Patent Description:
The present disclosure relates generally to communication systems, and more particularly, to design of code books in sparse code multiple access (SCMA) networks.

An example telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). LTE is designed to support mobile broadband access through improved spectral efficiency, lowered costs, and improved services using OFDMA on the downlink, SC-FDMA on the uplink, and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology.

In wireless communications systems employing CDMA, data symbols are spread over orthogonal or near orthogonal code sequences in which a binary code is mapped to a quadrature amplitude modulation (QAM) symbol before a spreading sequence is applied. Although this type of encoding may provide relatively higher coding rates, it may not be enough to meet the demands of current wireless networks.

As such, new techniques or mechanisms to achieve even higher coding rates are needed to meet the growing demands of the wireless networks. <CIT> discloses systems and methods for sparse code multiple access.

According to one example, a method for multilayer transmission in a wireless network is provided. The method includes generating, at a transmitter, a group of binary data bits for resources of each layer of a plurality of layers; mapping, at the transmitter, the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers; combining, at the transmitter, the code words; and transmitting, from the transmitter, the combined code word to a receiver in the wireless network.

In another example, an apparatus for multilayer transmission in a wireless network is provided. The apparatus includes means for generating, at a transmitter, a group of binary data bits for resources of each layer of a plurality of layers; means for mapping, at the transmitter, the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers; means for combining, at the transmitter, the code words; and means for transmitting, from the transmitter, the combined code word to receiver in the wireless network.

In a further example, an apparatus for multilayer transmission in a wireless network is provided. The apparatus includes a memory; and at least one processor coupled to the memory and configured to generate, at a transmitter, a group of binary data bits for resources of each layer of a plurality of layers; map, at the transmitter, the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers; combine, at the transmitter, the code words; and transmit, from the transmitter, the combined code word to receiver in the wireless network.

Additionally, in another example, a computer readable medium storing computer executable code for a multilayer transmission is provided. The computer readable medium includes code to generate, at a transmitter, a group of binary data bits for resources of each layer of a plurality of layers; map, at the transmitter, the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers; combine, at the transmitter, the code words; and transmit, from the transmitter, the combined code word to receiver in the wireless network.

The drawings include like reference numbers for like elements, and may represent optional components or actions using dashed lines.

Accordingly, in one or more example aspects, the functions described may be implemented in hardware, software, or any combination thereof.

The present disclosure relates to a multilayer transmission at base station and/or a user equipment.

<FIG> is a diagram illustrating an example of a wireless communications system and an access network <NUM> including at least one base station <NUM> configured to include a multilayer transmission component <NUM> for multilayer transmission to at least one UE <NUM> in accordance with various aspects of the present disclosure. The wireless communications system <NUM> (also referred to as a wireless wide area network (WWAN)) includes base stations <NUM>, UEs <NUM>, and an Evolved Packet Core (EPC) <NUM>. The macro cells include eNBs.

A network that includes both small cell and macro cells may be known as a heterogeneous network. A heterogeneous network may also include Home Evolved NodeBs (eNBs) (HeNBs), which may provide service to a restricted group known as a closed subscriber group (CSG). The communication links <NUM> may use MIMO antenna technology, including spatial multiplexing, beamforming, and/or transmit diversity. The base stations <NUM> / UEs <NUM> may use spectrum up to Y MHz (e.g., <NUM>, <NUM>, <NUM>, <NUM>) bandwidth per carrier allocated in a carrier aggregation of up to a total of Yx MHz (x component carriers) used for transmission in each direction. Allocation of carriers may be asymmetric with respect to DL and UL (e.g., more or less carriers may be allocated for DL than for UL).

The wireless communications system <NUM> may further include a Wi-Fi access point (AP) <NUM> in communication with Wi-Fi stations (STAs) <NUM> via communication links <NUM> in a <NUM> unlicensed frequency spectrum.

When operating in an unlicensed frequency spectrum, the small cell <NUM>' may employ LTE and use the same <NUM> unlicensed frequency spectrum as used by the Wi-Fi AP <NUM>. The small cell <NUM>', employing LTE in an unlicensed frequency spectrum, may boost coverage to and/or increase capacity of the access network. LTE in an unlicensed spectrum may be referred to as LTE-unlicensed (LTE-U), licensed assisted access (LAA), or MuLTEfire.

The IP Services <NUM> may include the Internet, an intranet, an IP Multimedia Subsystem (IMS), a PS Streaming Service (PSS), and/or other IP services.

