Showing papers on "Frequency-division multiplexing published in 2016"
TL;DR: In this article, the uplink performance of a quantized massive MIMO system that deploys orthogonal frequency division multiplexing (OFDM) for wideband communication is investigated.
Abstract: Coarse quantization at the base station (BS) of a massive multi-user (MU) multiple-input multiple-output (MIMO) wireless system promises significant power and cost savings. Coarse quantization also enables significant reductions of the raw analog-to-digital converter data that must be transferred from a spatially separated antenna array to the baseband processing unit. The theoretical limits as well as practical transceiver algorithms for such quantized MU-MIMO systems operating over frequency-flat, narrowband channels have been studied extensively. However, the practically relevant scenario where such communication systems operate over frequency-selective, wideband channels is less well understood. This paper investigates the uplink performance of a quantized massive MU-MIMO system that deploys orthogonal frequency-division multiplexing (OFDM) for wideband communication. We propose new algorithms for quantized maximum a posteriori channel estimation and data detection, and we study the associated performance/quantization tradeoffs. Our results demonstrate that coarse quantization (e.g., four to six bits, depending on the ratio between the number of BS antennas and the number of users) in massive MU-MIMO-OFDM systems entails virtually no performance loss compared with the infinite-precision case at no additional cost in terms of baseband processing complexity.
221 citations
TL;DR: DSP techniques for channel aggregation and deaggregation, frequency-domain windowing, adjacent channel leak age ratio reduction, and synchronous transmission of both the I/Q waveforms of wireless signals and the control words (CWs) used for control and management purposes are presented.
Abstract: Mobile fronthaul is an important network segment that bridges wireless baseband units and remote radio units to support cloud radio access network. We review recent progresses on the use of frequency-division multiplexing to achieve highly bandwidth-efficient mobile fronthaul with low latency. We present digital signal processing (DSP) techniques for channel aggregation and deaggregation, frequency-domain windowing, adjacent channel leak age ratio reduction, and synchronous transmission of both the I/Q waveforms of wireless signals and the control words (CWs) used for control and management purposes. In a proof-of-concept experiment, we demonstrate the transmission of 48 20-MHz LTE signals with a common public radio interface (CPRI) equivalent data rate of 59 Gb/s, achieving a low round-trip DSP latency of <2 μs and a low mean error-vector magnitude (EVM) of ∼2.5% after fiber transmission. In a follow-up experiment, we further demonstrate the transmission of 32 20-MHz LTE signals together with CPRI-compliant CWs, corresponding to a CPRI-equivalent data rate of 39.32 Gb/s, in single optical wavelength channel that requires an RF bandwidth of only ∼1.6 GHz. After transmission over 5-km standard single-mode fiber, the CWs are recovered without error, while the LTE signals are recovered with an EVM of lower than 3%. Applying this technique to future 5G wireless networks with massive multiple-input multiple-output is also discussed. This efficient mobile fronthaul technique may find promising applications in future integrated fiber/wireless access networks to provide ultrabroadband access services.
163 citations
TL;DR: In this article, the design and characterization of a heterogeneous 36-core, three-mode fiber with three core types is described, and the total transmission capacity is investigated using free-space multiplexing/demultiplexing technologies, 40-wavelength division multiplexed, 25 GBd, 93.4Gb/s dual-polarization QPSK signals, and coherent detection with a sparse 6 × 6 MIMO equalizer.
Abstract: We describe the design and characterization of a heterogeneous 36-core, three-mode fiber with three core types. Intercore crosstalk for LP11 modes is estimated to be below −31 dB for 5.5 km propagation at a core pitch of 34 μm. Feasibility of 108 space/mode division multiplexed transmission is investigated using free-space multiplexing/demultiplexing technologies, 40-wavelength division multiplexed, 25 GBd, 93.4-Gb/s dual-polarization QPSK signals, and coherent detection with a sparse 6 × 6 MIMO equalizer. The total transmission capacity amount to 403.7 Tb/s.
83 citations
TL;DR: For the first time, the generation, detection, and transmission performance over transoceanic distances of 10 Gbd nonlinear inverse synthesis-based signal, in which the transmitted information is encoded directly onto the continuous part of the signal nonlinear spectrum is demonstrated.
