WO2009086670A1

WO2009086670A1 - Method and equipment for mapping a pilot

Info

Publication number: WO2009086670A1
Application number: PCT/CN2007/003961
Authority: WO
Inventors: Dong Li; Xiaolong Zhu
Original assignee: Alcatel Shanghai Bell Co., Ltd.; Alcatel Lucent
Priority date: 2007-12-29
Filing date: 2007-12-29
Publication date: 2009-07-16
Also published as: CN101911579A

Abstract

A method and equipment for mapping a pilot in a base station, to solve the problem that a pilot mode is not rule on the transmitting antenna in a trucked communication, the method including: generating at least a pilot sequence; mapping said at least a pilot sequence on the resource of time and frequency, making the interval of neighboring pilot of the symbol rule. The invention can use a new pilot mode to avoid the operation of perforation and cutting-off, and improve greatly the performance of demodulation and decoding.

Description

Method and device for mapping pilots

Technical field

The present invention relates to a communication technique, and more particularly to a method and system for mapping pilots capable of improving data mapping performance and channel estimation performance. Background technique

In the IEEE 802.16e (i.e., mobile WiMAX) mobile broadband wireless access system, the pilot mode of PUSC permutation for a different number of transmit antennas cannot be well designed due to the following points.

An existing design of pilot patterns for WiMAX PUSC permutations for 1, 2, and 4 transmit antenna numbers is shown in Figures 1 (a) - (c), respectively.

As shown in FIG. 1, in a certain sense, the pilot patterns in one cluster for a single transmit antenna are irregular, such that adjacent pilot intervals of even-numbered OFDMA symbols are 4 subcarriers, and The adjacent pilot spacing of the odd-coded OFDMA symbols is 12 subcarriers. The irregularity of the pilot subcarriers will somewhat deteriorate the performance of the channel estimation. The same problem exists for the pilot patterns of 2 and 4 transmit antennas.

For the pilot pattern of the four transmit antennas, the pilot subcarrier overhead is doubled, so for some useful data symbols, it must be punctured for conventional coding or truncated for the traditional turbo code (CTC). The simulation results show that the perforation or truncation operation will cause severe performance degradation. Summary of the invention

In view of the above, the present invention has been implemented. It is an object of the present invention to provide a method and system for mapping pilots that are capable of improving data mapping performance and signal estimation performance.

In an aspect of the invention, a method for mapping pilots in a base station is provided, the method comprising the steps of: generating at least one pilot sequence; and mapping the at least one pilot sequence to time and frequency resources, The adjacent pilot spacing of the symbols is made regular.

In another aspect of the present invention, an apparatus for mapping pilots in a base station is provided, the apparatus comprising: pilot sequence generating means for generating at least one pilot sequence; and pilot mapping means for Mapping the at least one pilot sequence onto time and frequency resources such that adjacent pilot spacing of symbols is a rule of.

With the system and method of the present invention, since the pilot pattern is regular, the performance of data mapping operations and channel estimation is improved. DRAWINGS

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings

Figure 1 shows a block diagram of a base station in accordance with an embodiment of the present invention;

2 shows a block diagram of a mobile station in accordance with an embodiment of the present invention;

Figure 3 illustrates a new pilot pattern for a single transmit antenna in accordance with an embodiment of the present invention; Figure 4 illustrates a new pilot pattern for two transmit antennas in accordance with an embodiment of the present invention; Figure 5 (a) A new pilot pattern for one of the four transmit antennas (transmit antennas 0 and 1) is shown;

Figure 5 (b) shows a new pilot pattern for the other of the four transmit antennas (transmit antennas 2 and 3);

Figure 6 shows another new pilot pattern for 4 transmit antennas;

Figure 7 still shows another new pilot pattern for the four transmit antennas;

Figures 8(a), 8(b) and 8(c) show existing pilot patterns for a single transmit antenna, 2 transmit antennas, and 4 transmit antennas, respectively. detailed description

In the following, specific embodiments of the invention will be described in detail with reference to the drawings. Figure 1 shows a block diagram of a base station in accordance with an embodiment of the present invention.

