KR20160096499A - Method and apparatus for time resource allocation - Google Patents

Abstract

Provided are a method and an apparatus for allocating time resource in a time division multiple access (TDMA). A mobile station receives a synchronization signal, detects a synchronization symbol from the received synchronization signal, and calculates the correlation between the detected synchronization symbol and an upward link synchronization symbol. Also, the mobile station calculates a determination metric based on the correlation and determines whether the synchronization symbol is detected based on the determination metric. The mobile station occupies time resource according to whether to detect the synchronization symbol.

Description

[0001] METHOD AND APPARATUS FOR TIME ARRANGEMENT [0002]

The present invention relates to a time resource allocation method and apparatus in a time division multiple access (TDMA) system.

A time division multiple access scheme (TDMA) divides a data packet of one user into a plurality of frames. At this time, each frame is divided into several slots and each user is allocated one slot for each frame, so that a data packet for one user is discontinuously transmitted for several frames.

A carrier sensing TDMA (CSTDMA) scheme is a scheme in which users share time and frequency resources and can increase system capacity when frequency resources are limited. However, since collision between mobile stations sharing resources may occur, carrier sensing, that is, carrier sensing should be performed to transmit data only when no carrier is detected in the corresponding resource.

Generally, the carrier sensing method measures a received signal level of a carrier wave, and if it is smaller than a threshold value, it determines that the channel is available and transmits the data. However, when mobile stations share the same slot and one mobile station is located at a cell boundary or a propagation path loss is large between mobile stations, when the mobile station transmits uplink data, the received signal level is measured by another mobile station to be smaller than a threshold value .

Therefore, according to the carrier sensing method, when the propagation path loss is large, there is a high probability that the carrier detection fails, and a data transmission collision occurs between mobile stations or a delay time of data transmission due to a false alarm occurs .

In addition, the conventional carrier wave prevention method is to solve a signal collision between mobile stations having different classes, so that a mobile station of a low class performs carrier detection so that a transmission collision with a high class mobile station does not occur.

A problem to be solved by the present invention is to provide a method and apparatus for determining a channel occupancy by using a synchronous signal in a carrier sensing TDMA (CSTDMA) system to allocate time resources.

A time resource allocation method according to an aspect of the present invention is a method of allocating time resources by sensing a carrier wave in a carrier sensing TDMA (Carrier Sense Time Division Multiple Access) system, Detecting a sync symbol from the sync symbol; Calculating a cross-correlation degree between the detected synchronous symbol and the uplink synchronous symbol; Calculating a decision metric based on the cross correlation; And determining whether to detect a synchronization symbol based on the determination metric.

Wherein the determining comprises: comparing the determination metric with a preset threshold; Determining that a sync symbol is detected if the value of the determination metric is greater than the threshold value; And determining that the sync symbol is not detected if the value of the determination metric is smaller than the threshold value.

Wherein the time resource allocation method further comprises delaying uplink data transmission and attempting carrier detection again in a next frame when it is determined that the synchronous symbol is detected. And determining that the channel is in an unoccupied state when it is determined that the synchronous symbol is not detected, and transmitting the data.

The step of calculating the determination metric may calculate the determination metric based on the calculated cross-correlation and an offset corresponding to a preset maximum size.

The synchronization signal may be included in a frame including a plurality of slots, and included with data and pilot for each slot.

The uplink synchronous symbol may be generated using a ZC (Zadoff Chu) sequence.

The threshold may have a value such that at least one of a missing probability and a false alarm probability is less than a set probability.

According to another aspect of the present invention, there is provided an apparatus for allocating time resources by sensing a carrier wave in a carrier sensing TDMA (Carrier Sense Time Division Multiple Access) system, the apparatus comprising: A demodulating section for demodulating the signal; A physical resource demapping unit for demodulating the demodulated synchronization signal to a physical resource to detect a synchronous symbol; A cross-correlation degree calculation unit for calculating a cross-correlation degree between the detected sync symbol and the uplink sync symbol; A judgment metric calculating section for calculating a judgment metric based on the cross correlation degree; And a sensing unit for determining whether or not to detect a synchronization symbol based on the determination metric.

The sensing unit may determine that a sync symbol is detected if the value of the determination metric is greater than a preset threshold value and may determine that the sync symbol is not detected if the determination metric is less than the threshold value.

If it is determined that the synchronous symbol is detected, the time resource allocation device defer the uplink data transmission and attempt to detect the carrier again in the next frame. If it is determined that the synchronous symbol is not detected, And transmit the data.

