Patent Description:
In a Time Division Multiple Access (TDMA) network multiple transmitters may share a transmission channel by dividing access to the channel into discrete time slots. Once a transmitter has accessed the network, for example, through a Random Access Channel (RACH), a dynamic bandwidth scheduler may provide a transmitter with bandwidth allocations on the shared channel, which allocations are non-overlapping in time for the shared channel.

In addition to TDMA, satellite communication systems assign a first frequency to legacy terminals and a different second frequency to new terminals because the types of decoders available in the new and legacy air interfaces are disjoint. The legacy air interface uses Turbo code, while the next generation air interface supports Turbo and new LDPC code rates. Legacy terminals are not equipped with the new LDPC decoder. The different frequency assignments reduce overall system capacity, in particular, when the traffic load for each carrier is low. For example, when the time utilization of the carrier by the legacy terminal is <NUM>% and the new terminal is <NUM>%, the system still uses two carriers and the overall utilization per carrier is <NUM>%. However, if the next generation air interface is designed such that legacy terminals can operate on the same carrier as the new terminals, the utilization becomes <NUM>% in the above example, which is twice the utilization achieved with two separate dedicated carriers. The legacy air interface mentioned in the example includes GMR-<NUM><NUM> (uses the Turbo code) and GMR-<NUM><NUM> (also known as GMPRS-<NUM>; uses slow LDPC code rates). The next generation air interface includes new LDPC code rates that the legacy GMR-<NUM><NUM> terminals do not support. The present teachings are applicable to both legacy <NUM> and <NUM> terminals.

<CIT> discloses a system in which packets are received at IP layer. The destination address is checked and then it is determined whether the packet should be transmitted on LTE in licensed spectrum or WiFi in unlicensed spectrum based on the destination address.

<CIT> discloses a system in which the base station receives different radio access bearers or different flows and based on the use of bearer/ flow filter, transmit the different bearers or flows to LTE or to WiFi.

<NPL>) discloses the coexistence of LTE and WIFI using the same unlicensed band.

The present teachings enable a use of the same carrier by both legacy and new terminals, improving the system utilization (or throughput) significantly.

This Summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description.

A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. Independent claim <NUM> defines a method according to the claimed invention for communicating with a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface. The method includes assigning a same carrier to the legacy terminal and the new terminal; receiving a terminal identifier and an optional payload for transmission at a MAC/RLC (media access layer/radio link control) layer; determining if the terminal identifier is associated with the legacy terminal or the new terminal; composing, based on the determining, a burst header; formatting, a burst including the burst header and the optional payload; and transmitting the burst. In the method, the legacy air interface defines one or more valid burst headers and one or more undefined burst headers, the burst header is set to one of the one or more valid burst headers when the burst is associated with the legacy terminal, and the burst header is set to one of the one or more undefined burst headers when the burst is associated with the new terminal. At least one of the one or more undefined burst headers identifies an MCS unsupported by the legacy air interface. Other embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods.

Implementations may include one or more of the following features. The method where the next generation air interface supports a MCS (modulation and coding scheme) unsupported by the legacy air interface. The method where the next generation air interface supports a ULMAP (uplink map). The method where at least of the one or more undefined burst headers identifies an MCS unsupported by the legacy air interface. The method where the transmitting of a portion of the burst is in a portion of the same carrier. The method where the same carrier may include a 5x carrier, and the transmitting for the next generation air interface transmits a portion of the burst in a 1x carrier, a 2x carrier or the 5x carrier. The method where the transmitting for the legacy air interface transmits the burst in the 5x carrier. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium.

Independent claim <NUM> defines a system according to the claimed invention to communicate with a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface. The system includes a gateway to assign a same carrier to the legacy terminal and the new terminal; a MAC/RLC (media access layer/radio link control) layer to receive a terminal identifier and an optional payload for transmission, to determine if the terminal identifier is associated with the legacy terminal or the new terminal, and to compose, based on the determining, a burst header; a burst formatter to format a burst may include the burst header and the optional payload, and a transmitter to transmit the burst. In the system, the legacy air interface defines one or more valid burst headers and one or more undefined burst headers, the burst header is set to one of the one or more valid burst headers when the burst is associated with the legacy terminal, and the burst header is set to one of the one or more undefined burst headers when the burst is associated with the new terminal. At least one of the one or more undefined burst headers identifies an MCS unsupported by the legacy air interface.

