Sparse code multiple access （SCMA） is a competitive nonorthogonal access scheme for the next mobile communication. As a multiuser sharing system, SCMA adopts message passing algorithm （MPA） for decoding scheme in ...Sparse code multiple access （SCMA） is a competitive nonorthogonal access scheme for the next mobile communication. As a multiuser sharing system, SCMA adopts message passing algorithm （MPA） for decoding scheme in receiver, but its iterative method leads to high computational complexity. Therefore, a serial message passing algorithm based on variable node （VMPA） is proposed in this paper. Making some subtle alterations to message update in original MPA, VMPA can greatly reduce overall computing complexity of decoding scheme. Furthermore, considering that serial structure may increase decoding delay, a novel grouping scheme based sparse matrix is applied to VMPA. Simulation results verify that the new algorithm, termed as grouping VMPA （G-VMPA）, can achieve a better tradeoff between bit error rate （BER） and computing complexity than MPA.展开更多
Sparse code multiple access-based uplink grant-free transmission(SCMA-UGFT)has been proposed to realize ultra reliable and low latency communication(URLLC)in the fifth generation(5 G)system.Without the process of reso...Sparse code multiple access-based uplink grant-free transmission(SCMA-UGFT)has been proposed to realize ultra reliable and low latency communication(URLLC)in the fifth generation(5 G)system.Without the process of resource request and grant,users may collide in the same resource.To compensate the potential user performance decline,resource scheduling becomes a tough issue in the SCMA-UGFT system.This article proposes a duplicated transmission-based resource scheduling(DTBRS)scheme for SCMA-UGFT system by considering the URLLC scenario.Different from the existing schemes,not only one shared basic transmission units(BTUs)are allocated to a user equipment(UE)in the proposed DTBRS scheme for initial transmission to realize the duplicated transmission and to guarantee the transmission reliability.Besides,according to the proposed DTBRS scheme,one or two exclusive BTUs are assigned to a UE for retransmission to avoid the re-collision.At last,each packet is given a lifetime to limit the transmission latency to meet the URLLC latency requirement.The simulation demonstrates that the DTBRS scheme can achieve a better performance than the existing state-of-the-art scheme in terms of the average packet drop rate.展开更多
A SCMA ACO-OFDM downlink visible light communication(VLC)system is proposed.Six users share four spectrum resources,four of which are 4 primary color LED lights.ACO-OFDM technology is used to convert the user’s spars...A SCMA ACO-OFDM downlink visible light communication(VLC)system is proposed.Six users share four spectrum resources,four of which are 4 primary color LED lights.ACO-OFDM technology is used to convert the user’s sparse codebook mapped signal into a positive real value signal that can be carried on the light wave,which can realize high-speed parallel communication.Simulation verifies the feasibility of the system.At the same time,the channel model of visible light communication is constructed,and the signal-to-noise ratio(SNR)and channel gain of the visible light channel are systematically analyzed.Finally,the theoretical bit error rate formula using MPA decoding algorithm under different codebook constellation mapping points is given.Through simulation,it is verified that the theoretical bit error rate formula is basically consistent with the simulation bit error rate formula.展开更多
The sparse code multiple access(SCMA)scheme is a Non-Orthogonal Multiple Access(NOMA)type of scheme that is used to handle the uplink com-ponent of mobile communication in the current generation.A need of the 5G mobil...The sparse code multiple access(SCMA)scheme is a Non-Orthogonal Multiple Access(NOMA)type of scheme that is used to handle the uplink com-ponent of mobile communication in the current generation.A need of the 5G mobile network is the ability to handle more users.To accommodate this,the SCMA allows each user to deploy a variety of sub-carrier broadcasts,and several consumers may contribute to the same frequency using superposition coding.The SCMA approach,together with codebook design for each user,is used to improve channel efficiency through better management of the available spectrum.How-ever,developing a codebook with a greater number of value sets is still another challenge.With enhanced techniques of encoding and decoding for 5G networks,mapping the multidimensional constellations in the SCMA system plays a signif-icant role in improving the system performance and enhancing the overall system performance.The creation of a codebook utilizing the SCMA approach in con-junction with the lattice theory is suggested in this study.The prototype is shaped using a popular lattice,such as A n and D n,as the basis.Afterward,from the primary lattice constellation,the multidimensional complex mother constellation with the most noticeable variance in power is discovered.The lattice-based cod-ing is generated by combining the codebooks with the mother constellation,and the codes in the matrices are mapped by rotating the constellations in this context.The suggested technique,in conjunction with the investigation of novel SCMA codebook sets,provides improved performance in terms of Bit Error Rate(BER)and complexity with regard to Signal to Noise Ratio(SNR).Finally,the bit error rate is reduced for various SNRs during transmission in the channel.展开更多
