Khảo Sát Ảnh Hưởng Của Dịch Tần Đến Hệ Thống Mb Ofdm

ĐA ̣ I HO ̣ C QUÔ ́ C GIA HA ̀ NÔ ̣ I TRƯƠ ̀ NG ĐA ̣ I HO ̣ C CÔNG NGHÊ ̣ LƯU VĂN HOAN KHO ST NH HƯNG CA DCH TÂ ̀ N ĐÊ ́ N HÊ ̣ THÔ ́ NG MB-OFDM LUÂ ̣ N VĂN THA ̣ C SI ̃ H Ni - 2011  -OFDM                                                  2011   n :                                     -OFDM       :                       :         :      - 2011 iv MC LC    i      ii T iii  iv       vi      viii  ix  x CHƯƠNG 1: GIƠ ́ I THIÊ ̣ U 1.1.      - 1 - 1.1.1.        - 1 - 1.1.2.  - 1 - 1.1.3.  - 4 - 1.2.  - 5 - 1.3.   - 5 - 1.4.          - 6 - CHƯƠNG 2: HÊ ̣ THÔ ́ NG MB-OFDM 2.1.   -OFDM - 7 - 2.1.1.    - 7 - 2.1.2.            - 8 - 2.1.2.1.   - 9 - 2.1.2.2.  10 - 2.2.  12 - 2.3.        14 - 2.4.           -OFDM 17 - 2.4.1.  18 - 2.4.2.  18 - 2.5.     -OFDM      20 - 2.6. -OFDM 24 - 2.6.1.   30 - 2.6.2.  31 - v CHƯƠNG 3: ƯC LƯNG DCH TN TRONG H THNG MB-OFDM 3.1.                35 - 3.2.            39 - 3.3.  47 - 3.4.  52 - CHƯƠNG 4: KÊ ́ T LUÂ ̣ N V HƯNG NGHIÊN CU TIÊ ́ P THEO 4.1.    54 - 4.2.      55 - 4.2.1.  55 - 4.2.2. MIMO Multiband OFDM 55 -  - 56 - : g MB-OFDM - 58 - Kho st nh hưng ca dch tn đn h thng hp kênh phân tn s trư ̣ c giao đa da ̉ i (MB-OFDM)  ,          ,             luuhoannd@gmail.com TS Ngu        ,                       hieunt@vnu.edu.vn Từ khóa – UWB, OFDM, MB-OFDM, Carrier Frequency Offset.    -            q-368         (WPAN),     UWB    3100  10600 MHz,                480   . I.   I   U         14  (subband),              528 MHz.           1 trong 6  .              1          . II. MÔ NH     NG MB-OFDM             -          .              -          (TFC)   y sang  .    -            802.15.3                       .  (CFO)         ,             (ICI)      . III.   T N C   NG CH   N        2                 .               (do CFO gây ra)  2    . IV.   T  MÔ NG    T   N K           5 mô  AWGN, CM1  CM4, c ,      ,   .           ,                       (ICI) (   CFO,    ).    ,                   .        1   , trên kênh CM4 . H                      .         , ,          (= 0.04 %)           .    ,              . TÀI  THAM  [1] W. Pam Siriwongpairat, K. J. Ray Liu, Ultra-Wideband Communications Systems - Multiband OFDM Approach, John Wiley & Sons, Inc, 2008. [2] Paul H. Moose, A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction, IEEE Transactions on Communications, Vol. 42, No. 10, October 1994, trang 2908  2914. [3] Timothy M. Schmidl, Donald C. Cox, Robust Frequency and Timing Synchronization for OFDM, IEEE Transactions on Communications, Vol. 45, No. 12, December 1997, trang 1613  1621. [4] Chin Wee Yak, Zhongding Lei, Tjeng Thiang Tjhung, Maximum likelihood frequency offset estimation and Cramer Rao bound for ultra-wideband (UWB) multi- band OFDM systems, IEEE Vehicular Technology Conference, VTC 2006 Spring, 7-10 May 2006, trang 1929  1934. [5] B. D. Sahu, Debarati Sen, R. V. Raja Kumar and Saswat Chakrabarti, A Frequency Offset Estimation Scheme for OFDM Based UWB Systems, 2006 IEEE Region 10 Technical Conference (IEEE TECON), 14-17 Nov. 2006, HongKong, trang 1 - 4. Studying the efffects of frequency offset on multiband orthogonal frequency division multiplexing (MB-OFDM) systems Luu Van Hoan Electronics Engineering, Electronics and Telecommunications