Patent Publication Number: US-11039428-B2

Title: System and method for scalable digital communications with adaptive system parameters

Description:
This application is a continuation of U.S. patent application Ser. No. 14/453,875, filed Aug. 7, 2014, entitled “System and Method for Scalable Digital Communications with Adaptive System Parameters,” which claims the benefit of U.S. Provisional Application No. 61/863,213, filed on Aug. 7, 2013, entitled “System and Method for Scalable Sparse Code Multiple Access with Adaptive System Parameters,” which applications are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates generally to digital communications, and more particularly to a system and method for scalable digital communications with adaptive system parameters. 
     BACKGROUND 
     Different radio access techniques exist for different purposes or applications. However, there is no general framework and mechanism to put them under the same umbrella and switch among them depending on the requirements of particular situations. These techniques include sparse code multiple access (SCMA), multicarrier modulations such as orthogonal frequency division multiplexing (OFDM), downlink (DL) user superposition, non-orthogonal multiple access (NOMA), code division multiple access (CDMA), uplink (UL) multi-user multiple-input multiple-output (MU-MIMO), low density signature (LDS). 
     SUMMARY OF THE DISCLOSURE 
     Example embodiments of the present disclosure which provide a system and method for scalable digital communications with adaptive system parameters. 
     In accordance with an example embodiment of the present disclosure, a method for operating an adapting device is provided. The method includes selecting, by the adapting device, a first access mode out of a plurality of access modes for a first transmission between a first communications device and a second communications device, wherein the selection of the first access mode is made in accordance with an access mode criterion, and at least one of communications system information, and user equipment information. The method also includes determining, by the adapting device, sparse code multiple access (SCMA) parameters from the first access mode in accordance with a SCMA parameter mapping rule, and providing, by the adapting device, information about the first access mode to at least one of the first communications device and the second communications device. 
     In accordance with another example embodiment of the present disclosure, a method for operating a first device is provided. The method includes sending, by the first device, user equipment information to a second device, wherein the user equipment information comprises at least one of user equipment requirements and user equipment capability, and receiving, by the first device, information about sparse code multiple access (SCMA) parameters related to an access mode for a transmission between the first device and a third device, wherein the access mode is selected out of a plurality of access modes in accordance with an access mode criterion, and at least one of the user equipment information and communications system information. The method also includes communicating, by the first device, with the third device in accordance with the access mode. 
     In accordance with another example embodiment of the present disclosure, an adapting device is provided. The adapting device includes a processor. The processor selects a first access mode out of a plurality of access modes for a first transmission between a first communications device and a second communications device, wherein the selection of the first access mode is made in accordance with an access mode criterion, and at least one of communications system information, and user equipment information. The processor also determines sparse code multiple access (SCMA) parameters from the first access mode in accordance with a SCMA parameter mapping rule, and provides information about the first access mode to at least one of the first communications device and the second communications device. 
     In accordance with another example embodiment of the present disclosure, a user equipment is provided. The user equipment includes a transmitter, a receiver, and a processor operatively coupled to the transmitter and to the receiver. The transmitter sends user equipment information to a first communications device, wherein the user equipment information comprises at least one of user equipment requirements and user equipment capability. The receiver receives information about sparse code multiple access (SCMA) parameters related to an access mode for a transmission between the user equipment and a second communications device, wherein the access mode is selected out of a plurality of access modes in accordance with an access mode criterion, and at least one of the user equipment information and communications system information. The processor communicates with the second communications device in accordance with the access mode. 
     One advantage of an embodiment is that access modes may be adapted to meet access mode criteria, as well as requirements and/or capabilities of the communications system and UE. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawing, in which: 
         FIG. 1  illustrates an example communications system according to example embodiments described herein; 
         FIG. 2  illustrates an example SCMA multiplexing scheme for encoding data according to example embodiments described herein; 
         FIGS. 3 a  and 3 b    illustrate example plots of SCMA system parameters highlighting complexity, multiplexing, spectral efficiency, and link-budget trade-off according to example embodiments described herein; 
         FIGS. 4 a , 4 b , and 4 c    illustrate example plots of SCMA system parameters highlighting complexity, multiplexing, spectral efficiency, and link-budget trade-off if overloading is capped to control complexity according to example embodiments described herein; 
         FIG. 5  illustrates an example high-level view of an example adapting device according to example embodiments described herein; 
         FIG. 6 a    illustrates an example flow diagram of example operations occurring in an adapting device as the adapting device adaptively adjusts an access mode of a communications system (or a part thereof) according to example embodiments described herein; 
         FIG. 6 b    illustrates an example flow diagram of example operations occurring in a UE as the UE communicates according to example embodiments described herein; 
         FIG. 7  illustrates an example graphical mapping rule for downlink access mode selection according to example embodiments described herein; 
         FIG. 8  illustrates an example graphical mapping rule for uplink access mode selection according to example embodiments described herein; 
         FIG. 9  illustrates an example communications device according to example embodiments described herein; and 
         FIG. 10  illustrates an example communications device according to example embodiments described herein. 
     
