Showing papers on "Co-channel interference published in 2016"

Intra and Inter-Cell Resource Management in Full-Duplex Heterogeneous Cellular Networks

Abstract: Full-duplex communication is drawing high attention as a means of enhancing wireless capacity considerably by enabling simultaneous transmission and reception on the same frequency spectrum. While it had been considered infeasible for a long time due to strong self-interference, recent researches have made substantial progress on addressing this challenge. This paper focuses on designing full-duplex cellular networks with co-channel femtocells. Due to relatively high transmit power, cancellation of self-interference by existing techniques could still be imperfect for cellular systems and thus residual interference may impact performance significantly. To overcome this in OFDMA systems, a new radio resource management scheme assigning downlink and uplink transmissions jointly while considering the gain of self-interference cancellation is developed. Three available transmission modes of a frequency resource block and crossover points between their achievable capacities are identified for the mode selection of each resource block. Users are then assigned resource blocks and transmit power levels are determined such that the total utility sum is maximized. To handle new femtocell interference scenarios, the transmit powers of femtocells and their connected users are adjusted by a coordination algorithm such that both data transmission and mode selection of an underlying macrocell are protected.

MIMO Cognitive Radio User Selection With and Without Primary Channel State Information

Abstract: In this paper, we study user selection (US) strategies for a multiple-input–multiple-output (MIMO) cognitive radio (CR) downlink network, where the $r$ -antenna underlay CR secondary users (SUs) coexist with a primary user (PU), and all terminals are equipped with multiple antennas. Two main scenarios are considered: 1) The $t$ -antenna cognitive base station (CBS) has perfect or partial channel state information at the transmitter (CSIT) from the CBS to the PU receiver (RX), and 2) the CBS has absolutely no PU CSIT. For these scenarios, we propose and evaluate multiple SU selection schemes that are applicable to both best-effort PU interference mitigation and hard interference temperature (IT) constraints. The computational complexity of the proposed schemes can be significantly smaller than that of an exhaustive search with negligible performance degradation. For the selection of $C$ SUs out of $K$ candidates, our proposed sliding window scheme, for example, is of complexity $\mathcal{O}(Krt^2)$ , whereas an exhaustive search is on the order of $\mathcal{O}(\binom{K}{C}C^4r^3)$ . When $t$ and $r$ are of the same order, the computational complexity of the proposed scheme can be $\binom{K}{C}C^4/K$ times smaller. Mathematical complexity analysis and numerical simulations are provided to show the advantage of our schemes.

Underlay Interference Analysis of Power Control and Receiver Association Schemes

Abstract: In this paper, we present a precise comprehensive analysis of the aggregate interference $I$ generated from an underlay network of cognitive radio (CR) nodes employing several transmit power control and receiver association schemes. Importantly, we consider spatial randomness by modeling CR transmitter nodes and receiver nodes as two independent Poisson point processes (PPPs). For the cognitive nodes, we investigate receiver association based on the distance or the instantaneous received power and power control based on the maximum possible transmitter–receiver distance, fixed or location-dependent cutoff power levels, feedback from the primary system, or the maximum number of available receivers. For each of these schemes, the exact moment generating function (mgf) and mean of aggregate $I$ power are derived for links with Rayleigh fading and exponential path loss. The resulting primary outage and the probability of secondary transmitter cutoff are also derived. Numerical results show that the secondary power thresholds and node densities significantly affect the aggregate $I$ , the primary receiver (PR) outage, and the secondary transmitter cutoff arising from the different schemes.

(Sub-)Optimality of Treating Interference as Noise in the Cellular Uplink With Weak Interference

Abstract: Despite the simplicity of the scheme of treating interference as noise (TIN), it was shown to be sum-capacity optimal in the Gaussian interference channel (IC) with very-weak (noisy) interference. In this paper, the two-user IC is altered by introducing an additional transmitter that wants to communicate with one of the receivers of the IC. The resulting network thus consists of a point-to-point channel interfering with a multiple access channel (MAC) and is denoted by PIMAC. The sum-capacity of the PIMAC is studied with main focus on the optimality of TIN. It turns out that TIN in its naive variant, where all transmitters are active and both receivers use TIN for decoding, is not the best choice for the PIMAC. In fact, a scheme that combines both time division multiple access and TIN (TDMA–TIN) strictly outperforms the naive-TIN scheme. Furthermore, it is shown that in some regimes, TDMA–TIN achieves the sum-capacity for the deterministic PIMAC and the sum-capacity within a constant gap for the Gaussian PIMAC. In addition, it is shown that, even for very-weak interference, there are some regimes where a combination of interference alignment with power control and TIN at the receiver side outperforms TDMA–TIN. As a consequence, on the one hand, TIN in a cellular uplink is approximately optimal in certain regimes. On the other hand, those regimes cannot be simply described by the strength of interference.

