KR101319626B1 - Mobile telecommunication system and method for transmitting forward link control information - Google Patents

Abstract

The present invention relates to a method and a mobile communication system for transmitting information on the number of symbols for downlink control information transmission to a terminal. The method and mobile communication system sets and transmits a Control Format Indicator (CFI) update period and a downlink frame length for transmission of control information, and divides and transmits a PCFICH signal including the CFI into the CFI update period. A base station transmitting control information; And receiving the CFI update period, the downlink frame length, and the PCFICH signal divided into the CFI update period, and merging the divided PCFICH signal into the CFI update period to obtain CFI information, wherein the CFI information and the downlink frame are obtained. And a terminal for demodulating / decoding the control information using a length.

Downlink Control Information, CFI, Downlink Frame

Description

Downlink control information transmission method and mobile communication system {MOBILE TELECOMMUNICATION SYSTEM AND METHOD FOR TRANSMITTING FORWARD LINK CONTROL INFORMATION}

The present invention relates to a mobile communication system, and more particularly, to a method and a mobile communication system for transmitting information on the number of symbols for downlink control information transmission to the terminal.

Unlike third generation mobile communication systems using code division multiple access (CDMA), most fourth generation mobile communication systems use Orthogonal Frequency Division Multplexing (OFDM). In the system using the OFDM scheme, some OFDM symbols are allocated for transmission of control information in order to transmit control information to the terminal, and the control information is transmitted. The control information includes uplink / downlink resource allocation information and uplink power. Control information, ACK / NACK information for uplink reception data, and the like are included. In addition, information (CFI; Control Format Indicator) on how many OFDM symbols to allocate for transmission of control information should also be transmitted to the UE every TTI. In the fourth generation mobile communication system, a channel for transmitting such CFI information to the UE for control information transmission is called a physical control format indicator channel (PCFICH), and the number of OFDM symbols allocated per TTI is 20 or less. About 20-40% of symbols are used for control information transmission. Typically, information bits of the CFI that transmit the number of symbols for control information transmission are about 2 bits or 3 bits, and subcarriers within 5% are mainly used for CFI transmission.

The number of symbols for transmission of control information can be changed for each TTI depending on how much control information the base station needs to send to each terminal to which the call is connected per TTI. If the UE fails to acquire the CFI, the base station cannot sufficiently decode / demodulate all the traffic information transmitted to the TTI. The PCFICH signal should be sent at high power.

However, since the PCFICH signal uses radio resources overlapping with reference acquisition signals (RSs) used by neighboring base stations, the PCFICH signal is received from a base station that is currently connected to and receives a service using a reference signal transmitted from the base station. In measuring the signal quality (Signal to Interference and Noise Ratio, SINR) and the quality of the signal received from the neighboring base station, it is a major cause of deterioration of accuracy.

In particular, the UE at the cell boundary has a significant influence of PCFICH in measuring downlink SINR, which may seriously degrade downlink data transmission efficiency.

The present invention provides a method and a mobile communication system for transmitting information on the number of symbols for downlink control information transmission to the terminal.

 The mobile communication system according to the present invention sets and transmits a Control Format Indicator (CFI) update period and a downlink frame length, and divides and transmits a PCFICH signal including the CFI into the CFI update period. A base station transmitting control information; And receiving the CFI update period, the downlink frame length, and the PCFICH signal divided into the CFI update period, and merging the divided PCFICH signal into the CFI update period to obtain CFI information, wherein the CFI information and the downlink frame are obtained. And a terminal for demodulating / decoding the control information using a length.

The method for transmitting downlink control information according to the present invention includes: a) setting and transmitting a control format indicator (CFI) update period and a downlink frame length for transmitting control information; b) dividing and transmitting a PCFICH signal including CFI information into the CFI update period; c) acquiring the CFI information by merging the divided PCFICH signals into the CFI update period; And d) demodulating / decoding the control information using the CFI information.

According to the present invention, the transmission power of a PCFICH (Physical Control Format Indicator Channel) signal for transmitting a Control Format Indicator (CFI) can be optimized according to an operator's operation strategy, network configuration type, and service status.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the scope of the present invention is not limited to the following preferred embodiments.

The number of symbols for control information transmission may change for each TTI depending on how much control information the base station needs to transmit to each terminal to which the call is connected per TTI. In addition, if the UE fails to acquire the CFI, the base station cannot decode / demodulate all traffic information delivered to the TTI so that the base station has a high output power so that all UEs in the cell can successfully acquire the CFI. PCFICH signal should be sent. However, when the transmission power of the PCFICH increases, the signal to interference and noise ratio (SINR) received from the base station decreases. The transmission power and SINR of such PCFICH should be adjusted efficiently.

The most intuitive approach to reduce the transmission power of the PCFICH is to obtain a channel coding gain by lowering the coding rate of the PCFICH, and there is a method of increasing the update period of the CFI to lower the coding rate of the PCFICH. By increasing the CFI update period, degradation of SINR can be minimized. That is, according to the present invention, the system operator can use only the minimum radio resources necessary for transmitting the CFI information according to cell characteristics for each base station, and thus can improve the performance of the mobile communication system by reducing inter-cell interference.

1 is a flowchart showing a procedure of a method for transmitting downlink control information according to an embodiment of the present invention, and FIG. 2 is an exemplary view showing a structure of a downlink frame according to an embodiment of the present invention.