The base station may also be referred to as a Node B, an access point, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. The eNB <NUM> provides an access point to the EPC <NUM> for a UE <NUM>. Examples of UEs <NUM> include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, a tablet, a smart device, a wearable device, or any other similar functioning device.

<FIG> is a diagram <NUM> illustrating an example of a DL frame structure in LTE, which may be an example of a frame structure that may be transmitted by at least one base station <NUM> configured to multilayer transmission component <NUM> for transmitting data in accordance with various aspects of the present disclosure.

<FIG> is a diagram <NUM> illustrating an example of channels within the DL frame structure in LTE that may be transmitted by base station <NUM> and used by UE <NUM> as described herein.

<FIG> is a diagram <NUM> illustrating an example of an UL frame structure in LTE that may be used by UE <NUM>.

<FIG> is a diagram <NUM> illustrating an example of channels within the UL frame structure in LTE that may be used by UE <NUM>.

In LTE, a frame (<NUM>) may be divided into <NUM> equally sized subframes. Each subframe may include two consecutive time slots. A resource grid may be used to represent the two time slots, each time slot including one or more time concurrent resource blocks (RBs) (also referred to as physical RBs (PRBs)). In LTE, for a normal cyclic prefix, an RB contains <NUM> consecutive subcarriers in the frequency domain and <NUM> consecutive symbols (for DL, OFDM symbols; for UL, SC-FDMA symbols) in the time domain, for a total of <NUM> REs. For an extended cyclic prefix, an RB contains <NUM> consecutive subcarriers in the frequency domain and <NUM> consecutive symbols in the time domain, for a total of <NUM> REs. Additionally, the RBs described above may also be referred to as "resources," "orthogonal resources," etc. in the present disclosure.

As illustrated in <FIG>, some of the REs carry DL reference (pilot) signals (DL-RS) for channel estimation at the UE. The DL-RS may include cell-specific reference signals (CRS) (also sometimes called common RS), UE-specific reference signals (UE-RS), and channel state information reference signals (CSI-RS). <FIG> illustrates CRS for antenna ports <NUM>, <NUM>, <NUM>, and <NUM> (indicated as R<NUM>, R<NUM>, R<NUM>, and R<NUM>, respectively), UE-RS for antenna port <NUM> (indicated as R<NUM>), and CSI-RS for antenna port <NUM> (indicated as R).

<FIG> illustrates an example of various channels within a DL subframe of a frame. The physical control format indicator channel (PCFICH) is within symbol <NUM> of slot <NUM>, and carries a control format indicator (CFI) that indicates whether the physical downlink control channel (PDCCH) occupies <NUM>, <NUM>, or <NUM> symbols (<FIG> illustrates a PDCCH that occupies <NUM> symbols). The PDCCH carries downlink control information (DCI) within one or more control channel elements (CCEs), each CCE including nine RE groups (REGs), each REG including four consecutive REs in an OFDM symbol. A UE may be configured with a UE-specific enhanced PDCCH (ePDCCH) that also carries DCI. The ePDCCH may have <NUM>, <NUM>, or <NUM> RB pairs (<FIG> shows two RB pairs, each subset including one RB pair). The physical hybrid automatic repeat request (ARQ) (HARQ) indicator channel (PHICH) is also within symbol <NUM> of slot <NUM> and carries the HARQ indicator (HI) that indicates HARQ acknowledgement (ACK) / negative ACK (NACK) feedback based on the physical uplink shared channel (PUSCH). The primary synchronization channel (PSCH) is within symbol <NUM> of slot <NUM> within subframes <NUM> and <NUM> of a frame, and carries a primary synchronization signal (PSS) that is used by a UE to determine subframe timing and a physical layer identity. The secondary synchronization channel (SSCH) is within symbol <NUM> of slot <NUM> within subframes <NUM> and <NUM> of a frame, and carries a secondary synchronization signal (SSS) that is used by a UE to determine a physical layer cell identity group number. Based on the PCI, the UE can determine the locations of the aforementioned DL-RS. The physical broadcast channel (PBCH) is within symbols <NUM>, <NUM>, <NUM>, <NUM> of slot <NUM> of subframe <NUM> of a frame, and carries a master information block (MIB). The MIB provides a number of RBs in the DL system bandwidth, a PHICH configuration, and a system frame number (SFN).

As illustrated in <FIG>, some of the REs carry demodulation reference signals (DM-RS) for channel estimation at the eNB. The UE may additionally transmit sounding reference signals (SRS) in the last symbol of a subframe. The SRS may be used by an eNB for channel quality estimation to enable frequency-dependent scheduling on the UL. <FIG> illustrates an example of various channels within an UL subframe of a frame. A physical random access channel (PRACH) may be within one or more subframes within a frame based on the PRACH configuration. The PRACH may include six consecutive RB pairs within a subframe. The PRACH allows the UE to perform initial system access and achieve UL synchronization. A physical uplink control channel (PUCCH) may be located on edges of the UL system bandwidth.

