THE AIM of second generation terrestrial digital video broadcasting

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1 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE Advanced Preamble Transmt Dversty of Polarzed DVB-T2 MSO System Usng Hybrd Dfferental Modulaton Zfeng Ku, Jae Shn Han, Jeong Mn Cho, Sungho Jeon, Member, EEE, Joosung Park, Member, EEE, Youngho Oh, and Jong Soo Seo, Fellow, EEE Abstract The dgtal vdeo broadcastng second generaton terrestral (DVB-T2) standard has adopted a preamble called P1 symbol to acheve the fast tme and frequency synchronzaton. The P1 symbol also carres basc transmsson parameters of DVB-T2 system, such as fast Fourer transform sze, guard nterval sze and transmsson type sngle nput sngle output or multple nput sngle output, etc. n ths paper, we propose an mproved preamble whch s modulated by a novel hybrd dfferental modulaton scheme that can provde transmt dversty gan to acheve the same performance of coherent transmsson. The proposed preamble has demonstrated a sgnfcantly mproved sgnalng error rate performance over varous channel condtons compared to the conventonal P1 symbol n DVB-T2. ndex Terms Dfferental modulaton, preamble, P1 symbol of DVB-T2, space tme block code, transmt dversty.. NTODUCTON THE AM of second generaton terrestral dgtal vdeo broadcastng (DVB-T2) system s to provde hgh defnton televson (HDTV) and hgh rate servces. The potental goal s acheved by adoptng new physcal layer features that ncrease the spectrum effcency, and t has been developed state-of-art technologes used as part of frst generaton system (DVB-T). DVB-T2 extends the avalable ranges of DVB-T and sgnfcantly reduces total overhead to buld a broadcastng system wth a throughput close to Shannon bounds, wth the best possble ruggedness of transmsson. The key motvaton behnd ths standard was the desre n order to offer HDTV servces as effcently and effectvely perspectves. However, broadcastng through the medum of ar requres the deployment of robust tmng synchronzaton and frequency offset compensaton due to the scattered mult-path fadng channel mparments. Thus, the appended non-coherent sgnalng of preamble (P1) before data feld enables recever to dentfy the encapsulated nformaton of super frames. Varous studes assocated wth mproved preamble structures n DVB-T2 are ntroduced to overcome such a poor channel condtons. n 1] 3], modfed coarse synchronzaton and offset estmaton wth a trangle correlaton s presented to provde the mproved performance n DVB-T2 system. n 4], authors presented preamble based dstance detecton nsertng tranng sequences n the frequency doman, whch can enhance the transmsson sgnalng performance and decrease the computatonal complexty. Authors n 5] proposed an mproved transmsson parameter sgnalng (TPS) scheme utlzng the phase nformaton obtaned from the cross-correlaton between dscrete Fourer transform (DFT)-spread Chu sequences. ecently, the requrements of more hgh qualty and varous servces, such as an ultra-hdtv (UHDTV) and a three dmensonal televson (3DTV) are beng ncreased, multple antenna system has been regarded as an nnovated drecton to ncrease the total capacty by a factor of the number of transmt and receve antennas. The most of the prevous research topcs assocated wth multple antenna broadcastng have focused on offerng spatal multplexng and transmt dversty n co-located or dstrbuted fashon. Unlke to prevous research nterests, n ths paper, we propose an mproved preamble transmsson wth hybrd dfferental modulaton to acheve transmt dversty n multple antenna envronments. Frst, we consder the dual-polarzed 2 1 multple-nput sngle-output (MSO) mode due to the advantages of smple mplementaton 7]. Then, we propose a new concept of hybrd dfferental modulaton, consstng of two dmensonal symbol based dfferental encodng, space tme block code (STBC), and dfferental space tme block (DSTBC) decodng to acheve the