Abstract: Nonlinear Fourier transform (NFT) and eigenvalue communication with the use of nonlinear signal spectrum (both discrete and continuous) have been recently discussed as promising transmission methods to combat fiber nonlinearity impairments. In this paper, for the first time, we demonstrate the generation, detection, and transmission performance over transoceanic distances of 10 Gbd nonlinear inverse synthesis-based signal (4 Gb/s line rate), in which the transmitted information is encoded directly onto the continuous part of the signal nonlinear spectrum. By applying effective digital signal processing techniques, a reach of 7344 km was achieved with a bit error rate (2.1 × 10−2) below the 20% FEC threshold. This represents an improvement by a factor of ∼12 in data capacity × distance product compared with other previously demonstrated NFT-based systems, showing a significant advance in the active research area of NFT-based communication systems.
65 citations
TL;DR: The proposed optimal SEFDM signals allow to increase spectral efficiency and to reduce the frequency bandwidth up to 32% with respect to orthogonal frequency division multiplexing (OFDM) signals.
Abstract: Examination of a method of increasing the spectral and energy efficiency of the nonorthogonal multifrequency spectrally efficient frequency division multiplexing (SEFDM) signals is considered. This method consists in the application of optimal envelopes of signals increased duration on each subcarrier frequency under intersignal interference for fix data rate. Multistep optimization problem for the determination of the set of envelopes of these SEFDM signals was proposed and numerically solved. The proposed optimal SEFDM signals allow to increase spectral efficiency and to reduce the frequency bandwidth up to 32% with respect to orthogonal frequency division multiplexing (OFDM) signals.
60 citations
TL;DR: The evolution of AON architectures based on the different all optical switching and multiplexing technologies (i.e., TDM, FDM, and SDM), which is one of the main areas of focus in this article, is reviewed.
Abstract: Research into all optical network (AON) technology has been ongoing over the past decade, and new features are constantly being developed The advantages of AON include large-bandwidth provisioning, low-latency transmission and low energy consumption The basic concept underlying AON is transmission of data signals entirely through the optical domain from source to destination nodes, with no optical-electrical-optical (O-E-O) conversion at intermediate nodes The technologies used to implement AON have undergone a series of evolutions, which encompass time division multiplexing (TDM), frequency division multiplexing (FDM), and space division multiplexing (SDM) Multi-dimensional AON (MD-AON), which leads the trend of AONs future architecture, provides a vibrant state for emerging applications such as cloud computing and Internet of Things (IoT) In this article, we review the evolution of AON architectures based on the different all optical switching and multiplexing technologies (ie, TDM, FDM, and SDM), which is one of the main areas of focus in this article The other main area is detailed discussion of implementations such as data plane and control plane technologies as well as resource optimization technologies for realizing AON We also introduce several AON testbeds with their compositions and functions, and some potential application scenarios that can be implemented based on these testbeds
54 citations
TL;DR: Compared with existing DCEM methods, ACE-BOC has much higher design flexibility in the number of signal components, power ratio among components, hardware complexity of both transmitters and receivers, and spectrum compatibility.
Abstract: In the signal design of new generation global navigation satellite systems, there is a strong demand for multiplexing multiple binary spreading signals on two adjacent frequencies into an integrated signal with a constant envelope. In this paper, a dual-frequency constant envelope multiplexing (DCEM) technique with high-design flexibility based on subcarrier waveform reconstruction, named asymmetric constant envelope binary offset carrier (ACE-BOC), is presented. This multiplexing technique can be seen as a generalized alternate BOC. It can combine four or fewer independent, bipolar, direct sequence spread spectrum signals onto two sidebands of a spectrum-split integrated signal, where each sideband consists of two or fewer signals with arbitrary power ratio modulated onto the quadrature components. The design principle, diversified generation methods of ACE-BOC signals, as well as the characteristics in both time and frequency domains are investigated. Multiplexing efficiency and receiving performance of this signal are also analyzed. Analysis with typical examples shows that, for both transmitters and receivers, ACE-BOC signals have multiple processing forms. Compared with existing DCEM methods, ACE-BOC has much higher design flexibility in the number of signal components, power ratio among components, hardware complexity of both transmitters and receivers, and spectrum compatibility. Such high-level design flexibility provides system designers great room in signal scheme optimization for varied navigation applications in the future.