<FIG> is a block diagram of an eNB <NUM> in communication with UE <NUM> in an access network. In an aspect, base station <NUM> and/or UE <NUM> may be configured to include multilayer transmission component <NUM>. In an aspect, multilayer transmission component <NUM> may be configured to manage transmissions to multiple layers. The controller/processor <NUM> provides RRC layer functionality associated with broadcasting of system information (e.g., MIB, SIBs), RRC connection control (e.g., RRC connection paging, RRC connection establishment, RRC connection modification, and RRC connection release), inter radio access technology (RAT) mobility, and measurement configuration for UE measurement reporting; PDCP layer functionality associated with header compression / decompression, security (ciphering, deciphering, integrity protection, integrity verification), and handover support functions; RLC layer functionality associated with the transfer of upper layer packet data units (PDUs), error correction through ARQ, concatenation, segmentation, and reassembly of RLC service data units (SDUs), re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto transport blocks (TBs), demuliplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

The symbols on each subcarrier, and the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB <NUM>. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB <NUM> on the physical channel.

Similar to the functionality described in connection with the DL transmission by the eNB <NUM>, the controller/processor <NUM> provides RRC layer functionality associated with system information (e.g., MIB, SIBs) acquisition, RRC connections, and measurement reporting; PDCP layer functionality associated with header compression / decompression, and security (ciphering, deciphering, integrity protection, integrity verification); RLC layer functionality associated with the transfer of upper layer PDUs, error correction through ARQ, concatenation, segmentation, and reassembly of RLC SDUs, re-segmentation of RLC data PDUs, and reordering of RLC data PDUs; and MAC layer functionality associated with mapping between logical channels and transport channels, multiplexing of MAC SDUs onto TBs, demuliplexing of MAC SDUs from TBs, scheduling information reporting, error correction through HARQ, priority handling, and logical channel prioritization.

Channel estimates derived by a channel estimator <NUM> from a reference signal or feedback transmitted by the eNB <NUM> may be used by the TX processor <NUM> to select the appropriate coding and modulation schemes, and to facilitate spatial processing.

The UL transmission is processed at the eNB <NUM> in a manner similar to that described in connection with the receiver function at the UE <NUM>.

Referring to <FIG>, in an aspect, a wireless communications system <NUM> (which may be the same as or similar to wireless communications system and an access network <NUM> of <FIG>) includes a plurality of UEs (UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, which may be the same or similar to UE <NUM> of <FIG>) in communication coverage of at least one base station <NUM>. The base station <NUM> (collectively referred to as Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN)) may interface with an EPC (such as EPC <NUM> of <FIG>) through backhaul links <NUM> (e.g., S1 interface). In an aspect, base station <NUM> may include one or more processors (not shown) and, optionally, memory (not shown), that may operate in combination with multilayer transmission component <NUM> for transmitting data to the UEs. In an additional or optional aspect, any of the UEs (e.g., (UEs <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>) may also include multilayer transmission component <NUM>, one or more processors (not shown), optionally, memory (not shown), that may operate in combination with multilayer transmission component <NUM> for transmitting data from the UE to the base station.

In an aspect, base station <NUM> which may include multilayer transmission component <NUM> may send a transmission (e.g., SCMA transmission) <NUM> on downlink <NUM>-a (only one downlink shown for simplicity) to one or more UEs (e.g., <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>). Although six UEs (referred to as users or layers in the present disclosure) are shown in the <FIG>, the present disclosure is not limited to six layers. In an example, four resources may be available at the base station for transmitting data to the six layers, e.g., users/UEs. At each layer, only two resources may be used for transmitting the data and no data is transmitted on the unused resources. At each layer, the data available for transmission on the downlink is converted to binary data bits. The binary data bits are then mapped to code words of a signal constellation (e.g., a code book of the respective layer) to maximize the distance between code words of a resource. The code words for all the layers are combined to generate a combined code word prior to transmission.

For example, base station <NUM> and/or multilayer transmission component <NUM> may be configured for multilayer transmission (e.g., transmission <NUM>) by generating a group of binary data bits for resources of each of the layers, mapping each of the groups of binary data bits to a respective code word in a signal constellation, wherein the mapping of each of the groups of binary data bits is based at least on maximizing a distance between the code words within each of the layers, combining the code words, and transmitting the combined code word. Additionally, the transmission <NUM> may be a sparse code multiple access transmission to achieve multi-dimensional coded modulation for non-orthogonal multiple access to meet the growing demands of wireless networks.

