Interference Temperature Limit Research Articles

Performance of Novel Adaptive Schemes for Cognitive Full-Duplex Relaying-Based Downlink Cooperative NOMA

In this paper, we demonstrate that due to large variations in link signal-to-noise-ratios, the key to good performance in underlay cooperative non-orthogonal multiple access (CNOMA) is intelligent adaptation. First adaptation involves switching between the cooperative mode (CM) and the non-cooperative mode (NCM). While a full-duplex near user (NU) assists the multiple-antenna base-station in communication to a far user (FU) in CM, allowing the NU to switch to NCM ensures that its performance is same as in a network without the FU. The second adaptation relates to transmit antenna selection. In the first scheme, the NOMA power allocation parameter (NPAP), and the interference temperature limit (ITL) apportioning parameter (ITLAP) depend on channel statistics. The third adaptation (presented for the first time in literature) used in two other proposed schemes involves selection of inter-dependent NPAP and ITLAP based on channel state information (CSI). The fourth adaptation used in the third proposed scheme relates to use of CSI-dependent ITL, which is shown to dramatically improve performance. Optimum choices of NPAP and ITLAP are expressed in closed-form for all three schemes, and performance with these is analyzed (and validated by computer simulations) assuming imperfect successive interference cancellation and residual self-interference cancellation at the NU.

Performance of CDRT-Based Underlay Downlink NOMA Network With Combining at the Users

The performance of an underlay coordinated direct and relay transmission (CDRT) based non-orthogonal multiple access (NOMA) network is limited by the random nature of the transmit powers due to the interference temperature limit (ITL) imposed by the primary network. In this paper, we show that combining the signals at both near and far users can significantly enhance throughput. Considering the practical scenario of imperfect successive interference cancellation, the performance of near and far user nodes is analyzed in terms of throughput and outage probability. The traditional case of static ITL is considered first. Then, analysis is presented for the case when the ITL depends on the primary channel state information, and it is shown that the gain in performance can be very large over static ITL. Closed-form expressions for NOMA power apportioning are presented for a special case. Further, it is shown that how optimum parameters can be chosen to maximize the performance. Simulations validate the derived analytical expressions.

Comparison of Different Frequency Channel Allocation Methods in ultra-dense networks

The impact of information transmission on production and life under dense networking is self-evident. Dense networking application scenarios include airports, dense residential buildings, dense business districts and blocks, campuses, large gatherings, stadiums, subways, etc. However, with the increase of 5G frequency band, the 5G macro base station signal attenuates more when it penetrates the wall than 4G, which makes it difficult to cover indoor signals. The outdoor 5G macro base station signal can only provide shallow indoor coverage after penetrating obstacles such as brick walls, glass and cement, which cannot guarantee the good experience required for indoor deep coverage. This paper compares and discusses various channel allocation algorithms based on user scenarios in ultra-dense networks. By adjusting some parameters of 19 units, the integer frequency reuse (IFR) method (N=1,3), fractional frequency reuse (FFR) method, simultaneous water injection (SWF) method, and transmission interference temperature limit (TX-ITL) method are compared. In order to increase the capacity, a combination of several algorithms will also be used.

Performance of NOMA-Enabled Cooperative FD D2D Communication in Cellular Underlay

This paper investigates the performance of non-orthogonal multiple access (NOMA) enabled device-to-device (D2D) communication underlaid in the cellular uplink. The uplink cellular user is also a full-duplex, decode and forward relay assisting in D2D communication. To guarantee the desired QoS, the interference due to D2D transmissions caused to the cellular base station is kept below an interference temperature limit (ITL). Since the D2D source and the cellular user transmit D2D symbols concurrently, the ITL is apportioned between them using an ITL apportioning parameter (ITLAP) to determine their transmit powers. Both ITL and ITLAP can be statistical quantities or channel state information (CSI) dependent. Based on various degrees of channel knowledge, this work presents three different schemes. We first consider the case when both ITL and ITLAP are statistically determined quantities in the statistical channel aware (SCA) scheme. The second is the cellular channel aware (CCA) scheme, where an adaptive ITL is considered based on uplink channel conditions. The third is the full channel aware (FCA) scheme, which yields the best performance. For all three schemes, we determine expressions for D2D throughput in closed-form. Computer simulations validate the accuracy of the derived expressions.