52 citations
TL;DR: In this article, a new optical spectrally efficient frequency division multiplexing technique, utilizing coherent detection and polarization detection, was proposed and demonstrated, using non-orthogonal and overlapping subcarriers to provide a significant reduction in both electrical and optical bandwidth.
Abstract: A new optical spectrally efficient frequency division multiplexing technique, utilizing coherent detection and polarization division multiplexing, is proposed and demonstrated. The proposed system uses non-orthogonal and overlapping subcarriers to provide a significant reduction in both the electrical and optical bandwidth of up to 33%, relative to dual polarization orthogonal frequency division multiplexing (DP-OFDM), with an implementation penalty <3.2 dB. After transmission over 80 km of single mode fiber, it is shown that quadrature phase shift keying-based DP coherent optical spectrally efficient frequency division multiplexing, achieves a 2-dB gain in optical signal-to-noise ratio performance relative to eight-quadrature amplitude modulation-based DP-OFDM, which has approximately the same spectral efficiency.
48 citations
TL;DR: This paper focuses on the subframe structure, configuration, and contents, including subframe boundary symbols which carry additional pilots to assist with channel estimation at the receiver and cell multiplexing which maps physical layer pipe (PLP) payload data to physical layer resources within each subframe.
Abstract: An ATSC 3.0 physical layer frame consists of a bootstrap immediately followed by a preamble containing layer 1 control signaling and then one or more subframes carrying payload data. Subframes within a particular frame may be of the same or different types, with different subframe types being configured for different classes of receivers (e.g., mobile versus fixed). This paper focuses on the subframe structure, configuration, and contents, including subframe boundary symbols which carry additional pilots to assist with channel estimation at the receiver and cell multiplexing which maps physical layer pipe (PLP) payload data to physical layer resources within each subframe. Various methods for cell multiplexing multiple PLPs within a subframe are discussed and described, including time division multiplexing, frequency division multiplexing, time-frequency division multiplexing, and layered division multiplexing. Frequency interleaving, pilot insertion, and guard interval insertion are also covered, including a method of distributing extra samples to guard intervals in order to obtain frame lengths equal to an integer number of milliseconds.
47 citations
TL;DR: In this paper, a spectrally efficient frequency division multiplexing (SEFDM) was proposed to increase transmission data rates without changing signal bandwidth and modulation format in a 60 GHz mm-wave radio-over-fiber scenario.
Abstract: A bandwidth compressed waveform termed spectrally efficient frequency division multiplexing (SEFDM) is experimentally demonstrated in a 60-GHz millimeter-wave (mm-wave) radio-over-fiber scenario to increase transmission data rates without changing signal bandwidth and modulation format. Experimental results show the advantages of SEFDM and confirm that the bit rate of SEFDM signals can be substantially higher than that of orthogonal frequency-division multiplexing (OFDM) signals. Experimentally, a 2.25 Gbit/s 4QAM OFDM signal is transmitted through 250 m of OM-1 multi-mode fiber and then it is optically up converted to 60 GHz band at the photodiode before delivery to a mm-wave antenna for transmission over a 3 meter wireless link. The work demonstrates that when the OFDM signal is replaced by an SEFDM signal using the same modulation format and occupying the same bandwidth, the bit rate can be increased, by a factor of up to 67%, to 3.75 Gbit/s at the expense of a 3-dB power penalty. Additionally, a bandwidth compressed 4QAM SEFDM is shown to outperform an 8QAM OFDM of the same spectral efficiency, thereby verifying that a lower order modulation format may replace a higher order one and achieve performance gain.
45 citations
TL;DR: A novel measurement scheme for multiple high-frequency vibrations has been demonstrated by combining phase-sensitive optical time domain reflectometry (Ф-OTDR) and Mach-Zehnder interferometer (MZI) based on frequency division multiplexing.
Abstract: A novel measurement scheme for multiple high-frequency vibrations has been demonstrated by combining phase-sensitive optical time domain reflectometry (Ф-OTDR) and Mach-Zehnder interferometer (MZI) based on frequency division multiplexing. The light source is directly launched into the MZI structure, while it was modulated by an acoustic optical modulator (AOM) with a frequency shift of 200 MHz for the Ф-OTDR part. The vibration frequency is obtained by demodulating the interference signal obtained by the MZI structure, while the vibration position is located by Ф-OTDR system. The spatial resolution of 10m is obtained over 3 km sensing fiber. And the detectable vibration frequency reaches up to 40 kHz. Compared to the previous schemes, this system works without dead zone in the detectable frequency range. Furthermore, the frequency spectrum mapping method has been adopted to determine multiple high-frequency vibrations simultaneously. The experimental results prove the concept and match well with the theoretical analysis.