In an additional aspect, for example, one or more of the UEs (e.g., UE <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>) may include multilayer transmission component <NUM> and may send a transmission (e.g., SCMA transmission) on uplink <NUM>-b (only one uplink shown for simplicity reasons) to the base station. As the uplinks are synchronized, the transmissions from the one or more UEs are combined at a receiving antenna of the base station. Further, the base station decodes the data transmitted on each layer using a code book associated with the respective layer to determine the data transmitted on each layer. Furthermore, a UE may be assigned more than one layer by the base station.

In a further additional aspect, multilayer transmission component <NUM> may include a binary data generating component <NUM>, a mapping component <NUM>, a combining component <NUM>, and/or a transmitting component <NUM> for performing the multilayer transmission. Further, multilayer transmission component <NUM> and other components (<NUM>, <NUM>, <NUM>, and/or <NUM>) may reside at base station <NUM> for multilayer transmission from the base station to the one or more UEs and/or at UE <NUM> for multilayer transmission from the one or more UEs to the base station.

<FIG> is a diagram illustrating a non-limiting example of a multilayer transmission <NUM> in a wireless communications system such as system <NUM> (<FIG>) or system <NUM> (<FIG>).

For example, in an aspect, a non-limiting example with six layers, four resources is described. Each layer uses two resources out of the four available resources, as described below in reference to <FIG>. That is, each layer uses two resources (out of the four available resources) for transmission and no data is transmitted on the other two non-used resources. The resources used by a layer may be referred to as non-zero resources and the resources not used by the layer may be referred to as zero resources. Further, in an aspect, the resources may be orthogonal to each other (e.g., orthogonal resources) and may be RBs as described above in reference to <FIG>. Additionally, a <NUM>st resource and a <NUM>nd resource in <FIG> represent the used (e.g., non-zero) resources at a layer and may include any two of the four resources (e.g., any two of resources R1, R2, R3, and/or R4, as described below in reference to <FIG>).

At each layer, an FEC encoder (e.g., FEC encoders <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and/or <NUM>) converts the data available for transmission at each layer to binary data bits. For instance, data available for transmission at layer C1 may be converted to binary data bits, <NUM> or <NUM>, for each of the resources, e.g., for <NUM>st resource and the <NUM>nd resource. For example, in an aspect, FEC encoder <NUM> may output binary data bits (<NUM>,<NUM>) at layer C1 for the two resources used by layer C1. The two bits are for the two resources used at layer C1 (e.g., two non-zero resources at layer C1). In an additional or optional aspect, FEC encoder <NUM> may output binary data bits (<NUM>,<NUM>), (<NUM>,<NUM>), or (<NUM>, <NUM>) at layer C1 based on the data available for transmission at the first and second resources of layer C1. A similar procedure may be used at layers C2-C6 for converting the data available for transmission at layers C2-C6 into binary data bits. For example, in an additional or optional aspect, FEC encoder <NUM> may output binary data bits (<NUM>,<NUM>), (<NUM>,<NUM>), (<NUM>,<NUM>), and/or (<NUM>,<NUM>) at layer C6 corresponding to the two resources used by layer C6. Although, the above example is described in the context of two bits, the disclosure is not limited to two bits for each layer. For instance, four bits may be used for each layer, e.g., (<NUM>,<NUM>,<NUM>,<NUM>), (<NUM>,<NUM>,<NUM>,<NUM>), (<NUM>,<NUM>,<NUM>,<NUM>), etc..

In an aspect, the output of an FEC encoder is mapped to code words. For instance, in an aspect, output of FEC encoder <NUM> (e.g., (<NUM>,<NUM>)) may be mapped to <NUM> and -<NUM>. The mapping of the binary data bits to code words in a signal constellation (also referred to as a "code book") is based at least on maximizing distance between the code words of different layers, specifically the code words that are close. For example, as described below in reference to <FIG>, binary data bits (<NUM>,<NUM>) associated with layer C1 are mapped to (<NUM>, -<NUM>), binary data bits (<NUM>,<NUM>) associated with layer C1 are mapped to (<NUM>, <NUM>), binary data bits (<NUM>,<NUM>) associated with layer C1 are mapped to (-<NUM>, -<NUM>), and binary data bits (<NUM>,<NUM>) associated with layer C1 are mapped to (-<NUM>, <NUM>). For instance, the binary data bits (<NUM>,<NUM>) and (<NUM>,<NUM>) are separated by the maximum distance possible in the signal constellation by mapping them to (<NUM>, -<NUM>) and (<NUM>,<NUM>). This allows the receiver (e.g., receiver at UE <NUM> or base station <NUM>) to correctly detect the pair of transmitted bits.

