Citation
Mamman, Maharazu
(2018)
Efficient radio resource management algorithms for downlink long term evolution networks.
Doctoral thesis, Universiti Putra Malaysia.
Abstract
The increasing demand for wireless network services, particularly for downlink
broadband communication has triggered the evolution of cellular networks.
The Third Generation Partnership Project (3GPP) introduced the Long Term
Evolution (LTE) in response to the forthcoming fourth-generation (4G) cellular
networks. LTE is a very complex and large standard. Its performance is
dependent on the large range of elements. One of the key essential elements
is Radio Resource Management (RRM). RRM has a great impact on the system
performance due to many problematic aspects such as packet scheduling, Call
Admission Control (CAC) and Energy Efficiency (EE).
With the aim to meet the LTE QoS requirements (i.e. Quality of Service (QoS),
fairness provisioning, minimal delay, packet loss, and throughput maximization),
the objective of scheduling algorithm is critical to use limited available
spectrum. As long as choosing an appropriate scheduling algorithm is not
standardized by the 3GPP specification for LTE, vendors are free to adopt,
configure and implement their own algorithms depending on the problems of
the system. Nevertheless, achieving all the intended objectives simultaneously
is difficult. Each problem solved can lead to additional ones. For instance,
radio resource algorithms intended to maximize system throughput are not
appropriate for handling guaranteed bit rate traffic. Hence, the major problem
is developing a scheduling algorithm which creates a trade-off between the
system performances.
It is imperative to note that, in spite of the network-wide control schemes to ease
transmission order, mobile data content overwhelms the available bandwidth for each node in many high traffic times. According to this premise, it is
understandable that the transmission order is an inevitable issue in LTE mobile
networks. Therefore, this thesis examines the efficient resource scheduling
algorithms to be resistant to the unpredicted transmission order patterns.
Firstly, a QoS channel quality identifier algorithm is proposed, to support the
transmission order of users while considering the QoS requirements as well as
the channel condition. The algorithm is based on the idea of the optimization
problem in which resource allocation problem is formulated as an optimization
problem. Optimal priority algorithm uses minimum data rate to guarantees
resource allocation to users but increases the average delay and deteriorate
the network performance. Therefore, the proposed algorithm minimizes the
average delay and improves the network performance.
In addition to network deterioration, the admitting of users to the network
environment contributes to the ineffective use of resources. Thus, we proposed a
call admission control algorithm that admits users to utilize available resources.
It adaptively defines how users should be admitted, by considering the network
conditions.
Furthermore, to deal with the energy consumption problem and provide a
trade-off between spectral and energy efficiency, we proposed a spectral and
energy efficiency trade-off algorithm. Unlike other algorithms that prolong the
battery lifetime by considering the idle state of the base station, thus increasing
the average delay and increases the energy consumption. Our algorithms
prolong the battery life by adjusting the base station using initial and final states.
Consequently, minimizes the average delay as well as low energy consumption.
Similarly, the use of omnidirectional antenna to spread radio signals to UEs
in all directions causes high interference and low special reuse. We proposed
the used of the directional antenna to replaces the omnidirectional antenna by
transmitting signals in one direction 600 and 1200 which resulted in no or less
interference as well as high spatial reuse.
Substantial simulations have been extensively carried out to evaluate the
performance of the proposed algorithms compared with the existing RRM
algorithms. The findings demonstrate that the proposed algorithms have
shown significant improvements, which includes: lowering delay, minimizes
packet loss, improve fairness, and increases the throughput of the system in
the proposed QoS channel quality indicator algorithm. Secondly, the proposed
call admission control algorithm improved the resource utilization algorithm
thus reducing the call block, call dropped, call degradation. This has further
enabled the improvement of data throughput. Lastly, reducing the amount of
energy consumed and lowering delay is shown in the proposed spectral-energy
efficiency algorithm.
Overall, the research has shown promising support and improvements to LTE
networks scheduling algorithms and to associated challenges in wireless communication
paradigm. Likewise, it would be valuable if the proposed scheduling
algorithms are evaluated on anticipated networks covering a large number
of users in further research.
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