Multi-band Orthogonal Frequency Division Multiplexing System Research Articles

Low-Voltage Low Noise Figure Down-Conversion Mixer for Band #1 of MB-OFDM System in 180 nm Complementary Metal Oxide Semiconductor Technology

Low-voltage design is a challenge for Gilbert cell-based mixers due to stacking transconductance and switching stage. This work addresses this issue by proposing a design of a low-voltage down-conversion mixer for band #1 of multiband orthogonal frequency division multiplexing (MB-OFDM) system in 180 nm complementary metal oxide semiconductor (CMOS) technology. The mixer is tuned at band #1 at RF frequency of 3.432 GHz and IF frequency of 264 MHz. The proposed mixer uses folded cascode connection of LO and RF in order to increase headroom and to reduce the DC supply voltage for low-voltage operation. Common gate configuration is used at RF transconductance stage to enhance the input bandwidth of the mixer. RF and LO ports are matched to 50 Ω using differential T and LC matching, respectively. The resistive source denegation technique is used to linearize transconductance with respect to the bias point. The common source stage is used at the IF port as a buffer cum matching circuit it. The simulation results of the mixer show the maximum conversion gain of 9.76 dB, 1 dB compression point (P1dB) of -16.25 dBm, the third-order input intercept point (IIP3) of -4.70 dBm, an SSB noise figure of 9.036 dB, and S11of -19.490 dB at the supply voltage of 1.2 V. Excluding off chip components, proposed mixer records an active area of 926.35 μm2.

Wideband ring mixer for band #1 of MB-OFDM systems in 180 nm CMOS technology

Abstract A wideband down conversion ring mixer is proposed for multi band orthogonal frequency division multiplexing (MB-OFDM) system in 180 nm CMOS technology. The mixer is essentially used in a heterodyne wireless receiver to enhance the selectivity of the system. Being a nonlinear system, the mixer dominates the overall performance of the system. The design of down conversion mixer is the most challenging part of a receive chain. Wideband impedance matching always remains a challenge in any radio frequency integrated circuit design. This paper presents the design of a ring mixer with high linearity, wideband impedance matching using differential resistive impedance matching and without using any DC bias. The proposed mixer is tuned for a frequency of 3.432 GHz of band 1 of the MB-OFDM system. Mixer core is based on the FET ring mixer topology. The mixer is implemented in 180 nm CMOS technology. The mixer achieves the minimum conversion loss of 10.49 dB, 1 dB compression point (P1) of 12.40 dBm, third order input intercept point (IIP3) of 12.01 dBm, a minimum SSB noise figure of 8.99 dB, and S 11 of less than -10 dB over the frequency range of 0 to 13.61 GHz . The layout of the mixer records an active area of 183.75 μm 2 .

Parameter estimation and channel reconstruction based on compressive sensing for ultra-wideband MB-OFDM systems

Multi-band orthogonal frequency-division multiplexing (MB-OFDM) is an important transmission technique for ultra-wideband (UWB) communication. One of the challenges for practical realization of these UWB MB-OFDM systems is the estimation of the channel. In UWB MB-OFDM, the channel can be modelled as sparse, and channel estimation (CE) based on compressed sensing (CS) can be used. However, the existing techniques all require prior knowledge of some channel parameters, which are not known in practice, e.g. the dictionary size, corresponding to the effective duration of the channel impulse response (CIR), and the sparsity of the CIR. Therefore, in this paper, we propose a CS-based channel parameter estimation method to estimate the dictionary size and the sparsity based on a pilot preamble of which the duration is shorter than the total duration of the CIR. Using the resulting parameter estimates, we reconstruct the CIR with the compressive sampling matching pursuit (CoSaMP) method. We show that the proposed algorithm is able to accurately estimate the sparsity and the dictionary size, and can effectively reconstruct the CIR for channels that are either based on a mathematical model or real, measured channels. Moreover, as the algorithm has acceptable complexity, the proposed method is suitable for practical use.

