Preamble retransmission method in mobile communications system

Method for retransmitting pre-sequence code in mobile communication system

The present invention relates to an evolved universal mobile telecommunication system (E-UMTS), and specifically, relates to a method for retransmitting a transmission channel preamble in a mobile communication system for updating between a terminal and a base station Fast uplink time synchronization.

Figure 1 shows the network structure of E-UMTS, which is related to the mobile telecommunication system of both the prior art and the present invention. The E-UMTS is a system that has evolved from the existing UMTS system.

The Third Generation Partnership Project (3GPP) is currently developing the basic specifications of the E-UMTS system. The E-UMTS system can be called a long-term evolution (LTE) system.

As shown in Figure 1, an E-UMTS network can be composed of an E-UTRAN and a core network (CN). E-UTRAN may include user equipment (UE), a base station called eNodeB or eNB, and an access gateway (AG) located at the end of the network and connected to an external network.

The AG can be divided into a part for processing user traffic and a part for processing control traffic. The AG part for processing user traffic and the AG part for processing control traffic can be connected to each other via a new interface for communication.

One or more cells may exist in an eNodeB (eNB), and the eNodeB may be connected by an interface for transmitting user traffic or controlling traffic.

CN may also include AG and a node for user registration of UE. An interface can also be provided in E-UMTS to distinguish E-UTRAN and CN.

The radio interface protocol layer between a mobile terminal and a network can be divided into a first layer (L11) and a second layer according to the three lower layers of the well-known Open System Interconnection (OSI) model in communication systems. Layer (L2), and a third layer (L3). A physical layer of the first layer uses a physical channel to provide information transfer. A radio resource control (RRC) layer located in the third layer controls the radio resources between the mobile terminal and the network.

The RRC layer exchanges RRC messages between the mobile terminal and the network. The RRC layer can be located in each network node such as eNodeB and AG, or located in eNodeB or AG.

Figure 2 shows the architecture of the control plane of the radio interface protocol between a terminal and a UMTS terrestrial radio access network (UTRAN) based on the 3GPP radio access network specifications. The radio interface protocol level is represented by a physical layer, a data link layer, and a network layer, and the vertical is represented by a user plane for transmitting data and a control plane for transmitting control signals.

The protocol layers in Figure 2 can be divided into a first layer (L1), a second layer (L2), and a third layer according to the three lower layers of the well-known Open System Interconnection (OSI) model in communication systems. Layer (L3). The radio protocol layers in the control plane shown in Figure 2 and the radio protocol layers in the user plane shown in Figure 3 will now be explained.

A physical layer (which is the first layer) uses a physical channel to provide information transfer services to an upper layer. The physical layer is connected to a media access control (MAC) layer via a transmission channel, which is located on the upper layer.

Data is transferred between the MAC layer and the physical layer via a transmission channel. Data is also transferred between different physical layers (specifically, between a physical layer on the transmitting side and a physical layer on the receiving side).

The MAC layer of the second layer provides services to the radio link control (PLC) layer (which is the upper layer) via a logical channel. The RLC layer of the second layer supports reliable data transmission.

It should be noted that the RLC layer is described in the dashed line, because if the RLC function is implemented in and performed by the MAC layer, the RLC layer itself may not need to exist.

The packet data convergence protocol (PDCP) layer of the second layer is used to use IP packets (such as IPv4 or IPv6) to efficiently transmit data on the radio interface with a relatively narrow bandwidth. The PDCP layer implements header compression to reduce the size of the header of a fairly large IP packet containing unnecessary control information.

A radio resource control (RRC) layer at the bottom of the third layer is only defined in the control plane. The RRC layer handles the transmission and physical channels used for the configuration, reconfiguration, and release of radio transmission. A radio transmission (RB) refers to a service provided by the second layer for data transfer between mobile terminals and UTRAN.

The downlink transmission channel used to transmit data from a network to a mobile terminal can include a broadcast channel (BCH) for transmitting system information, and a downlink transmission channel for transmitting user traffic or control messages Shared channel (SCH). User traffic or control messages for downlink multicast services or broadcast services can be transmitted via the downlink SCH, or via an additional downlink multicast channel (MCH). Used to transmit data from a mobile terminal to a network uplink transmission channel, which can include a random access channel (RACH) for transmitting an initial control message, and an uplink for transmitting user traffic or control messages Link shared channel (SCH).

