WO2017134778A1

WO2017134778A1 - Wireless communication system, base station, and wireless terminal

Info

Publication number: WO2017134778A1
Application number: PCT/JP2016/053254
Authority: WO
Inventors: 大出　高義; 武志芥川; 山本　明弘
Original assignee: 富士通株式会社
Priority date: 2016-02-03
Filing date: 2016-02-03
Publication date: 2017-08-10

Abstract

A wireless communication system (100) is provided with a plurality of base stations (1b) and a wireless terminal (2). The plurality of base stations (1b) issue notifications of the same data. Each of the plurality of base stations (1b) is provided with a transmitter. The transmitter transmits, to a wireless area to be notified of the same data, a synchronization signal based on identification information pertaining to the wireless area. The wireless terminal (2) receives data of which notification was issued by one of the plurality of base stations (1b). The wireless terminal (2) is provided with a receiver. The receiver establishes synchronization of a data reception process on the basis of the synchronization signal.

Description

Wireless communication system, base station and wireless terminal

The present invention relates to a wireless communication system, a base station, and a wireless terminal.

In a wireless network system called LTE (Long Term Evolution) or LTE-Advanced, an identifier (which may be referred to as a “cell ID”) is assigned to a cell formed by a base station. The cell ID assignment can be independently performed by a communication carrier (sometimes abbreviated as “operator”) that manages the base station.

Japanese Patent Laying-Open No. 2015-133634 International Publication No. 2010/070844 Pamphlet

Implementing a service in which a plurality of base stations managed by different operators are shared to broadcast or transmit the same data to a plurality of terminals in each cell (may be referred to as “broadcast” or “multicast”). Let's assume.

Here, if a cell ID for identifying a cell is uniquely assigned to each operator, there is a possibility that the cell IDs coincide with each other between base stations managed by different operators. For example, there is a possibility that a cell that happens to be assigned the same cell ID may exist in the vicinity of a base station (in other words, a “cell”) shared by different operators for the same data transmission.

If the cell IDs match, the synchronization signals generated based on the cell IDs also match, and interference may occur between the synchronization signals. If interference occurs between the synchronization signals, the reception quality of the synchronization signal deteriorates in the wireless terminal, and thus the probability that the wireless terminal will fail to establish synchronization with a cell that provides a service to which the same data is transmitted increases.

In one aspect, the technology described in this specification is intended to ensure synchronization between a plurality of base stations that transmit the same data and a wireless terminal.

In one aspect, the wireless communication system includes a plurality of base stations that broadcast the same data, and a wireless terminal that receives the data broadcasted by any of the plurality of base stations. Each of the plurality of base stations includes a transmission unit that transmits a synchronization signal based on identification information of a wireless area that broadcasts the same data to the wireless area. The wireless terminal includes a receiving unit configured to establish synchronization of the data reception process based on the synchronization signal.

According to the disclosed wireless communication system, a plurality of base stations that transmit the same data can be reliably synchronized with the wireless terminal.

It is a block diagram which shows the structural example of the radio | wireless communications system of embodiment. It is a block diagram which shows the example of application of MCE (Multi-Cell / Multicast | Coordinate | Entity) in the radio | wireless communications system of embodiment. It is a figure which shows typically the function structure of the base station which implements MBSFN (MBMS * Single * Frequency * Network) transmission in the radio | wireless communications system of embodiment. It is a figure which shows typically the function structure of the radio | wireless terminal which receives MBMS (Multimedia | Broadcast | Multicast | Service *) data in the radio | wireless communications system of embodiment. It is a sequence diagram which shows the 1st example of the MBSFN transmission operation | movement in the radio | wireless communications system of embodiment. It is a sequence diagram which shows the 2nd example of the MBSFN transmission operation | movement in the radio | wireless communications system of embodiment. It is a figure which illustrates the hardware constitutions of the base station which implements MBSFN transmission in the radio | wireless communications system of embodiment. It is a figure which illustrates the hardware constitutions of the radio | wireless terminal which receives MBMS data in the radio | wireless communications system of embodiment.

Hereinafter, an embodiment will be described with reference to the drawings. However, the embodiment described below is merely an example, and there is no intention to exclude application of various modifications and techniques not explicitly described in the embodiment. The present embodiment can be implemented with various modifications without departing from the spirit of the present embodiment.

Each figure is not intended to include only the components shown in the figure, but may include other functions.

Hereinafter, in the drawings, the same reference numerals indicate the same parts.

[A] Example of Embodiment [A-1] System Configuration Example As a successor to LTE and LTE-Advanced, a technology called fifth generation mobile communication (5G), which is a high-capacity and high-speed wireless network technology Consideration is ongoing. Further, as one of LTE-Advanced technologies, a service using CA (Carrier Aggregation) has been introduced, and the communication speed in wireless communication has been improved.

The frequency used for CA is currently implemented with a combination of frequencies assigned to the operator. For example, CA is realized by a combination of a plurality of frequencies in a frequency band such as 800 MHz and 1.7 GHz.

Today, radio frequencies are allocated to various communication systems such as emergency communication such as mobile communication and disaster radio, broadcasting and satellite communication, and the frequency allocated to mobile communication is limited. On the other hand, the amount of mobile communication (which may be referred to as “traffic”) is increasing year by year due to the spread of smartphones and the like, and it is difficult to secure a frequency sufficient to meet the demand.

Therefore, discussions have been started on 3GPP standardization organizations (hereinafter referred to as “3GPP” in some cases) regarding the implementation of CA by combining frequencies that can be used without a license such as 5 GHz. ing.

(1.1) LAA and WLAN interworking
In 3GPP, LAA (Licensed assisted access using LTE) technology and WLAN interworking technology are being studied. WLAN interworking is a technique for improving transmission speed by performing CA or DC (Dual Connectivity) between Wi-Fi (IEEE802.11x) and LTE.

LAA is a technology that performs CA with LTE using a frequency that requires a license and LTE configured with a frequency that does not require a license. LTE configured using a frequency that does not require a license, for example, uses an ISM (Industry Science Medical) band (2.4-2.5 GHz) or 5 GHz, and is constructed with the assistance of an existing LTE system. .

Since communication using LAA uses a frequency that does not require a license, it is specified as specific low power communication in Japan.

A frequency that does not require a license is a frequency that can be freely used as long as the upper limit of transmission power, the upper limit of continuous transmission time, and confirmation that the frequency is not used before transmission are observed. It is.

(1.2) Licensed band and Unlicensed band
In the current mobile communication, in general, the frequency used in wireless communication is determined by each country assigning a license to a specific operator based on the frequency allocation established by ITU-R and the circumstances of each country. Yes. “ITU-R” is an abbreviation for International Telecommunication Union Radio communications Sector.

In other words, the operator operates a mobile communication business using a frequency (which may be referred to as “Licensed band”) that requires a license and can be used exclusively.

Unlicensed band is a frequency that can be used without a license, unlike the above-mentioned Licensed band. For example, the ISM band and the 5 GHz band are defined in each country as Unlicensed band.

To use Unlicensedensband, it is stipulated that LBT (Listen Before Talk) be implemented. “LTB” is to confirm that a frequency is not used before transmitting at a certain frequency.

Furthermore, the specifications for Unlicenced band are stipulated by each country. For example, in Japan, the specification of Unlicenced band has a maximum transmission power of 23 dBm per 1 MHz (in other words, 200 mW) or less and a maximum continuous transmission period of 4 msec.

(1.3) MBMS and MBSFN
In 3G and LTE network systems, MBMS, which is a system that can distribute (in other words, “broadcast”) various information such as video, music, and weather forecasts to an unspecified number of users such as TV broadcasting, is a specification. It has become.

MBMS is a transmission method that distributes various types of information to all terminals at once using a common wireless channel (may be referred to as “notification” or “broadcast”) to all terminals in a distribution area. . In MBMS, various types of information and common information are similarly transmitted to all terminals in a specific terminal group (may be referred to as “multicast”).

In the LTE service, MBMS is implemented using the MBSFN transmission method.

In MBSFN, multiple base stations constituting MBSFN transmit the same data simultaneously using the same frequency with the same modulation method and the same coding rate, so that the terminal transmits the signal transmitted from each base station. It is a method that can be synthesized. The “base station” may be referred to as “eNB (eNodeeB)”.

In addition, the specifications of MBSFN are defined in W-CDMA (Wideband Code Division Multiple Access) and LTE. The MBSFN uses the same frequency (or radio resource), the same modulation scheme and the same coding rate, and simultaneously (in other words, “at the same timing”) from a plurality of base stations. It is a technology that transmits data.

