Tolerable Interference Research Articles

Interference-controlled D2D routing aided by knowledge extraction at cellular infrastructure towards ubiquitous CPS

Device-to-device (D2D) networks underlaying cellular networks are widely recognized as one of the major approaches for ubiquitous information acquisition and exchange, which features the future cyber-physical systems (CPSs). In this paper, we propose the interference-controlled D2D routing designs underlaying cellular networks, i.e. sharing/reusing the cellular spectrum, to support multi-hop D2D transmissions and thus enhancing the flexibility of CPS. The unique feature and challenge for this task include threefolds. First, the huge density of device nodes in future cellular networks yields huge amount of information to process. Second, as device nodes in cellular networks do not maintain the routing table, the route selection via low-complexity knowledge-extraction approach over huge amount of information needs to be performed by the base station (BS). Third, the interference generated by reusing cellular spectrum needs to be thoroughly controlled. To address these issues, we in this work consider two D2D networking scenarios that allow D2D users to share the uplink and downlink spectrum of cellular networks, respectively. Our objective for routing is hop-count minimization such that the delay and power consumptions can be decreased. In particular, we propose a maximum rate towards destination (MR-D) routing algorithm for the scenario sharing uplink spectrum and a MR-D advanced (MR-DA) routing algorithm for the scenario sharing downlink spectrum, respectively. Both algorithms have low computational complexity and thus meaningful for practical systems. Furthermore, our routing designs can avoid the violation of tolerable interferences to cellular users as well as to fulfil the rate requirement of D2D services. Also conducted are abundant simulation evaluations to demonstrate the advantages of our proposed schemes as compared to the baseline schemes including the farthest neighbour routing and closest to destination routing scheme.

Cooperative primary–secondary dynamic spectrum leasing game via decentralized bargaining

Dynamic spectrum leasing (DSL) has been proposed as a solution for better spectrum utilization. Most of the work focused on non-cooperative game to model primary/secondary users interactions in DSL approach. Some others introduced cooperative game just for secondary users (SUs). In this paper, both primary users (PUs) and SUs incentives and level of satisfactions are considered. Nash bargaining is developed with both PUs and SUs as bargainers. A simple pricing approach is introduced which makes the proposed method practically feasible. On one hand, SUs adjust their power regarding to price and tolerable interference which are announced by PU. On the other hand, PU adjusts its tolerable interference to maximize its profit. Simulation results verify the viability of proposed method.

A Pricing Power Control Scheme with Statistical Delay QoS Provisioning in Uplink of Two-tier OFDMA Femtocell Networks

Femtocell is a promising technique to enhance indoor coverage and improve network capacity. Nevertheless, because of the random and co-channel deployment of femtocells, the macrocell will suffer serious cross-tier interference from femtocells in two-tier femtocell networks. Thus, interference mitigation in femtocell networks has been an indispensable task. Meanwhile, with the explosive popularity of smart terminals, especially smart phones and tablets, the wireless networks have loaded a mount of data services with diverse delay quality of service (QoS) requirements. However, due to the stochastically varying nature of wireless physical channel, it is extremely difficult to offer a deterministic delay guarantee in wireless networks. Therefore, the effective capacity of femtocell users (FU) has been introduced to provide a statistical delay QoS provisioning. For that reason, in this paper, we will study the interference mitigation with statistical delay QoS guarantee in uplink two-tier orthogonal frequency division multiple access (OFDMA) femtocell networks. In order to mitigate the cross-tier interference at macrocell base station (MBS), we adopt a price-based power control strategy, in which the MBS protects itself by pricing the interference from FU. Additionally, to guarantee the statistical delay QoS for each FU, effective capacity is introduced into their utility functions. Then, a Stackelberg game is formulated to study the joint utility maximization of the MBS and the FUs subject to a maximum tolerable interference power constraint at the MBS. Subsequently, based on the mathematical analysis of the equilibrium of the formulated Stalkeberg game, a particle swarm optimization (PSO) aided power allocation (PSOPA) algorithm is proposed to solve this optimization problem. At last, simulation results show that our proposed PSOPA algorithm can not only improve significantly the average effective capacity of each FU and guarantee their statistical delay QoS, but also converge successfully.