performance of coherent MSO transmsson. t s shown that spatally superposed sgnals projectng both the nphase and quadrature axes can be perfectly decoupled by explotng the quaternomc form at the destnaton. For the comparson purpose, we also analyze the performance of coherent BPSK, dfferental BPSK and hybrd dfferental BPSK for the transmt dversty MSO system. By usng the proposed dfferental modulaton technology, t s shown that the proposed preamble can sgnalng ndependent 7 bt preambles (total 14 bts) and provde at least 3 db SN gan compare to DVB-T2 SSO P1 symbol n the mult-path fadng channels. Fnally, we accomplsh the performance evaluatons n practcal moble broadcastng scenaros. Manuscrpt receved March 9, 2015; revsed June 28, 2015; accepted July 22, Date of publcaton August 25, 2015; date of current verson December 5, Ths work was supported by the Samsung Electroncs Company Ltd., under the outsourcng development plan of physcal layer framework for the next-generaton broadcastng standardzaton. (Correspondng author: Jong-Soo Seo.) Z. Ku, J. S. Han, J. M. Cho, and J. S. Seo are wth the Department of Electrcal and Electronc Engneerng, Yonse Unversty, Seoul , Korea (e-mal: ku0921@yonse.ac.kr; hjs4015@yonse.ac.kr; cho_jm@yonse.ac.kr; jsseo@yonse.ac.kr). S. Jeon s wth the Techncal esearch nsttute, Korean Broadcastng System, Seoul , Korea (e-mal: jeonsh@kbs.co.kr). J. Park and Y. Oh are wth the Standard and Technology Enablng Team, DMC esearch and Development Center, Samsung Electroncs Company Ltd., Suwon , Korea (e-mal: jsjoo.park@samsung.com; young1394.oh@samsung.com). Color versons of one or more of the fgures n ths paper are avalable onlne at Dgtal Object dentfer /TBC P1 SYMBOL EVEW N DVB-T2 SYSTEM n ths secton, we brefly revew the P1 symbol n DVB-T2 system before ntroducng our proposed preamble. A. Overvew of P1 Symbol Preamble P1 s placed at the begnnng of every DVB-T2 sgnal frame. Accordng to the DVB-T2 standard specfcaton 8], P1 symbol has four man purposes. Durng the ntal scannng of the receve sgnal, t s used to recognze the T2 sgnal much faster nstead of the whole T2 frame. t can be dscrmnated from the other sgnals n the future extenson frame (FEF) to dentfy tself as a preamble of T2 frame c 2015 EEE. Personal use s permtted, but republcaton/redstrbuton requres EEE permsson. See for more nformaton.

2 724 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE 2015 Fg. 2. Double correlaton structure of DVB-T2. Fg. 1. (a) Actve carrer dstrbuton of P1 symbol, (b) C-A-B structure of P1 symbol. P1 symbol wll help the ntalzaton process to detect transmsson parameters such as FFT sze, G sze and transmsson type (SSO/MSO), etc. P1 symbol enables the recever to make fne tme and frequency synchronzatons. B. Generaton of P1 Symbol The P1 symbol n DVB-T2 conssts of two sgnalng felds, that s 3-bt sgnalng S1 and 4-bt sgnalng S2. The extended S1 and S2 sequences are generated based on eght orthogonal complementary sequences of length 64 and sxteen orthogonal complementary sequences of length 256, correspondng to the reference table of S1 and S2 8]. Two 64-length S1 sequences are attached at both sdes of 256-length S2 sequence to compose a sgnalng sequence of length 384. After dfferental bnary phase shft keyng (DBPSK) modulaton and scramblng, sgnalng sequences are mapped nto 384 actve subcarrers accordng to the carrer dstrbuton sequence (CDS) pattern 8]. As shown n Fg. 1(a), the number of avalable carrer of P1 symbol s 853, where only 384 carrers are actvated wthn 6.83 MHz n the mddle of the nomnal bandwdth 7.61 MHz, and the other carrers are nullfed. Ths carrer allocaton strategy makes P1 symbol robust to large carrer frequency offset (CFO). For example, P1 symbol can be detected even the CFO s up to 500 khz snce the actve carrers stll stay wthn the nomnal bandwdth. After nverse fast Fourer transform (FFT), the P1 symbol n tme doman of sze 1024 (part