As shown in FIG. 1, a base station according to an embodiment of the present invention includes: first to Nth pilot sequence generating units 10-1 to 10-N, first to Nth pilot mapping units 11-1 to 11 -N, first to Nth OFDM modulation units 12-1 to 12-N, channel coding unit 13, modulation unit 14, MIMO space-time coding unit 15, and first to N-th data mapping units 16-1 to 16-N, where N=l, 2 or 4.

Each of the first to Nth pilot sequence generating units 10-1 to 10-N generates a pilot sequence. The generated pilot sequences are input to the first to Nth pilot mapping units 11-1 to 11-N, respectively.

In the case of N=l, the first pilot mapping unit 11-1 maps the pilot sequence onto the time-frequency resource according to the pilot pattern shown in FIG. As shown in Figure 3, we can observe that the right half of the symbol has been adjusted. The location makes the new pilot pattern more regular, which will benefit data mapping operations and channel estimation. For example, the adjacent pilot spacing of the even-numbered OFDM symbols is 8 subcarriers, and the adjacent pilot spacing of the odd-numbered 'OFDM symbols is 8 subcarriers.

In the case of N=2, each of the first to Nth pilot mapping units 11-1 to 11-N is outputted from the first to the Nth guide according to the pilot pattern as shown in FIG. The pilot sequences of the frequency sequence generating units 10-1 to 10-N are mapped onto time-frequency resources. As shown in Figure 4, adjusting the position of the right half of the symbol makes the new pilot pattern more regular, which will benefit data mapping operations and channel estimation. Pilot spacing between pilot subcarriers for one transmit antenna and pilot subcarriers for another transmit antenna for symbols numbered 4k, symbol numbered 4k+1, symbol numbered 4k+2, number The sign for 4k+3 remains unchanged, where k is an integer.

In the case of N=4, each of the first to Nth pilot mapping units 11-1 to 11-N is outputted from the first to the Nth guide according to the pilot pattern as shown in FIG. The pilot sequences of the frequency sequence generating units 10-1 to 10-N are mapped onto time-frequency resources. As shown in Figure 5, the position of the right half of the symbol is adjusted to make the new pilot pattern more regular, which will benefit data mapping operations and channel estimation.

Furthermore, as shown in Fig. 5, we can see that the second transmit antenna pair (antennas 2 and 3) and the first transmit antenna pair (antennas 0 and 1) are multiplexed into the code domain. At the receiver, appropriate operations such as code demultiplexing can be performed to separate the first and second transmit antenna pairs.

As shown in FIG. 5, the pilot multiplexing pattern between the first transmit antenna pair (ie, antennas 0 and 1) and the second transmit antenna pair (antennas 2 and 3) is changed from frequency multiplexing to code multiplexing. In other words, the pilot symbols of the four transmit antennas are multiplexed in the time domain and the code domain. By using this pilot symbol multiplexing mode, the pilot subcarrier overhead can be halved, thereby avoiding puncturing or truncation operations.

As described above, in each of the first to Nth pilot mapping units 11-1 to 11-N, the pilot symbol positions are adjusted such that the pilot pattern for one number of transmitting antennas is more regular. The regular pilot pattern is advantageous not only for data symbol to subcarrier mapping operations, but also for channel estimation optimization and enhancement.

On the other hand, the information to be transmitted is input to the channel coding unit 13, and the information bits are channel-encoded in the channel coding unit 13. Then, the modulating unit 14 performs constellations such as QPSK:, 16QAM with respect to the coded bits to generate modulation symbols.

Next, the MIMO space-time encoding unit 15 performs MIMO encoding on modulation symbols to generate MIMO encoded symbols corresponding to a plurality of transmitting antennas. Then, the first to Nth data mapping units 16-1 The MIMO encoded symbols are mapped onto the time-frequency resources according to the allocated resources to 16-N to generate time and frequency symbols having data mapped onto the allocated resources. Time and frequency symbols having pilot and data are input to the first through Nth OFDM modulation units 12-1 through 12-N, respectively.