Core–shell gold–silver nanoparticles based impedimetric immunosensor for cancer antigen CA125

We report a simple and fast assay for cancer antigen CA125 quantification using gold–silver core–shell nanoparticles for ovarian cancer diagnosis and prognosis. The impedimetric analysis of CA125 using label-free and reagentless immunosensor could be used done in 20min. Furthermore, the directed immobilization of antibody onto the core–shell nanoparticles enabled linear response upto 1–150IU/mL (r2=0.994) as opposed to the maximum linear response of 1.0–100.0IU/mL reported for impedimetric immunosensors till date. The fabricated immunosensor displayed tolerable interference of 2.0–5% from serum components and retained 90% stability up to 20 days. Moreover, sensitivity of immunosensor fabricated using Au–Ag nanoparticles (190ΩIU−1mLcm−2) was almost three times that of gold nanoparticles based immunosensor (59ΩU−1mLcm−2).

Resource management for interference mitigation in device‐to‐device communication

Resource management issue is studied for device-to-device (D2D) communication in cellular networks to improve the overall system capacity and spectrum efficiency. Firstly, a lower bound of the interference distance is derived for a D2D user equipment's according to the transmitter density and the quality of servicerequirement of a D2D pair. By using this distance, an interference set can be chosen adaptively based on the interference condition to guarantee the signal-to-interference-plus-noise ratio of the D2D pair at a desired probability. Then, the authors propose two resource allocation schemes, the dual metric scheme and the TID (tolerant interference degree) scheme, to mitigate interference among coexistent D2D pairs. The dual metric scheme aims for uniform resource allocation to avoid excess interference in some resources. The TID scheme is designed to guarantee the interference at each D2D pair tolerable. The simulation results show that both the dual metric scheme and the TID scheme achieve more uniform resource allocation at the cost of a negligible increase of resource usage. Compared with the existing schemes such as the random scheme and the freedom degree scheme, the system performance in terms of resource efficiency is significantly improved by two proposed schemes.

Impact of maximum transmit power limit on the first-order and second-order performance of cognitive opportunistic relaying

This paper focuses on the first-order and second-order performance of dual-hop underlay cognitive radio systems with opportunistic relaying (UCR-OR) over independent and non-identically distributed (i.ni.d) Rayleigh fading channels. For the UCR-OR systems, the tolerable maximum interference power (TMIP) Q at primary users (PUs) and the allowable maximum transmission power limit (AMTP) Pmax at secondary users (SUs) are considered, simultaneously. We first obtain the closed-form solutions to the first-order performance such as outage probability, average symbol error ratio (SER), and ergodic capacity (EC). Secondly, we investigate the second-order statistical performance, i.e., average outage rate (AOR) and average outage duration (AOD). With the consideration that in practice implementation the receiver performance is primarily influenced by the signal-to-noise ratio (SNR) (not the signal envelope), the second-order statistical performance is investigated based on the equivalent instantaneous end-to-end SNR. Finally, we present the detailed performance comparison analysis of UCR-OR systems by defining a random variable μ=Pmax/Q. The results show that the effect of μ on the first-order and second-order performances is different greatly. For the first-order performance, the performance gap is negligible when the value of μ is relatively large. However, for the second-order one, the gap is distinct.

