KR20180036911A - Method and apparatus for detecting event using image information analysis - Google Patents

Abstract

A method for controlling a subcarrier interval is provided. The method includes a step of selecting a subcarrier interval in the intersection of a first subcarrier interval set including a subcarrier interval smaller than a channel correlation bandwidth and a second subcarrier interval set including a subcarrier interval larger than the reciprocal of a channel correlation time; a step of transmitting the control information of the selected subcarrier interval to a terminal; and a step of transmitting and receiving data according to the selected subcarrier interval.

Description

Field of the Invention [0001] The present invention relates to a method and an apparatus for controlling a sub-

The present disclosure relates to a method and apparatus for controlling the subcarrier spacing of a multi-carrier system.

In a multi-carrier-based wireless communication system, a signal carrying information is transmitted through a plurality of subcarriers, so that delay spread in the time domain and frequency selective fading in the frequency domain ) Can be overcome. Multicarrier technology also enables high-speed broadband transmission of data in a wireless environment.

As an example of a multi-carrier-based wireless transmission scheme, there is an orthogonal frequency-division multiplexing (OFDM) transmission scheme. In OFDM, each subcarrier maintains orthogonality in the frequency domain and is used for data transmission without Inter-Carrier Interference (ICI). However, orthogonality between subcarriers may be broken due to various radio channel environment characteristics and performance limitations of the transceiver. There are time and frequency synchronization errors, Doppler shift / spread, phase noise, and the like, which cause the orthogonality between subcarriers to be disturbed and generate ICI.

One embodiment provides a method of controlling the subcarrier spacing of a multi-carrier system.

Selecting a subcarrier interval in an intersection of a first subcarrier interval set including a subcarrier interval smaller than the channel correlation bandwidth and a second subcarrier interval set including a subcarrier interval larger than a reciprocal of the channel correlation time; And transmitting and receiving data according to the selected subcarrier interval. The subcarrier interval control method includes the steps of:

The base station of the multi-carrier system can reduce the error rate of the signal and improve the data transmission efficiency by controlling the subcarrier interval.

1 is a flowchart illustrating a method of controlling a subcarrier interval according to an exemplary embodiment of the present invention.
2 is a block diagram illustrating a wireless communication system according to an embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present disclosure can be embodied in various different forms and is not limited to the embodiments described herein. In order to clearly illustrate the present invention in the drawings, parts not related to the description are omitted, and like reference numerals are given to similar parts throughout the specification.

Throughout the specification, a terminal is referred to as a mobile station (MS), a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE), a machine type communication device MTC device and the like and may include all or some functions of MT, MS, AMS, HR-MS, SS, PSS, AT, UE,

Also, a base station (BS) is an advanced base station (ABS), a high reliability base station (HR-BS), a node B, an evolved node B, eNodeB), an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) (RS), a relay node (RN) serving as a base station, an advanced relay station (ARS) serving as a base station, a high reliability relay station (HR) (BS), a home Node B (HNB), a home eNodeB (HeNB), a pico BS, a macro BS, a micro BS ), Etc., and all or all of ABS, Node B, eNodeB, AP, RAS, BTS, MMR-BS, RS, RN, ARS, HR- And may include negative functionality.

1 is a flowchart illustrating a method of controlling a subcarrier interval according to an exemplary embodiment of the present invention.

The OFDM parameters related to the OFDM transmission performance include a subcarrier spacing, a size of a fast Fourier transform (FFT), a channel bandwidth, a carrier frequency, a cyclic prefix (CP) And the like. Properly changing the double subcarrier spacing allows the OFDM signal to be transmitted without ICI. In this case, the subcarrier interval should be smaller than the coherence bandwidth of the channel in the frequency domain. In order not to generate the ICI, the length of the OFDM symbol must be shorter than the coherence time of the channel, which can be adjusted through control of the subcarrier interval in view of the inverse relationship of the length of the OFDM symbol in the time domain . Also, a large sub-carrier spacing should be used as the frequency selectivity of the channel is high because a large number of the reflected waves are present, and a larger sub-carrier spacing should be used as the channel time selectivity is increased due to the high-speed movement of the UE. In addition to the channel characteristics, the use of a wide subcarrier spacing in which the ICI is relatively small is advantageous because the number of subcarriers used is small when a large number of phase noise occur in the transceiver. In the conventional OFDM system, since the subcarrier interval is fixed, it is difficult to adaptively adapt to the channel variation and transmission / reception performance difference per user, and the block error rate (BLER) and the spectrum efficiency are inevitably low.