One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions.

Additional features will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of what is described.

In order to describe the manner in which the above-recited and other advantages and features may be obtained, a more particular description is provided below and will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understanding that these drawings depict only typical embodiments and are not, therefore, to be limiting of its scope, implementations will be described and explained with additional specificity and detail with the accompanying drawings.

The present teachings may be a system, a method, and/or a computer program product at any possible technical detail level of integration.

Computer readable program instructions for carrying out operations of the present invention may be assembler instructions, instruction-set-architecture (ISA) instructions, machine instructions, machine dependent instructions, microcode, firmware instructions, state-setting data, or either source code or object code written in any combination of one or more programming languages, including an object oriented programming language such as SMALLTALK, C++ or the like, and conventional procedural programming languages, such as the "C" programming language or similar programming languages.

Reference in the specification to "one embodiment" or "an embodiment" of the present invention, as well as other variations thereof, means that a feature, structure, characteristic, and so forth described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment", as well any other variations, appearing in various places throughout the specification are not necessarily all referring to the same embodiment.

<FIG> illustrates a satellite communication system according to various embodiments.

<FIG> illustrates a satellite communication system <NUM> including a radio gateway <NUM>, a satellite <NUM>, a legacy terminal <NUM>, a new terminal <NUM>, a gateway <NUM> connected to an external IP network <NUM> such as the Internet. An uplink <NUM> may refer to a radio link transmitting from the legacy terminal <NUM> and the new terminal <NUM>, and received by the satellite <NUM>. A downlink <NUM> may refer to a radio link transmitting from the satellite <NUM> and received by the legacy terminal <NUM> and the new terminal <NUM>. The uplink <NUM> may be a TDMA channel or radio path. The downlink <NUM> maybe a TDMA channel. The gateway <NUM> may include or may communicate with a transceiver (not shown). The legacy terminal <NUM> may include or may communicate with a transceiver (not shown). The new terminal <NUM> may include or may communicate with a transceiver (not shown).

<FIG> illustrates a burst and its relation to network layers according to various embodiments.

A satellite network <NUM> may function using higher layers <NUM>, a MAC/RLC (Media Access Layer/Radio Link Control) layer <NUM> and a PHY (physical) layer <NUM>. An output of the PHY layer <NUM> may be error coded with a FEC (Forward Error Control) coder <NUM>, burst formatted with a burst formatter <NUM> and modulated with a modulator <NUM> prior to transmission. The satellite network <NUM> may assign a same carrier to a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface. In some embodiments, the new terminal may support both the legacy air interface and the next generation air interface.

A MAC/RLC structure <NUM> may be provided by the higher layers to the MAC/RLC layer <NUM>. The MAC/RLC structure <NUM> may include, among others, a terminal identifier <NUM> and a payload (PRI (private information)) <NUM>. In some embodiments, the terminal identifier <NUM> may be a MAC address. The terminal identifier <NUM> may be used for determining terminal type at operation <NUM> (legacy or next generation), for example, with a lookup table. The determined terminal type may be used for composing a burst structure <NUM> at operation <NUM>. Portions of the burst structure <NUM> may change by terminal type. Operation <NUM> may compose the burst structure <NUM> by generating and including symbols for a PUI (public user information) <NUM>, optionally an extended PUI <NUM>, optionally a ULMAP (uplink map) <NUM>, and optionally the payload <NUM>. The payload <NUM> of the MAC/RLC structure <NUM> may be segmented, if necessary, and disposed in one or more of the burst structure <NUM>.

The burst structure <NUM> is provided to the PHY layer <NUM> by the MAC/RLC layer <NUM> to format a burst <NUM>. The burst <NUM> is a single unit of transmission on a radio path defined in terms of a RF (radio frequency) channel, a RF power profile and modulation symbols. The burst <NUM> may be sent in a defined time and frequency resource (i.e., time and frequency slots). The burst <NUM> includes multiple fields: G (guard) periods <NUM>, multiple UWs (unique words) <NUM>, the PUI <NUM> from the burst structure <NUM>, the extended PUI <NUM> from the burst structure <NUM>, the ULMAP <NUM> from the burst structure <NUM>, and PRI symbols <NUM>. The payload <NUM> may be in-contiguously (as shown) or contiguously disposed as the PRI symbols <NUM> of the burst <NUM>. In some embodiments, the payload <NUM> and the PRI symbols <NUM> may be different.

