Uplink And Downlink Resource Reuse Strategies For Clustered MMTC

Mass Machine-Type Communications(mMTC),as the main form of existence of the Internet of Things(IoT),is one of the three application scenarios of the future wire-less communication network.How to achieve effective access to massive MTC de-vices(MTDs)has become one of the current research hotspots.Under the condition of limited resources,non-orthogonal multiple access(NOMA)and MTC multiuser clus-tering techniques become two key technologies for achieving large-scale access of the mMTC system.However,MTDs work in a dynamically distributed manner,resulting in dynamic changes in the number of MTDs that access the MTC Header(MTH)on each resource block at different times.When more than the expected number of MTDs are simulta-neously accessed on the same resource block,some MTDs will fail to access.In order to solve this problem,under the premise of guaranteeing the downlink communication rate of the base station(BS),this thesis deeply studies the uplink and downlink resource reuse strategy(UDRR)of the mMTC clustering network,and the main contributions and innovations are as follows.(1)For situations where there is no information exchange between clusters,MTDs users can reuse the downlink communication resources of their own cluster.There-fore,this thesis proposes a NOMA-based uplink and downlink resource reuse strategy in the same cluster(UDRR_S),its essence is the distributed resource allocation problem of NOMA system under complex constraints.Under the condition of guaranteeing the BS-MTH downlink communication rate of this cluster,we have established an opti-mization problem to maximize the number of access MTDs.Because the search space for this problem is very large and difficult to solve,we have designed a UDRR_S al-gorithm based on successive interference cancellation(SIC)and using greedy selection strategies.At the same time,the upper bound of the optimal solution and the relationship between mMTC system outage probability and number of access users are derived.(2)For the case of full information exchange between clusters,MTDs users can reuse the downlink communication resources of other clusters.Therefore,this thesis proposes an uplink and downlink resource reuse in different clustrers(UDRR_D)based on interference coordination,its essence is the uplink and downlink interference coordi-nation problem of multi-cluster networks under multi-constraints.In the case of guaran-teeing the downlink communication rate of BS-MTHs,we established the optimization problem of maximizing the sum rate of all the MTDs-MTH uplink communication of all clusters.we decompose this optimization problem into two sub-optimization problems,resource allocation and power control.Furthermore,we have designed a UDRR_D al-gorithm,including resource block allocation algorithm based on interference conflict graph and iterative power control algorithm based on Lagrangian multiplier method are designed.Furthermore,the complexity of these algorithms and system performances under multiple reuse mechanisms are also analyzed.Analysis and simulation results show that the uplink and downlink resource reuse strategy proposed in this thesis can effectively reduce the system outage probability and improve the uplink communication system capacity,so as to meet the access require-ments of a large number of MTDs users.