Analysis of UWB MB-OFDM Communication System through IEEE802.15.4a Channel Models using Matlab Simulink

This paper evaluates the performance of the UWB communication system with an accurate channel model using simulation. In real time a prototype model of UWB communication system is cost effective. This paper UWB Multiband-Orthogonal Frequency Division Multiplexing System is provided for various range of frequency. In various frequency range of IEEE 802.15.4a channel subgroup provides a several model. Ultra wideband frame work recurrence ranges from 2 to 10 GHz, and provides eight different models of channel for both Line-of-Sight (LOS) and No-line-of- Sight (NLOS) environment circumstances of both indoor as well as outdoor. The uniqueness of task group 4a Channel Models and UWB correspondence framework are confirmed and evaluated for numerous channel models.

Virtual Carrier-Assisted DD-MB-OFDM Schemes for UDWDM Metro-Access Networks With Improved Tolerance to Four-Wave Mixing

Virtual carrier (VC)-assisted multiband orthogonal frequency division multiplexing (MB-OFDM) schemes with improved tolerance to the four-wave mixing (FWM) effect in direct-direction ultradense wavelength division multiplexing metro-access networks are proposed and discussed. The best scheme is identified from a set of alternative schemes chosen with potential to increase the tolerance to the FWM effect in VC-assisted MB-OFDM systems. A data rate per band and per user of the metro-access network of 10 and 25 Gb/s is considered for band spacings of 3.125 and 6.25 GHz, respectively. With the proposed MB-OFDM schemes, increase of the maximum acceptable power launched into the fiber can be achieved. This increase translates into a similar power budget (PB) improvement. With band spacings of 3.125 GHz, a PB improvement of 3 dB is achieved, which enables to double the number of users served by the metro-access network or to extend the reach of the optical distribution network (ODN) by about 12 km. For a 6.25-GHz band spacing, a PB improvement exceeding 4 dB is achieved, enabling to double the number of users and simultaneously extend the ODN coverage by about 5 km.

Outage and BER analysis of dual-carrier modulation over frequency-selective Nakagami-m fading channels

PurposeThis paper aims to the increasing need for high-speed low-power data transmissions over frequency-selective fading channels has drawn attention to suggest dual-carrier modulation (DCM) for multiband orthogonal frequency division multiplexing (OFDM) transceivers for ultra wideband (UWB) wireless personal area network (WPAN).Design/methodology/approachUnder frequency-selective fading channel conditions, the decoder is not sufficient enough to decode the transmission bits of severely attenuated data tones. Hence, the authors suggest DCM for a multiband OFDM transceiver because of its multiple capability of providing both frequency diversity and coding gain. It also resulted in low bit-error-rate (BER) at a given signal- to-noise ratio when compared to conventional multiband OFDM system. To achieve an optimised BER, DCM transforms four re-ordered bits into two quaternary phase shift keying symbols and further transforms to two 16-quadrature amplitude modulation-like (16-QAM) symbols with a suitable mapping technique, and at the receiver end, they are decoded with maximum likelihood decision rule. After performing the transformation, the outage probability and average BER expressions are derived to analyse the system performance.FindingsDCM is suitable for high data rate transmission and is immune to frequency-selective fading. The outage and BER performance outstands over conventional multiband OFDM transceiver because of the inclusion of DCM mapping.Practical implicationsIt is widely used in WPANs such as high definition multimedia interface and wireless universal serial bus.Originality/valueThis paper derives novel closed-form outage probability and a tight upper bound on average BER expressions for DCM-based multiband OFDM UWB transceiver over frequency-selective Nakagami-m fading channels for any arbitrary value of m. For this, moment-generating function of sum of squared, independent and identically distributed (i.i.d.) Nakagami-m random variables are used. Further, the system performance is also validated for the case of exponential decaying power delay profile, and the simulation results are provided to check the accuracy of the derived expressions.