The fields in a burst <NUM> or a burst structure <NUM>, and other terms in the present teachings are defined as the following.

<FIG> illustrates an exemplary frequency and time grid used for resource allocation according to various embodiments.

<FIG> illustrates an exemplary frequency and time grid <NUM> used for resource allocation in a network that uses FDMA (Frequency division multiple access) and TDMA jointly. For example, a GMR-<NUM> satellite system is a FDMA/TDMA system. The physical layer resources are allocated in terms of a base frequency (for example, <NUM>) and a time slot (for example, <NUM>/<NUM>). Each PNB(m,n) (allocation block) occupies m x <NUM> base frequency bands and n x time slots. A PNB <NUM> illustrates an allocation block of one <NUM> base frequency band and <NUM> time slots, and may be represented as PNB(<NUM>,<NUM>). In similar vernacular, a PNB(<NUM>,<NUM>) (allocation <NUM> of <FIG>) represents a burst occupying a <NUM> (<NUM> x <NUM>) base frequency band and <NUM> (<NUM> x <NUM>/<NUM>) time slot. In this example, a frame has a duration of <NUM> with <NUM> time slots. As such, each time slot has a duration of <NUM>/<NUM>.

The next generation air interface supports signaling of 1x and 2x uplink allocations in a 5x downlink. The present teachings disclose a new ULMAP field in the next generation downlink bursts. The new burst types may be called PNB4(<NUM>,<NUM>), PNB4(<NUM>,<NUM>), PKAB4(<NUM>,<NUM>) with a ULMAP. These new bursts allow multiplexing of legacy terminals in the same carrier. The guard, UW, PHY header of the burst may remain the same as the legacy air interface. However, adding an additional field in the burst while keeping guard, UW, PHY header would necessitate a reduction in LPDC coded PRI symbols. In order to minimize cost involved in new LDPC code development and terminal memory requirement, already developed (<NUM>,<NUM>) and (<NUM>,<NUM>) LDPC code are reused in the following manner:.

For <NUM> PNB4(<NUM>,<NUM>)/PKAB4(<NUM>,<NUM>) burst with ULMAP, two methods are disclosed. In a method A, three fields in the burst header are used, where the PUI and Ext-PUI portions of the burst header are the same as those of a legacy air interface PNB(<NUM>,<NUM>) and the ULMAP is similar to the PNB(<NUM>,<NUM>) ext-PUI. In a method B, the PUI field is per the legacy air interface and the Ext-PUI and ULMAP fields form a combined field in the burst header.

Method A has common structure up to Ext-PUI and as such provides flexibility for future evolution of PNB4(<NUM>,<NUM>) with PUI and Ext-PUI only. Method B has two fields: PUI and ULMAP, minimizes the number of fields for PNB4(<NUM>,<NUM>)/PKAB4(<NUM>,<NUM>) with ULMAP burst, and the terminal may treat the front part (beyond PUI) differently for PNB4(<NUM>,<NUM>) and PNB4(<NUM>,<NUM>) processing.

To avoid allocating separate subbands to existing legacy and new terminals, the network may TDM the following bursts on the same subband, for example, a 5x carrier subband. Moreover, as the existing legacy terminals cannot process the new burst types, the new burst types need to be designed to be backward compatible with (i.e., no harm to) the legacy terminal operation. The legacy air interface burst formats are:.

The backward compatible Next generation air interface burst formats are: PNB4(<NUM>,<NUM>) with ULMAP, PNB4(<NUM>,<NUM>) with ULMAP and PKAB4(<NUM>,<NUM>) with ULMAP. In some embodiments, "PKAB4(<NUM>,<NUM>) with ULMAP" replaces PKAB(<NUM>,<NUM>) for a simpler network operation and terminal processing with the single PKAB format.

<FIG> illustrates an exemplary resource allocation according to various embodiments.

<FIG> illustrates different combinations of frequency and time resource allocations in an uplink transmission opportunity conveyed by a ULMAP. The gateway may transmit the USF bits in a downlink burst to the UT to indicate an uplink transmission opportunity, for example, in the burst structure <NUM>. The downlink received by the UT may be a 5x carrier (i.e., m=<NUM>), for example. However, the uplink allocation for the UT in the uplink transmission opportunity can be either on 1x carrier (allocation <NUM>), 2x carrier (allocation <NUM>) or 5x carrier (allocation <NUM> and allocation <NUM>). The allocation for the UT may depend on a UT capability (in terms of max EIRP), a backlog in the UT, available resources in the uplink, or the like. Allocation <NUM> is for <NUM> time slots (n=<NUM>); allocation <NUM> and allocation <NUM> are for <NUM> time slots (n=<NUM>); and allocation <NUM> is for <NUM> time slots (n=<NUM>).

