Study On Information Embedding/Superposition Based Transmission Technologies Toward Next-Generation Wireless Communications

Due to the continuous growth of mobile devices and rapid development of Internet of things,the next-generation wireless communication networks impose an explosive demand on high spectral efficiency over limited radio resources.However,while improving the spectral efficiency to meet the fast-growing demand for mobile services,the issue of energy consumption in the information and communication technologies(ICT)industries has also become prominent.Recent reports show that ICT industries account for 10% of the global power consumption.It can be expected that with a dramatic increase in the number of mobile devices every year,the power consumption of ICT industries will continue to increase.Therefore,developing new types of wireless transmission technologies to achieve both high spectral efficiency and high energy efficiency is of great importance.Conventional multiple-input-multiple-output(MIMO)may achieve high spectral efficiency with massive antennas,but has compromised energy efficiency due to the scaled power consumption of a large number of radio frequency(RF)chains.The orthogonal frequency division multiplexing(OFDM)has high spectral efficiency,but is prone to Doppler-induced intercarrier interference and suffers from high peak-to-average power ratio(PAPR).Novel advanced modulation techniques are therefore very demanding.To this end,the recently emerging index modulation(IM)techniques,which rely on the indices of some medium to convey embedding information,arise as a promising candidate for the next-generation wireless communications.Specifically,by activating part of transmit antennas to convey embedding index information,spatial modulation(SM)has been proven to strike a favorable trade-off between spectral efficiency and energy efficiency.Using the activation states of partial sub-carriers to convey additional index information,OFDM with index modulation(OFDM-IM)improves the spectral efficiency and energy efficiency while alleviating PAPR and facilitating easier inter-carrier interference mitigation thanks to idle sub-carriers.Recently,non-orthogonal principle has received great interest due to its potential to surpass the orthogonal one in both spectral efficiency and energy efficiency.Conventional single-carrier frequency domain equalization(SC-FDE)system multiplexes pilots and data symbols in an orthogonal manner,which requires extra spectral resources for the pilots and thus reduces the spectral efficiency and the transmission rate.In order to improve the spectral efficiency of SCFDE systems,frequency domain pilot multiplexing technique(FDPMT)is developed,which multiplexes the pilots and data symbols in a non-orthogonal manner.It has been shown that FDPMT can achieve similar error performance to the orthogonal technique like frequency expanding technique(FET),but achieve much higher spectral efficiency and energy efficiency.On the other hand,being able to break the limitation of the conventional orthogonal multiple access(OMA),non-orthogonal multiple access(NOMA)recently emerges as a promising multiple access technique to enlarge connections,improve spectral efficiency,balance user fairness,and support diverse services for the next-generation wireless communication networks.The contributions of this dissertation are summarized as follows.1)Two low-complexity algorithms based on the deterministic sequential Monte Carlo(DSMC)technique for the demodulation of generalized SM(GSM).The type-I demodulator,which uses the conventional successive interference cancellation(SIC)as the kernel and draws antenna-wise samples from the extended constellation,is proposed for the overdetermined GSM system.The type-II demodulator,which consists of two stages and uses the orthogonal matching pursuit(OMP)as the kernel in the first stage,is proposed for the underdetermined GSM system.A key component in both algorithms is an efficient online scheme to eliminate the illegal samples during the sampling process.Both proposed algorithms achieve near-optimal performances with complexity linear in terms of the transmit antenna size.Moreover,owing to their soft-input soft-output nature,they can be employed in a turbo receiver for a coded GSM system.2)A novel variant of OFDM techniques referred to as OFDM with in-phase/quadrature index modulation(OFDM-I/Q-IM)is proposed,which carries additional information bits through the index domain including in-phase and quadrature dimensions.Specifically,OFDM-I/Q-IM applies index modulation independently on the in-phase/quadrature component of the OFDM sub-block to improve the spectral efficiency and system performance.Then a novel low-complexity detector based on the maximum-likelihood(ML)criterion for OFDM-I/Q-IM is proposed for the receiver,which does not need to know the variance of the noise and the possible realizations of the active sub-carrier indices.With the proposed ML detector,the asymptotic average bit error probability and the exact coding gain achieved by OFDM-I/Q-IM are also derived.3)The relationship between the interference pattern and the loss of equal-spaced tones is discovered and proven for FDPMT.By exploiting this relationship,a novel pilot position selection(PPS)method and a novel signal reconstruction(SR)method are proposed.The proposed PPS method,which is based on the minimization of the most severe intersymbol interference experienced by those sub-blocks decimated from the transmitted signal block,dispenses with a priori knowledge of the channel statistics and imposes very low computational cost to the transmitter.The proposed SR method,which is based on the ML criterion,can be carried out sub-block-by-sub-block in parallel and sample-by-sample within each sub-block,saving the computational complexity and time consumption of the receiver.Simulation results in terms of bit error rate corroborate the superiority of both proposed methods over their existing counterparts in various channels of interest.4)A NOMA-based two-way relay network with secrecy considerations is developed,in which two users wish to exchange their NOMA signals via a trusted relay in the presence of single and multiple eavesdroppers.To ensure secure communications,the relay not only forwards confidential information to the legitimate users but also keeps emitting jamming signals all the time to degrade the performance of any potential eavesdropper.Moreover,the relay and each user are equipped with the full-duplex technique in the multiple-access phase to combat the eavesdropping and improve the data transmission efficiency,respectively.Different decoding schemes based on the SIC for the legitimate users,relay,and eavesdroppers are proposed.Closed-form expressions for the achievable ergodic secrecy rates of all data symbols under both single-and multiple-eavesdropper cases are derived,validated by the excellent fitting to the simulation results for the proposed network.