Cognitive Transmission Research Articles

The role of parental cognitive ageing in the intergenerational mobility of cognitive abilities

This paper studies intergenerational transmission of cognitive abilities from parents to children, highlighting the role of parental cognitive ageing measured during adulthood, net of their cognitive abilities measured in adolescence. We investigate the life-cycle of parental cognitive abilities on offspring’s cognitive abilities within the British National Child Development Study (NCDS). We find that children benefit not only from the stock of cognitive abilities their mothers and fathers hold as adolescents, but also from cognitive evolution their parents achieve as adults. Furthermore, we find that favourable parental cognitive ageing is particularly important for low ability offspring, pointing to a potential role of cognition in delivering more effective mitigation and nurturing. When analysing three subsequent generations, we find that the transmission of late parental cognition is strong in the offspring with high education origins, in particular for the those in the upper tail of the cognitive abilities distribution. We quantify the economic impact of the cognitive ageing transmission, and find that one standard deviation increase in late parental cognition can be approximated to an average of 1.7% increase in offspring earnings.

Uplink modeling of cognitive radio network using stochastic geometry

In this study, we investigate the coverage probability and spectral efficiency of a cognitive radio network with a single-tier uplink model based on a stochastic geometry framework. The locations of cognitive transmitters, cognitive receivers, primary transmitters, and primary receivers are modeled as independent Poisson point processes. We derive the mathematical expressions for the coverage probability and spectral efficiency of this network, as well as closed-form expressions for a path-loss exponent equal to 4. For the uplink transmission, truncated channel inversion power control is employed for the cognitive transmitter with a cutoff threshold at the cognitive receiver because of the limited transmission power. We consider two locations of the cognitive receiver (i.e., inside and outside the primary exclusion region) for uplink transmission. We found that the location of the cognitive receiver impacts on coverage probability and spectral efficiency. Numerical analysis confirms that (i) the coverage probability is higher and (ii) the spectral efficiency is higher when the cognitive receiver is outside the primary exclusion region.

A Non-Cooperative Game Model with Channel Price Scheme in Cognitive Radio Transmission

A Non-Cooperative Game Model with Channel Price Scheme in Cognitive Radio Transmission

Cognition and Cooperation in Interfered Multiple Access Channels

In this work, we investigate a three-user cognitive communication network where a primary two-user multiple access channel suffers interference from a secondary point-to-point channel, sharing the same medium. While the point-to-point channel transmitter—transmitter 3—causes an interference at the primary multiple access channel receiver, we assume that the primary channel transmitters—transmitters 1 and 2—do not cause any interference at the point-to-point receiver. It is assumed that one of the multiple access channel transmitters has cognitive capabilities and cribs causally from the other multiple access channel transmitter. Furthermore, we assume that the cognitive transmitter knows the message of transmitter 3 in a non-causal manner, thus introducing the three-user multiple access cognitive Z-interference channel. We obtain inner and outer bounds on the capacity region of the this channel for both causal and strictly causal cribbing cognitive encoders. We further investigate different variations and aspects of the channel, referring to some previously studied cases. Attempting to better characterize the capacity region we look at the vertex points of the capacity region where each one of the transmitters tries to achieve its maximal rate. Moreover, we find the capacity region of a special case of a certain kind of more-capable multiple access cognitive Z-interference channels. In addition, we study the case of full unidirectional cooperation between the 2 multiple access channel encoders. Finally, since direct cribbing allows us full cognition in the case of continuous input alphabets, we study the case of partial cribbing, i.e., when the cribbing is performed via a deterministic function.

