CN100471094C  OFDM time and frequency synchronizing method capable of correcting longrange frequency deviation  Google Patents
OFDM time and frequency synchronizing method capable of correcting longrange frequency deviation Download PDFInfo
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 CN100471094C CN100471094C CN 02134107 CN02134107A CN100471094C CN 100471094 C CN100471094 C CN 100471094C CN 02134107 CN02134107 CN 02134107 CN 02134107 A CN02134107 A CN 02134107A CN 100471094 C CN100471094 C CN 100471094C
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技术领域 FIELD
本发明厲于无线通信或有线通信领域， Li the present invention is a wireless communications or wired communications,
背最技术 Most technology back
OFDM由于具有数据传输速率高，抗多径干扰_力强，频谱效率商等优点，越来越受到重视。 Because OFDM has a high data transfer rate, and strong multipath immunity _ spectrum efficiency providers, etc., more and more attention. 它已成功用于有线、无线通信。 It has been successfully used in wired and wireless communications. 如：ADSL(Asyimnctrk Distal Subscriber Line),Wireless LAN, DAB(Digital Audio Broadcasting)、DVB、EEE802.11a 及HyperLAN/2 中。 Such as: ADSL (Asyimnctrk Distal Subscriber Line), Wireless LAN, DAB (Digital Audio Broadcasting), DVB, EEE802.11a and HyperLAN / 2. 在目前正在制定的IEEE802.16中，也大量涉及了OFDM技术• OFDM这种新的调制技术也可用于新一代的移动通信系统中。 In IEEE802.16 currently being developed, but also heavily involved in the OFDM technology • OFDM modulation of this new technology can also be used for the next generation of mobile communications systems. 使用OFDM技术将大大提商新一代移动通信系统的传输数据率和頻谱效率，且具有很好的抗多径、同信道干扰和冲击嗓音能力，见文献： Bingham1J.AC, MMuttidurri^ modulation for data transmission: an idea whose time has come，” IGEE Communications Using OFDM techniques to greatly enhance the transmission data rate and spectral efficiency of new generation mobile communication system, and has good resistance to multipath, cochannel interference and impact voice capabilities, see literature: Bingham1J.AC, MMuttidurri ^ modulation for data transmission: an idea whose time has come, "IGEE Communications
M^azine, Volume: 28 Issue: 5 , May 1990, P^e(s): 5 14:和文献：Yun Hee Kim; Iickho Song; Hong Gil Kim;Taejoo Chang; Hyung Myung Kim, “Perfmmance analysis of a coded OFDM sy^em in timevarying multipathRayleigh Ming channels, ” Vehicular Technology, IEEE Transactions on，Volume: 48 Issue: 5，Sept. 1999，Pt%e(s):16101615 所述. M ^ azine, Volume: 28 Issue: 5, May 1990, P ^ e (s): 5 14: and literature: Yun Hee Kim; Iickho Song; Hong Gil Kim; Taejoo Chang; Hyung Myung Kim, "Perfmmance analysis of a coded OFDM sy ^ em in timevarying multipathRayleigh Ming channels, "Vehicular Technology, IEEE Transactions on, Volume: 48 Issue: 5, Sept 1999, Pt% e (s):. the 16101615.
OFDM技术的弱点之一是对时间和頻率同步的要求特别是頻率同步要求比单载波系统要离得多* 一般要求采用OFDM技术的系统在接收靖頻率供移不超过其子载波间隔的2%,见文献van de Beek, JJ; Sandelll M.; Borjesson, PO, “ML estinwlimi of tone 的d firequency offset in OFDMsystems,” Signal Processing, IEEE Transactions on, Volume: 45 issue: 7, July 1997, Page(s): 1800 1805 所述•OFDM同步分为时间同步和频率同步.同步模块的位置见图I中的棋块11。 OFDM technology is one of the weaknesses of frequency and time synchronization requirements in particular frequency synchronization required than a single carrier system to leave much * ships requires a system with OFDM technology for frequency shift in the received Jing does not exceed 2% of the subcarrier spacing see Document van de Beek, JJ; Sandelll M .; Borjesson, PO, "ML estinwlimi of d firequency tone is offset in OFDMsystems," Signal Processing, IEEE Transactions on, Volume: 45 issue: 7, July 1997, Page (s ): 1800 1805 • OFDM synchronization is divided into the time synchronization and frequency synchronization position synchronization module is shown in Figure 11 I of the dragon. 时间同步的目的是在收到的串行数据流中找出各个OFDM符号的边界：而频率同步的目的是求出并纠正收靖相对发端的頻率偏移。 Time synchronization is to identify the purpose of the boundary of each OFDM symbol in the serial data stream received: the frequency synchronization purposes is to find and correct a frequency offset originating relatively close Yasushi.
