KR102503793B1 - Apparatus and method for transmitting beam-based synchronization signal and acquiring beam-based synchronization in mobile xhaul network system - Google Patents

Abstract

A method and apparatus for transmitting a downlink synchronization signal in a Mobile Xhaul Network (MXN) system are disclosed. The method of transmitting a synchronization signal comprises configuring a plurality of beam sweeping areas at a predetermined period within one radio frame - the beam sweeping areas include a first synchronization signal (SS1), a second synchronization signal (SS2), and a third synchronization signal, respectively. Includes N (N is a natural number of 2 or more) synchronization signal blocks (SSB: Synchronization Signal Block) including (SS3); In the first SSB of the first beam sweeping area among the plurality of beam sweeping areas, SS3 corresponding to N horizontal beam IDs dividing the entire horizontal beam area into N and omni-directionally radiating vertical beams transmitting; And in a second SSB of a second beam sweeping area among the plurality of beam sweeping areas, transmitting SS3 corresponding to N vertical beam IDs that divides the entire vertical beam area into N and omnidirectionally radiates horizontal beams. can be configured to include

Description

Apparatus and method for transmitting beam-based synchronization signal and acquiring beam-based synchronization in mobile xhaul network system}

The present invention relates to a synchronization signal transmission and synchronization acquisition apparatus and method, and more particularly, beam sweeping defined in a physical frame structure in a wireless MXN (Mobile Xhaul Network) system that transmits and receives a millimeter wave (mmWave) band with a large-scale antenna It relates to a method and apparatus for transmitting and receiving a synchronization signal within a beam sweeping area.

The Mobile Xhaul Network (MXN) system is a transmission technology or system for wirelessly replacing high-capacity data transmission of the existing wired network, and uses a large-scale antenna configuration and mmWave band for high-capacity transmission. It is a system using communication technologies such as , beamforming and the like.

The mmWave band has the advantage of being able to transmit large amounts of data over a broadband, but has the disadvantage of having a relatively poor channel environment in a radio link between transceivers due to effects such as high path loss and rain loss. In order to overcome high channel loss in this environment, a large-scale antenna configuration and beamforming through it are essential. The MXN system supports beamforming technology using a 2D planar array antenna to support this.

However, in the initial synchronization acquisition process, a transmission system using a beamforming method must apply a synchronization acquisition method different from a communication system that obtains synchronization using an omni-directional beam such as existing LTE. The beam-based synchronization procedure currently discussed in 3GPP is based on the existing LTE PSS/SSS (primary/secondary synchronization signal) structure and physical frame structure for reasons such as backward compatibility and increased synchronization signal overhead. Discussion is ongoing.

An object of the present invention to solve the above problems is to provide a synchronization signal transmission method and apparatus for effectively supporting beam sweeping in an initial synchronization acquisition process of an MXN system.

To achieve the above object, a method for transmitting a downlink synchronization signal in a Mobile Xhaul Network (MXN) system according to an embodiment of the present invention configures a plurality of beam sweeping areas in a predetermined period within one radio frame. Step - The beam sweeping area includes N (N is a natural number equal to or greater than 2) synchronization signal blocks (SSB) including the first synchronization signal (SS1), the second synchronization signal (SS2), and the third synchronization signal (SS3), respectively. : Synchronization Signal Block) included; In the first SSB of the first beam sweeping area among the plurality of beam sweeping areas, the entire horizontal beam area is divided into N pieces and the vertical beam of the system is omni-directionally radiated, corresponding to N horizontal beam IDs. Transmitting SS3 to be; And in the second SSB of the second beam sweeping area among the plurality of beam sweeping areas, SS3 corresponding to the N vertical beam IDs, which divides the entire vertical beam area into N and omnidirectionally radiates the horizontal beam of the system, is transmitted. It may be configured including the step of doing.

