KR100692654B1 - Network system using frequency converted through multistage - Google Patents

Abstract

The present invention relates to a CDMA mobile communication system, and more particularly, to a relay system that expands cell coverage and prevents oscillation by enabling a frequency conversion repeater in multiple stages in a CDMA mobile communication system. Multi-stage frequency conversion consisting of a frequency conversion repeater for transmitting an output signal through a base station in charge of mobile communication to a reference frequency channel and an output frequency channel converting the input frequency channel into a channel different from the input frequency channel of the received input signal It relates to a relay system. According to the multi-stage frequency conversion relay system according to the present invention, oscillation in the repeater can be prevented by changing the input frequency and the output frequency of the repeater.

Multistage Frequency Conversion Relay System, Frequency Conversion, Handoff, Cell Coverage, Oscillation

Description

Multi-stage frequency conversion relay system {Network system using frequency converted through multistage}             

1A and 1B are exemplary views illustrating a mobile communication relay system for preventing oscillation according to the prior art.

2 is a block diagram of a frequency conversion relay system in a mobile communication system according to the present invention;

3 is a block diagram of a multi-stage frequency conversion relay system according to a preferred embodiment of the present invention.

Figure 4 is an exemplary frequency allocation for each frequency conversion repeater in a multi-stage frequency conversion relay system according to a preferred embodiment of the present invention.

Figure 5 is a block diagram of a multi-stage frequency conversion relay system according to another embodiment of the present invention.

6 is an exemplary diagram of frequency allocation for each frequency conversion repeater in a multi-stage frequency conversion relay system according to a preferred embodiment of the present invention.

7 is an explanatory diagram showing a general compressed mode transmission structure.

<Explanation of symbols for the main parts of the drawings>

200, 230, 300, 301, 302, 303, 304, 500, 501, 502, 503, 504 mobile stations

210, 310, 510: base station

220, 321, 322, 323, 324, 521, 522, 523, 524,: frequency conversion repeater

710: normal frame

720: compressed frame

The present invention relates to a CDMA mobile communication system, and more particularly, to a relay system that expands cell coverage and prevents oscillation by enabling a frequency conversion repeater in multiple stages in a CDMA mobile communication system.

Mobile communication repeaters are widely used to economically extend coverage in mobile communication networks. The mobile communication repeater receives the weak base station signal from the base station through the base station counter antenna using the aerial line, amplifies the received signal and transmits the signal to the mobile station through the mobile station counter antenna. In addition, the repeater receives a signal from the mobile station through the mobile station facing antenna, amplifies the received signal and transmits the signal to the base station through the base station facing antenna.

The mobile communication relay system according to the prior art includes a base station, a mobile station for wireless communication with the base station, and a mobile communication repeater for receiving and amplifying a signal from the base station or the mobile station and transmitting the signal to the mobile station or the base station. Here, the mobile communication repeater includes a base station facing antenna and a mobile station facing antenna, and the base station facing antenna and the mobile station facing antenna are both transmitting and receiving antennas.

The mobile communication repeater according to the prior art includes a base station counter antenna, a first duplexer, a forward signal processor, a second duplexer, a mobile station counter antenna, and a reverse signal processor. Here, the base station facing antenna and the mobile station facing antenna are combined transmitting and receiving antennas. The base station facing antenna of the mobile communication repeater receives a signal from the base station by the first duplexer, and the forward signal processor outputs the received signal to the second duplexer through filtering, frequency conversion, and amplification. The second duplexer transmits the signal whose transmission strength is converted to the mobile station through the mobile station facing antenna. On the other hand, the mobile communication repeater receives a signal from the mobile station by the second duplexer through the mobile station facing antenna, the reverse signal processor outputs the received signal to the first duplexer through the process of filtering, frequency conversion and amplification. The first duplexer transmits a signal input from the reverse signal processor to the base station through the base station opposing antenna.

In the mobile communication repeater according to the related art, which is configured and operated as described above, a forward link for transmitting a signal from the base station to the mobile station and a reverse link for transmitting a signal from the mobile station to the base station exist simultaneously. That is, the signal transmitted to the mobile station through the mobile station opposing antenna is partially returned to the base station opposing antenna, and the signal transmitted to the base station via the base station opposing antenna is partially returned to the mobile station opposing antenna. At this time, the signal output through the mobile station counter antenna or the base station counter antenna is increased due to the transmitted signal, thereby repeating the process of bringing back the increased input. Accordingly, the forward signal processor or the reverse signal processor in the mobile communication repeater emits noise corresponding to the maximum value of the amplified output, which is called oscillation. This noise is transmitted to the base station, which has a fatal effect on the quality of mobile communication, and in severe cases, causes the base station to fail.