A n Fg. 1(b)) s encapsulated as 2K OFDM symbol wth two guard ntervals (part C and B ). The encoded P1 symbol P k can be expressed as P k A ej2πfshk, 0 k < 542 P k = P k 542 A, 542 k < 1566 (1) P k 1024 A e j2πfshk, 1566 k < 2048, where P k A s the baseband sgnal of part A, and f SH = 1/1024 ndcates the frequency shft to mprove the robustness of P1 symbol appled to part C and part B. C. Detecton of P1 Symbol At the recever, the symbol tme offset (STO) and fractonal CFO (fcfo) can be estmated and compensated by usng the double correlaton scheme as llustrated n Fg. 2. Here, the receved part A wll be transformed to the frequency doman sgnal by 1K FFT. n frequency doman, the nteger CFO (CFO) estmaton can be done by correlatng the receved sgnal and CDS pattern, and then the estmated sequences are extracted from the actve carrers. Fnally, the S1 and S2 bt can be decoded wth the ad of the cross-correlaton between the receved sequences and the stored S1, S2 modulaton patterns.. POPOSED PEAMBLE STUCTUE A. Proposed Preamble s Transmsson Structure The key technology of our proposed preamble s based on the hybrd dfferental modulaton as descrbed n Fg. 3. To clarfy, we restrct our system model to 2 1 co-located dual-polarzed MSO system snce the extenson to MMO can be a straght forward applcaton. Smlar to DVB-T2 preamble transmsson, 3-bt sgnalng S1 and 4-bt sgnalng S2 are generated to 384-length modulaton sgnalng sequence (MSS) by the same modulaton pattern. The conventonal DBPSK sgnal for the th ( = 0, 1,...,383) ndex s encoded by D = D 1 Mss, (2) where D represents the dfferentally encoded symbol, Mss denotes the 384-length MSS sequence where Mss { 1, 1}. t s sgnfcantly noted that the data nformaton n (2) stays on the n-phase axs ( axs). Snce the performance of dfferental modulaton s rapdly deterorated as ncreasng the modulaton order 16], only DBPSK transmsson s consdered as an acceptable scheme for practcal scenaro. Fg. 4 shows the constellaton of DBPSK, magnary DBPSK (DBPSK), and dfferental quadrature phase shft keyng (DQPSK), respectvely. As llustrated n Fg. 4(c), 8 constellaton ponts n the complex plane are observed for DQPSK. Due to the nherent characterstcs of magnary DPSK, only bnary bts on quadrature axs (Q axs) can be conveyed even though 4 constellaton ponts are transmtted. The combnatons of DBPSK and DBPSK transmsson are completely dfferent to the DQPSK, and t s mpossble to transmt DBPSK and DBPSK sgnals together by usng any conventonal schemes because of the constellaton nterferences n axs. Our proposed hybrd dfferental modulaton can avod constellaton nterferences by combnng symbol-based dfferental modulaton of DBPSK and DBPSK wth a STBC encodng, and a dfferental space-tme block code (DSTBC) decodng, whch wll be dscussed n the next subsectons. Specfcally, ndependent 384-length MSS sequences wth another 7 bt (S1 and S2 n Fg. 3) sgnalng are parallel encoded as followng D = j D 1 Mss, (3) where j = 1. Then the constellaton of encoded sequence D can be mapped nto Fg. 4(b). The nformaton stays n both axs and Q axs. Here, the 384-length MSS sequence Mss s encoded to

3 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE Fg. 3. Transmt block dagram of the proposed preamble. proposed model s restrcted to 2 1 MSO model, we defne E s = 1 and M t = 2 for more clear presentaton. Thus, h 1 and h 2 represent the channel coeffcents from dual-polarzed antennas. Fg. 4. Sgnal constellaton of (a) DBPSK, (b) magnary DBPSK, and (c) DQPSK. D by DBPSK and the other Mss s encoded nto D by DBPSK. Then, both of these two dfferentally encoded sequences perform a same generaton structure followed by scramblng and actve carrers paddng referrng to Fg. 3. After the sequences paddng to 1K carrers, the frequency doman preamble sgnals can be represented by P f and P f (f = 0, 1,..., 1023), respectvely. Accordng to the STBC encodng rule 10], all those symbols are