WO2007045127A1

WO2007045127A1 - Uplink signal transmission method for user equipment and timing synchronization method thereof

Info

Publication number: WO2007045127A1
Application number: PCT/CN2005/001735
Authority: WO
Inventors: Lianbin Xiao; Meiling Ding
Original assignee: Zte Corporation
Priority date: 2005-10-21
Filing date: 2005-10-21
Publication date: 2007-04-26
Also published as: CN101243622A; CN101243622B

Abstract

An uplink signal transmission method for a user equipment and a timing synchronization method thereof include the steps of: estimating an downlink channel impulse response h by the user equipment; determining the conjugation of h; preparing a uplink signal to be transmitted; filtering said signal by using a coefficient matched with h the matched filter has a conjugation of h; determining whether the traffic channel of the user equipment adopts pre-rake technique, and deciding whether the transmission timing is adjusted according the determining result; transmitting the timing-adjusted or unadjusted uplink signal to a base station by the user equipment; making correlation or FFT transformation for uplink pilot by the base station finding peak position, and performing uplink synchronization. Present invention can make the base station receive a great amount of energies of a certain multipath tap, improve uplink synchronous detection performance, thereby improve uplink synchronization performance.

Description

Uplink signal transmission method of user equipment and method for timing synchronization thereof

The present invention relates to the field of digital mobile communications, and more particularly to a method for transmitting uplink signals of user equipment and a method for timing synchronization in a split-duplex code division multiple access (TD-SCDMA) communication system. Background technique

Due to the characteristics of the wireless channel, the wireless signal needs to be reflected and scattered by multiple objects around the transmitting end to form multiple signal branches. These signal branches will be extended to different time delays to form different impact responses, which is multipath. Delay extension. In this way, the energy of the transmitted signal will be dispersed to different delays, which reduces the energy of the impulse response over a certain delay, which makes the estimation of the timing at the receiving end difficult. Since the split-duplex communication system uses the same carrier frequency in the uplink and downlink, the channels through which the uplink and downlink signals pass are the same. According to the principle of reciprocity, the uplink and downlink impact responses are identical. Therefore, the impulse response of the downlink channel can be estimated by the impulse response of the uplink channel, or conversely, the impulse response of the uplink channel can be estimated by the impulse response of the downlink channel.

The Pre-rake technique is a technique that uses the impulse response of the upstream channel to estimate the impulse response of the downlink channel and simplifies the downlink reception by adjusting the downlink transmission signal. The specific implementation process is as follows.

The base station receives the signal transmitted by the ordinary user, and obtains the characteristics of the uplink channel by estimating the uplink pilot. The uplink channel estimation result of the CDMA (Code Division Multiple Access) system is some time-varying taps. The base station collects and combines the tap signals on different delays through joint detection or rake reception to obtain better effects than single-path reception. However, the signal transmitted by the ordinary CDMA transmitter arrives at the receiver because the energy is diffused to different delays, so that the energy on the effective tap is lower than the energy of the transmitted signal. Due to the time-varying nature of the Rayleigh channel, the energy on the tap is constantly changing. The smaller energy on the tap after Rayleigh fading is likely to be fading and being overwhelmed by noise, making tap detection difficult. Pre- rake adjusts the transmitted signal so that the adjusted signal can pass through the channel and the peak of the original signal can appear at the receiver. That is A certain tap of the receiver estimate will have a large value, which is larger than the energy on the surrounding delay, and concentrates the energy of most of the original signal, so that the receiver can only estimate the channel of the peak tap. And demodulation, greatly reducing the complexity of the receiver. The method of adjusting the peak of the receiver is to filter the original signal to match the channel impulse response. For example: When the channel impulse response is h, the matched filter is the common h of h, and the downlink signal is filtered by this filter before being transmitted and then transmitted. After such a specially processed downlink signal is converged with the channel impulse response through the channel, the effect is equivalent to a rake reception of the original signal, so this technique is called Pre-rake technology.