As a service using MBSFN, for example, one or a plurality of live videos (may be referred to as “moving images”) are distributed in a stadium such as a soccer field, news, weather forecast, or tourist information. The case where information, such as, is distributed is mentioned.

For example, at the Tokyo Olympics to be held in 2020, distribution of competition content on the stadium is being considered. Since competitions such as athletics, gymnastics, and judo are running simultaneously in one stadium, it is considered beneficial to distribute multiple live images so that viewers can select them. ing.

In LTE, a cell ID (identifier) is assigned to each cell as a method for identifying the cell. The cell ID is assigned to each cell by the operator. In addition, in MBSFN, in order to transmit MBMS data from a plurality of base stations, a common cell ID (may be referred to as “MBSFN ID”) is assigned between base stations.

A base station that performs MBSFN transmission creates and transmits a synchronization signal (first synchronization signal PSS (Primary synchronization Signal) or second synchronization signal SSS (Secondary synchronization Signal) if LTE) based on the cell ID. It is possible. Therefore, it is conceivable that the terminal performs synchronization separately for a plurality of cells.

FIG. 1 is a block diagram illustrating a configuration example of a wireless communication system 100 according to an embodiment.

1 includes, for example, a plurality of

eNBs

1a, 1b, and 1c, and a radio terminal 2. “ENB” is an example of a “base station”.

In the example shown in FIG. 1, eNB1a (may be represented as “eNB1-1”) and m (m is a natural number) eNB1b (may be represented as “eNB2-1 to m”). Belongs to the core network 101a of the operator A. In the example illustrated in FIG. 1, the eNB 1c (may be referred to as “eNB 3-1”) belongs to the core network 101b of the operator B.

The eNB 1a is managed by the operator A, and may perform wireless communication with the wireless terminal 2 corresponding to the operator A in the area indicated by the one-dot chain line in FIG. The eNB 1b is managed by the operator B, and may perform radio communication with a radio terminal (not shown) corresponding to the operator B in an area not shown.

GW (Gateway) 9b and 9c may be provided between the core network 101a of the operator A and the core network 101b of the operator B. In the example shown in FIG. 1, the GW 9b may be provided on the core network 101a side of the operator A, and the GW 9c may be provided on the core network 101b side of the operator B.

GWs 9b and 9c are illustratively network nodes for connecting a computer network to networks with different protocols.

Between the core network 101a of the operator A and the eNB 1a, for example, an MME (Mobility Management Entity) 3a, an SGW (Serving Gateway) 5a, and two PGWs (Packet data network gateway) 6a are provided.

Between the core network 101b of the operator B and the eNB 1c, for example, an MME 3c, an SGW 5c, and a PGW 6c are provided.

The

SGWs

5a and 5c are illustratively gateways that handle user data. Specifically, the

SGWs

5a and 5c may transfer user data using a “communication tunnel” to which a “session” of the user terminal is assigned.

Here, the “communication tunnel” is a logical communication path provided between the

SGWs

5a and 5c and the eNBs 1a and 1c. The “session” is information held by EPC (Evolved Packet Packet Core) for connecting the wireless terminal 2 to the public data communication network (PDN). For example, the user terminal ID and the location information of the user terminal including.

The MMEs 3a and 3c illustratively perform control to switch communication tunnels used for communication of the wireless terminal 2 in cooperation with the

SGWs

5a and 5c, respectively.

The

PGWs

6a and 6c illustratively transfer user data between the

SGWs

5a and 5c and the core network 101a of the operator A and the core network 101b of the operator B, respectively.

The eNB 1b is managed by the operator A, and broadcasts or transmits the same data to the wireless terminal 2 in the area indicated by the broken line in FIG. 1 (may be referred to as “broadcast” or “multicast”). Good. The eNBs 2-1 2-2, and 2-3 may transmit the same data between the eNBs 1b with the same frequency, timing, and modulation scheme.

For example, MCE 2b, MME 3b, BMSC 4, MBMS GW 8, content provider 102, and GW 9b described above are provided between the core network 101a of operator A and eNB 1b. Note that “MCE” is an abbreviation for Multi-Cell / Multicast Coordinate Entity, and “BMSC” is an abbreviation for Broadcast Multicast Service Center.

Details of the MCE 2b, MME 3b, BMSC 4, MBMS GW 8, and content provider 102 will be described below.

(2.1) About MCE 2b The frequency, modulation scheme, coding rate, and transmission timing used for implementing MBSFN may be controlled (in other words, “selected”) by MCE 2b, which is a higher-level device of eNB 1b. The MCE 2b may control the amount of MBMS data to be transmitted. These control functions are sometimes called scheduling.

In addition, the frequency, modulation scheme, coding rate, transmission timing, and the like described above are control information necessary for the wireless terminal 2 to receive MBMS data (hereinafter may be referred to as “MBSFN control information”). It may be. The MCE 2b may notify the MBSFN control information to a plurality of subordinate eNBs 1b.

Further, the MCE 2b may create a list of the contents of MBMS data to be actually transmitted (may be referred to as “content list”) and notify the subordinate eNB 1b.

In the W-CDMA and LTE systems, a slot having 6 or 7 symbols, a subframe having 2 slots, a system frame having 20 slots or 10 subframes (may be referred to as a “radio frame”). The time axis direction is specified. The MCE 2b may define the transmission timing for transmitting the MBMS data using the system frame number, the subframe number, and the slot number, and notify the eNB 1b. Further, the MCE 2b may define the period for transmitting the MBMS data using the subframe or the like and notify the wireless terminal 2 in the same manner.

In addition, the MCE 2b may control one or a plurality of cells and define an area where MBSFN transmission is performed as an MBSFN area. The MCE 2b may assign an MBSFN ID uniquely to each of the fixed MBSFN areas (in other words, “so that it can be identified”). The MCE 2b may notify the assigned MBSFN ID to the eNB 1b.

The MBMS area setting and MBSFN ID assignment may be statically set by the operator when installing the MCE 2b and MME 3b, or may be dynamically assigned by the MCE 2b or the MME 3b described below. . That is, the MBMS area and the MBSFN ID may be dynamically changed (in other words, “control”).

FIG. 2 is a block diagram illustrating an application example of MCE in the wireless communication system 100 of the embodiment.

The MCE 2b may be provided in the wireless communication system 100 independently of the eNB 1b as shown in (1) of FIG. 2, or may be provided as a function of the eNB 1b as shown in (2) of FIG. Good. Moreover, MCE2b may be implement | achieved as one function of MME3b mentioned later.

(2.2) About MME 3b The MME 3b is, for example, provided in the wireless communication system 100 as a host device of the MCE 2b. The MME 3b may have a function of controlling an MBMS data transmission session, a function of controlling content, and the like.

(2.3) About MBMS GW8 MBMS GW8 multicasts MBMS data transmitted from BMSC4 to eNB1b which performs MBSFN transmission, for example. In other words, the MBMS GW 8 may simultaneously transmit the same data to a plurality of eNBs 1b.

The MBMS GW 8 may include an MBMS CP (MBMS Control Plane) 81 and an MBMS UP (MBMS User Plane) 82 as illustrated in (1) and (2) of FIG.

The MBMS CP 81 illustratively transmits the control information received from the BMSC 4 to the eNB 1b.

The MBMS UP 82 exemplarily transmits user data (in other words, “MBMS data”) received from the MBSC 4 to the eNB 1b.

(2.4) Regarding BMSC4 The BMSC4 illustratively manages the delivery of MBMS data. The BMSC 4 may be connected to a content provider 102 and a PDN gateway (PGW; not shown in FIG. 1) 7 as illustrated in FIGS. 2 (1) and (2).

The BMSC 4 may acquire MBMS data (for example, “video data”) from the content provider 102.

The BMSC 4 may transmit MBMS data to the core network 101a of the operator A or the core network 101b of the operator B through the PDN gateway 7.

(2.5) About eNB 1b The eNB 1b exemplarily transmits MBSFN control information such as a frequency notified from the MCE 2b to the radio terminal 2 using the MBMS control channel (MCCH).

The eNB 1b may create MBSFN control information indicating the transmission timing and transmission period notified from the MCE 2b. And eNB1b may transmit the produced MBMS control information to the radio | wireless terminal 2 using the MBMS control channel (MCCH: (Multicast | Control) CHannel) which is a logical channel.

Also, the eNB 1b may create MBMS control information and transmit the created MBMS control information using the shared radio channel (PDSCH) to the radio terminal 2.

The eNB 1b may select data to be transmitted from the MBMS data received from the MBMS GW 8, based on the transmission MBMS data amount notified from the MCE 2b. And eNB1b may transmit MBMS data to the radio | wireless terminal 2 using MTCH (Multicast * Traffic * Channel) which is a logical channel.