Performance of CSI-Based Power Control and NOMA/OMA Switching for Uplink Underlay Networks With Imperfect SIC

In a multiuser underlay uplink network, we show that despite the fact that the transmit powers are constrained by the interference temperature limit (ITL) imposed by the primary network, allowing upto two users to concurrently transmit using non-orthogonal multiple access (NOMA) principles ensures better performance than when only a single user is picked in an orthogonal multiple access (OMA) scheme. To deal with the large variation in the link SNRs in underlay networks, an optimal channel state information (CSI) based ITL apportioning scheme is suggested for the first time in literature that carefully controls the transmit powers of the selected users to maximize throughput. CSI-based throughput-optimal strategies are evolved for user selection and NOMA/OMA switching. We analyze the throughput performance of the uplink with NOMA/OMA switching, optimal user selection, and CSI based ITL apportioning, taking successive interference cancellation (SIC) errors into account. Useful bounds on performance are also derived. It is shown that when the ITL is broadcast in every coherence interval, and the ITL can also be channel dependent, large thoughput gains accrue. Computer simulations confirm accuracy of the derived expressions.

Resource Optimization of D2D-Assisted CR Network With NOMA for 5G and Beyond Systems

Device-to-device (D2D) communication has emerged as a potential candidate for 5G and beyond networks to optimize spectrum utilization, reduce power consumption, and support higher data rates. The energy and spectral efficiency of D2D communication can be enhanced further by adapting cognitive radio (CR), nonorthogonal multiple access (NOMA), and radio-frequency energy harvesting (RF-EH) technologies. Therefore, this article proposes a sum-rate maximization problem for a D2D-assisted CR network with NOMA, considering the RF-EH mechanism. A joint optimization problem is modeled to maximize the sum throughput of cellular and D2D nodes by considering power assignments, radio resource allocation, user pairing, and transmission time ratio assignment. The problem is then converted into a standard convex optimization problem subject to power allocations at individual nodes, interference temperature limits, individual data rate, and secrecy capacity. The duality theory is adopted to decompose the problem into multiple subproblems, and Karush–Kuhn–Tucker (KKT) conditions are applied to provide the solution. Finally, the proposed schemes are validated through simulation results. The proposed schemes outperform the existing schemes in terms of sum throughput and energy harvesting under different quality of service requirements.

Performance of Adaptive Multi-User Underlay NOMA Transmission With Simple User Selection

In this paper, we demonstrate that despite the power constraints on all transmit nodes caused by the interference temperature limit (ITL) imposed by the primary user, power domain cooperative non-orthogonal multiple access (NOMA) can ensure much higher throughput in underlay cognitive radio networks than conventional orthogonal multiple access (OMA), provided the network is adaptive. We use intelligent user-selection and switching between cooperative NOMA, (non-cooperative) NOMA and OMA to ensure high throughput at the selected far-user while ensuring a desired performance at the selected near-user. The suggested user and mode selection scheme is simple and easy to implement, and yet ensures performance comparable to that attained by a scheme using more information. When the ITL is broadcast by the primary receiver in every coherence interval based on the primary channel, we show that large gains in throughput accrue. Accurate expressions are derived for throughput of the near and far users with these schemes using peak power and ITL-based power constraints. Performance with imperfect successive interference cancellation is also analyzed. Useful asymptotic expressions are derived. Computer simulation results validate the derived expressions.

Transmit power control and data rate enhancement in cognitive radio network using computational intelligence

Underutilized radio frequencies are the chief apprehension in advance radio communication. The radio recourses are sparse and costly and their efficient allocation has become a challenge. Cognitive radio networks are the ray of hope. Cognitive radio networks use dynamic spectrum access technique to opportunistically retrieve and share the licensed spectrum. The licensed users are called primary users and the users that opportunistically access the licensed spectrum all called secondary users. The proposed system is a feedback system that work on demand and supply concept, in which secondary receivers senses the vacant spectrum and shares the information with the secondary transmitters. The secondary transmitters adjust their transmission parameters of transmit power and data rate in such a way that date rate is maximized. Two methods of spectrum access using frequency division multiple access (FDMA) and Time division multiple access (TDMA) are discussed. Interference temperature limit and maximum achievable capacity are the constraints that regulate the entire technique. The aim of the technique is to control the transmitter power according to the data requirements of each secondary user and optimizing the resources like bandwidth, transmit power using machine learning and feed forward back propagation deep neural networks making full use of the network capacity without hampering the operation of primary network.

