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Showing papers on "Co-channel interference published in 2006"


Patent
03 Mar 2006
TL;DR: In this article, a wireless communications signal is received within a frequency band and a desired component and an undesired interference component are identified, and at least some of the identified frequencies of the interference component of the signal are attenuated to generate an interference attenuated frequency domain signal.
Abstract: Methods of reducing interference in wireless communications in a communications system are provided. A wireless communications signal is received within a frequency band. The wireless communications signal includes a desired component and an undesired interference component. The interference component may be caused by, for example, communications by another component of the communications system using frequencies in the frequency band. The received communications signal is converted to a frequency domain representation. Frequencies of the interference component of the frequency domain signal are identified. At least some of the identified frequencies of the interference component of the frequency domain signal are attenuated to generate an interference attenuated frequency domain signal. The interference attenuated frequency domain signal is converted to an interference attenuated time domain signal.

70 citations


Proceedings ArticleDOI
11 Dec 2006
TL;DR: This work proposes an iterative way for reducing the intercell interference: The Turbo Base-Station Cooperation, and results show remarkable gains, especially in the presence of a strong interferer.
Abstract: Interference cancellation is an important issue since the coverage and capacity in the uplink are mainly interference limited. The interference from the own cell can be mitigated by multiuser detection. However, there does not exist a powerful interference cancellation technique for the interference from neighboring cells, the intercell interference. This work proposes a technique for combating the intercell interference. Since base-stations in wireless systems are connected through a backbone network, we propose the exchange of information through the network between the base-stations, in order to help each other in the detection of the signals. We present several strategies how this could be performed. Especially, we propose an iterative way for reducing the intercell interference: The Turbo Base-Station Cooperation. Simulation results show remarkable gains, especially in the presence of a strong interferer.

65 citations


Patent
30 Dec 2006
TL;DR: In this paper, the interference characteristics of at least one interferer in the presence of interference in an RF communications channel and selectively perform one or more adaptation mechanisms for adjusting properties of a communications protocol based on the interferer's interference characteristics are analyzed.
Abstract: Various embodiments directed to a radio frequency (RF) environment aware wireless communication device to analyze interference characteristics of at least one interferer in the presence of interference in an RF communications channel and to selectively perform one or more adaptation mechanisms for adjusting properties of a communications protocol based on the interference characteristics of the at least one interferer. The interferer may comprise a non-communicating device (e.g., microwave oven) or a communicating device (e.g., baby monitor, cordless phones, Bluetooth device, etc.) operating within or in the vicinity of a wireless network. The adaptation mechanisms may comprise contention window control to backoff and defer transmission according to a contention window and to leave a backoff counter of the contention window unchanged if the interference is determined to be non-802.11 interference. The adaptation mechanisms may comprise aggressive transmission to transmit over the interference. Other embodiments are described and claimed.

46 citations


Journal ArticleDOI
Yeliz Tokgoz1, B.D. Rao
TL;DR: This paper derives a compact, easily computable closed form outage probability expression in the form of finite sums that allows for simpler and faster analysis of various MIMO configurations.
Abstract: In this paper, we analyze the performance of the uplink of multi-cellular MIMO systems in flat Rayleigh fading. There is co-channel interference from users within the same cell as well as from other cell users. I The channel model includes lognormal shadowing and path loss along with power control, resulting in a statistical model for user powers. Consistent with practical scenarios, the co-channel interference is categorized into two groups: intracell interference from users within the same cell as the desired user and intercell interference from outer cell users. We derive a compact, easily computable closed form outage probability expression in the form of finite sums. This expression allows for simpler and faster analysis of various MIMO configurations. It has been shown that using antennas on the receiver side results in better performance, since transmit diversity does not combat interference from same cell users.

