WO2008037170A1 - A method for maintaining upward synchronization and a system thereof - Google Patents

Abstract

A method for maintaining upward synchronization in a long term evolution system maintains upward synchronization between the UE and the Node B and reduces the spending of the system resource in the TDD LTE system. The Node B receives the upward information transmitted from the UE; the Node B determines the timing advance TA according to the received upward information and send down the TA adjusting message to the UE just when the TA is greater than the threshold value; the UE updates the local upward transmitting TA to maintain upward synchronization according to the TA adjusting message. In addition, the UE which is in the state of no data flow interaction transmits the upward pilot signal to the Node B in the designated time-frequency resource via the existing upward resource. There is also a system thereof.

Description

 Method and system for maintaining uplink synchronization

 The present invention relates to the field of communications, and in particular to a method and system for maintaining uplink synchronization. Background technique

 In the Long Term Evolution (LTE) solution of the 3rd generation mobile communication system, the UE and the base station (Node B) may be out of synchronization due to the mobile device or the sudden strong interference of the user equipment (UE). However, the maintenance of the uplink synchronization state is a basic condition for the UE to be able to communicate normally with the Node B.

 At present, many companies have proposed corresponding solutions, a competitive-based solution, and designed an uplink synchronous random access channel, which is mainly used for uplink shared channel resource applications. When the UE has uplink signaling, the uplink signaling is used as the measurement signal of the uplink synchronization hold; when the UE does not send the uplink signaling, an uplink synchronous random access signal is triggered as the measurement signal of the uplink synchronization hold. The problem with this method is that when the UE does not transmit uplink signaling, the measurement signal held as the uplink synchronization is based on contention. The disadvantages of the competition-based approach are: the competition will bring collisions, resulting in a decline in detection performance; the transmitting UE generally uses open-loop power control for better access performance, transmitting signals with as high a power as possible, When the carrier is used, it is easy to cause interference to neighboring cells.

 A scheduling-based solution is designed with a new scheduling-based physical channel that transmits the UE's reference signal on a specified time-frequency resource. The problem with this approach is that it increases the system resource overhead and only transmits the reference signal in each subframe, resulting in low resource utilization. Summary of the invention

 The embodiments of the present invention provide a method and system for maintaining uplink synchronization. In the TDD LTE system, the UE maintains uplink synchronization with the Node B and reduces the overhead of system resources as much as possible.

 A method for maintaining uplink synchronization in a long term evolution system includes the steps of:

The UE in the non-uplink data transmission state sends an uplink signal to the Node B at the specified time-frequency location by using the existing uplink resource; The Node B determines the timing advance TA according to the received uplink pilot signal, and instructs the UE to maintain uplink synchronization according to the TA.

 In the state of no data traffic interaction, the Node B notifies the UE to periodically send an uplink pilot signal in a specified time-frequency resource by using a control signaling or a broadcast message.

 Node B determines TA includes steps:

 Node B intercepts a part of the time domain sequence according to the original TA at a specified time, and uses the time domain sequence to demodulate the uplink pilot sequence;

 And performing linear correlation calculation on the uplink pilot sequence and the known frequency domain sequence, and determining uplink timing information according to the calculated value;

 Determining, according to the uplink timing information, a time point at which the Node B instructs the UE to send a pilot signal

TA.

 Moving a starting sampling point from a sampling point near the specified time, and acquiring a signal sequence of a complete signal length from the partial time domain sequence at each starting sampling point, and from each of the signal sequences The uplink pilot sequence is demodulated and a plurality of the calculated values are obtained, and the uplink timing information is determined according to the largest calculated value. '

 When there is only downlink data transmission in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink signaling sent by the UE.

 When there is only uplink data transmission in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink information sent by the UE.