The orthogonal frequency division multiplexing (OFDM) method used in a physical layer (which is the first layer) will now be explained in detail. The basic principle of OFDM is to divide a data stream with a high transmission rate (or high rate) into multiple data streams with a low transmission rate (or low rate), and use multiple carriers to simultaneously transmit the multiple data streams.

This plural carrier system is called a subcarrier. The orthogonality existing between the plural carriers allows the frequency components of the carrier to be detected by a receiving end even if the components overlap each other.

The high-rate data stream is converted into a complex low-rate data stream by a serial-to-parallel converter. A carrier is multiplied by the complex number to convert the data stream in parallel. These data streams are then added and transmitted to the receiving end.

The complex data stream converted by the serial-to-parallel converter can be transmitted to the complex sub-carrier using inverse discrete Fourier transform (IDFT). IDFT can be effectively implemented by adapting an inverse fast Fourier transform (IFFT).

The symbol duration of the low-rate sub-carrier in OFDM is increased to reduce the relative signal dispersion caused by a time-based multipath delay curve. Inserting a guard interval longer than the delay dispersion of a channel between OFDM symbols can reduce inter-symbol interference. If a part of the OFDM symbol is copied and placed in the guard interval, the OFDM signal will cyclically extend to protect the symbol.

A related technique Orthogonal Frequency Division Multiple Access (OFDMA) will now be explained. OFDMA refers to a multi-access method that enables a part of the secondary carrier to be provided to individual users, which can be used to adapt OFDM to a modulation method.

OFDMA provides a frequency resource called a secondary carrier to an individual user. Each frequency resource is independently provided to many individual users so that they do not overlap with each other. Therefore, frequency resources are allocated exclusively.

A discrete Fourier transform single orthogonal frequency division multiple (DFT-S-OFDM) method is called single carrier frequency division multiple access FDMA (SC-FDMA). A related art SC-FDMA scheme is usually used in the uplink, where the expansion is first applied in a discrete Fourier transform (DFT) matrix at a frequency region before generating an OFDM signal, and then the result is based on a The related technology OFDM method modulation used for transmission.

Figure 4 shows the structure of a transmitter adapted to the related technology DFT-S-OFDM method. Several variables have been defined to explain the operation of the transmitter. "N" indicates the number of sub-carriers for transmitting an OFDM signal, "Nb" refers to the number of sub-carriers used for a user, "F" refers to a DFT matrix, "s" refers to a data symbol vector, "x" Refers to a vector of data scattered in the frequency zone, and "y" refers to a vector of OFDM symbols transmitted in the time zone.

SC-FDMA uses DFT matrix to scatter data symbols before transmitting data symbol "s", as shown in Equation 1.

<maths><img file="TW200742382A_D0001.tif" /></maths>

<img file="TW200742382A_D0002.tif" />Refers to a DFT matrix of the size "Nb" used to disperse the data symbol "s". Sub-carrier mapping is performed for the dispersed vector "x" by adapting a certain sub-carrier allocation method. The secondary carrier mapping vector "x" is then converted into a time zone by the IDFT module to obtain a signal for transmission to the receiving end, as shown in Equation 2.

<maths><img file="TW200742382A_D0003.tif" /></maths>

<i>F</i>_<i>NxN</i>Refers to a DFT matrix of size "N" used to convert a signal in a frequency area into a signal in a time area. The size of the DFT matrix can be controlled for a specific purpose. By including an inserted cyclic prefix A, the transmission signal "y" generated by this method is transmitted. A method for generating a transmission signal by adapting the above methods is called the SC-FDMA scheme.

A related technology hybrid ARQ (HARQ) scheme will now be explained. Figure 5 shows a method of implementing HARQ for the downlink physical layer of a radio packet communication system.

As shown in Figure 5, the base station determines a terminal that wants to receive packets and information, such as a type of packet for transmission to the terminal. The base station transmits a high-speed downlink control channel (HS-SCCH) to notify the terminal of corresponding information, such as coding rate, modulation method, and data volume.

The base station then transmits the corresponding data packet via the high-speed downlink shared channel (HS-DSCH) at the time of an associated downlink control channel. The corresponding terminal receives the downlink control channel, identifies the type of packet to be transmitted and a transmission time point, and receives the corresponding packet. The terminal then attempts to decode the received packet data.

If the packet data is successfully decoded, the terminal transmits an ACK signal to the base station. The base station receives the ACK signal, detects the successful packet transmission, and transmits the next packet.