41 citations


Proceedings ArticleDOI
01 Nov 2006
TL;DR: In this paper, the authors present measurements of radio interference using "Ambient Node" sensor nodes and show that the interference caused by transmissions on adjacent bands can influence the data delivery considerably.
Abstract: This paper presents measurements of radio interference using "Ambient ?Node" sensor nodes. By varying distances and frequencies we get a measure of the interference caused by transmissions on adjacent bands. Our observations show that adjacent spectrum interference influences the data delivery, considerably. Channels should be separated in the spatial or in the frequency domains if interference is to be avoided. In addition, the distance to simultaneous transmitters and the number of simultaneous transmissions are highly correlated with channel spacing. Therefore, channel spacing can be adjusted according to spatial distances so that multiple concurrent transmissions can be performed without interference. We also give proposals for further investigation on the usage of this correlation that are relevant to the design of future multi-channel protocols.

39 citations


Proceedings ArticleDOI
25 Apr 2006
TL;DR: Using the post- processing capability of a software GPS receiver, CW interference is detected and characterized by passing the GPS signal and the interference through the correlator, and the existence and characterization of the existing interference is determined.
Abstract: Narrowband interference can severely degrade the performance of GPS receivers. Different narrowband interference suppression techniques also degrade this performance correspondingly. Detecting the presence of interference and then characterizing it can lead to its removal. Knowledge that can be useful is: the location of the source or direction of arrival of the interference (spatial-directional characteristics), the time specification and frequency and power of the interference (temporal-spectral characteristics). Our focus in this work is on the second type. Using the post- processing capability of a software GPS receiver, CW interference is detected and characterized. This is achieved by passing the GPS signal and the interference through the correlator. After correlation, using the definition of carrier to noise density ratio (C/No), a mathematical expression for C/No is given in which the temporal and spectral parameters of interference are found. Then, using the conventional definition of C/No as the squared mean of the correlator output divided by its variance, the actual C/No is calculated. Finally comparing these two values and considering the structure of the GPS C/A code, the existence and characterization of the existing interference is determined.

38 citations


Proceedings ArticleDOI
01 Sep 2006
TL;DR: This paper proposes successive interference cancellation (SIC) for compensating the frequency offset in the uplink OFDMA systems and the proposed algorithm is shown to eliminate the interference and has a manageable complexity.
Abstract: Similar to OFDM systems, OFDMA systems also suffer from frequency mismatches between the receiver and the transmitter. However, the fact that each uplink user has a different frequency offset makes the compensation more challenging than that of OFDM systems. This paper proposes successive interference cancellation (SIC) for compensating the frequency offset in the uplink OFDMA systems. A decorrelator is used to remove the inter-carrier interference (ICI) within a user's signal and successive cancellation is applied to mitigate the multi access interference (MAI) arising due to the frequency difference among uplink users. The proposed algorithm is shown to eliminate the interference and has a manageable complexity.

38 citations


Journal ArticleDOI
TL;DR: This letter investigates the outage performance of multiple-input multiple-output (MIMO) maximal ratio combining (MRC) systems with unequal-power co-channel interference (CCI) and presents closed-form expression for the outage probability.
Abstract: In this letter, we investigate the outage performance of multiple-input multiple-output (MIMO) maximal ratio combining (MRC) systems with unequal-power co-channel interference (CCI). Closed-form expression for the outage probability is presented. Our results are applicable to the MIMO MRC systems with arbitrary numbers of transmit and receive antennas.

34 citations


Journal ArticleDOI
TL;DR: This paper studies the performance of multiple-input-multiple-output (MIMO) systems with optimum combining in the presence of both co-channel interference (CCI) and noise and derives exact results on the cumulative distribution function (CDF) of the output signal-to-interference-plus-noise ratio (SINR) from this MIMO optimum combining scheme.
Abstract: This paper studies the performance of multiple-input-multiple-output (MIMO) systems with optimum combining in the presence of both co-channel interference (CCI) and noise. We assume that both desired and CCI users are subject to Rayleigh fading and allow the number of CCI users to be arbitrary and their short-term average powers to be non-identical. Given these assumptions, we derive exact results on the cumulative distribution function (CDF) of the output signal-to-interference-plus-noise ratio (SINR), or equivalently, the outage probability of this MIMO optimum combining scheme. Finally, we present and discuss some numerical examples to validate our analytical expressions and to show the effect of CCI on the performance of MIMO optimum combining systems