Note that the eNB 1b may map the MTCH and MCCH to the transport channel MCH (Multicast Channel) and transmit the MBMS data to the radio terminal 2 using the radio broadcast channel (PBCH: Physical Channel).

The eNB 1b encodes the MBMS data selected as a transmission target in the encoding / modulation unit 114 (described later with reference to FIG. 3), and creates a CRC (Cyclic Redundancy Check) created based on the encoded MBMS data. ) Digits may be added. Also, the eNB 1b may scramble the MBMS data encoded with CRC digits added using the scrambling code created based on the Cell ID and the slot number in the encoding / modulation unit 114. . Then, the eNB 1b may modulate the scrambled data in the encoding / modulation unit 114. Scrambling code creation and scrambling will be described later.

The eNB 1b may be a signal corresponding to multiple access in the transmission multiple access processing unit 115 (described later with reference to FIG. 3), and may be an “OFDMA signal” if the communication method is LTE. ).

The eNB 1b performs frequency conversion on the baseband signal in the transmission radio unit 116 (described later with reference to FIG. 3), converts it into a radio signal, amplifies it, and then wirelessly transmits it via the antenna 10 (described later with reference to FIG. 3). You may transmit to the terminal 2. The eNB 1b may perform the same processing on the MBSFN control signal and the system information and transmit the same to the wireless terminal 2. The system information may include radio channel quality measurement conditions, information on cell selection, MBSFN cell ID, MBSFN ID, and the like.

The eNB 1b may also transmit an RS (Reference Signal, a reference signal, in other words, a “pilot signal”) and a synchronization signal to be described later to the wireless terminal 2. Note that the pilot, synchronization signal, coding, CRC digit addition, and scrambling need not be performed.

(2.6) About Wireless Terminal 2 The wireless terminal 2 may receive system information transmitted from a plurality of base stations, for example.

Specifically, the radio terminal 2 may frequency-convert the received signal received via the antenna 20 into a baseband signal in the reception radio unit 211 (described later with reference to FIG. 4).

The wireless terminal 2 may separate the multiplexed reception from the reception signal converted into the baseband signal in the reception orthogonal multiple access processing unit 212 (described later with reference to FIG. 4).

The radio terminal 2 may demodulate the separated received signal, decode the demodulated received signal, and reproduce the scrambled received signal in the demodulation / decoding unit 213 (described later with reference to FIG. 4).

In addition, the radio terminal 2 may descramble the scrambled received signal in the demodulation / decoding unit 213 using a scrambling code created based on the Cell ID and the slot number.

Further, the radio terminal 2 may determine whether or not the descrambled received signal has an error by CRC in the demodulation / decoding unit 213, separate the CRC digit, and reproduce the MBMS data.

Similarly, the wireless terminal 2 may receive a pilot signal and a synchronization signal. The wireless terminal 2 may demodulate the received signal using a pilot signal received simultaneously with the received signal. The radio terminal 2 may synchronize with the eNB 1b based on the received synchronization signal.

(2.7) MBMS data transmission In LTE, as described above, MBMS data is encoded, and a scramble code is created using the initial value calculated based on the MBSFN ID from the encoded transmission data. Good. The encoded MBMS data may be scrambled using the calculated scramble code. Thereafter, the MBMS data is modulated, subjected to processing necessary for OFDM (or OFDMA) such as FFT (Fast Fourier Transform), and the wireless terminal 2 via the antenna 10 (described later using FIG. 3 and the like). May be sent to. “OFDM” is an abbreviation for Orthogonal Frequency-Division Multiplexing. “OFDMA” is an abbreviation for Orthogonal Frequency-Division Multiple Access.

Also, the MBMS data may be mapped to a transport channel MCH (Multicast Channel). The MCH may be mapped to a PMCH (PhysicalPhysMulticast Channel) which is an example of a physical channel (may be referred to as a “radio channel”). Further, the MNBSFN RS and PMCH may be mapped to a radio resource composed of a frequency (or subcarrier) and a symbol in the time direction and transmitted.

Further, in MBSFN transmission, an MBSFN subframe different from a frame format (which may be referred to as “Non-MBSFN subframe” or “normal subframe”) used by a shared channel (DSCH) for transmitting normal individual data. May be used. Here, the “individual data” may be referred to as “terminal individual data” or “user individual data”. Note that details of MBSFN transmission using MBSFN subframes are described in, for example, section “6.10.2” of Non-Patent Document 1.

(2.8) Scrambling in MBSFN transmission The calculation formula of the initial value of the scrambling code is defined in, for example, section “6.3.1” of Non-Patent Document 1, and specifically, 1). In the following calculation formula, _ns is a slot number. Also,

Is the MBSFN ID.

For example, in section “7.2” of Non-Patent Document 1, a 31-bit PN (Pseudo Noise) code used for scrambling is defined. The PN code may be created by combining two 31-bit Gold codes. In section “7.2” of Non-Patent Document 1, the generator polynomial and initial value of each Gold code are also defined as follows.

Among the generator polynomial and the initial value is specified, replaced by an initial value of "6.3.1" section of the initial values of x _2, for example, Non-Patent Document 1, a scrambling code is generated. Note that Nc in the initial value calculation formula is a slot number.

(2.9) MBSFN pilot A pilot signal mapped to an MBSFN subframe may be referred to as an MBSFN RS. The MBSFN RS is a reference signal sequence derived by a different calculation formula from the RS mapped in the normal subframe, and the arrangement in the subframe (in other words, “mapping”) may be different.

According to section “6.10.2” of Non-Patent Document 1, the following (Equation 2) and MBSFN ID that is an ID for identifying an MBSFN area are used in calculating RS. In other words, (Equation 2) is used to calculate an RS that is transmitted when the eNB 1b performs MBSFN transmission.

Further, the following (Equation 2) indicates that the pilot using the MBSFN ID (in other words, “pilot signal sequence”) is also used in the radio terminal 2 when measuring synchronization or radio channel quality using RS. Used for calculation. “Radio channel quality” is, for example, “RSRQ (Reference Signal Received Quality, reference signal reception quality (or pilot reception quality, reception quality))”, “RSRP (Reference Signal, reference signal reception power (or pilot reception power). , Received power))) "or" Signal to Interference Ratio (SIR) ". In the following (Expression 2), _ns is a slot number.

According to the sections “6.10.1” and “6.10.2” of Non-Patent Document 1, the RS arrangement is different between the MBSFN subframe and the normal subframe. The “normal subframe RS” may be referred to as “CRS (Cell specific RS)” or “Common RS”.

The CP (Cyclic Prefix; may be referred to as “GI (Guard Interval)” or “redundant part”) used in the MBSFN subframe may be different from the CP used in the normal subframe. A CP used in a normal subframe may be referred to as a normal CP (normal CP). On the other hand, the CP used in the MBSFN subframe may be referred to as an extended CP (extended CP).

The extended CP is illustratively longer in the time axis direction than the normal CP. Thereby, it is possible to synthesize and receive transmission waves transmitted from as many eNBs 1b as possible, and it is possible to widen the temporal spread that can be synthesized (in other words, the “range in the time axis direction”).

Therefore, in the extended CP, the number of symbols per slot is one symbol less than that in the normal subframe. For example, a normal subframe has 7 symbols per slot, and an MBSFN subframe has 6 symbols per slot.

In addition, data transmission is performed in units of the above subframes. For example, when one subframe is 1 msec, data transmission may be controlled and data may be transmitted with 1 msec as a minimum unit.

(2.10) Synchronization Signal LTE and LTE-Advanced synchronization signals will be described below.

The LTE synchronization signal may include PSS (Primary synchronization signal; may be referred to as “first synchronization signal”) and SSS (Secondary synchronization signal; “second synchronization signal”). “PSS” is an example of “first synchronization signal”, and “SSS” is an example of “second synchronization signal”.

The LTE synchronization signal indicates a cell ID group number and a number belonging to the group number.

May be used to calculate.

The PSS and SSS may be periodically transmitted from the eNB 1b to the wireless terminal 2. For example, in LTE FDD, in a radio frame having 20 slots, the PSS is transmitted from the eNB 1b to the radio terminal 2 by the first symbol (eg, slot number 0) and the last symbol of the eleventh slot (eg, slot number 10). May be sent to. Further, the SSS may be transmitted by the first slot (for example, slot number 0) and the symbol immediately before the end of the eleventh slot (slot number 10). Note that “FDD” is an abbreviation for Frequency Division Duplex.