Then, each of the first to Nth OFDM modulation units 12-1 to 12-N is OFDM-modulated by IFFT to generate a time domain OFDM signal to be transmitted through the respective transmit antennas.

Alternatively, the pilot pattern for the four transmit antennas may be the pilot pattern as shown in Figures 6 and 7. For the example in Figure 6, it should be noted that the pilot mode period is changed in time from 4 OFDM symbols to 8 OFDMA symbols. The pilot symbols corresponding to the first transmit antenna pair (transmit antennas 0 and 1) are located at the first 4 OFDMA symbols, and the pilot symbols corresponding to the second transmit antenna pair (transmit antennas 2 and 3) are located at the rear 4 At the OFDMA symbol.

As shown in FIG. 6, the pilot multiplexing pattern between the first transmit antenna pair (ie, antennas 0 and 1) and the second transmit antenna pair (antennas 2 and 3) is changed from frequency multiplexing to code multiplexing.

In this case, the pilot multiplexing mode between the first transmit antenna pair and the second antenna pair may also be time-multiplexed, and resource allocation should be performed in units of 8 OFDM symbols in the time domain, and The pilot overhead is halved.

For the case in Fig. 7, in order to halve the pilot subcarrier overhead, the half pilot symbols shown in Fig. 8(b) are changed from the corresponding transmitting antennas 0 and 1 to the transmitting antennas 2 and 3.

In other words, the pilot multiplexing mode between the first transmit antenna pair (i.e., antennas 0 and 1) and the second transmit antenna pair (antennas 2 and 3) is frequency multiplexed, but the pilot shackle is halved.

It should be noted that halving the pilot symbols within the cluster structure will cause some channel estimation performance loss. However, this loss can be largely compensated by increasing the transmission power of the pilot subcarriers. The halving of the pilot symbols within the cluster structure makes it possible to avoid puncturing or truncation operations and thereby greatly improve the performance of demodulation and decoding.

2 shows a block diagram of a mobile station in accordance with an embodiment of the present invention. As shown in FIG. 2, a mobile station according to an embodiment of the present invention includes: first to Mth OFDM demodulation units 21-1 to 21-M, pilot extraction unit 23, channel estimation unit 24, MIMO space-time decoding Unit 22, demodulation unit 25, and channel decoding unit 26. It is to be noted here that some modules not related to the present invention, such as time and frequency synchronization modules, are not shown.

The reception signals from the M reception antennas are input to each of the first to Mth OFDM demodulation units 21-1 to 21-M, where M represents the number of reception antennas at the MS. Then, each of the first to Mth OFDM demodulation units 21-1 to 21-M performs OFDM demodulation by FFT to generate a frequency signal.

Next, the pilot extracting unit 23 extracts the received pilot symbols from the received frequency domain signals to obtain received pilot symbols. At the same time, channel estimation unit 24 performs channel estimation on the received pilot signal for the MIMO signal to produce an estimated channel coefficient. As described above, the pilot symbols are placed such that the new pilot pattern is more regular, which would be beneficial for channel estimation. For example, the adjacent pilot spacing of the even-numbered OFDM symbols is 8 subcarriers, and the adjacent pilot spacing of the odd-numbered OFDM symbols is also 8 subcarriers.

Based on the received signal on the frequency and the estimated channel coefficient, the MIMO space-time decoding unit 22 performs MIMO by using an algorithm such as ZF (Zero Forcing), MMSE (Minimum Mean Square Error), ML (Maximum Likelihood) Detected to generate a detection symbol.

Then, the demodulation unit 25 performs soft constellation demodulation on the MIMO detection output to obtain decoded soft information. Further, channel decoding unit 26 generates channel decoding bits based on the decoded soft information.