    
    
     DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS 
     The operating of the current example embodiments and the structure thereof are discussed in detail below. It should be appreciated, however, that the present disclosure provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific structures of the disclosure and ways to operate the disclosure, and do not limit the scope of the disclosure. 
     One embodiment of the disclosure relates to scalable digital communications with adaptive system parameters. For example, an adapting device receives access mode criteria for a first communications channel between a communications controller and a user equipment, selects a first access mode in accordance with a set of mapping rules to meet the access mode criteria, and provides information about the first access mode to the communications controller and the user equipment. 
     The present disclosure will be described with respect to example embodiments in a specific context, namely SCMA communications systems that adaptively adjust their radio access mode for different access mode criteria. The disclosure may be applied to standards compliant communications systems, and non-standards compliant communications systems, that adaptively adjust their radio access mode for different access mode criteria. 
     In SCMA, data is spread over multiple time-frequency tones of OFDMA resources through multi-dimensional codewords. Sparsity of codewords helps to reduce the complexity of joint detection of multiplexed SCMA layers by using message passing algorithm (MPA). In general, each layer of SCMA has its specific codebook set. Low density spreading (LDS) is a special case of SCMA. LDS as a form of multi-carrier CDMA (MC-CDMA) is used for multiplexing different layers of data. As opposed to SCMA with multi-dimensional codewords, LDS uses repetitions of the same (QAM) symbol on layer-specific nonzero position in time or frequency. As an example, in LDS-orthogonal frequency division multiplexing (LDS-OFDM) a constellation point is repeated (with some possible phase rotations) over nonzero frequency tones of a LDS block. The shaping gain of multi-dimensional constellations is one of the advantages of SCMA over LDS. The gain is potentially high for higher order modulations where the repletion coding of LDS shows a large loss and poor performance. 
     SCMA is an encoding technique that encodes data streams, such as binary data streams, or in general, M-ary data streams, where M is an integer number greater than or equal to 2, into multidimensional codewords. SCMA directly encodes the data stream into multidimensional codewords and circumvents quadrature amplitude modulation (QAM) symbol mapping, which may lead to coding gain over conventional CDMA (and LDS) encoding. Notably, SCMA encoding techniques convey data streams using a multidimensional codeword rather than a QAM symbol. 
     Additionally, SCMA encoding provides multiple access through the use of different codebooks for different multiplexed layers, as opposed to the use of different spreading sequences for difference multiplexed layers, e.g., a LDS signatures in LDS, as is common in conventional CDMA encoding. Furthermore, SCMA encoding typically uses codebooks with sparse codewords that enable receivers to use low complexity algorithms, such as message passing algorithms (MPA), to detect respective codewords from combined codewords received by the receiver, thereby reducing processing complexity in the receivers. 
       FIG. 1  illustrates an example communications system  100 . Communications system  100  may support SCMA communications. Communications system  100  may include an evolved NodeB (eNB)  105  operating as a communications controller. Communications system  100  may also include user equipment (UE), such as UE  110 , UE  112 , and UE  114 . eNB  105  may include multiple transmit antennas and multiple receive antennas to facilitate MIMO operation, wherein a single eNB may simultaneously transmit multiple data streams to multiple users, a single user also with multiple receive antennas, or a combination thereof. Similarly, the UEs may include multiple transmit antennas and multiple receive antennas to support MIMO operation. In general, an eNB may also be referred to as a communications controller, a NodeB, a base station, a controller, and the like. Similarly, a UE may also be referred to as a mobile station, a mobile, a terminal, a user, a subscriber, and the like. Communications system  100  may also include a relay node (RN)  118  that is capable of utilizing a portion of resources of eNB  105  to help improve coverage and/or overall performance of communications system  100 . 
     An adapting device  120  may adapt access modes for communications system  100  or a portion thereof. Adapting device  120  may adjust communications system parameters of communications system  100  or a portion thereof to meet access mode criteria to provide an access mode for devices in communications system  100 . A detailed discussion of adapting device  120  is presented below. It is noted that although shown in  FIG. 1  as being a single stand-alone device, in other example embodiments, there may be multiple adapting devices, each responsible for a different part of a communications system. Alternatively, adapting device  120  may be co-located in other devices in communications system  100 . As an example, some or all of the eNBs in communications system  100  may include adapting devices. 
     While it is understood that communications systems may employ multiple eNBs capable of communicating with a number of devices, only one eNB, one RN, an adapting device, and a number of UEs are illustrated for simplicity. 
     SCMA-OFDM is a code-domain multiplexing scheme over multicarrier modulation in which the spreading codebooks are sparse and hence detection can be made simpler. Spreading factor, sparsity of codebooks, and number of the maximum SCMA multiplexed layers are communications system parameters indicating the flexibility of the SCMA waveform. 
       FIG. 2  illustrates an example SCMA multiplexing scheme  200  for encoding data. As shown in  FIG. 2 , SCMA multiplexing scheme  200  may utilize a plurality of codebooks, such as codebook  210 , codebook  220 , codebook  230 , codebook  240 , codebook  250 , and codebook  260 . Each codebook of the plurality of codebooks is assigned to a different multiplexed layer. Each codebook includes a plurality of multidimensional codewords (or spreading sequences). It is noted that in LDS, the multidimensional codewords are low density sequence signatures. More specifically, codebook  210  includes codewords  211 - 214 , codebook  220  includes codewords  221 - 224 , codebook  230  includes codewords  231 - 234 , codebook  240  includes codewords  241 - 244 , codebook  250  includes codewords  251 - 254 , and codebook  260  includes codewords  261 - 264 . 
     Each codeword of a respective codebook may be mapped to a different data, e.g., binary, value. As an illustrative example, codewords  211 ,  221 ,  231 ,  241 ,  251 , and  261  are mapped to binary value ‘00’, the codewords  212 ,  222 ,  232 ,  242 ,  252 , and  262  are mapped to the binary value ‘01’, the codewords  213 ,  223 ,  233 ,  243 ,  253 , and  263  are mapped to the binary value ‘10’, and the codewords  214 ,  224 ,  234 ,  244 ,  254 , and  264  are mapped to the binary value ‘11’. It is noted that although the codebooks in  FIG. 2  are depicted as having four codewords each, SCMA codebooks in general may have any number of codewords. As an example, SCMA codebooks may have 8 codewords (e.g., mapped to binary values ‘000’ . . . ‘111’), 16 codewords (e.g., mapped to binary values ‘0000’ . . . ‘1111’), or more. 
     As shown in  FIG. 2 , different codewords are selected from various codebooks  210 ,  220 ,  230 ,  240 ,  250 , and  260  depending on the binary data being transmitted over the multiplexed layer. In this example, codeword  214  is selected from codebook  210  because the binary value ‘11’ is being transmitted over the first multiplexed layer, codeword  222  is selected from codebook  220  because the binary value ‘01’ is being transmitted over the second multiplexed layer, codeword  233  is selected from codebook  230  because the binary value ‘10’ is being transmitted over the third multiplexed layer, codeword  242  is selected from codebook  240  because the binary value ‘01’ is being transmitted over the fourth multiplexed layer, codeword  252  is selected from codebook  250  because the binary value ‘01’ is being transmitted over the fifth multiplexed layer, and codeword  264  is selected from codebook  260  because the binary value ‘11’ is being transmitted over the sixth multiplexed layer. Codewords  214 ,  222 ,  233 ,  242 ,  252 , and  264  may then be multiplexed together to form multiplexed data stream  280 , which is transmitted over shared resources of a network. Notably, codewords  214 ,  222 ,  233 ,  242 ,  252 , and  264  are sparse codewords, and therefore can be identified upon reception of multiplexed data stream  280  using a low complexity algorithm, such as a message passing algorithm (MPA) or a turbo decoder. 
     According to an example embodiment, an access mode of a communications system (or of a portion of a communications system) is be specified, at least in part, by communications system parameters. The communications system parameters, when set to specific values, may determine how the communications system communicates with UE within it. As an illustrative example, access modes in a SCMA communications system may be specified by a number of communications systems parameters, including: 
     M—a number of codewords in a SCMA codebook. 
     K—a spreading factor. 
     J—a maximum number of layers (or codebooks and/or signatures). It is noted that the number of signatures may exceed this value if signature reuse is allowed, such as in an uplink. 
     N—a number of nonzero elements of each codeword. 
     d f —a maximum number of codewords colliding at a tone. 
     λ—an overloading factor. 
     l—a number of overlapping elements of any two distinct codebooks 
     Example values of the communications system parameters include: 
     