TL;DR: An analytical approach is proposed to evaluate the error probability of OFDM-IM subject to carrier frequency offset (CFO) in fading channels, where the inter-carrier interference (ICI) is properly divided into two parts: the intra-subblock ICI and theinter-subblocks ICI.
Abstract: OFDM-IM, which uses the indices of active subcarriers to carry additional information bits, is a novel multi-carrier transmission technique. In this letter, by exploiting the special design of OFDM-IM, we propose an analytical approach to evaluate the error probability of OFDM-IM subject to carrier frequency offset (CFO) in fading channels, where the inter-carrier interference (ICI) is properly divided into two parts: the intra-subblock ICI and the inter-subblocks ICI. Simulation results illustrate that the results of theoretical analysis are quite accurate, and OFDM-IM outperforms the conventional OFDM when CFO exists.
TL;DR: This paper shows that the proposed OPDMA not only has low computational complexity as the conventional Time Division Multiple Access (TDMA) and Frequency Division multiple Access (FDMA) protocols but also gains better energy efficiency, which consists with the energy saving requirement in green communications.
Abstract: In cellular networks, since Media Access Control (MAC) layer plays a key role in every access equipment, it fascinates that little progress on multiple access protocol could save considerable energy. Accordingly, this paper studies a novel MAC protocol, i.e., the power division multiple access (PDMA) protocol, with the purpose of green communication. As a fundamental study of PDMA, we first propose a power division multiplexing (PDM) scheme, analogous to the time division multiplexing and frequency division multiplexing. It is proved that the transmit power could be divided into multiple regular power segments (PSs) to simultaneously transmit multiple independent information/data streams in peer to peer communications. Based on our fundamental studies of PDM, an orthogonal PDMA (OPDMA) protocol is proposed to utilize multiplexing and degraded channel gains for energy saving. By adopting the orthogonal PSs proposed in OPDMA, multiple information streams in different channels could be transmitted efficiently and concurrently with quality of service guarantee. This paper shows that the proposed OPDMA not only has low computational complexity as the conventional Time Division Multiple Access (TDMA) and Frequency Division Multiple Access (FDMA) protocols but also gains better energy efficiency, which consists with the energy saving requirement in green communications.
TL;DR: In this article, a cost-effective coherent receiver is implemented by using the Alamouti polarization-time block coding scheme combined with heterodyne detection for the optical network unit in passive optical networks.
Abstract: In an access network based on a passive optical network architecture, coherent detection is attractive since it allows for high receiver sensitivity coupled with inherent frequency selectivity. Nevertheless, solutions employed in core networks are prohibitively complex and costly, requiring the optical complexity of the coherent receivers to be reduced to make them feasible for access networks. For monolithic integration, a key challenge is posed by the polarization beam splitter (PBS). If, however, the PBS is removed, the receiver needs to be redesigned to be insensitive to the incoming polarization state of the received signal. In this paper, we experimentally demonstrate a polarization-insensitive (i.e., polarization-independent) coherent receiver for the optical network unit in passive optical networks (PONs). The receiver consists of only a 3-dB coupler and a single-balanced photodiode such that the complexity is comparable to a direct detection receiver. The proposed cost-effective coherent receiver is implemented by using the Alamouti polarization-time block coding scheme combined with heterodyne detection. To verify the technique, the Alamouti-coded orthogonal frequency division multiplexing (OFDM) signal is rotated over the full Poincare sphere. Compared to the dual-polarization-OFDM signal operating at a net bit rate of 10 Gb/s per polarization (a gross bit rate of 10.7 Gb/s including a 7% FEC overhead), only a 0.6 dB sensitivity degradation is observed. The sensitivity at the FEC threshold, assumed to be $4\times 10^{-3}$ , is measured to be $-$ 41.5 dBm (56 photons-per-bit) on a 25-GHz grid. Following this, different channel spacings are investigated and the signal is transmitted over 80 km of standard single-mode fiber in a long-reach wavelength division multiplexed PON system. The loss budgets are found to be 43.0 and 42.8 dB for 50- and 25-GHz grids, respectively.
