DVB-T2系统中的信道估计与符号边界检测

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"这篇文档是关于在DVB-T2（Digital Video Broadcasting - Terrestrial 2）系统中的信道估计和符号边界检测算法的研究。作者Ching-Sheng Ni, Pei-Jun Shih, 和 Shin-Shiuan Cheng来自Himax Media Solutions Inc.，他们提出了一种新颖的算法，该算法利用P1符号的部分内容设计了关联模式，并通过后续的逐次消除来处理关联过程中产生的失真。通过获取信道信息，可以估计出符号间的干扰并优化符号边界位置，以最小化ISI（Inter-Symbol Interference）。 I. 引言 DVB-T2信号由超级帧组成，每个超级帧包含多个T2帧，每个帧由OFDM（Orthogonal Frequency Division Multiplexing）符号构成，包括一个P1 OFDM符号和多个P2及数据OFDM符号。P1符号负责传输传输类型和关键传输参数的信息，而P2符号则携带剩余参数，如保护间隔类型、编码率等，并且也承载一部分数据负载。 II. 信道估计方法提出的信道估计方法利用P1符号的部分内容设计了一种新的关联模式。这种方法的目标是准确估计信道状态信息，这对于数字电视广播系统至关重要，因为信道条件的变化会影响信号的质量和接收性能。通过这种方式，可以更有效地补偿由于多径传播和衰落导致的信道失真。 III. 符号边界检测在DVB-T2系统中，正确地检测符号边界对于解码过程至关重要。提出的成功消除技术有助于减少在关联过程中引入的噪声和失真，从而提高符号边界检测的准确性。通过这种优化，可以降低因符号间干扰(ISI)引起的错误检测概率。 IV. ISI最小化 ISI是OFDM系统中的主要问题，因为它可能导致符号误解。利用信道估计得到的信息，可以预测和校正由信道条件变化引起的ISI。通过对符号边界进行优化，可以最大限度地减少这种干扰，提高系统的整体性能和可靠性。 V. 总结该文提出的算法对DVB-T2系统的信道估计和符号边界检测进行了创新性改进，旨在提升接收端的解码质量和系统效率。通过有效地处理信道条件的变化和减少ISI，该方法有望提高DVB-T2系统的稳健性和服务质量，特别是在动态和复杂环境下的无线通信。关键词：信道估计，DVB-T2，ISI，符号边界检测，OFDM，多径传播"

Channel Estimation and Symbol Boundary Detection in DVB-T2 System

Ching-Sheng Ni, Pei-Jun Shih, Shin-Shiuan Cheng

Himax Media Solutions Inc., Taipei, Taiwan

Email: jennyshihpj@gmail.com, sean.cheng@stanfordalumni.org

ABSTRACT

A novel channel estimation and symbol boundary detection

algorithm is proposed herein for the DVB-T2 system. The proposed

channel estimation uses devised correlation patterns utilizing parts of

P1 symbol and is followed by proposed successive cancellation to

eliminate the artifacts generated during the correlation. With the

channel information, the inter-symbol interference is estimated and

symbol boundary position can be optimized according to the least ISI.

I. INTRODUCTION

A DVB-T2 signal is constructed by super frames, which consist

of several T2-frames, and each frame is composed of OFDM

symbols, including one P1 OFDM symbol and several P2 and data

OFDM symbols, as shown in Fig. 1. P1 symbol carries information

to indicate the transmission type and key transmission parameters. P2

symbols carry remaining parameters such as the guard interval type,

code rate, etc., and they also carry some data payload [1]. To receive

DVB-T2 signals, P1 symbol should first be detected and decoded for

key parameters. Once P1 symbol has been identified, the symbol

boundary detection could follow. Channel impulse response (CIR)

information can facilitate better symbol boundary detection, and

better CIR estimation can be achieved by taking advantage of P1

symbol. After the CIR is estimated, the symbol boundary can be

decided. The symbol boundary should be positioned so that the least-

possible inter-symbol interference (ISI) is incurred. The incurred ISI

can be estimated by the estimated CIR information. Finally, to avoid

the aliasing caused by frequency interpolation, a phase rotator is

employed and the rotation angle is computed after the proper symbol

boundary is decided.

II. CHANNEL ESTIMATION - CORRELATION

After the received P1 symbol is detected and decoded, P1 symbol

can be regenerated according to the decoded parameters. Parts of P1

symbol is utilized as the correlation pattern. Based on the structure of

P1 symbol, three different tailor-made patterns are devised to take

advantage of the special formatting of P1 symbol.

542

542 482 482

542

482

pattern 1

542

542 482

482

542

542 1024

0 482

542

0 60 542

P1 symbol

pattern 2

pattern 3

part 1 part 2 part 3 part 4

correlation result

c(n)

0 0

Figure 2. P1 symbol and correlation results of the devised patterns

As shown in Fig. 2, pattern 1 is constructed by the part2 and the

part3 of P1 symbol. Under perfect channel, the cross-correlation of

pattern 1 with the received signal yields the result shown next to

pattern 1 in Fig. 2. The cross-correlation result has three major pulses.

However, under perfect channel, there should only be one

propagation path, hence one pulse. Therefore, two extra undesired

pulses, due to the artifact of the cross-correlation, should be

eliminated for correct CIR estimation.

III. CHANNEL ESTIMATION – SUCCECIVE

CANCELLATION

Successive cancellation scheme can be employed here to help

eliminate the two undesired paths. In order to facilitate better

working of successive cancelation, two additional patterns - pattern 2

and 3 - for cross-correlation are proposed, as shown in Fig. 2. The

cross-correlation results of these two proposed patterns with the

received signal under perfect channel are also shown in Fig. 2, next

to the pattern respectively. When pattern 2 is employed for the cross-

correlation, the undesired two paths to eliminate are those to the right

of the maximum path, i.e. paths at 482 and 542 as shown in Fig. 2.

On the contrary, if pattern 3 is employed, the undesired two paths to

eliminate are those to the left of the maximum path, i.e. paths at 0

and 60.

Figure 1. DVB-T2 signal structure

The successive cancellation is implemented as follows. If pattern

2 is employed, the cross-correlation result is shown again in Fig. 3.

In this case, the main path at 0 and the Left-to-Right (LtoR)

cancellation are employed to eliminate the two undesired artifact

paths at 482 and 542, hence achieving correct CIR estimation. The

implementation is mathematically described in (1).

)()542()542(

)()482()482(

u 

tststs

(1)

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