First, the base station sets an optimal CFI update period (eg, M TTIs) and a downlink frame length (eg, N TTIs) (S110). The base station manages a plurality of cells, and the optimal CFI update period is determined by the number of terminals connected to a specific cell and the type of service the terminal receives. For example, a cell having a large cell radius and a small number of access terminals may use only one or two symbols per TTI for transmitting control information, and there is no need to change the CFI every TTI. However, in the case of a very large number of access terminals in a cell and the types of services each terminal receives, it may be more desirable to change the CFI frequently according to circumstances. The base station may set the downlink frame length to an integer multiple of the CFI update period. The base station transmits the CFI update period and the downlink frame length set through the broadcast channel (S120). The base station divides and transmits the PCFICH signal including the control information and the CFI into a CFI update period.

The terminal receives the PCFICH signal divided into the CFI update period (S130). The received PCFICH signal is merged using the CFI update period received from the base station (S140). The terminal obtains CFI information from the merged PCFICH signal (S150). The UE knowing the downlink frame length performs demodulation and decoding of control information to be used during the next CFI update period (an integer multiple of the CFI update period M) using the obtained CFI information (S160). The terminal transmits and receives downlink / uplink data through demodulated and decoded control information.

In the case of a terminal using a standard different from the above-described standard of the present invention, since the CFI update period transmitted through the broadcast channel is not used, a transmission scheme as shown in FIG. 2 may be used to maintain compatibility. For example, the total number of TTIs included in the downlink frame from the first TTI of the downlink frame composed of 10 TTIs, except for the number of TTIs (for example, N TTIs) representing the downlink frame length, that is, during the 10-N TTI The PCFICH signal is transmitted with the same transmission power as the conventional method. However, during the N TTIs of the downlink frame, the PCFICH signal is transmitted by the method proposed by the present invention. In the present embodiment, the downlink frame length to which the method of the present invention is not applied is 2 TTI, and the downlink frame length N to which the method of the present invention is applied is 8 TTI, the CFI update period M is 4, and the length of the total downlink frame. Assume that 10 consists of 10 TTIs. From N + 2 TTI to N + 5 TTI, the same PCFICH signal is transmitted at a low transmission power (previous 25%) coding rate. That is, as shown in FIG. 2, when the power of the PCFICH signal per TTI is A, according to the embodiment of the present invention, since the CFI update period M is 4, the power of the PCFICH signal per TTI is reduced to A / 4. . The UE detects the CFI by merging the PCFICH signals received during the corresponding M TTI. The detected CFI is used to perform demodulation and decoding of control information during the next M TTI (n + 6 TTI to n + 9 TTI).

In the present embodiment, the downlink frame length (N) may be determined by an integer multiple of the CFI update period (M) to improve the convenience of operation, the downlink frame length N is the number of terminals connected in the cell, the terminal is provided It is desirable to determine a combination with the CFI update period M according to the variety of service types and the percentage of terminals that do not support the present invention in the cell. In addition, since a UE that does not support the present invention cannot receive downlink data service because CFI demodulation and decoding are not performed during N TTI, there are more UEs that do not support the present invention than a UE supporting the present invention in a cell. It is necessary to minimize the downlink data service degradation of the existing terminal by using a value of N less than 5. In addition, when the number of terminals supporting the present invention increases, the N value can be increased as well, and as N increases, interference to neighboring cells can decrease.

While the above methods have been described through specific embodiments, the methods may also be implemented as computer readable code on a computer readable recording medium. A computer-readable recording medium includes all kinds of recording apparatuses in which data that can be read by a computer system is stored. Examples of the computer-readable recording medium include a ROM, a RAM, a CD-ROM, a magnetic tape, a floppy disk, an optical data storage device, and the like, and may be implemented in the form of a carrier wave (for example, transmission over the Internet) . In addition, the computer-readable recording medium may be distributed over network-connected computer systems so that computer readable codes can be stored and executed in a distributed manner. In addition, functional programs, codes, and code segments for implementing the above embodiments can be easily deduced by programmers of the present invention.

While the invention has been described in connection with certain embodiments thereof, it will be apparent to those skilled in the art that various modifications and variations can be made therein without departing from the spirit and scope of the invention . It is also contemplated that such variations and modifications are within the scope of the claims appended hereto.

1 is a flowchart illustrating a procedure of a method for transmitting downlink control information according to an embodiment of the present invention.

2 is an exemplary view showing a structure of a downlink frame according to an embodiment of the present invention.

Claims (8)

In the mobile communication system, A base station for setting and transmitting a Control Format Indicator (CFI) update period and a downlink frame length for transmitting control information, dividing and transmitting a PCFICH signal including the CFI into the CFI update period, and transmitting control information; And Receives a PCFICH signal divided into the CFI update period, the downlink frame length and the CFI update period, and merges the divided PCFICH signal into the CFI update period to obtain CFI information, and the CFI information and the downlink frame length A mobile communication system comprising a terminal for demodulating / decoding the control information by using. The method of claim 1, The CFI update period and the downlink frame length is transmitted from the base station to the terminal using a broadcast channel. 3. The method of claim 2, The CFI update period and the downlink frame length is determined according to the number of terminals connected to a specific cell among a plurality of cells managed by the base station and the service type of each terminal. The method of claim 3, The downlink frame length is a mobile communication system, characterized in that the integer multiple of the CFI update period. As a downlink control information transmission method, a) setting and transmitting a Control Format Indicator (CFI) update period and a downlink frame length for transmitting control information; b) dividing and transmitting a PCFICH signal including CFI information into the CFI update period; c) acquiring the CFI information by merging the divided PCFICH signals into the CFI update period; And d) demodulating / decoding the control information using the CFI information. The method of claim 5, The CFI update period and the downlink frame length is transmitted using a broadcast channel. The method according to claim 6, The CFI update period and the downlink frame length is determined according to the number of terminals connected to a specific cell among a plurality of cells managed by the base station and the service type of each terminal. The method of claim 7, wherein The downlink frame length is an integer multiple of the CFI update period, downlink control information transmission method.

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