Capacity Results for the Multicast Cognitive Interference Channel

The capacity region of the multicast Cognitive Inter-Ference Channel (CIFC) is investigated. This channel consists of two independent transmitters that wish to multicast two different messages, each to a different set of users. In addition, one of the transmitters—commonly referred to as the cognitive transmitter—has prior non-causal knowledge of both messages to be transmitted. This scenario subsumes some long-standing open problems, such as the interference channel , the broadcast channel , and multicast communications . The aim of this paper is the derivation of optimal interference mitigation techniques under different interference regimes. To this end, two settings, namely the multi-primary CIFC , i.e., $M=1$ and $N \geq 1$ , and its complementary, the multi-secondary CIFC , i.e., $N=1$ and $M \geq 1$ , are investigated as an attempt to build a thorough understanding for the more general multicast CIFC setting. It is shown that, for some interference regimes, well-known coding techniques for the standard CIFC remain still optimal under the constraint of multicasting to multiple users. However, in other interference regimes, capacity achieving coding and decoding schemes prove to be more involved. A careful combination of these coding schemes and new outer bounding techniques allows to characterize the capacity region for several classes of discrete memoryless and Gaussian multicast CIFC under different interference regimes.

Outage and energy-efficiency analysis of cognitive radio networks: A stochastic approach to transmit antenna selection

Cognitive radio networks have recently attracted significant research attention owing to their promise for application in future cellular communication. In this light, given the intense power consumption of wireless networks, considerable research is now being directed at designing random cognitive radio networks with enhanced energy efficiency. In this study, we investigate the outage probability and energy efficiency in a cognitive radio network, modeling the locations of the primary users and cognitive users as a Poisson point process. We derive closed-form expressions for the outage probability and energy efficiency with consideration of the probabilities of unoccupied (not utilized by the primary users) channel selection and successful transmission for imperfect detection in an interference-limited environment of cognitive radio network. Furthermore, we propose a transmit antenna selection method for the cognitive transmitter in such networks and accordingly develop closed-form expressions for the outage probability and energy efficiency. The study reported here highlights the importance of combining the capabilities of unoccupied channel selection and successful transmission in cognitive radio networks to achieve optimal performance regarding outage probability and energy efficiency. In terms of energy efficiency, there is an optimal threshold that maximizes the energy efficiency. For implementation in transmit antenna selection, the outage probability can be significantly decreased by increasing the number of transmit antennas, even though the energy efficiency is maximized at the target outage probability.

Adaptive Cooperation for Bidirectional Communication in Cognitive Radio Networks

In the interweave cognitive networks, the interference from the primary user degrades the performance of the cognitive user transmissions. In this paper, we propose an adaptive cooperation scheme in the interweave cognitive networks to improve the performance of the cognitive user transmissions. In the proposed scheme for the bidirectional communication of two end-source cognitive users, the bidirectional communication is completed through the non-relay direct transmission, the one-way relaying cooperation transmission, and the two-way relaying cooperation transmission depending on the limited feedback from the end-sources. For the performance analysis of the proposed scheme, we derive the outage probability and the finite-SNR diversity multiplexing tradeoff (f-DMT) in a closed form, considering the imperfect spectrum sensing, the interference from the primary user, and the power allocation between the relay and the end-sources. The results show that compared with the direct transmissions (DT), the pure one-way relaying transmissions (POWRT), and the pure two-way relaying transmissions (PTWRT), the proposed scheme has better outage performance. In terms of the f-DMT, the proposed scheme outperforms the full cooperation transmissions of the POWRT and PTWRT.

Cognitive Multi-Relay Transmission over Asymmetric Fading Channels with Imperfect CSI

Outage performance of a cognitive multi-relay system using imperfect channel state information (CSI) of interfering links is formulated in this paper. In the considered cognitive system, it is assumed that wireless channels in the secondary network (source-to-relay and relay-to-destination links) experience Rician fading whereas interfering channels between primary and secondary networks undergo Rayleigh fading. Under the assumption of asymmetric fading, an outage probability (OP) expression of the secondary network is approximately formulated. Analytical OP values are in good agreement with related empirical ones in low signal-to-noise ratio (SNR) regimes. As a result, the approximate OP expression can be used to quantify the effect of asymmetric fading channels and CSI imperfection on the performance of cognitive multi-relay systems in practical SNR ranges.

Non-Orthogonal Random Access in MIMO Cognitive Radio Networks: Beamforming, Power Allocation, and Opportunistic Transmission.