33 citations


Proceedings ArticleDOI
11 Dec 2006
TL;DR: This work determines exact closed-form expressions for the outage probability of multiple-input/multiple-output systems in Rayleigh fading with maximal ratio diversity combining and co-channel interference and indicates that, for a fixed total interference power, system performance degrades when there are dominant interferers.
Abstract: We determine exact closed-form expressions for the outage probability of multiple-input/multiple-output systems in Rayleigh fading with maximal ratio diversity combining and co-channel interference. Our analysis generalizes prior work in that we place no restrictions on the number or power of the interferers, or on the number of antennas at the transmitter and receiver. We also present an alternative mathematical approach to performance analysis that leads to an undemanding expression for the SINR moment generating function, which can then be used to evaluate average probability of error and the moments of the SINR. Our numerical results indicate that, for a fixed total interference power, system performance degrades when there are dominant interferers. In addition, for a fixed total number of transmit and receive antennas, outage probability and average bit error rate decrease when the transmitter and receiver have the same number of antennas.

31 citations


Proceedings ArticleDOI
11 Dec 2006
TL;DR: A novel STBC distributed ARQ system using multifrequency band is proposed for improving the performance of the ad-hoc cognitive radio due to the small transmit power and the large interference from the primary system.
Abstract: The cognitive radio is a secondary wireless communication system that can overlap the frequency band assigned to the primary system by recognizing the frequency status. Ad-hoc cognitive radio is considered for realizing the cognitive radio by using multi-hop communication networks without giving the large interference toward the primary system. We have proposed the STBC distributed ARQ system applied to the ad-hoc cognitive radio for realizing effective cognitive radio. This system can realize a multi-hop communication from the source terminal to the destination terminal without deciding the reliable route in advance. However, the affect of inter-system interference has not been evaluated yet. In this paper, in order to keep the interference level low at the receiver of the primary system, the permissible maximum transmit power of the cognitive terminals is analytically derived. Moreover, we propose a novel STBC distributed ARQ using multifrequency band for improving the performance of the ad-hoc cognitive radio due to the small transmit power and the large interference from the primary system. Finally, we confirm the effectiveness of the proposed system by using computer simulations.

Patent
10 Apr 2006
TL;DR: In this paper, a method for radio interference-based sensor localization is presented, which has the steps of creating an interference signal from a first transmitter and a second transmitter, measuring phase offsets of the interference signal received by a first receiver and a secondary receiver, respectively, and determining the locations of the first and second transmitters and the first or second receivers from the measured phase offsets.
Abstract: A method for radio interference based sensor localization. In one embodiment, the method has the steps of creating an interference signal from a first transmitter and a second transmitter, measuring phase offsets of the interference signal received by a first receiver and a second receiver, respectively, and determining the locations of the first and second transmitters and the first and second receivers from the measured phase offsets.

Proceedings ArticleDOI
01 Jun 2006
TL;DR: Performance analysis conducted for this model shows that cognitive UWB supports sub-carriers selection model of band with 528 MHz wide, and the probability of primary users appearance affects goodput through channel processes.
Abstract: The paper puts forward a new link maintenance and compensation model for cognitive UWB radio systems. In this model, the link maintenance is combined with change of modulation method. Performance analysis conducted for this model shows that Cognitive UWB supports sub-carriers selection model of band with 528 MHz wide, and the probability of primary users appearance affects goodput through channel processes. The retransmission of last data and the change of modulation method enhance the robustness against primary users interference, as primary users appear, and compensate to data corruption due to primary users interference.

