RU2814537C1 - Method for planning joint operation of lte and gsm cellular communication networks - Google Patents

Abstract

FIELD: wireless communication.

SUBSTANCE: allocated radio frequency spectrum, which includes the operating frequency spectrum and protective intervals at the edges of the operating spectrum, is used so that the operating spectrum is divided into first, second and third frequency bands, wherein the second frequency band is located between the first and third, wherein all base stations of the cellular network are divided into two groups, where the base stations of the first group are configured to exchange radio signals with mobile stations using frequencies of the first frequency band and guard intervals for GSM technology, frequencies of the second and third frequency bands for LTE technology; and base stations of the second group — using frequencies of the third frequency band and guard intervals for GSM technology, frequencies of the second and first frequency bands for LTE technology; wherein the base stations closest to each other belong to different groups, and in the neighbouring cells formed by the base stations, the same frequencies for GSM technology are not used.

EFFECT: providing GSM coverage of adequate quality with minimum blocking of spectrum frequencies, which can be used for LTE technology.

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Description

A group of inventions relates to a cellular communication method and system, a method for planning joint operation of LTE and GSM cellular networks, in particular, to a method for distributing network resources between GSM and LTE technologies and a system of base stations for its implementation. A group of inventions can be used in the development of a frequency territorial plan (FTP) in order to increase the efficiency of using the frequency resource.

State of the art

In cellular wireless systems, operators use licenses for fixed portions of spectrum in which they can operate a cellular wireless network that operates under a standardized technology such as the Global System for Mobile Communications (GSM), the Universal Mobile Telecommunications System (UMTS), or a long-term design. development of communication systems (LTE). An operator migrating from one technology to another must make the transition gradually, transferring part of the spectrum to the newer technology, while continuing to support the network of terminals that do not support the new technology. However, such a transition may not necessarily result in a complete transition to a new technology. For example, in the case of GSM (old technology) and LTE (new technology) technologies, operators cannot allocate the entire spectrum to LTE technology. This is due to various reasons: some users have equipment that does not support LTE technology, government regulation, etc. Thus, it is necessary to divide the spectrum between GSM and LTE technologies. For this purpose, static spectrum division is used.

There are two different methods known in the prior art for static spectrum division between GSM and LTE technologies. For example, when statically dividing the spectrum between GSM 1800 and LTE 1800 with a 15 MHz frequency band having 75 physical resource blocks (PRBs), in the first division option for GSM technology, frequencies within the band are not allocated; GSM channels are located in LTE guard intervals (Fig. 1). The advantage of this division is the ability to use all 75 physical resource blocks for LTE technology. However, the use of frequencies only from the guard interval (for 15 MHz this is 6 channels of 0.2 MHz each) for GSM technology does not provide adequate quality coverage for this technology and reduces the service area, which is unacceptable.

In the second separation option, frequencies within the LTE band are allocated for GSM technology (Fig. 2). To maintain GSM quality at the proper level, 18 channels are required. In this case, adequate quality coverage is provided for GSM technology. However, this configuration blocks a significant portion of LTE resources. LTE radio frequency resources are divided into groups, so the 15 MHz band (excluding guard intervals of 0.75 MHz each at the edges of the band) is divided into 19 (ResourceBlockGroup - RBG) groups so that groups numbered 0 to 17 have a spectrum width 0.72 MHz (4 PRBs per group, with 1 PRB = 0.18 MHz), and group number 18 is 0.54 MHz (3 PRBs). In this case, the RBG entity is the minimum resource assigned by the resource scheduler (in the standard operation of the resource scheduler). In turn, channels of 0.2 MHz each are assigned for GSM technology.

Thus, in order to free up frequencies for a larger number of GSM 1800 channels, resources in LTE have to be turned off in multiples of groups. The above features degenerate into a stepwise dependence of the blocked resource of the new LTE spectrum on the required number of GSM channels.

