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Unit 1 Introduction to Wireless Communication IC. Topics to be covered in this course Introduction to OFDM baseband system designs Reference book: OFDM baseband receiver design for wireless communications by Tzi-Dar Chiueh and Pei-Yun Tsai Physical layer design (PHY)
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Unit 1 Introduction to Wireless Communication IC Institute of Communications Engineering, NCTU
Topics to be covered in this course • Introduction to OFDM baseband system designs • Reference book: OFDM baseband receiver design for wireless communications by Tzi-Dar Chiueh and Pei-Yun Tsai • Physical layer design (PHY) • Finite Impulse Response (FIR) filter design and implementation (2 lectures + 1 lab) • Synchronization circuits (1 lecture + 1 lab) • Fast Fourier Transform (FFT) (2 lectures + 1 lab) • Channel estimation and symbol detection (1 lecture + 1 lab) • From algorithm to bit-true design (1 lecture) • Medium access control (MAC) (3 lectures + 2 labs) • A simplified WiFi MAC • A simply cognitive MAC Department of Communication Engineering, NCTU
Labs are based on the OFDM reference design on Wireless Access Research Platform (WARP) • http://warp.rice.edu/trac/wiki/HardwareUsersGuides/FPGABoard_v2.2 Department of Communication Engineering, NCTU
Hardware features • Xilinx Vertex-4 FPAG: XC4VFX100-FF1517-11 • Logic slices: 42K • DSP48 slices: 160 • Block RAMs: 376 • Power PC cores: 2 PC405 • Tri-mode Ethernet MAC: 3 Department of Communication Engineering, NCTU
DSP slices: refer to Vertex-4 Xtreme DSP User Guide • http://www.xilinx.com/support/documentation/user_guides/ug073.pdf Department of Communication Engineering, NCTU
An OFDM reference designhttp://warp.rice.edu/trac/wiki/OFDMReferenceDesign Department of Communication Engineering, NCTU
Will do a basic point-to-point wireless communications • Virtex-4 (WARP FPGA Board v2.2): OFDM_ReferenceDesign_FPGAv2_v16.1.zip (100MB) • Both projects were built using the latest versions of the 10.1 release of the Xilinx tools (ISE 10.1.03 + IP3, EDK 10.1.03, Sysgen 10.1.3.1386). Department of Communication Engineering, NCTU
Simulink top-level design C:\WARP\OFDM_ReferenceDesign_FPGAv2_v16.1_public\pcores Department of Communication Engineering, NCTU
The PHY circuit and system is realized with Simulink. The entire design is in an mdl file: (ofdm_txrx_supermimo_coded.mdl) which is used to generate the “pcores” for Xilinx platform studie (XPS). • Because of limitations in the number of multipliers in the Virtex-4 FPGA, the decimation filters in the rate_change_filters pcore use non-embedded multipliers. • The rate_change_filter source model is in the repository /ResearchApps/PHY/MIMO_OFDM/Rate Change Filters Department of Communication Engineering, NCTU
1.2 Wireless Channels Institute of Communications Engineering, NCTU
A typical spatial channel model (SCM) used in IEEE 802.11n and 802.16 • There are 6multipaths each of which consists of 20subpaths Department of Communication Engineering, NCTU
Channel impulse responses • For wireless channels, the baseband input-output relationship can be expressed as • If the signal bandwidth is sufficiently narrow such that the channel can be treated as approximately constant over the operating frequency (frequency flat channel), the corresponding input-output relationship simplifies to Department of Communication Engineering, NCTU
Why OFDM • What does it mean by orthogonal frequency division multiplexing? Department of Communication Engineering, NCTU
How can we suppress the multipath effects in an efficient manner? Department of Communication Engineering, NCTU
Guard band v.s. guard interval Department of Communication Engineering, NCTU