The judgment metric calculator may calculate the judgment metric based on the calculated cross-correlation and an offset corresponding to a preset maximum size.

In addition, the time resource allocation apparatus may further include a sequence generator for generating the uplink synchronous symbol using a Zadoff Chu (ZC) sequence.

The threshold may have a value such that at least one of a missing probability and a false alarm probability is less than a set probability.

The time resource allocation device may further comprise: a physical resource mapping unit for mapping the uplink synchronous symbol provided from the sequence generation unit to frequency and time resources; And a modulator for modulating the uplink synchronous symbol mapped to the resource and transmitting the modulated uplink synchronous symbol as a synchronous signal.

According to embodiments of the present invention, in a carrier sensing TDMA (Carrier Sense Time Division Multiple Access) system, a probability of collision of data between mobile stations can be minimized and a data transmission delay time can be reduced.

Particularly, a mobile station of an equivalent class that simultaneously transmits data and a synchronous signal and carries out carrier sensing measures the degree of cross-correlation between the received synchronous signal and its synchronous signal and determines whether or not the synchronous signal is detected. And the data transmission delay time can be shortened.

FIG. 1 is a diagram illustrating a structure of a frame according to an embodiment of the present invention. FIG. 2 is a diagram illustrating data transmission in a CSTDMA communication environment.
3 is a diagram illustrating a process of generating a sync signal according to an embodiment of the present invention.
4 is a diagram illustrating resource mapping of a synchronization signal according to an embodiment of the present invention.
5 is a diagram illustrating a carrier sensing process according to an embodiment of the present invention.
FIG. 6 is a graph illustrating a sewing probability and a fault alarm probability according to a threshold value in the embodiment of the present invention.
7 is a flowchart of a time resource allocation method according to an embodiment of the present invention.
8 is a diagram illustrating a structure of a time resource allocation apparatus according to an embodiment of the present invention.

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. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when an element is referred to as "comprising ", it means that it can include other elements as well, without excluding other elements unless specifically stated otherwise.

Throughout the specification, a mobile station (MS) is referred to as a terminal, a mobile terminal (MT), an advanced mobile station (AMS), a high reliability mobile station (HR- , A subscriber station (SS), a portable subscriber station (PSS), an access terminal (AT), a user equipment (UE) , HR-MS, SS, PSS, AT, UE, and the like.

Also, a base station (BS) may be a coast station, an advanced base station (ABS), a high reliability base station (HR-BS), a node B, a Node B, an eNodeB, an access point (AP), a radio access station (RAS), a base transceiver station (BTS), a mobile multihop relay (MMR) A relay station (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-RS, a femto BS, a home Node B, a home eNodeB, a pico BS, a metro BS, BS, RS, RN, ARS, HR-RS, small base station (BS), etc.) There's also include all or some of the features.

Hereinafter, a time resource allocation method and apparatus according to an embodiment of the present invention will be described.

In a communication system, a multi-level modulation symbol can be transmitted on multiple carriers to increase the transmission rate in limited frequency resources, and carrier sensing TDMA (CSTDMA) can be used as an efficient multiple access scheme to increase system capacity. Using CSTDMA-based multi-carrier modulation schemes in dense regions of equivalent classes of mobile stations can increase system capacity and increase data rates in limited resources. However, it is very important to improve the performance of carrier sensing in order to solve the transmission collision between mobile stations and to reduce the signaling overhead because a plurality of mobile stations share channels.

FIG. 1 is a diagram illustrating a structure of a frame according to an embodiment of the present invention. FIG. 2 is a diagram illustrating data transmission in a CSTDMA communication environment.

In the CSTDMA scheme, each frame is divided into N slots, as shown in FIG. It is necessary not only to transmit data (data, D) and pilot (P) for channel estimation for each slot, but also to transmit synchronous signals (Sync, S) simultaneously for each slot.

For example, as shown in FIGS. 1 and 2, the mobile station A and the mobile station B can simultaneously receive the slot 1. In this case, each mobile station must perform carrier sensing to avoid collision before transmitting uplink data to check whether the slot is available.

In this state, if the carrier signal is measured according to a method of measuring the received signal level of the carrier and determining that the channel is usable if the received signal level is smaller than the threshold value, the probability of failing to detect the carrier in the usable state is increased.

2, when the mobile station A or the mobile station B is located at the cell boundary or the propagation path loss between the mobile station A and the mobile station B is large, when the mobile station A transmits the uplink data to the base station, Can be measured to be smaller than the threshold value. Therefore, although the received signal level of the arbitrary carrier has a value larger than the threshold value, it is determined that the received signal level is smaller than the threshold value, and the corresponding carrier may be excluded from the available state. Therefore, there is a high probability of failure in carrier detection and a collision may occur. Also, a false alarm may occur and a data transmission delay time may be prolonged.

