Cognitive Interference Channel Research Articles

Shannon meets Stackelberg on the cognitive interference channel part I: A deterministic view

AbstractIn this paper, we have combined a game‐theoretic and an information‐theoretic notions to describe the selfish behavior of each user in a two‐user linear deterministic cognitive interference channel (LD‐CIC). The two‐user LD‐CIC is the simple case of the cognitive radio technology in the high SNR regime. This model is a solution to improve the spectral efficiency in software defined network (SDN) concept in 5G. In the two‐user LD‐CIC, the information bits of the primary/licensed transmitter is a‐priori provided at the cognitive/secondary/unlicensed transmitter. So that, the cognitive transmitter can cooperate and utilize the frequency spectrum to send the information bits of the both transmitters. In information‐theoretic approaches, full cooperation is assumed between transmitters for codebook and rate selection in this channel. This may not be a realistic assumption if transmitters are selfish and are willing to maximize their own benefit. In particular, we have defined the Stackelberg equilibrium (SE) region on the capacity region of the two‐user LD‐CIC to capture the behavior of each transmitter when they compete even though one of them is informed of the other transmitter information bits. We have implemented a two‐phase Stackelberg game with the primary and cognitive transmitters acting as the leader in the first phase, and the follower in the second phase, respectively. In this implementation, both transmitters are assumed to be selfish and only interested in optimizing their own pay‐offs. The SE region is characterized as a subset of capacity region in which the transmitters cannot gain more transmission rate by individually deviating from the SE strategy. The achievability of the resultant region has been configured using a randomized Han‐Kobayashi scheme for all the channel gains. Also, we have compared the obtained SE region with the previous equilibrium regions such as Nash equilibrium (NE) region of the linear deterministic interference channel (LD‐IC). The results have shown that the SE points on the sum‐rate of the LD‐CIC capacity region are more than the NE points on the sum rate of the capacity region of LD‐IC, so the SE region of the LD‐CIC is Pareto superior to the NE region of LD‐IC.

Secrecy capacity results for a secure NOMA-based cognitive radio network with an external eavesdropper

In this paper, we investigate a secure cognitive radio network (CRN), which deploys non-orthogonal multiple access (NOMA) to deliver a mixed multicast and unicast traffic to the intended receivers, while keeping them secret from the eavesdroppers. This model represents a cognitive interference channel with an external eavesdropper (CIC-EE). In this model, there are one pair of primary nodes, one pair of secondary nodes, and an external eavesdropper. The primary transmitter multicasts a confidential message to both primary and secondary receivers, while trying to keep it secret from the eavesdropper. The secondary transmitter helps the primary user to deliver its message in exchange of transmission opportunity. The secondary message is unicasted to the secondary receiver, while concealing it from both primary receiver and the eavesdropper. This scenario models a NOMA-based overlay cognitive radio paradigm with an external eavesdropper. For this scenario, the achievable rate-equivocation region is obtained and its optimality is shown for a class of degraded channels. Then, the results obtained for the discrete memoryless channel are extended to the Gaussian channel model. Furthermore, by deploying numerical examples, a comparison is made between the proposed secure NOMA-based scheme, its orthogonal multiple access (OMA) based counterpart, and a cognitive interference channel without an external eavesdropper. It is shown that the NOMA-based method achieves significantly higher rates than its OMA based counterpart.

Achievable rates of Gaussian cognitive interference channel with common interference

This study considers the Gaussian cognitive interference channel (IC), in which one of the two users operates in cognitive mode. In addition, to transmit its signal, the cognitive sender can cooperatively forward the primary signal to its destination, the primary receiver. Moreover, the transmission over this IC also experiences interference from a third source, which is commonly known as the common interferer source. To reduce the effect of both the primary signal and the common interference signal at the secondary destination, both the cognitive transmitter and its destination may have noisy complete (non-causal) or partial (causal) knowledge of these signals. For this channel model, the achievable rate region is computed in which the availability of both the primary signal and the common interference signal at the cognitive transmitter and its destination can be (i) noisy non-causal and (ii) causally estimated. The authors numerical results confirm that knowing both the primary signal and the common interference signal can significantly increase the achievable rate region. Indeed, the obtained achievable rate region is larger than the available bounds in the literature. Furthermore, representative numerical examples are also shown to demonstrate the value of the power allocation at the cognitive source.

LDPC Codes for Interference Channels in the Primary Decodes Cognitive Regime

We investigate cognitive interference channels (CICs), a variant of two-user ICs in which one of the transmitters (called the cognitive transmitter) has non-causal knowledge of the other’s (private user’s) message. Prompted by the information theoretical results, we design an explicit coding scheme for CIC in the primary decodes cognitive regime. We present a novel joint decoder and design low-density parity-check codes for this set-up. Simulation results demonstrate that the proposed joint decoder and the designed codes outperform the conventional maximum ratio combining type decoder and the point-to-point optimal codes, respectively.