       
         
           
             J 
             = 
             
               
                 ( 
                 
                   
                     
                       K 
                     
                   
                   
                     
                       N 
                     
                   
                 
                 ) 
               
               . 
             
           
         
       
     
                 d   f     =       (           K   -   1               N   -   1           )     =     JN   K         ,         
which determines the complexity of the MPA algorithm ∝M d     f   .
 
     
       
         
           
             λ 
             = 
             
               
                 J 
                 K 
               
               = 
               
                 
                   
                     d 
                     f 
                   
                   N 
                 
                 . 
               
             
           
         
       
     
     max(0,2N−K)≤l≤N−1. 
     An example SCMA communications system design example is as follows: 
               N   =       2   ⁢           ⁢   J     =       (         K           N         )     =       (         K           2         )     =       K   ⁡     (     K   -   1     )       2             ;         
if K=4, then J=6.
 
                 d   f     =       (           K   -   1               N   -   1           )     =       (           K   -   1             1         )     =     K   -   1           ,       ∀   J     ;           
if K=4, then d f =3.
 
               λ   =       J   K     =       K   -   1     2         ;         
if K=4, then λ=4.
 
     0≤l≤1 if K=4, which means that the codewords are either totally orthogonal with no overlap (l=0) or they collide only over one non-zero element (l=1). Then, a factor graph of an SCMA codebook may be of the form: 
     
       
         
           
             
               [ 
               
                 
                   
                     1 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     0 
                   
                 
                 
                   
                     1 
                   
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                   
                     0 
                   
                 
                 
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     1 
                   
                 
                 
                   
                     0 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     0 
                   
                   
                     1 
                   
                   
                     1 
                   
                 
               
               ] 
             
             . 
           
