de-spreading process for converting the spread spectrum
`
`signal
`
`into a signal having a frequency bandwidth wide enough to extract
`
`the data
`
`information. More information describing the operation of spread spectrum systems can be
`
`10
`
`found in “Spread Spectrum Systems,” by R.C. Dixon published by John Wiley and Sons,
`
`Inc., 1976.
`
`Multiple user systems use multiple access techniques to allow users to share resources
`
`such as time and frequency. When the traffic from each user in the network is approximately
`
`steady it is possible to divide a single high capacity multiple access channel into a plurality of
`
`15
`
`smaller orthogonal channels corresponding to individual user requirements. This can be
`
`accomplished either on a frequency basis using FDMA, on a time basis using TDMA or using
`
`CDMA.
`
`In addition, various combinations of FDMA and TDMA can also be used to
`
`minimize cost in large networks. FDMA and TDMA techniques are suitable solutions as
`
`long the traffic from each user is relatively stable. CDMA is a multiple access technique
`
`20
`
`which uses spread spectrum communications. CDMA communuications can be synchronous
`
`
`
`if all users are mutually synchronized in time.
`
`TDMA communication systems are also known for providing multiple access. Theses
`
`systems partition the channel time in a fixed predetermined manner. They are efficient when
`
`the user population includes only a relatively small number of users having high duty cycles.
`
`25
`
`However, many modern communication systems need to provide communication among
`
`interactive data tenninals which operate in low duty cycle burst modes. Thus, TDMA is not
`
`particularly suited to this kind of communication.
`
`In the typical modern interactive network, however,
`
`the traffic from individual
`
`x
`
`terminals in the system varies as a function of time due to random traffic demands by
`
`30
`
`different users at each terminal.
`
`In addition, the set of terminals active in the network can
`
`vary from moment to moment.
`
`In such systems it may be desirable to assign channel
`
`capacity to users on demand by means of a demand assigned multiple access (DAMA)
`
`f
`
`P-1254-US
`
`3
`
`

`
`
`
`architecture.
`
`In a DAMA system a separate channel called the request channel is used by
`
`individual users to request capacity as needed. The capacity can then be allocated in response
`
`to requests by a central master controller implemented by a common algorithm running in
`
`each terminal.
`
`A DAMA system however introduces additional overhead into the multiple access
`
`channel due to the process of requesting and assigning capacity.
`
`In addition, the demand
`
`assignment process introduces a delay which can degrade the performance under the channel.
`
`In some DAMA networks the total number of potential data terminals sharing the
`
`request charmel is much larger than the number of terminals active at any given point in time.
`
`10
`
`Thus, subdividing a DAMA request channel into smaller fixed allocation sub channels is
`
`15
`
`
`
`impractical. It is thus necessary to design a request channel architecture based upon a random
`
`access technique which allows for the possibility of a small subset of active transmitters
`
`selected from a much larger set of potential transmitters. Two random access techniques are
`
`currently available for such applications which include ALOHA multiple access and CDMA.
`
`The first data network to be based upon a random access protocol was ALOHANET
`
`which went into operation throughout the state of Hawaii in 1970. The ALOHA system was
`
`the first random access multi-point packet data communication system. The system uses a
`
`single radio channel shared by plurality of stations or data terminals. When a station
`
`generates a packet, the ALOHA system transmits the packet on the common radio channel.
`Since more than one station may attempt to transmit a packet at the same time several
`
`transmissions may overlap. The overlapping transmissions are said to collide if any portion
`
`of two transmissions overlap. When a collision occurs each station waits a random period of
`
`time before attempting to gain access to the channel again.
`
`To increase the utilization of the radio channel, the slotted ALOHA system was
`
`25
`
`proposed in which the channel is partitioned into time slots equal to a packet length wherein
`
`each station can only transmit a packet at the beginning of a slot.
`
`In this way overlapping
`
`transmissions are forced to completely overlap. Using a slotted approach almost doubles
`
`maximum channel utilization compared to the unslotted ALOHA system.
`
`To reduce the effects of collisions in the slotted ALOHA system a slot reservation
`
`30
`
`scheme was proposed. The channel was partitioned into frames each containing a reservation
`
`slot for transmitting a reservation packet and data slots for transmitting data packets. Each
`
`station transmits a reservation packet on a random access basis requesting slots needed for
`
`P-1254-US
`
`/‘
`
`4
`
`
`
`