In order to achieve the above object, an apparatus for transmitting a downlink synchronization signal applied to an MXN system according to an embodiment of the present invention includes a processor, a memory and/or storage device storing program commands executed by the processor, and the processor It may be configured to include a transceiver controlled by In this case, the program command may configure a plurality of beam sweeping areas at predetermined cycles within one radio frame. At this time, the beam sweeping area includes N (N is a natural number equal to or greater than 2) sync signal blocks SSB including the first sync signal SS1, the second sync signal SS2, and the third sync signal SS3, respectively. It can be configured to include.

In addition, the program command divides the entire horizontal beam area into N and converts the vertical beam into omni-directional in the first SSB of the first beam sweeping area among the plurality of beam sweeping areas through the transceiver 430. radiating, configured to transmit SS3 corresponding to N horizontal beam IDs, and in a second SSB of a second beam sweeping area among the plurality of beam sweeping areas, the entire vertical beam area is divided into N and the horizontal beam is omnidirectional It may be configured to transmit SS3 corresponding to N vertical beam IDs that radiate.

According to an embodiment of the present invention, a beam-based sync signal is transmitted in the MXN system, and a physical sector ID and a beam ID can be detected using the sync signal at a receiving end.

In addition, in the case of using the beam-based synchronization transmission method proposed in the present invention, since it is possible to transmit a much larger number of beam IDs than the number of synchronization signal blocks (SSBs) within a limited beam sweeping area, configuration of an efficient synchronization signal transmission area and detection of the beam ID becomes possible. Accordingly, an optimal beam ID can be efficiently detected when the MXN node initially establishes a link and re-establishes the link.

1 is a conceptual diagram for explaining a physical frame structure and a beam sweeping area of an MXN system to which an embodiment of the present invention is applied.
2 is a conceptual diagram showing the configuration of a beam sweeping area in more detail in the MXN system to which an embodiment of the present invention is applied.
3 is a flowchart illustrating a procedure for acquiring synchronization using SSB and obtaining a physical sector ID in an MXN system according to an embodiment of the present invention.
4 is a block diagram for explaining the configuration of an apparatus for transmitting a synchronization signal of an MXN system according to an embodiment of the present invention.

Since the present invention can make various changes and have various embodiments, specific embodiments will be illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. Like reference numerals have been used for like elements throughout the description of each figure.

Terms such as first, second, A, and B may be used to describe various components, but the components should not be limited by the terms. These terms are only used for the purpose of distinguishing one component from another. For example, a first element may be termed a second element, and similarly, a second element may be termed a first element, without departing from the scope of the present invention. The terms and/or include any combination of a plurality of related recited items or any of a plurality of related recited items.

It is understood that when an element is referred to as being "connected" or "connected" to another element, it may be directly connected or connected to the other element, but other elements may exist in the middle. It should be. On the other hand, when an element is referred to as “directly connected” or “directly connected” to another element, it should be understood that no other element exists in the middle.

Terms used in this application are only used to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this application, the terms "include" or "have" are intended to designate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, but one or more other features It should be understood that the presence or addition of numbers, steps, operations, components, parts, or combinations thereof is not precluded.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related art, and unless explicitly defined in the present application, they should not be interpreted in an ideal or excessively formal meaning. don't

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings.

As described above, the beam-based synchronization procedure currently discussed in 3GPP is being discussed based on the PSS/SSS structure and the physical frame structure of the existing LTE for the purpose of ensuring backward compatibility and reducing synchronization signal overhead.

However, although this structure can operate properly in a scenario such as 'increasing the capacity of a mobile terminal in a small cell' targeted by 3GPP, the MXN system supporting high-speed data transmission through beamforming in a mobile environment may cause frequent beam search overhead and link setup delay.

Therefore, in the MXN system, in order to support fast beam synchronization setting in a mobile environment, a third synchronization signal ( SS3) is configured as a synchronization signal and transmitted. That is, by additionally transmitting the third synchronization signal SS3 for beam ID discrimination, fast synchronization acquisition and beam search are provided in a communication environment operating in a beam sweeping method.

1 is a conceptual diagram for explaining a physical frame structure and a beam sweeping area of an MXN system to which an embodiment of the present invention is applied.