 The Node B further compares the TA with the threshold, and sends a TA adjustment message to the UE only when the TA is greater than the threshold, and the UE updates the uplink transmission TA according to the TA adjustment message. 'A base station, including:

 a unit for receiving an uplink pilot signal transmitted by a UE in an uplink data-free state; a unit for determining a timing advance TA according to the received uplink pilot signal;

 And means for indicating that the UE keeps uplink synchronization according to the TA sending TA adjustment message. Also includes:

For comparing the TA with the threshold, and sending the TA adjustment message only when the TA is greater than the threshold A unit indicating that the UE maintains uplink synchronization.

 A communication system comprising:

 The user equipment UE sends the uplink pilot signal in the specified time-frequency resource through the existing uplink channel when the UE is in the no-data traffic interaction state;

 The Node B is configured to determine a timing advance TA according to the received uplink pilot number, and according to the TA indication, the UE maintains uplink synchronization.

 The Node B includes:

 a unit for receiving an uplink pilot signal transmitted by a UE in an interactive state without uplink data traffic;

 Means for determining a timing advance TA based on the received uplink pilot signal;

 And means for indicating that the UE keeps uplink synchronization according to the TA sending TA adjustment message. The Node B further includes:

 And means for comparing the TA with the threshold, and sending the TA adjustment message only when the TA is greater than the threshold, indicating that the UE maintains uplink synchronization.

 In the state of no data traffic interaction, the Node B notifies the UE to periodically send an uplink pilot signal in a specified time-frequency resource by using a control signaling or a broadcast message.

 The Node B intercepts a partial time domain sequence according to the original TA in the vicinity of the specified time, and demodulates the uplink pilot sequence from the time domain sequence; and performs the uplink pilot sequence with a known frequency domain sequence. Linear correlation calculation, and determining uplink timing information according to the calculated value; determining TA according to the uplink timing information and a time point when the Node B instructs the UE to send the pilot signal.

 Transmitting a starting sampling point from a sampling point near the specified time, and acquiring a signal sequence of a complete signal length from the partial time domain sequence at each starting sampling point, and from each of the signals The uplink pilot sequence is demodulated in the sequence and a plurality of the calculated values are obtained, and the uplink timing information is determined according to the largest calculated value.

 When there is only downlink data transmission in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink signaling sent by the UE.

When there is only uplink data transmission in the data traffic interaction state, the Node B is sent according to the UE. The line information determines the uplink timing information.

 In the embodiment of the present invention, the uplink synchronization is maintained according to the scheduling manner, and the collision caused by the contention mode is avoided, so that the detection performance is better; the present invention uses the uplink data or the uplink pilot signal to perform the TA in real time or periodically in the Exchanged Traffic state. The detection is performed to avoid occupying additional resources, and the threshold is set for the TA. The synchronization command is issued only when the TA is greater than the threshold, which reduces the excessive resources occupied by the large number of UEs requiring the Node B to issue the synchronization command. In the No Traffic state, the Node B dynamically specifies the time-frequency resources transmitted by the UE, and the Node B measures the corresponding time-frequency resources to obtain the uplink synchronization timing information of the UE, thereby avoiding occupying additional network resources, and the present invention sets a threshold for the TA, only When the TA is greater than the threshold, the synchronization command is issued, which reduces the resources occupied by the Node B to issue too many synchronization instructions. DRAWINGS

 1 is a schematic diagram of state transition in an embodiment of the present invention;

 2 is a structural diagram of a system for maintaining uplink synchronization in an embodiment of the present invention;

 3 is a structural diagram of an apparatus for maintaining uplink synchronization according to an embodiment of the present invention;

 4 is a schematic diagram of allocation of pilot signals under a single antenna according to an embodiment of the present invention;

 FIG. 5 is a schematic diagram of allocation of pilot signals under dual antennas according to an embodiment of the present invention; FIG.