Theoretical Analysis of the Four-Wave Mixing Effect in Virtual Carrier-Assisted DD MB-OFDM Ultradense WDM Metropolitan Networks

A theoretical method (TM) to evaluate the four-wave mixing (FWM) power in multiband orthogonal frequency division multiplexing (MB-OFDM) ultradense wavelength division multiplexing (WDM) metropolitan networks using virtual carriers (VCs) and direct detection is proposed and validated numerically. It considers a band spacing of 3.125 GHz and 10-Gb/s data rate per band. A simplified TM (STM) to obtain the FWM power for MB-OFDM systems employing high-dispersion fiber is also proposed to relax the computation complexity. Both methods consider that FWM products generated from the mixing between two VCs and an OFDM band are dominant. Analytical expressions for the maximum allowed average power of the worst band (the band most impaired by FWM) are also derived. The TM and STM enable estimating the average power level per WDM channel corresponding to the threshold error vector magnitude (EVM) (threshold average power—TAP), where the threshold EVM is the maximum allowed EVM due to FWM, which induces a 2-dB EVM penalty to the EVM at the forward error correction threshold. Results show that, when a total data bit rate of 450 Gb/s is transmitted (nine WDM channels with five bands each) along the standard single-mode fiber (SSMF), the discrepancy between the numerical simulation-estimated and TM-estimated TAPs does not exceed 0.5 dB. By defining the upper bound of the power limit (UBPL) as the TAP obtained with 17 WDM channels, the discrepancy between the TM-estimated and STM-estimated UBPLs does not exceed 1 dB for transmission along up to 10 SSMF spans and for channel gaps up to 22.81 GHz.

EAM-based multiband OFDM systems incorporating PAPR reduction and SSII cancellation

Multiband orthogonal frequency division multiplexing (OFDM) subcarrier allocation is a good scheme to fully utilize the available bandwidth under the restriction of dispersion- and chirp-induced power fading in electro-absorption modulator (EAM)-based intensity-modulation-direct-detection (IMDD) OFDM system. In this paper, a modified Tone Reservation (TR) technique combined with subcarrier interleaving is proposed to reduce high peak to average power ratio (PAPR) while minimizing the penalty of subcarrier-to-subcarrier intermixing interference. In the experiment, by incorporating of these two techniques, the receiver sensitivity is improved by about 1.8dB when a 20Gbps OFDM signal transmitted along 100km long single mode fiber in an EAM-based multiband IMDD–OFDM system.

High Granularity Multiband OFDM Virtual Carrier-Assisted Direct-Detection Metro Networks

A direct-detection metropolitan (metro) network employing multiband orthogonal frequency division multiplexing (MB-OFDM) signals (MORFEUS network) is proposed. The MORFEUS network employs virtual carriers to assist the detection of each OFDM band. It represents a cost-effective network enabling high granularity and flexibility, while requiring a reduced receiver bandwidth. The MB-OFDM signal structure and their main constraints are presented. Each MB-OFDM metro node is described and discussed, with particular attention dedicated to the blocks required to insert and extract a given OFDM band of the MB-OFDM signal. Conceptual solutions for the MORFEUS insertion and extraction blocks are also proposed and discussed. The performance of a 42.8-Gb/s MORFEUS network is evaluated through numerical simulation, and the network operation design is optimized. The impact of the optical filtering effect due to band add/drop operations is assessed as well. These studies are accomplished for systems employing band selectors (BS) with different selectivity to assess the performance tolerance to interband crosstalk and in-band amplitude distortion. The studies are performed for three MORFEUS networks, with granularity of 2-, 3-, and 4-bands. A required optical signal-to-noise ratio (OSNR) of 24 dB is demonstrated in a 240-km-long MORFEUS network without optical filtering cascade effect for a bit error ratio of $10^{-3}$. This required OSNR level is achieved for the three networks with different granularity and for the two BS analyzed after suitable optimization of the MB-OFDM system parameters. Compared with an ideal MORFEUS network employing ideal rectangular BS, the analyzed networks present an OSNR penalty not exceeding 2.5 dB. A required OSNR penalty of 1 dB due to optical filtering cascade is obtained after six nodes with band filtering, for BS with a second order super-Gaussian shape.

