Inter-cell Interference Cancellation Research Articles

On-Demand Coordinated Spectrum and Resource Provisioning Under an Open C-RAN Architecture for Dense Small Cell Networks

Mobile networks have seen more than a thousand times traffic increases in the past decade. Network operators face an ever increasing demand and cost to deploy denser networks in order to maintain the quality of services. In view of this paradigm shift, an open cloud radio access network (C-RAN) service model is studied in this work. Integrating the cross-layer functions of spectrum resource sharing, channel and power allocation, and interference management in a C-RAN architecture, we explore the feasibility of providing a scalable yet efficient broadband wireless service with dense small cell networks (DSN). The proposed methods and architecture can be applied to DSN that support the functions of (further enhanced) inter-cell interference cancelation (feICIC/ICIC) techniques of 3GPP standard, and have the potential to provide a cost-effective solution for high-quality DSN. Simulation results across an area of 100 km <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{2}$</tex-math></inline-formula> show that the proposed scheme can offer an aggregate downlink throughput of 21 Gbps over a maximum channel bandwidth of 20 MHz, which is 5 times the throughput with a typical ICIC method. Moreover, the service satisfaction degree can reach 85% under the proposed C-RAN architecture, making it a promising and cost-effective solution for future broadband wireless services.

Selective interference alignment and neutralization in coordinated multipoint using multiuser MIMO

SummaryIn wireless communication, the concept of coordinated multipoint (CoMP) transmission is more attractive, and it transpired the notion based on interference management techniques. Interference alignment (IA) and interference neutralization (IN) methods can substantially align and neutralize the interference signals. The existing work in the CoMP transmission using multiuser multi‐input and multi‐output (MU‐MIMO) had long‐held problems such as specific limit of intercell (ICI) and cochannel interference (CCI) cancelation that contain low performance in cell‐edge users. The proposed framework of the transmission signal in selective interference alignment and neutralization (SIAN) CoMP MU‐MIMO system transmits multiple data streams in multipath by using downlink coordination between base stations and receiver side. This work contributes the individual perspectives to implement the IA and IN to align and cancel the interfered signals at the receiver side. Once the perspectives mentioned above are executed, zero‐forcing (ZF) and rechanneling filter are applied on the receiver side to eliminate residual ICI. In addition, spectral efficiency significantly improves the achievable data rate and enhances the performance of cell‐edge users and reduces the CCI at the receiver side. Furthermore, the antenna configuration signals are decoded to get the exact version of interference‐free signals with null path loss of signal transmission. The effectiveness of the proposed framework analyzes and verifies the numerical evaluation of the achievable degree of freedom. Finally, the simulation demonstrates the comparison of the proposed CoMP scheme with MIMO ZF and non‐CoMP schemes, which significantly improve the performance of spectral efficiency for cell‐edge users.

An Interference-Aware Resource-Allocation Scheme for Non-Cooperative Multi-Cell Environment

Inter-cell interference cancellation has been investigated for several decades and has become an elementary technique for modern wireless networks. However, the existing interference cancellation mechanism rarely considers the historical channel variations and interference characteristics. In this paper, we propose an interference-aware prediction-based resource-allocation strategy to deal with multi-cell interference, where the historical noisy channel state and the acknowledgment feedback are fully utilized. Together with the predicted interference patterns, our proposed joint sub-channel allocation and rate selection mechanism can achieve better average throughput performance. Through the numerical as well as the prototyping results, we show that our proposed scheme is able to provide more than 9.7% and 8% average throughput improvement compared with many existing baselines.

Bit error rate evaluation of relay-aided cooperative NOMA with energy harvesting under imperfect SIC and CSI

In this paper, we investigate a decode-and-forward relay-assisted cooperative non-orthogonal multiple access (NOMA) scheme, where the relay implements a time-switching (TS) based energy harvesting (EH). The impacts of the imperfect channel state information (CSI), inter-cell interference (ICI) and imperfect successive interference cancellation (SIC) are taken into account. We derive the end-to-end bit error rate (BER) expressions under imperfect CSI and ICI for both users. The effect of the EH parameters under the imperfect CSI on users’ BER performance is also examined. Furthermore, we discuss the impact of ICI on BER performance. Computer simulations are used for numerical analysis validation. The results reveal that the CSI deterioration reduces the SIC performance in each node despite the increase in EH parameters and causes an error floor at the higher signal-to-noise ratio (SNR). Furthermore, the BER performance of the users increases by increasing the EH parameters. Also, the ICI affects the SIC and degrades the BER of users.

