A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s> Code domain NOMA <s> Novel low-density signature (LDS) structure is proposed for transmission and detection of symbol-synchronous communication over memoryless Gaussian channel. Given N as the processing gain, under this new arrangement, users' symbols are spread over N chips but virtually only dv < N chips that contain nonzero-values. The spread symbol is then so uniquely interleaved as the sampled, at chip rate, received signal contains the contribution from only dc < K number of users, where K denotes the total number of users in the system. Furthermore, a near-optimum chip-level iterative soft-in-soft-out (SISO) multiuser decoding (MUD), which is based on message passing algorithm (MPA) technique, is proposed to approximate optimum detection by efficiently exploiting the LDS structure. Given beta = K/N as the system loading, our simulation suggested that the proposed system alongside the proposed detection technique, in AWGN channel, can achieve an overall performance that is close to single-user performance, even when the system has 200% loading, i.e., when beta = 2. Its robustness against near-far effect and its performance behavior that is very similar to optimum detection are demonstrated in this paper. In addition, the complexity required for detection is now exponential to dc instead of K as in conventional code division multiple access (CDMA) structure employing optimum multiuser detector. <s> BIB001 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s> Code domain NOMA <s> Internet of things (IoT) is widely expected to be an important scenario in the fifth generation (5G) wireless network. Major challenges of IoT include the low cost of devices, low energy consumption, low latency and the ability to support a large number of simultaneous connections. In this article, a new type of non-orthogonal multiple access scheme called multi-user shared access (MUSA) is proposed to support IoT. MUSA adopts a grant-free access strategy to simplify the access procedure significantly and utilizes advanced code domain non-orthogonal complex spreading to accommodate massive number of users in the same radio resources. A family of complex sequences with short length is chosen as spreading sequence for its ability to enable simple and robust successive interference cancellation at the base station side and cope with high user load. Simulation results show that MUSA can achieve significant gain in user overloading performance compared to orthogonal systems, while incurring much lower control overhead. <s> BIB002 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s> Code domain NOMA <s> Sparse code multiple access (SCMA) is a non- orthogonal codebook (CB) based multiple access scheme, proposed to cope with the heterogeneous and challenging performance requirements for mission critical communication and massive machine-type communication (MTC) in the fifth Generation (5G) wireless system. In this paper, the performance of SCMA has been studied and analyzed, considering the impact of the energy diversity and minimum Euclidean distance of the mother constellation, overloading of the system and the layer specific operators for codebooks generation. An optimized codebooks generation method for four ring star QAM based signaling constellation is proposed. It is demonstrated that by selecting the optimum design parameters, the bit error rate (BER) can be improved. Moreover, an overloading technique is also proposed to enable higher connectivity at lower decoding complexity <s> BIB003 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s> Code domain NOMA <s> Sparse code multiple access (SCMA) is a nonorthogonal codebook based multiple access scheme, proposed to cope with the heterogeneous and challenging performance requirements for mission critical communication and massive machine-type communication in the fifth generation wireless system. In SCMA the codebooks are the main sources of performance improvement, which are generated based on the mother constellation. In this paper, a systematic sub-optimal approach of designing the mother constellation is proposed and a unified metric is derived to obtain the optimum codebooks using a specific mother constellation. It is demonstrated that the new mother constellation outperforms the existing mother constellations in terms of bit error rate (BER) performance. Moreover, it is shown that the optimum codebook obtained based on the unified metric can guarantee the optimum BER performance of the system. <s> BIB004 </s> A Survey: Non-Orthogonal Multiple Access with Compressed Sensing Multiuser Detection for mMTC <s> Code domain NOMA <s> In this paper, pattern division multiple access (PDMA), which is a novel nonorthogonal multiple access scheme, is proposed for fifth-generation (5G) radio networks. The PDMA pattern defines the mapping of transmitted data to a resource group that can consist of time, frequency, and spatial resources or any combination of these resources. The pattern is introduced to differentiate signals of users sharing the same resources, and the pattern is designed with disparate diversity order and sparsity so that PDMA can take the advantage of the joint design of transmitter and receiver to improve system performance while maintaining detection complexity to a reasonable level. System level simulation results show that PDMA can support $\text{six}$ times simultaneous connections than that of conventional and at least $\text{30}\%$ improvement in spectrum efficiency over orthogonal frequency division multiple access. <s> BIB005
In code domain NOMA, user specific codes are used as multiple access signatures to identify different users at the receiver. The number of available resources are less than the total number of users due to which the codes are non-orthogonal to each other. The correlations between the codes of a non-Correlations Fig. 4 : Resource allocation in code domain NOMA: Colours represent different users which are more than the number of resources orthogonal code domain NOMA is shown in Figure 4 by the overlapping parts of the codes. The correlations between the codes increases the probability of errors in detecting the active users at the receiver. However, advanced multiuser detection techniques such as message passing algorithm, minimum mean square error and SIC are used to efficiently recover the transmitted data. The prominent code domain NOMA schemes include sparse code multiple access (SCMA)  BIB003 BIB004 , pattern division multiple access (PDMA) BIB005 , multi-user shared access (MUSA) BIB002 and so on. SCMA and PDMA are codebook based schemes, in which a unique codebook is assigned to each user and message passing algorithm (MPA) BIB001 is used at the receiver for multiuser detection. In MUSA the users are separated by assigning low correlated spreading sequence at the transmitter and SIC is used at the receiver for MUD. All these NOMA schemes enable system overloading and hence facilitates the massive connectivity. However, all the nodes within the vicinity of a base station (BS) are assumed active in these schemes while in fact in mMTC a small fraction of the total nodes is active at a time. Moreover, in mMTC the data packet is of small size, for which a grant free medium access control mechanism is indispensable to reduce the control signaling overhead. 