WO2013048170A2

WO2013048170A2 - Method and apparatus for transmitting uplink

Info

Publication number: WO2013048170A2
Application number: PCT/KR2012/007887
Authority: WO
Inventors: 안준기; 양석철; 이윤정; 서동연
Original assignee: 엘지전자 주식회사
Priority date: 2011-09-29
Filing date: 2012-09-28
Publication date: 2013-04-04
Also published as: WO2013048170A3

Abstract

Provided are a method and a wireless device for transmitting an uplink. The wireless device transmits a random access preamble from a first serving cell through a first wireless resource, and transmits an uplink channel from a second serving cell through a second wireless resource. The first serving cell belongs to a first timing advance (TA) group, and the second serving cell belongs to a second TA group that differs from the first TA group. All or a portion of the first wireless resource and the second wireless resource overlap.

Description

Uplink transmission method and apparatus

The present invention relates to wireless communication, and more particularly, to a method and apparatus for uplink transmission in a wireless communication system.

The 3rd Generation Partnership Project (3GPP) long term evolution (LTE), an improvement of the Universal Mobile Telecommunications System (UMTS), is introduced as a 3GPP release 8. 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink and single carrier-frequency division multiple access (SC-FDMA) in uplink. A multiple input multiple output (MIMO) with up to four antennas is employed. Recently, a discussion on 3GPP LTE-Advanced (LTE-A), an evolution of 3GPP LTE, is underway.

As disclosed in 3GPP TS 36.211 V8.7.0 (2009-05) "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)", in 3GPP LTE / LTE-A, a physical channel is a downlink channel. It may be divided into a Physical Downlink Shared Channel (PDSCH), a Physical Downlink Control Channel (PDCCH), a Physical Uplink Shared Channel (PUSCH) and a Physical Uplink Control Channel (PUCCH) which are uplink channels.

In order to reduce interference due to uplink transmission between terminals, it is important for the base station to maintain uplink time alignment of the terminals. The terminal may be located in any region within the cell, and the arrival time until the uplink signal transmitted by the terminal reaches the base station may vary depending on the position of each terminal. The arrival time of the terminal located at the cell edge is longer than the arrival time of the terminal located at the cell center. In contrast, the arrival time of the terminal located at the cell center is shorter than the arrival time of the terminal located at the cell edge.

In order to reduce interference between terminals, the base station needs to schedule the uplink signals transmitted by the terminals in the cell to be received within a boundary (hourly) every time. The base station must adjust the transmission timing of each terminal according to the situation of each terminal, this adjustment is called uplink time alignment (uplink time alignment). The random access process is one of processes for maintaining uplink time synchronization. The UE acquires a time alignment value (or TA) through a random access procedure and maintains uplink time synchronization by applying a time synchronization value.

Recently, a plurality of serving cells have been introduced to provide higher data rates. However, the same time alignment value has been applied to all serving cells under the assumption that frequencies between serving cells are adjacent or propagation characteristics between serving cells are similar.

In the existing wireless communication system, uplink transmission is designed considering only the same time synchronization value. Since serving cells having different propagation characteristics may be allocated, it is necessary to design uplink transmission in consideration of having different time synchronization values between cells.

The present invention provides a method for uplink transmission between a plurality of tim advance (TA) groups and a wireless device using the same.

In one aspect, the uplink transmission method includes transmitting a random access preamble through a first radio resource in a first serving cell and transmitting an uplink channel through a second radio resource in a second serving cell, The first serving cell belongs to a first TA group, the second serving cell belongs to a second TA group different from the first TA group, and the first radio resource and the second radio resource are all or Some overlap.

In the overlapped portion, the total transmission power may not exceed the set maximum transmission power.

The uplink channel may include at least one of a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a sounding reference signal (SRS).

In another aspect, a wireless device for uplink transmission includes a radio frequency (RF) unit for transmitting and receiving a radio signal, and a processor connected to the RF unit, wherein the processor is configured to perform a first radio resource in a first serving cell. Instruct the RF unit to transmit a random access preamble through the RF unit, and transmit the uplink channel through a second radio resource in a second serving cell, wherein the first serving cell is a first TA. Advance) group, the second serving cell belongs to a second TA group different from the first TA group, the first radio resources and the second radio resources are all or part of the overlap.

When a plurality of TA (timing advance) groups are configured, it is possible to reduce the ambiguity of uplink transmission between each TA group and to prevent the maximum transmission power of the UE from exceeding.

1 shows a structure of a downlink radio frame in 3GPP LTE.

2 is a flowchart illustrating a random access procedure in 3GPP LTE.

3 shows an example of a random access response.

4 shows an example of a multi-carrier.

5 shows a UL propagation difference between a plurality of cells.

6 illustrates an example in which TAs are changed between a plurality of cells.

7 shows uplink transmission according to an embodiment of the present invention.

8 shows uplink transmission according to another embodiment of the present invention.

9 shows uplink transmission according to another embodiment of the present invention.

10 shows PUSCH and SRS transmission according to the conventional technology.

11 shows PUSCH and SRS transmission when a plurality of TA groups are configured.