在使用OFDM技术的系统中，取得时间同步之后，可采用计算差分相关的方法来计算频率偏移信息,参见文献Moose, PH, “A technique for orthogonal fim^iency division multiplexing frequencyofl&et CtMTCCtionl ” Conununic^kms, IEEE Transa^km on，Vohime: 42 Issue: 10, Oa 1994, Page(s): 2908 2914所述。 After the system using OFDM technology, to obtain time synchronization, can be calculated differential correlation method for calculating the frequency offset information, see Document Moose, PH, "A technique for orthogonal fim ^ iency division multiplexing frequencyofl & et CtMTCCtionl" Conununic ^ kms, IEEE Transa ^ km on, Vohime: 42 Issue: 10, Oa 1994, Page (s): said 29082914. 差分相关的基本原理如下(如圈2所示> 首先发靖在数据中放入两塯相鬨的训练序列，相同数据之间的距离为么然后收端_如下计算公式用差分相关值估计频偏： The basic principle of the differential correlation as follows (as shown in circle 2> is first made into two Liu Jing coax training sequence in the data phase, the distance between it and the same data as the terminating _ differential correlation value calculated by the estimated frequency partial:
其中，表示已估计的时间_步点，6表示估计的频率偏移值，r【ik]为接收信号，m代表训练序列的长度，4代表差分距离。 Wherein _ indicates the estimated time step point, 6 denotes the estimated frequency offset value, r is [IK] as a received signal, m represents the length of the training sequence, 4 represents a difference distance.
差分相关距离d的选择对頻率儂移的估计性能有根大彩确•差分距离选择得越小，则频率偏差估计的范围就越大，参见文献Marti i Puigv P,; Alvarez, JS” 44Coarsc frequency estimation inOFDM padcet oriented systems,” Acoustics, Speech, and Signal Processing, 2001. Proceedings. 2 001 IEEEInternational Conference on，2001, Page($): 2337 2340 vo丨,4 所述• Differential selection of the relevant distance d Lennon frequency shift estimation performance rooted large color difference determined • select smaller the distance, the frequency offset estimation range greater, see reference Marti i Puigv P ,; Alvarez, JS "44Coarsc frequency estimation inOFDM padcet oriented systems, "Acoustics, Speech, and Signal Processing, 2001. Proceedings 2 001 IEEEInternational Conference on, 2001, Page ($):. 2337 2340 vo Shu, 4 •
实际中，常常驀求能够对尽可能大范围内的頻偏进行估计并纠正，因此根据上述原理，需要尽可能地缩小差分距离。 In practice, often suddenly find an estimate of the frequency offset can be as large as possible within the range of correction and, therefore according to the above principle, the difference distance is necessary to reduce as much as possible. 常规的解决办法是发嶋连续地放置PN序列(pseudonoisesequences,伪随机序列)(如图3所示)，通过选择尽可能小的PN序列周期来缩小差分距离d.由于PN序列需要提供一定的扩頻增益来实现抗干扰能力，否则会严重影病频率同步的性能，因此需要PN序列的周期不能选择得很小，相应的差分距离也不能很小，这就覼制了常规方法所能进行頻偏估计的范围。 The conventional solution is continuously sent Kojima placed PN sequence (pseudonoisesequences, pseudorandom sequence) (Figure 3) to reduce the difference distance d as small as possible by selecting a PN sequence period. Due to the need to provide a certain PN sequence the spreading gain achieved antijamming capability, otherwise it will seriously affect the performance of the synchronous frequency of the disease, it is necessary to select the PN sequence period is not very small, the corresponding distance is not very small difference, which is manufactured by conventional methods can Luo carried out a range of frequency offset estimation.