TL;DR: In this article, an orthogonal chirp division multiplexing (OCDM) technique for coherent optical communication is proposed, in which the CO-OCDM can effectively compensate the dispersion and is more resilient to fading and noise impairment than OFDM.
Abstract: In this paper, we propose an orthogonal chirp division multiplexing (OCDM) technique for coherent optical communication. OCDM is the principle of orthogonally multiplexing a group of linear chirped waveforms for high-speed data communication, achieving the maximum spectral efficiency (SE) for chirp spread spectrum, in a similar way as the orthogonal frequency division multiplexing (OFDM) does for frequency division multiplexing. In the coherent optical (CO)-OCDM, Fresnel transform formulates the synthesis of the orthogonal chirps; discrete Fresnel transform (DFnT) realizes the CO-OCDM in the digital domain. As both the Fresnel and Fourier transforms are trigonometric transforms, the CO-OCDM can be easily integrated into the existing CO-OFDM systems. Analyses and numerical results are provided to investigate the transmission of CO-OCDM signals over optical fibers. Moreover, experiments of 36-Gbit/s CO-OCDM signal are carried out to validate the feasibility and confirm the analyses. It is shown that the CO-OCDM can effectively compensate the dispersion and is more resilient to fading and noise impairment than OFDM.
TL;DR: A point-to-multipoint bidirectional mobile fronthaul system that combines efficient virtual tone-based DSP for phase recovery and carrier-frequency-offset estimation, signal degradations from beating among incoherent asynchronous UL signals are mitigated.
Abstract: Empowered by spectral aggregation and cell densification, future 5G mobile data networks pose a huge challenge to building next-generation mobile fronthaul systems with higher capacity, scalability, and energy efficiency. Under this circumstance, traditional solutions based on the Common Public Radio Interface or channel aggregation with digital signal processing (DSP) are not sufficient to support heterogeneous ubiquitous wireless access. In this paper, we demonstrate a point-to-multipoint bidirectional mobile fronthaul system. Wavelength division multiplexing plus frequency division multiplexing is applied to support independent asynchronous small cells. Intensity-modulation and direct-detection downlink (DL) as well as field-modulation and heterodyne-detection uplink (UL) are proposed. Combined with efficient virtual tone-based DSP for phase recovery and carrier-frequency-offset estimation, signal degradations from beating among incoherent asynchronous UL signals are mitigated. Proof-of-concept experiments are demonstrated where 20 and 16 80-MHz component carriers are transmitted over 25-km standard single-mode fiber for DL and UL, respectively. Less than 6% error vector magnitudes with 64-, 16-, and 4-ary quadrature amplitude modulation are obtained.
TL;DR: This paper proposes to use an MMSE-sorted QR decomposition (MMSE-SQRD)-algorithm-based MIMO decoder to efficiently eliminate the ICI in a high-speed SEFDM-based wavelength-division multiplexing (WDM) VLC system and establishes a quasi-multiple-input multiple-output (MIMO) model for SEF DM-based systems.
Abstract: A spectrally efficient frequency division multiplexing (SEFDM) modulation has been proposed to improve system spectral efficiency, particularly for bandwidth-limited visible-light communication (VLC) systems. It employs non-orthogonal subcarriers to achieve bandwidth savings at the expense of serious intercarrier interference (ICI); thus, complicated detectors are required at the receiver to extract signals from the ICI. In this paper, we carry out an analysis of SEFDM modulation and establish a quasi-multiple-input multiple-output (MIMO) model for SEFDM-based systems. Based on this quasi-MIMO system model, for the first time, we propose to use an MMSE-sorted QR decomposition (MMSE-SQRD)-algorithm-based MIMO decoder to efficiently eliminate the ICI in a high-speed SEFDM-based wavelength-division multiplexing (WDM) VLC system. Using the MMSE-SQRD decoder, the WDM VLC system at an aggregate data rate of 2.4 Gb/s is experimentally demonstrated over a 2-m indoor free-space transmission, and up to 20% of bandwidth savings is achieved compared with that of the orthogonal frequency-division multiplexing (OFDM). The results clearly validate the effectiveness of the proposed MMSE-SQRD detector for SEFDM-based spectrum-compressed VLC system.