Additionally, each of the layers C2-C6 may have its own code book such that the mapping of the binary bits of a layer maximizes distance between the code words between the layers. Although, the mapping of resources (e.g., used/non-zero resources) at layer C1 is described above, similar mapping procedures may be designed or implemented for resources at layers C2-C6. For example, binary data bits of layers <NUM>-<NUM> associated with the first and second resources may be mapped as shown below:.

According to the invention, the code words for each of the layers are combined, e.g., to a combined code word, prior to transmission. For instance, in an aspect, the code words associated with all the layers of a resource are combined via a linear combiner <NUM> to produce a combined code word for that resource. For example, code words for resource "R1," e.g., code words <NUM>, c21, and c31 may be combined to produce a combined code word "A" to be transmitted on resource R1. Additionally, code words for resource "R2," e.g., code words -<NUM>, c42, and c52 may be combined to produce a combined code word "B" to be transmitted on resource R2. As a result, on the receiving side (e.g., at UE <NUM> or base station <NUM>), the received signal will be a linear combination of all the layers on a particular resource. As such, when the receiver receives the multilayer transmission <NUM>, the receiver searches for combinations of all possible signals for decoding at the receiver. As described above, data for multiple layers are transmitted from the base station. In additional aspect, the layers may be assigned to one UE, two UEs, three UEs, and so on. For instance, all the layers (i.e., six layers) may be assigned to UE <NUM> for increasing throughput at the UE.

Additionally, the signal constellation/code book mechanism/procedure described above is from a base station perspective, and a same/similar mechanism/procedure may be defined/implemented at a UE for transmission on an uplink at the base station.

<FIG> is a diagram illustrating a non-limiting example of resource allocation <NUM> among various layers in a wireless communications system such as system <NUM> (<FIG>) or system <NUM> (<FIG>).

For example, in an aspect, the number of resources may be defined as "M" and the number of layers may be defined as "N," wherein the value of M is less than N. That is, the number of resources is less than the number of layers (e.g., UEs). This may result in the resources being shared by the layers (e.g., non-dedicated resources). The data may be transmitted on a downlink from base station <NUM> to one or more UEs <NUM> or on the uplink from one or more UEs <NUM> to base station <NUM>. Although <FIG> is described in the context of four resources and six layers, the procedure/mechanism may be applied to any other numbers of resources and/or layers.

In an aspect, the resources may be represented by rows - R1 (<NUM>), R2 (<NUM>), R3 (<NUM>), and R4 (<NUM>) and the layers may be represented by columns - C1 (<NUM>), C2 (<NUM>), C3 (<NUM>), C4 (<NUM>), C5 (<NUM>), and C6 (<NUM>). Each of the resources may comprise one or more RBs which are described above in detail in reference to <FIG>. Additionally, as described above in reference to <FIG>, each of the layers may use two resources (out of a total of the four available resources) for transmission. That is, data is transmitted on only two resources (out of the four resources) for each layer and no data is transmitted on the other two resources. In an example aspect, the resources used by a layer may be referred to as "used" or "non-zero" resources and the resources not used by the layer may be referred to as "unused" or "zero" resources.

In an aspect, the four resources may be allocated or assigned among the six layers with each of the layers using two resources for transmission as illustrated in <FIG>. For example, layer C1 (<NUM>) may use resources R1 (<NUM>) and R2 (<NUM>), layer C2 (<NUM>) may use resources R1 (<NUM>) and R3 (<NUM>), layer C3 (<NUM>) may use resources R1 (<NUM>) and R4 (<NUM>), layer C4 (<NUM>) may use resources R2 (<NUM>) and R3 (<NUM>), layer C5 (<NUM>) may use resources R2 (<NUM>) and R4 (<NUM>), and layer C6 (<NUM>) may use resources R3 (<NUM>) and R4 (<NUM>).

Additionally, for each of the layers, no transmission occurs on each of the other two resources not used by a layer. For example, no transmission occurs on resources R3 (<NUM>) and R4 (<NUM>) for layer C1 (<NUM>), no transmission occurs for resources R2 and R4 for layer C2, no transmission occurs for resources R2 and R3 for layer C3, no transmission occurs for resources R1 and R4 for layer C4, no transmission occurs for resources R1 and R3 for layer C5, and no transmission occurs for resources R1 and R1 for layer C6.