An Achievable Region for the Cognitive Interference Relay Channel

In this paper, the causal cognitive interference relay channel (CCIRC) is considered. The CCIRC is obtained from the classic cognitive interference channel by introducing a full-duplex relay that has causal and noisy access to the transmitted signals and aids the communication between the two users. For this channel model, a simple upper bound on the capacity is initially established. Then, we derive an achievable rate region that jointly applies cooperative Han–Kobayashi rate splitting, block Markov encoding, superposition coding, Marton’s binning encoding, and backward decoding. In particular, these bounds are derived for both discrete memoryless model and Gaussian channel. Further, both our theoretical and numerical results indicate that the derived achievable rate region encompasses all known available results in the literature.

Polar Coding for the Cognitive Interference Channel With Confidential Messages

In this paper, we propose a low-complexity, secrecy capacity achieving polar coding scheme for the cognitive interference channel with confidential messages (CICC) under the strong secrecy criterion. Existing polar coding schemes for interference channels rely on the use of polar codes for the multiple access channel, the code construction problem of which can be complicated. We show that the whole secrecy capacity region of the CICC can be achieved by simple point-to-point polar codes due to the cognitivity, and our proposed scheme requires the minimum rate of randomness at the encoder.

On the Devroye–Mitran–Tarokh and Rini–Tuninetti–Devroye Achievable Rate Regions for the Cognitive Interference Channels

This letter includes two important comments on two well-cited papers in the field of the cognitive interference channel (CIC). First, it is shown that the Devroye-Mitran–Tarokh (DMT) achievable rate region for the discrete memoryless CIC can be enlarged by utilizing an important overlooked dependence between secondary auxiliary random variables. Then, it is shown that, with this new change, the strict inclusion of DMT region in an inner bound of the Rini-Tuninetti-Devroye (RTD) achievable region (proved by Rini et al. ) is no longer true between the enlarged (indeed amended) version of DMT region and RTD region. Thus, it is still not clear whether the RTD region is strictly the largest to date known region.

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.

Securing cognitive radio with a combined approach of beamforming and cooperative jamming

The authors consider secret communication through a relay-assisted cognitive interference channel in which primary and secondary base stations (SBSs), respectively, communicate with the primary and secondary receivers (PU-Rx and SU-Rx) in the presence of multiple eavesdroppers. An SBS is allowed to transmit simultaneously with the primary base station (PBS). They propose three cooperative jamming (CJ) schemes based on the available channel state information at the base stations and the relay. The proposed CJ schemes are designed to create additional interference in the direction of eavesdroppers without creating any interference to the PU-Rx and the SU-Rx. A combined approach of beamforming and zero-forcing precoding is developed at the PBS, the SBS and the relay to cancel out jamming interference at the PU-Rx and the SU-Rx. The secrecy rate of SU-Rx is calculated with the constraint of maintaining interference temperature at the PU-Rx under a certain threshold. Compared with the direct transmission schemes that are available in the literature, the authors’ results show that the approach which combined beamforming and CJ significantly improves the secrecy rate of the cognitive interference channel.

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.

The Degrees of Freedom Region of the Cognitive Interference Channel With Delayed Channel State Information Feedback

This paper studies two-user cognitive multiple-input multiple-output (MIMO) interference channel with delayed channel state information at transmitter (CSIT), where a transmitter possesses noncasual knowledge of data originating at the other user. We first derive an upper bound of degrees-of-freedom (DoF) region and then propose DoF bound achieving schemes for various antenna configurations. Since interference condition and interference suppression capability vary with antenna configurations, the proposed DoF optimal schemes differently utilize cognitive transmission based on delayed CSIT to suppress interference and thus differ in the required numbers of time slots and transmit symbols, although the key idea of swapping interfering signals between users is common. Comparing with the DoF regions of relevant channels, we identify and analyze the contributions of cognitive transmission and delay CSIT toward enlarging the DoF region. Our analysis specifies antenna configurations where delayed CSIT and cognitive transmission are useful, respectively.