We study secondary random access in multi-input multi-output cognitive radio networks, where a slotted ALOHA-type protocol and successive interference cancellation are used. We first introduce three types of transmit beamforming performed by secondary users, where multiple antennas are used to suppress the interference at the primary base station and/or to increase the received signal power at the secondary base station. Then, we show a simple decentralized power allocation along with the equivalent single-antenna conversion. To exploit the multiuser diversity gain, an opportunistic transmission protocol is proposed, where the secondary users generating less interference are opportunistically selected, resulting in a further reduction of the interference temperature. The proposed methods are validated via computer simulations. Numerical results show that increasing the number of transmit antennas can greatly reduce the interference temperature, while increasing the number of receive antennas leads to a reduction of the total transmit power. Optimal parameter values of the opportunistic transmission protocol are examined according to three types of beamforming and different antenna configurations, in terms of maximizing the cognitive transmission capacity. All the beamforming, decentralized power allocation, and opportunistic transmission protocol are performed by the secondary users in a decentralized manner, thus resulting in an easy implementation in practice.

Primary Channel Gain Estimation for Spectrum Sharing in Cognitive Radio Networks

In cognitive radio networks, the channel gain between primary transceivers, namely, primary channel gain, is crucial for a cognitive transmitter (CT) to control the transmit power and achieve spectrum sharing. Conventionally, the primary channel gain is estimated in the primary system and thus unavailable at the CT. To deal with this issue, two estimators are proposed by enabling the CT to sense primary signals. In particular, by adopting the maximum likelihood (ML) criterion to analyze the received primary signals, a ML estimator is first developed. After demonstrating the high computational complexity of the ML estimator, a median based (MB) estimator with proved low complexity is then proposed. Furthermore, the estimation accuracy of the MB estimation is theoretically characterized. By comparing the ML estimator and the MB estimator from the aspects of the computational complexity as well as the estimation accuracy, both advantages and disadvantages of two estimators are revealed. Numerical results show that the estimation errors of the ML estimator and the MB estimator can be as small as $0.6$ dB and $0.7$ dB, respectively.

Modified hybrid interference cancellation algorithm for uplink cognitive radio transmission based on overloaded DS-CDMA

In this paper, cognitive radio network architecture based on overloaded direct sequence code division multiple access (O-DS-CDMA) is proposed. In this method, secondary users are enabled to share the available bandwidth with the existing primary users. Two sets of orthogonal Gold codes are used to support the primary and secondary users simultaneously. Orthogonality between the spreading codes is lost due to non-zero cross correlation between the codes and timing synchronisation error in the uplink transmission, which causes interference among primary and secondary users. In this paper, a modified hybrid parallel/successive interference cancellation algorithm is proposed for the primary and secondary user base station receivers with multiple antennas, to suppress the interference among the users. Interferences among same group users are cancelled using parallel interference cancellation and the interferences between groups are cancelled using successive interference cancellation. The simulation results show that, the proposed modified interference cancellation algorithm improves the BER performance of the system significantly.

Outage Probability and Power Allocation for Collaborative Relaying of Multiple-Access Primary Users by Secondary User With Partial/Full Channel Knowledge

This paper investigates collaborative spectrum sharing (CSS) for which a cognitive secondary transmitter acts as a decode-and-forward (DF) relay for two primary users (PUs) occupying an interfering multiple-access channel. PUs are assumed to send their signals simultaneously; hence, interference between the primary signals exists due to the multiple-access nature. The secondary user (SU) selects and forwards one of the PU's signals to a desired destination, and at the same time, the SU also transmits its own signal only if it is not harmful to PUs. The selection of a primary signal to relay is investigated, depending on SU's knowledge of two primary source–destination channels, for which closed-form outage probabilities for PUs and SU are provided accordingly. With the help of the closed-form PU's outage probability, an optimal selection strategy between the primary signals and an optimal power allocation between the primary and secondary signals are also obtained in closed form, which minimizes SU's outage probability while keeping the PU's outage performance at an SU-free level. Numerical investigation is used to verify and illustrate the analysis given in this paper. Numerical results also show that the SU's performance can vary significantly according to the amount of channel knowledge that the SU can have.

