Adjacent Channel Interference Research Articles

Performance And Interference Analysis of 802.11G Wireless Network

This paper mainly presents Access Point s’ (APs’) performance and co-channel, adjacent channel interference according to 802.11g standard. Firstly, our study illustrates the performance of one AP, including its coverage performance, load-carrying properties and fairness. Next we propose the details about co-channel, adjacent channel interference which should be paid attention to in deploying network services. Then, performance analyses are evaluated by simulation and real test for a dense wireless network. Our contribution is that the co-channel, adjacent channel interference analysis, the simulation and test results can be the basis offered to network operators

Resource block Filtered-OFDM for future spectrally agile and power efficient systems

Spectrum sharing is a common paradigm in future communication systems and a spectrally agile baseband waveform with minimal out-of-band emissions is a critical component. In this paper, we propose a new multicarrier modulation technique, called resource block Filtered-OFDM (RB-F-OFDM) and present the transceiver design. This waveform can be used over channels with non-contiguous spectrum fragments and exhibits very low adjacent channel interference, which is required for cognitive radio systems with multi channel carrier aggregation capabilities. As such, regulatory based very stringent adjacent channel leakage ratio (ACLR) and adjacent channel selectivity (ACS) requirements can be met. We show that the transceiver complexity may be reduced by utilizing an efficient polyphase implementation that is commonly used in the filter bank multicarrier (FBMC) modulation. In addition, some efficient peak-to-average power ratio (PAPR) reduction techniques can be naturally applied. The new design is backwards compatible with legacy OFDM based systems. Simulation results to evaluate the performance, including measured bit error rate (BER) in multipath channels, are provided.

Iterative Decoding of Iterative Clipped and Filtered OFDM Signal

A communication system with non-linear power amplifier (PA) is considered. We introduce three major performance criteria of the system: (i) power efficiency of the PA, (ii) spectral purity of the transmitted signal expressed by adjacent channel interference, and (iii) transmission performance expressed by mutual information or symbol error rate. In order to fulfill the first two criteria it is proposed to use iterative clipping and filtering (ICF) at the transmitter together with low input back-off, while the third criterion is obtained by modified iterative receiver (MIR). The proposed MIR is based on the well-known iterative receiver, but with ICF in the feedback path. The obtained results show that the proposed system is better than its competitors when considering the three performance criteria together. The analysis and results are focused on OFDM; however, the proposed approach may be applied to single carrier.

Spectrum Sharing Model for Coexistence between High Altitude Platform System and Fixed Services at 5.8 GHz

This paper sheds the light on coexistence and sharing between high altitude platform system (HAPS) and Fixed Services (FS) as a recently critical issue due to the spectrum shortage. International Telecommunications Union Radiocommunications sector (ITU-R) allocated the 5850-7075 MHz band for the operation of HAPS along with existing FS services. Therefore, coexistence and sharing requirements like separation distance and frequency separation coordination must be achieved in terms of both co-channel and adjacent channel frequencies. The interference analysis mode based on the spectrum emission mask (SEM) is applied in the mentioned band to extract the required frequency separation to protect adjacent channel interference. Also interference to noise ratio (INR) as standard interference criteria is utilized.

Improvement of Memory Effects and ACPR of Power Amplifiers in CDMA Cellular Mobile and OFDM WLAN Transmitters

In this article, improvement of the memory effects and adjacent channel interference introduced by the nonlinearity of the power amplifier in the both Code division multiple access (CDMA) and Orthogonal frequency division multiplexing based (OFDM) transmitters is evaluated through Feedforward linearization method. For CDMA system, more than 17.27 dB increasing in OIP3 is and at least 25 dB improvement in adjacent channel power ratio (ACPR) is obtained. For OFDM system, achieved improvement through Feedforward linearization method is at least 39.03 dB in third output intercept point (OIP3 ), more than 26.6 dB in ACPR and 5.44 dB in peak-to- average ratio. It is observed that the designed Feedforward circuit can efficiently improve the nonlinearity caused by memory effects and saturation of the power amplifiers of CDMA cellular mobile telephony and OFDM wireless local area network (WLAN) transmitters.

Modeling of Adjacent Channel Interference in Heterogeneous Wireless Networks

This letter proposes a new model for the aggregate adjacent channel interference (ACI) received from nearby terminal stations (TSs) of heterogeneous wireless networks. It is well known that lognormal distribution approximates the aggregate received signal, but we found that it does not perform well for ACI-modeling among coexisting TSs. We propose a weighted sum of lognormals-based approximation (WSLA) where the probability density function (PDF) of the aggregate ACI appears in the form of a weighted sum of lognormals. The closed-form downlink outage probabilities with both lognormal approximation and WSLA are also derived. Through simulations, we demonstrate that the proposed approximation outperforms the lognormal one. The WSLA can also be applied to a dual slope channel model and extended to model the aggregate interference in inter-cells or sensor networks.