Referring to FIG. 1 , at least one beam sweeping area 131, 132 may be configured according to a beam sweeping period 120 within one radio frame 110. . That is, the beam sweeping area may be periodically arranged at regular intervals in a designated frequency time domain. Although FIG. 1 shows an example in which two beam sweeping areas are configured within one radio frame period for convenience of explanation, the number of beam sweeping areas may be three or more depending on the purpose of an embodiment of the present invention described later. .

At this time, one beam sweeping area may be composed of a Guard Period (GP) 141 and N Synchronization Signal Blocks (SSBs) 142 to 144 (where N is a natural number equal to or greater than 2).

2 is a conceptual diagram showing the configuration of a beam sweeping area in more detail in the MXN system to which an embodiment of the present invention is applied.

Referring to FIG. 2 , each SSB (SBB #1, SSB #2, ..., SSB #N) constituting the beam sweeping area 132 includes a first synchronization signal SS1 and a second synchronization signal SS2. ) and the third synchronization signal SS3 may be included and transmitted. At this time, the 1/2 synchronization signals SS1 and SS2 may be used to obtain frame synchronization of the terminal for the MXN system and to obtain a physical sector ID. That is, the first/second synchronization signal may have a purpose similar to PSS/SSS of the conventional LTE system.

Meanwhile, as can be seen in FIG. 2, each SSB may correspond to a beam (eg, SSB #1 corresponds to beam #1, SSB #2 corresponds to beam #2, and SSB #N corresponds to beam #1). corresponding to #N). In this case, the corresponding beam ID is defined in a beam codebook based on analog beamforming and may be transmitted through the third synchronization signal SS3.

In general, an exhaustive search-based algorithm is applied to beam transmission in a beam sweeping area. For example, since the beam ID and the SSB are configured to have a one-to-one correspondence, the beam ID may be searched in the order of the SSB. However, if the number of transmittable SSBs and the number of beam IDs are different within the beam sweeping area, a separate estimation algorithm is required. In particular, when the number of IDs of beams operated by the system is several times greater than the number of transmittable SSBs in the beam sweeping area, a considerable delay may be given to the initial beam search, so a solution to this problem is required.

As shown in FIG. 2, the transmitting end constructs and transmits SSB using a designated preamble sequence, transmits a preamble sequence identifying a physical sector ID in SS1 and SS2, and transmits a preamble sequence identifying a beam ID in SS3. send SS1 and SS2 of SSB blocks existing in one beam sweeping area are configured identically (ie, SS1 of SSB #1 and SS1 of SSBs #2 to #N are the same, SS2 of SSB #1 and SSB #2 SS2 of ~#N has the same configuration; however, SS2 (or SS1) can be transmitted by crossing a combination of sequences every half frame for half-frame detection), and SS3 can obtain timing synchronization of SSBs in the beam sweeping area. It is specified and transmitted as many as the number of beam IDs used in the system so that Therefore, in the case of a system using 16 beam IDs, it is common that a total of 16 SS blocks are transmitted in a sweeping period.

3 is a flowchart illustrating a procedure for acquiring synchronization using SSB and obtaining a physical sector ID in an MXN system according to an embodiment of the present invention.

Referring to FIG. 3 , the receiving end may perform symbol timing and frequency synchronization through Cyclic Prefix (CP) (S310). The receiving end detects SS1 for the first time after obtaining symbol timing and frequency synchronization, and through this, half-frame synchronization and a part of the physical sector ID (pSector ID) (e.g., the index within the group of the physical sector ID) Can be obtained (S320).

Thereafter, the receiving end acquires synchronization with a part of the physical sector ID (pSector ID) (eg, a group of physical sector IDs) and the entire frame through SS2 detection (S330). Full-frame synchronization in SS2 can be detected through various algorithms, and can be detected by a method of crossing and transmitting a combination of two gold-sequences in the frequency domain every half frame, like LTE's SSS. .

Thereafter, in step S340, a physical sector ID may be obtained through a combination of SS1 and SS2. If an error in which the physical sector ID is not normally detected occurs through the combination of SS1 and SS2, the process may proceed again from step S310.

