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The Next Generation Challenge for Software Defined Radio

The Next Generation Challenge for Software Defined Radio. Mark Woh 1 , Sangwon Seo 1 , Hyunseok Lee 1 , Yuan Lin 1 , Scott Mahlke 1 , Trevor Mudge 1 , Chaitali Chakrabarti 2 , Krisztian Flautner 3 1 Advanced Computer Architecture Lab, University of Michigan

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The Next Generation Challenge for Software Defined Radio

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  1. The Next Generation Challenge for Software Defined Radio Mark Woh1, Sangwon Seo1, Hyunseok Lee1, Yuan Lin1, Scott Mahlke1, Trevor Mudge1, Chaitali Chakrabarti2, Krisztian Flautner3 1Advanced Computer Architecture Lab, University of Michigan 2Department of Electrical Engineering, Arizona State University 3ARM, Ltd.

  2. 3G Wireless Large Coverage Outdoor - High Mobility Up to 14Mbps

  3. Expected Wireless Growth • The growth of wireless will require more bandwidth

  4. 4G Wireless Pico Cells Macro Cells Isolated HotSpots – 1Gbps Coverage Indoor – Very Low Mobility Large Coverage – 100Mbps Coverage Outdoor - High Mobility • What we need • Adaptive high performance transmission system • Great candidate for SDR

  5. Next Generation Wireless – 4G • 3 Major Components to 4G • Modulation/Demodulation • Multiple-Input Multiple-Out (MIMO) • Channel Decoder/Encoders

  6. Modulation - OFDM • Can be implemented with IFFT/FFT

  7. Major Component of Modulation – FFT/IFFT • Very wide data level parallelism • Requires complex operations

  8. MIMO (Multiple Input – Multiple Out) • Previously we used single antenna systems • Now we use multiple antennas to increase the channel capacity • Diversity - High Reliability • Space Time Block Codes (STBC) • Multiplexing – High Throughput • Vertical-BLAST (V-BLAST)

  9. Space Time Block Codes (STBC)

  10. STBC • Requires complex operations • Low Data Movement • Highly parallelizable

  11. Vertical-BLAST (V-BLAST)

  12. V-BLAST • Implementation Based on Square Root Method for V-BLAST • Original requires repeated pseudo-inverse calculation for finding the strongest signal • This algorithm has reduces complexity • Complexity • Requires matrix operations on complex numbers • Many Matrix Transformations

  13. Channel Decoding • 3G Technologies in 4G • Viterbi • Turbo Decoder • New to 4G • LDPC • Better performance characteristics compared to Turbo and Viterbi

  14. LDPC

  15. LDPC • Min-Sum Decoding Used • Regular LDPC code • Can get benefit from Wide SIMD • Can do the Bit Node and Check Node • Alignment of Check and Bit nodes is a problem

  16. SODA PE Architecture • SIMD – 32 Wide, 16-bit datapath, Predicate Execution

  17. 4G Workload on SODA • 100 Mbps 4G requires 8Ghz SODA PE • 1 Gbps 4G requires 20Ghz SODA PE

  18. SODA With Technology Scaling

  19. SDR Challenges In 4G • We can’t do any of 4G with technology scaling on one core • Would 8GHz cores even be an energy efficient solution? • What about 1Gbps? • Are we ever going to get a 20GHz core? • Cannot rely on technology scaling to give us 4G for free • 4G SDR will require algorithmic and architectural innovations

  20. 4G Algorithm-Architectural Co-design • Architectural improvements (SODA II) • Specialized functional units • CISC-like complex arithmetic operations • Specialized data movement hardware • Less strain on the memory system • Wider SIMD • How wide can we go? • More PEs • What does the interconnect look like? • Algorithmic optimization through parallelization • Reduce intra-kernel communication • Reduce memory accesses • Arithmetic is much cheaper than data movement

  21. Thanks • Questions?

  22. Successive Cancelling for V-BLAST • V-BLAST successive interference cancelling (SIC) • The ith ZF-nulling vector wi is defined as the unique minimum-norm vector satisfying • Orthogonal to the subspace spanned by the contributions to yi due to the symbols not yet estimated and cancelled and is given by the ith row of

  23. Alamouti Scheme • Assumption: the channel remains unchanged over two consecutive symbols • Rate = 1 • Diversity order = 2 • Simple decoding

  24. Advantages of Software Defined Radio • Multi-mode operations • Lower costs • Faster time to market • Prototyping and bug fixes • Chip volumes • Longevity of platforms • Enables future wireless communication innovations • Cognitive radio

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