In the embodiment of the present invention, whether or not a channel is available is determined based on whether a sync signal is detected. That is, the cross-correlation degree of the synchronization signal is measured, and if it is smaller than the threshold value, it is determined that the corresponding carrier channel is available and the data is transmitted.

A mobile station, i. E., A node, generates a synchronization signal.

3 is a diagram illustrating a process of generating a sync signal according to an embodiment of the present invention.

을 생성하고, 생성된 동기 심볼을 주파수 자원 및 시간 자원에 매핑한다. 주파수 인덱스 m과 심볼 인덱스 k에 매핑한 동기 신호를

(

)라고 나타낼 수 있다. 여기서, M은 동기 신호가 할당되는 부반송파 개수를 나타내며, K는 동기 신호가 할당되는 심볼 개수를 나타낸다.

의 조건이 성립된다. The node includes a synchronization symbol having a predetermined length Nss

And maps the generated synchronization symbols to frequency resources and time resources. The synchronization signal mapped to the frequency index m and the symbol index k

(

). Here, M represents the number of subcarriers to which the synchronization signal is allocated, and K represents the number of symbols to which the synchronization signal is allocated.

Is satisfied.

4 is a diagram illustrating resource mapping of a synchronization signal according to an embodiment of the present invention.

4, in a communication resource including a frequency resource composed of a plurality of carriers and a time resource composed of a plurality of symbols, a synchronous symbol s (n) is mapped to a frequency index m and a symbol index k, Thereafter, synchronous symbols are sequentially mapped to resources while the frequency index m is increased, and synchronous symbols are sequentially mapped to resources while increasing symbol index k. In this manner, synchronous symbols that are sequentially generated can be mapped to resources.

The synchronous symbol, that is, the synchronous signal, is transmitted together with data (data, D) and pilot (P) for channel estimation for each slot of the frame, as shown in FIG. A node to transmit uplink data performs carrier detection.

5 is a diagram illustrating a carrier sensing process according to an embodiment of the present invention.

를 복조하고 주파수축으로 필터링하여 동기 심볼을 추출한다. 이와 같이 추출된 동기 심볼을

이라고 나타낸다. For carrier sensing, a frame containing a sync signal is received, and a sync signal

And extracts the synchronous symbol by filtering it on the frequency axis. The extracted synchronous symbol

.

과 상향 링크 동기 심볼

간 상호상관도를 산출한다. 산출된 동기 심볼간 상호 상관도를

이라고 표기한다. 상호상관도의 크기를

이라고 하고 최대 크기에 해당하는 옵셋을 nmax라고 하면, 동기 심볼의 검출 여부를 판정하기 위한 판정 메트릭(decision metric)

는 다음 식과 같이 나타낼 수 있다. Then,

And an uplink synchronous symbol

Thereby calculating the cross-correlation between the two. The cross-correlation between the calculated sync symbols is

. The size of the cross correlation

And the offset corresponding to the maximum size is denoted by nmax, a decision metric for determining whether or not the synchronous symbol is detected,

Can be expressed by the following equation.

을 토대로 동기 심볼의 검출 여부를 판정하기 위한 판정 메트릭을 위의 수학식 1을 토대로 산출하고, 산출된 판정 메트릭을 미리 설정된 임계값과 비교한다. The cross-correlation between the calculated sync symbols is

On the basis of Equation (1) above, and compares the calculated determination metric with a preset threshold value.

If the determination metric is larger than the set threshold value, it is determined that the synchronous symbol of index u is detected. In this case, the uplink data transmission is postponed and carrier detection is attempted again in the next frame.

On the other hand, if the determination metric is smaller than the set threshold value, it is determined that the synchronous symbol of index u is not detected. In this case, it is determined that the channel is unoccupied and data is transmitted. Particularly, when it is determined that the synchronous symbol is not detected during a certain frame, the channel can be determined to be unoccupied and data can be transmitted.

In order to detect such a carrier wave, it is effective to use a sequence having a good cross-correlation as a synchronous symbol to improve signal detection performance, and to use a sequence with a low peak-to-average power ratio (PAPR) to be. For example, various ZC (Zadoff Chu) sequences can be used to generate various sync symbols depending on the number of multicarrier carriers.

인 동기 심볼 s(n)은 다음과 같이 나타낼 수 있다. Length is

(N) can be expressed as: < RTI ID = 0.0 > s (n) < / RTI >

은 길이가

인 ZC 시퀀스 집합 중에서 u번째 루트 시퀀스를 나타낸다.