According to the invention, a pair of layers are configured as an orthogonal pair. For example, layers C1 (<NUM>) and C6 (<NUM>) may be configured as an orthogonal pair, layers C2 (<NUM>) and C5 (<NUM>) may be configured as another orthogonal pair, and/or layers C3 (<NUM>) and C4 (<NUM>) may be configured as an additional orthogonal pair. That is, the six layers are configured as three orthogonal pairs. In an aspect, a pair of layers may be configured as an orthogonal pair if they use different resources for transmission. For instance, layer C1 (<NUM>) uses resources R1 (<NUM>) and R2 (<NUM>) for transmission and layer C6 (<NUM>) uses resources R3 (<NUM>) and R4 (<NUM>) for transmission. As the resources used by layers C1 and C6 are different resources, layers C1 and C6 may be configured or defined as an orthogonal pair. Further, layer C2 uses resources R1 and R3 for transmission and layer C5 uses resources R3 and R4 for transmission. As the resources used by layers C2 and C5 are different, layers C2 and C5 are defined as an orthogonal pair. Furthermore, layer C3 uses resources R1 and R4 for transmission and layer C4 uses resources R2 and R3 for transmission. As the resources used by layers C3 and C4 are different resources (in other words, different orthogonal resources), layers C1 and C6 are defined as an orthogonal pair.

According to the invention, layers are rotated to increase distance between code words of each of the layers. For example, in an aspect, layer C2 (<NUM>) may be rotated by <NUM>° from layer C1 (<NUM>) to increase the distance between the code words, for example, in two dimension, from layer C1. Further, layer C3 (<NUM>) may be rotated by <NUM>° from layer C1 to increase the distance, for example, in two dimension, from layer C1. That is, layer C3 is rotated an additional <NUM>° from layer C2 to increase the distance from C2. This may increase the success rate of decoding at the receiver when the receiver is decoding the data received at the receiver as the code words are separated. In an additional or optional aspect, layer C2 (<NUM>) may be rotated by <NUM>° from layer C1 (<NUM>) to increase the distance between the code words, for example, in two dimension, from layer C1. Further, layer C3 (<NUM>) may be rotated by <NUM>° from layer C1 to increase the distance, for example, in two dimension, from layer C1. That is, layer C3 is rotated an additional <NUM>° from layer C2 to increase the distance from C2. As the layers are rotated differently, the performance at the receiving end may differ as well. For instance, the performance achieved with rotating the layers <NUM>°/<NUM>° is better than the performance achieved by rotating the layers <NUM>°/<NUM>° as illustrated in <FIG>, <FIG>, <FIG>.

<FIG> is a diagram illustrating a non-limiting example of mapping binary data bits of a group of layers to code words in a wireless communications system such as system <NUM> (<FIG>) or system <NUM> (<FIG>).

For example, in an aspect, binary data bits associated with each of the resources of the layers are mapped to code words in a signal constellation (e.g., a codebook), wherein each of the layers may have its own codebook. For instance, in reference to layer C1, binary data bits "<NUM>" and "<NUM>" (represented by (<NUM>,<NUM>) in <FIG>) associated with resources R1 and R2 may be mapped to "<NUM>" and "-<NUM>," respectively. Additionally, in reference to layer C1, binary data bits (<NUM>,<NUM>) associated with resources R1 and R2 may be mapped to "<NUM>" and "<NUM>," respectively; binary data bits (<NUM>,<NUM>) associated with resources R1 and R2 may be mapped to "-<NUM>" and "-<NUM>," respectively; and binary data bits (<NUM>,<NUM>) associated with resources R1 and R2 may be mapped to "-<NUM>" and "<NUM>," respectively. For instance, in an aspect, the mapping of resources, e.g., R1 and R2 of layer C1, to code words <NUM> and -<NUM>, is performed in such as way the distance between the code words (of the signal constellation or code book) is maximized to increase the likelihood of successful decoding at the receiver. Although, the mapping of the binary data bits to code words in a signal constellation is described above in the context of one layer, e.g., layer C1, similar mapping procedure may be implemented for each of the other layers.

<FIG> is a diagram illustrating a non-limiting example of mapping of a group of binary data bits to code words in a wireless communications system such as system <NUM> (<FIG>) or system <NUM> (<FIG>). For example, the mapping of a group of binary data bits associated with layer C1 to code words in a signal constellation (e.g., a codebook) of layer C1 are shown in <FIG>.