If the packet data is not successfully decoded, the terminal transmits a NACK signal to the base station. The base station receives the NACK signal and detects unsuccessful packet transmission.

The base station can transmit the same data according to the same packet type, or transmit a new packet type at an appropriate point in time. The terminal uses various schemes to combine the retransmitted packet with a previously received but undecoded packet to perform decoding again.

A random access channel (RACH) of WCDMA will now be explained. RACH is a transmission channel used to transmit data with a short length through the uplink.

RACH is used to transmit several RRC messages, such as RRC connection request messages, cell update messages, or URA update messages. The logical channels including CCCH (shared control channel), DCCH (dedicated control channel) and DTCH (dedicated traffic channel) are mapped to RACH. RACH is mapped to a physical channel, such as PRACH (Physical Random Access Channel).

Figure 6 shows an example of a typical PRACH. As shown in Figure 6, the uplink physical channel PRACH envelope includes a preamble part and a message part.

The preamble part implements a power ramp function to adjust the appropriate transmission power for message transmission; and a function to prevent message collisions among several terminals. The message part performs a function for transmitting a MAC PDU (Protocol Data Unit) from a MAC to a physical channel.

When the MAC layer of the terminal instructs a PRACH to be transmitted to a physical layer of a terminal, the physical layer of the terminal selects an access slot and a signature to transmit a PRACH preamble for uplink. The preamble can be transmitted during an access slot interval having a length of 1.33 milliseconds. The preamble selects and transmits one of sixteen types of signatures up to a certain length of the initial part of one of the access slots.

Once the terminal transmits the preamble, the base station can transmit a response signal via the downlink physical channel AICH (Acquisition Indicator Channel). The base station uses a response signature transmitted via AICH to transmit an acknowledgment (ACK) or negative response (NACK) to the terminal.

When receiving the ACK, the terminal transmits the message part. Conversely, when receiving a NACK, the MAC layer of the terminal instructs a PRACH to be retransmitted to the physical layer of the terminal after an appropriate time. If the response corresponding to the transmitted preamble is not received, the terminal transmits a new preamble after a designated access slot using a higher power level than the previous preamble.

The response to the RACH preamble has been explained above. Furthermore, data or control signals can be transmitted from the base station to the terminal. The control signal transmitted from the base station to the terminal may include downlink scheduling information, uplink scheduling grant, or response information transmitted from the terminal to a RACH preamble.

Now it will be explained that the response information of the RACH preamble transmitted by the base station is explained. When receiving a RACH preamble transmitted from the terminal, the base station can transmit response information.

The response information transmitted from the base station may include an adjustment value of time synchronization, such as a time advance (TA). An OFDM system should match an uplink time synchronization between the terminal and the base station.

If the time synchronization is not matched, the uplink data transmission of one of the terminals may cause interference with the data transmission of another symbol or another user, thereby increasing the error rate. Therefore, the base station receives the RACH preamble from the terminal and calculates the TA of the terminal to indicate the TA to the terminal.

The terminal uses the received TA to reset and synchronize with the time of the base station to accurately match the time synchronization with the base station. The terminal can use the uplink radio resource allocation information included in the response information to transmit data to the base station.

In the related technical method using RACH, the terminal transmits the RACH preamble to the base station, and the base station then transmits response information including TA for the preamble, uplink radio resource allocation information, and other information to terminal. Therefore, the terminal uses TA to reset the time synchronization with one of the base stations to transmit data to the base station using uplink radio resource allocation information.

However, a time performance may not be sufficient to properly match the uplink time synchronization between the terminal and the base station. For example, a fast-moving terminal appears to be difficult to match a precise time synchronization through a single RACH preamble transmission and a single TA response. Data transmission from a fast mobile terminal may fail and may cause interference with transmissions from other terminals.

An object of the present invention is to provide a method for retransmitting a transmission channel preamble in a mobile communication system, which is used for faster uplink time synchronization between a terminal and a base station.

In one aspect of the present invention, a method for scheduling radio resources in a mobile communication system is provided. The method includes transmitting a transmission channel preamble, receiving a response to the transmission of the transmission channel preamble, and retransmitting one of the transmission channel preamble and using the allocated radio resource to transmit information, wherein if the response is When a request for retransmission of the transmission channel preamble is included, the transmission channel preamble is retransmitted, and if the response includes an indication of allocated radio resources, the information is transmitted.