For example, when expanding the LTE 1800 spectrum from 10 to 15 MHz, the available part of the new LTE spectrum (5 MHz) has to be partially blocked depending on the required number of GSM 1800 channels required to maintain quality in GSM 1800. As can be seen from the graph (Fig. 3 ), inclusion of more than 15 GSM channels will make 60 percent or more of the added LTE spectrum unavailable and virtually nullify the effect of such an expansion.

Thus, the problem of providing GSM coverage of appropriate quality with minimal blocking of spectrum frequencies that can be used for LTE technology is relevant and is solved by the claimed group of inventions.

The technical result is to provide GSM coverage of appropriate quality with minimal blocking of spectrum frequencies that can be used for LTE technology.

The technical result is achieved due to the fact that the allocated radio frequency spectrum, which includes the operating frequency spectrum and guard intervals at the edges of the operating spectrum, is used so that the operating spectrum is divided into the first, second and third frequency bands, with the second frequency band located between the first and third, all base stations of the cellular network are divided into two groups, where the base stations of the first group are configured to exchange radio signals with mobile stations using the frequencies of the first frequency band and guard intervals for GSM technology, the frequencies of the second and third frequency bands for LTE technology; and the base stations of the second group - using the frequencies of the third frequency band and guard intervals for GSM technology, the frequencies of the second and first frequency bands for LTE technology; Moreover, the base stations closest to each other belong to different groups, and the neighboring cells formed by the base stations do not use the same frequencies for GSM technology.

The technical result is also achieved due to the fact that the system of base stations of the cellular communication network consists of the first and second groups of base stations, configured to form cells and exchange radio signals with mobile stations at a given frequency in each cell formed by them, and used to exchange radio signals with mobile stations, the radio frequency spectrum includes the operating frequency spectrum and guard intervals at the edges of the operating spectrum, and the operating spectrum is divided into the first, third and second frequency bands located between them, and the base stations closest to each other belong to different groups, and in neighboring cells do not use the same frequencies for GSM technology, while the base stations of the first group are configured to exchange radio signals with mobile stations using the frequencies of the first frequency band and guard intervals for GSM technology, the frequencies of the second and third frequency bands for LTE technology; and the base stations of the second group - using the frequencies of the third frequency band and guard intervals for GSM technology, the frequencies of the second and first frequency bands for LTE technology.

The essence of the claimed technical solution is illustrated by the illustrations of Figures 1-9, where

- figure 1 shows the first method of static spectrum division;

- figure 2 shows the second method of static spectrum division;

- Fig. 3 shows a graph of the dependence of the blocked resource on the number of GSM 1800 channels with the second method of spectrum division;

- Fig. 4 shows the available spectrum, divided into three frequency bands;

- Fig. 5 shows cells of base stations belonging to different groups;

- Fig.6 shows the frequency bands allocated for GSM and LTE technologies for group A of base stations;

- in fig. 7 shows the frequency bands allocated for GSM and LTE technologies for group B of base stations;

- in fig. 8 shows graphs of the dependence of the blocked resource on the number of GSM 1800 channels with the standard and new approach;

- Fig.9 shows a diagram of the location of base stations of different groups when implementing the method.

Below is an example of the invention.

In the example implementation of the method disclosed below, the allocated frequency spectrum is 15 MHz and includes a working frequency spectrum of 13.5 MHz and guard intervals at the edges of the working spectrum of 0.75 MHz each. For GSM technology, 0.2 MHz channels are allocated.

In this case, for GSM technology channels, the frequencies of the guard intervals are used, resulting in 6 GSM channels (3 channels in each interval). For LTE technology, physical resource blocks (PRBs) of 0.18 MHz each are allocated in the available spectrum. In this case, LTE resources should be divided into 19 groups (RGB) in such a way that 18 groups with numbers from 0 to 17 have a spectrum width of 0.72 MHz, and group number 18 has a spectrum width of 0.54 MHz. Then, groups 0 to 17 have a resource of 4 PRB each, and group 18 has 3 PRB. All 19 groups (75 PRBs) fully use the resource of the operating frequency spectrum, however, in this case, GSM technology uses only 6 channels in the guard intervals, which does not provide coverage of adequate quality for this technology. As mentioned earlier, groups are the minimum resource that can be assigned to a user, therefore, in order to increase the number of GSM channels in the operating spectrum, it is necessary to reduce LTE resources in groups of 4 PRB or 3 PRB (in the case of group 18).

