4,982 research outputs found
A Novel Beamformed Control Channel Design for LTE with Full Dimension-MIMO
The Full Dimension-MIMO (FD-MIMO) technology is capable of achieving huge
improvements in network throughput with simultaneous connectivity of a large
number of mobile wireless devices, unmanned aerial vehicles, and the Internet
of Things (IoT). In FD-MIMO, with a large number of antennae at the base
station and the ability to perform beamforming, the capacity of the physical
downlink shared channel (PDSCH) has increased a lot. However, the current
specifications of the 3rd Generation Partnership Project (3GPP) does not allow
the base station to perform beamforming techniques for the physical downlink
control channel (PDCCH), and hence, PDCCH has neither the capacity nor the
coverage of PDSCH. Therefore, PDCCH capacity will still limit the performance
of a network as it dictates the number of users that can be scheduled at a
given time instant. In Release 11, 3GPP introduced enhanced PDCCH (EPDCCH) to
increase the PDCCH capacity at the cost of sacrificing the PDSCH resources. The
problem of enhancing the PDCCH capacity within the available control channel
resources has not been addressed yet in the literature. Hence, in this paper,
we propose a novel beamformed PDCCH (BF-PDCCH) design which is aligned to the
3GPP specifications and requires simple software changes at the base station.
We rely on the sounding reference signals transmitted in the uplink to decide
the best beam for a user and ingeniously schedule the users in PDCCH. We
perform system level simulations to evaluate the performance of the proposed
design and show that the proposed BF-PDCCH achieves larger network throughput
when compared with the current state of art algorithms, PDCCH and EPDCCH
schemes
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Self-organising network management for heterogeneous LTE-advanced networks
This thesis was submitted for the award of Doctor of Philosophy and awarded by Brunel University LondonSince 2004, when the Long Term Evolution (LTE) was first proposed to be publicly available in the year 2009, a plethora of new characteristics, techniques and applications have been constantly enhancing it since its first release, over the past decade. As a result, the research aims for LTE-Advanced (LTE-A) have been released to create a ubiquitous and supportive network for mobile users. The incorporation of heterogeneous networks (HetNets) has been proposed as one of the main enhancements of LTE-A systems over the existing LTE releases, by proposing the deployment of small-cell applications, such as femtocells, to provide more coverage and quality of service (QoS) within the network, whilst also reducing capital expenditure. These principal advantages can be obtained at the cost of new challenges such as inter-cell interference, which occurs when different network applications share the same frequency channel in the network. In this thesis, the main challenges of HetNets in LTE-A platform have been addressed and novel solutions are proposed by using self-organising network (SON) management approaches, which allows the cooperative cellular systems to observe, decide and amend their ongoing operation based on network conditions. The novel SON algorithms are modelled and simulated in OPNET modeler simulation software for the three processes of resource allocation, mobility management and interference coordination in multi-tier macro-femto networks. Different channel allocation methods based on cooperative transmission, frequency reuse and dynamic spectrum access are investigated and a novel SON sub-channel allocation method is proposed based on hybrid fractional frequency reuse (HFFR) scheme to provide dynamic resource allocation between macrocells and femtocells, while avoiding co-tier and cross-tier interference. Mobility management is also addressed as another important issue in HetNets, especially in hand-ins from macrocell to femtocell base stations. The existing research considers a limited number of methods for handover optimisation, such as signal strength and call admission control (CAC) to avoid unnecessary handovers, while our novel SON handover management method implements a comprehensive algorithm that performs sensing process, as well as resource availability and user residence checks to initiate the handover process at the optimal time. In addition to this, the novel femto over macro priority (FoMP) check in this process also gives the femtocell target nodes priority over the congested macrocells in order to improve the QoS at both the network tiers. Inter-cell interference, as the key challenge of HetNets, is also investigated by research on the existing time-domain, frequency-domain and power control methods. A novel SON interference mitigation algorithm is proposed, which is based on enhanced inter-cell interference coordination (eICIC) with power control process. The 3-phase power control algorithm contains signal to interference plus noise ratio (SINR) measurements, channel quality indicator (CQI) mapping and transmission power amendments to avoid the occurrence of interference due to the effects of high transmission power. The results of this research confirm that if heterogeneous systems are backed-up with SON management strategies, not only can improve the network capacity and QoS, but also the new network challenges such as inter-cell interference can also be mitigated in new releases of LTE-A network
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LTE-Advanced radio access enhancements: A survey
Long Term Evolution Advanced (LTE-Advanced) is the next step in LTE evolution and allows operators to improve network performance and service capabilities through smooth deployment of new techniques and technologies. LTE-Advanced uses some new features on top of the existing LTE standards to provide better user experience and higher throughputs. Some of the most significant features introduced in LTE-Advanced are carrier aggregation, enhancements in heterogeneous networks, coordinated multipoint transmission and reception, enhanced multiple input multiple output usage and deployment of relay nodes in the radio network. Mentioned features are mainly aimed to enhance the radio access part of the cellular networks. This survey article presents an overview of the key radio access features and functionalities of the LTE-Advanced radio access network, supported by the simulation results. We also provide a detailed review of the literature together with a very rich list of the references for each of the features. An LTE-Advanced roadmap and the latest updates and trends in LTE markets are also presented
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