It has been covered that the transmission channel is a random access channel (RACH). It further covers that the response to the transmission of the preamble of the transmission channel is a control signal.

It has been covered that the transmission channel preamble is associated with one of the following: an RRC connection request, a cell update, submission, a radio resource request, and the maintenance of time synchronization. It is further covered that retransmission of the transmission channel preamble includes the use of a signature included in the response. Preferably, retransmitting the transmission channel preamble includes including a retransmission indicator in the retransmitted preamble.

In another aspect of the present invention, a method for scheduling radio resources in a mobile communication system is provided. The method includes receiving a transmission channel preamble code, determining whether the preamble code meets a predetermined standard, and transmitting a response to the transmission channel preamble code, wherein if it is determined that the preamble code does not meet the predetermined standard, the response includes A request for retransmission of the preamble of the transmission channel, and if it is determined that the preamble meets a predetermined standard, the response includes an indication that radio resources have been allocated.

The covered predetermined standard includes at least one of the following: the error rate of a time synchronization or the number of times used to implement the time synchronization. It has further covered that the error rate of time synchronization is 80% of that of perfect synchronization.

It has been covered that the transmission channel is a random access channel (RACH). It further covers the transmission of the response to the preamble of the transmission channel including the transmission of a control signal.

It is covered that if it is determined that the preamble does not meet the predetermined criteria, the response further includes a signature for retransmitting the preamble of the transmission channel. It further covers that the transmission channel preamble is associated with one of the following: an RRC connection request, a cell update, submission, a radio resource request, and the maintenance of time synchronization. Preferably, the method further includes receiving a retransmitted transmission channel preamble if it is determined that the preamble does not meet a predetermined standard, and identifying one of the following: the retransmitted transmission channel preamble and a Retransmit the retransmission indicator in the preamble of the transmission channel.

In another aspect of the present invention, a method for scheduling radio resources in a mobile communication system is provided. The method includes a mobile communication terminal, which transmits a transmission channel preamble; a network, which determines whether the preamble meets a predetermined standard, and the network transmits a response to the transmission channel preamble, if it determines When the preamble does not meet the predetermined standard, the response includes a request to retransmit the transmission channel preamble, and if it is determined that the preamble meets the predetermined standard, the response includes an instruction to allocate radio resources, and if the response is If a request to retransmit the preamble of the transmission channel is included, the mobile communication terminal retransmits the preamble of the transmission channel, and if the response includes an indication of allocated radio resources, the allocated radio resources are used to transmit information.

It has been covered that the transmission channel is a random access channel (RACH). It further covers that the response to the transmission of the preamble of the transmission channel is a control signal.

It has been covered that the transmission channel preamble is associated with one of the following: an RRC connection request, a cell update, submission, a radio resource request, and the maintenance of time synchronization. It has been further covered that the predetermined standard includes at least one of the following: an error rate of time synchronization or the number of times used to perform time synchronization. Preferably, the error rate of time synchronization is 80% of perfect synchronization.

The foregoing and other objectives, features, aspects and advantages of the present invention will be better understood from the following detailed description of the present invention with reference to the accompanying drawings.

The following description will propose additional features and advantages of the present invention, and part of them will be understood from the description, or can be learned by the implementation of the present invention. It should be understood that the above general description and the following detailed description of the present invention are exemplary and explanatory, and are intended to provide further explanations of the patent application scope of the present invention.

Those skilled in the art will also be able to understand these and other exemplary embodiments from the following detailed description of the specific embodiments with reference to the accompanying drawings. The features herein are not limited to any specific embodiments disclosed.

The present invention will now be explained in detail with reference to the drawings. The invention is implemented in a mobile communication system (such as E-UMTS). However, the present invention can be applied to other communication systems operating in accordance with other specifications.

The present invention provides a method by which when a terminal uses a RACH to transmit a RACH preamble to a base station, a base station uses a specific control signal to request a retransmission of a RACH preamble to the terminal. The terminal receives the specific control signal, and then retransmits the RACH preamble to the base station according to the corresponding control signal. Preferably, the specific control signal is response information for the RACH preamble.

Figure 7 is a flow chart showing the preamble retransmission method in the mobile communication system according to the present invention, in which a RACH preamble is retransmitted by a terminal in response to a request from the base station. As shown in Figure 7, the terminal transmits a RACH preamble to the base station for the purpose of RRC connection request, cell update, delivery, radio resource request or maintenance of time synchronization with the base station (S10).