A low complexity soft-output detection algorithm for 2×2 multiple-input multiple-output multiband-ofdm systems using dual carrier modulation

This paper presents a low complexity soft-output detection algorithm for 2×2 multiple-input multiple-output (MIMO) multiband-orthogonal frequency division multiplexing (MB-OFDM) systems using dual carrier modulation (DCM) or modified DCM (MDCM). By detecting each symbol pair of DCM or MDCM separately, the proposed detection algorithm reduces the complexity of the partial Euclidean distance (PED) calculation and the preprocessing complexity, which is the complexity of QR decomposition and channel ordering. This paper also proposes an efficient candidate list extension method for soft-output MIMO detection by using the calculated PEDs. Because the proposed algorithm has a low complexity and can also be implemented in a fully-pipelined hardware, the proposed algorithm is suitable for MB-OFDM systems requiring high speed hardware. The simulation results of applying the proposed algorithm to 2×2 MIMO MB-OFDM systems using DCM or MDCM show that the performance of the proposed algorithm has near soft-output maximum likelihood detection performance. The hardware complexity of the proposed algorithm is approximately 40% of that of the existing algorithm with similar performance.

Performance of multiband orthogonal frequency division multiplexing network in ultra wideband channels incorporating people shadowing and channel fading

Ultra wideband (UWB) systems transmit signals across a much wider frequency than conventional systems and are usually very difficult to detect. UWB systems tend to be useful for short-range indoor applications. However, because of the short duration of UWB pulses, it is easier to engineer extremely high data rates. In multi-band orthogonal frequency division multiplexing (MB-OFDM) architecture, designers gain flexibility, reduction in power consumption, high spectrum efficiency and cost. In the earlier study, people shadowing has been considered to model attenuation in a packet-level UWB channel model. However, in dense short-range indoor applications, the effect of scatterers, diffractors and reflectors cannot be ignored. This happens mostly when the transmit antenna is omni-directional. Compared with the earlier work which incorporated only shadowing effects, this study discusses a packet-level UWB channel model subject to both multipath fading and people shadowing, which can arise even in an indoor channel (e.g. inside a hall of dimensions ∼ 10 m), and is incorporated in an MB-OFDM system. The performance analysis of the link is made based on link throughput and delay in servicing packets. The numerical results show the relative effects of various fading distributions, viz., Rayleigh, Rician, Weibull and Nakagami, together with people shadowing on the MB-OFDM system.

Avoiding WIMAX Interference on Ultra Wide Band MB-OFDM System by Cognitive Radio

This paper considers the ECMA-368 standard based on Multiband Orthogonal Frequency Division Multiplexing (MB-OFDM) as an Ultra Wideband (UWB) system in the presence of interference from an IEEE 802.16 WiMAX systems operating at 3.5 GHz. Simulations are conducted following the standards and adopting the IEEE 802.15.3a channel model CM1. This paper shows that the system fails because of the WiMAX interference, in the absence of an interference avoidance or cancellation scheme. This paper exploits the channel information and the flexibility of non- contiguous Orthogonal Frequency Division Multiplexing (NC-OFDM) based cognitive radios to avoid coexistence interference between UWB and WiMAX systems. The proposed cognitive UWB system results in a significant gain and is compatible with minimum changes to the current system specifications. Index Terms— Coexistence interference, MB-OFDM, UWB, WiMAX

Unitary Differential Space-Time-Frequency Codes for MB-OFDM UWB Wireless Communications