`
`
`
`data packet transmission.
`
`If the request is granted data slots of a subsequent frame are
`
`assigned to the requesting station which subsequently transmits data packets on its assigned
`
`slots.
`
`Satellite communications can provide point
`
`to point channels or broadcast and
`
`multiple access channels. A satellite is well suited to provide one to many i.e., broadcast,
`
`channels and many to one, i.e., multiple access, channels from and to an earth station. The
`
`architecture of the network used in very small aperture terminal (VSAT) data networks is
`
`almost always designed around a single large hub earth station transmitting data in a
`
`broadcast channel to a large number of VSATs as shown in Figure 1. Considering Network
`
`10
`
`A, for example, the VSATs 20 in such a network transmit data in packets to the hub station
`
`18 using the multiple access capability of the satellite channel 17.
`
`The communications from the hub station of a VSAT network to the VSATs
`
`themselves is easily configured using a conventional communication technique such as TDM
`
`or FDM. Currently, TDM is widely used for multiplexing the hub to the VSAT terminals,
`
`notwithstanding the fact that there are differences in data rate, modulation techniques and
`
`transmission formats among the various VSAT networks.
`
`The multiple access link from the VSATs to the hub, however, is currently subjected
`
`to a greater degree of variation. The choice of multiple access technique from the VSATs to
`
`the hub is currently the primary feature distinguishing one network from another.
`
`20
`
`Recently, however, it has become commonplace to build VSAT networks composed
`
`of hundreds and thousands of more small VSAT terminals. The traffic in these networks is
`
`typically in the form of single data packets originating from interactive users or bursts of data
`
`packets originating from some type of file transcript protocol. As the number of stations in
`
`the network increases, the more the traffic from the single station will appear to fluctuate due
`
`25
`
`to random user demand. In such networks, the use of FDMA or TDMA becomes impractical
`
`while the use of DAMA would impose an unreasonable amount of overhead in the network.
`
`Thus, to provide multiple access to these types of packet data networks, the access techniques
`
`of direct sequence (DS) spread spectrum multiple access, i.e., DS-CDMA and ALOHA, are
`
`used. Both these multiple access techniques however suffer from disadvantages. Direct
`
`30
`
`sequence spread spectrum systems require the hub receiving station to have a digital matched
`
`filter operating at the high speed chip rate for each of the possible transmitters with each
`
`using a different spreading sequence.
`
`In a network with a large number of VSATs this
`
`
`
`P-1254-US
`
`5
`
`

`
`
`
`becomes unwieldy and expensive to maintain. ALOHA systems suffer from relatively low
`
`capacity and high average power requirements.
`
`
`
`P-1254-US
`
`~
`
`6
`
`
`
`

`
`
`
`SUMMARY OF THE INVENTION
`
`The present invention is a reverse link for a satellite communication system. The
`reverse link described herein is suitable for use in any type of communications network such
`
`as networks used for Internet access purposes. The reverse link in combination with a
`
`forward link forms a complete two way communication system via satellite. The reverse link
`
`comprises two separate communication schemes used in combination to implement the
`
`reverse link of the satellite system. The first communication scheme uses a random access
`
`method based on a non synchronous frequency hopping code division multiple access
`
`technique (NS/FH/CDMA). The second communication scheme uses a channel assignment
`
`10
`
`method based on a frequency division multiple access (FDMA) technique. Data generated by
`
`15
` 20
`
`a user is transmitted utilizing one of the two communication schemes in accordance with the
`
`content and amount of data generated. Messages requiring a relatively low transmission rate,
`
`such as short bursty messages, utilize the random access transmission method. On the other
`
`hand, messages requiring a higher transmission rate, such as video conferencing, utilize the
`
`charmel assignment method.
`
`There is therefore provided in accordance with the present invention a multiple access
`
`communications system for use in a satellite communication network, comprising a plurality
`
`of user
`
`terminals
`
`for generating data to be transmitted over
`
`the multiple access
`
`communication system, at
`
`least one hub for receiving data over the multiple access
`
`communication system from the plurality of user terminals, transmitter means within each
`
`user terminal for receiving data to be transmitted from the user terminal to the hub, the
`
`transmitter means including first communication means for transmitting short bursty data in
`
`combination with second communication means for continuous transmission of data,
`
`switching means coupled to the transmitter means for switching transmission between the
`first communication means and the second communication means in accordance with
`
`25
`
`predefined criteria and receiver means within the at least one hub adapted to receive data
`
`transmitted by the plurality of terminals utilizing either the first communication means or the
`
`second communication means.
`
`The first communication means can comprise non synchronous multiple access
`
`30
`
`communication means or non synchronous frequency hopping code division multiple access
`
`communication means. The second communication means can comprise frequency division
`
`multiple access communication means. The receiver means comprises means for receiving
`
`P-1254-US
`
`7
`
`
`
`

