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Proceedings ArticleDOI

Performance analysis of an improved CSI feedback technique for LTE-A system with Femtocell Interference

17 Mar 2016-pp 1055-1058
TL;DR: A modified dirty paper coding technique to mitigate the effect of inter-cell interference is introduced and results shows that sum rate of Modifieddirty paper coding is 23% more than Zero-Forcing technique.
Abstract: The major challenge in Long Term Evolution Advanced (LTE-A) based 5G network is to improve the cell capacity and cell coverage of indoor users. To fulfill these demands, low power Femto Base stations are deployed at homes and company premises. Such heterogeneous network introduces interference due to both Femtocell and microcell users, especially for cell edge users as the frequencies are reused intrusively. In this Paper, we are introduce a modified dirty paper coding technique to mitigate the effect of inter-cell interference. To reduce the effect of interference, each user feedback quantize CSI to base station and then appropriate precoding is done on transmitted signal. Here, we are compare the sum rate of the Modified Dirty Paper Coding and Zero-Forcing technique. Simulation results shows that sum rate of Modified dirty paper coding is 23% more than Zero-Forcing technique.
Citations
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Journal ArticleDOI
TL;DR: SINR, system capacity, minimum and maximum rates of the system are analyzed when coordination is applied between the cells and three different scenarios are discussed, which includes coordinated multipoint transmission and reception (COMP), non-COMP and DCBS and the results of these scenarios are compared.
Abstract: The performance of long term evolution-advance (LTE-A) depends on different factors such as spectral efficiency, throughput and signal interference to noise ratio (SINR). Interference causes the performance of a network to be grassed to very low level, it directly affects the parameters such as noise interference, receiving diversity and system receiving gain so to mitigate the interference in LTE-A network is very important. Interference occurs in two forms, intra-cell interference and inter-cell interference. Intra-cell interference is removed by orthogonal frequency division multiple access, but the problem of inter-cell interference still exists due to reception of signals from two adjacent base stations at same frequency on user equipment, so coordination is applied between the cells to reduce the interference between the cells. This paper focuses on coordination between the base stations using dynamic cooperative Base Station selection (DCBS). In this paper, SINR, system capacity, minimum and maximum rates of the system are analyzed when coordination is applied between the cells. Three different scenarios are discussed in this paper, which includes coordinated multipoint transmission and reception (COMP), non-COMP and DCBS and then the results of these scenarios are compared.

7 citations

Journal ArticleDOI
01 Oct 2020
TL;DR: In this paper, a modified dirty paper coding is proposed for interference mitigation along with the optimization of feedback bits using natural inspired meta-heuristic firefly algorithm, which reduces the interference by periodically unicasting the channel state information.
Abstract: Femtocells are the feasible solutions to extend the network coverage of indoor users and to enhance the network capacity in long-term evolution advanced (LTE-A)-based 5G networks. However, the femtocell base station shares the same frequency spectrum of microcell base station in unplanned manner. Hence, interference mitigation is a crucial problem in densely deployed femtocell environment and it is more severe with the deployment of femtocells in LTE-A network. In this paper, a modified dirty paper coding is proposed for interference mitigation along with the optimization of feedback bits using natural inspired meta-heuristic firefly algorithm. The proposed meta-heuristic algorithm reduces the interference by periodically unicasting the channel state information. Since the bandwidth of feedback system is limited, it is optimized in such a way that it does not affect the performance of the system. As compared to the conventional zero-forcing pre-coding, the proposed modified dirty paper coding along with firefly algorithm scheme offers improved sum rate of 70% and 64% with increase in the number of feedback bits and number of users, respectively.

1 citations

References
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Journal ArticleDOI
TL;DR: The technical and business arguments for femtocells are overview and the state of the art on each front is described and the technical challenges facing femtocell networks are described and some preliminary ideas for how to overcome them are given.
Abstract: The surest way to increase the system capacity of a wireless link is by getting the transmitter and receiver closer to each other, which creates the dual benefits of higher-quality links and more spatial reuse. In a network with nomadic users, this inevitably involves deploying more infrastructure, typically in the form of microcells, hot spots, distributed antennas, or relays. A less expensive alternative is the recent concept of femtocells - also called home base stations - which are data access points installed by home users to get better indoor voice and data coverage. In this article we overview the technical and business arguments for femtocells and describe the state of the art on each front. We also describe the technical challenges facing femtocell networks and give some preliminary ideas for how to overcome them.