Proceedings ArticleDOI
20 Sep 2006
TL;DR: An efficient and low-complexity subcarrier assignment algorithm as well as power control scheme are proposed to mitigate the co-channel interference (CCI) impact in downlink multi-cell Orthogonal Frequency Division Multiple Access (OFDMA) systems.
Abstract: In this paper, we investigate resource management in downlink multi-cell Orthogonal Frequency Division Multiple Access (OFDMA) systems. An efficient and low-complexity subcarrier assignment algorithm as well as power control scheme are proposed to mitigate the co-channel interference (CCI) impact. Based on a new centralized reuse partitioning strategy, our approach aims to minimize the outage probability in the entire system. With this algorithm, adaptive frequency reuse factors are applied according to users' bandwidth requirement and the CCI level they undergo. Transmit power is then adjusted for further improvement of the system capacity and this without increasing the CCI level. Simulation results show that our approach is particularly efficient for services that demand high bit rates.

Patent
Murat Mese1, Arak Sutivong1
15 Mar 2006
TL;DR: In this article, techniques for adjusting transmit power to mitigate both intra-sector interference to a serving base station and inter-segment interference to neighbor base stations are described, which may be done by combining interference information from multiple base stations.
Abstract: Techniques for adjusting transmit power to mitigate both intra-sector interference to a serving base station and inter-sector interference to neighbor base stations are described. This may be done by combining interference information from multiple base stations.

Patent
17 Apr 2006
TL;DR: In this article, methods and systems for cancelling interference in an analog communication signal are provided. But they do not consider the effect of interference caused by a deterministic interference source.
Abstract: Methods and systems for cancelling interference in an analog communication signal are provided. The method includes receiving an analog communication signal including interference caused by a deterministic interference source, generating a digital interference signal corresponding to the interference caused by the deterministic interference source, converting the digital interference signal into a corresponding analog interference signal, and subtracting the analog interference signal from the analog communication signal.

Patent
29 Aug 2006
TL;DR: In this article, a wireless broadband communications system that provides increased reliability in environments in which portions of the available operating frequency band are subject to interference is proposed, where the system allocates the data to the sub-carriers currently being subjected to the lowest levels of interference.
Abstract: A wireless broadband communications system that provides increased reliability in environments in which portions of the available operating frequency band are subject to interference. The system determines whether the operating frequency band is being subjected to interference. If so, then the system determines whether such interference is affecting one or more portions of the band. If interference is affecting just portions of the band, then the system reduces the data rate and the number of sub-carriers used to transmit data. Next, the system allocates the data to be transmitted to the sub-carriers currently being subjected to the lowest levels of interference, while allocating no data to the sub-carriers currently being subjected to the highest levels of interference. In this way, the system allocates the data to be transmitted to the sub-carriers occupying optimal portions of the operating frequency band, in response to detected changes in the interference environment.

Patent
Xintian E. Lin1, Qinghua Li
28 Mar 2006
TL;DR: In this article, power control and/or hand off operations are performed in a wireless network in a manner that can enhance overall network throughput in a way that can improve overall network performance.
Abstract: Techniques are provided that allow power control and/or hand off operations to be performed in a wireless network in a manner that can enhance overall network throughput.

Patent
06 Feb 2006
TL;DR: In this paper, a system and method for interference reduction in a broadband wireless access (BWA) network is described. And a mobile station performs a recursive process to update channel estimates of interfering channels on a symbol-by-symbol basis for use in canceling interference from data subcarriers received through two or more antennas.
Abstract: System and method for interference reduction in a broadband wireless access (BWA) network are disclosed. A mobile station performs a recursive process to update channel estimates of interfering channels on a symbol-by-symbol basis for use in canceling interference from data subcarriers received through two or more antennas.

Proceedings ArticleDOI
01 Sep 2006
TL;DR: An amplitude, phase and group delay time of the correction signal can be controlled adaptively for optimum cancellation of the feedback interference signal in the proposed cancellation system.
Abstract: In this paper, a co-channel interference cancellation technique is suggested in order to cancel a feedback interference signal in the wireless communication repeater. And an amplitude, phase and group delay time of the correction signal can be controlled adaptively for optimum cancellation of the feedback interference signal in the proposed cancellation system. The fabricated co-channel interference cancellation system for Korean RFID frequency band (908.5~914MHz) could obtain the reduced feedback interference signal about 36.4dB.

