Alexandra Konek

Method for improving the performance of dynamically changing mobile networks

Content

• Introduction
• 1. Relevance of the topic
• 2. The purpose and objectives of the research
• 3. The principle of organizing a cellular network
• 4. Overview of the equipment used on the wireless network
• 5. Power consumption model of a dynamically changing wireless network
• Conclusion
• List of sources

Introduction

One of the most progressive areas of science and technology is networking. Dynamically changing mobile networks are one of the fastest growing areas in this area. With the advent of a large number of wireless devices, the user has the opportunity to freely move around the territory the globe without losing contact with people important to him. This advantage has contributed to the rise in popularity of wireless networks.

Compared to wired networks, wireless networks have several advantages:

• simplicity of network creation and expansion;

• mobility;

• the ability to simultaneously connect multiple devices.

The more wireless networks are available, the higher the number of subscribers using them, which in turn leads to an increase in the number of different wireless data networks, therefore, increasing interference in each specific network. Such popularity and prevalence creates many problems for the solution of which it is necessary to use new methods of information transmission, a higher level of service for subscribers. Today almost any radio communication network is mobile. However, the term mobile communication is used in those radio systems in which the main what matters is the location of the subscriber relative to the equipment and the organization of communication systems. Thus, the TV and radio broadcasting cannot be called mobile communication systems, since they do not search for a subscriber, establish and maintain a communication channel with this subscriber when he moves in the area, served by the network.

Today almost any radio communication network is mobile. However, the term mobile communication is used in those radio systems in which the location of the subscriber relative to the equipment and their organization is of prime importance.

1. Relevance of the topic

There is a huge increase in mobile traffic in the world today, which is caused by the evolution of mobile devices and an increase in the number of broadband services. To handle such a large volume of traffic, it is necessary to increase the bandwidth the ability of base stations. Due to the growing demand for high quality service for subscribers using mobile networks, 2 main questions arise: load distribution on the network, depending on the number of subscribers and the cost of the required network infrastructure. Both problems can be solved by designing an energy efficient mobile network: reducing the network's energy consumption will lead to a decrease in operational infrastructure costs, and will also lead to improved communication quality during a call.

The master's thesis is devoted to the urgent scientific task of developing a method for increasing the performance of mobile networks aimed at to reduce the cost of network power consumption.

2. The purpose and objectives of the research, planned results

The purpose of the research is to develop a method for increasing the performance of a conditional dynamically changing mobile network.

The main objectives of the research:

1. Analysis of the main parameters characterizing the effectiveness of mobile wireless networks, and the factors on which they depend.
2. Development of a method for calculating performance indicators of a wireless network, taking into account the real conditions of its operation.
3. Modeling the adaptation algorithm of the main network parameters.

Object of study: the process of quality management of the provided mobile communication services.

Subject of study: a method of transferring base stations to sleep mode, to reduce network power consumption.

Within the framework of the master's work, it is planned to obtain relevant scientific results in the following areas:

1. Development of a method for calculating performance indicators of a wireless network, taking into account the conditions of its functioning.
2. Modeling the adaptation algorithm of the main network parameters.

For an experimental assessment of the theoretical results obtained and the formation of the foundation for subsequent research, as practical results it is planned development of a model of a conditional dynamically changing wireless network.

3. The principle of organizing a cellular network

The organization of a cellular network is based on the use of a large number of transmitters with low power and short range. The territory (zone) served by the system is divided into cells. Each cell has its own frequency band. To avoid influence For crosstalk, different frequencies are allocated to adjacent cells. However, cells located at a great distance from each other can use the same frequency bands.

The higher the number of mobile subscribers in the network, the higher the load both on each base station of the network and on the network itself. In this regard, it is necessary to increase the bandwidth. Consequently, the number of access points increases. This leads to the emergence of networks with higher bandwidth - high-density. Users of such networks are rarely out of range. This raises the problem of assigning a unique operating frequency to each base station. It is solved by reusing frequencies (Fig. 1).

Network bandwidth depends on:

• the number of frequency channels of the base station;

• bandwidth of the communication channel;

• frequency reuse factor.

From this we can conclude that in order to increase the throughput, it is necessary to increase the recycle ratio use of frequencies and determine a sufficient number of frequency communication channels.

The channel capacity of the base station (number of frequency channels) is one of the main parameters to be definition in the network design process, and depends on:

• the most probable number of mobile subscribers capable of creating an appropriate load on it;

• their distribution in the network or coverage area of the base station;

• the probability of failure to establish a connection at the first attempt;

• specific load from subscribers;

• terrain.

