Quasi‐distributed Interference Coordination for HSPA HetNet

The heterogeneous network (HetNet) has been discussed in detail in the Long‐Term Evolution (LTE) and LTE Advanced standards. However, the standardization of High‐Speed Packet Access HetNet (HSPA HetNet) launched by 3GPP is pushing at full steam. Interference coordination (IC), which is responsible for dealing with the interference in the system, remains a subject worthy of investigation in regard to HSPA HetNet. In this paper, considering the network framework of HSPA HetNet, we propose a quasi‐distributed IC (QDIC) scheme to lower the interference level in the co‐channel HSPA HetNet. Our QDIC scheme is constructed as slightly different energy‐efficient non‐cooperative games in the downlink (DL) and uplink (UL) scenarios, respectively. The existence and uniqueness of the equilibrium for these games are first revealed. Then, we derive the closed‐form best responses of these games. A feasible implementation is finally developed to achieve our QDIC scheme in the practical DL and UL. Simulation results show the notable benefits of our scheme, which can indeed control the interference level and enhance the system performance.     

Maximized achievable rate of SINR‐measurement‐based spectrum sharing with binary feedback

Motivated by the difficulty in measuring channel state information between heterogeneous primary and secondary systems, we propose a signal‐to‐interference‐noise ratio (SINR)‐based spectrum sharing policy. In the proposed spectrum sharing policy, a secondary user who does not cause SINR outage at the primary receiver is admitted to share the primary user's spectrum. In this article, we analyze the achievable rate of a secondary user and for whom the achievable rate is maximized in the SINR‐constrained spectrum sharing. The maximized achievable rate is determined by the ratio of the distance between the secondary transmitter and the primary receiver to the distance between the secondary transmitter and receiver, and it is proportional to the distance ratio. In conclusion, secondary links with large distance ratio can support high data rate applications so long as SINR constraint of the primary user is guaranteed. Copyright © 2011 John Wiley & Sons, Ltd.     

On the performance of interference cancelation in D2D‐enabled cellular networks

Device‐to‐device (D2D) communication underlaying cellular networks is a promising technology to improve network resource utilization. In D2D‐enabled cellular networks, interference among spectrum‐sharing links is severer than that in traditional cellular networks, which motivates the adoption of interference cancelation (IC) techniques at the receivers. However, to date, how IC can affect the performance of D2D‐enabled cellular networks is still unknown. In this paper, we present an analytical framework for studying the performance of two IC methods, that is, unconditional IC and successive IC, in large‐scale D2D‐enabled cellular networks using the tools from stochastic geometry. To facilitate the interference analysis, we propose an approach of stochastic equivalence of the interference, which converts the two‐tier interference (interference from the cellular tier and D2D tier) to an equivalent single‐tier interference. Based on the proposed stochastic equivalence models, we derive the general expressions for the successful transmission probabilities of both cellular uplinks and D2D links in the networks where unconditional IC and successive IC are respectively applied. We demonstrate how these IC methods affect the network performance using both analytical and numerical results. Copyright © 2016 John Wiley & Sons, Ltd.     

Energy‐efficient cluster division for multi‐cell joint transmission technology

Coordinated Multi‐Point (CoMP) is an effective way to improve user performance in next‐generation wireless cellular networks, such as 3GPP LTE‐Advanced(LTE‐A). The base station cooperation can reduce interference, and increase the signal to interference and noise ratio (SINR) of cell‐edge users and improve the system capacity. However, the base station cooperation also adds additional power consumption for signal processing and sharing information through back‐haul links between cooperative base stations. As such, CoMP may potentially consume more energy. This paper studies such energy consumption issue in CoMP, presents a semi‐dynamic CoMP cluster division algorithm based on energy efficiency (SCCD‐EE) that can effectively adapt to users' real‐time interference, and employs the idea of Maximal Independent Set (MIS) to solve the problem of cluster overlapping. To verify the feasibility of the proposed algorithm, this paper performs comprehensive evaluations in terms of energy efficiency and system capacity. The simulation results show that the proposed semi‐dynamic cluster division algorithm can not only improve the system capacity and the quality of service (QoS) of cell‐edge users, but also achieve higher network energy efficiency compared with static cluster methods and Non‐CoMP approaches. Copyright © 2016 John Wiley & Sons, Ltd.     