`
`
`
`data transmitted by the plurality of user terminals using the first communication means, the
`
`first communication means utilizing non synchronous frequency hopping code division
`
`multiple access communications, means for receiving data transmitted by the plurality of user
`
`terminals using the second communication means, the second communication means utilizing
`
`frequency division multiple access communications and means for receiving preamble and
`
`synchronization message data transmitted by the plurality of user terminals precedent to
`
`transmissions utilizing the first communication means.
`
`The switching means comprises means for switching transmission from the first
`
`communication means to the second communication means either in accordance with a
`
`l0
`
`source port field within messages received by the transmitter, when the length of a message
`
`
`
`received by the transmitter means exceeds a predetermined threshold, when a continuation
`
`flag in a message received by the transmitter means is turned on, when a user buffer
`
`containing a plurality of messages to be sent via the transmitter means fills beyond
`
`predetermined level or in accordance with the type and nature of the software application that
`
`initiated a message to be transmitted via the transmitter means.
`
`The switching means comprises means for switching transmission from the second
`
`communication means to the first communication means either when a source port matching
`
`a predetermined criteria ceases to transmit messages, when the length of a message received
`
`by the transmitter means fails to exceed a predetermined threshold, when a continuation flag
`
`in a message received by the transmitter means is turned off, when a user buffer containing a
`
`plurality of messages to be sent via the transmitter means empties or when the software
`
`application meeting a predetermined criteria that initiated a message to be transmitted via the
`
`transmitter means ceases to generate message data,
`
`In addition, the hub comprises collision detection means for determining when two
`
`25
`
`frequency hops associated with two independent receivers are utilizing the same frequency at
`
`the same time, thus improving decoding within the receiver means.
`
`There is also provided in accordance with the present invention a multiple access
`
`communication system for use in a satellite communication network,
`
`the satellite
`
`communication network including a plurality of user terminals and at least one hub, the
`system comprising first transmitter means for transmitting data utilizing a non synchronous
`
`30
`
`frequency hopping code division multiple access communication scheme, second transmitter
`
`means for transmitting data utilizing a frequency division multiple access communication
`
`P-1254-US
`
`8
`
`
`
`

`
`
`
`scheme, switching means for switching transmission between the first transmitter means and
`
`the second transmitter means in accordance with predefined criteria, first receiver means for
`
`receiving data transmitted using utilizing the non synchronous frequency hopping code
`
`division multiple access communication scheme, second receiver means for receiving data
`
`transmitted using the frequency division multiple access communication scheme and third
`
`receiver means for receiving preamble and synchronization data transmitted utilizing the
`
`utilizing a non synchronous frequency hopping code division multiple access communication
`
`scheme.
`
`The switching means comprises means for switching transmission from the first
`
`10
`
`transmitter means to the second transmitter means either in accordance with a source port
`
`field within messages received by the transmitter means, when the length of a message
`
`received by the transmitter means exceeds a predetermined threshold, when a continuation
`flag in a message received by the transmitter means is turned on, when a user buffer
`
`containing a plurality of messages to be sent via the transmitter means fills beyond
`
`predetermined level or in accordance with the type and nature of the software application that
`
`initiated a message to be transmitted via the transmitter means.
`
`The switching means comprises means for switching transmission from the second
`
`transmitter means to the first transmitter means either when a source port matching a
`
`predetermined criteria ceases to transmit messages, when the length of a message received by
`
`the transmitter means fails to exceed a predetermined threshold, when a continuation flag in a
`
`message received by the transmitter means is turned off, when a user buffer containing a
`
`plurality of messages to be sent via the. transmitter means empties or when the software
`
`application meeting a predetennined criteria that initiated a message to be transmitted via the
`
`transmitter means ceases to generate message data.
`
`
`
`25
`
`The system fllI'thCI' comprises interface means for interfacing the at least one hub to an
`
`external communications network. The external communications network can comprise the
`
`Internet, a packet switched telephone network (PSTN), an Integrated Services Digital
`
`Network (ISDN), a Community Antenna Television (CATV) network, a Digital Subscriber
`
`Loop (XDSL) or a Frame Relay network.
`
`30
`
`The system further comprises collision detection means for determining when two
`
`frequency hops associated with two independent receivers within the receiver means are
`
`P-1254-US
`
`9
`
`
`
`