The new pilot pattern suggested in the present disclosure has the following benefits compared to existing pilot patterns. For pilot patterns of single and two transmit antennas, the proposed new pilot pattern has a more regular pilot symbol arrangement that can be beneficial for data mapping operations and channel estimation performance.

For the pilot pattern of the four transmit antennas, the proposed new pilot pattern halve the pilot subcarrier overhead by changing the multiplexing method between the first transmit antenna pair and the second transmit antenna pair. Therefore, the puncturing and truncation operations are avoided, and the performance of demodulation and decoding is greatly improved.

While the invention has been particularly shown and described with respect to the exemplary embodiments of the present invention, the invention is not limited to the embodiments, and those skilled in the art will understand without departing from the spirit and scope of the invention as defined by the appended claims. Under the premise, various changes can be made in form and detail.

Claims

Rights request

A method for mapping pilots in a base station, comprising the steps of:

Generating at least one pilot sequence; and mapping the at least one pilot sequence onto time and frequency resources such that adjacent pilot intervals of the symbols are regular.

2. The method of claim 1 further comprising the step of: generating a modulation symbol based on the bits to be transmitted;

The modulation symbols are mapped onto time and frequency resources.

The method according to claim 1, wherein the base station has a single transmit antenna, and adjacent pilot intervals of even-numbered symbols are the same as adjacent pilot intervals of odd-numbered symbols.

4. The method according to claim 1, the base station has 2 transmit antennas, and a pilot interval between a pilot subcarrier for one transmit antenna and a pilot subcarrier for another transmit antenna is numbered The 4k symbol, the symbol numbered 4k+1, the symbol numbered 4k+2, and the symbol numbered 4k+3 remain unchanged, where k is an integer.

The method according to claim 1, wherein the base station has four transmit antennas, and a pilot multiplexing mode between the first transmit antenna pair and the second transmit antenna pair is code multiplexing. And halve the pilot overhead.

The method according to claim 5, wherein the base station has four transmit antennas, and the pilot multiplexing mode between the first transmit antenna pair and the second antenna pair is time-multiplexed. The pilot period is 8 symbols in time and halve the pilot overhead.

The method according to claim 5, wherein the base station has four transmit antennas, and a pilot multiplexing mode between the first transmit antenna pair and the second antenna pair is frequency reuse, and The pilot overhead is halved.

8. A device for mapping pilots in a base station, comprising:

a pilot sequence generating device for generating at least one pilot sequence;

The pilot mapping apparatus is configured to map the at least one pilot sequence to the time and frequency resources such that the adjacent pilot intervals of the symbols are regular.

9. The apparatus of claim 8 further comprising: a modulating means for generating a modulation symbol based on bits to be transmitted; and data mapping means for mapping the modulation symbols onto time and frequency resources.

The apparatus according to claim 8, wherein the base station has a single transmit antenna, and adjacent pilot intervals of even-numbered symbols are the same as adjacent pilot intervals of odd-numbered symbols.

The apparatus according to claim 8, wherein the base station has 2 transmit antennas, and a pilot interval between a pilot subcarrier for one transmit antenna and a pilot subcarrier for another transmit antenna is The symbols numbered 4k, the symbols numbered 4k+l, the symbols numbered 4k+2, and the symbols numbered 4k+3 remain unchanged, where k is an integer.

The device according to claim 8, wherein the base station has four transmit antennas, and a pilot multiplexing mode between the first transmit antenna pair and the second transmit antenna pair is code multiplexing. And halve the pilot overhead.

The device according to claim 12, wherein the base station has four transmit antennas, and the pilot multiplexing mode between the first transmit antenna pair and the second antenna pair is time-multiplexed. The pilot period is 8 symbols in time and halve the pilot overhead.

The device according to claim 12, wherein the base station has four transmit antennas, and the pilot multiplexing mode between the first transmit antenna pair and the second transmit antenna pair is frequency reuse. And halve the pilot overhead.