3 research outputs found
Recommended from our members
Cognitive radio systems in LTE networks
This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London.The most important fact in the mobile industry at the moment is that demand for wireless services will continue to expand in the coming years. Therefore, it is vital to find more spectrums through cognitive radios for the growing numbers of services and users. However, the spectrum reallocations, enhanced receivers, shared use, or secondary markets-will not likely, by themselves or in combination, meet the real exponential increases in demand for wireless resources. Network operators will also need to re-examine network architecture, and consider integrating the fibre and wireless networks to address this issue. This thesis involves driving fibre deeper into cognitive networks, deploying microcells connected through fibre infrastructure to the backbone LTE networks, and developing the algorithms for diverting calls between the wireless and fibre systems, introducing new coexistence models, and mobility management. This research addresses the network deployment scenarios to a microcell-aided cognitive network, specifically slicing the spectrum spatially and providing reliable coverage at either tier. The goal of this research is to propose new method of decentralized-to-distributed management techniques that overcomes the spectrum unavailability barrier overhead in ongoing and future deployments of multi-tiered cognitive network architectures. Such adjustments will propose new opportunities in cognitive radio-to-fibre systematic investment strategies. Specific contributions include:
1) Identifying the radio access technologies and radio over fibre solution for cognitive network infrastructure to increase the uplink capacity analysis in two-tier networks.
2) Coexistence of macro and microcells are studied to propose a roadmap for optimising the deployment of cognitive microcells inside LTE macrocells in the case of considering radio over fibre access systems.
3) New method for roaming mobiles moving between microcells and macrocell coverage areas is proposed for managing spectrum handover, operator database, authentication and accounting by introducing the channel assigning agent entity. The ultimate goal is to reduce unnecessary channel adaptation
Final report on the evaluation of RRM/CRRM algorithms
Deliverable public del projecte EVERESTThis deliverable provides a definition and a complete evaluation of the RRM/CRRM algorithms selected in D11 and D15, and evolved and refined on an iterative process. The evaluation will be carried out by means of simulations using the simulators provided at D07, and D14.Preprin
Dense wireless network design and evaluation – an aircraft cabin use case
One of the key requirements of fifth generation (5G) systems is having a connection to mobile
networks without interruption at anytime and anywhere, which is also known as seamless connectivity.
Nowadays, fourth generation (4G) systems, Long Term Evolution (LTE) and Long
Term Evolution Advanced (LTE-A), are mature enough to provide connectivity to most terrestrial
mobile users. However, for airborne mobile users, there is no connection that exists
without interruption. According to the regulations, mobile connectivity for aircraft passengers
can only be established when the altitude of the aircraft is above 3000 m. Along with demands
to have mobile connectivity during a flight and the seamless connectivity requirement of 5G
systems, there is a notable interest in providing in-flight wireless services during all phases of
a flight. In this thesis, many issues related to the deployment and operation of the onboard
systems have been investigated.
A measurement and modelling procedure to investigate radio frequency (RF) propagation inside
an aircraft is proposed in this thesis. Unlike in existing studies for in-cabin channel characterization,
the proposed procedure takes into account the deployment of a multi-cell onboard
system. The proposed model is verified through another set of measurements where reference
signal received power (RSRP) levels inside the aircraft are measured. The results show that
the proposed model closely matches the in-cabin RSRP measurements. Moreover, in order to
enforce the distance between a user and an interfering resource, cell sectorization is employed
in the multi-cell onboard system deployment. The proposed propagation model is used to find
an optimum antenna orientation that minimizes the interference level among the neighbouring
evolved nodeBs (eNBs).
Once the optimum antenna deployment is obtained, comprehensive downlink performance evaluations
of the multi-cell, multi-user onboard LTE-A system is carried out. Techniques that are
proposed for LTE-A systems, namely enhanced inter-cell interference coordination (eICIC) and
carrier aggregation (CA), are employed in the system analysis. Different numbers of eNBs, antenna
mounting positions and scheduling policies are examined. A scheduling algorithm that
provides a good tradeoff between fairness and system throughput is proposed. The results show
that the downlink performance of the proposed onboard LTE-A system achieves not only 75%
of the theoretical limits of the overall system throughput but also fair user data rate performance,
irrespective of a passenger’s seat location.
In order to provide the seamless connectivity requirement of 5G systems, compatibility between
the proposed onboard system deployment and the already deployed terrestrial networks
is investigated. Simulation based analyses are carried out to investigate power leakage from
the onboard systems while the aircraft is in the parked position on the apron. According to
the regulations, the onboard system should not increase the noise level of the already deployed
terrestrial system by 1 dB. Results show that the proposed onboard communication system can
be operated while the aircraft is in the parked position on the apron without exceeding the 1 dB
increase in the noise level of the already deployed terrestrial 4G network. Furthermore, handover
parameters are obtained for different transmission power levels of both the terrestrial and
onboard systems to make the transition from one system to another without interruption while
a passenger boards or leaves the aircraft. Simulation and measurement based analyses show
that when the RSRP level of the terrestrial system is below -65 dBm around the aircraft, a
boarding passenger can be smoothly handed over to the onboard system and vice versa. Moreover,
in order to trigger the handover process without interfering with the data transmission, a
broadcast control channel (BCCH) power boosting feature is proposed for the in-cabin eNBs.
Results show that employing the BCCH power boosting feature helps to trigger the handover
process as soon as the passengers step on board the aircraft