12 shows uplink transmission according to another embodiment of the present invention.

13 is a block diagram illustrating a wireless communication system in which an embodiment of the present invention is implemented.

The wireless device may be fixed or mobile and may be called by other terms such as a user equipment (UE), a mobile station (MS), a user terminal (UT), a subscriber station (SS), and a mobile terminal (MT). A base station generally refers to a fixed station for communicating with a wireless device, and may be referred to in other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, and the like.

Hereinafter, the present invention will be applied based on 3rd Generation Partnership Project (3GPP) 3GPP long term evolution (LTE) or 3GPP LTE-A (LTE-Avanced). This is merely an example, and the present invention can be applied to various wireless communication systems. Hereinafter, LTE includes LTE and / or LTE-A.

1 shows a structure of a downlink radio frame in 3GPP LTE. It may be referred to section 6 of 3GPP TS 36.211 V8.7.0 (2009-05) "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical Channels and Modulation (Release 8)".

The radio frame includes 10 subframes indexed from 0 to 9. One subframe includes two consecutive slots. The time it takes for one subframe to be transmitted is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

One slot may include a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain. OFDM symbol is only for representing one symbol period in the time domain, since 3GPP LTE uses orthogonal frequency division multiple access (OFDMA) in downlink (DL), multiple access scheme or name There is no limit on. For example, the OFDM symbol may be called another name such as a single carrier-frequency division multiple access (SC-FDMA) symbol, a symbol period, and the like.

One slot includes 7 OFDM symbols as an example, but the number of OFDM symbols included in one slot may vary according to the length of a cyclic prefix (CP). According to 3GPP TS 36.211 V8.7.0, one slot in a normal CP includes 7 OFDM symbols, and one slot in an extended CP includes 6 OFDM symbols.

A resource block (RB) is a resource allocation unit and includes a plurality of subcarriers in one slot. For example, if one slot includes 7 OFDM symbols in the time domain and the resource block includes 12 subcarriers in the frequency domain, one resource block includes 7 × 12 resource elements (REs). It may include.

The DL (downlink) subframe is divided into a control region and a data region in the time domain. The control region includes up to three OFDM symbols preceding the first slot in the subframe, but the number of OFDM symbols included in the control region may be changed. A physical downlink control channel (PDCCH) and another control channel are allocated to the control region, and a PDSCH is allocated to the data region.

As disclosed in 3GPP TS 36.211 V8.7.0, in 3GPP LTE, a physical channel is a physical downlink shared channel (PDSCH), a physical downlink shared channel (PUSCH), a physical downlink control channel (PDCCH), and a physical channel (PCFICH). It may be divided into a Control Format Indicator Channel (PHICH), a Physical Hybrid-ARQ Indicator Channel (PHICH), and a Physical Uplink Control Channel (PUCCH).

The PCFICH transmitted in the first OFDM symbol of a subframe carries a control format indicator (CFI) regarding the number of OFDM symbols (that is, the size of the control region) used for transmission of control channels in the subframe. The terminal first receives the CFI on the PCFICH, and then monitors the PDCCH.

Unlike the PDCCH, the PCFICH does not use blind decoding and is transmitted on a fixed PCFICH resource of a subframe.

The PHICH carries a positive-acknowledgement (ACK) / negative-acknowledgement (NACK) signal for an uplink hybrid automatic repeat request (HARQ). The ACK / NACK signal for uplink (UL) data on the PUSCH transmitted by the UE is transmitted on the PHICH.

The Physical Broadcast Channel (PBCH) is transmitted in the preceding four OFDM symbols of the second slot of the first subframe of the radio frame. The PBCH carries system information necessary for the terminal to communicate with the base station, and the system information transmitted through the PBCH is called a master information block (MIB). In comparison, system information transmitted on the PDSCH indicated by the PDCCH is called a system information block (SIB).

Control information transmitted through the PDCCH is called downlink control information (DCI). DCI is a resource allocation of PDSCH (also called DL grant), a PUSCH resource allocation (also called UL grant), a set of transmit power control commands for individual UEs in any UE group. And / or activation of Voice over Internet Protocol (VoIP).

In 3GPP LTE, blind decoding is used to detect the PDCCH. Blind decoding is a method of demasking a desired identifier in a CRC of a received PDCCH (which is called a candidate PDCCH) and checking a CRC error to determine whether the corresponding PDCCH is its control channel.

The base station determines the PDCCH format according to the DCI to be sent to the terminal, attaches a cyclic redundancy check (CRC) to the DCI, and unique identifier according to the owner or purpose of the PDCCH (this is called a Radio Network Temporary Identifier) Mask to the CRC.

The control region in the subframe includes a plurality of control channel elements (CCEs). The CCE is a logical allocation unit used to provide a coding rate according to the state of a radio channel to a PDCCH and corresponds to a plurality of resource element groups (REGs). The REG includes a plurality of resource elements. The format of the PDCCH and the number of bits of the PDCCH are determined according to the correlation between the number of CCEs and the coding rate provided by the CCEs.