全双工大规模MIMO异构网络频谱效率分析及优化

本文研究全双工大规模多输入多输出（multiple-input-multiple-output, MIMO）异构网络。推导了采用迫零（zero-forcing, ZF）预编码/检测方案的上下行渐近信干噪比（signal-to-interference-plus-noise ratio, SINR）的闭合表达式。根据理论分析,提出了基于几何规划（geometric programming, GP）的功率控制方案和基于部分用户选择（partial users selection, PUS）的跨层干扰消除方案,改善系统频谱效率。仿真结果表明,与传统方案相比本文提出的功率控制方案和跨层干扰消除方案能够显著提升异构网络的频谱效率。      

Joint interference coordination approach in femtocell networks for QoS performance optimization

Future heterogeneous networks with dense cell deployment may cause high intercell interference. A number of interference coordination (IC) approaches have been proposed to reduce intercell interference. For dense small‐cell deployment with high intercell interference between cells, traditional forward link IC approaches intended to improve edge user throughput for best effort traffic (ie, file transfer protocol download), may not necessarily improve quality of service performance for delay‐sensitive traffic such as voice over long‐term evolution traffic. This study proposes a dynamic, centralized joint IC approach to improve forward link performance for delay‐sensitive traffic on densely deployed enterprise‐wide long‐term evolution femtocell networks. This approach uses a 2‐level scheme: central and femtocell. At the central level, the algorithm aims to maximize network utility (the utility‐based approach) and minimize network outage (the graphic‐based approach) by partitioning the network into clusters and conducting an exhaustive search for optimized resource allocation solutions among femtocells (femto access points) within each cluster. At the femtocell level, in contrast, the algorithm uses existing static approaches, such as conventional frequency reuse (ReUse3) or soft frequency reuse (SFR) to further improve user equipment quality of service performance. This combined approach uses utility‐ and graphic‐based SFR and ReUse3 (USFR/GSFR and UReUse3/GReUse3, respectively). The cell and edge user throughput of best effort traffic and the packet loss rate of voice over long‐term evolution traffic have been characterized and compared using both the proposed and traditional IC approaches.     

Hybrid channel gain prioritized access‐aware cell association with interference mitigation in LTE‐Advanced HetNets

LTE‐Advanced heterogeneous networks deployment is meant to address the increasing demand for quality of service, high data rates and coverage extension. Load balancing is among the primary challenges, especially when the user equipments (UEs) associate with diverse transmission power network tiers using received signal strength. The low‐power network tier's spectrum will be underutilized, and UEs associated with them will be inflicted by interference from the high‐power network tier. The proposed hybrid channel gain prioritized access (HCGPA)‐aware cell association scheme stresses the importance of combined metrics with interference mitigation to simultaneously achieve load balancing and enhance performance among the network tiers. The high‐priority UEs associate with the tier that gives the maximum channel gain being higher than a given threshold. While the low‐priority UEs association is based on the maximum joint metrics (channel gain, channel access probabilities of low‐priority UEs and high‐priority UEs). The HCGPA scheme has 1.72 times the number of UEs connected to low‐power networks, 8% better load balancing fairness, compared with the conventional reference signal receive power and RSRP + 6 dB bias cell associations. Although the susceptibility of HCGPA to interference led to the poor signal to interference to noise ratio (SINR) performance of the cell‐edge UEs, the cell‐centre UEs exhibited the best spectral efficiency performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Coverage analysis of cell‐edge users in heterogeneous wireless networks using Stienen's model and RFA scheme

In heterogeneous wireless networks, signal‐to‐interference‐plus‐noise ratio (SINR) suffers degradation due to strong interference received by users from offloaded macro base station (mBS). Similarly, cell‐edge users experience low SINR due to their distant locations. Moreover, small base stations (sBSs) located in the vicinity of mBS experience reduced coverage due to the high transmit power of mBS. To overcome these limitations, we use Stienen's model as a base station deployment strategy to improve network performance gain. More specifically, we use reverse frequency allocation (RFA) as an interference management scheme together with Stienen's model to significantly improve SINR, enhance edge user coverage, and avoid sBS deployment near the mBS. In the proposed set‐up, the available coverage region is divided into two noncontiguous regions, ie, center region and outer region. Furthermore, mBSs are uniformly distributed throughout the coverage region using independent Poisson point processes, while sBSs are deployed only in outer region using Poisson hole process (PHP). Closed‐form expressions for coverage probabilities are characterized for the proposed model. Numerical results show that the proposed scheme yields improved SINR with enhanced edge user coverage and requires fewer number of sBSs.     