Shaping Spectral Leakage: A Novel Low-Complexity Transceiver Architecture for Cognitive Radio

In this article, we propose a transceiver architecture based on orthogonal frequency-division multiplexing (OFDM) with transmit and receive windowing to reduce spectral leakage and reject adjacent channel interference (ACI). The transceiver enables the utilization of unused subbands in a fragmented spectrum with low complexity, which may be used in cognitive radio systems. We first show a multicarrier modulation (MCM) framework and the implementation of transmit and receive windowing. The intersymbol interference (ISI) resulting from receive windowing with a multipath channel is illustrated, and the performance of the presented transceiver architecture is evaluated and compared with several other MCM techniques. The results show that windowing offers a simple transceiver architecture with acceptable performance and is well suited for cognitive radio scenarios with noncontiguous spectrum fragments. Its performance can be further improved by using more advanced receivers.

Protection Ratio and Antenna Separation for DVB—T/LTE Coexistence Issues

This paper concerns the analysis of adjacent channel interference of the 3GPP Long Term Evolution (LTE) E-UTRA (Evolved Universal Terrestrial Radio Access) mobile systems into Digital Video Broadcasting - Terrestrial (DVB-T) systems. The simulated performance of both systems allows us to define recommendations for minimizing the interference effects. The subjective quality of the received TV signal has been evaluated experimentally in terms of picture failure (PF). We also investigated the importance of the selection of suitable Spectral Emission Masks (SEMs) of the LTE downlink transmission. Results show that, by using the ECC 148 SEM, both the protection ratio and the minimum distance between LTE towers and DVB-T receivers can be significantly decreased.

웨이블릿 OFDM 시스템과 FD-OFDM 시스템 성능 비교 분석

본 논문에서는 웨이블릿 OFDM (Orthogonal Frequency Division Multiplexing) 및 FD-OFDM(Frequency Diversity OFDM) 시스템과 일반 OFDM 시스템의 성능을 비교 분석 한다. 푸리에 변환에 기반하는 일반 OFDM방식과는 달리 웨이블릿 OFDM 방식은 웨이블릿 변환을 사용하며, CDM (Code Division Multiplexing)과 OFDM의 중간적인 특성을 통해 심볼간 간섭을 효과적으로 제거할 수 있으며 채널간 간섭 역시 최소화 할 수 있다. FD-OFDM 방식의 경우, 각 병렬 브랜치에 입력된 심볼들이 직교 시퀀스로 곱해진 뒤 모든 부반송파에 분배되고, 각 부반송파는 주어진 프레임에서 각 병렬 브랜치의 심볼 조각들의 합의형태로 이루어진 정보를 전달한다. FD-OFDM의 한 부반송파 내에 포함된 모든 심볼들은 직교 시퀀스에 의해 구별되며, 간섭에 강하며 주파수 다이버시티 특성을 가진다는 장점을 지닌다. 협대역 간섭과 하모닉 잡음 환경에서 BER (Bit Error Rate) 성능을 통해 시스템 간 성능 비교 분석을 진행하였으며, 이를 통해 웨이블릿 OFDM과 FD-OFDM의 성능이 일반 OFDM보다 간섭에 대해 강건하고 특히 하모닉 노이즈 환경에서는 웨이블릿 OFDM이 가장 강건한 특성을 보이는 것을 알 수 있다.

XCHARM: A routing protocol for multi-channel wireless mesh networks

Recent experimental results have pointed out the impact of physical layer multi-path fading and co-channel interference as the key factors influencing packet delivery among mesh routers (MRs) in wireless mesh networks. In addition, in a multi-channel environment, there exists significant power spectral overlap among channels used by MRs, leading to adjacent channel interference. In this paper, a cross-layer multi-radio, multi-channel routing protocol, XCHARM, is proposed in which the key contribution is the selection of the next hop, channel and transmission rate based on fading and interference concerns. The key features of our proposed protocol are as follows: (i) Routes are chosen based on the availability of channels that support high data rates, exhibit acceptable interference levels and long term resilience to fading related losses, (ii) The path latency is analytically calculated in advance for the candidate routes, accounting for channel induced errors, link layer contention, forward error correcting (FEC) codes, and the allowed data rates over the chosen channels, (iii) The route maintenance is performed by first attempting to identify and correct the point of failure before undertaking a global recovery action. An extensive performance evaluation, spanning the network, link and physical layers, reveals the benefits of adopting our cross-layer routing solution for wireless mesh networks.