         
       
     
     According to an example embodiment, the communications systems parameters of a communications system may be set so that the access mode of the communications system emulates that of another communications system. As an illustrative example, a SCMA communications system may be set to emulate an orthogonal frequency division multiple access (OFDMA) communications system if communications system parameters K is set to 1 (K=1) and N is set to 1 (N=1). As another illustrative example, a SCMA communications system may be set to emulate a CDMA communications system if communications system parameters N and K are set to be equal (N=K) and non-zero elements are not allowed in the codebooks. The codebooks may be constructed over quadrature amplitude modulation (QAM) symbols with CDMA spreading signatures. 
       FIGS. 3 a  and 3 b    illustrate example plots of SCMA complexity, multiplexing, spectral efficiency, and link-budget trade-off. As shown in  FIG. 3 b   , for a given N and K, complexity can be capped by limiting the number of multiplexed layers. The cost for doing so may be a lower overloading factor, as discussed below. 
       FIGS. 4 a , 4 b , and 4 c    illustrate example plots of SCMA if overloading is capped to control complexity. As an example, complexity may be limited by reducing the number of overlaid codewords. 
     According to an example embodiment, a SCMA communications system is used to implement flexible and scalable access techniques that compromise amongst criteria, e.g., spectral efficiency, coverage, detection complexity, connectivity, link budget, and the like, to support different application scenarios and access modes under a single communications system with a smooth switching mechanism. The implementation is achieved by selecting an access mode in accordance with access mode criteria, communications system information, and UE information, and the selected access mode is implemented by setting SCMA parameters based on mapping rules and the selected access mode. 
     According to an example embodiment, a SCMA communications system optimizes access modes for different application scenarios and different receive categories. The optimization of the access modes is achieved by adjusting SCMA parameters. As an example, an access mode adaptation mechanism, having predefined access modes for both UL and DL, selects a best access mode in accordance with access mode criteria, such as applications, requirements, network conditions, and the like. Additionally, signaling support is provided to switch between different access modes. The SCMA communications system is adaptively adjusted according to access mode criteria. There is low signaling overhead to switch the access mode and/or parameters in response to the access mode criteria. 
     In general, SCMA-OFDM is a flexible waveform that can facilitate different access modes, including existing ones such as OFDMA, LDS-OFDM, UL MU-MIMO, and MC-CDMA. SCMA-OFDM also is a promising waveform/access technology for proposed 5G standards and beyond. The access modes may be applied to an individual transmission, a plurality of transmissions, a single communications channel (uplink, downlink, or uplink and downlink), or a plurality of communications channels. 
       FIG. 5  illustrates a high-level view of an example adapting device  500 . Adapting device  500  may perform access mode/UE criteria processing  505  on access mode criteria, which may include communications system requirements, and communications system capabilities, as well as UE criteria, which may include UE capabilities and UE requirements. The processed access mode criteria and/or the UE criteria may be provided to an adaptive framework  510  to select an access mode  515 . Examples of access mode criteria and/or UE criteria may include link-budget, coverage, connectivity, throughput, multiplexing gain, processing capabilities, and the like. Adaptive framework  510  may utilize mapping rules to select values for communications system parameters (such as J, N, K, d f , λ, multiplexing technique, and the like) to emulate an access mode to meet the access mode criteria and/or the UE criteria. Examples of access modes include OFDMA, NOMA, single UE SCMA (SU-SCMA), multi-user SCMA (MU-SCMA), multi-carrier CDMA (MC-CDMA), low density signature (LDS), and the like. 
     Table 1 below illustrates example predefined downlink (DL) multiple access modes, in which J is a maximum number of signatures/codebooks, K is a spreading factor, and N≤K is a number of non-zero elements in each signature/codeword. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Example downlink multiple access modes. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Codebook/ 
                   
                 Typical 
               
               
                 Scenario 
                 J 
                 K 
                 N 
                 Signature 
                 Comment 
                 Applications 
               
               
                   
               
               
                 SCMA- 
                 J ≤ f 
                 K &gt; N 
                 N &gt;&gt; 1 
                 SCMA 
                 large processing 
                 Link budget and 
               
               
                 mode1 
                 (N, K) 
                   
                   
                 multidimensional 
                 gain due to large 
                 coverage 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 effective 
                 improvement 
               
               
                   
                   
                   
                   
                 LDS signatures 
                 spreading factor 
               
               
                 SCMA- 
                 Moderate 
                 K &gt; N 
                 N &gt; 1 
                 SCMA 
                 User pairing 
                 Capacity 
               
               
                 Mode2 
                   
                   
                   
                 multidimensional 
                 with power 
                 enhancement or 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 allocation, Low 
                 interference 
               
               
                   
                   
                   
                   
                 LDS signatures 
                 to moderate 
                 whitening 
               
               
                   
                   
                   
                   
                   
                 overloading 
               
               
                   
                   
                   
                   
                   
                 factor 
               
               
                 SCMA- 
                 Large 
                 K &gt; N 
                 N &gt; 1 
                 SCMA 
                 Large 
                 Scheduling free 
               
               
                 Mode3 
                   
                   
                   
                 multidimensional 
                 overloading 
                 small packet 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 factor 
                 transmission for 
               
               
                   
                   
                   
                   
                 LDS signatures 
                   
                 massive 
               
               
                   
                   
                   
                   
                   
                   
                 connectivity 
               
               
                 OFDMA 
                 1 
                 1 
                 1 
                 — 
                 Non- 
                 legacy UEs or UE 
               
               
                   
                   
                   
                   
                   
                 superposition 
                 with no SCMA 
               
               
                   
                   
                   
                   
                   
                 type 
                 decoding capability 
               
               
                   