(2.11) PSS Calculation Method The PSS may be calculated based on a Zadoff-Chu sequence. The “Zadoff-Chu sequence” may be referred to as “CAZAC (Constant Amplitude Zero AutoCorrelation)”.

Non-Patent Document 2 “6.11.1.1” defines a method for calculating a Primary Synchronization signal. The Primary synchronization signal is the cell ID group number according to (Equation 3) and (Table 1) below.

May be calculated based on

Furthermore, the Primary synchronization signal may be a Zadoff-Chu sequence (may be referred to as a “Zadoff-Chu code”). The Zadoff-Chu sequence is a one's complement periodic complex signal and may be a sequence with zero autocorrelation.

The 62 complex signals calculated as described above may be mapped in the frequency axis direction of OFDMA (in other words, “subcarrier direction”). In addition, Primary synchronization signal does not need to be scrambled.

From Section 6.11.1.1.2 of Non-Patent Document 2, for example, in the case of FDD (type 1), the PSS is the frequency axis direction (in other words, “subcarrier” in the last symbols of slots 0 and 10. Direction "). The last symbol of slots 0 and 10 may be a symbol indicated by l = 6 in the Normal subframe. The PSS may be arranged in ± 31 symbols from the frequency center of 6 RB (Resource Block), and may not be arranged in 5 symbols at both ends.

Since the PSS is arranged at the last symbol in the time axis direction, the head of the slot can be identified and the slot can be synchronized.

(2.12) SSS Calculation Method Next, SSS (Secondary Synchronization Signal) will be described.

From Section “6.11.2.1” of Non-Patent Document 2, SSS may be calculated differently depending on whether it is transmitted with subframe number 0 and when it is transmitted with subframe number 5. . “Subframe number 0” may correspond to “slot number 0”, and “subframe number 5” may correspond to “slot number 10”. Also, the calculation formula may be different between the odd-numbered and even-numbered complex signals to be generated.

Number of the group to which a certain cell ID belongs

Is a number belonging to

C ₀ (n) and c ₁ (n) of an M sequence (M sequence) or a PN sequence (which may be referred to as a “pseudo noise sequence”) are calculated by the following (Equation 4). May be. The initial values used at this time may be x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0, and x (4) = 1.

Also, the number of the group to which a certain cell ID belongs

And m ₀ and m ₁ derived from (Table 2) below,

May be calculated by the following (Formula 5). The initial values used at this time may be x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0, and x (4) = 1.

From Section 6.11.2.2 of Non-Patent Document 2, for example, in the case of type 1 (in other words, “FDD”), an SSS is placed in the symbols one slot prior to the last of slot 0 and slot 10. Is done. The last symbol is

It is. Similarly to the PSS, the SSS is arranged in ± 31 symbols from the frequency center of 6 RBs in the frequency axis direction, and may not be arranged in the 5 symbols at both ends.

Also, since the SSS transmitted in slot 0 and slot 10 is different, the head of the radio frame can be specified, and the radio frame can be synchronized.

In general, in CA in LTE-Advanced, PCell and SCell are cells operated by the same operator, and wireless terminal 2 can synchronize with an accuracy less than that of PCell even if it is an SCell using a license-free frequency. There is a case. Here, PCell (may also be referred to as “main cell” or “first cell”) is an abbreviation for Primary Cell, and may be a cell that does not perform MBSFN transmission. Also, SCell (may be referred to as “sub cell” or “second cell”) is an abbreviation for Secondary Cell, and may be a cell that performs MBSFN transmission.

Therefore, if the wireless terminal 2 synchronizes with the PCell, there is a high possibility that the wireless terminal 2 can also synchronize with the SCell. Even if the transmission timings of the PCell and the SCell coincide with each other, the reception timing may be different if there is a difference between the distance from the PCell to the wireless terminal 2 and the distance from the SCell to the wireless terminal 2. Even in such a case, the wireless terminal 2 can receive data from the PCell and the SCell as long as the reception timing difference is about 1/10 of the CP.

However, it is assumed that MBSFN transmission is performed jointly between a plurality of operators using a frequency that does not require a license. In this case, in order to synchronize the wireless terminal 2 with the PCell and the SCell, all the

eNBs

1a, 1b and 1c of all the operators are synchronized with each other. It is difficult to share a device for performing

As a result, the PCell and the SCell performing MBSFN transmission may not be synchronized. Therefore, it is conceivable that the wireless terminal 2 receives a synchronization signal from each of the PCell and the SCell, and the wireless terminal 2 performs synchronization separately for the PCell and the SCell.

Also, the eNB 1b that performs the MBSFN transmission can create and transmit a synchronization signal based on the cell ID, similarly to the eNBs 1a and 1c that do not perform the MBSFN transmission. Therefore, it is conceivable that the wireless terminal 2 synchronizes the PCell and the SCell separately.

However, there is a possibility that the provider providing PCell and the provider providing SCell are different. Since the assignment of the cell ID is performed independently by the business operator, the method of assigning the cell ID differs between business operators. Therefore, there is a possibility that the cell ID of a cell that performs MBSFN transmission that is shared between carriers matches the cell ID of a cell that is not shared between carriers and that does not perform MBSFN transmission.

Currently, a synchronization signal for synchronization with the eNB 1b that performs MBSFN transmission is not defined, and the definition of the synchronization signal is limited to a synchronization signal using a normal cell ID.

Also, as described above, the rules for assigning cell IDs differ depending on the operator. For this reason, when a normal cell ID is used for synchronization in MBSFN transmission, the same cell ID is assigned in the vicinity of eNB 1b (in other words, “cell”) shared between operators implementing MBSFN transmission. There is a possibility that a new cell exists. When a plurality of cells to which the same cell ID is assigned are present in the vicinity, the synchronization signals may interfere with each other, and the reception quality of the synchronization signals may deteriorate. In the worst case, the eNB 1b and the radio terminal 2 may not be synchronized.

Therefore, in the embodiment, an MBSFN cell ID is newly defined as a cell ID of a cell that performs MBSFN transmission. A specific cell ID among normal 504 cell IDs may be assigned to the MBSFN cell ID.

FIG. 3 is a diagram schematically illustrating a functional configuration of an eNB that performs MBSFN transmission in the wireless communication system 100 according to the embodiment.

ENB1b is provided with the antenna 10 illustratively, and functions as the transmission part 11, the control part 12, and the receiving part 13.

The receiving unit 13 exemplarily receives, via the antenna 10, data transmitted from the wireless terminal 2 using a frequency that does not require a license. The reception unit 13 may include a reception wireless unit 131, a reception multiple access processing unit 132, a demodulation / decoding unit 133, and a wireless measurement unit 134.

The reception radio unit 131 exemplarily receives a signal transmitted from the radio terminal 2 using a frequency that does not require a license via the antenna 10. Then, the reception radio unit 131 may amplify the reception signal and further convert the radio frequency into a baseband signal. Then, the reception radio unit 131 may input the signal converted into the baseband signal to the reception multiple access processing unit 132 and the radio measurement unit 134.

Further, the reception wireless unit 131 may receive a signal transmitted from the wireless terminal 2 using a frequency that requires a license via the antenna 10.

The reception multiple access processing unit 132 exemplarily performs a process of separating multiplexed reception on the reception signal converted into the baseband signal. Then, the reception multiple access processing unit 132 may input the processed reception signal to the demodulation / decoding unit 133.

Demodulation / decoding section 133 exemplarily receives a signal input from reception multiple access processing section 132. Then, the demodulation / decoding unit 133 performs demodulation processing on the received signal. Further, the demodulation / decoding unit 133 may perform a decoding process on the demodulated signal. The demodulation / decoding unit 133 may input the demodulated / decoded signal to the wireless measurement unit 134 and the I / F 11b (described later with reference to FIG. 7).

The wireless measurement unit 134 illustratively determines whether or not a certain frequency that does not require a license is used.

Specifically, the radio measurement unit 134 measures the radio channel quality at a certain frequency that does not require a license based on the inputs from the reception radio unit 131 and the demodulation / decoding unit 133, and determines the measured radio channel quality. It may be compared with a threshold value. “Radio channel quality” may be, for example, “reception field strength”, “pilot reception power”, or “pilot reception quality”.

Then, when the wireless channel quality is equal to or lower than the threshold, the wireless measuring unit 134 may determine that a certain frequency for measuring the wireless channel quality is not used. On the other hand, when the wireless channel quality is equal to or higher than the threshold, the wireless measuring unit 134 may determine that a certain frequency for which the wireless channel quality is measured is used.