Cooperative Mode Switching-Based Cognitive NOMA With Transmit Antenna and User Selection

The paper presents performance analysis of a multiuser Cooperative Non-Orthogonal Multiple Access (CNOMA) network that is underlay to a primary network. A selected secondary Full-Duplex (FD) Near User (NU) cooperates with a selected secondary Far User (FU) by apportioning the Interference Temperature Limit (ITL) with an ITL Apportioning Parameter (ITLAP). This Cooperative Mode (CM) is exercised only when NU meets its own performance criteria, else the network switches to a Non-Cooperative Mode (NCM). The network is therefore made adaptive in such a way that performance of the NU is same as in a network without the FU. Performance of the network is further improved using Maximum Transmit Power-based Transmit Antenna Selection (MTP-TAS), Best NU-Best FU (BNBF) selection, and optimal power allocation, thereby also motivating NOMA even in power-constrained underlay environments where transmit powers are not always high. The selection mechanisms are designed in a way that additional overheads for Channel State Information (CSI) estimation and feedback are not imposed. Analytical expressions for outage probability are presented for both end users, assuming only statistical knowledge of channel gains under the assumption of imperfect Successive Interference Cancellation (SIC) at the NU. Outage minimizing optimal values of the NOMA Power Allocation Parameter (NPAP) and ITLAP are derived that minimize FU outage. Simulations validate the derived expressions, and demonstrate superiority of the proposed scheme over FD NU-based conventional NOMA as well as conventional OMA signalling.

Channel Power Allocation Optimization Based on Water-filling Algorithm in 5G

Since entering the information age, the popularity of mobile communication has become higher and higher, and people’s requirements for communication quality are also increasing, but the channel resources that people can control are limited. This paper proposes an optimization algorithm for channel resource allocation based on water-filling algorithm. Some improvements have been made on the basis of the original water-filling algorithm. The sgn function is used to optimize the transmit interference temperature limit (Sk), so that the screening result is not completely dependent on Sk, which improves the flexibility of channel screening and effectively optimizes the capacity of the communication network.

Analysis of spectral efficiency for OFDM cooperative cognitive networks with non‐linear relay

This paper analyzes the downlink achievable spectral efficiency of an orthogonal frequency-division multiplexing (OFDM) cooperative cognitive network with a non-linear relay. The analysis is carried out subject to the power amplifier's (PA) non-linear effect on the relay node which operates in the amplify-and-forward (AF) mode. Specifically, an analytical expression for the power spectral density (PSD) of relay output in terms of its source power is derived. By using the obtained PSD, the power of relay's PA output is derived for each subcarrier and the 1 dB compression point is determined. Then, the adjacent channel power (ACP) of each subcarrier is analytically derived in terms of secondary user (SU) source input power. Next, the signal to interference and noise ratio (SINR) of each subcarrier at destination (SU receiver) is calculated by considering the non-linear effect of PA at the relay. Having the SINRs of all subcarriers, a constrained optimization problem on the source's input power is formulated in which the achievable spectral efficiency is the objective function and all ACPs being less than the interference temperature limit are its constraints. Finally, we perform some simulations and show that the numerical results are consistent with the analytical findings.

Joint Impact of Nodes Mobility and Imperfect Channel Estimates on the Secrecy Performance of Cognitive Radio Vehicular Networks Over Nakagami-m Fading Channels

This paper investigates the joint impact of nodes' mobility and imperfect channel estimates on the secrecy performance of an underlay cognitive radio vehicular network over Nakagami-m fading channels. Specifically, the secondary network consists of a single-antenna source vehicle, an N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> D</sub> -antenna destination vehicle, and an N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> E</sub> -antenna passive eavesdropper vehicle, whereas the primary network comprises of a single-antenna primary receiver vehicle. The time selective fading links arise due to nodes' mobility are modeled via first-order auto-regressive process, and the channel state information is estimated using linear minimum mean square error estimation method. Moreover, the transmit power of secondary source is constrained by both the interference threshold of the primary receiver and the maximum transmit power of secondary network. Under such a realistic scenario, we derive the analytical closed-form secrecy outage probability (SOP) and ergodic secrecy capacity expressions. Furthermore, we present asymptotic SOP analysis to obtain key insights into the system's secrecy diversity order. We also report several practical cases of interest to reveal valuable information about the system's secrecy behavior. Moreover, we illustrate the impacts of system/channel parameters, nodes' mobility, imperfect channel estimates, interference temperature limit, and the maximum available source power. Finally, the simulation studies corroborate our derived analytical findings.