TIE-MAC: tolerable interference estimation-based concurrent medium access control for WLAN mesh networks

This paper proposes TIE-MAC, tolerable interference estimation-based concurrent medium access control protocol for wireless local area network (WLAN) mesh networks. The goal is to increase spatial reuse, achieve high throughput and reduce average energy consumption through exploiting concurrent transmissions among neighbouring nodes. TIE-MAC confirms that the tolerable interference of the receiver plays a key role in determining the efficiency of concurrent transmission scheduling, and puts forward a novel tolerable interference estimation mechanism, enabling the receivers to precisely estimate their tolerable interference. Meanwhile, a concurrent transmission gap (CTG) is inserted between the transmission of the RTS/CTS and data packets to offer the nodes in the vicinity of the receiver the chance to schedule possible overlapping transmissions. The size of the CTG is optimised using an exponential smoothing model-based adjustment algorithm. Moreover, sequenced acknowledgements (ACKs) are introduced in TIE-MAC and used in combination with the tolerable interference estimation mechanism to avoid possible collisions among different concurrent transmissions. Simulation results show that TIE-MAC gains better throughput and energy consumption performance in comparison with existing concurrent transmission protocols as well as the active WLAN mesh standard.

Second Order Suboptimal Power Allocation for MIMO-OFDM Based Cognitive Radio Systems

This paper proposes an efficient and low complexity power-loading algorithm for MIMO-OFDM downlink based cognitive radio system that maximizes the sum rate of single secondary user (SU) under constraints on the tolerable interference thresholds between secondary user and primary user’s frequency bands and the total transmission power. Our suboptimal algorithm is based on the 2 nd order interference tracking and nulling mechanism to allocate transmission power of the subcarriers among SU’s scheme. The performance of our proposed suboptimal scheme is compared with the performance of the classical power loading algorithms, e.g., water filling, 1 st order interference tracking, nulling, and other suboptimal schemes. Numerical results show that our algorithm has low complexity but obtains a higher channel capacity than that of some previous suboptimal algorithms in some scenarios. We dedicate also that for a given interference threshold, the 2 nd order interference tracking mechanism has dynamic number of nulling position instead fixed number of nulling position.

Utility-based joint Power and Rate Control Game with Interference Threshold Elasticity for Cooperative Cognitive Networks

In cognitive networks, the cognitive radio users can share spectrum resource with the primary user while ensuring the normal communication of primary user. In addition, next generation wireless systems needs to provide flexible transmission rate to each terminal. In this paper, a utility-based game-theoretic model is proposed to study the joint power and rate control problem in spectrum underlay fashion in cognitive networks. We adopt a novel utility function based on cognitive network which focuses on social optimal resource allocation through pricing. Further, we show an interference threshold elasticity perspective, which is the key for primary network to maximize its utility by increasing its transmitted power to adjust the tolerable interference constraint. And also, the cognitive network can increase its total throughput capacity. In Stackelberg game, the primary user and the cognitive radio users interact with each other by adjusting their own actions. The cooperative cognitive networks model follows the “best-effort” principle as well as the win-win perspective of primary-cognitive user. Numerical simulations are conducted to demonstrate the performance of the model. The results show that the PU network can get more profit and also the CRU network can increase its total throughput capacity by the adjustment of the interference threshold.

Tier-Aware Resource Allocation in OFDMA Macrocell-Small Cell Networks

We present a joint sub-channel and power allocation framework for downlink transmission in an orthogonal frequency-division multiple access (OFDMA)-based cellular network composed of a macrocell overlaid by small cells. In this framework, the resource allocation (RA) problems for both the macrocell and small cells are formulated as optimization problems. For the macrocell, we formulate an RA problem that is aware of the existence of the small cell tier. In this problem, the macrocell performs RA to satisfy the data rate requirements of macro user equipments (MUEs) while maximizing the tolerable interference from the small cell tier on its allocated sub-channels. Although the RA problem for the macrocell is shown to be a mixed integer nonlinear problem (MINLP), we prove that the macrocell can solve another alternate optimization problem that will yield the optimal solution with reduced complexity. For the small cells, following the same idea of tier-awareness, we formulate an optimization problem that accounts for both RA and admission control (AC) and aims at maximizing the number of admitted users while simultaneously minimizing the consumed bandwidth. Similar to the macrocell optimization problem, the small cell problem is shown to be an MINLP. We obtain a sub-optimal solution to the MINLP problem relying on convex relaxation. In addition, we employ the dual decomposition technique to have a distributed solution for the small cell tier. Numerical results confirm the performance gains of our proposed RA formulation for the macrocell over the traditional resource allocation based on minimizing the transmission power. Besides, it is shown that the formulation based on convex relaxation yields a similar behavior to the MINLP formulation. Also, the distributed solution converges to the same solution obtained by solving the corresponding convex optimization problem in a centralized fashion.