TL;DR: The results of the allocation of RF channels to better exploit the available modulation bandwidth of commercial transceivers show that the uniformly spaced channel plan is bandwidth efficient but susceptible to interference.
Abstract: Analogue Radio over Fibre together with subcarrier multiplexing and wavelength division multiplexing is proven to be more cost-efficient when compared to CPRI fronthaul solutions. Furthermore, the results of the allocation of RF channels to better exploit the available modulation bandwidth of commercial transceivers show that the uniformly spaced channel plan is bandwidth efficient but susceptible to interference. The ITU-T G.692 plan results in much higher tolerance to interference but it is more bandwidth consuming. Finally, the proposed ‘mind the gap’ RF channel plan shows an acceptable compromise between bandwidth consumption and robustness against intermodulation interference.
22 May 2016
TL;DR: It is shown via computer simulations that the proposed scheme achieves considerably better error performance than the existing VLC-MIMO-OFDM systems due to its power efficiency and improved transceiver structure.
Abstract: In this paper, we propose a generalized light emitting diode (LED) index modulation scheme for multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) visible light communications (VLC) systems. The proposed scheme generalizes the LED index modulation concept by using the spatial multiplexing principle to transmit complex OFDM signals through VLC channels by separating these signals into their real-imaginary and positive-negative parts. The maximum a posteriori (MAP) estimator of the proposed scheme, which relies on quadratic programing (QP) problem, is presented for flat VLC channels. It is shown via computer simulations that the proposed scheme achieves considerably better error performance than the existing VLC-MIMO-OFDM systems due to its power efficiency and improved transceiver structure.
TL;DR: This study considers the downlink radio resource allocation for heterogeneous traffic in generalised frequency division multiplexing (GFDM)-non-orthogonal multiple access (NOMA) based heterogeneous cellular networks and shows that AGMA can achieve a sum-rate near to the global optimal solution, at the expense of more computational time.
Abstract: In this study, the authors consider the downlink radio resource allocation for heterogeneous traffic in generalised frequency division multiplexing (GFDM)-non-orthogonal multiple access (NOMA) based heterogeneous cellular networks. In this scheme, multiple number of users can be allocated on each subcarrier. Two types of traffic are considered, elastic and streaming. The problem of maximising the weighted sum-rate of elastic users is addressed subject to streaming users minimum rate in addition to subcarrier and transmit power constraints. This problem is a non-convex NP-hard optimisation problem. To solve this problem, the authors divide it into two subproblems, subcarrier allocation and power allocation then an iterative algorithm is proposed. Subcarrier allocation is updated by solving an integer linear program, where a successive convex approximation approach is adopted to transform the power allocation subproblem to a sequence of convex subproblems, using one of the three methods, successive convex approximation for low ComplExity, arithmetic-geometric mean approximation (AGMA) and difference of two concave functions to find the power allocation optimal solutions. Numerical experiments show that the proposed algorithms can improve the system performance. Furthermore, they show that AGMA can achieve a sum-rate near to the global optimal solution, at the expense of more computational time.
01 Dec 2016
TL;DR: A new FFT-based trellis receiver for multicarrier signals with nonorthogonal frequency spacing (spectrally efficient frequency division multiplexing, SEFDM) is proposed and the iterative version of demodulator is developed.
Abstract: A new FFT-based trellis receiver for multicarrier signals with nonorthogonal frequency spacing (spectrally efficient frequency division multiplexing, SEFDM) is proposed. It is based on FFT and max-log-MAP algorithm, which is adapted to work with frequency samples of received signal. The iterative version of demodulator is also developed. The performance of proposed iterative QPSK-SEFDM demodulation is comparable with the one of classic coded QPSK modulation while the spectral efficiency remains very high. The proposed algorithms can demodulate SEFDM signals with large number of subcarriers.
TL;DR: By using the non-orthogonal multiple access (NOMA) scheme, the system optimizes the performance of all users as a whole group and dynamically allocates the power resources between different users, such that the reception quality and reliability of the user group is significantly improved compared with current orthogonal frequency-division multiple access.