grouped nto pars P f, P f ]T (where ] T denotes the transpose operaton), whch are processed by space-tme block encoder as P f ] P f P f P f ] P f P f, (4) where ( ) denotes the complex-conjugate operaton and ndcates a mappng functon to enable STBC encodng. After FFT operaton, the tme doman sgnal for the lth ndex can be represented as p l r p l ] p l p l (l = 0, 1,...,1023). Takng the same procedures of r C-A-B structure to the proposed preamble wth guard ntervals, the p k baseband sgnal matrx can be expressed as p k ] p k p k,where k = 0, 1,...,2047 and p k p k r ej2πfshk, 0 k < 542, = p k 542 r, 542 k < 1566, (5) p k 1024 r e j2πfshk, 1566 k < Wth two transmt antennas, and one receve antenna, the receved sgnals n two consecutve tme slots n and n + 1 for the kth sample can be represented as ] y k n y k E ] s n+1 = h k M 1 h k p k p k ] ] 2 t p k p k + z k 1 z k 2, (6) where E s s the average power for each transmt antenna, M t ndcates the number of transmt antenna, and z k 1 and zk 2 denote addtve whte Gaussan nose (AWGN) of CN (0,σz 2) where Ezk 1 zk 1 ] = σ z 2,and E ] stands for the expectaton operaton. Snce we assumed that our B. Proposed Preamble s ecever Structure ecever transforms one of the receved symbol y k n+1 to yk n+1, then (6) can be equvalently treated as y k ] n h k y k = η 1 h k ] p k ] 2 z k ] n+1 h k 2 h k 1 p k + 1 z k, (7) 2 where η = Es M t. Noted that we once agan transform (7) nto quaternonc form 11] to perform dfferental STBC decodng. n partcular, our proposed receved sgnal matrx can be rewrtten as y k n y k ] n+1 h k y k n+1 y k = η 1 h k ] 2 p k p k ] n h k 2 h k 1 p k p k }{{}}{{}}{{} Y k H k P k z k + 1 z k ] 2. (8) z k 2 z k 1 }{{} Z k The receved sgnal mposed by tme and frequency offsets durng the kth transmsson sample tme can be expressed as Y k+δ e j2π(ε f +ε )k/n ỹk = n ỹ k ] n+1 ỹ k n+1 ỹ k, (9) n where the receved sgnal element wth tme and frequency shfts can be represented as ỹ k n = yk+δ n e j2π(ε f +ε )k/n,andn = Here, dstorton parameters δ, ε f and ε represent STO, fcfo and CFO effects, respectvely. n order to estmated the STO and fcfo and also to decode S1 and S2 sequences, the double correlaton scheme n SSO DVB-T2 (Fg. 2) can be used. STO as well as CFO compensatons and dfferental STBC decodng processes are explaned as follows: 1) STO Compensaton: n (9), t s observed that the whole receved symbols have the same STO and CFO effects durng the transmsson tme, thus we consder only one of the receved symbol ỹ k n (k = 0, 1,...,2047) as the nput of the correlator, nstead of the whole receved matrx Y k to reduce complexty. Specfcally, the correlaton outputs of C and B branches C (t) and B (t) for the tth arbtrary sample tme can be obtaned by C (t) = B (t) = N 1 ỹ t+l n e j2πf SHt ỹ (t+l+t C ) n /N l=0 N 1 ỹ (t+l+t B) n ỹ t+l n e j2πf SHt /N, (10) l=0

4 726 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE 2015 Fg. 5. Absolute value of output for (a) C branch correlator (b) B branch correlator (c) total correlator. where the delay coeffcents for each branch are T C = 542, T B = 482, and N = As a result, the effect of STO can be estmated by δ = arg max C (t) B (t) ], (11) t where stands for the absolute operaton. Fg. 5 shows the absolute value of each correlator s output accordng to tme samples. t s noted that the total output of the correlator has a clear ndcaton to estmate the tmng offset. 