Densely Deployed Indoor Massive MIMO Experiment: From Small Cells to Spectrum Sharing to Cooperation.

Massive MIMO is a key 5G technology that achieves high spectral efficiency and capacity by significantly increasing the number of antennas per cell. Furthermore, due to precoding, massive MIMO allows co-channel interference cancellation across cells. In this work, based on experimental channel data for an indoor scenario, we analyse the impact of inter and intra-cell interference suppression in terms of spectral efficiency, capacity, user fairness and computational cost for three simulated systems under different cooperation levels. The first scenario assumes a cooperative case where eight neighbouring cells share the spectrum and infrastructure. This scenario provides the highest system performance; however, user fairness is achieved only when there is inter and intra-cell interference suppression. The second scenario considers eight cells that only share the spectrum; with full intra-cell and inter-cell interference cancellation, it is possible to achieve 32% of the optimal capacity with 20% of the computational cost in each distributed CPU, although the total computational cost per system is the highest. The third scenario considers eight independent cells operating in different frequency bands; in this case, intra-cell interference suppression leads to higher spectral efficiency compared to the cooperative case without intra-cell interference suppression.

Imperfect CSI Muting With Time-Domain Thresholding for Cooperative Intercell Interference Cancellation

This article improves spectral efficiency performance of the cooperative intercell interference (ICI) cancellation by channel state information (CSI) muting with time-domain thresholding. In the original scheme, each transmitter superposes ICI replica signal to the original transmission signal so as to cancel them at the receiver side. Suppose uplink CSI estimation, its imperfection becomes significant since the transmission power of the user terminal is generally lower than that of the base station; ICI cancellation capability is limited. In order to overcome this problem, incorrect CSI needs to be properly muted. However, the qualification of CSI around the noise level is a challenging issue. A key proposal is to focus on the time-domain impulse response wherein the channel power is concentrated to the specified part in the observation range. It can accurately differentiate useful CSI even in the noise-limited region; generation of erroneous ICI replica signals is prevented and remaining transmission power can be re-allocated to the desired signal. Therefore, the ICI cancellation capability can be fully provided to maximize overall spectral efficiency. Simulative evaluation validates its possibility and effectiveness; average spectral efficiency can be improved by up to 11.9% compared to the original approach using full CSI.

Mission-critical user priority-based cooperative resource allocation schemes for multi-layer next-generation public safety networks

The Republic of Korea became the first country in the world to have next-generation long term evolution (LTE) public safety networks, and South Korea’s evolution in critical communications has taken the lead as well. However, the same 700 MHz frequency band is allocated to the LTE-based public safety (PS-LTE) network, the LTE-based high-speed railway (LTE-R) network, and the LTE-maritime (LTE-M) network, and hence, extensive interest and practical research into co-channel interference management schemes are immediately required. This paper focuses on multi-layer next-generation public safety networks and employs efficient mission-critical user priority-based resource allocation schemes to resolve major challenges, such as co-channel interference, mission-critical user requirements, quality of service (QoS) prioritization, etc. We utilize coordinated scheduling (CS), coordinated multipoint (CoMP), and intercell interference cancellation (ICIC) under the radio access network (RAN)-sharing environment to analyze the overlapping next-generation PS-LTE, LTE-R, and LTE-M networks. CS CoMP is implemented between the three LTE public safety networks to boost cell-edge-user performance by muting the neighboring interfering base stations. This accomplishes a tremendous enhancement in system throughput for coexisting next-generation public safety networks. By employing ICIC with CS CoMP under the RAN-sharing environment, the best interference and outage performance can be attained for coexisting PS-LTE, LTE-R, and LTE-M networks.

Mutual Successive Interference Cancellation Strategies in NOMA for Enhancing the Spectral Efficiency of CoMP Systems

The densification of mobile networks should enable the fifth generation (5G) mobile networks to cope with the ever increasing demand for higher rate traffic, reduced latency, and improved reliability. The large scale deployment of small cells and distributed antenna systems in heterogeneous environments will require more elaborate interference mitigating techniques to increase spectral efficiency and to help unlock the expected performance leaps from the new network topologies. Coordinated multi-point (CoMP) is the most advanced framework for interference management enabling the cooperation between base stations to mitigate inter-cell interference and boost cell-edge user performance. In this paper, we study the combination of CoMP with mutual SIC, an interference cancellation technique based on power-domain non-orthogonal multiple access (NOMA) that enables multiplexed users to simultaneously cancel their corresponding interfering signals. A highly efficient inter-cell interference cancellation scheme is then devised, that can encompass several deployment configurations and coordination techniques. The obtained results prove the superiority of this approach compared to conventional NOMA-CoMP systems.