The principle of the Pre-rake transmitter is shown in Figure 1. As seen from the figure, the downlink signal is filtered before transmission, so that the energy distribution of the downlink transmitted substitute signal after passing through the channel is concentrated in one or several On the chip, thereby reducing the complexity of the user equipment. For the user equipment, whether the base station has the Pre-mke function does not affect the normal receiving function of the user equipment, and the base station adopts the Pre-rake technology to adopt a simpler user receiving device.

On the other hand, for wireless communication systems, especially TD-SCDMA (Time Division Duplex Code Division Multiple Access) communication systems. Due to the different distance between the user equipment and the base station, accurate uplink alignment synchronization needs to be established in order to correctly demodulate the information. The accuracy of synchronization is required to be less than one chip.

Depending on the channel characteristics, the delay of different paths for uplink synchronization remains relatively stable, but the amplitude of multipath changes abruptly with time, which makes uplink synchronization difficult. Since the uplink synchronization needs to determine the timing of the uplink synchronization according to the path position with the strongest intensity, the synchronous CDMA system can adjust the uplink transmission of the user equipment according to the timing of the signal. The base station determines the uplink timing according to the maximum tap, and the signal transmitted by the common user equipment is usually not representative because of the dispersion and fading of the multipath energy, and it is necessary to find multiple effective ones. The "center of gravity" of the path represents the characteristics of the entire channel, and the energy in the entire demodulation window is combined as much as possible by synchronization.

Therefore, the existing uplink signal transmission method of the user equipment does not easily implement uplink synchronization detection for the base station side.

Summary of the invention

The technical problem to be solved by the present invention is to provide a user equipment for transmitting uplink signals. The shooting method improves the base station synchronization performance by using the pre-Rake technology for the user equipment.

The present invention provides an uplink signal transmission method for a user equipment, which is used in a time division duplex code division multiple access communication system, and the method includes the following steps:

The user equipment estimates the downlink channel impulse response h;

The user equipment determines the conjugate of h according to the downlink channel impulse response h;

The user equipment prepares an uplink signal to be transmitted;

The user equipment performs filtering on the uplink signal to be transmitted that matches the channel impulse response h, and the matched filter is a common conjugate of h;

The user equipment transmits the uplink signal filtered by the filter to the base station through the uplink channel.

The present invention also provides a method for timing synchronization of an uplink signal transmitted by a user equipment, which is used for splitting a duplex code division multiple access communication system, and the method includes the following steps:

The user equipment estimates the downlink channel impulse response h _;

The user equipment prepares an uplink signal to be transmitted;

The user equipment transmits the uplink signal filtered by the filter to the base station through the uplink channel;

The base station performs correlation or Fourier transform on the pilot of the uplink signal to find a peak position;

According to the peak position, for the synchronous code division multiple access system, the base station transmits a fast physical access channel signal, and the user equipment is required to adjust the uplink transmission timing according to the determined adjustment amount to compensate for the path delay. For the asynchronous code division multiple access system, The base station adjusts the uplink reception timing.

The uplink signal may include an uplink synchronization signal and an uplink service signal, and the uplink channels respectively correspond to an uplink synchronization channel and an uplink traffic channel.

The uplink signal may also include only an uplink synchronization signal, and the uplink channel is an uplink synchronization channel. In this case, the user equipment transmits the filtered uplink signal to the base station by using an uplink channel, and the method includes the following steps:

The user equipment determines the volume of h and h collocated according to the common channel of the downlink channel impulse response h and h. Product

The user equipment determines a maximum value of the convolution of the h and h conjugates;

The user equipment determines the timing adjustment amount according to the maximum value of the convolution of the common sum of h and h; the user equipment adjusts the uplink transmission timing of the filtered uplink signal according to the timing adjustment amount;

The user equipment transmits the time-adjusted uplink signal to the base station through the uplink channel.

The determining, by the user equipment, the timing adjustment amount according to the maximum value of the convolution of h and h, may include the following steps:

Setting a position p corresponding to the maximum value is a possible peak position of the base station side estimated by the user equipment in advance;

The filtered uplink signal transmission timing is advanced by Lp/2", where L" points to the next integer operation.