Abstract: We proposed to use the non-orthogonal multiple access (NOMA) scheme in 60-GHz-millimeter-wave radio-over-fiber systems, exploiting the power domain of signals to enable multiuser access, and improve the performance with users under different channel conditions. A DSP-based successive interference cancellation scheme is implemented in the receiver to remove the interference from other users. By this NOMA scheme, the system optimizes the performance of all users as a whole group and dynamically allocates the power resources between different users, such that the reception quality and reliability of the user group is significantly improved compared with current orthogonal frequency-division multiple access. To overcome the user number and security issue raised from NOMA, both orthogonal and NOMA are applied. A nonlinear conjugate gradient method is proposed in the power allocation updating process for fast convergence of the feedback system. With a centralized radio-over-fiber architecture, we enable the millimeter wave system with high-resource utilization rate and better approximation to end users with low cost. A 4-Gb/s downlink system serving three users using 60-GHz band is experimentally demonstrated and measured. The proposed scheme provides larger distance coverage, wider angle tolerance, and better shaded channel tolerance. Better reception quality and reliability are experimentally verified without reducing data rate or increasing transmission power.
TL;DR: This paper proposes a medium access control (MAC) protocol for vehicular PLC systems, where multiple nodes are competing for transmission over the direct current (dc) power line and consists of a distributed channel selection policy to arbitrate packet transmission across different channels and robustness against interference and noise.
Abstract: In-vehicle communications are emerging to play an important role in the continued development of reliable and efficient X-by-Wire applications in new vehicles. Since vehicle devices, sensors, and the electronic control unit (ECU) are already connected to power wires, the advancement of power line communications (PLCs) can provide a very low cost and virtually free platform for in-vehicle communications. In this paper, we propose a medium access control (MAC) protocol for vehicular PLC systems, where multiple nodes are competing for transmission over the direct current (dc) power line. The proposed protocol uses a combination of time and frequency multiplexing and consists of two key features: 1) a distributed channel selection policy to arbitrate packet transmission across different channels and provide robustness against interference and noise and 2) a distributed collision resolution algorithm to allow efficient nodes completion over selected channels. Specifically, the collision resolution algorithm is optimized with respect to the channel policy such that the success probability of transmission in each channel is maximized. Numerical results are also supplemented to validate the performance of the proposed protocol and provide useful guidelines for developing a robust contention-based MAC protocol for vehicular PLC systems.
TL;DR: In this article, a cladding-pumped six-core Erbium-doped fiber amplifiers (EDFAs) were demonstrated using two different pump coupling schemes: edge-coupled and side coupled, where a single multimode laser diode can be applied to pump all cores.
Abstract: We demonstrate cladding-pumped six-core Erbium-doped fiber amplifiers (EDFAs) using two different pump coupling schemes: edge-coupled and side-coupled pumping, where a single multimode laser diode can be applied to pump all cores. Using two in-line cladding-pumped EDFAs at the input and output of a 31-km coupled-six-core fiber, we realized 465-km space-division multiplexing and wavelength division multiplexing transmission in a recirculating loop and achieved a spectral efficiency of 18 bits/s/Hz. Through side-coupled pumping, the cladding-pumped six-core EDFA produced >18-dBm output power per core and had <6-dB noise figure across the C-band.
TL;DR: Compared with the polyphase coding and the discrete frequency coding waveforms, the PLFM waveform has a lower cross-correlation level and higher degrees of freedom.
Abstract: To separate the received signals in a multiple-input multiple-output (MIMO) radar, the transmitted signals should be orthogonal or have a low cross-correlation level. Some other properties, such as low autocorrelation sidelobes, high range resolution, and good Doppler tolerance are also desired. However, they are difficult to achieve simultaneously. In general, an improved criterion is at the cost of another degraded one. In this paper, we propose a piecewise linear frequency modulation (PLFM) waveform for the MIMO radar. The transmitted signals are pulse trains, including diversified subpulses, which are divided into three segments with controllable durations and bandwidths. The duration sequence of the second segment is obtained by the genetic algorithm to optimize the cross correlation. Theoretical analyses and numerical results are presented to illustrate the properties of the proposed PLFM waveform. Compared with the polyphase coding and the discrete frequency coding waveforms, the PLFM waveform has a lower cross-correlation level and higher degrees of freedom. The relationship of the bandwidths among different segments can be used to adjust the sidelobe peak and the main lobe width of the autocorrelation function.