Reduction of Outage Probability due to Handover by Mitigating Inter‐cell Interference in Long‐Term Evolution Networks

The burgeoning growth of real‐time applications, such as interactive video and VoIP, places a heavy demand for a high data rate and guarantee of QoS from a network. This is being addressed by fourth generation networks such as Long‐Term Evolution (LTE). But, the mobility of user equipment that needs to be handed over to a new evolved node base‐station (eNB) while maintaining connectivity with high data rates poses a significant challenge that needs to be addressed. Handover (HO) normally takes place at cell borders, which normally suffers high interference. This inter‐cell interference (ICI) can affect HO procedures, as well as reduce throughput. In this paper, soft frequency reuse (SFR) and multiple preparations (MP), so‐called SFRAMP, are proposed to provide a seamless and fast handover with high throughput by keeping the ICI low. Simulation results using LTE‐Sim show that the outage probability and delay are reduced by 24.4% and 11.9%, respectively, over the hard handover method — quite a significant result.     

Joint admission control,cell association,power allocation and throughput maximization in decoupled 5G heterogeneous networks

Downlink (DL)-uplink (UL) coupled cell association scheme was adopted in 3rd generation (3G) homogeneous network and 4th generation (4G) heterogeneous network (HetNet). In the coupled cell association scheme, a user is associated to single base station (BS) in DL & UL based on the strongest received signal power (SRSP) in DL from a macro base station (MBS) and multiple small base stations (SBS) in HetNet. This is a sub-optimal solution for cell association as most of the users are associated to a MBS due to dominant transmit power and brings challenges like multiple interference issues and imbalanced user traffic load which leads to a degraded throughput in HetNet. In this paper, we investigate downlink uplink decoupled cell association scheme to address these issues and formulate a sum-rate maximization problem in terms of admission control, cell association and power allocation for MBS only, coupled and decoupled HetNet. The formulated optimization problem falls into class of a mixed integer non linear programming (MINLP) problem which is NP-hard and requires exhaustive search to find the optimal solution. However, computational complexity of the exhaustive search increases exponentially with the increase in number of users. Therefore, an outer approximation algorithm (OAA) is proposed as a solution to find near optimal solution with less computation complexity. Extensive simulations work has been done to evaluate the decoupled cell association scheme in HetNet vs the coupled cell association scheme in traditional MBS only and HetNet. Results show the effectiveness of decoupled cell association scheme in terms of KPIs, such as throughput, addressing user traffic load imbalances and number of users attached.

     

A universal frequency reuse scheme in LTE‐A heterogeneous networks

Effective inter‐cell interference mitigation has been extensively studied because of its outstanding cell‐edge signal quality improvement capability. Conventional static inter‐cell interference coordination strategies, including fractional frequency reuse and soft frequency reuse, have received much attention owing to their effectiveness in mitigating interference and low complexity in implementation. However, they are less effective when dealing with dense uneven traffic distributions and dynamic traffic demands and thus incur low spectrum utilization in some cells and spectrum shortage in others. This paper proposes a universal frequency reuse scheme in a two‐layer Long Term Evolution‐Advanced heterogeneous network to ensure good throughput for all user equipment (UE), especially UEs at cell edge. The proposed scheme allows each cell to use all the spectrum resources, limited by an orderly regulation of all sub‐bands. This scheme minimizes the potential occurrence probability of inter‐cell co‐sub‐band interference through an intra‐cell sub‐band resource management. Furthermore, a graph‐theoretic based sub‐band allocation algorithm is developed to optimize UE throughput performance, especially for the cell‐edge low signal to interference noise ratio UEs. A comprehensive performance comparison among different frequency reuse schemes is conducted by considering performance metrics, including cell‐edge throughput, average throughput, and signal to interference noise ratio cumulative distribution function. Simulation result shows that the universal frequency reuse scheme outperforms other two schemes significantly. Copyright © 2016 John Wiley & Sons, Ltd.     

基于规划的TD-LTE时频联合干扰协调技术研究

本文基于无线通信网络工程中的规划技术,针对TD-LTE系统传输基本单元资源块,将规划技术与资源块相融合,提出基于规划的TD-LTE时频联合干扰协调技术,突破了单纯从频率或时间维度上对资源规划的限制,同时结合用户调度、功率控制等辅助技术以提高干扰抑制性能.文中给出了基于3GPP标准仿真平台的性能对比,最后讨论并分析了该方...     