                   
                   
                   
                   
                 transmission 
                 might fall into this 
               
               
                   
                   
                   
                   
                   
                   
                 category 
               
               
                 DL-NOMA 
                 J &gt; 1 
                 1 
                 1 
                 — 
                 User 
                 DL user paring and 
               
               
                   
                 (reuse) 
                   
                   
                   
                 superposition 
                 open loop multiple 
               
               
                   
                   
                   
                   
                   
                 with power 
                 access for UEs with 
               
               
                   
                   
                   
                   
                   
                 sharing 
                 SIC reception 
               
               
                   
                   
                   
                   
                   
                   
                 capability 
               
               
                 MC-CDMA 
                 J ≤ K 
                 K = N 
                 N &gt; 1 
                 Orthogonal or 
                 CDMA 
                 Coverage/link 
               
               
                   
                   
                   
                   
                 non-orthogonal 
                 signatures 
                 budget 
               
               
                   
                   
                   
                   
                 CDMA 
                 allocated to one 
                 improvement with 
               
               
                   
                   
                   
                   
                 signatures 
                 or multiple UEs 
                 under-loading 
               
               
                   
               
            
           
         
       
     
     Table 2 below illustrates predefined uplink (UL) multiple access modes in which J is a maximum number of signatures/codebooks, K is a spreading factor, and N≤K is a number of non-zero elements in each signature/codeword. 
     
       
         
           
               
             
               
                 TABLE 2 
               
             
            
               
                   
               
               
                 Example uplink multiple access modes. 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                   
                   
                 Codebook/ 
                   
                 Typical 
               
               
                 Scenario 
                 J 
                 K 
                 N 
                 Signature 
                 Comment 
                 Applications 
               
               
                   
               
               
                 SCMA- 
                 J ≤ f 
                 K &gt; N 
                 N &gt;&gt; 1 
                 SCMA 
                 large processing 
                 Link budget 
               
               
                 Mode1 
                 (N, K) 
                   
                   
                 multidimensional 
                 gain due to large 
                 and coverage 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 effective 
                 improvement 
               
               
                   
                   
                   
                   
                 LDS signatures 
                 spreading factor 
               
               
                 SCMA- 
                 Moderate 
                 K &gt; N 
                 N &gt; 1 
                 SCMA 
                 Moderate 
                 Interference 
               
               
                 Mode-2 
                   
                   
                   
                 multidimensional 
                 overloading 
                 whitening and 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 factor 
                 multi-user 
               
               
                   
                   
                   
                   
                 LDS signatures 
                   
                 channel 
               
               
                   
                   
                   
                   
                   
                   
                 diversity for 
               
               
                   
                   
                   
                   
                   
                   
                 better capacity 
               
               
                 SCMA- 
                 Large 
                 K &gt; N 
                 N &gt; 1 
                 SCMA 
                 Large 
                 Contention 
               
               
                 Mode-3 
                   
                   
                   
                 multidimensional 
                 overloading 
                 based small 
               
               
                   
                   
                   
                   
                 codebooks, or 
                 factor 
                 packet 
               
               
                   
                   
                   
                   
                 LDS signatures 
                   
                 transmission for 
               
               
                   
                   
                   
                   
                   
                   
                 massive 
               
               
                   
                   
                   
                   
                   
                   
                 connectivity 
               
               
                 OFDMA, 
                 1 
                 1 
                 1 
                 — 
                 Non- 
                 Legacy UEs 
               
               
                 SC-FDMA 
                   
                   
                   
                   
                 superposition 
                 and BSs with 
               
               
                   
                   
                   
                   
                   
                 type 
                 no SCMA 
               
               
                   
                   
                   
                   
                   
                 transmission 
                 decoding 
               
               
                   
                   
                   
                   
                   
                   
                 capabilities 
               
               
                   
                   
                   
                   
                   
                   
                 might fall into 
               
               
                   
                   
                   
                   
                   
                   
                 this category. 
               
               
                 UL-NOMA 
                 J &gt; 1 
                 1 
                 1 
                 — 
                 Superposition 
                 UL multi-user 
               
               
                   
                 (reuse) 
                   
                   
                   
                 type 
                 access with 
               
               
                   
                   
                   
                   
                   
                 transmission 
                 non-linear 
               
               
                   
                   
                   
                   
                   
                   
                 reception 
               
               
                   
                   
                   
                   
                   
                   
                 capability (SIC) 
               
               
                   
                   
                   
                   
                   
                   
                 at BS 
               
               
                 MC-CDMA 
                 J ≤ K 
                 K = N 
                 N &gt; 1 
                 Orthogonal or 
                 CDMA 
                 For 
               
               
                   
                   
                   
                   
                 non-orthogonal 
                 signatures 
                 coverage/link 
               
               
                   
                   
                   
                   
                 CDMA 
                 allocated to one 
                 budget 
               
               
                   
                   
                   
                   
                 signatures 
                 or multiple UEs 
                 improvement to 
               
               
                   
                   
                   
                   
                   
                   
                 get processing 
               
               
                   
                   
                   
                   
                   
                   
                 gain 
               
               
                   
               
            
           
         
       
     