For example, the wireless measurement unit 134 compares RSSI (Received Signal Strength Strength Indicator) corresponding to the received electric field strength with a threshold value, and when the RSSI is equal to or lower than the threshold value, a certain frequency for measuring the wireless channel quality is used. It may be determined that it is not. In general, since RSSI is output as a voltage, the wireless measuring unit 134 may compare the voltage or use a digital value as a discrete value obtained by D / A (digital / analog) conversion. You may compare.

Further, the wireless measurement unit 134 may input a determination result obtained by measuring the wireless channel quality to the wireless channel control unit 122 of the control unit 12 described later.

The control unit 12 includes, for example, a system information management / storage unit 121 and a wireless line control unit 122.

The radio network controller 122 illustratively transmits / receives control information to / from the MME 3b.

The control information transmitted to the MME 3b is, for example, a frequency availability confirmation request for requesting the MME 3b for confirmation of availability of a frequency that does not require a license, or a use of a frequency that does not require a license for the MME 3b. It is frequency availability information indicating. The control information received from the MME 3b is, for example, an M-RNTI (MBMS Radio Network Temporaly ID) that identifies a wireless terminal 2 that receives an MBSFN ID and MBSFN data, which will be described later, a used frequency, and a modulation method.

The radio network controller 122 may input information on the modulation scheme, coding rate, radio resource, frequency, etc. to the transmitter 11. Further, the radio network controller 122 may input information regarding radio resources, frequencies, and the like to the receiver 13.

The system information management / storage unit 121 illustratively stores and manages system information. Further, the system information management / storage unit 121 may store and manage a normal cell ID.

The transmission unit 11 exemplarily transmits a synchronization signal based on identification information (which may be referred to as “MBSFN cell ID”) of a wireless area that transmits the same data to the wireless area. Moreover, the transmission part 11 may transmit the synchronous signal based on the identification information (it may be called "MBSFN ID") of the service which transmits the same data to a wireless area.

Thereby, the synchronization between the plurality of eNBs 1b that transmit the same data and the wireless terminal 2 can be reliably performed. Specifically, it can be prevented that the MBFSN cell ID of a cell that performs MBSFN transmission coincides with the cell ID of a cell that does not perform MBSFN transmission. Therefore, it is possible to prevent the synchronization signals generated based on the cell IDs from matching, and to prevent interference between the synchronization signals. Furthermore, it is possible to prevent the reception quality of the synchronization signal in the wireless terminal 2 from deteriorating, and to establish synchronization between the eNB 1a and the wireless terminal 2 with certainty.

Further, even when the eNB 1a that does not perform the connected MBSFN transmission and the eNB 1b that performs the MBSFN transmission of different networks or operators are not synchronized, the radio terminal 2 may be synchronized with the eNB 1b. it can. Even when the eNB 1a that does not perform the MBSFN transmission being connected and the eNB 1b that performs the MBSFN transmission of different networks or operators, the radio terminal 2 can be synchronized with the eNB 1b. it can.

The radio area where the transmission unit 11 transmits the synchronization signal may be an area where each eNB 1b transmits the same data between the eNBs 1b with the same frequency, timing, and modulation scheme. Thereby, several eNB1b can transmit the same data to the radio | wireless terminal 2 at the same timing.

Further, the wireless area where the transmission unit 11 transmits the synchronization signal is an MBSFN area, and the wireless area identification information is information for identifying the MBSFN area. Thereby, the same data can be transmitted by using a plurality of eNBs 1b using MBSFN transmission.

The transmission unit 11 may transmit the transmission data received from the MBMS GW 8 to the wireless terminal 2 through the antenna 10 using a frequency that does not require a license. Thereby, the same data can be transmitted by a plurality of business operators. In addition, it is possible to reduce the usage amount of the frequency that requires a license and to effectively use the frequency.

The transmission unit 11 may include a synchronization signal generation unit 111, a pilot generation unit 112, an MBSFN control information generation unit 113, an encoding / modulation unit 114, a transmission multiple access processing unit 115, and a transmission radio unit 116.

The synchronization signal creation unit 111 exemplarily acquires the MBSFN cell ID from the system information management / storage unit 121 and creates a synchronization signal based on the acquired MBSFN cell ID. Further, the synchronization signal creation unit 111 may acquire the MBSFN ID from the system information management / storage unit 121 and create the synchronization signal based on the acquired MBSFN ID.

The synchronization signal generation unit 111 may acquire a normal cell ID from the system information management / storage unit 121 and generate a synchronization signal based on the acquired cell ID. Thereby, eNB1b can provide the radio | wireless terminal 2 with a voice call service and a packet communication service in addition to MBSFN transmission. Therefore, since one eNB 1b has the functions of eNBs 1a and 1c that do not perform MBSFN transmission, the number of devices provided in the radio communication system 100 can be reduced, and management of the radio communication system 100 becomes easy.

The synchronization signal creation unit 111 may input the created synchronization signal to the encoding / modulation unit 114.

The synchronization signal creation unit 111 is an example of a “generation unit” that generates a synchronization signal based on identification information of a wireless area that transmits the same data.

It should be noted that the details of the method of creating the synchronization signal by the synchronization signal creation unit 111 will be described later using (Equation 6) to (Equation 15).

The pilot creation unit 112 illustratively creates a pilot signal based on the MBSFN ID acquired from the system information management / storage unit 121. Then, pilot creating section 112 may output the created pilot signal to encoding / modulating section 114.

The MBSFN control information creation unit 113 exemplarily creates MBSFN control information based on information on the radio scheme, coding rate, radio resource, etc. acquired from the system information management / storage unit 121 and the radio channel control unit 122. To do.

The encoding / modulation unit 114 exemplarily shows the modulation scheme acquired from the radio channel control unit 122 for the signals input from the synchronization signal generation unit 111, the pilot generation unit 112, and the MBSFN control information generation unit 113. And encoding and modulation based on the information on the coding rate. Further, the encoding / modulation unit 114 may map the input signal to a radio frame, a slot, or a subframe. Then, the encoding / modulation unit 114 may input the mapped signal to the transmission multiple access processing unit 115.

The transmission multiple access processing unit 115 illustratively uses the signal input from the encoding / modulation unit 114 as a signal corresponding to multiple access (which may be an “OFDMA signal” if the communication method is LTE). Convert to

The transmission radio unit 116 illustratively converts the frequency of the signal input from the transmission multiple access processing unit 115 into a radio frequency. Further, the transmission radio unit 116 may amplify the input signal. Thereafter, the transmission radio unit 116 may transmit the input signal to the radio terminal 2 via the antenna 10 using a frequency that does not require a license.

Further, the transmission radio unit 116 may transmit the input signal to the radio terminal 2 via the antenna 10 using a frequency that requires a license.

FIG. 4 is a diagram schematically illustrating a functional configuration of the wireless terminal 2 that receives MBMS data in the wireless communication system 100 according to the embodiment.

The wireless terminal 2 illustratively includes an antenna 20 and includes a reception unit 21, a control unit 22, and a transmission unit 23.

The transmission unit 23 exemplarily transmits transmission data using a frequency that does not require a license via the antenna 20. The transmission unit 23 may function as a transmission radio unit 231, a transmission orthogonal multiple access processing unit 232, and an encoding / modulation unit 233.

The encoding / modulation unit 233 exemplarily receives a transmission data signal from an external device (not shown). Then, the encoding / modulation unit 233 may encode the received signal. Furthermore, the encoding / modulation unit 233 may perform modulation processing on the encoded signal. The encoding / modulating unit 233 may perform encoding and modulation by a method corresponding to a predetermined modulation encoding method or a modulation encoding method instructed by a terminal setting control unit 321 of the control unit 22 described later. Then, the encoding / modulation unit 233 may input the signal subjected to the encoding and modulation processing to the transmission orthogonal multiple access processing unit 232.

For example, the transmission orthogonal multiple access processing unit 232 may use the signal input from the encoding / modulation unit 233 as a signal corresponding to multiple access (an “OFDMA signal” if the communication method is LTE). ). Then, the transmission orthogonal multiple access processing unit 232 may input the converted signal to the transmission radio unit 231.

The transmission wireless unit 231 receives the signal converted by the transmission orthogonal multiple access processing unit 232, for example. In addition, the transmission radio unit 231 may receive an instruction of a frequency band to be transmitted from the terminal setting control unit 221 of the control unit 22 described later. Then, the transmission radio unit 231 may amplify the signal and further convert the baseband signal to a radio frequency. And the transmission radio | wireless part 231 may transmit the signal converted into the radio frequency to eNB1b via the antenna 20. FIG. The transmission radio unit 231 may transmit a signal to the eNB 1b using a frequency that does not require a license.