Patent
16 Oct 2006
TL;DR: In this paper, a receiver searches for and identifies the locations of narrowband interference by sweeping across a wideband frequency channel to measure power levels of at least three narrowband frequency regions and determines if at least one interfering signal is present as a function of the measured power levels.
Abstract: A receiver searches for and identifies the locations of narrowband interference by sweeping across a wideband frequency channel to measure power levels of at least three narrowband frequency regions and determines if at least one interfering signal is present as a function of the measured power levels.

Proceedings ArticleDOI
11 Dec 2006
TL;DR: In this paper, the downlink of a multi-cell OFDMA system is considered and rate adaptive optimization is investigated with minimum rate requirement and in presence of co-channel interference.
Abstract: In this paper, the downlink of a multi-cell OFDMA system is considered. Rate Adaptive Optimization is investigated with minimum rate requirement and in presence of co-channel interference. A low-complexity subcarrier allocation scheme is proposed. A particular procedure provides limitation of co-channel interference by dynamically adapting the subcarrier reuse factor. A rate requirement violation (RRV) threshold is introduced to decide whether or not the interference limitation procedure is to be used. The performance is evaluated for variant user?s rate requirement. The evaluation includes comparison of the cell global rate and the outage probability with existing heuristics.

Patent
28 Jun 2006
TL;DR: In this article, an orthogonal frequency division multiplex (OFDM) communication system comprises OFDM transmitters (103-109) and an OFDM receiver (101) consisting of a subcarrier status data controller (200) and a channel estimator (205) which determines channel estimates for at least an air interface communication channel from the first OFDM transmitter (103) to the interfering OFDM (101).
Abstract: An Orthogonal Frequency Division Multiplex (OFDM) communication system comprises OFDM transmitters (103-109) and an OFDM receiver (101) . The system comprises a subcarrier status data controller (200) for transmitting subcarrier status data to the OFDM receiver (101) . The subcarrier status data indicates the active subcarriers of the OFDM transmitters (103-109) . The OFDM receiver (101) further comprises a subcarrier status processor (203) which receives the subcarrier status data and a channel estimator (205) which determines channel estimates for at least an air interface communication channel from the first OFDM transmitter (103) and an air interface communication channel from the interfering OFDM transmitter (105) . An interference mitigation processor (207) performs interference mitigation of the interference in response to the subcarrier status data and the channel estimates thereby providing improved recovery of the data from the first OFDM transmitter (103) .

Proceedings ArticleDOI
01 Oct 2006
TL;DR: A new centralized and low-complexity algorithm is proposed that minimizes the outage probability in the entire system and applies a power control scheme that improves system capacity without increasing the CCI level.
Abstract: The increasing demand for high data rate services has created an acute requirement for efficient subcarrier assignment and power control algorithms in Orthogonal Frequency Division Multiple Access (OFDMA) systems. Resource allocation optimization becomes even more constraining in multi-cell OFDMA systems because of the presence of Co-Channel Interference (CCI). In this paper, we mitigate the CCI impact with a particular frequency reuse partitioning strategy. We propose a new centralized and low-complexity algorithm that minimizes the outage probability in the entire system. With this algorithm, adaptive frequency reuse factors are applied according to users' bandwidth requirements. We also apply a power control scheme that improves system capacity without increasing the CCI level. Simulation results show its efficiency for high bit rate services.

Proceedings ArticleDOI
01 Nov 2006
TL;DR: Simulation results in a space-time coded orthogonal frequency division multiplexing (STC-OFDM) system show that the proposed algorithm can significantly improve the robustness of the beamformers to combat the co-channel interference over Rayleigh multipath fading channel.
Abstract: In this paper, a robust algorithm based on particle filter is proposed to improve the performance of the beamformers with uncertainty or errors in desired direction-of-arrivals (DOAs). In the proposed scheme, DOAs of desired signals are regarded as groups of random particles. Simulation results in a space-time coded orthogonal frequency division multiplexing (STC-OFDM) system show that the proposed algorithm can significantly improve the robustness of the beamformers to combat the co-channel interference over Rayleigh multipath fading channel.