Underlay cooperative af relaying in cellular networks: performance and challenges

Cognitive radio is a promising technique to resolve the growing scarcity of the indispensable spectrum resources in wireless applications. Among its three major implementation paradigms, namely, interweave, overlay and underlay, underlay CR is the most flexible. However, the transmit power of secondary users (SUs) having to be strictly limited by the prescribed tolerable interference power dictated by primary users (PUs), confines underlay CR to short-range communications. To address this limitation, cooperative amplify-and-forward (AF) relaying techniques can be exploited to extend the coverage area and reduce the interference region of secondary transmission with low implementation complexity. Nevertheless, despite the significant potential of cooperation in underlay CR systems, advances in this context have been limited so far, mainly due to the extreme difficulty of mathematical tractability involved in the performance evaluation and design of these systems. This article aims to overview recent advances in this area. In particular, important dominating factors on system performance of underlay cooperative AF relaying in cellular networks are identified, in terms of cochannel interference coming from concurrent primary transmission, relay selection, number of relaying hops, and imperfect channel state information (CSI). Moreover, we outline some future research topics in this exciting area.

Spectrum-Sharing Multi-Hop Cooperative Relaying: Performance Analysis Using Extreme Value Theory

In spectrum-sharing cognitive radio systems, the transmit power of secondary users has to be very low due to the restrictions on the tolerable interference power dictated by primary users. In order to extend the coverage area of secondary transmission and reduce the corresponding interference region, multi-hop amplify-and-forward (AF) relaying can be implemented for the communication between secondary transmitters and receivers. This paper addresses the fundamental limits of this promising technique. Specifically, the effect of major system parameters on the performance of spectrum-sharing multi-hop AF relaying is investigated. To this end, the optimal transmit power allocation at each node along the multi-hop link is firstly addressed. Then, the extreme value theory is exploited to study the limiting distribution functions of the lower and upper bounds on the end-to-end signal-to-noise ratio of the relaying path. Our results disclose that the diversity gain of the multi-hop link is always unity, regardless of the number of relaying hops. On the other hand, the coding gain is proportional to the water level of the optimal water-filling power allocation at secondary transmitter and to the large-scale path-loss ratio of the desired link to the interference link at each hop, yet is inversely proportional to the accumulated noise, i.e. the product of the number of relays and the noise variance, at the destination. These important findings do not only shed light on the performance of the secondary transmissions but also benefit system designers improving the efficiency of future spectrum-sharing cooperative systems.

Optimizing compatible sets in wireless networks through integer programming

In wireless networks, the notion of compatible set refers to a set of radio links that can be simultaneously active with a tolerable interference. Finding a compatible set with maximum weighted revenue from the parallel transmissions is an important optimization subproblem for resource management in wireless networks. For this subproblem, two basic ways of expressing the signal-to-interference-plus-noise-ratio within integer programming are used, differing in the number of variables and the quality of the upper bound given by their linear relaxations. To our knowledge, there is no systematic study comparing the effectiveness of these two approaches to the compatible set optimization problem. The contribution of the article is twofold. First, we present a comparison of the two basic approaches, and, second, we introduce matching inequalities that improve the upper bounds achievable with the two basic approaches. The matching inequalities are generated within the branch-and-cut process using a minimum odd-cut generation procedure based on the Gomory–Hu tree algorithm. The article presents results of a numerical study illustrating our statements and findings.