One REG includes four REs and one CCE includes nine REGs. {1, 2, 4, 8} CCEs may be used to configure one PDCCH, and each element of {1, 2, 4, 8} is called a CCE aggregation level.

The number of CCEs used for transmission of the PDDCH is determined by the base station according to the channel state. For example, one CCE may be used for PDCCH transmission for a UE having a good downlink channel state. Eight CCEs may be used for PDCCH transmission for a UE having a poor downlink channel state.

A control channel composed of one or more CCEs performs interleaving in units of REGs and is mapped to physical resources after a cyclic shift based on a cell ID.

According to 3GPP TS 36.211 V8.7.0, the uplink channel includes a PUSCH, a PUCCH, a Sounding Reference Signal (SRS), and a Physical Random Access Channl (PRACH).

PUCCH supports multiple formats. A PUCCH having a different number of bits per subframe may be used according to a modulation scheme dependent on the PUCCH format. PUCCH format 1 is used for transmission of SR (Scheduling Request), PUCCH format 1a / 1b is used for transmission of ACK / NACK signal for HARQ, PUCCH format 2 is used for transmission of CQI, PUCCH format 2a / 2b is used for CQI and Used for simultaneous transmission of ACK / NACK signals. PUCCH format 1a / 1b is used when transmitting only the ACK / NACK signal in the subframe, and PUCCH format 1 is used when the SR is transmitted alone. When transmitting SR and ACK / NACK at the same time, PUCCH format 1 is used, and an ACK / NACK signal is modulated and transmitted on a resource allocated to the SR.

Now, sounding reference signal (SRS) transmission will be described.

SRS transmission may be divided into periodic SRS transmission and aperiodic SRS transmission. Periodic SRS transmissions are sent in subframes triggered by periodic SRS configuration. The periodic SRS configuration includes an SRS period and an SRS subframe offset. Given a periodic SRS configuration, the UE can transmit the SRS periodically in a subframe that satisfies the periodic SRS configuration.

Aperiodic SRS transmission transmits the SRS when the SRS request of the base station is detected. For aperiodic SRS transmission, the SRS configuration is given in advance. The SRS configuration also includes an SRS period T _SRS and an SRS subframe offset T _Offset .

The SRS request for triggering aperiodic SRS transmission may be included in the DL grant or the UL grant on the PDCCH. For example, if the SRS request is 1 bit, '0' may indicate a negative SRS request and '1' may indicate a positive SRS request. If the SRS request is 2 bits, '00' indicates a negative SRS request and the rest indicates a positive SRS request, but one of a plurality of SRS settings for SRS transmission may be selected.

If the DL grant or UL grant does not include the CI, the SRS may be transmitted in the serving cell of the PDCCH in which the SRS request is detected. If the DL grant or UL grant includes a CI, the SRS may be sent in the serving cell indicated by the CI.

Assume that in subframe n of serving cell c, a positive SRS request is detected. If a positive SRS request is detected, the SRS is n + k, k≥4, and T _SRS > 2 in Time Division Duplex (TDD) and (10 * n _f + k _SRS -T _offset in Frequency Division Duplex (FDD) ) mod T is transmitted in the first subframe that satisfies _SRS = 0. The subframe index k _SRS = {0,1, .., 9} within frame n _f in FDD, and k _SRS in TDD is defined in a predetermined table. In TDD with T _SRS = 2, the SRS is transmitted in the first subframe that satisfies (k _SRS -T _offset ) mod5 = 0.

Hereinafter, the subframe in which the SRS is transmitted is called an SRS subframe or a triggered subframe. In periodic SRS transmission and aperiodic SRS transmission, the SRS may be transmitted in a UE-specifically determined SRS subframe.

In the SRS subframe, the position of the OFDM symbol in which the SRS is transmitted may be fixed. For example, the SRS may be transmitted in the last OFDM symbol of the SRS subframe. The OFDM symbol transmitted through the SRS is called a sounding reference symbol.

The maintenance of UL uplink time alignment in 3GPP LTE is now described.

In order to reduce interference due to UL transmission between terminals, it is important for the base station to maintain uplink time synchronization of the terminals. The terminal may be located in any area within the cell, and the arrival time until the UL signal transmitted by the terminal reaches the base station may vary depending on the location of each terminal. The arrival time of the terminal located at the cell edge is longer than the arrival time of the terminal located at the cell center. In contrast, the arrival time of the terminal located at the cell center is shorter than the arrival time of the terminal located at the cell edge.

In order to reduce the interference between the terminals, the base station needs to schedule the UL signals transmitted by the terminals in the cell to be received within the boundary (hourly) every time. The base station must adjust the transmission timing of each terminal according to the situation of each terminal, and this adjustment is called time synchronization maintenance.

One way to manage time synchronization is the random access procedure. The terminal transmits a random access preamble to the base station. The base station calculates a time alignment value for speeding up or slowing the transmission timing of the terminal based on the received random access preamble. The base station transmits a random access response including the calculated time synchronization value to the terminal. The terminal updates the transmission timing by using the time synchronization value.