A sub-carrier interval control method according to an exemplary embodiment of the present invention includes not only an OFDM system but also a windowed-OFDM system, a filtered-OFDM system, a filter-bank multi-carrier (FBMC) System, a generalized frequency division multiplexing (GFDM) system, and the like. The above-mentioned multicarrier system includes a guard period in the time domain, and the guard interval includes a cyclic prefix, a cyclic postfix, a null guard period, and the like. According to one embodiment, a guard band may be disposed at the edge of a bandwidth in a frequency region of a multicarrier, and a DC subcarrier may be disposed at a center of the bandwidth.

According to an embodiment, when a sub-carrier is arranged in information data, a data channel, a broadcast channel, a control channel, a reference signal, signal, a synchronization signal, and the like can be multiplexed. According to one embodiment, the encoding and decoding of the information data may be performed by a convolutional code, a turbo code, a low-density parity-check (LDPC) code, or a polar code . According to one embodiment, modulation and demodulation of the signal may be performed based on quadrature phase shift keying (QPSK), quadrature amplitude modulation (QAM), 64QAM, 256QAM, and the like.

Meanwhile, the number of candidate subcarriers according to an embodiment may be two or more, the subcarrier interval may be an exponential multiple of 2, and may be a multiple of 15kHz. For example, the subcarrier set may be {15, 30, 60, 120, 240, 480} kHz.

A base station according to an embodiment determines a subcarrier interval and transmits / receives a signal according to a determined subcarrier interval. For example, the base station may receive information for determining the subcarrier interval from the terminal, and may determine the subcarrier interval, the FFT size, the length of the OFDM symbol, the CP length, and the like. Referring to FIG. 1, a BS collects information for determining a subcarrier interval from a terminal (S110). According to one embodiment, the information used to control the subcarrier spacing may include channel delay spread, channel coherence bandwidth, channel Doppler shift / spread, channel correlation Time (channel coherence time), terminal movement speed, terminal phase noise power density, and the like. Also, the base station can receive BLER, signal to interference plus noise ratio (SINR), interference power level, and the like from the mobile station in order to control the subcarrier interval.

According to one embodiment, the base station may determine the subcarrier spacing among the candidate subcarrier spacing values less than the channel correlation bandwidth. Equation 1 represents a subset X of subcarrier spacings to be selected based on the channel correlation bandwidth.

Referring to Equation (1), A is a subcarrier set and _Wc is a channel correlation bandwidth.

According to another embodiment, the base station can determine the subcarrier spacing among the candidate subcarrier spacing values that are larger than the reciprocal of the channel correlation time. Equation (2) represents a subset Y of subcarrier intervals to be selected based on the channel correlation time.

According to yet another embodiment, the base station selects a subcarrier interval at intersection Z (Z = X? Y) of subset X according to equation (1) and subset Y according to equation (S110). If the selected sub-carrier interval is different from the previously used sub-carrier interval and the sub-carrier interval needs to be changed, the base station transmits control information of the selected sub-carrier interval to the terminal (S120). The sub-carrier interval control of the base station according to an embodiment may be performed in a dynamic or semi-persistent manner. The base station can transmit the control information of the subcarrier interval to the terminal through a broadcast channel, a control channel, or an upper control message. After receiving the control information of the subcarrier interval from the base station, the UE can change the subcarrier interval, the FFT size, the CP length, and the like simultaneously after a predetermined time.