Technology Faculty of Electronics and Telecommunications luuhoannd@gmail.com Dr Nguyen Thanh Hieu Department of Wireless Communications, Faculty of Electronics and Telecommunications University of Engineering and Technology hieunt@vnu.edu.vn Keywords – UWB, OFDM, MB-OFDM, Carrier Frequency Offset. The MB-OFDM systems is standardised by ECMA-368 standard for wireless personal area networks (WPAN) operating at short ranges and high data rates. The systems use all of or a part of the UWB spectrum from 3100 MHz to 10600 MHz. At present, the system support data rates upto 480 Mbps and so on. I. INTRODUCTION The UWB spectrum is diveded into 14 subbands, each with a bandwidth of 528 MHz. At least one of the band groups shall be supported. This standard specifies a Multiband Orthogonal Frequency Division Modulation (MB-OFDM) scheme to transmit information. II. MODEL OF THE MB-OFDM SYSTEM The structures of the transmiter and receiver of the MB-OFDM systems is the same to the one of normal OFDM systems. The primary difference is that the MB-OFDM use the time-frequency code (TFC) to hop between subbands from this symbol to next symbol. The UWB standard channel models specified in the IEEE 802.15.3a are derived froum the Saleh-Valezuela (S-V) model with some minor modifications due to clustering phenomenon. Carrier frequency offset (CFO) causes intercarrier interference (ICI) froum other subcarrier which are now no longer orthogonal with each other. III. THE FREQUENCY OFFSET ESTIMATION SCHEME The phase of the correlation of two symbol which are in packet/frame synchronization part of each packet consist of the information about CFO. The algorithm derives its estimates based on phase differences in the received subcarrier signals of several successive symbol in the preamble. This thesis consider the same CFOs and the same channel responses in different bands. IV. SIMULATION RESULTS AND CONCLUSION With CFO, but not compensating, we can see that as the CFO increases, the BER also increases. The reason is that SNR at the receiver decreases, because the signal after demodulation has ICI. The performance of system is improved significantly when CFO is compesnsated at receiver. When CFO is so small, the accuracy of the CFO estimation is not good. REFERENCES [1] W. Pam Siriwongpairat, K. J. Ray Liu, Ultra-Wideband Communications Systems - Multiband OFDM Approach, John Wiley & Sons, Inc, 2008. [2] Paul H. Moose, A Technique for Orthogonal Frequency Division Multiplexing Frequency Offset Correction, IEEE Transactions on Communications, Vol. 42, No. 10, October 1994, pages 2908  2914. [3] Timothy M. Schmidl, Donald C. Cox, Robust Frequency and Timing Synchronization for OFDM, IEEE Transactions on Communications, Vol. 45, No. 12, December 1997, pages 1613  1621. [4] Chin Wee Yak, Zhongding Lei, Tjeng Thiang Tjhung, Maximum likelihood frequency offset estimation and Cramer Rao bound for ultra-wideband (UWB) multi- band OFDM systems, IEEE Vehicular Technology Conference, VTC 2006 Spring, 7-10 May 2006, pages 1929  1934. [5] B. D. Sahu, Debarati Sen, R. V. Raja Kumar and Saswat Chakrabarti, A Frequency Offset Estimation Scheme for OFDM Based UWB Systems, 2006 IEEE Region 10 Technical Conference (IEEE TECON), 14-17 Nov. 2006, HongKong, pages 1 - 4.