Detection And Analysis For 5G Sparse Multiple Access

The rapid development of communication techniques render wireless networks evolve into the Internet of Things(IoT).Compared with the existing communication networks,the next generation IoT networks may face the following requirements and challenges.First is the massive access of user equipments(UE).By estimate,the number of devices linked to the wireless network will reach to 50 billions till the year of2020.In contrast,the existing networks could accommodate several billions of users only.Further,the low latency transmission between wireless devices is another concern.To support the 5G applications such as telemedicine,industrial robot control,and automatic drive with vehicular networking,the future wireless networks should insure the millimeter-level delay.Moreover,with the scarce spectrum resource,it is also necessary to consider the ways to improve the level of spectrum resource utilization.To meet the above challenges,the design of new type air interface technology is becoming significant.In this paper,we will focus on the design of new type air interface technology as well as the fundamental limits of massive random access in multiple-input multiple-output(MIMO)antenna systems.For the design of new type air interface technology,we will consider the sparse code multiple access(SCMA),which is kind of non-orthogonal multiple access(NOMA).The decoder design for SCMA will be addressed first,and a low complexity SCMA signal detector based on sphere decoding is proposed in this paper.Sphere decoder can avoid the exhaustive search for the possible transmission points and thus reduces the computational complexity.For the channel estimation and active users detection in Grant-Free,we have proposed a joint detector that explores both pilot and data signals.Compared with pilot-aided only scheme,the proposed joint detector has a better estimation accuracy.Finally,the fundamental limits of MIMO massive random access will also be investigated in this paper.Compared with conventional multiple access channel,the number of users within massive access channel may be comparable with the coding blocklength.Thus,with the philosophy of “quantitative change leads to qualitative”,the fundamental limits of MIMO massive random access may also possess some new behaviors.The design of new type air interface technology is a significant aspect in 5G network.The proposed decoder design for SCMA may be a well referential for the multiuser receiver design in NOMA.On the other hand,the study on the fundamental limits of MIMO massive random access will help to enrich the multiuser information theory.The results can also shed some lights on the design for IoT networks with massive users access.