Cross-Layer Optimization for Multi-Hop Wireless Networks With Successive Interference Cancellation

Abstract: The classical approach to interference management in wireless medium access is based on avoidance. Recently, there is a growing interest in exploiting interference (rather than avoiding it) to increase network throughput. This was made possible by a number of advances at the physical layer. In particular, the so-called successive interference cancellation (SIC) scheme appears very promising, due to its ability to enable concurrent receptions from multiple transmitters as well as interference rejection. Although SIC has been extensively studied as a physical layer technology, its research and advances in the context of multi-hop wireless network remain limited. In this paper, we aim to close this gap by offering a systematic study of SIC in a multi-hop wireless network. After gaining a fundamental understanding of SIC’s capability and limitation, we propose a cross-layer optimization framework for SIC that incorporates variables at physical, link, and network layers. We use numerical results to affirm the validity of our optimization framework and give insights on how SIC behaves in a multi-hop wireless network.

A tractable approach to analyzing the energy-aware two-way relaying networks in the presence of co-channel interference

Abstract: Under the impact of co-channel interference (CCI) at two source nodes and the relay, we investigate the performance of dual-hop amplify-and-forward (AF) relaying networks. In terms of energy harvesting, the power-constrained relay first scavenges energy from the received signal and CCI signals then amplifies them and forwards them to the destination. In particular, we provide closed-form expressions for outage probability and bit error ratio (BER) to easily analyse the system performance. In this paper, the impact of distinct interference power level and the number of CCIs are derived. Monte Carlo simulations are used to provide expressions related to outage probability performance. It is confirmed that energy efficiency at the relay can be enhanced due to several advantages of CCI signals which can also prolong the life expectancy of relaying systems.

Interference Management Through Exclusion Zones in Two-Tier Cognitive Networks

Abstract: The transmission capacity of wireless networks is limited by the intensity of the interference received from concurrent transmissions. Interference causes serious performance degradation, particularly when no centralized controller within the network exists. Cognitive radio (CR) is a promising solution for distributed interference management as users with CR capabilities can acquire local activity and position information to achieve spatial reuse while limiting interference to neighboring users. Considering a two-tier network consisting of a licensed primary network overlaid by an unlicensed secondary tier, this paper proposes CR-based spectrum access schemes for secondary users (SUs). Acquiring the activity information of nearby users, the SUs are activated only when they are outside the exclusion zone of primary receivers. Additionally, the active secondary transmitters are separated from each other by forming secondary exclusion zones around themselves. Using stochastic geometry, primary and secondary exclusion zone sizes that maximize the transmission capacity under per-tier outage constraints are calculated. Analytical results supported by numerical simulations, suggest primary exclusion zones reduce predominantly the cross-tier interference while the secondary exclusion zone size is critical in mitigating the interference among SUs.

Multiuser hybrid satellite-terrestrial relay networks with co-channel interference and feedback latency

Abstract: In this paper, we consider a multiuser hybrid satellite-terrestrial relay network (HSTRN) that employs opportunistic user scheduling with feedback latency and amplify-and-forward relaying with co-channel interference (CCI). The performance of the considered HSTRN may be critically affected by outdated channel state information (CSI) and CCI in practical operating environments. Leveraging the statistical characterizations of the underlying hybrid channels, we first derive a novel closed-form expression of outage probability of the considered system. Then, we derive an asymptotic outage expression to examine the achievable diversity order. Numerical and simulation results corroborate the analysis and illustrate the impact of outdated CSI and CCI on the HSTRN performance.

Adaptive self-interference cancelation in LTE-A carrier aggregation FDD direct-conversion transceivers

Abstract: Modern frequency division duplex radio frequency transceivers experience transmitter-to-receiver leakage due to the limited isolation of the duplexer. In Long Term Evolution-Advanced (LTE-A) carrier aggregation receivers the coupling between the local oscillators creates harmonics on the chip which can lead to the downconversion of this leakage signal to the receive (Rx) baseband. Thereby, this so-called modulated spur interference reduces the signal-to-noise ratio of the Rx signal. In this paper, the modulated spur interference is modeled and several adaptive algorithms are compared regarding their convergence and cancelation performance. To maximize the data throughput, the adaptive filter is required to converge within the short time period of one orthogonal frequency-division multiplexing (OFDM) symbol. Out of the investigated concepts the proposed variable step-size least-mean-square algorithm turns out to be the most favorable choice. It satisfies the required constraints of convergence time and cancelation performance, and it features a reasonable low complexity.