In the proposed method, the available spectrum is divided into three frequency bands (Fig. 4). The first and third frequency bands are at the edges of the available spectrum, adjacent to the guard intervals, and are allocated to either GSM or LTE technology. The second frequency band is located between them and is dedicated to LTE technology. For example, the first frequency band has a width of 1 MHz, then its resource can be allocated either for 5 GSM channels or for 1 LTE group of 0.72 MHz, including 4 PRBs. The third band can be 1.4 MHz wide, i.e. contain 7 GSM channels, or one group of 0.54 MHz and one group of 0.72 MHz (7 PRBs in total). Then the second band will have a width of 11.1 MHz and include 15 LTE groups of 0.72 MHz each
(total 60 PRB).

This example shows only one way to divide the 15 MHz frequency spectrum into three frequency bands. Within the framework of this application, the first, second and third frequency bands may have a different width, depending on the required network parameters (number of GSM channels, number of PRBs, etc.) At the same time, the allocated and, accordingly, operating frequency spectrum may also be different, for example, it is possible to use LTE 1800/900 bands, with a bandwidth from 5 to 20 MHz in clusters with any type of underlying surface: urban areas, suburbs, regional territories, etc.

The method is carried out through the exchange of radio signals between base stations and mobile stations.

Mobile stations can be, for example, smartphones, modems, etc. Mobile stations also contain an antenna system, a subscriber identification module (can be located either in the mobile station itself (Nano-SIM, eSIM, iSIM, etc.) or outside it (Virtual SIM)), and a computing device (for example, a microprocessor).

Base stations (BS) consist of an antenna system connected to a radio module, which in turn is connected to elements of the base station control system. Antennas receive and receive radio signals and can be sectoral, for example, panel antennas, in which case one base station can form several cells. The radio module contains a digital-to-analog converter (DAC) and an analog-to-digital converter (ADC). In the radio module, digital data is converted into analog electrical signals of a given frequency (and vice versa). The radio module forwards the resulting signals to the appropriate antennas or antenna via wire connections. Antennas convert the received electrical signal into radio waves, amplify it and distribute it in space. For each cell, at least one GSM channel is assigned, then for one BS with three sectors at least three channels are assigned, since it is highly not recommended to assign channels of the same frequency to neighboring cells in order to avoid interference of signals from neighboring and own cells.

Base stations are divided into two groups (group A and group B) on a territorial basis. The division occurs in such a way that the nearest base stations belong to different groups (Fig. 5).

Radio modules of group A, through elements of the base station control system, for each cell are assigned frequencies (channels of 0.2 MHz) for exchanging signals using GSM technology from the first frequency band and guard intervals, the remaining frequencies are assigned to LTE technology. Thus, cells formed by base stations from group A can be assigned at least 1 of 11 GSM channels (6 channels in guard intervals and 5 channels in the first frequency band). At the same time, 67 PRB resources will be available for LTE technology.

Radio modules of group B are also assigned frequencies (0.2 MHz channels) for the exchange of signals using GSM technology from the third frequency band and guard intervals through elements of the base station control system for each cell; the remaining frequencies are assigned to LTE technology. Then, cells formed by base stations from group B can be assigned at least 1 of 13 GSM channels (6 channels in guard intervals and 7 channels in the third frequency band). At the same time, 64 PRB resources will be available for LTE technology.

