Active Interference Cancellation Technologies In UFMC Systems

With supporting asynchronous framework,segmented spectrum operation,and low latency,universal filtered multi-carrier modulation technology(UFMC)has attracted plenty of attentions from academia and industry and it is a communication scheme with great potential.To gain better performance,the paper mainly designs active interference cancellation(AIC)technologies in UFMC systems.The contents are listed as follows:First,we propose a kind of AIC encoding algorithm which can improve the performance of the existing UFMC systems and utilize the least square criterion(LS)to derive the best encoding scheme.By filtering a series of successive sub-carriers,UFMC can achieve lower out-of-band(OOB)emission as compared to OFDM and it has low sensitivity to CFO.However,to gain better performance for UFMC systems,the filter design often teems with challenges.Therefore,we propose to apply AIC to UFMC systems.The key idea is that every user turns to the narrow guard between every two successive sub-bands in UFMC systems and inserts some interference cancellation subcarriers(ICSs)symmetrically on both sides of the sub-band it adopts to suppress the interference on its adjacent sub-bands.These ICSs are then modulated by proper weighting factors.With the equivalent cooperation among users,we aim to minimize inter-sub-band inter-ference by optimizing the weighting factors.Numerical results show that our proposed scheme makes inter-sub-band interference suppression very effective.Then,we design an enhanced inter-sub-band interference suppression scheme by taking into account power consumption.By combing the multi-objective programming(MOP)and La-grangian dual algorithm,we have obtained the closed-form solutions.ICSs do not carry any use-ful information.For some communication systems with limited power cost,we need to take into account the power consumed by ICSs.Specifically,every user inserts some ICSs symmetrically on both sides of every sub-band,which carry special information with some power constraints.Simulation results validate that as compared to the conventional UFMC systems,the modified scheme can achieve higher transmission rate and better bit error ratio(BER)performance ei-ther for additive white gaussian noise(AWGN)channel or for Rayleigh channel.Moreover,our proposal can significantly reduce the filter design requirements.At last,we propose a brand-new adaptive AIC algorithm,which can adaptively encode transmit data in accordance with the state of each sub-band(active or not).In real communi-cation scenarios,especially machine type communication(MTC),terminals transmit data inter-mittently.When its adjacent sub-bands are not occupied,it is not necessary for the user to insert ICSs.Hence,faced with the kind of communication system,we develop an adaptive interference cancellation encoding protocol.All active users first transmit several frames to the base station(BS)without ICSs.After that,the BS feeds back to users the subcarrier index with the lowest average signal-to-interference plus noise ratio(SINR)among all active subcarriers.Based on some pre-defined threshold,each active user decides whether to insert some ICSs to reduce the interference on the subcarrier.The overall SINR performance can be finally maximized by the continuous feedback and adjustment process.We have validated our proposals via extensive sim-ulation,which shows that they can achieve far better SINR and BER performance as compared to the traditional UFMC under different CFOs and/or Rayleigh block fadings.