Traditional orthogonal frequency division multiplexing(OFDM)based visible light communication(VLC)system is susceptible to high peak-to-average power ratio(PAPR),thus leading to low power efficiency.To address this is...Traditional orthogonal frequency division multiplexing(OFDM)based visible light communication(VLC)system is susceptible to high peak-to-average power ratio(PAPR),thus leading to low power efficiency.To address this issue,a sparse code multiple access(SCMA)codebook design method has been proposed to lower the PAPR of the clipping based OFDM-VLC system.展开更多
Sparse code multiple access(SCMA) is a novel non-orthogonal multiple access scheme proposed to meet the challenging demand of the future 5G communications, especially in support of the massive connections. The coded b...Sparse code multiple access(SCMA) is a novel non-orthogonal multiple access scheme proposed to meet the challenging demand of the future 5G communications, especially in support of the massive connections. The coded bits from each data stream will be directly mapped as multi-dimensional SCMA codeword in complex domain and then spread onto the physical resource elements in a sparse manner. The number of codewords that can be nonorthogonally multiplexed in one SCMA block can be made much larger than the number of orthogonal resource elements therein, resulting in an overloaded system. The sparsity in the spreading pattern and the design in the multidimensional modulator jointly ensure the SCMA codewords can be robustly decoded with low complexity. In this paper, we focus on the low complexity receiver design and verified the superior of an SCMA system via simulations and real-time prototyping. Lab tests and field tests all show that SCMA is a promising candidate for 5G non-orthogonal multiple access which can provide up to 300% overloading that triples the whole system throughput while still enjoying the link performance close to orthogonal transmissions.展开更多
基金supported by the NSFC Young Scientists Research Fund(61501047)
文摘Sparse code multiple access （SCMA） is a competitive nonorthogonal access scheme for the next mobile communication. As a multiuser sharing system, SCMA adopts message passing algorithm （MPA） for decoding scheme in receiver, but its iterative method leads to high computational complexity. Therefore, a serial message passing algorithm based on variable node （VMPA） is proposed in this paper. Making some subtle alterations to message update in original MPA, VMPA can greatly reduce overall computing complexity of decoding scheme. Furthermore, considering that serial structure may increase decoding delay, a novel grouping scheme based sparse matrix is applied to VMPA. Simulation results verify that the new algorithm, termed as grouping VMPA （G-VMPA）, can achieve a better tradeoff between bit error rate （BER） and computing complexity than MPA.
基金supported by National Natural Science Foundation of China(61801046)。
文摘Sparse code multiple access-based uplink grant-free transmission(SCMA-UGFT)has been proposed to realize ultra reliable and low latency communication(URLLC)in the fifth generation(5 G)system.Without the process of resource request and grant,users may collide in the same resource.To compensate the potential user performance decline,resource scheduling becomes a tough issue in the SCMA-UGFT system.This article proposes a duplicated transmission-based resource scheduling(DTBRS)scheme for SCMA-UGFT system by considering the URLLC scenario.Different from the existing schemes,not only one shared basic transmission units(BTUs)are allocated to a user equipment(UE)in the proposed DTBRS scheme for initial transmission to realize the duplicated transmission and to guarantee the transmission reliability.Besides,according to the proposed DTBRS scheme,one or two exclusive BTUs are assigned to a UE for retransmission to avoid the re-collision.At last,each packet is given a lifetime to limit the transmission latency to meet the URLLC latency requirement.The simulation demonstrates that the DTBRS scheme can achieve a better performance than the existing state-of-the-art scheme in terms of the average packet drop rate.
文摘A SCMA ACO-OFDM downlink visible light communication(VLC)system is proposed.Six users share four spectrum resources,four of which are 4 primary color LED lights.ACO-OFDM technology is used to convert the user’s sparse codebook mapped signal into a positive real value signal that can be carried on the light wave,which can realize high-speed parallel communication.Simulation verifies the feasibility of the system.At the same time,the channel model of visible light communication is constructed,and the signal-to-noise ratio(SNR)and channel gain of the visible light channel are systematically analyzed.Finally,the theoretical bit error rate formula using MPA decoding algorithm under different codebook constellation mapping points is given.Through simulation,it is verified that the theoretical bit error rate formula is basically consistent with the simulation bit error rate formula.