<FIG> illustrate non-limiting examples of code book designs <NUM> and <NUM> in a wireless communications system such as system <NUM> (<FIG>) or system <NUM> (<FIG>). For example, <FIG> illustrates a code book design for layer C1 with the signal constellation rotated by <NUM>° for layer C2 and <NUM>° for layer C3 (referred to as "Design <NUM>"). Additionally, <FIG> illustrates an additional code book design for layer C1 with the signal constellation rotated by <NUM>° for layer C2 and <NUM>° for layer C3 (referred to as "Design <NUM>").

<FIG> is a diagram illustrating code book performance with six layers, <NUM> resources (or symbols) per layers, and <NUM> bits used per each layer. As illustrated in <FIG>, the performance of Design <NUM> (i.e., rotated by <NUM>°/<NUM>°) is relatively better than the performance of Design <NUM> (i.e., rotated by <NUM>°/<NUM>°), both of which are relatively better than know code book designs.

<FIG> illustrate code book performance with known code book designs (<FIG>) and Design <NUM> (i.e., rotated by <NUM>°/<NUM>°) and Design <NUM> (i.e., rotated by <NUM>°/<NUM>°).

<FIG> illustrate code book performance with a known code book design, and Design <NUM> (i.e., rotated by <NUM>°/<NUM>°) and Design <NUM> (i.e., rotated by <NUM>°/<NUM>°) in accordance with aspects of the present disclosure.

<FIG> is a flow diagram of an aspect of a multilayer transmission, which may be executed by the multilayer transmission component <NUM> of <FIG>. Referring to <FIG>, a base station such as base station <NUM> and/or UE <NUM> (<FIG> and <FIG>) may include one or more processors to perform an aspect of a method <NUM> for a multilayer transmission. While, for purposes of simplicity of explanation, the method is shown and described as a series of acts, it is to be understood and appreciated that the method is not limited by the order of acts, as some acts may, in accordance with one or more embodiments, occur in different orders and/or concurrently with other acts from that shown and described herein. For example, it is to be appreciated that a method could alternatively be represented as a series of interrelated states or events, such as in a state diagram. Moreover, not all illustrated acts may be required to implement a method in accordance with one or more features described herein.

In an aspect, at block <NUM>, the method <NUM> may include generating, at a transmitter, a group of binary data bits for resources of each layer of a plurality of layers. For example, in an aspect, base station <NUM> and/or multilayer transmission component <NUM> may generate a group of binary data bits (for example, (<NUM>,<NUM>) for layer C1, etc.) for resources of all six layers. In an aspect, binary data generating component <NUM> may generate the group of binary data bits for resources of each layer of the plurality of layers. In an additional or optional aspect, generating a group of binary data bits may be performed by/at a FEC encoder (e.g., FEC encoder <NUM> for layer C1). In an additional or optional aspect, UE <NUM> and/or multilayer transmission component <NUM> may generate a group of binary data bits (for example, (<NUM>,<NUM>) for layer C1, etc.) for resources of all six layers.

In an aspect, at block <NUM>, the method <NUM> may include the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers. For example, in an aspect, base station <NUM> and/or multilayer transmission component <NUM> may map each of the groups of binary data bits (for example, (<NUM>,<NUM>)) to respective code words (for example, (<NUM>, -<NUM>)) in a signal constellation , wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers (e.g., distance is maximized between <NUM> and -<NUM>). In an aspect, mapping component <NUM> may perform the mapping. In an additional or optional aspect, mapping may be performed by at/by a code book (e.g., code book <NUM> for layer C1). In an additional or optional aspect, UE <NUM> and/or multilayer transmission component <NUM> may map the group of binary data bits of each layer of the plurality of layers to respective code words in a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers.

In an aspect, at block <NUM>, the method <NUM> may include combining, at the transmitter, the code words. For example, in an aspect, base station <NUM> and/or multilayer transmission component <NUM> may combine the code words at the transmitter, e.g., prior to transmission. In an aspect, combining component <NUM> may perform the combining. In an additional or optional aspect, the combining may be performed at/by a linear combiner <NUM>. In an additional or optional aspect, UE <NUM> and/or multilayer transmission component <NUM> may combine, at the transmitter, the code words.

In an aspect, at block <NUM>, the method <NUM> may include transmitting, from the transmitter, the combined code word to a receiver in the wireless network. For example, in an aspect, in an aspect, base station <NUM> and/or multilayer transmission component <NUM> may transmit the combined <NUM>. In an aspect, transmitting component <NUM> may perform the transmission. In an additional or optional aspect, UE <NUM> and/or multilayer transmission component <NUM> may transmit the combined code word to a receiver in the wireless network.