 6 is a basic flowchart of maintaining an uplink synchronization method according to an embodiment of the present invention;

 FIG. 7 is a flowchart of a method for maintaining uplink synchronization during uplink transmission according to an embodiment of the present invention; FIG. 9 is a flowchart of a method for maintaining uplink synchronization when no data is transmitted according to an embodiment of the present invention. detailed description

The embodiment of the present invention provides a method for maintaining synchronization between a UE and a Node B in three situations, that is, using uplink data or an uplink pilot signal to maintain synchronization when there is uplink data transmission; and second, using uplink of feedback information when downlink data transmission exists. The signaling is kept in sync; the third is that the uplink pilot signal is synchronized when there is no information interaction. In LTE, the UE status is divided into LTE__ACTIVE (active) and LTE-IDLE (idle) states according to the provisions of standard protocol 25.813. In the LTE-AC state, it can be divided into two states: Exchange Traffic (data traffic interaction) and No Traffic (no data traffic interaction). In the Exchange Traffic state, data interaction between the UE and the Node B, after data interaction, The UE also keeps the LTE-AC state for a period of time, that is, it is in the No Traffic state. If there is a need for data interaction during this time, the UE will initiate a request in the synchronization state to enter the data interaction state, that is, return to the Exchange Traffic. Status; otherwise the RRC (Radio Resource Control) connection is released, the uplink synchronization is no longer maintained, and the UE enters the LTE_IDLE state. See Figure 1.

 Referring to FIG. 2, the communication system in this embodiment includes a UE and a Node B, where

 The UE performs data interaction with the Node B, and receives an instruction sent by the Node B, and changes a local uplink sending TA (Timing Advance) to maintain synchronization with the Node B. The Node B receives or delivers data, and measures the TA. When the TA is found to exceed a certain threshold, the UE sends an instruction to the UE to instruct the UE to update to maintain synchronization.

 Referring to FIG. 3, the Node B in the communication system of this embodiment includes a receiving unit 301, a measuring unit 302, and a transmitting unit 303.

 The receiving unit 301 receives data from the UE. The measuring unit 302 receives the receiving unit 302 according to the receiving unit 301.

The TA of the UE is periodically measured in the state of No Traffic, and the transmitting unit 303 is started when it is found that the TA exceeds a certain threshold. The sending unit 303 generates a synchronization instruction, instructs the UE to perform synchronization according to the TA of the Node B, and sends the instruction to the UE. In the No Traffic state, a response command is generated and sent to the UE, and the UE is instructed to periodically send the uplink pilot signal. In order to measure the TA.

In TDD LTE, according to the standard protocol 25.814, the pilot signal of the uplink channel is designed as a short block (SB, Short Block), that is, the time length is half of the general OFDM (Orthogonal Frequency Division Multiplexing) signal, and the subcarrier The interval is twice that of a general OFDM signal. The SB includes two types of pilot signals, one is a reference signal for data demodulation, called a DM pilot (Demodulation pilot); the other is a reference signal for uplink channel quality detection, called It is a channel quality indication pilot (CQI pilot, Channel Quantity Indication pilot). DM pilot and UE data transmission The bandwidth corresponds to the CQI pilot and the scheduling bandwidth of the UE. The data transmission bandwidth is included in the uplink scheduling bandwidth and is a subset of the uplink scheduling bandwidth. The Node B measures the CQI pilot transmitted by a certain UE. Selecting an optimal subband in the entire uplink scheduling bandwidth of the UE, indicating that the subband transmits uplink data in the downlink signaling, and the frequency range of the subband is the data transmission bandwidth. This embodiment can achieve the purpose of determining the TA by measuring the CQI pilot.

 4 shows the allocation of pilot signals in the SB when the UE is transmitting in a single antenna in this embodiment, and there are three sets of CQI pilots in the SB, and each group of pilots can support three by code division multiplexing (CDM). UE. It can support up to 9 UE CQI pilots. FIG. 5 shows the allocation of pilot signals in the SB when the UE transmits for 2 antennas in this embodiment. Compared with FIG. 4, the number of DM pilots increases, and the CQI pilot changes to two groups. In this embodiment, the CQI pilot is taken as an example, and the TA is measured according to the CQI pilot in the uplink channel.