Also, the transmission radio unit 231 may transmit a signal to the eNB 1b using a frequency that requires a license.

The control unit 22 includes, for example, a terminal setting control unit 221, a system information storage unit 222, and a wireless line control unit 223.

The terminal setting control unit 221 illustratively receives system information input from the system information extraction unit 214 of the reception unit 21 described later. And the terminal setting control part 221 may perform the following control based on system information.

The terminal setting control unit 221 may determine the radio resource allocated to the radio terminal 2 based on the control information designated by the radio channel control unit 223 and also determine the modulation and coding scheme applied. Then, the terminal setting control unit 221 performs reception radio unit 211, reception orthogonal multiple access processing unit 212, demodulation / decoding unit 213, transmission radio unit 231, transmission orthogonal multiple access based on the determined radio resource and modulation and coding scheme. The operations of the processing unit 232 and the encoding / modulating unit 233 may be controlled.

Further, the terminal setting control unit 221 illustratively receives a notification from the wireless line control unit 223 that a frequency that does not require a license is used. Then, the terminal setting control unit 221 may determine that the wireless terminal 2 uses a wireless resource having a frequency that does not require a license. The terminal setting control unit 221 does not require a license for the reception radio unit 211, the reception orthogonal multiple access processing unit 212, the demodulation / decoding unit 213, the transmission radio unit 231, the transmission orthogonal multiple access processing unit 232, and the encoding / modulation unit 233. You may perform control which uses the radio | wireless resource of a various frequency.

The system information storage unit 222 exemplarily receives system information input from the system information extraction unit 214. And the system information storage part 222 may memorize | store the system information of eNB1b. Further, the system information storage unit 222 may store the system information of the eNB 1b in accordance with an instruction from the radio channel control unit 223.

The wireless channel control unit 223 illustratively receives from the control signal extraction unit 215 the input of the cell ID of the SCell extracted by the control signal extraction unit 215 described later of the reception unit 21. Further, the radio channel controller 223 may acquire the MBSFN control information extracted by the control signal extractor 215. Further, the wireless line control unit 223 may receive system information input from the system information extraction unit 214.

The receiving unit 21 illustratively performs synchronization establishment of data reception processing based on the synchronization signal. In addition, the reception unit 21 may receive the reception data transmitted from the eNB 1b using a frequency that does not require a license via the antenna 20.

The reception unit 21 includes a reception radio unit 211, a reception orthogonal multiple access processing unit 212, a bitone / decoding unit 213, a system information extraction unit 214, a control signal extraction unit 215, a synchronization signal extraction unit 216, and a pilot extraction unit 217. May function. In addition, the reception unit 21 may function as the MBSFN pilot creation unit 218, the MBSFN synchronization signal creation unit 219, and the synchronization unit 220.

The reception radio unit 211 illustratively receives a signal transmitted from the eNB 1b via the antenna 20 using a frequency that does not require a license. Here, the reception radio unit 211 may receive an instruction of the frequency band to be received from the terminal setting control unit 221. Then, the reception radio unit 211 may amplify the reception signal and further convert the radio frequency into a baseband signal. In addition, the reception radio unit 211 may input the signal converted into the baseband signal to the reception orthogonal multiple access processing unit 212.

Further, the reception radio unit 211 may receive the signal transmitted from the eNB 1b via the antenna 20 using a frequency that requires a license.

The reception orthogonal multiple access processing unit 212 illustratively performs a process of separating multiplexed reception on the reception signal converted into the baseband signal. The reception orthogonal multiple access processing unit 212 may input the processed reception signal to the demodulation / decoding unit 213.

The demodulation / decoding unit 213 illustratively performs demodulation processing on the signal input from the reception orthogonal multiple access processing unit 212. Further, the demodulation / decoding unit 213 may perform a decoding process on the demodulated signal. The demodulation / decoding unit 213 may perform demodulation and decoding by a method corresponding to a predetermined modulation and coding method or a modulation and coding method instructed by the terminal setting control unit 221. Then, the demodulation / decoding unit 213 may output a signal subjected to demodulation / decoding processing.

The system information extraction unit 214 illustratively extracts system information transmitted from the eNB 1b from the signal input from the demodulation / decoding unit 213. Then, the system information extraction unit 214 may store the extracted system information in the system information storage unit 222. In addition, the system information extraction unit 214 may input the extracted system information to the terminal setting control unit 221 and the wireless line control unit 223. The system information extracted by the system information extraction unit 214 may include network identification information.

For example, the control signal extraction unit 215 receives, from the demodulation / decoding unit 213, MBSFN control information of L (Layer) 1 / L2 that is transmitted by the eNB 1b through a PDCCH (Physical-Downlink-Control-Channel) that is a downlink control channel. Extract from signal.

The MBSFN control information may include information on a cell ID, an MBSFN ID, an MBSFN cell ID, a modulation scheme, and the like.

Then, the control signal extraction unit 215 may input the extracted control information to the wireless line control unit 223. Further, the control signal extraction unit 215 may input the MBSFN ID of the extracted control information to the MBSFN pilot creation unit 218. Further, the control signal extraction unit 215 may input the MBSFN cell ID in the extracted control information to the MBSFN synchronization signal creation unit 219.

The synchronization signal extraction unit 216 illustratively extracts PSS and SSS synchronization signals for each CC (Component Carrier) from the signal input from the demodulation / decoding unit 213. Then, the synchronization signal extraction unit 216 may input the extracted synchronization signal to the synchronization unit 220.

The pilot extraction unit 217 illustratively extracts a pilot signal from the signal input from the demodulation / decoding unit 213 based on the radio frame and slot timing detected by the synchronization unit 220. Then, the pilot extraction unit 217 may input the extracted pilot signal to the synchronization unit 220. For example, in the case of the LTE system, the pilot signal is RS (Reference Signal).

The MBSFN pilot creation unit 218 illustratively creates a pilot based on the MBSFN ID acquired from the control signal extraction unit 215. Then, MBSFN pilot creation section 218 may input the created pilot to synchronization section 220.

The MBSFN synchronization signal creation unit 219 illustratively acquires the MBSFN cell ID extracted by the control signal extraction unit 215, and creates a synchronization signal based on the acquired MBSFN cell ID. Also, the MBSFN synchronization signal creation unit 219 inputs the created synchronization signal to the synchronization unit 220.

For example, the synchronization unit 220 is based on the synchronization signals input from the MBSFN synchronization signal creation unit 219 and the synchronization signal extraction unit 216 and the pilots extracted from the MBSFN pilot creation unit 218 and the pilot extraction unit 217, and the eNB 1b Synchronize.

The reception radio unit 211, the reception orthogonal multiple access processing unit 212, and the bitone / decoding unit 213 are examples of the “first reception unit”. The control signal extraction unit 215, the synchronization signal extraction unit 216, the pilot extraction unit 217, the MBSFN pilot creation unit 218, the MBSFN synchronization signal creation unit 219, and the synchronization unit 220 are examples of the “second reception unit”. is there.

The first receiver exemplarily receives a synchronization signal generated based on the identification information of the radio area where the plurality of eNBs 1b transmit the same data from any of the plurality of eNBs 1b.

The second receiving unit illustratively establishes synchronization of data reception processing based on the synchronization signal.

Hereinafter, an example of setting the MBSFN cell ID separately from the normal cell ID will be described. The MBSFN ID of a radio area that broadcasts the same data may be identification information that is separate from a normal cell ID assigned to a radio area that can be individually formed by a plurality of eNBs 1b.

For example, MBSFN ID is defined as 0-255. The specified MBSFN ID may be used as the MBSFN cell ID.

Here, the normal synchronization signal defined by LTE is calculated based on the normal 504 cell IDs. If the normal sync signal calculation formula is used as it is for the MBSFN sync signal sequence calculation, the normal cell ID and the MBSFN cell ID may match.

Therefore, the MBSFN synchronization signal may be created using a calculation formula different from the normal calculation formula of the sync signal sequence and the MBSFN cell ID. Note that, as described above, the calculation of a normal synchronization signal sequence (in other words, “PSS” and “SSS”) is defined in “6.11” of Non-Patent Document 1, for example.

Hereinafter, similarly to the current LTE synchronization signal, PSS and SSS are set, and using the MBSFN cell ID transmitted in the MBSFN transmission cell, the transmission unit 11 (in other words, “synchronization signal creation unit 111”) An example in which a synchronization signal is generated by the following. A calculation formula for creating a synchronization signal for MBSFN transmission may be defined based on a formula for calculating a synchronization signal of the current LTE.