In another method, the base station receives a sounding reference signal from the terminal periodically or arbitrarily, calculates a time synchronization value of the terminal through the sounding reference signal, and provides a MAC CE (control) to the terminal. element).

The time synchronization value may be referred to as information that the base station sends to the terminal to maintain uplink time synchronization, and a timing alignment command indicates this information.

In general, since the terminal has mobility, the transmission timing of the terminal is changed according to the speed and position of the terminal. Therefore, it is preferable that the time synchronization value received by the terminal be valid for a specific time. The purpose of this is the Time Alignment Timer.

When the terminal updates the time synchronization after receiving the time synchronization value from the base station, the time synchronization timer starts or restarts. The UE can transmit uplink only when the time synchronization timer is in operation. The value of the time synchronization timer may be notified by the base station to the terminal through an RRC message such as system information or a radio bearer reconfiguration message.

When the time synchronization timer expires or the time synchronization timer does not operate, the UE assumes that the time synchronization is not synchronized with the base station, and does not transmit any uplink signal except the random access preamble.

2 is a flowchart illustrating a random access procedure in 3GPP LTE. The random access procedure is used for the terminal to obtain UL synchronization with the base station or to be allocated UL radio resources.

The terminal receives a root index and a physical random access channel (PRACH) configuration index from the base station. Each cell has 64 candidate random access preambles defined by a Zadoff-Chu (ZC) sequence, and the root index is a logical index for the UE to generate 64 candidate random access preambles.

Transmission of the random access preamble is limited to specific time and frequency resources for each cell. The PRACH configuration index indicates a specific subframe and a preamble format capable of transmitting the random access preamble.

The table below is an example of a random access configuration published in section 5.7 of 3GPP TS 36.211 V8.7.0 (2009-05).

Table 1

PRACH setting index	Preamble format	System frame number	Subframe number
0	0	Even	One
One	0	Even	4
2	0	Even	7
3	0	Any	One
4	0	Any	4
5	0	Any	7
6	0	Any	1, 6

The terminal transmits the randomly selected random access preamble to the base station (S110). The terminal selects one of 64 candidate random access preambles. Then, the corresponding subframe is selected by the PRACH configuration index. The terminal transmits the selected random access preamble in the selected subframe.

The base station receiving the random access preamble sends a random access response (RAR) to the terminal (S120). The random access response is detected in two steps. First, the UE detects a PDCCH masked with a random access-RNTI (RA-RNTI). The terminal receives a random access response in a medium access control (MAC) protocol data unit (PDU) on the PDSCH indicated by the detected PDCCH.

3 shows an example of a random access response.

The random access response may include a TAC, a UL grant, and a temporary C-RNTI.

The TAC is information indicating a time synchronization value sent by the base station to the terminal to maintain UL time alignment. The terminal updates the UL transmission timing by using the time synchronization value. When the terminal updates the time synchronization, the time alignment timer (Time Alignment Timer) is started or restarted.

The UL grant includes UL resource allocation and transmit power command (TPC) used for transmission of a scheduling message described later. TPC is used to determine the transmit power for the scheduled PUSCH.

Referring back to FIG. 2, the terminal transmits the scheduled message to the base station according to the UL grant in the random access response (S130).

Hereinafter, the random access preamble is also referred to as an M1 message, a random access response as an M2 message, and a scheduled message as an M3 message.

Now, referring to section 5 of 3GPP TS 36.213 V8.7.0 (2009-05), the uplink transmission power in 3GPP LTE will be described.

The transmission power P _PUSCH (i) for PUSCH transmission in subframe i is defined as follows.

Equation 1

Here, P _CMAX is the set terminal transmission power, M _PUSCH (i) is the bandwidth of the PUSCH resource allocation in RB unit. P _{O_PUSCH} (j) is a parameter configured by the sum of the cell-specific element P _{O_NOMINAL_PUSCH} (j) and the terminal-specific element P _{O_UE_PUSCH} (j) given in the upper layer when j = 0 and 1. α (j) is a parameter given to the upper layer. PL is a downlink path loss estimate calculated by the terminal. Δ _TF (i) is a terminal specific parameter. f (i) is a terminal specific value obtained from the TPC. min {A, B} is a function that outputs the smaller of A and B.

The transmission power P _PUCCH (i) for PUCCH transmission in subframe i is defined as follows.

Equation 2

Here, P _CMAX and PL are the same as Equation 1, and P _{O_PUCCH} (j) is a parameter configured by the sum of the cell-specific element P _{O_NOMINAL_PUCCH} (j) and the terminal-specific element P _{O_UE_PUCCH} (j) given in the upper layer. h (n _CQI , n _HARQ ) is a value dependent on the PUCCH format. Δ _{F_PUCCH} (F) is a parameter given by an upper layer. g (i) is a terminal specific value obtained from the TPC.

The transmit power P _SRS (i) for SRS transmission in subframe i is defined as follows.

Equation 3

_{_{Here, P CMAX, P O_PUSCH (j}} ), α (j), PL and f (i) is the same as equation 1, and, P _{SRS_OFFSET} is the UE-specific parameters, M _SRS is given in the upper layer shows the bandwidth for SRS transmission .