Iterative Inter-Cell Interference Cancellation Receiver for LDPC-Coded MIMO Systems

In an ultra-dense cellular system, users at the cell-edge are susceptible to inter-cell interference (ICI) because of the overlap of the spectrum. To combat ICI, this paper investigates two iterative ICI cancellation approaches for low-density parity-check-coded multiple-input multiple-output systems. One approach includes separate signal and interference detectors; the other one employs a joint detector for both the desired signal and interference. The joint-detector approach achieves a comparable error-rate performance with only half the computational complexity when compared to the separate-detector counterpart. An iterative ICI cancellation receiver using the joint detector is proposed and implemented. Its hardware efficiency is significantly enhanced by leveraging an efficient coordinate rotation digital computer based processing array, an adaptive input-range scaling scheme, and an area-efficient log-likelihood ratio calculator. The iterative ICI cancellation receiver is flexible enough to support multiple modulations of up to 256-QAM. The maximum gross throughput is 1.24 Gb/s for a 4×4 256-QAM configuration in a 40-nm CMOS technology. The proposed iterative receiver outperforms the current state-of-the-art works in both the throughput-to-area ratio and the normalized energy metrics, despite the added ICI capability.

Experimental performance evaluations of CoMP and CA in centralized radio access networks

According to International Mobile Telecommunication’s requirements for 2020, next generation cellular networks such as 5G need to meet certain Key Performance Indicator targets. Centralized-Radio Access Networks (C-RAN) is a novel technique that can address growing capacity needs of Mobile Network Operators (MNOs) due to ever increasing demands of their users. In order to meet stringent requirements of next generation cellular networks, C-RAN enabled techniques have attracted a lot attention due to their efficient spectrum (band, bandwidth) utilization [e.g. via carrier aggregation (CA)], spectrum efficiency (e.g. via Inter-Cell Interference Co-ordination and cancellation using Coordinated MultiPoint (CoMP) Transmission/Reception). In this paper, we investigate three different CA scenarios along with their benefits and limitations from the perspective of MNO. Additionally, we analyze inter-Baseband Unit (BBU) uplink (UL) CoMP feature as a real-world experimental C-RAN implementation in an operational suburban site of Istanbul in Turkey. Quantitative CA performance measurements demonstrate performance comparison of the considered three CA scenarios, and depending on each MNO’s strategy, different CA gains are observed (e.g. LTE 1800 Mhz MNOs can benefit more from L800 umbrella coverage scenario). Our coordinated inter-BBU UL CoMP results indicate that around $$7\%$$, $$9\%$$ and $$6\%$$ gains can be achieved in UL cell, user and cell-edge user throughput respectively.

Cooperative Spatial Modulation for Cellular Networks

Spatial modulation (SM) is a unique single-stream, multiple-input multiple-output (MIMO) transmission technique. One key property of the SM is that a single transmit antenna is activated at any given time, which completely avoids inter-channel interference in a single-user scenario. In the context of multi-user cellular networks, inter-cell interference (ICI) mitigation becomes the main challenge for the SM. Network MIMO is a technique that employs precoding to enable ICI cancellation among neighbouring cells. However, the cell-edge users might still experience a high level of the ICI due to the significant channel attenuation. In this paper, we propose a novel cooperative scheme based on the SM, named cooperative SM (CoSM). The basic concept is to reschedule the transmit antennas of multiple base stations for multiple co-channel users, so as to maximize the antenna diversity gain. Unlike the traditional antenna selection for a single user, the involvement of multiple users might cause conflict due to the selection of the same antenna. An antenna rescheduling scheme (ARS) is thus proposed to address this issue. The performance of the ARS is theoretically analyzed, and closed-form expressions are derived for the probability distribution of the received SNR. Also, a novel three-tier cellular architecture is proposed to accommodate the CoSM within the context of the network MIMO. Results show that the CoSM can improve signal-to-interference-plus-noise ratio by up to 4 dB over the network MIMO. In addition, compared with spatial multiplexing using the same ARS, the CoSM can halve the energy consumption while achieving the same bit error rate.