3,298 citations

Journal ArticleDOI
TL;DR: This paper proposes an efficient CSI quantization technique for BD preceded systems with limited feedback where users supported by a base station are selected by dynamic scheduling and achieves a significant sum rate gain over the conventional method in practical MU-MIMO systems.
Abstract: Block diagonalization (BD) has been proposed as a simple and effective technique in multiuser multiple-input multiple-output (MU-MIMO) broadcast channels. However, when channel state information (CSI) knowledge is limited at the transmitter, the performance of the BD may be degraded because inter-user interference cannot be completely eliminated. In this paper, we propose an efficient CSI quantization technique for BD preceded systems with limited feedback where users supported by a base station are selected by dynamic scheduling. First, we express the received signal-to-interference-plus-noise ratio (SINR) when multiple data streams are transmitted to the user, and derive a lower bound expression of the expected received SINR at each user. Then, based on this measure, each user determines its quantized CSI feedback information which maximizes the derived expected SINR, which comprises both the channel direction and the amplitude information. From simulations, we confirm that the proposed SINR-based channel quantization scheme achieves a significant sum rate gain over the conventional method in practical MU-MIMO systems.

20 citations

Journal ArticleDOI
TL;DR: This paper develops three MIMO beamforming schemes for interference mitigation that take into account the Quality of Service (QoS) requirement of both femtocell and macrocell clients, and extends the proposed interference control precoding schemes to spatial multiplexing for MIMo transmissions.
Abstract: This paper studies interference mitigation in heterogeneous cellular networks consisting of traditional macrocells and newly envisioned femtocells. The mutual interference between macrocells and femtocells arises as a result of decentralized femtocell deployment and backhaul delay. To mitigate downlink interference between the femtocell clients, known as Home User Equipments (HUEs), and macrocell clients, known as Macrocell User Equipments (MUEs), we present methods of dynamic distributed beamforming that are fully compatible with MIMO precoding mechanisms in existing LTE standard releases. We develop three MIMO beamforming schemes for interference mitigation that take into account the Quality of Service (QoS) requirement of both femtocell and macrocell clients. These new heterogeneous MIMO precoding strategies improve flexibility in resource provisioning and signaling requirement while responding to different QoS needs. We also present MUE mean throughput analysis by applying order statistics to our proposed methods. Moreover, we provide an approximate closed form for the mean throughput in terms of basic transmitter, channel, and receiver parameters. Furthermore, we extend our proposed interference control precoding schemes to spatial multiplexing for MIMO transmissions. Finally, we extend our solution to tackle the more general case involving multiple MUEs, multiple HUEs, and multiple femtocells.

16 citations

Journal ArticleDOI
TL;DR: Interference mitigation schemes for LTE downlink networks are investigated and can restrict overall system performance in terms of throughput and spectral efficiency, especially for the users located at the cell edge area.
Abstract: Two major challenges for evolving LTE (Long Term Evolution) networks are to achieve enhanced system capacity and cell coverage compared with WCDMA (Wideband Code Division Multiple Access) system. Effective utilization of radio resources as well as dense spectrum reuse are at the core to attain these targets. However, dense frequency reuse may increase inter-cell interference, which in turn severely limits the capacity of users in the system. Inter-cell interference can restrict overall system performance in terms of throughput and spectral efficiency, especially for the users located at the cell edge area. Hence, careful management of inter-cell interferences becomes crucial to improve LTE system performance. In this paper, interference mitigation schemes for LTE downlink networks are investigated.

14 citations

Journal ArticleDOI
TL;DR: This paper presents a novel precoding technique which allows the joint precoding of legacy and new users, and ensures that no perturbations are made to linearly precoded users, while minimising the power normalisation using a modified sphere encoder.
Abstract: Multiuser MIMO vector perturbation precoding facilitates multiple representations of the transmit symbols in order to improve transmit power normalisation of the transmitted signal All the receiver needs to do is to apply a modulo operation to undo the perturbation However existing system with multiuser MIMO support, such as LTE, employ linear precoding This means that these legacy users will not be able to operate together with new users with vector perturbation capabilities, reducing the system throughput and flexibility in resource allocation In this paper we present a novel precoding technique which allows the joint precoding of legacy and new users The precoding ensures that no perturbations are made to linearly precoded users, while minimising the power normalisation using a modified sphere encoder We also show that the diversity order of the joint precoding scheme is the difference between the number of transmit antennas and the number of legacy users, regardless of the number of new users

13 citations