Now, a multiple carrier system will be described.

The 3GPP LTE system supports a case in which downlink bandwidth and uplink bandwidth are set differently, but this assumes one component carrier (CC). The 3GPP LTE system supports up to 20MHz and may have different uplink and downlink bandwidths, but only one CC is supported for each of the uplink and the downlink.

Spectrum aggregation (or bandwidth aggregation, also known as carrier aggregation) supports a plurality of CCs. For example, if five CCs are allocated as granularity in a carrier unit having a 20 MHz bandwidth, a bandwidth of up to 100 MHz may be supported.

One DL CC or a pair of UL CC and DL CC may correspond to one cell. Accordingly, it can be said that a terminal communicating with a base station through a plurality of DL CCs receives a service from a plurality of serving cells.

4 shows an example of a multi-carrier.

Although there are three DL CCs and three UL CCs, the number of DL CCs and UL CCs is not limited. PDCCH and PDSCH are independently transmitted in each DL CC, and PUCCH and PUSCH are independently transmitted in each UL CC. Since three DL CC-UL CC pairs are defined, the UE may be provided with services from three serving cells.

The UE may monitor the PDCCH in the plurality of DL CCs and receive DL transport blocks simultaneously through the plurality of DL CCs. The terminal may transmit a plurality of UL transport blocks simultaneously through the plurality of UL CCs.

Assume that the pair of DL CC # 1 and UL CC # 1 becomes the first serving cell, the pair of DL CC # 2 and UL CC # 2 becomes the second serving cell, and DL CC # 3 becomes the third serving cell. Each serving cell may be identified through a cell index (CI). The CI may be unique within the cell or may be terminal-specific. Here, an example in which CI = 0, 1, 2 is assigned to the first to third serving cells is shown.

The serving cell may be divided into a primary cell (pcell) and a secondary cell (scell). The primary cell is a cell that operates at the primary frequency and performs an initial connection establishment process, which is a terminal, initiates a connection reestablishment process, or is designated as a primary cell in a handover process. The primary cell is also called a reference cell. The secondary cell operates at the secondary frequency, can be established after the RRC connection is established, and can be used to provide additional radio resources. At least one primary cell is always configured, and the secondary cell may be added / modified / released by higher layer signaling (eg, RRC message).

The CI of the primary cell can be fixed. For example, the lowest CI may be designated as the CI of the primary cell. Hereinafter, the CI of the primary cell is 0, and the CI of the secondary cell is sequentially assigned from 1.

The UE may monitor the PDCCH through a plurality of serving cells. However, even if there are N serving cells, the base station can be configured to monitor the PDCCH for M (M≤N) serving cells. In addition, the base station may be configured to preferentially monitor the PDCCH for L (L≤M≤N) serving cells.

In the existing 3GPP LTE, even if the terminal supports a plurality of serving cells, one TA (Timing Alignment) value is commonly applied to the plurality of serving cells. However, a plurality of serving cells may be spaced apart in the frequency domain so that propagation characteristics may vary. For example, a remote radio header (RRH) and devices may be present in the area of the base station to expand coverage or to remove a coverage hole.

5 shows a UL propagation difference between a plurality of cells.

The terminal is provided with services by the primary cell and the secondary cell. The primary cell is serviced by a base station, and the secondary cell is serviced by an RRH connected to the base station. The propagation delay characteristic of the primary cell and the propagation delay characteristic of the secondary cell may be different due to the distance between the base station and the RRH, the processing time of the RRH, and the like.

In this case, if the same TA value is applied to the primary cell and the secondary cell, it may seriously affect the synchronization of the UL signal.

6 illustrates an example in which TAs are changed between a plurality of cells.

The actual TA of the primary cell is 'TA 1', and the actual TA of the secondary cell is 'TA 2'. Therefore, it is necessary to apply an independent TA for each serving cell.

To apply an independent TA, a TA group is defined. A TA group includes one or more cells to which the same TA applies. TA is applied to each TA group, and the time synchronization timer also operates for each TA group.

Hereinafter, considering a first serving cell, a second serving cell, and two serving cells, the first serving cell belongs to the first TA group, and the second serving cell belongs to the second TA group. The number of serving cells and TA groups is only an example. The first serving cell may be a primary cell or a secondary cell, and the second serving cell may be a primary cell or a secondary cell.

The TA group may include at least one serving cell. Information on the configuration of the TA group may be informed by the base station to the terminal.

In the existing 3GPP LTE / LTE-A system, even though the terminal supports a plurality of serving cells, a single power amplifier is used for UL transmission. When transmitting different UL channels in different serving cells, it may be difficult to block radio frequency (RF) signal components between cells. In particular, this problem may be serious if ULs having a large transmission power difference are transmitted simultaneously in different cells. Thus, simultaneous transmission of heterogeneous UL channels has been difficult.

However, assuming that TA groups fall relatively in frequency, the UE may implement an independent power amplifier for UL transmission in each TA group.

Hereinafter, a method of transmitting a plurality of UL channels in a plurality of TA groups is proposed.