In the example in Fig. 5, three base stations are shown, two of which belong to group B (B1 and B2), and one to group A (A1). Each station forms three cells, B1 forms cells 1, 2, 3; A1 forms cells 4, 5, 6;
B2 – 7, 8, 9. Then cells 1-3 and 7-9 can be assigned channels from the third frequency band. Since there are 7 GSM channels in the third frequency band, and there are only 6 cells, different GSM channels from the third frequency band can be assigned to the cells. At the same time, a resource of 64 PRB for LTE technology will be available for cells 1-3 and 7-9. Cells 4-6 will be assigned different GSM channels from the first band containing 5 GSM channels. For cells 4-6, a resource of 67 PRB will be available for LTE technology.

Thus, both neighboring cells of one base station and cells of nearby base stations (belonging to base stations of different groups) have enough channels to assign in such a way as to overcome the problem of interference of signals from neighboring cells and provide GSM coverage of adequate quality.

Base stations send radio signals into space. At the same time, radio signals contain not only the user traffic itself, but also service information, including information on what frequencies the base station exchanges radio signals in a given cell.

The mobile station measures the power level of the received radio signals from the base stations and connects (begins exchanging radio signals) to the base station with the highest signal strength. If the mobile station is located in a cell of the base station of group A, then the radio signal from such a station will have the highest signal strength and the mobile station will begin to exchange radio signals with this base station. The mobile station receives a radio signal containing service information about which GSM channel or channels are used for exchanging radio signals using GSM technology and which frequencies are used for exchanging radio signals using LTE technology in the cell. If the mobile station is located in a cell of the base station of group B, then the signal level from this station will be the highest and similarly the mobile station will receive a radio signal containing service information about which GSM channel or channels are used for exchanging radio signals using GSM technology and which frequencies are used to exchange radio signals using LTE technology in the cell, and will begin to exchange radio signals with the base station.

As shown above, by implementing this communication method, the number of PRBs that can be used for LTE technology increases, while leaving for GSM technology a sufficient number of channels to provide GSM coverage of adequate quality. With the new method of frequency-territorial planning, the threshold of 60% of a blocked resource is achieved when the number of GSM channels exceeds 27, and for 18 GSM channels only 30% of the resource will be blocked (Fig. 8).

This method was implemented in Blagoveshchensk (Fig. 9, where the blue points are BS with configuration A, and the red points are BS with configuration B). The increase in LTE speed was +40% while maintaining the quality of voice service.

Claims (7)

1. A method for distributing cellular network resources between GSM and LTE technologies, in which the allocated radio frequency spectrum includes a working frequency spectrum and guard intervals at the edges of the working spectrum, characterized in that the working spectrum is divided into the first, second and third frequency bands, and the second frequency band is located between the first and third, and all base stations of the cellular network are divided into two groups, where the base stations of the first group are configured to exchange radio signals with mobile stations using the frequencies of the first frequency band and guard intervals for GSM technology, the frequencies of the second and third frequency bands for LTE technology; and the base stations of the second group - using the frequencies of the third frequency band and guard intervals for GSM technology, the frequencies of the second and first frequency bands for LTE technology; Moreover, the base stations closest to each other belong to different groups, and the neighboring cells formed by the base stations do not use the same frequencies for GSM technology. 2. A system of base stations of a cellular communication network, characterized in that it consists of the first and second groups of base stations, configured to form cells and exchange radio signals with mobile stations at a given frequency in each cell formed by them and using radio frequency to exchange radio signals with mobile stations spectrum, including the operating frequency spectrum and guard intervals at the edges of the operating spectrum, and the operating spectrum is divided into the first, third and second frequency bands located between them, and the base stations closest to each other belong to different groups, and in neighboring cells the same frequencies are not used for GSM technology, wherein the base stations of the first group are configured to exchange radio signals with mobile stations using the frequencies of the first frequency band and guard intervals for GSM technology, the frequencies of the second and third frequency bands for LTE technology; and the base stations of the second group - using the frequencies of the third frequency band and guard intervals for GSM technology, the frequencies of the second and first frequency bands for LTE technology.