Relay selection for secrecy improvement in cognitive amplify‐and‐forward relay networks against multiple eavesdroppers

In this study, the authors investigate the physical-layer security in a cognitive amplify-and-forward relay network consisting of a secondary transmitter (ST) and a secondary destination (SD) with the aid of multiple secondary relays (SRs) in the face of multiple eavesdroppers. In cognitive radio networks, increasing transmit power may not always be beneficial in terms of improving the channel capacity of cognitive transmissions, which would not only cause an extra interference to primary user, but also enhance the possibility of successfully intercepting the cognitive transmissions at an eavesdropper because an improved signal strength is received in this case. The authors propose two relay selection schemes to improve the physical-layer security of cognitive transmissions against eavesdropping attacks, which are referred to as the global and partial channel state information based relay selection, denoted by GCSIbRS and PCSIbRS, respectively. The authors analyse the intercept probability of the proposed GCSIbRS and PCSIbRS, as well as the traditional round-robin and all-relay transmission schemes. It is shown that the proposed GCSIbRS and PCSIbRS schemes both outperform the conventional round-robin and all-relay schemes in terms of their intercept probability performance.

Joint sensing and transmission for cognitive amplify-and-forward two-way relay networks

In this paper, we propose a cognitive transmission scheme for Amplify-and-Forward (AF) two-way relay networks (TWRNs) and investigate its joint sensing and transmission performance. Specifically, we derive the overall false alarm probability, the overall detection probability, the outage probability of the cognitive TWRN over Rayleigh fading channels. Furthermore, based on these probabilities, the spectrum hole utilization efficiency of the cognitive TWRN is defined and evaluated. It is shown that smaller individual or overall false alarm probability can result in less outage probability and thus larger spectrum hole utilization efficiency for cognitive TWRN, and however produce more interference to the primary users. Interestingly, it is found that given data rate, more transmission power for the cognitive TWRN does not necessarily obtain higher spectrum hole utilization efficiency. Moreover, our results show that a maximum spectrum hole utilization efficiency can be achieved through an optimal allocation of the time slots between the spectrum sensing and data transmission phases. Finally, simulation results are provided to corroborate our proposed studies. Copyright © 2016 John Wiley & Sons, Ltd.

Multicoding Schemes for Interference Channels

The best known inner bound for the two-user discrete memoryless interference channel is the Han–Kobayashi rate region. The coding schemes that achieve this region are based on rate-splitting and superposition coding. In this paper, we develop a multicoding scheme to achieve the same rate region. A key advantage of the multicoding nature of the proposed coding scheme is that it can be naturally extended to more general settings, such as when encoders have state information or can overhear each other. In particular, we extend our coding scheme to characterize the capacity region of the state-dependent deterministic Z-interference channel when noncausal state information is available at the interfering transmitter. We specialize our results to the case of the linear deterministic model with ON/OFF interference, which models a wireless system where a cognitive transmitter is noncausally aware of the times it interferes with a primary transmission. For this special case, we provide an explicit expression for the capacity region and discuss some interesting properties of the optimal strategy. We also extend our multicoding scheme to find the capacity region of the deterministic Z-interference channel when the signal of the interfering transmitter can be overheard at the other transmitter (also known as unidirectional partial cribbing).

On the secrecy of the cognitive interference channel with partial channel states

AbstractThe secrecy problem in the state‐dependent cognitive interference channel is considered in this paper. In our model, there are a primary and a secondary (cognitive) transmitter–receiver pairs, in which the cognitive transmitter has the message of the primary one as side information. In addition, the channel is affected by two channel state sequences, which are known at the cognitive transmitter and the corresponding receiver, separately. The cognitive transmitter should cooperate with the primary one, and it wishes to keep its message secure at the primary receiver. The achievable equivocation‐rate regions for this channel are derived using two approaches: the binning scheme coding and superposition coding. Then, comparisons between the results using two coding approaches, in Gaussian case, shows that there is a trade‐off between the achievable rate of the primary transmitter and the equivocation rate of the cognitive one. Moreover, the outer bounds on the capacity of the channel are derived. Copyright © 2016 John Wiley & Sons, Ltd.