In addition to bandwidth, the network is characterized by its capacity. Network capacity is a quantity characterized by the load on network area in a dedicated frequency band. The higher the network capacity, the more traffic, i.e. more subscribers can be served, without increasing the system bandwidth. For each type of network, there is a limit value of the capacity, above which the capacity is realized the network will fail. This limiting capacity is related to the maximum amount of traffic density that a given network is able to serve. with a given quality of information transfer. For a given throughput of base stations, the higher the traffic density, the less there must be a cell size and, therefore, the smaller is the distance between cells with the same set of frequency channels. As a result, at a certain traffic density, these distances and, accordingly, the total propagation loss between the antennas of the cells, using the same frequencies are so small that they lead to unstable network operation. There are various methods of raising the efficiency of the network and its bandwidth, however, they are aimed at adjusting a single parameter. Wednesday, in which there are mobile wireless networks, constantly changing, dynamic, and the problems that it creates, it is impossible to solve by adjusting any one parameter. To determine the level of mutual interference (interference from mobile subscribers) the method of the equivalent generator is used, which allows to relate the interference power from mobile subscribers with such parameters how: distribution of subscribers in the coverage area of a base station or network; distance between centers of base stations using the same frequencies; radius of the coverage area of the base station, etc. The network requires careful approach to its design and optimization. This is the only way to organize work various network components operating simultaneously in real operating conditions with the required quality, without creating unacceptable interference with each other.

4. Overview of the equipment used on the wireless network

In the case of cellular networks, the most energy-consuming equipment is the base station, the consumption of which ranges from 0.5 kW to 2 kW power [1, 2], including power amplifiers, digital signal processors, etc. Together, base stations account for about 80% of total cellular network power consumption. [3].

Cellular base stations (BSs) are of a certain size. These include femtocells, picocells, microcells, and macrocells.

Femtocells and picocells are used for domestic and corporate purposes. They are not intended to serve subscribers in urban conditions.

Next largest: micro and macro cells. Microcell is a functional cellular communication station with a range of up to 5 km. Such BSs are used mainly in villages or suburbs where there is no need for high power. A macro cell is a large base station for serving densely populated areas. Macros are very complex and expensive to deploy and operation, especially in urban environments. Therefore, the most common deployment option can be used networks – a heterogeneous network. It is a network in which micro and pico cells (also called small cells) are superimposed on macro cells. Such a network is shown in Figure 2. Network deployments are designed to provide enough capacity to handle incoming traffic, and it has been observed that due to this dimension, network equipment spends most of its time (and therefore most of its energy) to turn on with very low or even no traffic load [4]. Hence, A promising solution is to dynamically put some network elements into sleep mode during periods of low load.

Thus, the network will operate with a minimal subset of network elements sufficient for high-quality service to subscribers at a given time, while the rest of the network equipment is in a state low power consumption (called sleep mode) or even turned off.

In order to make the transition to sleep mode, consider the power consumption model.

5. Power consumption model of a dynamically changing wireless network

Let us assume that in the considered area, all base stations have the same power consumption.

Let be W_S – power consumption in sleep mode for each base station. In that case, when the base station receives a load f(t), the power consumption of the station can be expressed as:

(1)

where, W₀ – the power required to activate the BS;

W_T – the power required to process one unit of traffic;

t ∈ [0;T], T = 24h, t = 0 – busy hour;

f(t) – the function describing the load in the hour of full load, therefore

In expression (1), the condition must be satisfied under which the sum of all three power components is equal to 1.

Obviously, the values W_S , W₀ и W_T   depend from the technology and model of the BS, but usually the component dominates W₀  [2]. Generally, the higher the power consumption in state S, the shorter the BS activation time.

Thus, the values will depend on the policy that the operator wants to accept, based on the times when stations are activated or deactivated.

Low values will be used in calculations here W_S, due to the transition of the station to the state S just a few times a day.

Consequently, the activation or deactivation time, even if it is large in absolute terms (for example, tens of seconds or even several minutes), may be considered negligible in relation to long sleep intervals.

The energy consumed per day by a BS in a cellular network, in which all BSs remain always on, can be determined from the expression:

(2)

Consider a network in which at the moment of time τ low power configuration applied φ. In this case, BSs have different daily consumption, depending on whether they are always on or go to sleep at low load. Energy consumed during the day by the base station, which goes into sleep mode according to the configuration φ,is:

(3)

since, from 0 to τ and from T − τ to T – the BS is on, while the rest of the day is in the sleep state.

In practice, this model can be represented as shown in Fig. 3.

The shown network is conditional. This network contains 6 randomly located base stations. All of them are off, that is, they are in sleep mode. As soon as a smartphone appears in the coverage area of BS3, BS switches from sleep to active mode. Likewise, turn on all other base stations when new users arrive.

Conclusion

In the process of performing a master's thesis on Method of increasing the performance of dynamically changing mobile networks the relevance of the work, its purpose and the tasks that need to be performed to improve the efficiency of the wireless network were established.

The master's thesis is devoted to the urgent scientific problem of improving the performance of dynamically changing wireless networks. As part of the research carried out:

1. The analysis of the main parameters characterizing the efficiency of mobile wireless networks, and the factors on which they depend.
2. The wireless equipment being used has been identified.
3. The model of energy consumption of a dynamically changing mobile network is considered.

Further research focuses on the following aspects:

1. Analysis of the base station sleep model.
2. Determination of network parameters that affect the operation of base stations.
3. Simulation of a conditional dynamically changing network based on OMNET++ software.

When writing this abstract, the master's thesis has not yet been completed. Final completion: May 2021. Full text of the work and materials on the topic can be obtained from the author or his manager after that date.

List of sources

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