Finally, the receiving end acquires accurate frame synchronization for restoring data at the transmitting node by frame synchronization correction through SS3 detection transmitted from a designated location within the beam sweeping area (S350). For example, frame synchronization correction through SS3 detection is estimated through measurement of transmission timing between a guard period in a beam sweeping area and SS3, or a separation distance from a control region detectable by a physical sector ID, and various correction algorithms are used. Applicable. In addition, through SS3 detection, the transmitting node can obtain a beam ID.

A beam ID is defined through a beam codebook based on analog beamforming and transmitted through SS3. In the large-scale antenna configuration of the MXN system, the bore sight of the beam is changed using codebook-based analog beamforming. At this time, the aiming point of the beam refers to the direction of the axis where the antenna gain of the beam transmitted from the directional antenna is maximized, and the analog beam codebook is the half power beam width (HPBW) of each beam when 3D beamforming is applied. , can be applied by defining the aiming point of the beam in the horizontal (azimuth) and vertical (elevation) directions. In the analog beam codebook, 3D beamforming can be implemented through an antenna of a 2D planar array, and beamforming can be implemented by a method such as antenna configuration or electrical tilting. In the beam sweeping area through the defined beam codebook, the specified beam in the codebook is loaded with the SS combination and transmitted.

Table 1 below is an example of an analog beam forming-based beam codebook defining a beam ID, and an example of an analog beam codebook of a 2D flat panel array antenna composed of 1024 antenna elements. Meanwhile, below, it is assumed that the number of SSBs within one beam sweeping area is 16.

At this time, it is a scenario assuming that one sector of the MXN system transmits a range of 60ºx60º of vertical x horizontal domain, and the codebook may change according to the sector area setting of the system and is defined in advance at the transceiver end.

In Table 1, when the entire vertical beam area and the horizontal beam area of the sector are divided into beams each having a beam width of 3.75 degrees (60/3.75 = 16, that is, 16 divisions in the horizontal/vertical directions, respectively), (vertical beam ID A total of 256 beams can be defined as number) x (number of horizontal beam IDs). The 256 beams may be used by being mapped with beam IDs in various ways, and Table 2 below shows an example of beam ID mapping. For example, Table 2 below illustrates a case where 16 of 256 beams are mapped to 16 beam IDs of 1 to 16 by mapping to (horizontal beam index = vertical beam index = beam ID).

As described above, in addition to the case where the number of detectable beams and the number of SSBs have a one-to-one correspondence between beams and beam IDs, for more detailed beam management or fast beam search, the number of beam IDs and It may also be possible to configure the number of SSBs differently (ie, when there is no one-to-one correspondence).

For example, the following three cases are possible.

1) When the number of SSBs in the beam sweeping area and the number of beam IDs in the beamforming codebook are the same

In the case of having a mapping relationship between beams and beam IDs as shown in Table 2 described above, when the number of SSBs transmittable in the beam sweeping area is the same as the number of beam IDs, the exhaustive search method in the beam sweeping area Synchronization signals may be sequentially transmitted through all beams by applying an algorithm.

2) When the number of SSBs in the beam sweeping area is greater than the number of beam IDs in the beamforming codebook

If the number of SSBs that can be transmitted in the beam sweeping area is greater than the number of beam IDs defined in the beamforming codebook, the algorithm of the full search method is applied in the beam sweeping area, and additional search is supported in the remaining sweeping period or the remaining sweeping period is a GP period. can be left as

When conducting an additional search, it is possible to apply various methods, such as additional transmission of frequently used beams through training or repeated transmission from the first beam ID.

3) When the number of SSBs in the beam sweeping area is less than the number of beam IDs in the beamforming codebook

When the number of transmittable SSBs in the beam sweeping area is less than the number of beam IDs defined in the beamforming codebook, a search method for transmitting a synchronization signal according to the following two embodiments can be applied.

Also, in this case, a method of separately defining and transmitting an analog codebook for transmission of a synchronization signal in a transmitting/receiving node may be used. The following algorithm can be applied to the analog codebook for synchronization signal transmission.