On Feasibility Conditions for Linear Interference Alignment over Cognitive Interference Channel: A DoF Analysis with Diversity Tradeoff

ABSTRACTIn a multiple-antennas cognitive radio network, the rate of the primary link is maximized by water-filling power allocation along the spatial directions associated with the singular values of primary channel matrix. Due to transmitter power constraint, even when the primary user occupies the entire spectrum, some spatial opportunities remain that can be utilized by secondary users. This scheme is called opportunistic interference alignment (OIA). The feasibility issue of OIA in a general symbol-extended system considering the diversity tradeoff, in particular, is the topic that is considered in this paper. An outer bound on the achievable degrees of freedom and also a necessary condition on the feasibility of a multiuser OIA network are presented analytically. In the remaining parts of the paper, the diversity and rate tradeoff is considered. In order to achieve diversity, it is assumed that the paired nodes utilize a space-time coder before the OIA pre-coder. A closed-form relation is presented that relates the minimum achievable diversity to interference alignment quality and code rate.

Structured Lattice Codes for Some Two-User Gaussian Networks With Cognition, Coordination, and Two Hops

We study a number of two-user interference networks with multiple-antenna transmitters/receivers (MIMO), transmitter side information in the form of linear combinations (over an appropriate finite-field) of the information messages, and two-hop relaying. We start with a cognitive interference channel (CIC) where one of the transmitters (noncognitive) has knowledge of a rank-1 linear combination of the two information messages, while the other transmitter (cognitive) has access to a rank-2 linear combination of the same messages. This is referred to as the network-coded CIC, since such linear combination may be the consequence of some random linear network coding scheme implemented in the backbone wired network. For such channel we develop an achievable region based on a few novel concepts: precoded compute-and-forward (PCoF) with channel integer alignment (CIA), combined with standard dirty-paper coding. We also develop a capacity region outer bound and find the symmetric generalized degrees of freedom (GDoF) region of the network-coded CIC. Through the GDoF characterization, we show that knowing mixed data (linear combinations of the information messages) provides a unbounded spectral efficiency gain over the classical CIC counterpart, if the ratio (in decibel) of signal-to-noise (SNR) to interference-to-noise is larger than certain threshold. Then, we consider a Gaussian relay network having the two-user MIMO IC as the main building block. We use PCoF with CIA to convert the MIMO IC into a deterministic finite-field IC. Then, we use a linear precoding scheme over the finite-field to eliminate interference in the finite-field domain. Using this unified approach, we derive the symmetric sum rate of the two-user MIMO IC with coordination, cognition, and two-hops. We also provide finite-SNR results (not just DoF) which show that the proposed coding schemes are competitive against state-of-the-art interference avoidance scheme based on orthogonal access, for standard randomly generated Rayleigh fading channels.

The Cognitive Interference Channel With a Causal Relay in Very Strong Interference

We study the cognitive interference channel where an additional node (a relay) is present. In our model the relay's operation is causal rather than strictly causal, i.e., the relay's transmit symbol depends not only on its past but also on its current received symbol. We derive outer bounds for the discrete and Gaussian cases in very strong interference. A scheme for achievability based on instantaneous amplify-and-forward relaying is proposed for this model. The inner and outer bounds coincide for a special case of very strong interference.

The Two-User Causal Cognitive Interference Channel: Novel Outer Bounds and Constant Gap Result for the Symmetric Gaussian Noise Channel in Weak Interference

This paper studies the two-user Causal Cognitive Interference Channel (CCIC), where two transmitters aim to communicate independent messages to two different receivers via a common channel. One source, referred to as the cognitive, is capable of overhearing the other source, referred to as the primary, through a noisy in-band link and thus can assist in sending the primary's data. Two novel outer bounds of the type $2R_p+R_c$ and $R_p+2R_c$ are derived for the class of injective semi-deterministic CCICs where the noises at the different source-destination pairs are independent. An achievable rate region is derived based on Gelfand-Pinsker binning, superposition coding and simultaneous decoding at the receivers. The lower and outer bounds are then specialized to the practically relevant Gaussian noise case. The authors of this paper recently characterized to within a constant gap the capacity of the symmetric Gaussian CCIC in (a) the strong interference regime, and (b) for a subset of the weak interference regime when the cooperation link is larger than a given threshold. This work characterizes to within a constant gap the capacity for the symmetric Gaussian CCIC in the regime that was still open. In particular, it is shown that the novel outer bounds are necessary to characterize the capacity to within a constant gap when the cooperation link is weaker than the direct links, that is, in this regime unilateral cooperation leaves some system resources underutilized.