In an example aspect, base station <NUM> may be the transmitter and UE <NUM> may be the receiver, for example, in a downlink SCMA transmission from base station <NUM> to UE <NUM>. In an additional example aspect, UE <NUM> may be the transmitter and base station <NUM> may be the receiver, for example, in an uplink SCMA transmission from UE <NUM> to base station <NUM>.

<FIG> is a conceptual data flow diagram <NUM> illustrating the data flow between different means/components in an exemplary apparatus <NUM> that includes multilayer transmission component <NUM>, which may be the same as or similar to multilayer transmission component <NUM> of <FIG> for multilayer transmission. The apparatus may be a base station, which may be base station <NUM> of <FIG> or <FIG>, and/or a UE which may be UE <NUM> of <FIG> or <FIG>. The apparatus includes a binary data generating component <NUM> to generate a group of binary data bits for resources of each of the layers, a mapping component <NUM> to map each of the groups of binary data bits to a respective code word in a signal constellation, a combining component <NUM> to combine the code words, and a transmission component <NUM> to transmit the combined code word, and a reception component <NUM> that receives one or more signals (e.g., combined code words) from UE <NUM>.

<FIG> is a diagram <NUM> illustrating an example of a hardware implementation for an apparatus <NUM>' employing a processing system <NUM> that includes multilayer transmission component <NUM> (of <FIG>), which may be the same as or similar to multilayer transmission component <NUM> (of <FIG>) for multilayer transmission. The processing system <NUM> may be implemented with a bus architecture, represented generally by bus <NUM>. The bus <NUM> may include any number of interconnecting buses and bridges depending on the specific application of the processing system <NUM> and the overall design constraints. The bus <NUM> links together various circuits including one or more processors and/or hardware components, represented by the processor <NUM>, components <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and computer-readable medium / memory <NUM>. The bus <NUM> may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.

The processing system <NUM> may be coupled to a transceiver <NUM>. The transceiver <NUM> is coupled to one or more antennas <NUM>. The transceiver <NUM> provides a means for communicating with various other apparatus over a transmission medium. The transceiver <NUM> receives a signal from the one or more antennas <NUM>, extracts information from the received signal, and provides the extracted information to the processing system <NUM>, specifically the reception component <NUM>. In addition, the transceiver <NUM> receives information from the processing system <NUM>, specifically the transmission component <NUM>, and based on the received information, generates a signal to be applied to the one or more antennas <NUM>. The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium / memory <NUM>. The processor <NUM> is responsible for general processing, including the execution of software stored on the computer-readable medium / memory <NUM>. The software, when executed by the processor <NUM>, causes the processing system <NUM> to perform the various functions described supra for any particular apparatus. The computer-readable medium / memory <NUM> may also be used for storing data that is manipulated by the processor <NUM> when executing software. The processing system <NUM> further includes at least one of the components <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. The components may be software components running in the processor <NUM>, resident/stored in the computer readable medium / memory <NUM>, one or more hardware components coupled to the processor <NUM>, or some combination thereof.

In one configuration, the apparatus <NUM>/<NUM>' for wireless communication includes means for generating a group of binary data bits for resources of each of the layers; means for mapping each of the groups of binary data bits to a respective code word in a signal constellation , wherein the mapping of each of the groups of binary data bits is based at least on maximizing a distance between the code words within each of the layers; means for combining the code words; and means for transmitting the combined code word. In an additional aspect, the processing system <NUM> may include the TX Processor <NUM>, the RX Processor <NUM>, and the controller/processor <NUM>. As such, in another configuration, the aforementioned means may be the TX Processor <NUM>, the RX Processor <NUM>, and the controller/processor <NUM> configured to perform the functions recited by the aforementioned means.

Claim 1:
A method of a multilayer transmission in a wireless network (<NUM>), performed by a transmitter and comprising:
generating data for transmission for each layer of a plurality of layers (C1-C6);
converting the data for each layer into a respective group of data bits for the respective layer;
mapping the group of data bits for each layer to respective code words associated with a signal constellation, wherein the mapping is based at least on maximizing a distance between the code words within each layer of the plurality of layers;
linearly combining the code words for the plurality of layers for each resource of a plurality of resources (R1-R4) into a combined code word (<NUM>, A, B, C, D) for the respective resource; and
transmitting the combined code words (<NUM>, A, B, C, D) for the plurality of resources (R1-R4);
wherein the method further comprises:
rotating the signal constellation across a plurality of orthogonal layer pairs for increasing the distance between the code words in two dimension, wherein the plurality of layers are configured as the plurality of orthogonal layer pairs, and wherein at least one of the plurality of orthogonal layer pairs is obtained by rotating the signal constellation by a number of degrees.