Optimal spectrum utilisation in cognitive radio networks based on processor sharing techniques

SummaryCognitive radio networks have achieved higher efficiency in terms of spectrum usage; however they do not readily solve any competition for access among secondary users. Optimisation is applied to an underlay network to obtain the optimal solution for at least two secondary users operating simultaneously on the same channel. Performance measures are used as the target for optimisation. However, the objective function is difficult to obtain in closed form. For the performance measures, queueing theory, particularly weighted processor sharing techniques are employed to model the system dynamics and behaviour. Transmission power and the interference temperature limit are used to allocate weights to the secondary users. Queue length and waiting time functions obtained from the queuing models are used for optimisation. After establishing that the objective function can be considered to be pseudo‐convex, convex programming is then deployed to obtain the optimised solution. The results suggest that there is indeed an improvement in network performance after optimisation. The immediate benefits of such a system are firstly improved spectrum utilisation through adding multiple secondary users and secondly, through optimisation, higher performance that can be achieved by the secondary users.

Joint User Pairing, Channel Assignment and Power Allocation in NOMA based CR Systems

The fifth generation (5G) wireless communication systems promise to provide massive connectivity over the limited available spectrum. Various new transmission paradigms such as non-orthogonal multiple access (NOMA) and cognitive radio (CR) have emerged as potential 5G enabling technologies. These techniques offer high spectral efficiency by allowing multiple users to communicate on the same frequency channel, simultaneously. A combination of both techniques may further enhance the performance of the system. This work aims to maximize the achievable rate of a multi-user multi-channel NOMA based CR system. We propose an efficient user pairing, channel assignment and power optimization technique for the secondary users while the performance of primary users is guaranteed through interference temperature limits. The results show that, at small values of the power budget or high interference threshold, optimizing channel allocation and user pairing proves to be more beneficial than optimal power allocation to the user pairs. The proposed joint optimization technique provides promising results for all values of the power budget, interference threshold and rate requirement of the communicating users.

Securing Primary Downlink Transmissions From Untrusted Receivers of Co-Existing Underlay Cognitive Networks

In a recent paper, network management rules were evolved to maximize sum throughput of two co-existing underlay secondary networks that reuse the spectrum of a licensed primary network. Such rules require secondary networks to either transmit concurrently by optimal apportioning of the interference temperature limit (ITL), or in isolation. In this paper, we analyze the secrecy outage performance of the primary downlink network for a scenario when receivers of the two co-existing secondary networks are untrusted and eavesdrop on the primary downlink transmissions. We analytically establish that it is only when secondary networks transmit concurrently, that the primary network is most secure. Further, we derive an optimum ITL apportioning mechanism that guarantees maximum secrecy for the primary network, and also present closed-form expressions in a special case. The optimum apportioning parameter shows that the network management rule that maximizes secrecy of the primary network is not the same as that which maximizes secondary sum throughput. Computer simulations are presented that demonstrate accuracy of the derived expressions.

Space shift keying modulation under spectrum sharing over Nakagami‐m fading

In this letter, we analyze the performance of the space shift keying (SSK) modulation scheme for underlay spectrum‐sharing environments. For underlay spectrum‐sharing transmission, the transmit power condition of the proposed spectrum‐sharing system is considered by the interference temperature limit on the primary network and the maximum transmission power at the secondary network. Closed‐form expression for the average bit error probability (ABEP) is derived for Nakagami‐m fading channels. The obtained expression contains a hypergeometric function. Numerical and simulation results are presented to illustrate the impact of the fading parameters on the system performance.