Price‐based interference management in dense femtocell systems

SUMMARYFemtocell technology has been drawing considerable attention as a cost‐effective means of improving cellular coverage and capacity. However, under co‐channel deployment, femtocell system in dense environment may incur high uplink interference to existing macrocells and experiences strong inter‐cell interference at the same time. To manage the uplink interference to macrocell, as well as the inter‐cell interference, this paper proposes a price‐based uplink interference management scheme for dense femtocell systems. Specifically, on the one hand, to guarantee the macrocell users' quality of service, the macrocell base station prices the interference from femtocell users (FUEs) subject to a maximum tolerable interference power constraint. On the other hand, the inter‐cell interference is also taken into consideration. Moreover, a Stackelberg game model is adopted to jointly study the utility maximization of the macrocell base station and FUEs. Then, in order to reduce the amount of information exchange, we design a distributed power allocation algorithm for FUEs. In addition, admission control is adopted to protect the active FUEs' performance. Numerical results show that the price‐based interference management scheme is effective. Meanwhile, it is shown that the distributed power allocation combined with admission control is capable of robustly protecting the performance of all the active FUEs. Copyright © 2013 John Wiley & Sons, Ltd.

Integer programming models for maximizing parallel transmissions in wireless networks

In radio communications, a set of links that can transmit in parallel with a tolerable interference is called a compatible set. Finding a compatible set with maximum weighted revenue of the parallel transmissions is an important subproblem in wireless network management. For the subproblem, there are two basic approaches to express the signal to interference plus noise ratio (SINR) within integer programming, differing in the number of variables and the quality of the upper bound given by linear relaxations. To our knowledge, there is no systematic study comparing the effectiveness of the two approaches. The contribution of the paper is two-fold. Firstly, we present such a comparison, and, secondly, we introduce matching inequalities improving the upper bounds as compared to the two basic approaches. The matching inequalities are generated within a branch-and-cut algorithm using a minimum odd-cut procedure based on the Gomory-Hu algorithm. The paper presents results of extensive numerical studies illustrating our statements and findings.

A GENERALIZED NASH EQUILIBRIUM PROBLEM FOR CENTRALIZED DYNAMIC SPECTRUM LEASING

The dramatic increase of wireless devices in telecommunications is underlining the inefficiency of the traditional spectrum allocation system. A novel scheme for resource allocation is the Dynamic Spectrum Sharing (DSS), where primary users, the exclusive owners of the spectrum rights, allow the secondary ones to share their licensed frequency band. In this paper, a time-continuous model is presented for Centralized Dynamic Spectrum Leasing (C-DSL). This kind of model involves the active participation of both the primary and secondary users in order to share the same frequency band. I treat the problem of secondary power allocation like a non-cooperative Generalized Nash Equilibrium Problem (GNEP) where the primary commu- nication system is willing to allow the secondary users to share its spectrum band and consequently adjusts the maximum tolerable interference in order to obtain the greatest gain, while the secondary users play the game by choosing the most convenient powers to be allocated, in order to obtain a good quality signal and avoid an excessive interference. I give mathematical conditions, easy to be verified locally at the secondary receivers, that ensure the existence of a Generalized Nash Equilibrium for the game.

An electrochemical impedimetric immunosensor for ultrasensitive determination of ketamine hydrochloride

In this paper, an immunosensor for ultrasensitive and specific detection of ketamine is reported with electrochemical impedance as read-out signal. It is constructed based on the self-assembly modification (SAM) of 3-mercaptopropionic acid on Au electrode, the activation strategy by 1-ethyl-3-(3-dimethylaminoprophyl) carbodiimide (EDC)/n-hydroxysulfsuccinimide (NHS) and the immobilization of ketamine antibody to form the sensing surface. The antibody acts as the sensing host due to its specific covalent bonding with ketamine. The technique of electrochemical impedance spectroscopy (EIS) is employed to read-out the sensing signal. The value of electron transfer resistance (Ret) responds to the concentration of ketamine with a detection limit of 0.41pmol/L. The immunosensor can be regenerated for more than 5 times resorted to elution by NaOH–H3PO4 (pH 12.0). When it was applied to detect the ketamine in spiked serum samples after 2000-folds dilution, there were satisfactory recoveries from 89.0% to 136.4% and tolerable interference from blood components. The so-prepared sensor is proven as a dominant element than those once reported ones in terms of the sensitivity and simplicity.