Therefore, the repeater used to expand the cell coverage of the base station in the mobile communication system has an oscillation problem, and thus there are many limitations in extending the coverage. Due to the oscillation problem, it is impossible to use high output power, and it is necessary to arrange an additional circuit to prevent oscillation or to secure an isolation. In addition, even if the oscillation problem is solved in any environment, there is a high probability that another oscillation problem may occur in another environment.

1A and 1B are exemplary views illustrating a mobile communication relay system for preventing oscillation according to the prior art. Referring to FIG. 1A, in the case of a general RF repeater, since an input frequency and an output frequency are the same, there is always a risk of oscillation. In order to prevent this, there is a donor unit (DU), which converts a reference frequency f1 of the mobile communication base station into a conversion frequency f2 and transmits it to a remote unit (RU). In addition, the RU converts the received frequency f2 back to the frequency f1 for talking with the terminal. As another method, as illustrated in FIG. 1B, an input cancellation signal and an output signal may be compared and analyzed using an ICS (Interference Cancellation System) repeater to remove the oscillation component.

However, the methods shown in FIGS. 1A and 1B require additional new devices, which adds cost and require additional management, and thus are not fundamental measures for solving the oscillation problem in the repeater.

Accordingly, in order to solve the above problems, it is an object of the present invention to provide a multi-stage frequency conversion relay system capable of preventing oscillation in a repeater by changing the input frequency and the output frequency of the repeater.

Another object of the present invention is to provide a multi-stage frequency conversion relay system to significantly expand the cell coverage of a base station in a mobile communication system.

It is still another object of the present invention to provide a multi-stage frequency conversion relay system capable of preventing oscillation in a repeater even without the use of an essential DU (main relay) in the existing band conversion relay equipment.

In order to achieve the above objects, according to an aspect of the present invention, an output frequency channel obtained by converting the input frequency channel into a channel different from a base station in charge of mobile communication to a reference frequency channel and an input frequency channel of a received input signal. A frequency conversion repeater for outputting an output signal through a channel, wherein the input frequency channel and the output frequency channel are in the same frequency allocation band, wherein the frequency conversion repeater has n (n ≧ 2), The input frequency channel of the frequency conversion repeater of the is the reference frequency channel of the signal received from the base station, the output frequency channel of the frequency conversion repeater of the preceding step is the input frequency channel of the frequency conversion repeater of the subsequent stage, the base station Communicates with the mobile terminal through the reference frequency channel. Wherein the frequency translating repeater provides a multi-stage frequency conversion relay system, characterized by the communication with the mobile terminal via the frequency output channel it is possible.

Preferably, the reference frequency channel of the base station and the output frequency channel of the even stage of the frequency conversion repeater may be the same, and the output frequency channel of the odd stage of the frequency conversion repeater may be the same.

Also preferably, the communication between the base station and the frequency conversion repeater and the mobile communication terminal may be characterized by using a hard handoff, the hard handoff may use a compression mode, the hard handoff is NCHO (Network Controlled Handoff), Mobile Assisted Handoff (MAHO) or Mobile Controlled Handoff (MCHO), and the mobile communication terminal is the reference frequency of the base station. It may include two transceivers that are tuned independently of each other on the channel or on the output frequency channel of the frequency conversion repeater.

Other objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a configuration diagram of a frequency conversion relay system in a mobile communication system according to the present invention. Referring to Figure 2, the frequency conversion relay system is composed of a base station 210 and the frequency conversion repeater 220. It may also include mobile stations 200 and 230 for communicating.

Base station 210 is responsible for one cell for mobile communication. That is, it means one radio station in charge of mobile service.

The frequency conversion repeater 220 receives an input signal from the base station 210 to the reference frequency channel FA1 through the base station facing antenna. And converts to a converted frequency channel FA2, which is another channel in the same frequency allocation band as the reference frequency channel FA1, and transmits an output signal to the converted frequency channel FA2 to the mobile station 230 through the mobile station facing antenna. The mobile station 230 receives an input signal from the mobile station 230 through the converted frequency channel FA2, converts the frequency into a reference frequency channel FA1, which is a frequency that can communicate with the base station 210, and then converts the received signal into the base station 210 through the base station opposed antenna. To send.

