Wireless terabit-per-second (Tb/s) links will become an urgent requirement within the next 10 years. However, current methodology for high data rate wireless communication that keep increasing the M-ary modulation schemes and the order of MIMO spatial multiplexing cannot reach Tb/s with a low power consumption. Thus, a new methodology is required with a large bandwidth in the millimeter-wave (mm-Wave) and sub-Terahertz (sub-THz) bands above 90GHz. In addition, it must be able to provide an extremely high spectral efficiency with a low energy consumption. Note that this consumption can be reduced by using constant-envelope modulations such as continuous phase modulation (CPM). However, the CPM has a very low spectral efficiency that limits the desired data rate. This paper suggests a new methodology to reach 1 Tb/s with a low power consumption by using power efficient single carrier with Index Modulation (IM). Simulation results under various uncorrelated/correlated fading channels show that the systems with power efficient modulations as CPM or QPSK can achieve Tb/s with a good performance. Moreover, the link budget and power estimation prove that the constant and near-constant envelope modulations require less than 1−3 Watts for 1 Tb/s with 10 −4 un-coded BER. Finally, this paper shows that conveying most of the information bits using IM to reach an ultra-high data rate is more power efficient than high order MIMO spatial multiplexing with large M-ary QAM as used in LTE.
A novel domain for Index Modulation (IM) named "Filter Domain" is proposed. This new domain generalizes many existing modulations and IM domains. In addition, a novel scheme "Filter Shape Index Modulation" (FSIM) is proposed. This FSIM scheme allows a higher Spectral Efficiency ( SE) gain than the time and frequency IM dimensions in Single-Input Single-Output (SISO) systems. In the FSIM system, the bitstream is mapped using an Amplitude Phase Modulation (APM) as QAM or PSK, and an index of a filter-shape c hanging a t the symbol rate. This filter s hape, b eing c hanged a t e ach symbol, enables a SE gain in SISO system without sacrificing a ny time or frequency resources. Compared to an equivalent 8QAM and 16QAM schemes and at the same SE, the FSIM with QPSK using 2 and 4 non-optimal filter s hapes a chieves a g ain o f 3.8 dB and 1.7 dB respectively at BER= 10 −4 , and this superiority is maintained in frequency selective fading channel compared to equivalent SISO-IM schemes. A low complexity detection scheme, approaching the maximum likelihood detector performance, is proposed along with a full performance characterization in terms of theoretical probability of filter i ndex e rror a nd B ER lower bound. Finally, FSIM can achieve better spectral and energy efficiencies w hen a fi lter ba nk an d an IS I ca ncellation technique are optimally designed.
Multiple-Input Multiple-Output (MIMO) systems and sub-TeraHertz (sub-THz) bands are being considered for the development of ultra-high data rate applications in beyond 5G. However, sub-THz band suffers from many technological limitations and severe RF-impairments such as low output power, limited resolution of high-speed ADCs, and important Phase Noise (PN) introduced by the Local Oscillator (LO). In this paper, MIMO Spatial Multiplexing (SMX) and Generalized Spatial Modulation (GSM) are compared from different perspectives while considering the sub-THz impairments. The effect of PN has been investigated for both systems in sub-THz channels using uniform linear and rectangular antenna arrays. The comparison is also performed in terms of Peak-to-Average-Power-Ratio (PAPR), power consumption, detection complexity and transmitter/receiver cost. In addition, the link budget and the system power consumption is estimated for both systems. The obtained results reveal that, when low order modulation schemes like QPSK is used, GSM outperforms SMX by a gain ranging from 4 up to 6.2 dB with a throughput rate reaching 0.5 Tbps that leads to 3.25 dB power gain with medium PN and noncoherent detection. Thus enforcing the GSM to be a promising candidate for ultra-high wireless data rate communication in sub-THz bands.
Generalized spatial modulation (GSM) is a promising technique that can highly increase the spectral efficiency for ultra-high data rate systems. However, its performance degrades in highly correlated channels such as those in the millimeter wave (mmWave) and sub-Terahertz (sub-THz) bands. GSM conveys information by the index of the activated transmit antenna combination (TAC) and by the M-ary symbols. In conventional GSM, the legitimate TACs are randomly selected, where their number should be a power of 2. In this paper, a simplified EGSM (S-EGSM) based on TAC selection but without channel side information (CSI) is proposed for highly correlated channels. Moreover, an efficient Index-to-Bit mapping for spatial bits based on Gray coding is proposed to reduce the spatial bit-error rate (BER) instead of using the normal binary mapping as in conventional GSM. Simulation results show that the proposed TAC selection without CSI (S-EGSM) outperforms the existing method by 1.4 dB in highly correlated channels. In addition, the proposed S-EGSM when compared to TAC selection with CSI can be considered as a good trade-off between performance and complexity since it does not consider any feedback from the channel when updating the TAC selection, which are, in the proposed approach, determined offline. Finally, simulation results of gray coding for spatial bits show a performance gain of the order of 1 dB in highly correlated channels, and which becomes less significant in case of low spatially correlated channels.
UFMC is a candidate waveform technology for 5G wireless systems and beyond. It combines the simplicity of OFDM with the advantages of FBMC. However, these advantages come together with an increase in the complexity at the transmitter caused by the implementation of a filter and applying an FFT for each sub-band, whereas at the receiver it is due doubling the size of the FFT being implemented. Then a low-complexity solutions must be found. UFMC waveform and FFT pruning have been widely studied recently but separately. In this paper, the computational complexity of different UFMC implementation methods with FFT pruning is evaluated. Depending on the number of sub-bands, it is shown that a complexity reduction up to 50% of the UFMC transmitter can be obtained. Also, the UFMC receiver complexity can be reduced to be similar or even less than OFDM. This complexity reduction of the UFMC transceiver comes without performance degradation since no computational approximation is introduced.
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