Adaptive HPA Linearization Technique for Practical ATSC DTV System

In the digital television (DTV) broadcasting system, high power amplifier (HPA) is the most essential device to expand the service availability and coverage. However, as the input power level of HPA increases, the HPA is driven into the saturation mode and HPA output signal suffers nonlinear distortion. HPA nonlinearity is potentially responsible for adjacent channel interference and inter-symbol interference (ISI). To prevent these negative effects, digital pre-distortion (DPD) is one of the most widely used techniques for the HPA linearization. In order to estimate the HPA nonlinearity, DPD technique requires a feedback signal, which needs to be appropriately down converted and digitized from HPA output. However, since the feedback signal might be generally influenced by offset error, it is important to reduce the offset error in order to improve HPA linearization. In this paper, an adaptive DPD technique based on iterative look-up table (LUT) update and adaptive acquisition is proposed. The proposed DPD technique is validated on the advanced television systems committee (ATSC) terrestrial DTV broadcasting system by computer simulation and laboratory test.

Improvement of Optically Generated Adjacent Channel Interference in RoF Systems

The optically generated adjacent channel interference (O-ACI) issue in the wavelength-reuse multi-channel radio-over-fiber systems is first studied. It is generated by the re-modulation of a downlink optical signal, which is already modulated by the downlink microwave signal. A carrier amplitude-phase-control double sideband modulation is proposed and experimentally demonstrated to improve the O-ACI in such systems. By tuning the bias voltage of the main modulator of the dual parallel Mach-Zehnder modulator, the amplitude and phase of the optical carrier are controlled to improve the O-ACI. Experiments show that the O-ACI in wavelength-reuse multi-channel WIFI-over-fiber system is reduced for 8 dB and the power penalty due to the O-ACI is improved by at least 5 dB when EVM is 6%.

Resource‐efficient and scalable solution to problem of real‐data polyphase discrete Fourier transform channelisation with rational over‐sampling factor

The study describes the results of research carried out into the design of a parallel and resource-efficient solution to the real-data polyphase discrete Fourier transform (DFT), or PDFT. The solution is able to exploit both the real-valued nature of the data and the parallel processing capabilities of the computing technology - assumed to be a field-programmable gate array - to yield a solution with a low size, weight and power requirement. A parallel computing architecture has been devised, based upon batch processing, whereby pipelined operation of the polyphase filter bank (PFB) is achieved using shared resources and pipelined operation of the real-data DFT using the resource-efficient regularised fast Hartley transform (RFHT). The PFB outputs are appropriately re-ordered for input to the RFHT by means of a suitably defined finite state machine. The resulting design, which includes a flexible up-sampling capability (with rational over-sampling factor) to address the problem of adjacent channel interference, trade-off time complexity against space complexity in order to satisfy the associated timing constraints. The solution is also scalable, in terms of the number of channels, so that it might be easily adapted, for new or multiple applications, at minimal re-design effort and cost.

Protection ratios for ATSC digital TV receivers

The Federal Communications Commission (FCC) planned the DTV Service for the United States in 1996 based upon laboratory measurements of the prototype ATSC receiver, establishing Protection Ratios for Co-Channel Interference (CCI) and Adjacent Channel Interference (ACI). Based on the available data it concluded that the UHF Taboos for analog TV were not applicable to ATSC receivers. Charles Rhodes has previously reported on laboratory tests of ATSC commercially available receiving devices against multiple strong radio broadcast signals in the FM Band, 88- 108 MHz. The results of laboratory tests of ATSC receiver's ability to reject interference from unwanted ATSC signals are reported.

A Multiband Mobile Analog TV Tuner SoC With 78-dB Harmonic Rejection and GSM Blocker Detection in 65-nm CMOS

A 48–885–MHz ultralow-cost high-performance mobile analog TV (MATV) tuner with an improved harmonic rejection design algorithm achieves 5.5 dB/4.5 dB noise figure at VHF and UHF bands, respectively, and adjacent channel interference (ACI) <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm N}+1/{\rm N}+2$</tex></formula> performance of 24/29 dB. A harmonic rejection mixer (HRM) with a tracking filter (TF) scheme employing three external inductors, one for each TV band, achieves better than 78/83-dB harmonic-rejection for the VHFI/VHFIII bands. A single LC-tank VCO with a programmable divider that has a 50% duty cycle correction scheme covers the entire TV band with accurate LO phases. A digital automatic gain control (AGC) scheme detects the presence of ACI and/or GSM burst-mode blockers through an RF wideband peak detector (WBPD) and adjusts the receiver gain for optimum dynamic range. The RF tuner is fabricated in 65-nm CMOS technology with silicon area of only 1.25 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{mm}^{2}$</tex> </formula> and draws 37/19 mA for analog TV and FM radio receiver modes, respectively.