Improved hybrid inter and intra-cell interference cancellation mechanism for LTE-A HETNETS

In Heterogeneous networks (HetNets), operators need to ensure reliable service to their users in terms of network performance and low cost. The growing demand of user traffic necessitates the incorporation of femto cells and pico cells for facilitating seamless services. The network performance of Long Term Evolution (LTE) and LTE Advanced (LTE-A) HetNets is drastically influenced by the degree of interference that is realized in the inter-cell and intra-cell during communication. In this paper, an Improved Hybrid inter and intra-cell interference cancellation mechanism (CRS-IIC-LFLS) is propounded for handling interference at the inter and intra-cell level. Inter-cell interference cancellation is achieved through the use of an Improved CRS-IIC algorithm that uses the benefits of Linear Filtering Least Square (LFLS) method for channel estimation. CRS-IIC-LFLS is found to potent in rapid interference cancellation facilitation by suppressing the noise level, reducing the impact of fading channel and inherently eliminates small energy aware paths from large energy aware paths. The Simulation results confirm that the proposed scheme ensures better network throughput under light load, medium load and heavy load conditions of the network. The results prove that the performance of CRS-IIC-LFLS with CRS-IC-LFLS and CRS-IC-LLS based on spectral efficiency is improved at a mean rate of 21% and 26% respectively. The simulation results also portrays that the increase in the spectral efficiency of CRS-IIC-LFLS (64-QAM) is phenomenal to a maximum improvement of 12% over CRS-IIC-LFLS (16-QAM).

Interference management based on power control and MU-MIMO

Improvement of spectrum efficiency is a valuable research topic in mobile communication system, which impact cell edge user experience especially. According to current research results, three methods to improve inter-cell spectrum efficiency base on inter-cell interference management, including inter-cell interference randomization, inter-cell interference cancellation and inter-cell interference co-ordination. In this paper, one combinatorial method based on uplink power control and SINR prediction with non-ideal MU-MIMO CSI feedback is proposed for optimal management of inter-cell interference co-ordination. The simulation results show that this method performs very well in complex inter-cell interference scenario, and the average spectrum efficiency is improved more than 50%.

Iterative Intercell Interference Cancellation in MIMO Multicell Networks

An iterative intercell interference cancellation algorithm is introduced to improve the receiver performance of uplink transmission in multicell networks. At first, the uplink signal detection is performed independently in each cell according to minimum mean squared error (MMSE) criterion. Subsequently, the detection results are applied to reconstruct the transmit signals of different users and cancel their interference to neighboring cells. With the help of reconstruction results, the MMSE detection matrix of each cell is updated. The channel responses of both efficient and interference links are estimated with the help of pilots. The pilot allocation parameter is introduced to indicate the quality of channel estimation. The simulation results indicate that intercell interference can be greatly mitigated by the proposed algorithm with a moderate number of receiver antennas at the base station.

Novel Beamforming and User Scheduling Algorithm for Inter-cell Interference Cancellation

Coordinated multi-point transmission is a candidate technique for next-generation cellular communications systems. We consider a system with multiple cells in which base stations coordinate with each other by sharing user channel state information, which mitigates inter-cell interference (ICI), especially for users located at the cell edge. We introduce a new u

Efficient resource allocation for passive optical fronthaul-based coordinated multipoint transmission

The centralized processing in cloud radio access network enables cooperation between baseband processing units (BBUs) like inter-cell interference (ICI) cancellation on the basis of coordinated multipoint (CoMP). Large amounts of the sharing data will be transmitted through fronthaul transport network. In the paper, both integer non-linear programming (INLP) optimization model and adaptive genetic algorithm (GA) are explored to release the capacity pressure of the fronthaul transport network when CoMP is introduced. We also consider the resource allocation problem of the passive optical fronthaul network. The proposed algorithm tries to reduce the downlink bandwidth and improve the optical resource allocation efficiency of the optical fronthaul with minimal influence on the fronthaul topology. During the simulations, three critical factors are considered: (1) the number of cell edge users, (2) the average traffic demand of cell edge users, (3) the size of cell cluster used to enable the CoMP. The simulation results show that the most efficient bandwidth saving and optical resource allocation can be achieved with INLP, while the proposed adaptive GA nearly has the same performance with low computational complexity and fast convergence, which is more applicable for the large-scale fronthaul network. Furthermore, the load difference of the fronthaul transport network can be further reduced.