In a multiple-input multiple-output (MIMO), multiband orthogonal frequency division multiplexing (MB-OFDM) ultra-wideband (UWB) system, coherent detection requires the transmission of a large number of symbols for channel estimation, thus reducing the bandwidth efficiency. For the first time, this paper proposes unitary differential space-time-frequency codes (DSTFCs) for MB-OFDM UWB communications, which increase the system bandwidth efficiency because no channel state information (CSI) is required. The proposed system would be useful when CSI is unavailable at the receiver, such as when the transmission of multiple channel estimation symbols is impractical or uneconomical. The coding and decoding algorithms for the proposed DSTFCs are then derived for both constant envelope modulation scheme, such as PSK (phase shift keying) and 4QAM (quadrature amplitude modulation), and multi-dimensional modulation scheme, such as DCM (dual carrier modulation). The paper also quantifies for the first time the diversity order of a DSTFC MB-OFDM system. Simulation results show that the application of DSTFCs can significantly improve the bit error performance of conventional differential MB-OFDM system (without MIMO), and even provide much better bit error performance than the conventional coherent MB-OFDM system (without MIMO) at high signal-to-noise ratios.

Performance evaluation of variable transmission rate OFDM systems via network source coding

Studies related to the network source coding have addressed rate-distortion analysis in both noiseless and noisy channels. However, to the best of authors’ knowledge, no prior work has studied network source coding in the context of orthogonal frequency division multiplexing (OFDM) systems. In addition, the system performance using network source coding schemes also remains unknown. In this article, we first propose two variable transmission rate (VTR) OFDM systems by utilizing network source coding schemes, and then evaluate the system performance of these two proposed VTR-OFDM systems. For the proposed VTR single-input single-output OFDM system, we employ the concept of a network with intermediate nodes to develop a 3-stage encoder/decoder, and the proposed encoder provides three different coding rates from 0.5 to 0.8. As for the proposed VTR multi-band OFDM system, two correlated sources are simultaneously transmitted using the multiterminal source coding schemes, and two sources are encoded by different coding rates from 0.25 to 0.5. Finally, compared with the traditional uncoded OFDM system, the proposed VTR-OFDM systems have at least 1 to 4 dB gain in signal-to-noise ratio to achieve the same symbol error rate in the additive white Gaussian noise channel.

Multi Band OFDM System Model and Its Performance Evaluation for UWB Communication

In this work multiband orthogonal frequency division multiplexing (OFDM) System is modeled and its performance evaluation is analyzed for ultra wide band (UWB) communication environment. Theoretical derivation for the average pairwise error probability (PEP) and Outage Probability are derived based on Saleh and Valenzuela fading model. In line with this, the impact of joint coding the information across subcarriers in the system performance is investigated. The link budget analysis is also computed and results are obtained in regard to the transmission range for indoor environments. Moreover, average coded bit error rate achieved from convolutional codes over the system is computed and supported with computer simulations for all UWB channel conditions.

Performance of MB-OFDM network in a UWB channel under people shadowing and channel fading statistics

Ultra Wideband (UWB) systems transmit signals across a much wider frequency than conventional systems and are usually very difficult to detect. Due to the extremely low emission levels currently allowed by regulatory agencies, UWB systems tend to be useful for short-range and indoor applications. However, due to the short duration of the UWB pulses, it is easier to engineer extremely high data rates. Conventional Orthogonal Frequency Division Multiplexing (OFDM) technology is used subject to the minimum bandwidth requirement of the regulations. By turning to Multiband OFDM (MB-OFDM) architecture, designers gain the flexibility, power consumption, high spectral efficiency and costs needed to make UWB come to life. A packet-level UWB channel model is incorporated in MB-OFDM system and the performance of the link is determined on the basis of link throughput and delay in servicing the packets.

The Error Performance and Fairness of CUWB Correlated Channels

Abstract The symbol period becomes smaller compared to the channel delay in multiband orthogonal frequency division multiplexing (MB-OFDM) cognitive ultra wideband (CUWB) wireless communications, the transmitted signals experiences frequency-selective fading and leads to performance degradation. In this paper, a new design method for space-time trellis codes in MB-OFDM systems with correlated Rayleigh fading channels is introduced. This method converts the single output code symbol into several STTC code symbols, which are to be transmitted simultaneously from multiple transmitter-antennas. By using Viterbi optimal soft decision decoding algorithm, we investigate both quasi-static and interleaved channels and demonstrate how the spatial fading correlation affects the performance of space–time codes over these two different MB-OFDM wireless channel models. Simulation results show that the performance of space–time code is to be robust to spatial correlation. When the system bandwidth increases, the long term fairness quality will gradually become better and finally converges to 1.