Game Theory based Hybrid Cognitive Radio Transmission

Background: Overlay based Cognitive radio can utilize only the primary user spectrum opportunistically for transmission. A hybrid overlay and under based cognitive radio is presented with game theory based decision making to facilitate continuous transmission support for the secondary user. Methods: The Hybrid Cognitive Radio (HCR) provides an optimum solution for effective utilization of the spectrum. A hybrid cognitive radio is designed to switch between overlay and under lay mode of transmission to continuously provide transmission opportunity with high data rate support for secondary user. The switching between the two transmission modes and frequency selection is formulated as a game. Decision making in the game is carried out by using the frequency utilization factor of the primary user as the utilization function of the game. Spectrally Modulated Spectrally Encoded (SMSE) framework is employed to efficiently generate the overlay Orthogonal Frequency Division Multiplexing signal and underlay Multicarrier Code Division Multiple Access (MCCDMA) signal with less overhead. Findings: This simple game theory based hybrid cognitive radio show improved bit error rate and throughput performance of the secondary user. The implementation of the hybrid cognitive radio is done using the LabVIEW and Universal Software Radio Peripheral (USRP) Software defined radio hardware platform. Applications/Improvements: The overhead of generation two different waveform in hybrid cognitive radio using Fast Fourier Transform (FFT) is reduced by sharing the common functionality between them under the frame work of the Spectrally Modulated Spectrally Encoded scheme which reduces the switching time and increases the spectral efficiency.

Outage Performance of Cognitive Relay Networks With Wireless Information and Power Transfer

In this paper, we consider underlay cognitive radio (CR) networks with one primary receiver, one cognitive transmitter–receiver pair, and one energy harvesting relay. The transmission power of the secondary source is opportunistically determined by its interference to the primary receiver, and the relay transmission is powered by the energy harvested from the radio-frequency observations at the relay. For the considered CR networks with simultaneous wireless information and power transfer (SWIPT), we derive analytical expressions for the outage probability, as well as their high signal-to-noise ratio (SNR) approximations in closed form. The developed analytical results demonstrate that the use of SWIPT will not cause any loss in diversity gain, but the outage probability achieved by the SWIPT-CR scheme asymptotically decays as ${\log \mbox{SNR}}/\mbox{SNR}$ , whereas a decaying rate of ${\mbox{1}}/\mbox{SNR}$ is achieved by a conventional CR network. Computer simulation results are also provided to demonstrate the accuracy of the presented analysis.

Cooperative Precoding for Cognitive Transmission in Two-Tier Networks

In this paper, we study cooperative precoder design in two-tier networks, consisting of a macro-cell (MC) and several small-cells (SCs). By exploiting multiuser Vandermonde-subspace frequency division multiplexing (VFDM) transmission, an MC downlink can co-exist with cognitive SCs. In this paper, we first propose a cooperative cross-tier precoder (CTP) among the transmitters in the SCs to increase the transmitted dimension. The cooperative CTP allows us to use more efficient intra-tier precoder (ITP) in SCs to handle intracell interference and improve the throughput of the cognitive system. And then, three ITPs, a block-diagonal zero-forcing (BD-ZF) ITP, a capacity-achieving (CA) ITP, and a generalized MMSE channel inversion (GMI) ITP, are developed. Complexities of all CTPs and ITPs are discussed and compared. The overhead of channel state information (CSI) exchange is analyzed. Numerical results are presented to demonstrate the throughput improvement of the proposed schemes and to discover the impact of the imperfect CSI. From the complexity comparison and the numerical results, the GMI ITP offers a good tradeoff between complexity and throughput.

Relay-Assisted Cross-Channel Gain Estimation for Spectrum Sharing

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.