发爾内容 Fat content Seoul
本发明的目的在于提供一种可以纠正大范围频Il的OFDM时间、頻率同步的方法，它包括发纗的训练序列设置和收靖的相应处理。 Object of the present invention is to provide a wide range of frequency to correct the OFDM time Il, frequency synchronization method, comprising respective processing Zui hair and received training sequence is provided Jing.
本发明任务的实现是通过发纗先将PN序列按碍片重寞放置，然后将得到的序列再进行整体重复，构成训练序列，最后将此训练序列与OFDM原始歙据点对点带权叠加后发射出去；收端首先取得时间同步，然后对接收数据进行差分距离为I的差分相关运算，最后在1/2个OFDM系统带宽的范围内对頻偏进行估计和补偿• The task of the present invention is achieved by sending Zui first PN sequence by placing lonely hinder tablet weight, and then the resulting sequence then repeats the whole, constitute a training sequence, the training sequence with this final original OFDM data after the point Xi weighted superimposing transmission out; terminating first acquires time synchronization, and data received from the differential operation of the differential correlation of I, and the final estimate of the frequency offset compensation in the range of 1/2 • OFDM system bandwidth
本发明的创新之处在于在发端在第一次重复时，将PN序列按码片，而不是PN序列的周期进行重复放置，然后在收端利用相应的差分相关方法对接收数据进行频率偏移估计和补偿，从而取得OFDM系统的频率同步。 The innovation of the present invention is that when the originating first iteration, the PN sequence by chips, instead of repeating a cycle of the PN sequence is placed, then the receiving end the received data frequency offset associated with the corresponding difference method estimation and compensation to achieve frequency synchronization of OFDM systems. 这里，码片的含义是一个数据位，例如，OFDM系统的FFT点数躭是其原始数据的码片数^显然，这种方法了克服常规方法频率鴒移离阶范圃受到PN序列周期的隈制，它的頻偏估计范围与PN序列爾期无关，因此差分距离d可缩小至理论最小值I,相应的頻儋估计范櫊为Oimi系统带宽的1/2。 Here, the meaning of the chip is a data bit, for example, an FFT points Dan OFDM system is the number of chips which raw data ^ Obviously, this method is a conventional method to overcome frequency shift from the lingnorm PN sequence period Po by Okuma system, its range of frequency offset estimation independent PN sequence of Seoul, so the difference distance d may be reduced to the theoretical minimum I, Dan corresponding frequency bandwidth as the estimated range Ge 1/2 Oimi system. 按照本发明的一种可以纠正大范围麵偏的OFDM时间、頻率同步的方法，其特征在于它包含下列步骤： According to a the present invention can correct a large range of partial surface OFDM time, frequency synchronization method, characterized in that it comprises the following steps:
—、发端  originator
发端对接收信号处理的步驟如下(如圈4所示)： Originating the received signal processing step are as follows (as shown in circle 4):
1)选择一段周期为义的m序列w[Jk]，*6[0,^.1],此时m[幻可取值为复 1) Select a period defined as the msequence period w [Jk], * 6 [0, ^ . 1], m at this time [phantom possible values complex
数形式，BPm[*]6{l + y,ly},也可为实数形式，即w⑷e {1,1}; Forms, BPm [*] 6 {l + y, ly}, may also be a real number, i.e. w⑷e {1, 1};
2)第一次重复(如图5所示)：将《[幻按码片重复，每个码片重复JV,,次，生成 2) the first iteration (Figure 5): A "[Magic repeated by chip, each chip is repeated JV ,, Ci, generate
一个长度为序列/«狀],ke[0,NmNHl]t其数学表达式如下： m^nik/NJ kemmN„\] (2) A sequence of length / «like], ke [0, NmNHl] t following mathematical expression: m ^ nik / NJ kemmN"  \] (2)
其中，/表示整除运算。 Where / represents integer division.
3)第二次重复(如图6所示>:上述序列W【幻在训练序列中的完整重复次数 3) repeated a second time (Figure 6>: complete the above sequence of repetitions W [in the training sequence of magic
〜是"/(纥\)的整数部分，W为OFDM系统的FFT点数；将上述PN ~ Is "(knot \) is the integer part of /, W is the number of FFT points in OFDM system; the above PN
序列wlP]连续整体重复放置，使总的点数为M得到训练序列，其数 Sequence WLP] repeated continuously integrally disposed, so that the total number of points obtained training sequence is M, the number
学表达式如下： Learn expressions are as follows:
其中，mod表示取模运算。 Wherein, mod represents modulo operation.