Joint power and admission control based on hybrid users in cognitive radio network

• We study the problem of joint power and admission control in spectrum underlay cognitive radio network based on hybrid users. • Hybrid users are advanced primary users that are able to access the secondary network using their cognitive functions. • An advanced cognitive radio network (ACRN) is proposed by employing the hybrid users. • We show that such ACRN can remarkably improve the network performance in terms of the number of supported secondary users, transmit power and aggregate throughput. Hybrid users or primary-secondary users (PSUs) are advanced primary users that are able to access the secondary network using their cognitive functions. Hybrid users can appear as a new type of cognitive users that would be promising for future cognitive radio networks (CRNs). Regarding the unique capabilities of such users and due to the lack of considerable research on this subject, we study the problem of joint power and admission control in spectrum underlay CRN based on hybrid users. In order to fully take the advantages of cognitive capability, an advanced cognitive radio network (ACRN) is proposed by employing the PSUs, and the corresponding power and signal-to-interference-plus-noise ratio (SINR) are derived. Then, feasibility checking mechanism is investigated and the optimal value of interference temperature limit for PSUs is also obtained. A new formulation to maximize the number of admitted secondary users (SUs) in ACRN is presented. Moreover, two power and admission control algorithms are proposed which significantly improve the network performance not only in the number of admitted SUs but also in transmit power consumption. For a feasible network, the problem of aggregate throughput maximization is solved using successive geometric programming. Afterwards, it is proved that our proposed ACRN can improve the aggregate throughput of SUs. The superior efficiency of ACRN in terms of the number of admitted SUs, transmit power consumption and aggregate throughput is verified by simulation results for different scenarios.

Optimizing Performance of Co-Existing Underlay Secondary Networks

In this paper, we analyze sum throughput and (asymptotic) sum ergodic rate performance of two co-existing downlink multiuser underlay secondary networks employing either fixed-rate transmission (FRT) or (channel aware) adaptive rate transmission (ART). In the considered scenario in which two secondary sources may transmit simultaneously, intelligent apportioning the interference temperature limit (ITL) is vital. We consider cases when this ITL apportioning is based on statistical properties of the channels, or on full (or partial) knowledge of the channel gains. For these cases, proper network management (NM) strategies are evolved to maximize sum throughput or sum ergodic rate of the secondary networks. Each NM strategy determines whether both secondary sources should transmit concurrently or not, and also determines their transmit powers. We demonstrate that a channel aware NM strategy is superior to an optimal fixed NM strategy. With secondary sources employing non-opportunistic user selection, in case of FRT (ART), we demonstrate that there exists a critical target-rate (ITL) below which it is advantageous to operate both secondary networks concurrently. We present closed form expressions of critical parameters that influence sum throughput and sum ergodic rate. Computer simulations are presented to corroborate the derived expressions.

Secrecy Performance of an Idle Receiver Assisted Underlay Secondary Network

In this letter, we derive an expression for the secrecy outage probability of a multiuser underlay downlink in which a selected idle secondary user serves as a friendly jammer to enhance physical-layer secrecy of secondary downlink communication in the presence of a passive eavesdropper. Secondary nodes constrain their transmit powers to ensure that the interference caused to the primary network is below an interference temperature limit I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</sub> . We show that careful apportioning of IP between the secondary source and the selected jammer (which transmit simultaneously), and judicious choice of peak powers, is the key to improving secrecy performance. Computer simulation results demonstrate accuracy of the derived expressions.

Non-Orthogonal Multiple Access Based Integrated Terrestrial-Satellite Networks

In this paper, we investigate the downlink transmission of a non-orthogonal multiple access (NOMA)-based integrated terrestrial-satellite network, in which the NOMA-based terrestrial networks and the satellite cooperatively provide coverage for ground users while reusing the entire bandwidth. For both terrestrial networks and the satellite network, multi-antennas are equipped and beamforming techniques are utilized to serve multiple users simultaneously. A channel quality-based scheme is proposed to select users for the satellite, and we then formulate the terrestrial user pairing as a max-min problem to maximize the minimum channel correlation between users in one NOMA group. Since the terrestrial networks and the satellite network will cause interference to each other, we first investigate the capacity performance of the terrestrial networks and the satellite networks separately, which can be decomposed into the designing of beamforming vectors and the power allocation schemes. Then, a joint iteration algorithm is proposed to maximize the total system capacity, where we introduce the interference temperature limit for the satellite since the satellite can cause interference to all base station users. Finally, numerical results are provided to evaluate the user paring scheme as well as the total system performance, in comparison with some other proposed algorithms and existing algorithms.