文摘The sparse code multiple access(SCMA)scheme is a Non-Orthogonal Multiple Access(NOMA)type of scheme that is used to handle the uplink com-ponent of mobile communication in the current generation.A need of the 5G mobile network is the ability to handle more users.To accommodate this,the SCMA allows each user to deploy a variety of sub-carrier broadcasts,and several consumers may contribute to the same frequency using superposition coding.The SCMA approach,together with codebook design for each user,is used to improve channel efficiency through better management of the available spectrum.How-ever,developing a codebook with a greater number of value sets is still another challenge.With enhanced techniques of encoding and decoding for 5G networks,mapping the multidimensional constellations in the SCMA system plays a signif-icant role in improving the system performance and enhancing the overall system performance.The creation of a codebook utilizing the SCMA approach in con-junction with the lattice theory is suggested in this study.The prototype is shaped using a popular lattice,such as A n and D n,as the basis.Afterward,from the primary lattice constellation,the multidimensional complex mother constellation with the most noticeable variance in power is discovered.The lattice-based cod-ing is generated by combining the codebooks with the mother constellation,and the codes in the matrices are mapped by rotating the constellations in this context.The suggested technique,in conjunction with the investigation of novel SCMA codebook sets,provides improved performance in terms of Bit Error Rate(BER)and complexity with regard to Signal to Noise Ratio(SNR).Finally,the bit error rate is reduced for various SNRs during transmission in the channel.
文摘5G新技术应用于可见光通信(Visible Light Communication,VLC)场景对系统容量以及频谱效率有了更高的要求,稀疏码多址接入(Sparse Code Multiple Access,SCMA)技术作为一种新型的非正交多址接入(Non-Orthgonal Multiple Access,NOMA)技术可作为解决方案。针对上述方案,搭建了VLC-SCMA系统,使得系统在相同的频谱资源下能够拥有更大的系统容量和频谱效率,同时为了降低系统复杂度,加快接收端进行多用户检测时的收敛速度,提出了基于串行改进下的部分外部信息传递的消息传递算法(Message Passing Algorithm Based on Serial Strategy for Partial External Information Transmission,SPEIT-MPA)。通过在迭代过程中设置门限值过滤掉携带信息量较少的外部信息点,利用串行改进使得算法迭代过程进一步简化。在VLC-SCMA系统中的仿真结果表明,对比原始算法,新算法可以在保证误码率(Bit Error Rate,BER)性能损失较少的前提下拥有更快的收敛速度,且算法复杂度随着信噪比(Signal to Noise Ratio,SNR)的增大明显降低。
基金supported by the National Natural Science Foundation of China(No.62071365)the Key Research and Development Program of Shaanxi Province(No.2017ZDCXL-GY-06-02)。
文摘Traditional orthogonal frequency division multiplexing(OFDM)based visible light communication(VLC)system is susceptible to high peak-to-average power ratio(PAPR),thus leading to low power efficiency.To address this issue,a sparse code multiple access(SCMA)codebook design method has been proposed to lower the PAPR of the clipping based OFDM-VLC system.
文摘Sparse code multiple access(SCMA) is a novel non-orthogonal multiple access scheme proposed to meet the challenging demand of the future 5G communications, especially in support of the massive connections. The coded bits from each data stream will be directly mapped as multi-dimensional SCMA codeword in complex domain and then spread onto the physical resource elements in a sparse manner. The number of codewords that can be nonorthogonally multiplexed in one SCMA block can be made much larger than the number of orthogonal resource elements therein, resulting in an overloaded system. The sparsity in the spreading pattern and the design in the multidimensional modulator jointly ensure the SCMA codewords can be robustly decoded with low complexity. In this paper, we focus on the low complexity receiver design and verified the superior of an SCMA system via simulations and real-time prototyping. Lab tests and field tests all show that SCMA is a promising candidate for 5G non-orthogonal multiple access which can provide up to 300% overloading that triples the whole system throughput while still enjoying the link performance close to orthogonal transmissions.