2) Fractonal CFO Compensaton: Fractonal frequency offset can be estmated by consderng the angle of the correlaton output n the tme doman. From (10), the effect of fcfo s estmated by ˆε f = arg C( δ) B ( δ)], (12) 2π where arg( ) denotes the phase angle of complex number. STO and fcfo compensatons can be readly acheved as Y k e j2πε k/n = Y k+δ ˆδ e j2π(ε +ε f )k/n e j2π ˆε f k/n. (13) 3) nteger CFO Compensaton: Snce the recever prelmnary performs STO and fcfo estmatons and compensatons, the guard nterval parts C and B are dscarded. Let us defne the remanng part A for the pth tme ndex as Y p e j2πεp/n (p = 0, 1,...,1023) from Y k e j2πεk/n (k = 542, 544,...,1565). We take the FFT operaton to transform the part A nto frequency doman, then the part A n frequency doman for the mth frequency grd s Y m, and each entry of Y m+ε Ỹm = n Ỹn+1 m ] Ỹn+1 m Ỹn m,whereỹn m s the frequency doman receved sgnal affected by CFO,.e., Ỹn m = Ym+ε n. As a result, the nteger CFO can be estmated by observng the correlaton result between the receved sgnal and CDS pattern as 6] ˆε = max Ỹ s+r r n Ỹ n (s+r), (14) s S where S s the set of accurate plot sub-carrers of CDS patterns, and Ỹn s+r represents the receved symbol on carrer s + r. The searchng parameter r must be an nteger wthn the possble range of frequency offset. The nteger CFO compensaton can be acheved as Y m = Y m+ε ˆε. (15) Upon completng the nteger CFO compensaton, the receved symbols can be unpadded from the 1K subcarrers and then descrambled. Note that all of those processes must be done n block unt, n order to enable the dfferental STBC decodng. 4) Dfferental STBC Decodng: Let us defne the receved preamble matrx n frequency doman after descramblng as Y ( = 0, 1,..., 383). Then, the equvalent system model can be represented as Y = ηh D + Z,where H H = 1 H2 H2 H1 ] D = D D D D ] Z = Z 1 Z2 Z2 Z1 ]. (16) Assumng that the channel states are constant over the transmsson of two consecutve block tmes,.e., H 1 = H, then the correlaton between H 1 and H can be perfectly decoupled owng to the orthogonal propertes as H 2 = H ( 1) H = ( H1 2 + H2 2 ) 2. Here, ( ) denotes the Hermtan operaton, and 2 s the dentty matrx of sze 2. Then, the dfferental STBC decodng can be performed as Y ( 1) Y = η 2 D ( 1) H ( 1) H D + Z = η 2 H 2 D ( 1) D + Z ( H η 2 2 H ) 2 ( D ( 1) D = + D ( 1) ) D + Ż1 α ( H η 2 2 H ) ( 2 D D 1 + D 1 D ) + Ż2, β (17) where the equalty of η 2 D ( 1) H ( 1) H D + Z = η 2 H 2 D ( 1) D + Z s met f and only f H 2 denotes a dagonal matrx. The unknown Ż nose matrx Z ndcates the effectve nose matrx,.e., Z = 1 Ż3 ] Ż2 Ż4, whose entres are Ż1 = η D ( 1) (H ( 1) 1 Z1 +H 1 2 Z2 )+η(z( 1) 1 H1 +Z 1 2 H2 ) D +2σ z 2, Ż2 1 = η D (H ( 1) 1 Z1 + H 1 2 Z2 ) + η(z( 1) 2 H2 + Z 1 H 1 ) D + 2σz 2, Ż 3 = η D ( 1) (H ( 1) 2 Z2 + H 1 1 Z1 ) η(z( 1) 1 H1 + Z2 1 H2 ) D + 2σz 2, and Ż 1 4 = η D (H( 1) 2 Z2 + H 1 1 Z1 ) + η(z ( 1) 2 H2 + Z 1 H 1 ) D + 2σ z 2, respectvely. n (17), we defne α = η 2 ( H1 2 + H2 2 )( D ( 1) D + D ( 1) D )+Ż3 and β = η2 ( H1 2 + H2 2 )( D 1 D 1 + D D )+ Ż4 to represent the entres (1,2) and (2,2), respectvely. t s observed that all entres perform the same dfferental decodng for each preamble sequence. Therefore, we take the frst meanngful entry n (17) of r,.e., r = η 2 ( H1 2 + H2 2 )( D ( 1) D + D ( 1) D ) + Ż 1. Substtutng (2) and(3) ntor and after some manpulatons, we obtan ( H r = η 2 2 H ) 2 ( Mss + j Mss ) + Ż1. (18) Fnally, we can separately decode 384-length MSS sequences Mss and Mss by takng the real and magnary part of r ( = 0, 1,...,383),.e., Mss = ( r ) Mss = (r ), (19) where ( ) and ( ) ndcate the real and magnary part of the sgnal, respectvely. As a result, the S1 and S2 bts are ndependently decoded by observng the correlaton of Mss, and the modulaton pattern. V. PEFOMANCE EVALUATONS n ths secton, we accomplsh the performance evaluatons to reveal the gan of our proposed preamble transmsson. A. Performance of Hybrd Dfferental Modulaton Frstly, we compare the performance of varous dfferental modulatons n order to verfy the robustness of our hybrd dfferental modulaton. Fg. 6 llustrates the comparsons of BE performance of DBPSK, DBPSK and hybrd dfferental BPSK over AWGN and aylegh flat fadng channels. We can see that BE performances of DBPSK and DBPSK are completely the same to each other over both channels. However, the hybrd dfferental BPSK has sgnfcantly mproved the BE performance.

