Interference Mitigation Mechanisms Research Articles

ISense: Intelligent Object Sensing and Robot Tracking Through Networked Coupled Magnetic Resonant Coils

Object sensing and tracking using electric and magnetic fields allow intelligent interaction, automation, and adaptation in cyber–physical systems. Our approach, called iSense, uses a software-defined collaborative sensing technique for the detection of the type of object when placed on a large surface and tracking its mobility. iSense is cost effective, low power, and scalable, which allows its use over large surfaces. First, we introduce a dual-coil magnetic resonant sensing architecture based on nested coils, i.e., passive (outer) and active (inner) coils, for low-power contactless sensing. Second, a data-driven support vector machine-based approach helps to classify different types of objects using the voltage readings obtained at the passive coil. iSense combines sensed voltage information from multiple different coils spread over the surface with a group-based interference mitigation mechanism between coils for collaborative sensing. We validate our system with real-time prototype and experimental evaluations. We demonstrate the detection of seven different types of objects over three different materials, and real-time detection and tracking of mobile objects including a robot car. Experimental results show that each sensing coil only consumes few milliwatts, i.e., $18\times $ less than inductive sensing and $15\times $ less than classical magnetic resonance sensing, extend sensing depth to 3 cm, and enable tracking on the large surface sensing with more than 90% accuracy for velocity estimation.

Performance analysis of coverage-centric heterogeneous cellular networks using dual-slope path loss model

Densifying the cellular networks has been largely considered as a promising solution in meeting the capacity demands of emerging cellular networks that have expeditiously transformed from voice-oriented to data-oriented. However, densifying the network infrastructure is like a double-edged sword; it on one hand helps in achieving the desired data rates but on the other hand, it degrades the network coverage. Owing to the disparity in transmit power of macro base stations (MBSs) and small BSs (SBSs), the SBSs located in the close proximity of MBSs have negligible coverage areas that not only overburden the macro tier but also cause excessive interference. In order to overcome these limitations, we propose to mute the SBSs that are located in the near-vicinity of MBSs to introduce a partial-correlation between the locations of the BS tiers. Meanwhile, to further enhance the coverage performance of these coverage-centric cellular networks, the traditional load balancing mechanism along with interference abating strategy is also employed in this paper. Nonetheless, it is also well-known in the literature that the usage of single-slope path loss model (PLM) leads to significant inaccuracies in evaluating the performance of dense cellular networks. Therefore, a more accurate PLM based on the dual-slope is adopted in this paper. Analytical expressions for the tier association and coverage probability are derived for a randomly chosen user using the tools from stochastic geometry and validated through simulations. The numerical results testify the improvement in network coverage due to the non-uniform deployment of SBSs and the joint consideration of load balancing and interference mitigation mechanisms.

Small Cell Planning: Resource Management and Interference Mitigation Mechanisms in LTE HetNets

In an attempt to address the huge data demand of indoor mobile users and poor signal strength from outdoor base stations to indoor environments, opertaors have started deploying variety of small cells likes Femtos, picos and micro cells. In this work, we used Femtos as small cells. Femto cells are low-cost, low-power consuming cellular base stations which operate only in licensed spectrum and are designed for both outdoor and indoor communication. Although small cells can be used for enhancing network capacity and coverage, arbitrary deployment of large number of small cells can lead to increase in operators expenditure and may create severe interference issues for cell edge users. In this paper, we look into optimal placement of small cell solutions to improve data rates of users in LTE HetNets using Femtos. Besides, these solutions address the main concerns of interference and resource management by proposing mechanisms for optimal placement of Femtos (OptFP, MinNF), dynamic power control and bandwidth allocation in Femtos (SOPC) and dynamic offloading. We provide a comparison of placement solutions and the applicability of each proposal keeping the operators’ revenue in mind.

UsICIC—A Proactive Small Cell Interference Mitigation Strategy for Improving Spectral Efficiency of LTE Networks in the Unlicensed Spectrum

The deployment of long term evolution (LTE) in the unlicensed spectrum (LTE-U) has been gaining significant industry momentum in recent months. The US 5-GHz Unlicensed National Information Infrastructure (UNII) bands that are currently under consideration for LTE deployment in the unlicensed spectrum contain only a limited number of 20 MHZ channels. Thus, in a dense multi-operator deployment scenario, one or more LTE-U small cells have to coexist and share the same 20 MHz unlicensed channel with each other and with the incumbent Wi-Fi. In this paper, we present the scenario and demonstrate that in the absence of an explicit interference mitigation mechanism, there will be a significant degradation in the overall LTE-U system performance for LTE-U cochannel coexistence in countries that do not mandate listen-before-talk (LBT) requirements. We then present the unlicensed spectrum intercell interference co-ordination (usICIC) mechanism as a time-domain multiplexing technique for interference mitigation for the sharing of an unlicensed channel by multioperator LTE-U small cells. Through extensive simulation results, we also demonstrate that our proposed usICIC mechanism will result in 40% or more improvement in overall LTE-U system performance.