       FIG. 6 a    illustrates a flow diagram of example operations  600  occurring in an adapting device as the adapting device adaptively adjusts an access mode of a communications system (or a part thereof). Operations  600  may be indicative of operations occurring in an adapting device, such as a stand-alone adapting device or a co-located adapting device located in a network device, such as an eNB, in the communications system, as the adapting device adaptively adjusts the access mode of the communications system (or a part thereof). 
     Operations  600  may begin with the adapting device receiving communications system information (block  605 ). As discussed previously, the communications system information may include information about applications, requirements, network conditions, and the like. Examples of the communications system information may include communications system requirements, and/or communications system capabilities, and the like. The adapting device may receive the communications system information from controller(s) or eNB(s) in the communications system, or another network entity in the communications system that maintains the access mode criteria. 
     The adapting device may receive UE information (block  607 ). Examples of UE information may include UE capabilities, UE requirements, and the like. The adapting device may receive the UE information from UE(s) that it is serving, UE(s) in the communications system, a network entity in the communications system that maintains the UE criteria. 
     The adapting device may receive communications system parameters (block  610 ). The communications system parameters may include J, N, K, d f , λ, multiplexing technique, and the like. The adapting device may have a default version of the communications system parameters provided to it at system start up, for example, and then as it (as well as potentially other adapting devices) adjusts the communications system parameters, the adapting device may receive (or provide) updates for the communications system parameters. Depending on a granularity of the adaptation (e.g., communications system wide, eNB wide, cell wide, eNB-to-UE type wide, eNB-to-UE pairing wide), the adapting device may store different versions of the communications system parameters for the different levels of granularity and devices involved. 
     The adapting device may receive access mode criteria (block  612 ). The access mode criteria may include link-budget, coverage, connectivity, throughput, multiplexing gain, processing capabilities, and the like. According to an example embodiment, the access mode criteria may be associated with a transmission(s) or a communications channel. The access mode criteria may be associated with a single transmission over a single communications channel, a plurality of transmissions over a single communications channel, a plurality of transmissions over a plurality of communications channels, a single communications channel (such as a downlink communications channel between an eNB and a UE or an uplink communications channel between a UE and an eNB), or a plurality of communications channels (such as both downlink and uplink communications channels between an eNB and a UE, uplink and/or downlink communications channels between an eNB and a type (or group) of UEs, uplink and/or downlink communications channels between a group of eNBs and a type (or group) of UEs, uplink and/or downlink communications channels between all eNBs and a type (or group) of UEs, uplink and/or downlink communications channels between all eNBs and all UEs, and the like). 
     The adapting device may receive mapping rules (block  615 ). The mapping rules may specify how the communications system parameter(s), e.g., SCMA parameter(s), are affected by the access mode criteria, the communications system information, and the UE information. The mapping rules may be associated with transmissions for downlink communications channels, uplink communications channels, or both downlink and uplink communications channels. The mapping rules may differ for different types or groups of UEs. The mapping rules may differ for one eNB or multiple eNBs. The mapping rules may also specify how to change the communications system parameter(s) and potentially, by how much. As an illustrative example, parameter K may be impacted by UE that have no SCMA capability, while parameters K and J may be impacted by a need to support large number of overlaid transmissions in a massive connectivity situation. Table 3 below illustrates example mapping rules. 
     
       
         
           
               
             
               
                 TABLE 3 
               
             
            
               
                   
               
               
                 Example mapping rules. 
               
            
           
           
               
               
               
               
            
               
                   
                   
                 Acceptable 
                   
               
               
                 No. 
                 Requirements/Capabilities 
                 access mode 
                 System parameters 
               
               
                   
               
            
           
           
               
               
               
               
            
               
                 1 
                 Legacy users with no capabilities to 
                 OFDMA 
                 K = 1 and no super 
               
               
                   
                 handle spreading in any forms as well 
                 transmission 
                 positioning 
               
               
                   
                 as no SIC reception capability 
                 mode 
               
               
                 2 
                 Legacy users with no capability to 
                 OFDMA 
                 K = 1 and UE pairing 
               
               
                   
                 handle spreading in any forms but with 
                 transmission 
               
               
                   
                 SIC reception capability 
                 mode and user 
               
               
                   
                   
                 pairing (NOMA) 
               
               
                 3 
                 User can support spreading with linear 
                 MC-CDMA 
                 K &gt; 1 but no overloading 
               
               
                   
                 reception techniques 
               
               
                 4 
                 This MC-CDMA user needs larger 
                   
                 Increase K with limited J 
               
               
                   
                 coverage and link budget 
               
               
                 5 
                 More MC-CDMA users need to access 
                   
                 Increase K and J 
               
               
                   
                 the system to support massive 
                   
                 considering complexity 
               
               
                   
                 connectivity for example for 
                   
                 capability of receivers 
               
               
                   
                 contention-based transmission 
               
               
                 6 
                 User can support SCMA spreading 
                 SCMA-OFDM 
                 SCMA codebooks with 
               
               
                   
                 with advanced non-linear reception 
                   
                 appropriate K, J, and d f   
               
               
                   
                 capabilities 
               
               
                 7 
                 This SCMA user needs larger coverage 
                   
                 Increase N only or both N 
               
               
                   
                 and link budget 
                   
                 and K while limit J and 
               
               
                   
                   
                   
                 consider complexity 
               
               
                   
                   
                   
                 impacts. Increasing N 
               
               
                   
                   
                   
                 improves processing and 
               
               
                   
                   
                   
                 multi-dimensional gain 
               
               
                   
                   
                   
                 of SCMA codebooks. 
               