Here, the frequency band allocation for the mobile communication service is in charge of the national agency for the fair distribution and management of frequency resources. In Korea, the Tx band is 869 ~ 894MHz, the Rx band is 824-849MHz, and in the case of PCS, the Tx band is 1840-1870MHz and the Rx band is 1750-1780MHz. In each of the allocated frequency bands, there are 18 channels of 1.23 MHz intervals for cellular and 21 channels of 1.25 MHz intervals for cellular. In addition to the above-mentioned Korean standards in frequency band allocation or frequency channel spacing of the present invention, many modifications are possible by those skilled in the art within the spirit of the present invention. In addition, the conversion from the FA1 of the reference frequency channel to the FA2 of the converted frequency channel means that the channel is converted from the frequency channel including the FA1 to the frequency channel including the FA2 in the same cellular system or within the same personal mobile communication system. It is.

Here, since the frequency channel of the signal transmitted and received by the base station opposing antenna and the frequency channel of the signal transmitted and received by the mobile station opposing antenna in the frequency conversion repeater 220 are different from FA1 and FA2, respectively, the oscillation which was important in the system including the conventional repeater Problems can be solved at source.

Using the above-described principle, if the frequency of the signal transmitted and received by the base station facing antenna in the repeater and the frequency of the signal transmitted and received in the mobile station facing antenna are different, the oscillation problem no longer occurs. It is possible to enlarge.

3 is a block diagram of a multi-stage frequency conversion relay system according to an exemplary embodiment of the present invention. Referring to FIG. 3, the multi-stage frequency conversion relay system is composed of a base station 310 and frequency conversion repeaters 321, 322, 323,... 324 of n (n ≧ 1, natural numbers) stages.

There are n frequency-converted repeaters 321, 322, 323, ..., and 324, and the frequency-converted repeaters at each stage are different from the input frequency channels, which are frequencies of signals transmitted and received within the same frequency allocation band through base station facing antennas. An output frequency channel, which is a channel, is used as a frequency channel of a signal transmitted and received through a mobile station facing antenna.

Since the frequency conversion repeater 320 of the first stage receives a signal from the base station 310, the input frequency channel of the signal through the base station facing antenna is FA1, which is the reference frequency channel of the base station 310, and is within the same frequency allocation band as FA1. Converts the frequency channel of the signal through the mobile opposing antenna from the other channel to output frequency channel FA2. Then, the second stage of the frequency conversion repeater 322 receives the signal of the base station 310 from the frequency conversion repeater 320 of the first stage bar signals transmitted and received through the base station opposed antenna 320 of the first stage of the frequency conversion repeater 320 Through the signal. Thus, the input frequency channel of the frequency converter repeater 322 of the second stage becomes the output frequency channel FA2 of the frequency converter repeater 320 of the first stage. The second stage of the frequency conversion repeater 322 converts it again to form a frequency channel of the frequency channel FA3 is used as the frequency channel of the signal transmitted and received through the mobile station facing antenna of the frequency conversion repeater 322 of the second stage. This process is repeated so that the reference frequency channel FA (n-1) is converted into the converted frequency channel FA (n) in the nth frequency conversion repeater 326.

Here, each of the frequency conversion repeaters 321, 322, 323, ..., 324 can communicate with each mobile station 301, 302, 303, ..., 304 through the conversion frequency channel through the mobile station facing antenna. In addition, the cell coverage may be extended to zone 2 when the frequency conversion repeater is used as compared to the zone 1 of FIG. 3 because there is only one repeater.

4 is an exemplary diagram of frequency allocation for each frequency conversion repeater in a multi-stage frequency conversion relay system according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the frequency converter repeater # 1 321 includes a signal transmitted and received through a base station facing antenna and a signal transmitted and received through a mobile station facing antenna. Here, the frequency channel used by the signal transmitted and received through the base station facing antenna is called FA1. In the frequency conversion repeater # 1 321, the frequency channel used by the signal transmitted and received through the mobile station counter antenna is a channel converted from the frequency channel FA1 to FA2 within the same frequency band according to the above-described principle of the present invention. FA2 may be any channel other than FA1 within the same frequency band.

The frequency conversion repeater # 2 322 receives the signal from the frequency conversion repeater # 1 321 through the base station counter antenna, and thus the frequency channel used by the signal transmitted and received through the base station counter antenna becomes FA2. In the frequency conversion repeater # 2 322, when a signal is transmitted and received through the mobile station counter antenna again, the frequency channel FA2 of the signal transmitted and received through the base station counter antenna is converted to use the channel of FA3. Thereafter, the above-described process is repeated up to the frequency conversion repeater #n 324.

5 is a block diagram of a multi-stage frequency conversion relay system according to another embodiment of the present invention. Referring to FIG. 5, the multi-stage frequency conversion relay system includes a base station 510 and frequency conversion repeaters 521, 522, 523,... 524 of n (n ≧ 1) stages.