Improving Wireless Physical Layer Security via Exploiting Co-Channel Interference

Abstract: This paper considers a scenario in which a source–destination pair needs to establish a confidential connection against an external eavesdropper, aided by the interference generated by another source–destination pair that exchanges public messages. The goal is to compute the maximum achievable secrecy degrees of freedom (S.D.o.F) region of a MIMO two-user wiretap network. First, a cooperative secrecy transmission scheme is proposed, whose feasible set is shown to achieve all S.D.o.F. pairs on the S.D.o.F. region boundary. In this way, the determination of the S.D.o.F. region is reduced to a problem of maximizing the S.D.o.F. pair over the proposed transmission scheme. The maximum achievable S.D.o.F. region boundary points are obtained in closed form, and the construction of the precoding matrices achieving the maximum S.D.o.F. region boundary is provided. The proposed expressions are functions of the number of antennas at each terminal, and apply to any number of antennas, thus constituting an advancement over prior works that have considered only fixed antenna configurations.

Uplink Resource Allocation in Interference Limited Area for D2D-Based Underlaying Cellular Networks

Abstract: The device-to-device (D2D) communication has become one of the most promising methods for alleviating the deficiency of wireless spectrum. In spite of the potential gains brought by activating D2D communications, the problem of severe interference between cellular and D2D users cannot be ignored. In this paper, we introduce the power-control scheme based on interference limited area (ILA) for alleviating the abovementioned interference. In a single cell where there are M cellular user equipments (CUEs) supporting both the conventional cellular mode and the D2D mode, the controlling thresholds λD and λC are defined for the D2D transmitter (DT) and the base station (BS), respectively; we forbid all the DT from transmission within ILA-S1 but activating DT only within the inner section of ILA-S2, where ILA-S1 and ILA-S2 are defined as the areas in which the signal-to- interference ratio (SIR) is higher than λC and λD, respectively. Furthermore, we propose a novel resourceallocation scheme relying on interference control mechanism based on the criteria of "maximum/minimum power of DT". Numerical results show that the proposed scheme is capable of achieving the best system performance in terms of capacity, where the optimal ILA size is attainable.

Impact of the CSI on the Performance of Cognitive Relay Networks With Partial Relay Selection

Abstract: In a cognitive relay network, a secondary cooperative transmission, sharing the same spectrum band with $N$ primary transmissions, is considered. Assuming imperfect channel state knowledge of the interference channels (from secondary transmitters to primary receivers) at the secondary nodes, we investigate the problem of secondary achievable rate maximization under a constraint on the interference caused at the primary receivers. Different scenarios are defined based on the accuracy of estimating the interference channels at the primary receivers and the number of feedback quantization bits. For each scenario, we derive expressions for both the secondary achievable rate and the primary interference probability. Then, we investigate the associated power allocation problem and provide a sub-optimal solution. Finally, analytical and simulation results illustrate the efficiency of the provided solution in terms of secondary achievable rate and primary interference probability.

Distributed Energy Spectral Efficiency Optimization for Partial/Full Interference Alignment in Multi-user Multi-relay Multi-cell MIMO Systems

Abstract: The energy spectral efficiency maximization (ESEM) problem of a multi-user, multi-relay, multi-cell system is considered, where all the network nodes are equipped with multi-antenna transceivers. To deal with the potentially excessive interference originating from a plethora of geographically distributed transmission sources, a pair of transmission protocols based on interference alignment (IA) are conceived. The first, termed the full-IA, avoids all intra-cell interference (ICI) and other-cell interference by finding the perfect interference-nulling receive beamforming matrices (RxBFMs). The second protocol, termed partial-IA, only attempts to null the ICI. Employing the RxBFMs computed by either of these protocols mathematically decomposes the channel into a multiplicity of non-interfering multiple-input–single-output channels, which we term as spatial multiplexing components (SMCs). The problem of finding the optimal SMCs as well as their power control variables for the ESEM problem considered is formally defined and converted into a convex optimization form with carefully selected variable relaxations and transformations. Thus, the optimal SMCs and power control variables can be distributively computed using both the classic dual decomposition and subgradient methods. Our results indicate that indeed, the ESEM algorithm performs better than the baseline equal power allocation algorithm in terms of its ESE. Furthermore, surprisingly the partial-IA outperforms the full-IA in all cases considered, which is because the partial-IA is less restrictive in terms of the number of available transmit dimensions at the transmitters. Given the typical cell sizes considered in this paper, the path-loss sufficiently attenuates the majority of the interference, and thus the full-IA over-compensates, when trying to avoid all possible sources of interference.