 Referring to FIG. 6, in the basic flowchart of maintaining uplink synchronization between the UE and the Node B in this embodiment: Step 601: The UE performs data interaction with the Node B.

 Step 602: When the Node B measures the TA in real time or periodically, and finds that the TA is greater than a certain threshold, step 603 is performed.

 Step 603: The Node B sends a synchronization instruction to the UE, instructing the UE to perform synchronization according to the TA. Step 604: The UE synchronizes according to the TA in the synchronization instruction to maintain uplink synchronization with the Node B, and continues to step 601, and loops back until the UE enters the LTE-IDLE state.

 Referring to FIG. 7, in the embodiment, when the UE is in the Exchanged Traffic mode and the uplink data is transmitted, the method for maintaining the uplink synchronization is as follows:

 Step 701: The UE uploads data to the Node B, and performs uplink information interaction.

 Step 702: The Node B detects the TA according to the pilot signal in the uplink data or the uplink signaling, and determines whether the TA is greater than the threshold value. In this embodiment, if a is preset, then step 703 is performed, otherwise, Continuing the detection, step 702 is performed until the uplink data transmission ends.

Step 703: The Node B generates a synchronization instruction and sends the synchronization instruction to the UE, where the synchronization instruction includes TA information. Step 704: After receiving the synchronization instruction, the UE adjusts the local according to the TA information in the synchronization instruction. The uplink transmission TA, a TA is advanced in advance when the information is uploaded, to maintain uplink synchronization with the Node B.

 Referring to FIG. 8, in the embodiment, when the UE is in the Exchanged Traffic state and the downlink data is transmitted, the method for maintaining the uplink synchronization is as follows:

 Step 801: The Node B sends data to the UE to perform downlink information interaction.

 Step 802: The UE receives data and periodically sends uplink signaling to provide feedback information.

 Step 803: The Node B detects the TA according to the received uplink signaling, and determines whether the TA is greater than the threshold a. If yes, step 804 is performed. Otherwise, the detection is continued, and step 803 is performed until the downlink data transmission ends.

 Step 804: The Node B generates a synchronization instruction and sends the synchronization instruction to the UE, where the synchronization instruction includes TA information. Step 805: After receiving the synchronization command, the UE adjusts the local uplink sending TA according to the TA information in the synchronization command, and advances a TA when the information is uploaded next time to maintain the uplink synchronization with the Node B.

 Referring to FIG. 9, the method for maintaining uplink synchronization when the UE is in the No Traffic state in this embodiment is as follows:

 Step 901: The Node B sends a reply command to the UE by using the control signaling and the broadcast information, and instructs the UE to periodically use the existing channel to send the uplink pilot signal at the specified time point B.

 Step 902: The UE sends uplink signaling at a specified time point B according to the received reply command (the transmission time may be adjusted according to the local original TA).

 Step 903: The Node B starts receiving the uplink pilot signal at the corresponding time point A. The time point A is before the time point B.

Step 904: Intercept a partial time domain sequence in position A, in which a partial time domain sequence (the length of one signal) is further intercepted for the time point A, and a partial time domain sequence is time-frequency processed by FFT (Fast Fourier Transform) Transform, solve the uplink pilot sequence (XX ₂ , . . . Xn , n denotes the sequence number), and use the corresponding frequency domain sequence (Υ, Υ ₂ , ... Υ „ ) and the solved uplink pilot sequence Perform a linear correlation calculation, the formula is: X, X γ , + Χ ₂ X Υ ₂ + ... + Χ" Ϋ _η , record calculation The result. Then, a partial time domain sequence is intercepted for the next time point B, the time point C, and the time point D, and linear correlation calculation is performed. (Time points, B, C, and D are sampling points arranged in order.)