5 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE Fg. 6. BE performances of DBPSK, DBPSK and hybrd dfferental BPSK n AWGN and aylegh fadng channels. Fg. 8. SE performance of DVB-T2 P1 and the proposed preamble n statc TU-6 and DVB-NGH outdoor channels. Fg. 7. BE performances of hybrd dfferental BPSK, coherent BPSK 10] and dfferental BPSK 14] for MSO system over aylegh flat fadng channel. Fg. 7 depcts the BE performance of hybrd dfferental BPSK, coherent BPSK 10] and dfferental BPSK 14] for MSO system over aylegh fadng channel. t s clearly shown that the dfferental detecton has a 3 db performance degradaton compared to the coherent detecton, whch s already verfed n 14]. However, t s sgnfcantly notced that hybrd dfferental BPSK acheves the same BE performance wth coherent BPSK. Here, 3dB performance degradaton can be elmnated by explotng our proposed hybrd dfferental modulaton snce the nose s not enhanced as n (17). n addton, low computatonal complexty can be acheved snce the recever does not requre channel estmatons. B. Performance of Proposed Preamble We analyze the sgnalng error rate (SE) performances of DVB-T2 P1 and proposed preamble over mult-path fadng channels. Specfcally, typcal urban 6-path channel model (TU-6) 9] andthe DVB-NGH 8-tap outdoor channel model 15] were randomly generated by havng a combnaton of Jake s spectrum. To actualze ntra-tap correlaton and cross-polarzaton mparment of antennas, two co-located transmt antennas were consdered. The antenna Fg. 9. SE performance of DVB-T2 P1 and the proposed preamble n TU-6 and DVB-NGH outdoor channels wth 20 Hz Doppler shft. correlaton coeffcent was set to 0.12, and the lne-of-sght (LOS) factor K was consdered accordng to the varous scenaros. t s assumed that the same transmt confguraton of both P1 and proposed preamble are pre-determned. For nstance, the duratons of both preambles were 224 μs n 8 MHz nomnal bandwdth. Both of the transmtted sgnals consst of two 2K OFDM random symbols (the same length wth the preamble) before and after the tme doman baseband preamble. We set the STO to δ = 60, the normalzed CFO as ε = 5.5 for the synchronzaton. t s observed n (19) that our proposed transmsson can transmt the same or dfferent preambles.e., S1 = S1 and S2 = S2. nterestngly, the same SE performance can be acheved snce the SE of each real and magnary part symbol are ndependently calculated. Fg. 8 shows the SE performance of DVB-T2 P1 and proposed preamble n statc TU-6 and DVB-NGH outdoor channels, whereas Fg. 9 compares the correspondng performances wth 20 Hz Doppler shft. t s clearly observed that the proposed preamble can provde up to 4 db SN gan compared to the conventonal DVB-T2 P1 symbol. When the Doppler shft s 20 Hz, the proposed

6 728 EEE TANSACTONS ON BOADCASTNG, VOL. 61, NO. 4, DECEMBE 2015 Fg. 10. SE performance of DVB-T2 P1 and the proposed preamble n DVB-NGH outdoor channel wth 20 Hz Doppler shft and LOS factor K=4. preamble stll can provde around 3 db and 4 db gans for DVB-NGH and TU-6 channels, respectvely. Here, t s already verfed n 4] that the poor performance of preamble transmsson n moble fadng channels. Fg. 10 llustrates the performance of the proposed preamble scheme n DVB-NGH outdoor channel n hgh LOS