Radio with interference measurement during a blanking interval

Abstract: A backhaul radio is disclosed that operates in multipath propagation environments such as obstructed LOS conditions with uncoordinated interference sources in the same operating band. Such a backhaul radio may use a combination of interference mitigation procedures across multiple of the frequency, time, spatial and cancellation domains. Such backhaul radios may communicate with each other to coordinate radio resource allocations such that accurate interference assessment and channel propagation characteristics assessment may be determined during normal operation.

Co-channel interference in two-tier heterogeneous networks: analytical model and ergodic capacity

Abstract: The modelling of co-channel interference in heterogeneous networks HetNets is increasingly highlighted for the spectrum underlay mechanism where the macro base stations MBSs and low-power nodes LPNs share the same radio resources. To clarify the characteristics of co-channel interference, an analytical interference model is developed in this paper for the two-tier hierarchical HetNets in Long-Term-Evolution-Advanced systems, which consists of MBSs with deterministic locations and LPNs locating with a random Poisson field. The distribution of aggregate interference is analysed, and the parameters impacting the proposed interference model are evaluated. In the proposed aggregate interference model, the success probability is derived on the basis of the moment generation function. Further, the ergodic capacity is developed in high signal-to-noise ratio region, and its closed-form expressions are derived for both MBSs and LPNs. Simulation results are presented to validate the analytical results of proposed interference model. Copyright © 2014 John Wiley & Sons, Ltd.

Analysing self interference cancellation in full duplex radios

Abstract: Full duplex communication promises a theoretical 100% throughput gain by doubling the number of simultaneous transmissions. Such compelling gains are conditioned on perfect cancellation of the self interference power resulting from simultaneous transmission and reception. Generally, self interference power is modelled as a noise-like constant level interference floor. However, experimental validations have shown that the self interference power is in practice a random variable depending on a number of factors such as the surrounding wireless environment and the degree of interference cancellation. In this study, we derive an analytical model for the residual self interference power, and demonstrate various applications of the derived model in analysing the performance of a Full Duplex radio. In general, full duplex communication is found to provide only modest throughput gains over half duplex communication in a dense network scenario with practical self interference cancellation models.

Full duplex backhaul radio with interference measurement during a blanking interval

Abstract: A backhaul radio is disclosed that operates in multipath propagation environments such as obstructed LOS conditions with uncoordinated interference sources in the same operating band. Such a backhaul radio may use a combination of interference mitigation procedures across multiple of the frequency, time, spatial and cancellation domains. Such backhaul radios may communicate with each other to coordinate radio resource allocations such that accurate interference assessment and channel propagation characteristics assessment may be determined during normal operation.

Massive MIMO based underlay networks with power control

Abstract: While massive MIMO based underlay cognitive radio (CR) networks are a promising concept in the next generation of wireless networks to increase spectral efficiency, reusing the same pilot sequences in both networks cause pilot contamination leading to residual interference. Thus, this paper investigates the affects of pilot contamination on a random CR network underlaid upon a random primary network where both networks employ path loss inversion based power control. A Matern cluster process is considered for the underlay system, while homogeneous Poisson point processes are considered for the primary transmitters and receivers. We derive the moment generating function of the normalized aggregate interference at an underlay receiver, its first two moments, and the outage probability. Finally, it is shown that the underlay cluster radius, ensured received power levels through power control and the different node densities have a significant effect on the outage of an underlay receiver.