Journal ArticleDOI
TL;DR: Single antenna co-channel interference cancellation for cellular time-division multiple access (TDMA) networks by means of joint delayed-decision feedback sequence estimation is studied and the performance is increased by a novel adaptive state allocation technique.
Abstract: In this letter, single antenna co-channel interference cancellation for cellular time-division multiple access (TDMA) networks by means of joint delayed-decision feedback sequence estimation is studied. The performance is increased by a novel adaptive state allocation technique

Patent
02 Mar 2006
TL;DR: In this article, the levels of signal components transmitted by each of the co-channel base stations in the area under test in a wireless network are measured and associated with the appropriate (originating) base station in the presence of cochannel and adjacent channel interference without interrupting service by sensing and responding to received, variable, patterns.
Abstract: A method and apparatus for identifying signal sources in a multi-source signal. Levels of signal components transmitted by each of the co-channel base stations in the area under test in a wireless network are measured and associated with the appropriate (originating) base station in the presence of co-channel and adjacent-channel interference without interrupting service by sensing and responding to received, variable, patterns.

Patent
31 Mar 2006
TL;DR: In this paper, the authors present several apparatuses, articles, methods, and systems for predicting one or more performance metrics for an over-the-air link in the presence of co-channel interference.
Abstract: Embodiments of apparatuses, articles, methods, and systems for predicting one or more performance metrics for an over-the-air link in the presence of co-channel interference are generally described herein. Other embodiments may be described and claimed.

Journal ArticleDOI
S. Das1, Harish Viswanathan1
TL;DR: Time-multiplexed transmissions, despite the bursty out-of-cell interference power structure, has throughput comparable to that of a multiple-user orthogonal transmission system for small cells where mobiles have sufficient transmit power to meet the target IROT.
Abstract: We consider different transmission options on the reverse link of cellular systems for packet data. The different transmission options are classified based on the nature of in-cell and out-of-cell interference power statistics. The categories are: (a) no in-cell interference, averaged out-of cell interference; (b) no in-cell interference, bursty out-of-cell interference; and (c) averaged in-cell interference, averaged out-of-cell interference. Depending on whether the reverse link transmission is time multiplexed one user at a time transmission, or simultaneous transmission by multiple users with or without in-cell orthogonality, the interference structure falls into one of the above three categories. We analyze the throughput performance of the system in each of these cases when incremental redundancy is employed to combat uncertainty in the interference power. We compare the different options under an in-cell rise-over-thermal (IROT) constraint and provide some insights for reverse link design for next-generation cellular systems. Our results show that transmission option (a) with an optimal choice of the number of simultaneous transmissions within the cell has the best performance over several different scenarios. Time-multiplexed transmissions, despite the bursty out-of-cell interference power structure, has throughput comparable to that of a multiple-user orthogonal transmission system for small cells where mobiles have sufficient transmit power to meet the target IROT.

Proceedings ArticleDOI
01 Nov 2006
TL;DR: In a multiuser scenario, the capacity of multiple-input/multiple-output (MIMO) communication systems in the presence of multiple MIMO co-channel interferers is studied, using the known determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues with arbitrary multiplicity.
Abstract: In a multiuser scenario, we study the capacity of multiple-input/multiple-output (MIMO) communication systems in the presence of multiple MIMO co-channel interferers. We assume that transmitters have no information about the channel status and that all links undergo Rayleigh distributed fading; no restrictions are made to the transmission power levels or on the number of interferers and antennas, so that many possible cases can be studied, including distributed MIMO. In order to be able to cover all possible scenarios, we generalize the known determinant representation of hypergeometric functions with matrix arguments to the case when the argument matrices have eigenvalues with arbitrary multiplicity. Possible extensions and numerical results are then sketched.