UL channels of different formats or a same format between a plurality of TA groups may transmit a UL channel, such as a PUCCH having a relatively high transmit power, in the same UL subframe. For example, the UE may transmit a PRACH in the first serving cell and simultaneously transmit PUCCH / PUSCH / SRS in the second serving cell. Alternatively, the UE may transmit SRS in the first serving cell and simultaneously transmit PUCCH / PUSCH in the second serving cell.

According to the current 3GPP LTE, PRACH can not be transmitted simultaneously with PUCCH / PUSCH / SRS in the same subframe. According to the proposed invention, when a plurality of TA groups are configured, the UE may transmit PUCCH / PUSCH / SRS in a serving cell belonging to another TA group in the same subframe as the PRACH. That is, even if UL channels cannot be simultaneously transmitted in the same TA group, it is proposed that simultaneous transmission is allowed in different TA groups. The base station may inform the terminal whether the simultaneous transmission between a plurality of TA groups is allowed through the RRC message.

7 shows uplink transmission according to an embodiment of the present invention. The PRACH (or random access preamble) may be transmitted in one cell in each TA group. The first serving cell belongs to the first TA group, and the second serving cell belongs to the second TA group.

When the PRACH is transmitted in the first serving cell, the second serving cell may transmit at least one of a UL channel, that is, PUSCH, PUCCH, and SRS. If the radio resources for transmitting the PRACH and the radio resources for transmitting the UL channel overlap, the total transmit power does not exceed the maximum transmission power set in the overlapped portion. When a PRACH is transmitted in a first serving cell and a PUCCH is transmitted in a second serving cell, it is assumed that one of OFDM symbols in which a PRACH is transmitted and one of OFDM symbols in which a PUCCH is transmitted are overlapped. If the total transmit power of PRACH and PUCCH in the overlapping OFDM symbol does not exceed the maximum transmit power, the PRACH and PUCCH are transmitted in the overlapped OFDM symbol.

Other cells in the TA group to which the first serving cell belongs may not transmit UL channels.

In one subframe, each TA group may transmit a PUCCH in one cell (or primary cell of a specific TA group) in each TA group. Other cells of the TA group may not transmit PRACH / SRS / PUSCH, but cells belonging to another TA group may transmit RPRACH / SRS / PUSCH.

In one subframe, each TA group cannot simultaneously transmit SRS and / or PUSCH through the same OFDM symbol in different cells in each TA group. Cells belonging to different TA groups may transmit SRS and / or PUSCH in the same OFDM symbol.

In one subframe, each TA group cannot simultaneously transmit PUCCHs from different cells in each TA group, but cells belonging to different TA groups can simultaneously transmit PUCCHs. In one subframe, each TA group cannot simultaneously transmit the same PUCCH format in different cells in each TA group, but cells belonging to different TA groups can simultaneously transmit the same PUCCH format. In one subframe, each TA group cannot simultaneously transmit different PUCCH formats in different cells in each TA group, but cells belonging to different TA groups can simultaneously transmit different PUCCH formats.

The base station may inform the user equipment through RRC signaling whether simultaneous transmission of a specific UL channel or UL physical channel format group between the TA groups described above is possible.

A UL channel (eg, PUCCH) carrying uplink control information (UCI) such as CSI and ACK / NACK for each TA group may be transmitted only in a cell belonging to the TA group.

The first serving cell belongs to the first TA group, and the second serving cell belongs to the second TA group. When the radio resources used for transmission of the SRS in the first serving cell and the radio resources used for transmission of the UL channel (that is, at least one of PUSCH, PUCCH, and PRACH) of the second serving cell overlap in part or all. It is a problem. The SRS may include periodic SRS and aperiodic SRS.

For example, if the transmission of the SRS is triggered in the last OFDM symbol of subframe n of the first serving cell, and the PUCCH is transmitted in subframe m + 1 of the second serving cell, the last of subframe n is due to different TAs. Some or all of the OFDM symbol and the first OFDM symbol of the subframe m + 1 may overlap.

In one embodiment, if there is an overlapped portion, the SRS transmission may be dropped. If at least some of the OFDM symbols used for transmission of the SRS and the OFDM symbols used for transmission of the UL channel overlap, the transmission of the SRS is abandoned.

In another embodiment, the transmission of the SRS may be dropped when the overlapped portion exists and the total transmission power of the SRS and the UL channel exceeds a set maximum transmission power. If the total transmit power of the SRS and the UL channel does not exceed the set maximum transmit power, the SRS and the UL channel may be transmitted.

In another embodiment, if the overlapped portion exists and the total transmit power of the SRS and UL channel exceeds the set maximum transmit power, the transmission of the SRS is not dropped, but the total transmit power does not exceed the maximum transmit power. The transmission power of the SRS can be reduced.

The aperiodic SRS dynamically scheduled by the base station may be important compared to other UL channels since the base station is for acquiring the UL channel state at a specific point in time. Thus, when aperiodic SRS is triggered, it may need to be handled differently than periodic SRS.