Multilayer Dual-Band Bandpass Filter in Low-Temperature Co-Fired Ceramic Substrate for Ultra-Wideband Applications

In this paper, we propose a new multilayer dual-band bandpass filter in a low-temperature co-fired ceramic (LTCC) substrate for ultra-wideband (UWB) applications. This bandpass filter consists of two wideband bandpass filters and matching circuits. It is for UWB applications, which use the band group 1 (3.168-4.752 GHz) and the band groups 3 and 4 (6.336-9.504 GHz) of multiband orthogonal frequency-division multiplexing systems. The basic characteristics of the bandpass filter are simulated with a circuit simulator and an electromagnetic simulator. We also verify the effectiveness of the presented filter through experiments using LTCC technologies. The measured results of the fabricated filters agree well with the simulated results, and we obtain the good wide-passband characteristics with the desired notch band. The insertion losses are less than 2.5 dB in the wide passbands, which satisfies the target characteristics. Moreover, out-of-band attenuation performances almost satisfy the target characteristics: for instance, the attenuation level is higher than 33 dB from 0.8 to 2.17 GHz, 17 dB from 2.4 to 2.48 GHz, and 26 dB from 5.15 to 5.35 GHz. The fabricated filter has a size of 7.5 × 3.8 × 0.386 mm3.

Effects of MB-OFDM System Interference on the Performance of DS-UWB

So far, two ultrawideband (UWB) standards have been proposed as high-speed physical technologies for next-generation wireless personal area networks (WPANs). These standards are based on multiband orthogonal frequency-division-multiplexing (MB-OFDM) UWB or direct-sequence UWB (DS-UWB). However, because of the withdrawal of the plan for a unique standardization process by the IEEE 802.15.3a task group (TG3a), these two technologies will coexist in the future. In this context, this correspondence provides a performance analysis of DS-UWB communication in the presence of MB-OFDM interfering transmissions, where the channel is modeled through the IEEE 802.15.3a standard model, and the network topology for the MB-OFDM interferers is based on a clustered structure as per the IEEE 802.15.3 descriptions for medium access control (MAC) and physical layer specifications for high-rate WPANs. The DS-UWB system performance is assessed in terms of bit error rate (BER). Specifically, an analytical expression for the average BER is derived, conditioned on the channel impulse response using a pulse collision model. Numerical and simulation results are provided and compared for different coexistence scenarios.

Impact of WiMAX interference on MB-OFDM UWB systems: analysis and mitigation

This paper presents an analysis of the performance of the multiband orthogonal frequency division multiplexing (MB-OFDM) system for ultra wideband (UWB) communication in the presence of interference from IEEE 802.16 WiMAX systems operating in the 3.5 GHz band. We present an exact analysis of the uncoded bit error rate (BER) of the MB-OFDM system, based on Laplace transform techniques. We also present a simple Gaussian approximation for the WiMAX interference, and establish its relative accuracy and usefulness by means of comparison with the exact analysis and simulations. Such a Gaussian approximation is especially useful for simplified performance analysis, as well as for the design of interference mitigation techniques. Motivated by the Gaussian approximation, we propose a simple two-stage interference mitigation technique for coded MB-OFDM transmissions, consisting of interference spectrum estimation during silent periods followed by appropriate bit metric weighting during Viterbi decoding. We compare parametric and non-parametric spectrum estimation techniques for various scenarios of interest. In the presence of WiMAX interference, the two-stage interference mitigation provides substantial gains in performance in return for modest increases in complexity and without requiring any modifications to the MB-OFDM transmitter or signal structure.