By defining the formula for calculating the synchronization signal for MBSFN transmission based on the formula for calculating the synchronization signal for the current LTE, the orthogonality between the synchronization signal using the current cell ID and the synchronization signal using the MBSFN cell ID is improved. It becomes higher and interference can be reduced.

Since the MBSFN ID in LTE is 0 to 255, the MBSFN cell ID may be 0 to 255. The MBSFN ID and the MBSFN cell ID may be the same or different. Similarly to the normal cell ID, the MBSFN cell ID may be 128 groups, and one group may include two MBSFN cell IDs.

The MBSFN cell ID is exemplarily shown by the following (formula 6).

The following (Formula 7) shows an example of the calculation formula of PSS in MBSFN transmission, and Table 3 shows the root sequence index of PSS.

The PSS is transmitted as the last symbol of the slot 0 and the slot 10 in the case of FDD, and is transmitted as the third symbol from the end of the subframes 1 and 6 in the case of TDD, as in the current LTE. Good. The normal PSS may have two root sequences, and the respective indexes may be different.

The following (Formula 8) shows an example of an SSS calculation formula in MBSFN transmission.

M ₀ and m ₁ exemplarily satisfy the following (formula 9),

And Table 4.

2 sequences

Is the M series

May be defined as two different shift amounts that cause a cyclic shift.

Is illustratively shown by (Equation 10) below. (Equation 10) differs from (Equation 5) described above in that an offset 7 is added.

In (Equation 10) above,

It is. X (i) may be defined by the following (formula 11).

Note that the initial value of x (i) may be x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0 and x (4) = 1.

The two scrambling sequences c ₀ (n) and c ₁ (n) depending on the PSS are M sequences of the following (formula 12).

May be defined as two different shift amounts that cause a cyclic shift. Also, (Equation 12) may have a different offset amount compared to the example shown in (Equation 4).

here,

And the cell ID group is

It may be.

Also,

Is illustratively

When 0 ≦ i ≦ 30, the above “Expression 32” may be defined by the following (formula 13).

Scrambling sequence

Is the M series

May be defined by the following (Equation 14).

In (Equation 14), m ₀ and m ₁ may be defined by Table 4 above. Also,

Is illustratively

When 0 ≦ i ≦ 30, the above “Equation 38” may be defined by the following (Formula 15).

In addition,

May be x (0) = 0, x (1) = 0, x (2) = 0, x (3) = 0 and x (4) = 1.

The SSS created above is transmitted as the third symbol from the end of slot 0 and slot 10 in the case of FFD, and is transmitted as the second symbol from the end of slot 1 and slot 11 in the case of TDD. It's okay.

In LTE, the synchronization signals (in other words, “PSS” and “SSS”) may be transmitted using the center 32 symbols in the subcarrier direction (in other words, “32 carriers”).

Note that a specific cell ID may be a cell ID for MBSFN transmission common to carriers, and a synchronization signal may be created using the same calculation formula as the current synchronization signal.

The wireless terminal 2 stores a synchronization signal calculation formula or a synchronization signal sequence in advance and calculates a synchronization signal corresponding to all MBSFN cell IDs or reads out a stored synchronization signal sequence based on the MBSFN cell IDs. Good. The wireless terminal 2 may identify the synchronization signal sequence by comparing the plurality of calculated or stored synchronization signal sequences with the received synchronization signal sequence. The wireless terminal 2 can recognize the cell ID by specifying the synchronization signal string.

The eNB 1a that is connected to the wireless terminal 2 and does not perform MBSFN transmission receives the MBSFN cell ID (or, in other words, a base station (or cell that performs MBSFN transmission) notified via the GW 9b that connects different operators. ) Identification information ”) may be notified to the wireless terminal 2.

The wireless terminal 2 that has received the MBSFN cell ID may calculate a synchronization signal sequence based on the MBSFN cell ID. Further, the wireless terminal 2 that has received the MBSFN cell ID may read out the stored synchronization signal sequence based on the received MBSFN cell ID.

As a result, the synchronization signal string can be specified in advance, so that the synchronization process is facilitated. Specifically, the comparison of the synchronization signal sequence for specifying the synchronization signal sequence becomes 1/256 at the maximum.

[A-2] Operation Example A first example of the MBSFN transmission operation in the radio communication system 100 of the embodiment configured as described above will be described with reference to the sequence diagram (processing A1 to A8) shown in FIG. FIG. 5 illustrates an MBSFN transmission operation closed in the core network 101a of the operator A shown in FIG.

The MME 3b may issue a session start instruction to the MCE 2b (Process A1).

The eNB 2-1 may create a synchronization signal and transmit the created synchronization signal to the wireless terminal 2 (processing A2).

The wireless terminal 2 may synchronize with the eNB 2-1 based on the received synchronization signal (process A3).

The MCE 2b may perform MBSFN transmission scheduling (processing A4).

The MCE 2b may transmit MBSFN control information (for example, “transmission timing” or “used frequency”) to the eNBs 2-1 to 2-m based on the result of the performed scheduling ( Process A5).

The eNBs 2-1 to 2-m may transmit the received MBSFN control information to the wireless terminal 2 (processing A6).

The MBMS GW 8 may transmit MBMS data (in other words, “content data”) to the eNBs 2-1 to 2-m (processing A7).

The eNBs 2-1 to 2-m may perform MBSFN transmission of the received MBMS data to the wireless terminal 2 (processing A8). Then, the process may end.

Next, a second example of the MBSFN transmission operation in the wireless communication system 100 according to the embodiment will be described with reference to the sequence diagram (processing B1 to B13) shown in FIG. FIG. 6 illustrates an MBSFN transmission operation over the core network 101a of the operator A and the core network 101b of the operator B shown in FIG.

The MME 3b may issue a session start instruction to the MCE 2b (Process B1).

Upon receiving the session start instruction, the MCE 2b may transmit MBSFN control information (for example, “MBSFN ID” or “MBSFN cell ID”) to the eNBs 2-1 to 2-m ( Process B2).

The MCE 2b may transmit the MBSFN control information to the GW 9b with another network (in other words, “core network 101b of the operator B”) (processing B3).

The GW 9b with another network may transmit MBSFN control information to the MCE 3a (processing B4).

The MCE 3a may transmit the received MBSFN control information to the eNB 1-1 (processing B5).

The eNB 1-1 may transmit the received MBSFN control information to the wireless terminal 2 (processing B6).

The eNB 2-1 may create a synchronization signal and transmit the created synchronization signal to the wireless terminal 2 (processing B7).

The wireless terminal 2 may synchronize with the eNB 2-1 based on the received synchronization signal (Process B8).

The MCE 2b may perform MBSFN transmission scheduling (processing B9).

The MCE 2b may transmit MBSFN control information (for example, “transmission timing” or “used frequency”) to the eNBs 2-1 to 2-m based on the result of the performed scheduling ( Process B10).

The eNBs 2-1 to 2-m may transmit the received MBSFN control information to the wireless terminal 2 (processing B11).

The MBMS GW 8 may transmit MBMS data (in other words, “content data”) to the eNBs 2-1 to 2-m (processing B12).

The eNBs 2-1 to 2-m may perform MBSFN transmission of the received MBMS data to the wireless terminal 2 (processing B13). Then, the process may end.

[A-3] Hardware Configuration Example FIG. 7 is a diagram illustrating a hardware configuration of the eNB 1b that performs MBSFN transmission.

The eNB 1b illustratively includes an LSI (Large-Scale Integrated Circuit) 10a, a DSP (Digital Signal Processor) 10b, and a memory 14, in addition to the antenna 10 described above with reference to FIG. The DSP 10b may be, for example, a CPU (Central （Processing Unit) or a combination of a DSP and a CPU.

The LSI 10a illustratively functions as the transmission radio unit 116 and the reception radio unit 131 described above with reference to FIG.

The DSP 10b is, for example, a processing device that performs various controls and operations, and implements various functions by executing a program stored in the memory 14. That is, the DSP 10b functions as the I / F 11b as shown in FIG. 7, and may function as the control unit 12, the reception unit 13, and the transmission unit 11 described above with reference to FIG. However, since the function as the reception wireless unit 131 among the functions provided in the reception unit 13 is provided in the LSI 10a, the DSP 10b may not be provided. Of the functions provided in the transmission unit 11, the function as the transmission wireless unit 116 is provided in the LSI 10a, and thus may not be provided in the DSP 10b.

Note that a program for realizing the functions as the I / F 11b, the control unit 12, the reception unit 13, and the transmission unit 11 may be provided in a form recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a flexible disk, CD, DVD, Blu-ray disk, magnetic disk, optical disk, magneto-optical disk, or the like. The CD may be a CD-ROM, CD-R, CD-RW, etc., and the DVD may be a DVD-ROM, DVD-RAM, DVD-R, DVD + R, DVD-RW, DVD + RW, HD DVD, etc. .