 Step 905: Comparing the calculated knots at the three time points, and finding that the calculation result at the time point C is the largest, the time point C is the current uplink timing information.

 If the calculation result at the time point D is the largest, the time point E needs to be further calculated. If the result at the time point A is greater than the result at the time point B, it means that the time point A is the current uplink timing information, and no further information is needed. The time point C is calculated. '

 Step 906: Determine whether the time difference between the time point B (specified point) and the time point C (the result maximum point) is greater than a, that is, whether the TA is greater than a, and if yes, execute step 907; otherwise, continue to step 902 until the UE exits No Traffic. status.

 Step 907: The Node B generates a synchronization instruction and sends the synchronization instruction to the UE, where the synchronization instruction includes TA information. Step 908: After receiving the synchronization command, the UE adjusts the local uplink sending TA according to the TA information in the synchronization command, and advances a TA when the information is uploaded next time to keep the uplink synchronization with the Node B.

 This situation will occupy a certain amount of uplink pilot resources, but considering the uplink synchronization to keep the signal transmission period longer, the impact on resource occupancy can be ignored. For example, a 5M bandwidth system supports 200 ACTIVE UEs, assuming an uplink scheduling bandwidth of 5M. According to the design of the uplink pilot, one uplink time slot can support 9 CQI pilots (in the case of a single antenna), even if all The UE needs to maintain the uplink synchronization, and the estimation that keeps the uplink synchronization period conservative is generally equal to Is, that is, the uplink synchronization and hold signal of one UE needs to be transmitted every one subframe, and only 1/9 of the CQI pilot resources are occupied. The No Traffic state is a small probability. It is impossible for all UEs to be in the No Traffic state. The actual occupied CQI pilot resources will be less. If the uplink scheduling bandwidth is less than 5M, the resource occupancy rate will be further reduced. Other pilot signals can also be used for detection in the same way.

The embodiment of the invention keeps the uplink synchronization based on the scheduling mode, avoids the performance degradation caused by the competition, does not have the collision caused by the competition, and the detection performance is better. From the perspective of access delay, for the TDD system, the uplink time slot itself is based on scheduling. At the same time, the uplink synchronization needs to be long and is not sensitive to delay, so the signal is only at the scheduled time. On the frequency resource, Therefore, the problem of large delay does not have a large impact, so a higher reliability can be obtained by using a scheduling-based method.

 The embodiment of the present invention detects the TA in real time or periodically according to the uplink data or the uplink pilot signal in the Exchanged Traffic state, avoids occupying additional resources, and sets a threshold for the TA, and only issues a synchronization command when the TA is greater than the threshold. In the embodiment of the present invention, the Node B dynamically specifies the time-frequency resource for the UE to transmit the CQI pilot signal in the No Traffic state, and the NodeB measures the corresponding CQI pilot. The signal can obtain the UE uplink synchronization timing information, avoiding the use of additional network resources, and the UE moving speed is large (>300Km/h) is an uncommon situation. Therefore, the embodiment of the present invention sets the threshold for the TA, only in the TA. When the threshold is greater than the threshold, the synchronization command is issued, which reduces the resources occupied by the Node B to send too many synchronization instructions.

 It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Therefore, it is intended that the present invention cover the modifications and variations of the invention as claimed.