`
`
`
`utilizing the same frequency at the same time, thus improving decoding within the first
`
`receiver means.
`
`There is also provided in accordance with the present invention a multiple access
`
`communications system for use in a satellite communication network, comprising a plurality
`
`of user terminals for transmitting and receiving data over the multiple access communication
`
`system, at
`
`least one hub for transmitting and receiving data over the multiple access
`
`communication system to and from the plurality of user terminals, a forward communication
`
`link for transmitting data from the at least one hub to the plurality of user terminals, a return
`
`communication link for transmitting data from the plurality of user terminals to the at least
`
`10
`
`one hub,
`
`the return communication link including a first communication means for
`
`transmitting short bursty data in combination with second communication means for
`
`continuous transmission of data, switching means within the plurality of user terminals for
`
`switching transmission between the
`
`first
`
`communication means
`
`and the
`
`second
`
`communication means in accordance with predefined criteria and receiver means within the at
`
`least one hub adapted to receive data transmitted by the plurality of terminals utilizing either
`
`the first communication means or the second communication means.
`
`Further, each user terminal comprises means for generating a request to be sent over
`
`the return communications link in order to utilize the second communication means. The hub
`
`comprises means for polling each user terminal over the forward communication link as to
`
`whether the transmission of data should be switched to utilize the second communication
`
`
`
`
`
`means .
`
`P-1254-US
`
`10
`
`
`
`

`
`
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`The invention is herein described, by way of example only, with reference to the
`
`accompanying dr wings, wherein:
`
`Fig. lzahigh level block diagram illustrating two satellite communication networks
`
`coupled to the I ternet utilizing both a forward and a reverse link via satellite;
`
`a graph illustrating the relationship between time and frequency for data
`
`Fig.
`
`packets trans
`
`itted by two users;
`
`Fig. Z5 a diagram illustrating sequence of packets transmitted in time making up a
`message;
`/
`Fig. 4,;//is a diagram illustrating a frequency band making up the frequency spectrum of
`
`the communica ion system;
`
`a high level block diagram illustrating the random access transmitter of the
`Fig.
`communicati‘r;;{system ofthe present invention;
`
`Fig. ,
`
`is a high level block diagram illustrating the channel assignment transmitter of
`
`the communicat'6n system;
`
`Fig.
`
`a high level block diagram illustrating the software layers making up the
`
`personal compu er based transmitter method portion of the communication system;
`
`a high level flow diagram illustrating the driver method of the present
`Fig.
`I
`“
`I
`invention;
`Fig. ;/is a high level block diagram illustrating the random access transmitting
`
`method of the present invention;
`Fig.
`lrflfis a high level block diagram illustrating the hub receiver portion of the
`
`communication system;
`Fig. 1 a high level block diagram illustrating the random access receiver of the
`
`communication fgystem of the present invention;
`Fig. 12/is a high level block diagram illustrating the channel assignment receiver of
`
`the communica ion system;
`
`Fig. 1&5 a high level flow diagram illustrating the synchronization receiver method
`
`of the present i /vention; and
`
`Fig.
`
`a high level flow diagram illustrating the random access receiver portion of
`
`10
`
`15
`20
`
`25
`
`30
`
`the communication system of the present invention.
`
`P-1254-US
`
`
`
`

`
`
`
`
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`0 The following notation is used throughout this document.
`
`Notation Used Throughout
`
`Term
`
`CA
`CATV
`CDMA
`DAMA
`DPSK
`DQPSK
`DSL
`DTH
`
`DVB
`FDM
`FDMA
`FH
`FSK
`IP
`
`ISDN
`ISP
`
`LAN
`
`NS
`PLL
`PSK
`QPSK
`RA
`
`RC
`SOHO
`
`TCP
`
`Definition
`
`Channel Assignment
`Community Antenna Television
`Code Division Multiple Access
`Demand Assigned Multiple Access
`Differential Phase Shift Keying
`Differential Quadrature Phase Shift Keying
`Digital Subscriber Loop
`Direct-To-Home
`
`Digital Video Broadcasting
`Frequency Division Multiplexing
`Frequency Division Multiple Access
`Frequency Hoping
`Frequency Shift Keying
`Internet Protocol
`
`Integrated Services Digital Network
`Internet Service Provider
`
`Local Area Network
`
`Non Synchronous
`Phase Lock Loop
`Phase Shift Keying
`Quadrature Phase Shift Keying
`Random Access
`
`Raised Cosine
`Small Office Home Office
`
`Transmission Control Protocol
`
`
`
`_
`
`I
`
`O
`
`Time Division Multiplexing
`TDM
`Time Division Multiple Access
`TDMA
`User Datagram Protocol
`UDP
`VSAT
`Very Small Aperture Terminal
`
`WAN
`Wide Area Network
`
`T
`
`5
`
`~
`
`General Description
`
`The present invention is a reverse link for a satellite communication system. The
`
`reverse link described herein is suitable for use in any type of communications network such
`
`as networks used for Internet access purposes. The reverse link in combination with a
`
`forward link fo