Stackelberg game based interference management for two-tier femtocell networks

Femtocell is viewed as a promising option for mobile operators to improve coverage and provide high-data-rate services in a cost-effective manner. This paper considers the uplink interference management problem in a spectrum-sharing femtocell network. Assuming that the macrocell base station (MBS) is rewarded for sharing the spectrum with femtocells by setting a reasonable interference cap (IC) for femtocell users’ (FUEs’) transmissions. Within IC, the FUEs allocate their transmission powers competitively while not introducing much interference to both the macrocell users (MUEs) and other FUEs. A Stackelberg game is formulated to jointly maximize the utility of MBS and the individual utility of FUEs. Specifically, the maximum tolerable interference at the MBS is used as the resource that the leader (MBS) and the followers (FUEs) compete for. Then, the backward induction method is applied to achieve the Stackelberg equilibrium and a distributed power update rule is developed for FUEs. In addition, the implementation protocol is presented, some issues related to the implementations and some future extensions regarding the MUEs’ uplink protection are discussed. Lastly, numerical results demonstrate the performance of our proposed power allocation in detail, and show the effects of varying the number of FBSs and changing other system parameters on the system’s performance.

Price-based interference control for two-tier femtocell networks

This paper presents a novel price-based interference control scheme for two-tier femtocell networks, aiming to limit the interference from femtocell users to macrocell base station (MBS). Assuming that the MBS protects itself by pricing the interference power from the femtocell users, the femtocell users set their transmission powers by competitively selecting the interference power fractions under the constraint of the total tolerable interference. The problem of femtocell users’ competitive interference occupation process is cast into a non-cooperative interference power purchase game, and the existence and uniqueness of the Nash equilibrium is proved. Then, a distributed interference power fraction iterative algorithm is developed to find the Nash equilibrium of the game, and the convergence analyses in both synchronous and asynchronous cases are presented. The distributed implementations are also shown. Simulation results show the convergence of the interference power fraction iterative algorithm and the effectiveness of the proposed interference control scheme.

Cooperative AF Relaying in Spectrum-Sharing Systems: Outage Probability Analysis under Co-Channel Interferences and Relay Selection

For cooperative amplify-and-forward (AF) relaying in spectrum-sharing wireless systems, secondary users share spectrum resources originally licensed to primary users to communicate with each other and, thus, the transmit power of secondary transmitters is strictly limited by the tolerable interference powers at primary receivers. Furthermore, the received signals at a relay and at a secondary receiver are inevitably interfered by the signals from primary transmitters. These co-channel interferences (CCIs) from concurrent primary transmission can significantly degrade the performance of secondary transmission. This paper studies the effect of CCIs on outage probability of the secondary link in a spectrum-sharing environment. In particular, in order to compensate the performance loss due to CCIs, the transmit powers of a secondary transmitter and its relaying node are respectively optimized with respect to both the tolerable interference powers at the primary receivers and the CCIs from the primary transmitters. Moreover, when multiple relays are available, the technique of opportunistic relay selection is exploited to further improve system performance with low implementation complexity. By analyzing lower and upper bounds on the outage probability of the secondary system, this study reveals that it is the tolerable interference powers at primary receivers that dominate the system performance, rather than the CCIs from primary transmitters. System designers will benefit from this result in planning and designing next-generation broadband spectrum-sharing systems.