Multi-user Cognitive Interference Channels: A Survey and New Capacity Results

This paper provides a survey of the state-of-the-art information theoretic analysis for overlay multi-user (more than two pairs) cognitive networks and reports new capacity results. In an overlay scenario, cognitive/secondary users share the same frequency band with licensed/primary users to efficiently exploit the spectrum. They do so without degrading the performance of the incumbent users, and may possibly even aid in transmitting their messages as cognitive users are assumed to possess the message(s) of primary user(s) and possibly other cognitive user(s). The survey begins with a short overview of the two-user overlay cognitive interference channel. The evolution from two-user to three-user overlay cognitive interference channels is described next, followed by generalizations to multi-user (arbitrary number of users) cognitive networks. The rest of the paper considers $K$ -user cognitive interference channels with different message knowledge structures at the transmitters. Novel capacity inner and outer bounds are proposed. Channel conditions under which the bounds meet, thus, characterizing the information theoretic capacity of the channel, for both linear deterministic and Gaussian channel models, are derived. The results show that for certain channel conditions distributed cognition, or having a cumulative message knowledge structure at the nodes, may not be worth the overhead as (approximately) the same capacity can be achieved by having only one global cognitive user whose role is to manage all the interference in the network. This paper concludes with future research directions.

Lattice Codes for Many-to-One Interference Channels With and Without Cognitive Messages

A new achievable rate region is given for the Gaussian cognitive many-to-one interference channel. The proposed novel coding scheme is based on the compute-and-forward approach with lattice codes. Using the idea of decoding sums of codewords, our scheme improves considerably upon the conventional coding schemes which treat interference as noise or decode messages simultaneously. Our strategy also extends directly to the usual many-to-one interference channels without cognitive messages. Comparing to the usual compute-and-forward scheme where a fixed lattice is used for the code construction, the novel scheme employs scaled lattices and also encompasses key ingredients of the existing schemes for the cognitive interference channel. With this new component, our scheme achieves a larger rate region in general. For some symmetric channel settings, new constant gap or capacity results are established, which are independent of the number of users in the system.

The Sum-Capacity of the Ergodic Fading Gaussian Cognitive Interference Channel

This paper characterizes the sum-capacity of the ergodic fading Gaussian overlay cognitive interference channel (EGCIFC), a time-varying channel with two source-destination pairs in which a primary/licensed transmitter and a secondary/cognitive transmitter share the same spectrum and where the cognitive transmitter has noncausal knowledge of the primary user's message. The throughput/sum-capacity is characterized under the assumption of perfect knowledge of the instantaneous fading states at all terminals, which are assumed to form an ergodic process. A genie-aided outer bound on the sum-capacity is developed and then matched with an achievable scheme, thereby completely characterizing the sum-capacity of the EGCIFC. The power allocation policy that maximizes the sum-capacity is derived. It is shown that the sum-capacity achieving scheme for an EGCIFC is “separable” in all regimes (i.e., coding across fading states is not necessary), as opposed to the classical interference channel. Extensions to the whole capacity region are discussed. As a capacity achieving scheme for the EGCIFC under certain channel gain conditions, and as a topic of independent interest, the ergodic capacity of a point-to-point multiple-input-single-output channel with per-antenna power constraints and with perfect channel state information at all terminals is also derived.

Cognitive interference channel: achievable rate region and power allocation

In this study, the authors consider a state-dependent two user interference channel. The two users sharing the spectrum are assumed to be cognitive and each user has a non-causal access to the signal from the other user. For this channel model, an achievable rate region is established for both discrete memoryless model and Gaussian channel. In particular, the achievable rate region is obtained by combining Han–Kobayashi rate splitting coding scheme, superposition coding, Gelfand–Pinsker coding scheme and zero-forcing dirty paper coding. Furthermore, the sum rate maximisation and the associated power allocation problem are studied, numerically and theoretically. The corresponding numerical examples show that the proposed combined coding scheme outperforms the existing schemes in the sense of achievable rate region. Moreover, the effectiveness of the optimal power allocation between the two cognitive nodes is also shown.

Bounds and Capacity Theorems for Cognitive Interference Channels With State

A class of cognitive interference channels with state are investigated, in which a primary transmitter sends a message to two receivers (receivers 1 and 2) with assistance of a cognitive transmitter (that knows the primary transmitter’s message), and the cognitive transmitter also sends a separate message to receiver 2. The channel is corrupted by an independent and identically distributed (i.i.d.) state sequence. The scenario, in which the state sequence is noncausally known at both the cognitive transmitter and receiver 2, is first studied. The capacity region is obtained for both the discrete memoryless and Gaussian channels. The second scenario, in which the state sequence is noncausally known only at the cognitive transmitter, is further studied. Inner and outer bounds on the capacity region are obtained for the discrete memoryless channel and its degraded version. The capacity region is characterized for the degraded semideterministic channel and for channels that satisfy a less noisy condition. The Gaussian channels are further studied, which are partitioned into two cases based on how the interference compares with the signal at receiver 1. For each case, inner and outer bounds on the capacity region are derived, and partial boundaries of the capacity region are characterized. The full capacity region is also characterized for channels that satisfy certain conditions. It is shown that certain Gaussian channels achieve the capacity of the same channels with state noncausally known at both the cognitive transmitter and receiver 2.