The present invention proposes a Pre-mke method for uplink channels, particularly uplink synchronization channels. The user terminal equipment detects downlink pilots or other beacon channels, and uses Pre-rake technology to adjust the uplink channel, especially the uplink synchronization channel, so that the base station receives a certain multipath tap to concentrate most of the energy, thereby improving uplink synchronization. The purpose of detecting performance.

BRIEF abstract

1 is a schematic diagram of signal transmission of a base station using Pre-rake technology in the prior art; FIG. 2 is a schematic diagram of signal transmission using Pre-mke technology for a user equipment according to the present invention; FIG. 3 is a flowchart of an implementation of the present invention;

4 is a schematic diagram showing the effect of applying a better channel impulse response after using the present invention; FIG. 5 is a schematic diagram showing the effect of applying a better channel impulse response convolution after using the present invention;

6 is a schematic diagram showing the effect of applying a poor channel impulse response after the present invention; FIG. 7 is a schematic diagram showing the effect of applying a poor channel impulse response convolution after the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Uplink synchronization is a very critical process and the basis for subsequent communications, so how to improve the performance of uplink synchronization is a very important issue. For the time division duplex communication system, since the uplink channel impulse response and the downlink impulse response have strong correlation, the user equipment can estimate the downlink channel impulse response and obtain an approximate uplink channel impulse response. Thus, if the user equipment adjusts the transmitted signal through Pre-mke, after the adjusted signal is convolved through the channel, most of the transmitted energy is concentrated on one (or some) of the taps. Even after fading, some taps still have higher energy. The impact response on these taps is significantly stronger than other taps. Since the base station determines the uplink timing according to the maximum tap, adjusting the transmission signal by Pre-mke makes it easier for the base station to distinguish the timing information, thereby making the uplink synchronization performance better.

Therefore, the core idea of the present invention is: The Pre-mke technology adopted is not on the base station side, but uses Pre-mke technology on the user equipment.

Also, unlike the prior art, the purpose of the Pre-mke technique of the present invention is not to reduce the complexity of the user equipment, but to improve the performance of the uplink synchronization.

Therefore, the present invention proposes a method of using Pre-rake on an uplink channel, particularly an uplink synchronization channel. The user terminal equipment detects downlink pilots or other beacon channels, and uses Pre-mke technology to adjust the uplink channel, especially the uplink synchronization channel, so that the multipath taps received by the base station concentrate most of the energy taps to improve. The purpose of uplink synchronization detection performance.

3 is an example of the above-mentioned line synchronization signal s(t), and the specific implementation steps of the present invention are as follows: Step 301: User equipment estimates i-|downstream channel impulse response h;

Step 302: The user equipment determines the conjugate of h according to the downlink channel impulse response h. Step 303: The user equipment prepares an uplink synchronization signal s(t) to be transmitted _.

Step 304: The user equipment performs filtering on the uplink synchronization signal s(t) to be transmitted, which is matched with the channel impulse response h, and the matched filter is a common conjugate of h;

Step 305: Determine whether to adjust the transmit quota according to whether the user equipment service channel adopts the pre-rake technology. If yes, go to step 307, otherwise go to step 306; Step 306: The user equipment responds according to the downlink channel impulse The total of h and h, the convolution of h and h conjugates is determined; the user equipment finds the maximum value of the convolution of the h and h conjugates, the maximum value The corresponding position p is a possible peak position of the base station side estimated by the user equipment in advance; the uplink synchronization signal timing of the matched filter is advanced [p / 2", where L" points to the next integer step 307: the user equipment will The matched filtered uplink synchronization signal s(t) is transmitted to the base station via the timing adjustment or the unadjusted.

Step 308: The base station correlates or performs FFT transformation on the uplink pilot according to the uplink synchronization process, and finds a peak position, where the location is an uplink timing including a path delay.

Step 309: For the synchronous CDMA system, the base station transmits a fast physical access channel signal, and the user equipment is required to adjust the uplink transmission timing to compensate for the path delay. For the asynchronous CDMA system, the base station adjusts the uplink reception timing.