4)将训练序列Ua]与OFDM原始数据(不包含循环前缀部分)按下式进行点对 4) Ua training sequence] and the original OFDM data (excluding a cyclic prefix portion) of the following formula in point
点带权叠加后(如图7所示)，得到最终的发射載据发射出去： After the weighted superposition point (7), to give the final emission emitted data carrier:
5[k} = yl^d[k]+4pt[k] ke[0,Nl] (4) 5 [k} = yl ^ d [k] + 4pt [k] ke [0, Nl] (4)
其中，为加权值，其物理意义是训练序列的能置相对于发射数据总 Wherein a weighting value, which is the physical meaning of the training sequence can be set relative to the total transmitted data
能I：的归一化值。 Can I: normalized value.
二、收端 Two, terminating
收纗对接收信.处理的步11如下(如圈S所示)： The yield of Zui received signal processing step 11 follows (shown as circles S):
I)按照下式计算目标函数，以取得时间同步： I) the objective function is calculated according to the following formula to obtain time synchronization:
时间同步点为使取值最大的的值，a为接收序列中放置的PN序列相对本地PN序列滑动的点数。 Time synchronization point to make the value of the maximum value, a is the received sequence is placed in a local PN sequence PN sequence relative sliding points.
2)从训练序列起始点开始将个点的接收序列分为段，记为： 2) the training sequence from the start point of the received sequence of points is divided into sections, referred to as:
3)对每个与本地m序列按照下式求相关，得到&个相关值 3) each associated with the local sequence according to the following equation m, & correlation values obtained
对每组相关值将相邻的两个相关值^"^、^共扼相乘，累加， 得到各组共扼相关值c7w^: Correlation values associated with each group of two adjacent values ^ "^, ^ conjugate multiplying the accumulated, to obtain a correlation value of each group conjugate c7w ^:
把上述^个组共扼相关值进行累加，求幅角，调養系数，得到最终的频偏估计值为： ^ The above groups were briefly accumulating correlation values, seeking argument, tone coefficients, the final frequency offset estimate is obtained:
总的计算公式为： The total is calculated as follows:
其中，左表示估计的頻率鮮值，r[ltj为接收信号，汉为FFT长度，&为PN序列wW长度，义为PN序列mW按_片重复_次数，〜为序列W⑷的整体重*次数。 Wherein the left represents the estimated frequency fresh value, r [ltj to receive signals, the Han FFT length, & a PN sequence wW length, Yi repetition _ frequency and the PN sequence mW by _ sheet, ~ sequence W⑷ overall weight * number .
4)进行相应的麯偏补偿。 4) corresponding bias compensation curve.
这种设计方法的依据是： This design approach is based on:
1)由于各个PN序列相同，因此它们之间的相关性可以体现頻率偏移； 1) Since identical respective PN sequences, so the correlation between them may be embodied in a frequency offset;
2)由于发鳩对PN序列第一次重复时为按码片重复，调练序列中相興数据之间的最小间隔为I,因此在理论上达到了最小差分炬离的要求，收端按照此差分距离来处理数据可以估计最大范围的频偏； 2) Since the PN sequence dove hair when repeatedly pressing the first chip, a training tone is repeated minimum interval between data sequences Xing phase I, so in theory the minimum differential torch reached from the requirement, according to the receiving end this difference data may be processed from the maximum estimated frequency offset range;
3)由于发纗第一次重复时，PN序列不是按照整个长度来重复放置的，因此差分距离与PN序列的长度无关，因此PN序列周期的选择可以更灵活，若选择周期较长的PN序列，可以提高抗干扰能力； 3) due to hair Zui first repetition, not according to the entire length of the PN sequence is repeated is placed, and therefore independent of the PN sequence length distance difference, so selecting the PN sequence period can be more flexible, if a longer period of the PN sequence selection can improve antijamming capability;
4)将按码片重复后得到的PN序列再重ft放置〜次的目的是累加能量,提高性能； 4) PN sequence chip repetition obtained will then replaced object ~ ft times is cumulative energy, to improve performance;
5)为保证准_实现同步，可以在捕获阶段通过提高p值来掲高发射截据中训练序列成分的信号功率，而在蹋踪阶段降低p值。 5) In order to ensure a quasi _ synchronized, can be kei by increasing pvalue cutoff highpower transmission signal according to the training sequence component in the acquisition phase, the pvalue is reduced tread tracking phase. 调节p可以实现最佳时间和频率同步。 P can be adjusted to achieve the optimum time and frequency synchronization. 当PI时，发射数据完全为训练序列信号；当/7=0时，发射数据完全为OFDM原 When the PI, the transmission data is completely training sequence; if / 7 = 0, the transmission data is completely original OFDM
始数据。 The beginning of the data. p值的选择也是本专利的技术之一。 Selecting the value of p is one of the techniques of this patent.