Meanwhile, the base station may determine the minimum value among the sub-carrier intervals included in the subset Z, or may determine the median as the sub-carrier interval, or may determine the maximum value as the sub-carrier interval. When the carrier frequency is relatively large, the base station can determine a value close to the maximum value of the subset Z at the subcarrier interval. And, when the carrier frequency is relatively small, the base station can determine the subcarrier interval to a value close to the minimum of the subset Z. [

When the terminal phase noise density is large, the base station can determine a value close to the maximum value of the subset Z at the subcarrier interval. When the terminal phase noise density is small, the base station can determine the subcarrier interval with a value close to the minimum value of the subset Z. [

The base station can transmit / receive data to / from the terminal after the information about the sub-carrier interval is shared with the terminal (S130).

When the subcarrier interval control of the base station according to an embodiment is performed in a dynamic or semi-persistent manner, the base station can instruct the terminal to change the subcarrier interval (S140). At this time, the control information of the subcarrier interval may include an instruction indicating a step of the subcarrier interval. At this time, the step of the subcarrier interval may be predetermined, and the instruction may instruct the step of the subcarrier interval to be lowered or increased by a predetermined number. For example, if the BLER or interference power value is greater than a predetermined threshold, or if the SINR is less than a predetermined threshold, then the base station may instruct the instruction to increment or decrement the subcarrier interval by one. Or if the BLER or interference power value increases or the SINR decreases after a change in the subcarrier interval, the instruction may instruct to return the subcarrier interval back to before the change. Alternatively, if the BLER or interference power value decreases or the SINR increases after a change in the subcarrier interval, the instruction may indicate one more step or one step decrease in the subcarrier interval. Or if the amount of change in the BLER, or the interference power value, or the SINR, after a change in the subcarrier interval is less than or equal to the predetermined level?, The command may indicate an interruption of the subcarrier interval change. At this time, the control period of the subcarrier interval may be constant or not constant. Thereafter, the base station can transmit / receive data to / from the terminal according to the changed subcarrier interval (S150).

As described above, the base station of the multi-carrier system can reduce the error rate of the signal and improve the data transmission efficiency by controlling the subcarrier interval.

2 is a block diagram illustrating a wireless communication system according to an embodiment.

Referring to FIG. 2, a wireless communication system according to an embodiment includes a base station 210 and a terminal 220.

The base station 210 includes a processor 211, a memory 212, and a radio frequency unit (RF unit) 213. The memory 212 may be coupled to the processor 211 to store various information for driving the processor 211 or at least one program to be executed by the processor 211. [ The wireless communication unit 213 is connected to the processor 211 to transmit and receive a wireless signal. The processor 211 may implement the functions, processes, or methods proposed in the embodiments of the present disclosure. At this time, in the wireless communication system according to an embodiment of the present invention, the wireless interface protocol layer may be implemented by the processor 211. [ The operation of the base station 210 according to one embodiment may be implemented by the processor 211. [

The terminal 220 includes a processor 221, a memory 222, and a wireless communication unit 223. The memory 222 may be coupled to the processor 221 to store various information for driving the processor 221 or at least one program executed by the processor 221. [ The wireless communication unit 223 is connected to the processor 221 and can transmit and receive wireless signals. The processor 221 may implement the functions, steps, or methods suggested in the embodiments of the present disclosure. At this time, in the wireless communication system according to an embodiment of the present invention, the wireless interface protocol layer can be implemented by the processor 221. The operation of the terminal 220 according to one embodiment may be implemented by the processor 221. [

In an embodiment of the present disclosure, the memory may be located inside or outside the processor, and the memory may be connected to the processor through various means already known. The memory may be any type of volatile or nonvolatile storage medium, e.g., the memory may include read-only memory (ROM) or random access memory (RAM).

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (1)

A method for controlling subcarrier spacing,
Selecting a subcarrier interval in an intersection of a first subcarrier interval set including a subcarrier interval smaller than a channel correlation bandwidth and a second subcarrier interval set including a subcarrier interval larger than a reciprocal of a channel correlation time;
Transmitting control information of the selected sub-carrier interval to the terminal, and
Transmitting and receiving data according to the selected sub-carrier interval
/ RTI >

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