All Digital Multi-Gigabit Baseband P. Sandeep M. Seo M. Rodwell - PowerPoint PPT Presentation

Joint Channel and Mismatch Correction for OFDM Reception with Time-interleaved ADCs All Digital Multi-Gigabit Baseband P. Sandeep M. Seo M. Rodwell U. Madhow ECE Dept, UCSB

ECE Dept, UCSB

All Digital Baseband “Digital Baseband” Receiver cos (wt ) ADC Synchronization Equalization Demodulation Decoding ECE Dept, UCSB

Signal Processing Issues Analog –to-Digital Converter (ADC) Analog In Digital Out Sampling rate & Output resolution ECE Dept, UCSB

Large bandwidth ! ECE Dept, UCSB

Need for Resolution REFLECTOR TRANSMITTER RECEIVER ECE Dept, UCSB

ADCs available Speed 100 KHz 10MHz 100MHz 1 GHz Resolution 24 bit 18 bit 15 bit 8 bit Power 1-10mW 10-100mW 100mW-1W 1-10W ADC Survey by Le et al, IEEE Sig. Proc. Mag. Nov’05 ECE Dept, UCSB

High speed, moderate resolution ADCs ? ECE Dept, UCSB

Solution Time-interleaving ECE Dept, UCSB

Issues ? • Mismatch between parallel channels ECE Dept, UCSB

Mismatch model Gain and timing mismatch Munkyo Seo, Rodwell & Madhow, IEEE Tran. Mic. Tech. March 2005 ECE Dept, UCSB

TI ADCs for multi-Gigabit Communication ECE Dept, UCSB

Conventional approach Make a better ADC Make a better ADC TI ADC : Status and Future Directions, by Vogel et al ISCAS 06 ECE Dept, UCSB

Our approach to mismatch Adapt mismatch correction to Communication signal ECE Dept, UCSB

Example : TI-ADC in OFDM system ECE Dept, UCSB

OFDM transceiver cos (wt ) Training DAC Data OFDM transceiver Data ’ cos (wt ) TI ADC Training ’ Training ECE Dept, UCSB

Structure of mismatch induced interference ECE Dept, UCSB

Signal at sub-carrier ‘0’ ECE Dept, UCSB

Zero-forcing Equalization Orthogonal to Signal vector interference space # of ADCs = 8 # of interferers = 8 Interference space ECE Dept, UCSB

Equalization performance • 16 QAM, OFDM • 8 parallel-ADCs • 10% mismatch (~20ps, 5GSa/s) ECE Dept, UCSB

Estimation of mismatch ECE Dept, UCSB

Joint channel-mismatch estimation Received Training Iterations ECE Dept, UCSB

Accuracy in estimates ECE Dept, UCSB

Hardware Experiment ECE Dept, UCSB

Setup 1 4x100 MSa/s ADCs Received Baseband (2x) 14 bit sampled data 1 On TI ADC testbed of Dr. Munkyo Seo, Prof Rodwell’s Lab ECE Dept, UCSB

Results ECE Dept, UCSB

Conclusions Gigabit Wireless Time-interleaved ADC Mismatch compensation Joint demodulation & mismatch correction ECE Dept, UCSB

THANKS THANKS

Flash ADC Flash ADC Comparators Digital logic 2 N comparators Analog Static power Input 2 bits 00 01 11 10 ECE Dept, UCSB

SAR ADC Successive Approximation Register 00 01 11 10 ECE Dept, UCSB

MIMO Receiver (2k+1)T ADC 1 2kT ADC 2 RECEIVER (2k+1)T ADC 3 2kT ADC 4 ECE Dept, UCSB