理论分析证明，采用本专利所述的方法可以将OFDM系统的頻率偏移估计范围达到最大，即1/2个OFDM带宽，具有很强的实用价值. Theoretical analysis shows that, using the method described in this patent may be frequency offset estimation for OFDM systems the maximum range, i.e. 1/2 OFDM bandwidth has great practical value.
附_说期 Attached _ said period
图I为一般的OFDM系统框图图中，11为同步模块； FIG. I is a general block diagram of an OFDM system, the synchronization module 11;
图2为差分相关的基本原理图 Figure 2 is a schematic diagram of the differential related to basic
图2中的训练数据构成的17和18完全相网，就是画3中的任意一个己知序列，由于只有对应数据间才具有相关性，因而差分距离只齙选择为对应数据位之间的距离，注意圈2中的差分距离并不一定为调练截镅的个数m,它还取决于两个训练序列之间相隔的数据点数；囿3为常规的OFDM符号中训练序列的结构 17 and 18 exactly in the training data network configuration of FIG. 2 is a drawing of any known sequence 3, since it has only the correlation between the corresponding data, and therefore only the difference distance is the distance between the benches select corresponding data bits , Note that the number m of difference distance ring 2 is not necessarily in practice a truncated modulation americium, it depends on the data between two points separated by a training sequence; caught 3 is a conventional OFDM symbols of the training sequence structure
图中训练序列由多个相同的PN序列构成，n个PN序列19、20、21、22完全相同，而且它们是连续放置的，即相邻的两个PN序列之间无间隔，因此，相同数据之间的最小距离即最小差分拒离为PN序列的周期，这表明差分距离受到PN序列的周期的限制； FIG training sequence composed of a plurality of identical PN sequences, PN sequences 19, 20 nidentical, and they are placed contiguously, without i.e. the spacing between two adjacent PN sequences, and therefore, the same i.e., the minimum distance between the data from the minimum differential repellent cycle of the PN sequence, which indicates a difference from the restricted period of the PN sequence;
图4为本专利说明的发端OFDM符号中训练序列的产生步骤图中，可看出发端处理步骤中含有两次重复过程，第一次为按码片重复，第二次为整体重复； The step of generating an originating OFDM symbols FIG 4 is illustrated in Figure Patent training sequence, can be seen originating process steps comprising process is repeated twice, by repeating the first chip, the second overall repeat;
图5为本专利说明的发靖第一次重复后得到的PN序列的结构示意图图中，PN序列周期为PN序列按码片重复了'次； PN sequence is a schematic structural diagram of the present patent described in FIG. 5 Yasushi hair obtained after the first iteration, the PN sequence by PN sequence period is repeated chip 'times;
图6为本专利说明的发靖第二次重复后得到的调炼序列攻句的结构示意图图中,训练序列/[幻的长度为OFDM系统的FFT点数JV ,PN序列W1 [幻在训练序列中完《重复了次； FIG 6 is a schematic structural diagram of a sequence of attack adjustment period after refining patent specification Yasushi hair obtained in the second iteration, the training sequence / [length of FFT points phantom OFDM system JV, PN sequence W1 of [magic training sequence finished in "repeated times;
图7为本专利说明的训练序列在OFDM发符号中的位童示意围图中，训练序列与OFDM原始数据进行点对点帚权叠加； Figure 7 is a training sequence of bits Tong patent specifications issued in the OFDM symbol surrounded by a schematic drawing, OFDM training sequence with the original data point broom right superimposed;
图8为本专利说明的收纗数据处理步_的实施裾图異雔瘺_方式 Figure 8 is a data processing step received Zui _ garment embodiment illustrated in FIG Patent heterologous Chou embodiment fistula _
下面以给出一个具体的OFDM配置下，本专利的实现步驟《注：下例中的参数并不彩响本专利的一般性。 Below is given a specific configuration of the OFDM, this patent implementation steps "Note: Examples of parameters are not generally affect the color of this patent.