               
                 8 
                 More SCMA users need to access the 
                   
                 Increase K and J 
               
               
                   
                 system to support massive connectivity 
                   
                 considering complexity 
               
               
                   
                 for example for contention-based 
                   
                 capability of receivers by 
               
               
                   
                 access 
                   
                 controlling N. 
               
               
                 9 
                 Throughput improvement for SCMA 
                   
                 SCMA codebooks rather 
               
               
                   
                 users 
                   
                 than LDS signatures 
               
               
                   
                   
                   
                 Increase N at the expense 
               
               
                   
                   
                   
                 of more complexity 
               
               
                   
                   
                   
                 Allow UE pairing if users 
               
               
                   
                   
                   
                 and network support UE 
               
               
                   
                   
                   
                 pairing access mode 
               
               
                   
                   
                   
                 (MU-SCMA) 
               
               
                 10 
                 SCMA users with low PAPR 
                   
                 Limit bandwidth of 
               
               
                   
                 requirements for example for small 
                   
                 transmission 
               
               
                   
                 packet transmission of UL access or 
                   
                 Use SCMA codebooks 
               
               
                   
                 MTC 
                   
                 providing lower PAPR at 
               
               
                   
                   
                   
                 the expense of possible 
               
               
                   
                   
                   
                 less throughput 
               
               
                   
                   
                   
                 performance 
               
               
                   
                   
                   
                 Reduce N to decrease 
               
               
                   
                   
                   
                 PAPR with careful 
               
               
                   
                   
                   
                 codebook design 
               
               
                   
               
            
           
         
       
     