Low‐complexity inter‐carrier interference cancelation scheme for SC‐IFDMA system

After the standardization of SCFDMA as the uplink transmission scheme for LTE, frequency synchronization and resulting interference cancelation received considerable attention. In this paper, mathematical modeling of uplink SCFDMA system with interleaved subcarrier assignment scheme (SC‐IFDMA) is carried out in the presence of carrier frequency offset, and the results were utilized in framing the concept of effective interference matrix, which efficiently represents the interference cancelation problem. We propose two schemes to mitigate the effects of interference and channel based on linear filtering approach, and the typical structure of effective interference and channel matrices in SC‐IFDMA were utilized in formulating a low‐complexity implementation model for the proposed compensation schemes. Even though many works have been reported in the field of interference cancelation of SCFDMA system, majority of them were extension of the interference compensation schemes proposed for OFDMA system, whereas schemes proposed in this paper utilize the typical characteristics of the SC‐IFDMA system. The proposed schemes were simulated using MATLAB, and the performance is compared with existing schemes. Copyright © 2015 John Wiley & Sons, Ltd.     

Leveraging multiuser diversity for adaptive hybrid satellite‐LTE downlink scheduler (H‐MUDoS) in emerging 5G‐satellite network

In order to achieve ubiquitous coverage and service continuity in future 5G network, satellite‐based access is the best solution to complement the terrestrial LTE‐A. In light of this, we introduce a channel‐aware hybrid scheduling technique on the basis of satellite‐LTE spectrum sharing. According to the user‐experienced channel, base stations (eNodeB) and the satellite will work cooperatively. The eNodeB mainly provides service in urban area for high density population. Meanwhile, the satellite will perform either offloading, providing service for under‐served users, or extra coverage for users in rural and remote areas having no coverage of eNodeB. Leveraging the multiuser diversity, we implement a new metrics computation method for hybrid satellite‐LTE downlink scheduler (H‐MUDoS). Compared with other existing schedulers, simulation results clearly demonstrate the high performance of H‐MUDoS in terms of spectral efficiency in addition to improvement of the quality‐of‐service requirements and capacity maximization.     

A novel MAC protocol for IDMA‐based multi‐beam satellite communication systems

Considering the limitations of satellite communication systems and advantages of new emerging interleave‐division multiple access (IDMA) technology, IDMA is introduced into the satellite systems, providing a new solution for multiple access techniques of satellite systems. To further validate the IDMA into satellite systems, a novel medium access control (MAC) scheme is proposed. In the random access channel, the interleave‐division slotted ALOHA method is adopted to alleviate the collision of access requests. Furthermore, a novel minimum power allocation scheme based on signal‐to‐interference‐plus‐noise ratio (SINR) evolution is proposed to maximize the capacity of such an interference‐sensitive system. By virtue of SINR evolution, our proposed scheme can accurately estimate multi‐user detection efficiency with low computational cost and further reduce the transmitted power, illustrating the high power efficiency of IDMA. To further enhance the performance of the MAC protocol, an effective call admission control scheme considering the effect of power control error is designed and combined into our MAC protocol. Analysis and simulation results show that, by taking full advantage of the chip‐by‐chip multi‐user detection technique, the proposed IDMA MAC protocol achieves high throughput and low average packet delay simultaneously, with low onboard processing complexity in the multi‐beam satellite communication systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Anomaly‐based intrusion detection of jamming attacks,local versus collaborative detection

We present intrusion detection algorithms to detect physical layer jamming attacks in wireless networks. We compare the performance of local algorithms on the basis of the signal‐to‐interference‐plus‐noise ratio (SINR) executing independently at several monitors, with a collaborative detection algorithm that fuses the outputs provided by these algorithms. The local algorithms fall into two categories: simple threshold that raise an alarm if the output of the SINR‐based metrics we consider deviates from a predefined detection threshold and cumulative sum (cusum) algorithms that raise an alarm if the aggregated output exceeds the predefined threshold. For collaborative detection, we use the Dempster–Shafer theory of evidence algorithm. We collect SINR traces from a real IEEE 802.11 network, and with the use of a new evaluation method, we evaluate both the local and the Dempster–Shafer algorithms in terms of the detection probability, false alarm rate, and their robustness to different detection threshold values, under different attack intensities. The evaluation shows that the cusums achieve higher performance than the simple threshold algorithms under all attack intensities. The Dempster–Shafer algorithm when combined with the simple algorithms, it can increase their performance by more than 80%, but for the cusum algorithms it does not substantially improve their already high performance.Copyright © 2013 John Wiley & Sons, Ltd.     