The computer (DSP 10b in the present embodiment) may read the program from the recording medium described above via a reader (not shown), transfer the program to an internal recording device or an external recording device, and use it. Further, the program may be recorded in a storage device (recording medium) such as a magnetic disk, an optical disk, or a magneto-optical disk, and provided to the computer via a communication path from the storage device.

When realizing the functions as the I / F 11b, the control unit 12, the reception unit 13, and the transmission unit 11, a program stored in the internal storage device (memory 14 in this embodiment) is stored in a computer (in this embodiment). May be executed by the DSP 10b). Further, the computer may read and execute the program recorded on the recording medium.

The I / F 11b is, for example, an interface device for the eNB 1b to communicate with an external device such as the MCE 2b or the MBMS GW 8. As the I / F 11b, for example, various interface cards corresponding to network standards of a wired LAN (Local Area Network), a wireless LAN, and a WWAN (Wireless Wide Area Network) are used.

The memory 14 is a storage device including, for example, a ROM (Read Only Memory) and a RAM (Random Access Memory). A program such as BIOS (Basic Input / Output System) may be written in the ROM of the memory 14. The software program in the memory 14 may be appropriately read and executed by the DSP 10b. The RAM of the memory 14 may be used as a primary recording memory or a working memory.

FIG. 8 is a diagram illustrating a hardware configuration of the wireless terminal 2 that receives MBMS data.

The eNB 1b exemplarily includes an LSI 20a, a DSP 20b, a memory 24, a display unit 25, a microphone 26, and a loudspeaker 27 in addition to the antenna 20 described above with reference to FIG. The DSP 20b may be, for example, a CPU, or a combination of a DSP and a CPU.

The LSI 20a illustratively functions as the transmission radio unit 231 and the reception radio unit 211 described above with reference to FIG.

The DSP 20b is, for example, a processing device that performs various controls and operations, and implements various functions by executing a program stored in the memory 24. That is, the DSP 20b may function as the control unit 22, the reception unit 21, and the transmission unit 23 described above with reference to FIG. 4 as illustrated in FIG. However, since the function as the reception wireless unit 211 among the functions provided in the reception unit 21 is provided in the LSI 20a, the DSP 20b may not be provided. Of the functions provided in the transmission unit 23, the function as the transmission wireless unit 231 is provided in the LSI 20a, and thus may not be provided in the DSP 20b.

The program for realizing the functions as the control unit 22, the receiving unit 21, and the transmitting unit 23 may be provided in a form recorded on a computer-readable recording medium. The computer-readable recording medium is, for example, a flexible disk, CD, DVD, Blu-ray disk, magnetic disk, optical disk, magneto-optical disk, or the like. The CD may be a CD-ROM, CD-R, CD-RW, etc., and the DVD may be a DVD-ROM, DVD-RAM, DVD-R, DVD + R, DVD-RW, DVD + RW, HD DVD, etc. .

The computer (DSP 20b in the present embodiment) may read the program from the recording medium described above via a reader (not shown), transfer it to an internal recording device or an external recording device, and use it. Further, the program may be recorded in a storage device (recording medium) such as a magnetic disk, an optical disk, or a magneto-optical disk, and provided to the computer via a communication path from the storage device.

When realizing the functions as the control unit 22, the reception unit 21, and the transmission unit 23, the program stored in the internal storage device (memory 24 in the present embodiment) is executed by the computer (DSP 20 b in the present embodiment). May be. Further, the computer may read and execute the program recorded on the recording medium.

The memory 24 is, for example, a storage device including a ROM (Read Only Memory) and a RAM (Random Access Memory). In the ROM of the memory 24, a program such as BIOS (Basic Input / Output System) may be written. The software program in the memory 24 may be appropriately read and executed by the DSP 20b. The RAM of the memory 24 may be used as a primary recording memory or a working memory.

The display unit 25 is illustratively a liquid crystal display, a CRT (Cathode Ray Tube), an electronic paper display, or the like, and displays various information for an operator or the like. The display unit 25 may be combined with an input device (not shown), for example, a touch panel.

The microphone 26 exemplarily inputs the voice of the user of the wireless terminal 2 to the DSP 20b.

The loudspeaker 27 exemplarily outputs sound based on the input from the DSP 20b.

[B] Others The disclosed technology is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present embodiment. Each structure and each process of this embodiment can be selected as needed, or may be combined suitably.

DESCRIPTION OF SYMBOLS 100 Wireless communication system 101a Core network of operator A 101b Core network of operator B 102 Content provider 1a eNB
1b eNB
10 antenna 10a LSI
10b DSP
11b I / F
DESCRIPTION OF SYMBOLS 111 Synchronous signal preparation part 112 Pilot signal preparation part 113 MBSFN control information preparation part 114 Encoding / modulation part 115 Transmission multiple access processing part 116 Transmission radio | wireless part 12 Control part 121 System information management and memory | storage part 122 Radio | wireless line control part 13 Reception part 131 Reception Radio Unit 132 Reception Multiple Access Processing Unit 133 Demodulation / Decoding Unit 134 Radio Measurement Unit 14 Memory 1c eNB
2 Wireless terminal 20 Antenna 20a LSI
20b DSP
21 reception unit 211 reception radio unit 212 reception orthogonal multiple access processing unit 213 demodulation / decoding unit 214 system information extraction unit 215 control signal extraction unit 216 synchronization signal extraction unit 217 pilot extraction unit 218 MBSFN pilot creation unit 219 MBSFN synchronization creation unit 22 control Unit 221 terminal control unit 222 system information storage unit 223 radio channel control unit 23 transmission unit 231 transmission radio unit 232 transmission orthogonal multiple access processing unit 233 encoding / modulation unit 24 memory 25 display unit 26 microphone 27 loudspeaker 3a MME
3b MME
3c MME
4 BMSC
5a SGW
5c SGW
6a PGW
6c PGW
7 PDN gateway 8 MBMS GW
81 MBMS CP
82 MBMS UP
9b GW
9c GW

Claims

A plurality of base stations that broadcast the same data;
A wireless terminal that receives the data broadcasted by any of the plurality of base stations,
Each of the plurality of base stations is
A transmission unit that transmits a synchronization signal based on identification information of a wireless area that broadcasts the same data to the wireless area;
The wireless terminal is
A wireless communication system, comprising: a receiver that establishes synchronization of the data reception process based on the synchronization signal.
A plurality of base stations that broadcast the same data;
A wireless terminal that receives the data broadcasted by any of the plurality of base stations,
Each of the plurality of base stations is
A transmission unit that transmits a synchronization signal based on identification information of a service that broadcasts the same data to the wireless area;
The wireless terminal is
A wireless communication system, comprising: a receiver that establishes synchronization of the data reception process based on the synchronization signal.
The wireless communication according to claim 1 or 2, wherein the identification information of the wireless area that broadcasts the same data is identification information that is separate from identification information assigned to a wireless area that can be individually formed by the plurality of base stations. system.
The wireless communication system according to claim 3, wherein the frequency is a frequency that does not require a license.
The wireless area is an area for simultaneously broadcasting the same data from a plurality of base stations to a plurality of wireless terminals using the same frequency and modulation method, and the identification information is information for identifying the wireless area. The wireless communication system according to any one of claims 1 to 4, wherein:
Any one of a plurality of base stations that broadcast the same data,
A generating unit that generates a synchronization signal based on identification information of a wireless area that broadcasts the same data;
A transmitter for transmitting the synchronization signal to the wireless area;
With a base station.
The base station according to claim 6, wherein the frequency is a frequency that does not require a license.
The wireless area is an area for simultaneously broadcasting the same data from a plurality of base stations to a plurality of wireless terminals using the same frequency and modulation scheme, and the identification information is information for identifying the wireless area. The base station according to claim 6 or 7, wherein there is a base station.
A first receiver that receives a synchronization signal generated based on identification information of a wireless area in which a plurality of base stations broadcast the same data, from any of the plurality of base stations;
A second receiver for establishing synchronization of the data reception process based on the synchronization signal;
Wireless terminal equipped with.
The radio terminal according to claim 9, wherein the frequency is a frequency that does not require a license.
The wireless area is an area for simultaneously broadcasting the same data from a plurality of base stations to a plurality of wireless terminals using the same frequency and modulation scheme, and the identification information is information for identifying the wireless area. The wireless terminal according to claim 9 or 10, wherein there is a wireless terminal.