No. 1 Example

A beam having a wide HPBW as shown in Tables 3 and 4 below is configured to satisfy the condition of '(number of SSBs in beam sweeping area) ≥ (number of beam IDs in beamforming codebook)' in the synchronization signal analog codebook. Configured so that the entire sector area can be searched. This corresponds to a method of setting the horizontal beam width and vertical beam width of each beam four times wider than in Table 1 (ie, a method of increasing a beam width of 3.75 degrees to a beam width of 15 degrees four times). In this case, since the number of horizontal beams (4) * the number of vertical beams (4) = 16, it is possible to adjust SSB and beam ID to have a one-to-one correspondence. That is, the first embodiment may correspond to a technique of matching the number of SSBs and the number of beam IDs by adjusting the beam width of the horizontal/vertical beams.

2nd Example

Each analog codebook using horizontal/vertical beamforming is configured to search the sector area and obtain a beam ID to be mapped (horizontal beam ID, vertical beam ID). In a scenario in which 256 beams can be transmitted as shown in Table 1 above, a beam codebook for synchronization signal transmission can be generated as shown in Tables 5 and 6 below. Table 5 divides the entire horizontal beam area of the sector into N (that is, the number of SSBs in the beam sweeping area) and sets it to have an omni-directional radiation width vertically. This is an example of a method of dividing the entire vertical beam area into N and setting it to have an omnidirectional radiation width horizontally.

When the beam codebooks shown in Tables 5 and 6 are used, beams having different beam widths are formed in vertical and horizontal domains to transmit synchronization signals. In the above transmission method, the beam ID is divided into horizontal and vertical directions and transmitted over two beam sweeping areas within the entire radio frame. At the receiving end, the distinction between the horizontal ID and the vertical ID is implicitly transmitted through SS2 detection, and in this case, the final beam ID used for the radio link in the system can be mapped in Table 2.

That is, according to the codebook defined in Table 5, in the first SSB of the first beam sweeping area, the transmitter divides the entire horizontal beam area into N pieces and omni-directionally radiates the vertical beam of the system, SS3 corresponding to N horizontal beam IDs is transmitted. In addition, according to the codebook defined in Table 6, the transmitting end divides the entire vertical beam area into N pieces in the second SSB of the second beam sweeping area and omni-radiates the horizontal beam of the system to N vertical beam IDs. Corresponding SS3 is transmitted.

In the case of the receiving end, a horizontal beam ID is obtained from SS3 of the first SSB of the first beam sweeping area, and a vertical beam ID is obtained from SS3 of the second SSB of the second beam sweeping area. Through the combination of the obtained horizontal beam ID and vertical beam ID, all 256 beams that can be generated by the 2D flat antenna shown in Tables 1 and 2 can be detected.

4 is a block diagram for explaining the configuration of an apparatus for transmitting a synchronization signal of an MXN system according to an embodiment of the present invention.

Referring to FIG. 4, a synchronization signal transmission device 400 according to an embodiment of the present invention includes a processor 410, a memory 420, a transceiver 430 that transmits a synchronization signal to a receiving end, and a storage device 440. ) and bus 450. The processor 410, the memory 420, the transceiver 430, and the storage device 440 of the synchronization signal transmission device 400 are connected to the bus 450 to communicate with each other. Alternatively, the processor 410, the memory 420, the transceiver 430, and the storage device 440 may be directly connected through a dedicated 1-to-1 interface.

The processor 410 may execute a program command stored in at least one of the memory 420 and the storage device 440 . The processor 410 may mean a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor on which methods according to embodiments of the present invention are performed. Each of the memory 420 and the storage device 440 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 420 may include at least one of read only memory (ROM) and random access memory (RAM).

A program command executed by the processor 410 may configure a plurality of beam sweeping areas at predetermined cycles within one radio frame. At this time, the beam sweeping area includes N (N is a natural number equal to or greater than 2) synchronization signal blocks SSB including the first synchronization signal SS1, the second synchronization signal SS2, and the third synchronization signal SS3. Synchronization Signal Block).