In one embodiment, if the overlapped portion exists, it may transmit aperiodic SRS and drop transmission of another UL channel in the overlapped portion. Alternatively, the transmission of the UL channel may be abandoned. The UL channel may include a PUCCH carrying CSI.

In another embodiment, if the duplicated portion is present, the aperiodic SRS may be transmitted and the transmit power of another UL channel in the overlapped portion may be lowered so as not to exceed the maximum transmit power. Alternatively, the transmission power may be equally lowered over all OFDM symbols on which the UL channel is transmitted. The UL channel may include a PUCCH carrying CSI.

If the TA difference between two TA groups is greater than the SRS transmission interval, the SRS may not overlap with the UL channel transmitted from another cell.

If the transmission of the SRS is triggered in the last OFDM symbol of subframe n of the first serving cell and the PUCCH is transmitted in subframe m of the second serving cell, but not overlapping with the OFDM symbol for the SRS and the OFDM symbol for the PUCCH, SRS may be transmitted.

10 shows PUSCH and SRS transmission according to the conventional technology.

When the UE transmits the SRS in the last OFDM symbol of one subframe, the PUSCH is not transmitted in the last OFDM symbol. This is to reduce the complexity of the UL transmission of the terminal and to reduce the change in amplitude according to the UL transmission.

In FIG. 10A, a PUSCH is transmitted over all OFDM symbols in a subframe in which SRS is not transmitted. In FIG. 10B, when the SRS is transmitted in the last OFDM symbol, the PUSCH is transmitted over the OFDM symbols except for the last OFDM symbol.

However, if the UE transmits a UL signal through a cell belonging to different TA groups, this operation may cause a problem.

When the UE transmits at least one of PUSCH / PUCCH / PRACH in subframe n + 1 of the first serving cell and transmits SRS in the last OFDM symbol of subframe n of the second serving cell, a duplicate part exists Let's say

In the overlapped portion, if the total transmit power exceeds the maximum transmit power, the SRS may be abandoned. As a result, since the UE does not transmit the SRS in subframe n of the second serving cell, as shown in FIG. 11, the UE transmits the PUSCH over all OFDM symbols.

The base station may not accurately know the transmission timing between the first TA group to which the first serving cell belongs and the second TA group to which the second serving cell belongs. In addition, the base station does not know whether the total transmission power of the terminal exceeds the set maximum transmission power. Therefore, the base station cannot know exactly whether there is a duplicate part and whether the drop of the SRS transmission. Therefore, depending on whether the UE actually transmits the SRS or not, if the UE determines whether to transmit the PUSCH symbol in the corresponding OFDM symbol, a problem may occur in the base station receiving the PUSCH.

In addition, even in the case of allowing the SRS and other UL signals to be transmitted at the same time even if they exist in overlapping areas between different TA groups, the same problem may occur if the total transmission power exceeds the maximum transmission power to give up SRS transmission.

In a subframe configured to transmit an SRS, it is proposed that a PUSCH is not transmitted in a corresponding SRS symbol regardless of whether the UE actually transmits the SRS.

Alternatively, the PUSCH may not be transmitted in a corresponding SRS symbol regardless of whether the UE transmits the SRS for all SRS subframes configured for SRS transmission for each cell or TA group.

Regardless of whether the overlapped region exists, the PUSCH may not be transmitted in the corresponding SRS symbol.

To transmit the PUSCH except for the SRS symbol, exclude from generating a code string to be transmitted to the PUSCH or generate a code string on the assumption that the PUSCH is transmitted to the corresponding SRS symbol, and then map the code string to the corresponding symbol. You may not.

Now, transmission of a UL channel (PUCCH / PUSCH / SRS) different from a PRACH will be described.

A UE configured with a first TA group and a second TA group transmits a PRACH to a first serving cell (eg, a secondary cell) belonging to the first TA group, and transmits a UL channel to a second serving cell belonging to the second TA group. When transmitting, if the total transmit power of the PRACH and UL channels exceeds the maximum transmit power, it is necessary to adjust the transmit power or give up transmission.

In the first embodiment, power allocation may be prioritized in order of PUCCH of the primary cell, PUSCH having UCI, PRACH of the secondary cell, and other channels. From the channel with the lower priority, the transmit power can be reduced or the abandoned transmission can be adjusted so that the total transmit power does not exceed the maximum transmit power.

In the second embodiment, high priority may be given to the UL channel transmitted through the TA group to which the primary cell belongs. Assume that a first serving cell belonging to the first TA group is a secondary cell, and a second serving cell to which the second serving cell belongs is a primary cell. When transmitting UL channels in the first and second serving cells at the same time, the transmission power of the UL channel transmitted in the first serving cell may be preferentially reduced or abandoned.

In the third embodiment, higher priority may be given to other UL channels than the PRACH transmitted in the secondary cell. When the transmission of the PRACH in the secondary cell overlaps the transmission of the UL channel in a cell of another TA group, the transmission power of the PRACH may be first reduced or abandoned.

In a fourth embodiment, higher priority may be given to PRACH. This is because uplink synchronization of the TA group may be delayed if transmission of the PRACH fails. If the transmission interval of the UL channel and the transmission interval of the PRACH overlap, the transmission power can be reduced only in the overlapped portion.