envronments,.e., K = 4. t s found that both conventonal DVB-T2 P1 symbol and proposed preamble become robust under the strong LOS envronments. Moreover, our proposed preamble stll acheves the 4 db SN gan compare to the conventonal DVB-T2 P1 symbol. V. CONCLUSON n ths paper, we have presented an advanced preamble, whch s modulated by a novel hybrd dfferental modulaton to provde transmt dversty gan for the dual polarzed DVB-T2 MSO system. Our smulaton results have clearly demonstrated that our proposed preamble has a sgnfcant mproved performances compared to the conventonal P1 symbol n DVB-T2 system over several practcal moble broadcastng channels. Specfcally, as much as 4dB SN gans are observed n TU-6 and DVB-NGH outdoor channels wth and wthout 20 Hz Doppler shft, respectvely. EFEENCES 1] J. G. Doblado, V. Baena, A. C. Ora, D. Perez-Calderon, and P. Lopes, Coarse tme synchronzaton for DVB-T2, Electron. Lett., vol. 46, no. 11, pp , May ] M. otolon, S. Tomasn, and L. Vangelsta, On correlaton-based synchronzaton for DVB-T2, EEE Commun. Lett., vol. 14, no. 3, pp , Mar ] A. Vemann et al., mplementaton-frendly synchronzaton algorthm for DVB-T2, Electron. Lett., vol. 46, no. 4, pp , Feb ] L. He, Z. Wang, F. Yang, S. Chen, and L. Hanzo, Preamble desgn usng embedded sgnalng for OFDM broadcast systems based on reduced complexty dstance detecton, EEE Trans. Veh. Technol., vol. 60, no. 3, pp , Mar ] J. M. Cho et al., mproved transmsson parameter sgnalng scheme utlzng cross-correlaton propertes of DFT-spread Chu sequence, n Proc. EEE BMSB, Bejng, Chna, Jun. 2014, pp ] T. Jokela, M. Tupala, and J. Paavola, Analyss of physcal layer sgnalng transmsson n DVB-T2 systems, EEE Trans. Broadcast., vol. 56, no. 3, pp , Sep ] J. S. Han, J. S. Baek, and J. S. Seo, MMO-OFDM transcevers wth dual-polarzed dvson multplexng and dversty for multmeda broadcastng servces, EEE Trans. Broadcast., vol. 59, no. 1, pp , Mar ] Dgtal Vdeo Broadcastng (DVB); Frame Structure, Channel Codng and Modulaton for a Second Generaton Dgtal Terrestral Televson Broadcastng System (DVB-T2), ETS Standard EN , Apr ] Dgtal Vdeo Broadcastng (DVB); mplementaton Gudelnes for a Second Generaton Dgtal Terrestral Televson Broadcastng System (DVB-T2), ETS Standard TS , Aug ] S. M. Alamout, A smple transmtter dversty scheme for wreless communcatons, EEE J. Sel. Areas Commun., vol. 16, no. 8, pp , Oct ] S. Dggav, N. Al-Dhahr, A. Stamouls, and A.. Calderbank, Dfferental space-tme codng for frequency-selectve channels, EEE Commun. Lett., vol. 6, no. 6, pp , Jun ] N. Al-Dhahr, A new hgh-rate dfferental space-tme block codng scheme, EEE Commun. Lett., vol. 7, no. 11, pp , Nov ] P. Tarasak, H. Mnn, and V. K. Bhargava, Dfferental modulaton for two-user cooperatve dversty systems, EEE J. Sel. Areas Commun., vol. 23, no. 9, pp , Sep ] V. Tarokh and H. Jafarkhan, A dfferental detecton scheme for transmt dversty, EEE J. Sel. Areas Commun., vol. 18, no. 7, pp , Jul ] P. Moss, DVB-NGH Channel Models, document TM-NGH063, Dgt. Vdeo Broadcast., Geneva, Swtzerland, Nov ] S. Haykn and M. Moher, ntroducton to Analog and Dgtal Communcatons. Hoboken, NJ, USA: Wley, ] Y. S. Cho, J. W. Km, W. Y. Yang, and C. G. Kang, MMO-OFDM Wreless Communcatons Wth MATLAB. Sngapore: Wley, 2010.