In some embodiments, a gateway may have to send one or more of the PUI, Ext-PUI and ULMAP field in the downlink burst when the uplink allocation has a mix of different burst types with different slot duration and bandwidth.

According to the claimed invention, a legacy terminal declares a PUI error and treats the burst as not present when the decoded PUI has MCS = <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> &<NUM>. These MCS values are called Invalid MCSs. In some embodiments, the Network reserves one of the invalid MCS values (for example MCS = <NUM>) in PUI when a gateway transmits PNB4(<NUM>,<NUM>) with a ULMAP or PNB4(<NUM>,<NUM>) with a ULMAP. In some embodiments, the network may use the invalid MCS bit string in the PUI and introduce a new <NUM>-bit downlink MCS field in the ULMAP to indicate new PRI MCS. The following table illustrates a legacy terminal's reaction.

<FIG> illustrates a receive processing for a legacy terminal in some embodiments.

A process <NUM> for receive processing for a legacy terminal to handle legacy and next generation burst types over a common carrier is disclosed. The burst types may include burst types PNB2(<NUM>,<NUM>) <NUM>, PNB2(<NUM>,<NUM>) <NUM>, and PKAB(<NUM>,<NUM>) <NUM>.

A legacy terminal may perform burst detection <NUM> using a PUI decoder metric and decoded PUI MCS. If the decoder metric is lower than a predefined threshold or if the decoded MCS belong to invalid MCS, the terminal declares a burst not detected per <NUM> and repeats the receiver process with next received burst; otherwise a burst detected is declared. When a burst detected is declared, the terminal parses PUI and EXT PUI fields and performs the processing as shown per <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>. According to the claimed invention, as the next generation burst type encodes the PUI MCS field with an invalid MCS, the legacy terminal declares a burst not detected when a new burst type is received.

<FIG> illustrates a receive processing for a next generation terminal in some embodiments.

A process <NUM> for receive processing for a new terminal to handle legacy and next generation burst types over a common carrier is disclosed. The burst types may include burst types PKAB(<NUM>,<NUM>)) <NUM>, PKAB4(<NUM>,<NUM>) <NUM>, PNB4(<NUM>,<NUM>) <NUM>, PNB2(<NUM>,<NUM>) <NUM>, PNB2(<NUM>,<NUM>) <NUM>, PNB4(<NUM>,<NUM>) <NUM>, and PNB4(<NUM>,<NUM>) <NUM>.

A next generation terminal may perform burst detection <NUM> using a PUI decoder metric and decoded PUI MCS. If the decoder metric is lower than a predefined threshold, the terminal declares a burst not detected per <NUM> and repeats the receiver process with next received burst; otherwise a burst detected is declared. When a burst detected is declared, the terminal parses PUI and EXT PUI fields and performs the processing as shown per <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

A process <NUM> for receive processing for a new terminal to handle legacy and next generation burst types over a common carrier is disclosed. The burst types may include burst types PKAB(<NUM>,<NUM>) <NUM>, PNB4(<NUM>,<NUM>) <NUM>, PNB2(<NUM>,<NUM>) <NUM>, PNB2(<NUM>,<NUM>) <NUM>, and PNB4(<NUM>,<NUM>) <NUM>.

A next generation terminal may perform burst detection <NUM> using a PUI decoder metric and decoded PUI MCS. If the decoder metric is lower than a predefined threshold, the terminal declares a burst not detected per <NUM> and repeats the receiver process with next received burst; otherwise a burst detected is declared. When a burst detected is declared, the terminal parses PUI and EXT PUI fields and performs the processing as shown per <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> and <NUM>.

In addition to supporting the legacy burst formats, the present teachings disclose new burst formats. The new burst formats may have identical durations as the defined durations of the legacy burst formats, for example, <NUM>, <NUM>. Moreover, the positioning and durations of various guards and unique words in the new burst formats may be identical as the defined positioning and durations of the legacy formats. According to the claimed invention, the modulations and codings used in the ULMAP and PRI may not be supported by the legacy terminals. In the example, the QPSK (Quadrature Phase Shift Keying) or APSK (Amplitude Phase Shift Keying) are exemplary. The generic term QPSK covers specific implementations such as pi/<NUM>-QPSK and the like.