In a fifth embodiment, PRACH may be given a lower priority. In the 3GPP LTE TDD system, there is a PRACH (shorthened-PRACH (sPRACH)) having a short transmission interval, such as a PRACH transmitted through UpPTS. In this case, the entire transmission interval of the PRACH may overlap with all or some of the transmission interval of the UL channel. When the total transmit power exceeds the maximum transmit power, it may be inefficient to abandon the transmission of the UL channel or to reduce the transmit power of the UL channel.

In the corresponding UL channel, transmission may be abandoned or transmission power may be reduced only in a transmission period overlapping with the sPRACH. The UL channel may be a PUCCH or a PUSCH with CSI.

Alternatively, the transmission of the sPRACH may be abandoned or the transmission power may be reduced. The UL channel overlapping with the sPRACH may be a PUCCH with ACK / NACK.

The base station 50 includes a processor 51, a memory 52, and an RF unit 53. The memory 52 is connected to the processor 51 and stores various information for driving the processor 51. The RF unit 53 is connected to the processor 51 and transmits and / or receives a radio signal. The processor 51 implements the proposed functions, processes and / or methods. In the above embodiment, the serving cell and / or TA group may be controlled / managed by the base station, and the operation of one or more cells may be implemented by the processor 51.

The wireless device 60 includes a processor 61, a memory 62, and an RF unit 63. The memory 62 is connected to the processor 61 and stores various information for driving the processor 61. The RF unit 63 is connected to the processor 61 and transmits and / or receives a radio signal. The processor 61 implements the proposed functions, processes and / or methods. In the above-described embodiment, the operation of the terminal may be implemented by the processor 61.

The processor may include application-specific integrated circuits (ASICs), other chipsets, logic circuits, and / or data processing devices. The memory may include read-only memory (ROM), random access memory (RAM), flash memory, memory card, storage medium and / or other storage device. The RF unit may include a baseband circuit for processing a radio signal. When the embodiment is implemented in software, the above-described technique may be implemented as a module (process, function, etc.) for performing the above-described function. The module may be stored in memory and executed by a processor. The memory may be internal or external to the processor and may be coupled to the processor by various well known means.

In the exemplary system described above, the methods are described based on a flowchart as a series of steps or blocks, but the invention is not limited to the order of steps, and certain steps may occur in a different order or concurrently with other steps than those described above. Can be. In addition, those skilled in the art will appreciate that the steps shown in the flowcharts are not exclusive and that other steps may be included or one or more steps in the flowcharts may be deleted without affecting the scope of the present invention.

Claims

Transmit a random access preamble through a first radio resource in a first serving cell,

In the second serving cell comprising transmitting an uplink channel through a second radio resource,

The first serving cell belongs to a first TA group, the second serving cell belongs to a second TA group different from the first TA group,

And all or part of the first radio resource and the second radio resource overlap.
The uplink transmission method of claim 1, wherein the total transmission power in the overlapped portion does not exceed a set maximum transmission power.
The method of claim 1, wherein the uplink channel comprises at least one of a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a sounding reference signal (SRS).
The method of claim 1, wherein the uplink channel is transmitted while a second time alignment timer for the second TA group is in operation.
5. The method of claim 4, wherein the random access preamble is transmitted when the first time synchronization timer for the first TA group is in operation or not in operation.
The uplink transmission method according to claim 1, wherein the first and second radio resources include a plurality of orthogonal frequency division multiplexing (OFDM) symbols, and the overlapped portion includes at least one OFDM symbol. .
The uplink transmission method of claim 1, wherein the first serving cell is a secondary cell and the second serving cell is a primary cell or a secondary cell.
In a wireless device for uplink transmission,

A radio frequency (RF) unit for transmitting and receiving a radio signal; And

Including a processor connected to the RF unit, wherein the processor

Instructing the RF unit to transmit a random access preamble through a first radio resource in a first serving cell,

Instructing the RF unit to transmit an uplink channel through a second radio resource in a second serving cell,

The first serving cell belongs to a first TA group, the second serving cell belongs to a second TA group different from the first TA group,

And all or part of the first radio resource and the second radio resource overlap.
The wireless device of claim 8, wherein the total transmission power in the overlapped portion does not exceed a set maximum transmission power.
The wireless device of claim 8, wherein the uplink channel comprises at least one of a physical uplink shared channel (PUSCH), a physical uplink control channel (PUCCH), and a sounding reference signal (SRS).
10. The wireless device of claim 8, wherein the uplink channel is transmitted while a second time alignment timer for the second TA group is in operation.
12. The wireless device of claim 11, wherein the random access preamble is transmitted when the first time synchronization timer for the first TA group is active or inactive.
10. The wireless device of claim 8, wherein the first and second radio resources include a plurality of orthogonal frequency division multiplexing (OFDM) symbols, and wherein the overlapped portion includes at least one OFDM symbol.
The wireless device of claim 8, wherein the first serving cell is a secondary cell, and the second serving cell is a primary cell or a secondary cell.