Downlink performance of cell edge using cooperative BS for multicell cellular network

We consider the downlink of a multicell system comprised of base stations (BSs) and user terminals equipped with multiple antennas respectively on the condition that arbitrary BS cooperation and distance dependent propagation path loss are assumed. In this paper, we consider homogeneous networks for the rectangular coordinates and show the cell edge performance of cellular networks based on distance from their cell center, i.e., BS. We focus on the downlink capacity of edge users in the cellular networks and show that BS cooperation can improve the spectral efficiency. The BSs cooperate for their transmission to the cell edge users in order to improve their signal-to-interference-plus-noise ratio (SINR) for inter-cell interference (ICI) cancelation in downlink multicell systems. When fractional frequency reuse (FFR) is applied to the cell edge, it is conjectured that BS cooperation, or a coordinated multipoint (CoMP), will further improve the system performance. Simulation results show that the proposed scheme outperforms the reference schemes in terms of the cell edge SINR with a minimal impact on the path loss exponent in the networks.

Full Duplex-Assisted Intercell Interference Cancellation in Heterogeneous Networks

This paper studies the suppression of cross-tier intercell interference (ICI) generated by a macro base station (MBS) to pico user equipments (PUEs) in heterogeneous networks (HetNets). Different from existing ICI avoidance schemes such as enhanced ICI cancellation (eICIC) and coordinated beamforming, which generally operate at the MBS, we propose a full duplex (FD)-assisted ICI cancellation (fICIC) scheme, which can operate at each pico BS (PBS) individually and is transparent to the MBS. The basic idea of the fICIC is to apply FD technique at the PBS such that the PBS can send the desired signals and forward the listened cross-tier ICI simultaneously to PUEs. We first consider the narrowband single-user case, where the MBS serves a single macro UE and each PBS serves a single PUE. We obtain the closed-form solution of the optimal fICIC scheme, and analyze its asymptotical performance in ICI-dominated scenario. We then investigate the general narrowband multiuser case, where both MBS and PBSs serve multiple UEs. We devise a low-complexity algorithm to optimize the fICIC aimed at maximizing the downlink sum rate of the PUEs subject to user fairness constraint. Finally, the generalization of the fICIC to wideband systems is investigated. Simulations validate the analytical results and demonstrate the advantages of the fICIC on mitigating cross-tier ICI.

Spatial Reuse Precoding for Scalable Downlink Networks

In this paper, we develop linear precoding schemes for MIMO downlink networks with quasi-static channels that are scalable, in the sense that they can be implemented with moderate complexity in networks with increasing numbers of cells and users. The principle that underlies the proposed precoding scheme is to exploit the decomposable structure of the equivalent channel matrix by designing the precoders at the base stations to be decomposable as well. Thus, the channel matrices and the designed precoders can be expressed as the Kronecker product of constituent matrices. For networks with a finite number of cells, the proposed structured precoding schemes enable inter-cell interference cancellation without the need for inter-cell feedback and provide more degrees of freedom than conventional interference avoidance schemes, while incurring a latency that grows only linearly in the number of cells. The proposed structured precoding schemes also enable a scaling approach for unbounded networks that we have called “spatial reuse precoding” (SRP). SRP is based on the observation that at each receiver, the signals from interfering sources that employ the same precoder arrive in the same subspace, regardless of the particular channel matrices between the interfering sources and the receiver. In some typical cellular architectures we show how an SRP scheme based on the proposed structured precoders can be designed to eliminate the dominant sources of interference without requiring cooperation between cells. In addition, we show that SRP can provide substantial performance gains in certain heterogeneous networks.

다중 셀 MIMO 하향채널의 셀 에지 SINR

In this paper, we consider 19 cells with the two tiers for polar-rectangular coordinates (PRCs) and provide the cell edge performance of cellular networks based on distance from cell center i.e., BS (base station). When FFR is applied(or adopted) to cell edge, it is expected that BS cooperation, or a coordinated multipoint (CoMP) multiple access strategy will further improve the system performance. We proposed a new method to evaluate the sum rate capacity of the MIMO DC of multicell system. We improve the performance of cell edge users for intercell interference cancelation in cooperative downlink multicell systems. Simulation results show that the proposed scheme outperforms the reference schemes, in terms of cell edge SINR (signal-to-interference-noise ratio) with a minimal impact on the network path loss exponent. We show 13 dB improvements in cell-edge SINR by using reuse of three relative to reuse of one. BS cooperation has been proposed to mitigate the cell edge effect.