은 다음과 같이 나타낼 수 있다. here

Is the length

Represents the u-th root sequence in the ZC sequence set.

Can be expressed as follows.

는

보다 작은 소수에 해당한다.here

The

It corresponds to a smaller prime number.

The missing probability corresponds to the cumulative density function (CDF) of the decision metric when there is a synchronization signal and noise, and the false alarm probability is the CCDF of the decision metric when there is noise only without a synchronization signal. complementary cumulative density function. In order to improve the signal detection performance, the miss probability and the failure alarm probability should be minimized.

Since the performance of the carrier sensing according to the embodiment of the present invention is more influenced by the transmission collision due to the missing than the data transmission delay caused by the alarm of the failure, in determining the threshold value for detecting the synchronous symbol, It is preferable to keep the sewing probability at a set probability of, for example, less than 0.1%.

FIG. 6 is a graph illustrating a sewing probability and a fault alarm probability according to a threshold value in the embodiment of the present invention.

In FIG. 6, the miss probability and the failure alarm probability of the synchronous signal having the length of 64 are shown according to the threshold value. The threshold can be selected based on the signal to noise ratio (SNR). For example, when the SNR is equal to or greater than 2dB, a threshold value of less than 0.1% can be selected. Alternatively, when the SNR is less than 2dB, a threshold value that makes the missing probability less than 0.1% can be selected.

Therefore, according to the carrier sensing according to the embodiment of the present invention, data transmission collision can be solved even in a condition of low SNR. Also, if the channel availability is determined based on the detection of the synchronization signal, the performance of the carrier detection can be improved even when the SNR is low or the propagation path loss is large.

7 is a flowchart of a time resource allocation method according to an embodiment of the present invention.

In a communication environment using CSTDMA, a frame is divided into a plurality of slots, and each slot includes data and a pilot signal for channel estimation and a synchronization signal.

The node, that is, the mobile station receives the synchronization signal having the above-described frame structure (S100), demodulates the received synchronization signal, and detects the synchronization symbol (S110).

Then, the degree of cross correlation between the detected sync symbol and its uplink sync symbol is calculated (S120). Based on the calculated cross-correlation, a determination metric for determining whether to detect a synchronous symbol is calculated (S130). The determination metric can be calculated based on Equation (1) above, and can be calculated based on an offset corresponding to a cross-correlation and a predetermined maximum size.

Thereafter, a judgment metric for judging whether or not the synchronous symbol is detected is compared with a preset threshold value (S140).

If the determination metric is greater than the set threshold value, it is determined that the sync symbol having the index u is detected (S150). In this case, the uplink data transmission is delayed and the carrier detection is attempted again in the next frame (S160).

On the other hand, if the determination metric is smaller than the set threshold value, it is determined that the synchronous symbol of index u is not detected (S170). In this case, it is determined that the channel is unoccupied and data is transmitted (S180). Particularly, when it is determined that the synchronous symbol is not detected during a certain frame, the channel can be determined to be unoccupied and data can be transmitted.

8 is a diagram illustrating a structure of a time resource allocation apparatus according to an embodiment of the present invention.

A time resource allocation apparatus 1 according to an embodiment of the present invention includes a signal demodulation unit 11, a physical resource demapping unit 12, a cross correlation degree calculation unit 13, a decision metric calculation unit 14, A sensor 15, and a sensing unit 16. And may further include a baseband transmitter 17.

The signal demodulator 11 receives the synchronization signal and demodulates the received synchronization signal.

The physical resource demapping unit 12 demaps the demodulated synchronization signal to a physical resource to detect a synchronization symbol. That is, the synchronous symbol is extracted by filtering the synchronous signal on the frequency axis.

The cross-correlation calculator 13 calculates the cross-correlation between the detected sync symbol and its uplink sync symbol.

The sequence generator 15 provides an uplink synchronization symbol to the cross-correlation degree calculator 13. [ The sequence generator 15 may generate various synchronous symbols depending on the number of the multiple carriers by using a predetermined sequence (for example, a ZC (Zadoff Chu) sequence) Synchronization symbols can be generated using sequences.

The judgment metric calculating section 14 calculates a judgment metric for judging whether or not the synchronous symbol is detected based on the cross-correlation provided from the cross-correlation degree calculating section 13 and the offset corresponding to the maximum size set in advance.