In addition, the program command divides the entire horizontal beam area into N pieces in the first SSB of the first beam sweeping area among the plurality of beam sweeping areas through the transceiver 430 and converts the vertical beam of the system into omni-direction (omni -directional) radiating, configured to transmit SS3 corresponding to N horizontal beam IDs, and in the second SSB of the second beam sweeping area among the plurality of beam sweeping areas, the entire vertical beam area is divided into N and the system It may be configured to transmit SS3 corresponding to N vertical beam IDs that omnidirectionally radiate horizontal beams of .

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention within the scope not departing from the spirit and scope of the present invention described in the claims below. You will understand that it can be done.

110: radio frame
120: beam sweeping cycle
131, 132: beam sweeping area
141: protection zone
142~144: synchronization signal block (SSB)
SS1, SS2, SS3: 1st/2/3rd sync signal

Claims (10)

A downlink synchronization signal transmission method based on a beam sweeping method,
configuring a plurality of beam sweeping areas in a predetermined cycle within one radio frame; and
N (N is a natural number equal to or greater than 2) sync signal blocks including the first sync signal SS1, the second sync signal SS2, and the third sync signal SS3 in each beam sweeping area of the plurality of beam sweeping areas. Including the step of transmitting (SSB: Synchronization Signal Blocks),
The SS3s of the N SSBs of the first beam sweeping area among the plurality of beam sweeping areas are vertically omi-directionally radiated and horizontally correspond to the divided N beams one-to-one, sequentially. , and the SS3s of the N SSBs of the second beam sweeping area among the plurality of beam sweeping areas are omnidirectionally radiated horizontally and correspond one-to-one to the divided N beams vertically sequentially. transmitted,
Downlink synchronization signal transmission method. The method of claim 1,
SS3 of each of the N SSBs corresponds to a beam ID defined by a beam codebook based on analog beamforming,
Downlink synchronization signal transmission method. In claim 1,
The SS3s of the N SSBs are sequentially transmitted in a one-to-one correspondence to all beams transmitted by the beam sweeping scheme.
Downlink synchronization signal transmission method. In claim 1,
Among the N SSBs, SS3s of L (L is a natural number less than N) SSBs are sequentially transmitted in a one-to-one correspondence to all beams transmitted in the beam sweeping scheme, and the L SSBs among the N SSBs (NL) SSBs, excluding SSBs, are used for additional search or used as GP intervals.
Downlink synchronization signal transmission method. delete A synchronization acquisition method using a downlink synchronization signal transmitted by a beam sweeping method,
Acquiring information on a beam codebook based on analog beamforming;
Among N (N is a natural number greater than or equal to 2) synchronization signal blocks (SSBs) including the first synchronization signal SS1, the second synchronization signal SS2, and the third synchronization signal SS3, at least Receiving one SSB; and
Acquiring frame synchronization, a physical sector identifier (ID), and/or a beam ID based on the received at least one SSB and the beam codebook,
A plurality of beam sweeping regions are configured at a predetermined period within one radio frame, and the N SSBs are transmitted in each beam sweeping region of the plurality of beam sweeping regions;
The SS3s of the N SSBs of the first beam sweeping area among the plurality of beam sweeping areas are vertically omi-directionally radiated and horizontally correspond to the divided N beams one-to-one, sequentially. , and the SS3s of the N SSBs of the second beam sweeping area among the plurality of beam sweeping areas are omnidirectionally radiated horizontally and correspond one-to-one to the divided N beams vertically sequentially. transmitted,
How to get motivated. The method of claim 6,
SS3 of each of the N SSBs corresponds to a beam ID defined by the beam codebook,
How to get motivated. In claim 6,
The SS3s of the N SSBs are sequentially transmitted in a one-to-one correspondence to all beams transmitted by the beam sweeping scheme.
How to get motivated. In claim 6,
Among the N SSBs, SS3s of L (L is a natural number less than N) SSBs are sequentially transmitted in a one-to-one correspondence to all beams transmitted in the beam sweeping scheme, and the L SSBs among the N SSBs (NL) SSBs, excluding SSBs, are used for additional search or used as GP intervals.
How to get motivated. delete

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