Almost the same as shown in FIG. 3, the difference is that only the frequency channels to convert in the frequency conversion repeater are FA1 and FA2. Instead of using n frequency channels as shown in FIG. 3, FA1 and FA2 are alternately used by utilizing a frequency reuse concept in which a frequency channel that has been used once can be reused again and again over a predetermined distance. In this way, the use of frequency channels, while extending coverage of the cells, uses only FA1 and FA2, maximizing the frequency spectrum efficiency, thereby increasing the subscriber capacity.

6 is an exemplary diagram of frequency allocation for each frequency conversion repeater in a multi-stage frequency conversion relay system according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the frequency channel conversion in frequency conversion repeater # 1 521 is the same as described above with reference to FIG. 4. That is, the reference frequency channel used by the signal transmitted and received through the base station facing antenna in the frequency converter repeater # 1 521 is FA1, and the converted frequency channel used by the signal transmitted and received through the mobile station facing antenna is FA2. The frequency converter repeater # 2 522 receives the signal from the frequency converter repeater # 1 521 through the base station opposing antenna, and the frequency channel used by the signal transmitted and received through the base station opposing antenna becomes FA2. In the frequency conversion repeater # 2 522, when a signal is transmitted and received through the mobile station facing antenna again, the frequency channel FA2, which is a frequency channel of the signal transmitted and received through the base station facing antenna, is converted. The channel of is used. This allows the use of only two channels of frequency channels, resulting in maximum frequency spectrum efficiency.

In order to operate the multi-stage frequency conversion relay system described above, there are requirements required for a base station, a frequency conversion repeater, and a mobile station. The mobile station performing the communication should perform the communication on the reference frequency channel within the range directly served by the base station, and the communication on the converted frequency channel within the range serviced by the frequency conversion repeater. When moving from the service coverage to the extended service coverage by the frequency conversion repeater, since the same frequency is not used between the base station and the repeater, the hard handoff should be possible so that the communication is not interrupted even when the frequency is changed during the communication.

In code division multiple access (CDMA) mobile communication systems, it is well known that all base stations of one operator can use the same frequency, so that soft handoff without frequency conversion is possible during handoff. Soft handoff is when the mobile station is at the boundary between the base stations, i.e., when it tries to enter the coverage of the neighboring base station out of the coverage of the home base station, using the same frequency without changing the talk frequency, While transmitting and receiving at the same time, when the signal sensitivity of the home base station falls below the reference value, the connection with the base station is disconnected and the call can be maintained through the remaining base stations. On the other hand, the hard handoff is a method of transmitting and receiving a new communication to the neighboring base station because the current base station and the neighboring base stations are different from each other and cannot transmit and receive simultaneously.

Using the soft handoff among the above-described handoffs enables the natural handoff by eliminating the simplistic phenomenon, which is a chronic problem in the analog system, and maintains a low call loss rate and high call quality.

However, from the viewpoint of the economics of the network design and the efficiency of the investment, different numbers of frequencies are allocated among adjacent base stations according to the call density, that is, the frequency of use among the adjacent base stations is different. Soft handoff cannot be applied when a mobile station that has used a specific talk frequency of the base station moves to an adjacent base station that does not have the same talk frequency. In such a case, hard handoff between frequencies should be performed.

There are three types of handoff control methods described above: Network Controlled Handoff (NCHO), Mobile Assisted Handoff (MAHO), and Mobile Controlled Handoff (MCHO). . NCHO is a method in which a network including a base station manages radio channel quality from a terminal. When the radio channel quality falls below a threshold and the handoff of the terminal is determined to be necessary, the network instructs the terminal to handoff. In the MAHO method, the UE measures the radio channel quality of the cell where the UE is currently located and the neighboring BS and periodically informs the BS of this, and the BS determines whether the UE needs handoff and handoffs to the UE when handoff is needed. Instructs off. Here, whether handoff is required is determined in consideration of radio channel quality, current and traffic conditions of neighboring base stations, and the like, when a handoff is required, the network node performs handoff. When the MCHO determines that handoff is necessary by measuring the quality of a radio channel, the UE attempts to perform a handoff, and a handoff request message is directly transmitted to a candidate base station. There is no need to inform the quality, which reduces the signal processing load and the handoff processing time is very short compared to other methods.

Therefore, the mobile station constituting the multi-stage frequency conversion relay system may be a mobile communication terminal capable of handoff by the above-described NCHO, MAHO or MCHO system.

In addition, a compression mode may be used to implement hard handoff in a multi-stage frequency conversion relay system.

