Abstract
Different from traditional communication systems, information-centric Internet of things (IC-IoT) as a novel smart paradigm needs to guarantee end-to-end connectivity for rapidly growing smart devices. How to meet the demands of massive connection has become a key problem for IC-IoT. Sparse code multiple access (SCMA) as a code-domain non-orthogonal multiple access (NOMA) technique has been intensively investigated. With SCMA, each user employs different sub-carrier frequencies for transmission, and different users can share the same sub-carrier frequency via superposition coding. The spectrum efficiency is thus improved. However, designing large-scale codebook sets is still an open problem for SCMA. In this paper, a new lattice-based codebook design method is proposed via mother constellation optimization. First, the optimization problem of the mother constellation is formulated. Through analysis, the problem can be converted into two sub-problems. Accordingly, we first use the lattice theory to find a constellation containing infinite points with large coding gain. After that, we search for a boundary that contains a set of points via spherical packing. Such an approach enables us to obtain a real constellation satisfying a power saving criterion. Secondly, the mother constellation with large power variance is obtained from the real multi-dimensional constellation. Finally, lattice-based codebooks are generated by combining the mother constellation and the mapping matrices with constellation rotation. Simulations demonstrate that the designed codebooks have improved bit error rate (BER) performance with large codebook size, especially at high signal to noise ratio (SNR).
Highlights
We propose a new sparse code multiple access (SCMA) codebook design method based on the lattice theory
By using the lattice theory to obtain the multidimensional constellation with power saving criteria, we find that the generation matrix is the key factor that determines the symbol error probability (SEP) performance of the constellation
The reasons are based on the following two points: i) For any SCMA system, N characterizes the sparsity of SCMA, and determines the complexity and overload ratio of the system. ii) The length K of the spreading sequences tend to be small in the SCMA systems, such as K = 4 and K = 6
Summary
A. BACKGROUND As an emerging network technology, Internet of things (IoT) attracts growing attention in fifth generation (5G) [1], [2]. The objective of 5G IoT is to realize the intelligent lifestyle of human beings by using smart devices connected to the Internet [3], [4]. In application scenarios of IoT, smart cities have become a hot topic. The differences between heterogeneous networks make the traditional TCP/IP protocol unable to meet the urgent needs of the IoT in terms of the data exchange latency [5].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