Step 310: Synchronize the CDMA system, and the user equipment adjusts the timing again on the basis of the original adjustment according to the requirements of the base station, and the adjustment amount is determined by the base station; the asynchronous CDMA system user equipment does not need any operation. Uplink synchronization is completed.

For the step 306, only one embodiment of the timing adjustment algorithm is known to those skilled in the art. Regardless of how the timing adjustment algorithm is selected, the timing adjustment can be determined as long as the maximum value of the convolution is based on h and h. The quantity should be covered by the scope of this patent.

It can be seen that the focus of the present invention is that the user equipment transmits the uplink signal differently from the existing mode, and after the uplink signal is transmitted to the base station, the base station can implement the uplink synchronization by using the existing receiving synchronization process, and simultaneously improve. Synchronization performance.

After the user equipment adopts the pre-rake technology to adjust the transmit signal, the uplink signal energy that reaches the base station through the channel is concentrated on one or several taps, which greatly increases the energy of the received strong path, and the synchronization performance is also improved accordingly. . The correlation results show that the more the number of channel taps, the more dispersed the tap energy, the greater the gain obtained by the pre-mke technique. The better channel impulse response and convolution effects of the present invention are shown in Figures 4 and 5, respectively. In the case where the number of hoes is small and the dispersion of the impact response position distribution is poor, the channel impulse response before convolution and the channel impulse response after convolution are shown in Fig. 6 and Fig. 7, respectively. We can see that the impact response after convolution is still significantly improved compared to the original shock response before convolution. Since the user equipment adopts pre-rake does not affect the communication function of the base station and other users, after the uplink synchronization channel adopts the pre-rake technology, even if the traffic channel does not adopt the pre-mke technology, by adjusting the timing of the user equipment, Not only does it still support normal base station synchronization, but also uplink synchronization performance. Improved with pre-mke technology

Claims

Claim

A method for transmitting uplink signals of a user equipment, for a time division duplex code division multiple access communication system, characterized in that the method comprises the following steps:

The user equipment estimates a downlink channel impulse response h;

The user equipment prepares an uplink signal to be transmitted;

The user equipment performs filtering on the uplink signal to be transmitted to match the channel impulse response h, and the matched filter is a common conjugate of h;

2. The method according to claim 1, wherein the uplink signal comprises an uplink synchronization signal and an uplink service signal, and the uplink channels respectively correspond to an uplink synchronization channel and an uplink traffic channel.

3. The method according to claim 1, wherein the uplink signal is an uplink synchronization signal, and the uplink channel is an uplink synchronization channel.

The method of claim 3, wherein the step of the user equipment transmitting the filtered uplink signal to the base station through the uplink channel comprises the following steps:

The user equipment determines the convolution of h and h according to the common channel of the downlink channel impulse response h and h;

The method according to claim 4, wherein the determining, by the user equipment, the timing adjustment amount according to the maximum value of the convolution of h and h, comprises the following steps:

Setting the position p corresponding to the maximum value is possible for the base station side estimated by the user equipment in advance Peak position

A method for timing synchronization of an uplink signal transmitted by a user equipment, which is used for splitting a duplex code division multiple access communication system, characterized in that the method comprises the following steps:

The user equipment estimates a downlink channel impulse response h;

The user equipment prepares an uplink signal to be transmitted;

The method according to claim 6, wherein the uplink signal comprises an uplink synchronization signal and an uplink service signal, and the uplink channels respectively correspond to an uplink synchronization channel and an uplink traffic channel.

The method according to claim 6, wherein the uplink signal is an uplink synchronization signal, and the uplink channel is an uplink synchronization channel.

The method according to claim 8, wherein the step of the user equipment transmitting the filtered uplink signal to the base station through the uplink channel comprises the following steps:

The user equipment determines the timing adjustment amount according to the maximum value of the convolution of the common sum of h and h; the user equipment adjusts the filtered uplink signal according to the timing adjustment amount. Line transmission timing

10. The method according to claim 9, wherein the step of determining, by the user equipment, the amount of adjustment according to the maximum value of the convolution of h and h, comprising the following steps:

The filtered uplink signal transmission timing is advanced by LP / 2", where L" points to the next integer operation.