01 Dec 2016
TL;DR: The proposed algorithm incorporates the effects of QoS and stochastic traffic, and studies the benefits of joint spatial- frequency multiplexing over the static frequency slicing approach, and sheds some light on the trade-offs between frequency and spatial multiplexed as well as betweenQoS and utilization.
Abstract: Wireless virtualization is a promising approach to foster innovation and prevent the ossification of wireless networks. Within a virtualized wireless network, multiple network slices, or virtual operators (VO), are co- hosted on the same physical infrastructure. A fundamental question in this environment is which multiplexing technique, TDMA, FDMA or SDMA, should be used to slice the network among the VOs. Another related question is how should the stochastic arrival process affect the slicing and QoS criteria. To answer these two questions, we study the problem of QoS-aware joint admission control and network slicing. Due to the NP- hardness of the problem, we approach it using a heuristic algorithm composed of three steps: spectrum allocation, admission control and spatial multiplexing. The proposed algorithm incorporates the effects of QoS and stochastic traffic. We study through simulations the benefits of joint spatial- frequency multiplexing over the static frequency slicing approach. Finally, our simulation results help shed some light on the trade-offs between frequency and spatial multiplexing as well as between QoS and utilization.
TL;DR: Various MUD techniques for SDMA-OFDM system are reviewed, which can provide high spectral efficiency and resistance from inter symbol interference and multiple users transmit their data simultaneously.
TL;DR: By utilizing the frequency plan, this work successfully transmit 24-20-MHz long-term evolution advanced (LTE-A) signals over 60-km single-mode fiber (SMF) without any penalties from the distortion and shows the transmission performance when transmitting larger number of IF carriers in the limited modulation bandwidth.
Abstract: Nowadays, there have been many research works on multiple-intermediate-frequency-over-fiber (multi-IFoF)-based mobile fronthaul link to accommodate explosive mobile data traffic. The performance of multi-IFoF transmission scheme is affected by fiber dispersion-induced second-order distortion in 1.5 μm. Thus, we derive an appropriate frequency plan to avoid the distortion. By utilizing the frequency plan, we successfully transmit 24- 20-MHz long-term evolution advanced (LTE-A) signals over 60-km single-mode fiber (SMF) without any penalties from the distortion. We also show the transmission performance when transmitting larger number of IF carriers in the limited modulation bandwidth so the penalties from the distortion are inevitable. We confirm that 72- 20-MHz LTE-A carriers can be transmitted over 30-km SMF within only 1.5-GHz modulation bandwidth.
TL;DR: The method reuses the data transmitter without any impact on data transmission and provides capability of in-service reflectometry measurements of fiber optic lines with 10-m spatial resolution and 1.0-dB fault detection sensitivity.
Abstract: In this paper, we describe an efficient method for monitoring fiber links utilizing sub-carrier multiplexing. By assigning a void sub-carrier frequency band for monitoring purposes, the method reuses the data transmitter without any impact on data transmission and provides capability of in-service reflectometry measurements of fiber optic lines with 10-m spatial resolution and 1.0-dB fault detection sensitivity. Its promising properties and performance enable potential application in emerging networks such as relatively short distance analogue mobile fronthaul.
TL;DR: In this paper, a new computationally efficient blind carrier frequency offset (CFO) estimator for multi-input multi-output orthogonal frequency division multiplexing systems is proposed and an enhanced CFO estimator is developed by introducing an additional one-step adjustment.
Abstract: In this paper, we propose a new computationally efficient blind carrier frequency offset (CFO) estimator for multi-input multi-output orthogonal frequency division multiplexing systems. A cost function is carefully designed and can be exactly expressed as the superposition of very few harmonically related cosine waves even with the effect of the noise. Using this property, the minimization of the designed cost function can be solved in a quite computationally efficient manner without any exhaustive grid search procedure. It is seen that the proposed estimator can achieve comparable estimation performance as existing competitors with substantially reduced computational burden. Moreover, in order to improve the estimation performance, we further develop an enhanced CFO estimator by introducing an additional one-step adjustment. We find that the enhanced estimator can attain almost the same estimation performance as the existing maximum likelihood estimator but with a lower order of computational burden. We provide both numerical results and theoretical performance analysis to corroborate the proposed studies.