     The adapting device may select an access mode in accordance with the mapping rules to meet the access mode criteria, the communications system information, and the UE information (block  620 ). The adapting device may select the access mode out of a plurality of access modes. As an illustrative example, the adapting device may have a list of the plurality of access modes and the adapting device may select the access mode out of the plurality of access modes. The adapting device may select the access mode from the plurality of access modes by considering the access mode criteria, the communications system information, and the UE information. As an illustrative example, if the UE is a legacy UE with no SCMA capability, the adapting device may select OFDMA as the access mode. Similarly, if the UE is SCMA capable, the adapting device may consider access mode criteria, such as link-budget, coverage, and the like, to select the access mode. Detailed discussions of example access mode selection techniques are presented below. 
     The adapting device may determine the communications system parameters, e.g., SCMA parameters, from the selected access mode in accordance with the mapping rules (block  622 ). The adapting device may use mapping rules, such as the example mapping rules shown in Table 3, to determine values for communications system parameters from the selected access mode. As an illustrative example, if the selected access mode for a specified type of UE is to increase the coverage area for the UE, the adapting device may use mapping rule #7 shown in Table 3 and increase parameter N only or both parameters N and K while limiting parameter J and consider complexity impacts, since increasing parameter N improves processing and multi-dimensional gain of SCMA codebooks. 
     The adapting device may signal the communications system parameters (block  625 ). The adapting device may send the communications system parameters to devices impacted by the access mode change. As an illustrative example, if the access mode change is for the communications system as a whole, the adapting device may send the communications system parameters to the eNBs in the communications system, which may provide the communications system parameters to the UEs that they serve. As another illustrative example, if the access mode change is for an eNB, the adapting device may send the communications system parameters to the eNB and the eNB may provide the communications system parameters to the UE that it serves. As yet another illustrative example, if the access mode change is for a single cell and UE type, the adapting device may send the communications system parameters to an eNB associated with the cell and the eNB may provide the communications system parameters to the UEs that it is serving that are of same UE type. As yet another illustrative example, if the access mode change is for a single cell and a single UE, the adapting device may send the communications system parameters to an eNB associated with the cell and the eNB may provide the communications system parameters to the UE. According to an example embodiment, there may be a pre-defined plurality of access modes and the adapting device may simply send an indicator, e.g., a number that corresponds to the selected access mode. 
       FIG. 6 b    illustrates an example flow diagram of example operations  650  occurring in a UE as the UE communicates. Operations  650  may be indicative of operations occurring in a UE, such as UE  110 , UE  112 , and UE  114 , as the UE communicates. 
     Operations  650  may begin with the UE sending UE information (block  655 ). The UE may send the UE information, including UE capabilities and/or requirements, and the like. The UE information may be sent to an eNB serving the UE or an adapting device that is performing access mode selection. The UE may receive communications system parameters (block  660 ). The UE may receive the communications system parameters from the eNB or the adapting device, whichever is performing access mode selection. The communications system parameters may be sent to the UE as well as other devices that are impacted by the access mode selection. According to an example embodiment, there may be a pre-defined plurality of access modes and the UE may receive an indicator, e.g., a number that corresponds to the selected access mode. The UE may communicate using the communications system parameters (block  665 ). 
       FIG. 7  illustrates an example graphical representation of a mapping rule  700  for downlink access mode selection. The representation of mapping rule  700  shown in  FIG. 7  may illustrate graphically the selection of an access mode for a downlink. The adapting device may select OFDMA  705  for the downlink if the UE(s) are legacy UEs or if SCMA is not supported. Then, if coverage and/or link budget increase is an access mode criterion, the adapting device may select MC-CDMA  710 . If capacity increase is access mode criterion and the UE(s) has successive interference cancellation capability, the adapting device may select DL-NOMA  715 . 
     The adapting device may select SCMA  720  if the UE(s) and eNB(s) are SCMA capable. Then if link-budget and coverage improvement are access mode criterion, the adapting device may select mode-1 SCMA  725 . If interference whitening and multi-user pairing for better capacity are access mode criterion, the adapting device may select mode-2 SCMA  730 , and if scheduling free small packet transmission for massive connectivity is the access mode criteria, the adapting device may select mode-3 SCMA  735 . 
       FIG. 8  illustrates an example graphical representation of a mapping rule  800  for uplink access mode selection. The representation of mapping rule  800  shown in  FIG. 8  may illustrate graphically the selection of an access mode for an uplink. The adapting device may select OFDMA or SC-FDMA  805  for the uplink if the UE(s) are legacy UEs and if SCMA is not supported at the eNB(s). Then, if random access with moderate connectivity or capacity enhancement if eNB has SIC reception, the adapting device may select UL-NOMA  810 . If coverage and/or link budget increase are access mode criterion, the adapting device may select MC-CDMA  815 . 
     The adapting device may select SCMA  820  if the UE(s) and eNB(s) are SCMA capable. Then, if link-budget and coverage improvement are access mode criterion, the adapting device may select mode-1 SCMA  825 . If interference whitening and multi-user pairing for better capacity are access mode criterion, the adapting device may select mode-2 SCMA  830 , and if scheduling free small packet transmission for massive connectivity is the access mode criteria, the adapting device may select mode-3 SCMA  835 . 
       FIG. 9  illustrates an example first communications device  900 . Communications device  900  may be an implementation of an adapting device, such as a stand-alone device, or a co-located device located in an eNB, a communications controller, a base station, a controller, and the like. Communications device  900  may be used to implement various ones of the embodiments discussed herein. As shown in  FIG. 9 , a transmitter  905  is configured to transmit packets, communications system parameters, and the like. Communications device  900  also includes a receiver  910  that is configured to receive packets, access mode criteria, communications system parameters, mapping rules, and the like. 
     A criteria processing unit  920  is configured to process access mode criteria and communications system information, such as communications system requirements, communications system capabilities link-budget, coverage, connectivity, throughput, multiplexing gain, and the like, to help adapt an access mode. Criteria processing unit  920  is configured to process UE information to help adapt the access mode. A parameter processing unit  922  is configured to receive processed access mode criteria, communications system information, UE information, and communications system parameters, and to select an access mode in accordance with the access mode criteria, the communications system information, and the UE information. Parameter processing unit  922  is configured to set the communications system parameters in accordance with the mapping rules and the selected access mode. A memory  930  is configured to store packets, access mode criteria, communications system information, UE information, communications system parameters, mapping rules, and the like. 
     The elements of communications device  900  may be implemented as specific hardware logic blocks. In an alternative, the elements of communications device  900  may be implemented as software executing in a processor, controller, application specific integrated circuit, or so on. In yet another alternative, the elements of communications device  900  may be implemented as a combination of software and/or hardware. 
     As an example, receiver  910  and transmitter  905  may be implemented as a specific hardware block, while criteria processing unit  920  and parameter processing unit  922  may be software modules executing in a microprocessor (such as processor  915 ) or a custom circuit or a custom compiled logic array of a field programmable logic array. Criteria processing unit  920  and parameter processing unit  922  may be modules stored in memory  930 . 
       FIG. 10  illustrates an example second communications device  1000 . Communications device  1000  may be an implementation of a receiving device, such as a user equipment, an eNB, and the like. Communications device  1000  may be used to implement various ones of the embodiments discussed herein. As shown in  FIG. 10 , a transmitter  1005  is configured to transmit packets, access mode criteria, mapping rules, and the like. Communications device  1000  also includes a receiver  1010  that is configured to receive packets, communications system parameters, and the like. 
     A criteria processing unit  1020  is configured to process access mode criteria and communications system information, such as communications system requirements, communications system capabilities link-budget, coverage, connectivity, throughput, multiplexing gain, and the like, and UE information, such as UE capabilities, UE requirements, and the like, to help adapt an access mode. A parameter processing unit  1022  is configured to receive information, such as communications system parameters, associated with an access mode. A memory  1030  is configured to store packets, access mode criteria, communications system information, UE information, communications system parameters, and the like. 
     The elements of communications device  1000  may be implemented as specific hardware logic blocks. In an alternative, the elements of communications device  1000  may be implemented as software executing in a processor, controller, application specific integrated circuit, or so on. In yet another alternative, the elements of communications device  1000  may be implemented as a combination of software and/or hardware. 
     As an example, receiver  1010  and transmitter  1005  may be implemented as a specific hardware block, while criteria processing unit  1020  and parameter processing unit  1022  may be software modules executing in a microprocessor (such as processor  1015 ) or a custom circuit or a custom compiled logic array of a field programmable logic array. Criteria processing unit  1020  and parameter processing unit  1022  may be modules stored in memory  1030 . 
     Although the present disclosure and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the disclosure as defined by the appended claims.