<FIG> each illustrate an exemplary <NUM> burst format according to various embodiments.

<FIG> illustrates a <NUM> burst format including a ULMAP segmented into two portions with a unique word disposed between the two portions. The second portion may have a duration of <NUM> between positions <NUM> to <NUM>. Exemplary modulations and codings for this new burst format are listed in the following table. In some embodiments, the burst format of <FIG> may be known as GMR-<NUM><NUM> (<NUM>,<NUM>) with ULMAP: type <NUM>.

<FIG> illustrates a <NUM> burst format including a ULMAP and a CH placeholder (reserved for future use or messages), where the ULMAP is segmented into two portions with a unique word disposed between the two portions. The second portion may have a duration of <NUM> between positions <NUM> to <NUM>. Exemplary modulations and codings for this new burst format are listed in the following table. In some embodiments, the burst format of <FIG> may be known as GMR-<NUM><NUM> (<NUM>,<NUM>) with ULMAP: type <NUM>.

<FIG> illustrates a <NUM> burst format separating a ULMAP and extended PUI. In some embodiments, the burst format of <FIG> may be known as PNB4(<NUM>,<NUM>). The presence of the ULMAP may be indicated through a use of spare bits in the extended PUI (similar to indication of presence of ULMAP in the <NUM> burst). This may be conceptually simple and allow unified processing at the receiver. In some embodiments, using the extended PUI and the ULMAP at the same time allows two additional burst types in future.

<FIG> illustrates a <NUM> burst format including a ULMAP without an extended PUI. In some embodiments, the burst format of <FIG> may be known as PNB4(<NUM>,<NUM>). Although processing of the burst format of <FIG> may not be as uniform as processing of the burst of <FIG>, it may be an attractive solution due to its simplicity. Currently processing of the burst format of <FIG> is the baseline to minimize terminal RX processing complexity.

<FIG> illustrates a method for communicating with a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface according to various embodiments.

A method <NUM> for communicating with a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface may include an operation <NUM> to assign a same carrier to the legacy terminal and the new terminal. The method <NUM> may include operation <NUM> to receive a terminal identifier and an optional payload for transmission at a MAC/RLC (Media Access Layer/Radio Link Control) layer. The method <NUM> may include operation <NUM> to determine if the terminal identifier is associated with the legacy terminal or the new terminal. The method <NUM> may include operation <NUM> to compose, based on the determining, a burst header. The method <NUM> may include operation <NUM> to format a burst including the burst header and the optional payload. The method <NUM> may include operation <NUM> to transmit the burst.

<FIG> illustrates a method for processing a burst at a terminal supporting a next generation air interface, which is not part of the claimed invention.

A method <NUM> for processing a burst at a terminal supporting a next generation air interface may include operation <NUM> to receive burst comprising an extended PUI (public user information). The method <NUM> may include operation <NUM> to check an integrity of the extended PUI with a colored CRC (Cyclic Redundancy Check). The method <NUM> may include operation <NUM> to extract a ULMAP from the burst when the ULMAP is indicated to be present by the extended PUI.

Having described preferred embodiments of a system and method (which are intended to be illustrative and not limiting), it is noted that modifications and variations can be made by persons skilled in the art considering the above teachings.

Claim 1:
A method (<NUM>) for communicating with a legacy terminal supporting a legacy air interface and a new terminal supporting a next generation air interface, the method comprising:
assigning (<NUM>) a same carrier to the legacy terminal and the new terminal;
receiving (<NUM>) a terminal identifier and an optional payload for transmission at a Media Access Layer/Radio Link Control "MAC/RLC" layer;
determining (<NUM>) if the terminal identifier is associated with the legacy terminal or the new terminal;
composing (<NUM>), based on the determining, a burst header; and
formatting (<NUM>) a burst comprising the burst header and the optional payload; and
transmitting (<NUM>) the burst,
wherein the legacy air interface defines one or more valid burst headers and one or more undefined burst headers,
the burst header is set to one of the one or more valid burst headers when the burst is associated with the legacy terminal, and
the burst header is set to one of the one or more undefined burst headers when the burst is associated with the new terminal, wherein at least one of the one or more undefined burst headers identifies a Modulation and Coding Scheme "MCS" unsupported by the legacy air interface.