On co-channel and adjacent channel interference mitigation in cognitive radio networks

Cognitive radio (CR) is an emerging wireless communications paradigm of sharing spectrum among licensed (or, primary) and unlicensed (or, CR) users. In CR networks, interference mitigation is crucial not only for primary user protection, but also for the quality of service of CR user themselves. In this paper, we consider the problem of interference mitigation via channel assignment and power allocation for CR users. A cross-layer optimization framework for minimizing both co-channel and adjacent channel interference is developed; the latter has been shown to have considerable impact in practical systems. Cooperative spectrum sensing, opportunistic spectrum access, channel assignment, and power allocation are considered in the problem formulation. We propose a reformulation–linearization technique (RLT) based centralized algorithm, as well as a distributed greedy algorithm that uses local information for near-optimal solutions. Both algorithms are evaluated with simulations and are shown quite effective for mitigating both types of interference and achieving high CR network capacity.

A novel measurement-based approach for modeling and computing interference factors for wireless channels

Wireless communication technologies divide their available spectrum into pre-defined channels. Some wireless technologies, such as the IEEE 802.11b/g, define their channels in such a way that adjacent channels share the spectrum. When two distinct channels share some part of their spectrum, simultaneous transmissions on these channels cause what is known as the adjacent channel interference. For problems that consider adjacent channel interference, such as the channel assignment problem for multi-channel wireless mesh networks, we need a model that quantitatively describes adjacent channel interference. The interference factor is a concept defined to quantify the amount of the overlap, hence the interference, between two wireless channels. Analytical and experimental methods have been proposed in the literature to define the interference factors among channels of a wireless technology. In this article, we propose a physical-layer-measurement-based, technology-independent and generic approach that is capable of determining interference factors between the channels of a wireless technology and also between the channels of two different wireless technologies, such as IEEE 802.11 and IEEE 802.15.4. We also report our measurement results for interference factors among 802.11b DSSS channels and between 802.15.4 and 802.11b channels. Our results show that our approach is practical, accurate and generic enough to compute the interference factors of radio channels belonging to various wireless communication technologies.

Adjacent Channel Interference Cancellation Using Orthogonal Precoding for Fractional Sampling OFDM Receiver

To achieve diversity with a single antenna, fractional sampling has been proposed. The imaging component of a desired signal must be transmitted by increasing the baseband filter bandwidth. This paper proposes and evaluates a system in which the imaging component is transmitted on the adjacent channel to the desired signal. The adjacent channel interference is cancelled by the precoding generated based on the basis of the channel state information of all the terminals. In this paper, the performance with perfect feedback and limited feedback is evaluated. Numerical results obtained through computer simulation show that the proposed scheme with a 6 bit random codebook for QPSK modulation improves the performance compared with that with the conventional scheme in the low $$E_b/N_0$$ region.

Derivation of Probability Density Function of Signal-to-Interference-Plus-Noise Ratio for the MS-to-MS Interference Analysis

This paper provides an analytical derivation of the probability density function of signal-to-interference-plus-noise ratio in the scenario where mobile stations interfere with each other. This analysis considers cochannel interference and adjacent channel interference. This could also remove the need for Monte Carlo simulations when evaluating the interference effect between mobile stations. Numerical verification shows that the analytical result agrees well with a Monte Carlo simulation. Also, we applied analytical methods for evaluating the interference effect between mobile stations using adjacent frequency bands. The analytical derivation of the probability density function can be used to provide the technical criteria for sharing a frequency band.

Available Channel Measurement in TV Whitespace with Adjacent Channel Interference

When using the sharing spectrum with others communication system, the most important thing is considering about harmful interference from unlicensed to licensed systems. With TV-band also, the digital television (DTV) can tolerate the interference from other system with their threshold and sharing spectrum regulations can guarantee the interference between communications system was characterized in Federal Communications Commission (FCC) 10-174 and Advanced Television Systems Committee (ATSC). This paper provides an interference analysis to verify a probability of interference between TV band devices and DTV system in adjacent TV channel. Besides, the combination of using Spectrum Engineering Advanced Monte Carlo Analysis Tool (SEAMCAT) will propose the criterion to get the level of harmful interference by another wireless system with specified transmission and geo-location arrangement. 