设OFDM有用符号长度为N»4096，PN序列选择周期为'„127的m序列，第一次重复次数\ = 2，则第二次重复次数〜=4096/(127*2) = 16。取p0.5,表示训练序列在发射数据中占一半的能量。 Useful OFDM symbol length is set to N »4096, PN sequence selection period '" m sequence is 127, the first repetition frequency and \ = 2, the second repetition ~ = 4096 / (127 * 2) = 16. take p0.5, half of the training sequence represents the energy in the transmission data.
发纗将m序列按码片重复2次，得到将体重复17次，截去尾部多余的数据，构成长度为40%的调练序列/[幻，按照公式5将训练序列找句与OFDM原始数据进行点对点带权曼麵构成OFfm发緻符号发射出去• Zui made by the repeated chip sequence m 2, was repeated 17 times to obtain the material, cut off the excess tail portion of data constituting 40% of the length of training sequence modulation / [phantom, in accordance with the formula to find the training sequence 5 and the original OFDM Man data point weighted symbol actuation surface configured OFfm hair emitted •
收緇首先按照公式5取得时间同步，也就是找到OFl^i符号的起点，OFDM有用数据记为40 »€[0,4095]；与此同时也找到了调练序殉的开始点。 First, according to Equation 5 Zi received synchronization function, i.e. to find the symbol starting OFl ^ i, referred to as the OFDM useful data 40 »€ [0,4095]; at the same time to find the starting point of the sympathetic tone training sequence. 下面开始估计频偏： Here began the estimated frequency offset:
⑴从训练序列起点开始，每127*2 = 254个数据分为一段，共〜=16段，记为 先e[0,253]; ⑴ starting from the starting point of the training sequence, each of 127 * 2 = 254 data is divided into a period, a total of 16 = ~ section, referred to as the first e [0,253];
(2)按照公式7与本地m序列作相关，得到32个相关值，记为Cor: (2) according to Equation 7 for the correlation with the local sequence m, to obtain 32 correlation values, referred to as Cor:
和Cor10  Cor,15，即： And Cor10  Cor, 15, namely:
(3)按照公式8得到各组共扼相关值Cor^,即： (3) obtained according to equation 8 conjugate groups correlation value Cor ^, namely:
(4)按照公式9进行频偏估计： (4) frequency offset estimate according to equation 9:
(5)®照下式对数据进行頻率补偿： (5) ® according to the formula frequency compensation data:
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US7551696B2 (en)  20040720  20090623  Realtek Semiconductor Corp.  Method and apparatus of detecting ISI/ICSI in an OFDM system 
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CN100502377C (en) *  20050107  20090617  北京邮电大学  Timed and largedeviation combined estimation method suitable to burst transmission system 
CN1870465B (en)  20050524  20110601  都科摩（北京）通信技术研究中心有限公司  Generating method, communication system and communication method of circulation training sequence 
CN101222306B (en)  20070108  20120201  上海无线通信研究中心  Combined with the frequency domain and hybrid automatic repeat retransmission in a communication system and communication method 
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CN1258143A (en) *  19981106  20000628  松下电器产业株式会社  Orthogonal frequencydivision multiplex communication apparatus and method 
CN1359570A (en) *  19990705  20020717  三星电子株式会社  Apparatus of compensating for frequency offset using pilot symbol in an orthogonal frequency division multiplexing system 

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CN1258143A (en) *  19981106  20000628  松下电器产业株式会社  Orthogonal frequencydivision multiplex communication apparatus and method 
CN1359570A (en) *  19990705  20020717  三星电子株式会社  Apparatus of compensating for frequency offset using pilot symbol in an orthogonal frequency division multiplexing system 
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