Claims

Rights request An uplink synchronization maintaining method, comprising the steps of:  The user terminal UE in the state of no uplink data transmission uses the existing uplink resource to send an uplink signal to the base station Node B at the specified time-frequency location;  The base station determines the timing advance TA according to the received uplink pilot signal, and according to the TA indication, the user terminal maintains uplink synchronization.  The uplink synchronization holding method according to claim 1, wherein the Node B notifies the UE to periodically send in a specified time-frequency resource by using a control signaling or a broadcast message in a state of no data traffic interaction. Uplink pilot signal.  3. The uplink synchronization holding method according to claim 2, wherein the Node B determines the TA to include the following steps:  Node B intercepts a part of the time domain sequence according to the original TA at a specified time, and uses the time domain sequence to demodulate the uplink pilot sequence;  And performing linear correlation calculation on the uplink pilot sequence and the known frequency domain sequence, and determining uplink timing information according to the calculated value;  Determining, according to the uplink timing information, a time point at which the Node B instructs the UE to send a pilot signal 4. The uplink synchronization holding method according to claim 3, wherein the starting sampling point is moved from a sampling point near the specified time, and the partial time domain sequence is obtained from each of the starting sampling points. Obtaining a signal sequence of a complete signal length, and extracting an uplink pilot sequence from each of the signal sequences and obtaining a plurality of the calculated values, and determining uplink timing information according to the largest calculated value.  The uplink synchronization holding method according to claim 1, wherein when the downlink data transmission is only performed in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink signaling sent by the UE. 6. The uplink synchronization holding method according to claim 1, wherein the data traffic is delivered When there is only uplink data transmission in the inter-state, the Node B determines the uplink timing information according to the uplink information sent by the UE.  The uplink synchronization holding method according to any one of claims 1 to 6, wherein the Node B further compares the TA with a threshold and transmits a TA adjustment message to the UE only when the TA is greater than a threshold. The UE updates the uplink sending TA according to the TA adjustment message.  8. A base station, comprising:  Used for receiving data with no upstream data interaction ^  Means for determining a timing advance TA based on the received uplink pilot signal;  And means for indicating that the UE keeps uplink synchronization according to the TA sending TA adjustment message. The base station according to claim 8, further comprising:  It is used to compare the TA with the threshold, and only sends a TA adjustment message when the TA is greater than the threshold to indicate that the UE maintains uplink synchronization.  10. A communication system, comprising:  The user equipment UE sends the uplink pilot signal in the specified time-frequency resource through the existing uplink channel when the UE is in the no-data traffic interaction state;  The Node B is configured to determine a timing advance TA according to the received uplink pilot signal, and according to the TA indication, the UE maintains uplink synchronization.  The communication system according to claim 10, wherein the Node B comprises: a unit for receiving an uplink pilot signal sent by a UE that is in an interactive state without uplink data traffic;  Means for determining a timing advance TA based on the received uplink pilot signal;  And means for indicating that the UE keeps uplink synchronization according to the TA sending TA adjustment message. The communication system according to claim 11, wherein the Node B further comprises: comparing the TA with a threshold, and sending a TA adjustment message to indicate that the UE keeps uplink when the TA is greater than the threshold Synchronized unit. The communication system according to claim 10, wherein, in a state of no data traffic interaction, the Node B notifies the UE of the specified time-frequency resource by using a control signaling or a broadcast message. The uplink pilot signal is periodically transmitted.  The communication system according to claim 13, wherein the Node B intercepts a partial time domain sequence in the vicinity of the specified time according to the original TA, and demodulates the uplink pilot sequence from the time domain sequence. And performing linear correlation calculation on the uplink pilot sequence and the known frequency domain sequence, and determining uplink timing information according to the calculated value; determining the TA according to the uplink timing information and a time point when the Node B instructs the UE to send the pilot signal.  15. The communication system according to claim 14, wherein: said starting a sampling point is moved from a sample point near said specified time, and said partial time domain sequence is obtained at each starting sampling point And acquiring a signal sequence of a complete signal length, and demodulating the uplink pilot sequence from each of the signal sequences and obtaining a plurality of the calculated values, and determining uplink timing information according to the largest calculated value.  The communication system according to claim 10, wherein, when only the downlink data is transmitted in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink signaling sent by the UE.  The communication system according to any one of claims 10 to 16, wherein when the uplink data is transmitted only in the data traffic interaction state, the Node B determines the uplink timing information according to the uplink information sent by the UE.