Global roaming
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There are a number of scheduling algorithms. In the simplest case, the resources are distributed between the subscribers in order of receipt of requests, not taking into account the structure of the transmitted data and other conditions (Algorithm Round Robin). Other algorithms make decisions based on the channel quality and allocate resources to the subscriber with the best quality (algorithm Best CQI). This scheduling algorithm can increase system capacity by using optimal modulation and coding scheme.

More sophisticated scheduling algorithms take into account the data presented in the subscriber's request, and perform resources allocation in order of priority of the available data. Currently, users can run simultaneously different applications on their client devices. In this case, each application has its own requirements for quality of service. Each type of data is assigned with QoS Class Identifier (QCI). Each QCI determines the values for the following parameters QoS: priority, acceptable delay, and allowable number of packets lost.

As a rule, the priority value and the allowable delay determine how eNodeB scheduler will process the data packets [1].

The LTE system throughput strongly depends on the frequency and time domain allocation algorithm (scheduling algorithm). The algorithms are not defined in specifications and are developed by equipment suppliers. The correct choice of the algorithm can improve system throughput without increasing bandwidth.

At the moment, a set of algorithms are developing with the aim of more efficient system resources usage. Researches allow to estimate the effectiveness of each algorithm and to understand the conditions under which it is more effective.

Many scientists make researches in this area. Numerous scientific articles have written on the subject [3-4].

 

1.2          Experimental results of researches

During researches simulation models of Round Robin and Best CQI scheduling algorithms were developed.

The simulation model allows to estimate LTE system capacity under different parameters. The study yielded the following plots shown in Figures 4 and 5.

Figure 3 shows plots of throughput depending on the intensity of the input load for various system parameters.