The sensing section 16 compares the judgment metric provided from the judgment metric calculating section 14 with a preset threshold value. If the determination metric is larger than the set threshold value, it is determined that the synchronous symbol is detected. If the determination metric is smaller than the set threshold value, it is determined that the synchronous symbol is not detected. Here, the threshold value can be determined so that the missing probability or the failure alarm probability satisfies a setting condition (for example, less than 0.1%). In addition, the threshold value may be determined so that at least one of the missing probability or the failure alarm probability satisfies the set condition according to the SNR.

Meanwhile, the baseband transmitter 17 may include a physical resource mapping unit 171 and a modulator 172.

The physical resource mapping unit 171 maps the uplink synchronous symbol provided from the sequence generator 15 to frequency and time resources. The modulator 172 modulates the uplink synchronous symbol mapped to the resource, and transmits the uplink synchronous symbol as a synchronous signal.

The time resource allocation apparatus 1 having such a structure can be applied to a marine digital microwave communication system. In maritime digital microwave communication systems, coast stations and mobile stations communicate using CSTDMA, while coast stations are installed on the coast to control mobile stations, allocate access slots, and communicate over a network. Here, the mobile station may be a communication device mounted on a ship to provide IP-based data communication.

The embodiments of the present invention described above are not implemented only by the apparatus and method, but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded.

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 (14)

In a method for allocating time resources by detecting a carrier in a carrier sensing TDMA (Carrier Sense Time Division Multiple Access) system,
The mobile station receiving the synchronization signal and detecting a synchronization symbol from the received synchronization signal;
Calculating a cross-correlation degree between the detected synchronous symbol and the uplink synchronous symbol;
Calculating a decision metric based on the cross correlation; And
Determining whether a synchronization symbol is detected based on the determination metric
, A time resource allocation method The method of claim 1, wherein
The determining step
Comparing the determination metric with a preset threshold value;
Determining that a sync symbol is detected if the value of the determination metric is greater than the threshold value; And
Determining that the synchronous symbol is not detected if the value of the determination metric is smaller than the threshold value
, A time resource allocation method The method according to claim 2, wherein
Deferring uplink data transmission and attempting carrier detection again in a next frame when it is determined that the synchronous symbol is detected; And
If it is determined that the synchronous symbol is not detected, determining that the channel is unoccupied and transmitting data
Further comprising a time resource allocation method The method of claim 1, wherein
Wherein the step of calculating the determination metric includes calculating a determination metric based on the calculated cross-correlation and an offset corresponding to a preset maximum size, The method of claim 1, wherein
Wherein the synchronization signal is included and transmitted with data and pilot for each slot in a frame including a plurality of slots, The method of claim 1, wherein
Wherein the uplink synchronous symbol is generated using a Zadoff Chu (ZC) sequence, The method according to claim 2, wherein
Wherein the threshold has a value such that at least one of a missing probability and a false alarm probability is less than a set probability, In an apparatus for detecting a carrier wave in a carrier sensing TDMA (CSTDMA) system to allocate time resources,
A signal demodulator for receiving the synchronization signal and demodulating the received synchronization signal;
A physical resource demapping unit for demodulating the demodulated synchronization signal to a physical resource to detect a synchronous symbol;
A cross-correlation degree calculation unit for calculating a cross-correlation degree between the detected sync symbol and the uplink sync symbol;
A judgment metric calculating section for calculating a judgment metric based on the cross correlation degree; And
A determination unit for determining whether or not to detect a synchronization symbol based on the determination metric,
And a time resource allocation unit. The method of claim 8, wherein
Wherein the detecting unit determines that a sync symbol is detected if the value of the determination metric is greater than a preset threshold value and determines that a sync symbol is not detected if the value of the determination metric is less than the threshold value, . The method of claim 9, wherein
If it is determined that the synchronous symbol is detected, the time resource allocation device defer the uplink data transmission and attempt to detect the carrier again in the next frame. If it is determined that the synchronous symbol is not detected, And transmits the data. The method of claim 8, wherein
Wherein the determination metric calculation unit calculates the determination metric based on the calculated cross-correlation and an offset corresponding to a preset maximum size. The method of claim 8, wherein
Further comprising a sequence generator for generating the uplink synchronous symbol using a Zadoff Chu (ZC) sequence. The method of claim 9, wherein
Wherein the threshold has a value such that at least one of a missing probability and a false alarm probability is less than a set probability. The method of claim 12, wherein
A physical resource mapping unit for mapping an uplink synchronous symbol provided from the sequence generator to frequency and time resources; And
A modulator for modulating an uplink synchronous symbol mapped to the resource and transmitting the modulated uplink synchronous symbol as a synchronous signal,
Further comprising:

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