7 is an explanatory diagram showing a general compressed mode transmission structure. Referring to FIG. 7, data transmission is not allowed during a transmission gap (hereinafter, referred to as 'TG') in the compressed frame 720. Instead, the transmission power in the slot region other than the TG period in the compressed frame 720 is higher than the power in the normal frame 710, thereby maintaining the same frame error probability as in the normal frame 710.

A mobile station having a single receiver structure using the compression mode illustrated in FIG. 7 is a new frequency channel when a frequency channel currently connected is called FA1 and a new frequency channel of an adjacent base station is FA2 in a handoff situation in the forward link. The signal strength of FA2 can be searched. That is, during the TG period, the frequency channel of the currently established FA1 is cut off and the frequency channel is changed to FA2 to measure the signal strength of the FA2. After the TG period, the FA1 frequency call channel can be demodulated again. The mobile station can monitor the new frequency channel FA2 of the forward link before completely blocking the current call setup in case of a handoff situation, and use the FA2 sync channel and common pilot channel to synchronize the forward link transmitted from the target base station. Acquisition can be avoided, even if the current call setup is disconnected and the hard handoff to the new frequency channel FA2 does not cause a disconnection of the forward link.

In addition, a dual receiver may be used to implement hard handoff in a mobile station constituting a multi-stage frequency conversion relay system.

The dual receiver includes a first antenna connected to a first transceiver and a second antenna connected to a second transceiver, and the first transceiver and the second transceiver are operable independently of each other with respect to transmission and reception. While the first transceiver is connected to the base station currently communicating through the first antenna at a reference frequency, the second transceiver may search for the frequency of the adjacent base station through the second antenna, and the strength of the signal at the base station currently communicating is When lowered below a certain value, it is possible to continue communication with a neighboring base station at a different frequency by using a second transceiver, thereby enabling hard handoff.

According to another preferred embodiment of the present invention, the above-described multistage frequency conversion system can be used in a marine vessel. When the base station located in the high ground of the land transmits the radio wave as the reference frequency channel FA1, the repeater located in the sea vessel receives the radio wave, converts the frequency channel to FA2 and amplifies the radio wave and transmits it to the terminal located in the vessel. In addition, it is possible to expand the cell coverage through the repeater from one vessel to another vessel. It can be used in the above-described method in mountainous areas or rivers that require a small number of calls but wide cell coverage.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, according to the multi-stage frequency conversion relay system according to the present invention, it is possible to prevent oscillation in the repeater by changing the input frequency and the output frequency of the repeater.

In addition, it is possible to significantly expand the cell coverage of the base station in the mobile communication system.

In addition, it is possible to prevent oscillation in the repeater even without the use of the DU (main relay), which is essential in the existing band conversion relay equipment.

In addition, there is no need to use expensive equipment using digital processing technology.

In addition, it is very effective when used in mountainous areas, rivers, seas, etc., where the number of calls is small and cell coverage is widely held.

Claims (6)

In the relay system, A base station responsible for mobile communication in a reference frequency channel; And A frequency conversion repeater for transmitting an output signal through an output frequency channel obtained by converting the input frequency channel to a channel different from an input frequency channel of a received input signal, wherein the input frequency channel and the output frequency channel are assigned the same frequency In-band, The frequency conversion repeater has n (n ≧ 2), and the input frequency channel of the frequency conversion repeater of one stage is the reference frequency channel of the signal received from the base station, and sequentially the output frequency of the frequency conversion repeater of the preceding stage. A channel is the input frequency channel of a subsequent frequency conversion repeater, the base station can communicate with the mobile communication terminal through the reference frequency channel, and the frequency conversion repeater can communicate with the mobile communication terminal through the output frequency channel. Multistage frequency conversion relay system, characterized in that. The method of claim 1, The reference frequency channel of the base station and the output frequency channel of the even stage of the frequency conversion repeater is the same, and the output frequency channel of the odd stage of the frequency conversion repeater is the same. The method according to claim 1 or 2, And the communication between the base station and the frequency translating repeater and the mobile communication terminal uses hard handoff. 4. The method of claim 3, wherein the hard handoff is Multistage frequency conversion relay system characterized in that the handoff using the compression mode. 4. The method of claim 3, wherein the hard handoff is Multi-stage frequency conversion relay system characterized by Network Controlled Handoff (NCHO), Mobile Assisted Handoff (MAHO) or Mobile Controlled Handoff (MCHO). The method of claim 3, wherein the mobile communication terminal And two transceivers tuned independently of each other to the reference frequency channel of the base station or the output frequency channel of the frequency conversion repeater.

Images