Interference-Aware RZF Precoding for Multicell Downlink Systems

Recently, a structure of an optimal linear precoder for multi cell downlink systems has been described, and many other references have used simplified versions of this precoder to obtain promising performance gains. These gains have been hypothesized to stem from the additional degrees of freedom that allow for interference mitigation through interference relegation to orthogonal subspaces. However, no conclusive or rigorous understanding has yet been developed. In this paper, we build on an intuitive interference induction trade-off and the aforementioned preceding structure to propose an interference aware RZF (iaRZF) preceding scheme for multi cell downlink systems, and we analyze its rate performance. Special emphasis is placed on the induced interference mitigation mechanism of iaRZF. For example, we will verify the intuitive expectation that the precoder structure can either completely remove induced inter-cell or intra-cell interference. We state new results from large-scale random matrix theory that make it possible to give more intuitive and insightful explanations of the precoder behavior, also for cases involving imperfect channel state information (CSI). We remark especially that the interference-aware precoder makes use of all available information about interfering channels to improve performance. Even very poor CSI allows for significant sum-rate gains. Our obtained insights are then used to propose heuristic precoder parameters for arbitrary systems, whose effectiveness are shown in more involved system scenarios. Furthermore, calculation and implementation of these parameters does not require explicit inter base station cooperation.

Hybrid Relay Forwarding and Interference Mitigation Mechanisms in Cooperative Cognitive Ad-Hoc Networks

In this paper, a cooperative cognitive ad-hoc network is considered where a primary user and secondary users coexist with an interference user. A hybrid cooperation mechanism is proposed which allows secondary users to cooperate with primary user by forwarding the interference user’s data as well as conventionally forwarding the primary user’s data. The proposed scheme provides a more flexible approach that the secondary user can select the relay method according to channel state information. The primary user would release a reasonable portion of spectrum in return for data relay (so the primary user could improves throughput), while the secondary users could earn more spectrum access rights. When there is an interference user, secondary users could choose a method to help primary users by relay forwarding or interference mitigation depending on its own channel quality. With an aim of maximizing primary user’s rate and minimizing the secondary users’ energy consumption, a Stackelberg game framework is introduced in which a primary user is modeled as the leader and multiple secondary users are modeled as followers. The secondary users control their power to cooperate with the primary user to optimize game utilization. The existence and uniqueness of the proposed game’s equilibrium is proved and a distributed iterative algorithm is designed to reach the game equilibrium. Numerical results show that the proposed hybrid relay forwarding and interference mitigation mechanism outperforms the single cooperation scheme when an interference user exists.

Analysis on spatial reuse and interference in 60-GHz wireless networks

This paper evaluates the potential for spatial reuse and the degree of interference in a dense 60 GHz wireless networking environment. A 60 GHz simulation model is developed to evaluate the performance and extensive simulations are conducted by varying a number of parameters that affects the spatial reuse gain and interference. The results show that there is abundant spatial reuse to exploit in a dense 60 GHz wireless network. However, the results also indicate that there are considerable scenarios where interference is present, for which interference mitigation mechanisms are needed.

Multi-domain WLAN load balancing in WLAN/WPAN interference environments

The proliferation of wireless local area network (WLAN) deployments in enterprises, public areas, and homes will likely cause frequent geographical coverage overlap among multiple networks. A recent growing interest is the coordination among WLAN providers for efficient network management over a large coverage area. While radio resource management for a single WLAN has been studied extensively, little research work addresses resource management over multiple domains. When multiple WLANs co-locate in a small geographic vicinity, the lack of cooperative multi-domain resource management can cause significant performance degradation due to inter-domain interference. Unbalanced loads among multiple networks can incur congestion in a few WLANs while foregoing unused excess resources in others. Moreover, since WLANs often operate in unlicensed frequency bands shared by various public and private networks, they must cope with the dynamic RF environment involving a diverse set of interference sources. This paper introduces a new cooperative load balancing framework for multi-domain WLANs operating in an interference environment. A third-party-based architecture is proposed to facilitate fair radio resource allocation among multiple networks. The proposed third-party agent collects observed network state information from different WLANs and optimizes resource usage. Under the proposed scheme, resource utilization and co-channel interference can be adaptively balanced across the entire integrated system. The impact of other co-located interference sources in the operational environment are taken into account in the optimization process. The proposed load balancing framework for interference environments is a complement to the interference mitigation mechanisms operated at the PHY/MAC layer. Simulation results show that the proposed multi-domain load balancing scheme outperforms other schemes which do not consider interdomain interference or environmental interference.

Channel Clustering and Probabilistic Channel Visiting Techniques for WLAN Interference Mitigation in Bluetooth Devices

Since Bluetooth and wireless local area network (WLAN) technologies both operate at the 2.4-GHz industrial, scientific, and medical (ISM) band, the two types of devices may suffer from mutual interference and performance degradations. In this paper, we propose two new techniques, channel clustering and probabilistic channel visiting, to effectively improve the existing coexistence and interference mitigation mechanisms. The channel clustering technique employs statistical pattern recognition to classify the status of Bluetooth channels more accurately. The probabilistic channel visiting is used to more equitably allocate the channel resources between Bluetooth and WLAN devices. The effectiveness of these techniques is quantified by simulations. Results show that both techniques are beneficial in improving the performance of the existing mechanisms.