The base station compares the received RACH preamble with a predetermined specific standard (such as the error rate of time synchronization or the number of times of time synchronization) to determine whether the reception of the RACH preamble meets the specific standard. For example, if the error rate of time synchronization with the base station exceeds 80%, the base station determines that an additional time synchronization reset is required. The base station can also request a time synchronization verification procedure that is reset by more than two time synchronization resets.

Based on the comparison, the base station determines that the received RACH preamble does not meet the standard or requires a verification (S11). Therefore, the base station does not include information such as uplink radio resource allocation in the response information to the RACH preamble received from the terminal (S12).

The response information only includes TA and a retransmission indicator. The retransmission indicator informs the terminal to retransmit the RACH preamble. The response information may also include only TA.

The base station may include additional information in the response information, such as the RACH preamble signature and the RACH timing, and the terminal uses both of them to retransmit the RACH preamble. The RACH timing indication is used to use a specific frequency and a specific time of RACH.

When receiving a request for retransmission of the RACH preamble from the base station, the terminal retransmits the RACH preamble to the base station (S13). The terminal uses the signature included in the response information transmitted from the base station as a RACH preamble signature.

In this way, the base station can recognize that the terminal is retransmitting the RACH preamble based on the signature. Similarly, a retransmission indicator can be used to inform the base station of the retransmission of the RACH preamble from the terminal.

The base station compares the received retransmitted RACH preamble from the terminal with preset specific standards (such as the error rate for time synchronization or the number of times used for time synchronization) to determine whether the retransmitted RACH preamble meets the standard (S14 ). When it is determined that the retransmission of the RACH preamble complies with the standard or the verification of the RACH preamble is completed, the base station transmits response information, which includes TA, UE Id, and uplink radio resource allocation information (S15). If the terminal uses RACH to maintain time synchronization, the response information may only include TA.

The terminal uses the TA reset included in the response information to synchronize with the time of the base station, and uses uplink radio resources to transmit data to the base station (S16). If the terminal uses RACH to maintain time synchronization, step S16 may not be performed.

As described herein, when a terminal transmits a RACH preamble to a base station to use a RACH, a base station will receive the RACH preamble with a preset specific standard (such as error rate or time for time synchronization). The number of synchronization) comparison. If the RACH preamble does not meet the standard, the base station requests the retransmission of the RACH preamble to the terminal to reduce the probability of data transmission failure due to inaccurate time synchronization and reduce interference with transmission by other terminals.

Since the present invention can be embodied in several forms without departing from its spirit or basic characteristics, it should also be understood that the above specific embodiments are not limited to any details previously described, but should be broadly regarded as accompanying Attached are within the scope of the definition of the scope of patent application. Therefore, all changes and modifications that fall within the measurement and limits of the scope of the patent application, or the equivalent of these measurements and limits, are expected to be covered by the scope of the patent application.

The foregoing specific embodiments and advantages are merely exemplary and should not be regarded as limiting the present invention. This teaching can be easily applied to other types of equipment.

The description of the present invention is intended to demonstrate and does not limit the scope of the patent application. Those who are familiar with this technology will understand many alternatives, modifications and changes. In the scope of the patent application, when the quotation function is implemented, the component-plus-function clause is intended to cover the structure described here, and is not only structurally equivalent but also an equivalent structure.

<p>UE. . . terminal</p>

The accompanying drawings included herein provide a further understanding of the present invention, and are incorporated into and constitute a part of this specification. The accompanying drawings show specific embodiments of the present invention and together with descriptions are used to explain the principle of the present invention. The features, elements, and aspects of the present invention referenced by the same numbers in different figures represent the same, equivalent or similar features, elements, or aspects according to one or more specific embodiments.

Figure 1 shows the network structure of the E-UMTS of the mobile communication system, which can be applied to both the related technology and the present invention.

Figure 2 shows the various layers of the control plane of the radio protocol.

Figure 3 shows the various layers of the user plane of the radio protocol.

Figure 4 shows the structure of the transmitter using the DFT-S-OFDM method.

Figure 5 shows the method used to implement HARQ in the downlink physical layer of the radio packet communication system.

Figure 6 shows an example of a typical PRACH.

Figure 7 shows a flow chart of the preamble retransmission method in the mobile communication system according to the present invention.