Coordinated multi-point transmissions based on interference alignment and neutralization

Abstract: Both interference alignment (IA) and interference neutralization (IN) are exploited for Coordinated Multi-Point (CoMP) transmissions. With the base station's cooperation, transmit precoder and receive filter are designed jointly, and then concurrent transmissions of multiple data streams are achieved. In the design of preprocessing, IN is applied to the interferences carrying same data so as to align the interfering signals with opposite directions in a subspace. On the other hand, for interferences carrying different information, IA is employed to align them with the same direction in a subspace, thus reducing the interference signal dimension observed at the user side. Based on different precoding schemes at the transmitter's side, receivers adopt zero-forcing (ZF) so as to recover the desired data. The proposed interference alignment and neutralization based CoMP (IAN-CoMP) mechanism can achieve effective interference cancellation and suppression by exploiting limited and flexible collaboration only at the base station (BS) side. We also extend the mechanism to general cases where the antenna configurations at both transmitter and receiver side, the number of transmitters participating in CoMP and simultaneously served users are variable. In addition, the proposed scheme can also achieve a flexible tradeoff between cooperation overhead and the system's achievable degrees of freedom (DoFs). Our in-depth simulation results show that IAN-CoMP can significantly improve the spectral efficiency (SE) for cell-edge users.

Multi sensor radio frequency detection

Abstract: Radio frequency motion sensors may be configured for operation in a common vicinity so as to reduce interference. In some versions, interference may be reduced by timing and/or frequency synchronization. In some versions, a master radio frequency motion sensor may transmit a first radio frequency (RF) signal. A slave radio frequency motion sensor may determine a second radio frequency signal which minimizes interference with the first RF frequency. In some versions, interference may be reduced with additional transmission adjustments such as pulse width reduction or frequency and/or timing dithering differences. In some versions, apparatus may be configured with multiple sensors in a configuration to emit the radio frequency signals in different directions to mitigate interference between emitted pulses from the radio frequency motion sensors.

Queuing Theory Based Co-Channel Interference Analysis Approach for High-Density Wireless Local Area Networks

Abstract: Increased co-channel interference (CCI) in wireless local area networks (WLANs) is bringing serious resource constraints to today’s high-density wireless environments. CCI in IEEE 802.11-based networks is inevitable due to the nature of the carrier sensing mechanism however can be reduced by resource optimization approaches. That means the CCI analysis is basic, but also crucial for an efficient resource management. In this article, we present a novel CCI analysis approach based on the queuing theory, which considers the randomness of end users’ behavior and the irregularity and complexity of network traffic in high-density WLANs that adopts the M/M/c queuing model for CCI analysis. Most of the CCIs occur when multiple networks overlap and trigger channel contentions; therefore, we use the ratio of signal-overlapped areas to signal coverage as a probabilistic factor to the queuing model to analyze the CCI impacts in highly overlapped WLANs. With the queuing model, we perform simulations to see how the CCI influences the quality of service (QoS) in high-density WLANs.

Interference alignment in space, time and frequency: achievable DoF analysis

Abstract: It is well established that the employment of interference alignment (IA) in the interference channel can enhance the achievable degrees of freedom (DOF) significantly. The feasibility of IA in a multi-carrier time-extended interference channel is considered. A new IA scheme is introduced that jointly performs the alignment over space, time and frequency. An asymmetric case is considered where the users are equipped with a different number of transmit/receive antennas. In the wake of this asymmetry, the feasible DoF of each user can be different. A closed-form necessary condition on the feasibility of asymmetric achievable DoF in the proposed scheme is derived.

Interference Alignment for Multicell Multiuser MIMO Uplink Channels

Abstract: This paper proposes a linear interference alignment (IA) scheme, which can be used for uplink channels in a general multicell multiuser multiple-input-multiple-output (MIMO) cellular network. The proposed scheme aims to align interference caused by signals from a set of transmitters into a subspace that is established by the signals from only a subset of those transmitters, thereby effectively reducing the number of interfering transmitters. The total degrees of freedom (DoF) achievable by the proposed scheme is given in closed-form expression, and a numerical analysis shows that the proposed scheme can achieve the optimal DoF in certain scenarios and provides a higher total DoF than other related schemes in most cases.

Relay-Assisted Cross-Channel Gain Estimation for Spectrum Sharing

Abstract: In cognitive radio networks, the cross-channel gain from a cognitive transmitter (CT) to a primary receiver (PR) is critical for spectrum sharing and obtaining the cross-channel gain is very difficult. Even though proactive estimation allows the CT to autonomously estimate the cross-channel gain, it may cause severe interference to the PR. This raises a new issue for spectrum sensing, called spectrum sensing interference . In this paper, we deal with the sensing interference and propose a relay-assisted method to conduct the proactive estimation, which obtains the cross-channel gain with much less interference to the PR. In our method, we let the CT act as a full-duplex amplify-and-forward relay to probe the close-loop power control between primary transceivers. By measuring the power adjustment of the primary signal, the CT estimates the cross-channel gain. Simulation results indicate that our method can reduce the sensing interference to an extremely low level.