Design of near‐optimal local likelihood search‐based detection algorithm for coded large‐scale MU‐MIMO system

Massive multiuser multiple input multiple output (MU‐MIMO) system is aimed to improve throughput and spectral efficiency through a large number of antennas incorporated at the transmitter and/or receiver. However, the MU‐MIMO system usually suffers from interantenna interference (IAI) and multiuser interference (MUI). The IAI imposes due to closely spaced antennas at each user equipment (UE), and MUI is enforced when one user comes under the vicinity of another user in the same cellular network. Most of the previous literatures considered any one of these interferences. However, the present work proposes singular value decomposition (SVD) precoding‐assisted user‐level local likelihood ascent search (LLAS) algorithm to mitigate both IAI and MUI. In the uplink MU‐MIMO, the IAI is cancelled by SVD, and the residual MUI is mitigated by LLAS detection. The LLAS detection balances the trade‐off between the classical suboptimal likelihood ascent search (LAS) and optimal maximum likelihood (ML) detection techniques. The proposed LLAS performs local search among all 2M_T‐dimensional neighborhood vectors at each UE, where M_T represents number of transmitting antennas of each UE. Thus, its performance is near optimal, and its complexity is much lower than ML detector.     

A self‐organized resource allocation scheme for heterogeneous macro‐femto networks

This paper investigates the radio resource management (RRM) issues in a heterogeneous macro‐femto network. The objective of femto deployment is to improve coverage, capacity, and experienced quality of service of indoor users. The location and density of user‐deployed femtos is not known a‐priori. This makes interference management crucial. In particular, with co‐channel allocation (to improve resource utilization efficiency), RRM becomes involved because of both cross‐layer and co‐layer interference. In this paper, we review the resource allocation strategies available in the literature for heterogeneous macro‐femto network. Then, we propose a self‐organized resource allocation (SO‐RA) scheme for an orthogonal frequency division multiple access based macro‐femto network to mitigate co‐layer interference in the downlink transmission. We compare its performance with the existing schemes like Reuse‐1, adaptive frequency reuse (AFR), and AFR with power control (one of our proposed modification to AFR approach) in terms of 10 percentile user throughput and fairness to femto users. The performance of AFR with power control scheme matches closely with Reuse‐1, while the SO‐RA scheme achieves improved throughput and fairness performance. SO‐RA scheme ensures minimum throughput guarantee to all femto users and exhibits better performance than the existing state‐of‐the‐art resource allocation schemes.Copyright © 2014 John Wiley & Sons, Ltd.     

Cross‐layer scheduling for multi‐users in cognitive multi‐radio mesh networks

A wireless mesh network has been popularly researched as a wireless backbone for Internet access. However, the deployment of wireless mesh networks in unlicensed bands of urban areas is challenging because of interference from external users such as residential access points. We have proposed Urban‐X, which is a first attempt towards multi‐radio cognitive mesh networks in industrial, scientific, and medical bands. Urban‐X first controls network topology with a distributed channel assignment to avoid interference in large timescale. In such a topology, we develop a new link‐layer transmission‐scheduling algorithm together with source rate control as a small‐timescale approach, which exploits receiver diversity when receivers of multi‐flows can have different channel conditions because of varying interference. For this purpose, mesh nodes probe the channel condition of received mesh nodes using group Request to Send and group Clear to Send. In this study, we establish a mathematical Urban‐X model in a cross‐layer architecture, adopting a well‐known network utility maximization framework. We demonstrate the feasibility of our idea using a simulation on the model. Simulation results show improved network throughput from exploiting receiver diversity and distributed channel assignment under varying external user interference. Copyright © 2012 John Wiley & Sons, Ltd.     

Cluster‐based adaptive multispectrum sensing and access in cognitive radio networks

Spectrum sensing and access have been widely investigated in cognitive radio network for the secondary users to efficiently utilize and share the spectrum licensed by the primary user. We propose a cluster‐based adaptive multispectrum sensing and access strategy, in which the secondary users seeking to access the channel can select a set of channels to sense and access with adaptive sensing time. Specifically, the spectrum sensing and access problem is formulated into an optimization problem, which maximizes the utility of the secondary users and ensures sufficient protection of the primary users and the transmitting secondary users from unacceptable interference. Moreover, we explicitly calculate the expected number of channels that are detected to be idle, or being occupied by the primary users, or being occupied by the transmitting secondary users. Spectrum sharing with the primary and transmitting secondary users is accomplished by adapting the transmission power to keep the interference to an acceptable level. Simulation results demonstrate the effectiveness of our proposed sensing and access strategy as well as its advantage over conventional sensing and access methods in terms of improving the achieved throughput and keeping the sensing overhead low. Copyright © 2012 John Wiley & Sons, Ltd.