Retrospective Interference Alignment for the $K$ -User $M\times N$ MIMO Interference Channel

Abstract: In this paper, we consider a $K$ -user $M\times N$ MIMO interference channel, with outdated channel state information at the transmitters (CSIT). Based on the technique introduced by Cadambe and Jafar, for the IC with perfect and up-to-date CSIT, we propose and analyze a scheme that guarantees interference alignment with outdated CSIT. The interference is aligned by the transmitters, and removed by the receivers using zero-forcing by Cadambe and Jafar. However, this is not feasible for the IC with outdated CSIT, since there is no up-to-date CSIT to compute the interference alignment precoders. To overcome this limitation, we propose that the interference should be aligned by the receivers instead. With this approach, the interference caused by a transmitter spans the same subspace at all receivers, i.e., the interference at receiver $k eq m$ may be obtained through a linear map from the interference at receiver $m$ . Therefore, one interference retransmission per transmitter is enough to cancel all the interference. This reduces the overhead required for interference removal from $K(K-1)$ to $K$ interference terms.

Outage Analysis of Underlay Cognitive Radio Networks With Multihop Primary Transmission

Abstract: In this letter, we investigate an underlay cognitive radio network consisting of a single-hop secondary network coexisting with a multihop primary network. In the secondary network, the secondary destination receives the same interference signals from primary terminals over different time, which are cancelled by successive interference cancellation. We analyze the outage probability of the primary network and that of the secondary network. The validity of our analysis is verified by computer simulations.

Modelling interference in high altitude platforms with 3D LoS massive MIMO

Abstract: In this paper, we study a three-dimensional (3D) massive multiple-input-multiple-output (MIMO) system where a horizontal planar antenna array hovers in the sky, serving multiple single-antenna users in a cell on the ground. We consider the uplink where the users transmit to the antenna array utilising perfect uplink power control. Assuming pure line-of-sight (LoS) propagation conditions, the planar array performs receiver maximum-ratio-combining (MRC). We adopt a 3D freespace propagation channel model, which enables us to exploit both the azimuth and elevation dimensions of the space. Under such a setting, we analyse the intra-cell uplink interference. The effective single-user interference and total interference can then be modelled by Beta and Beta-mixture distributions, respectively. In particular, we point out that the height of the hovering antenna can be adjusted to minimise the interference in the system, and thus optimise all the signal-to-interference ratio (SIR) related performance metrics such as coverage and average throughput.

Reduction of inter-cell interference in asynchronous multi-cellular VLC by using OFDMA-based cell partitioning

Abstract: Inter-cell interference hinders multi-cellular transmission in visible light communication (VLC). We proposed a subcarrier allocation-based cell partitioning to avoid co-channel interference without a large frequency guard and additional RF components. In asynchronous environment, the interference remains due to a timing offset between cells even in the subcarrier allocation-based cell partitioning. To mitigate the remaining interference, we employed cyclic prefix (CP) extension and filter bank based multicarrier (FBMC), which could improve performance and it was experimentally demonstrated in this paper. By using the proposed method, inter-cell interference in asynchronous multi-cellular VLC could be effectively mitigated with only trivial frequency guard.

Interference cancellation methods and apparatus

Abstract: Methods and apparatus for interference cancelation in a radio frequency communications device are described. In various embodiments a signal to be transmitted in converted into an optical signal and processed using an optical filter assembly including one or more optical filters to generate an optical interference cancelation signal. The optical interference cancelation signal is converted into an analog radio frequency interference cancelation signal using an optical to electrical converter prior to the analog radio frequency interference cancelation signal being combined with a received signal to cancel interference, e.g., self interference. The optical filter assembly can include a large number of taps, e.g., 30, 50, 100 or more. Each tap may be implemented as a separate optical filter or series of optical filters. Delays and/or gain of the optical filters can be controlled dynamically based on channel estimates which may change due to changes in the environment and/or communications device position.

Effect of CCI on WPC With Time-Division Energy and Information Transmission

Abstract: The effect of cochannel interference (CCI) is studied on the performance of wireless powered communications (WPC), where the access point transfers energy in the downlink and the node sequentially uses the harvested energy to transmit information in the uplink. The average signal-to-interference-plus-noise ratio, the outage probability and the average throughput are examined. Numerical results show that the ratio of the interference power in the downlink and that in the uplink and the signal-to-noise ratio are crucial in determining whether the interference is beneficial or damaging. The effects of interference on different performance measures are also different.