ISSCC 2008 Student Forum

An 18 Gbps 2048-bit 10GBASE-T Ethernet LDPC Decoder

• Tinoosh Mohsenin• Electrical & Computer Engineering, UC Davis• tmohsenin@ucdavis.edu• PhD, graduation date: 2008• Adviser: Professor Bevan Baas• Research areas

• Energy efficient and high performance signal processing and error correction architectures• Multi-gigabit full-parallel LDPC decoders• Many-core processor architecture design

• UC Davis• BS from Sharif University • MS from Rice University

ISSCC 2008 Student Forum

Research Overview

Row processing

Column processing

100001010

010100001

001010100

001100010

100010001

010001100

HH=

• Low Density Parity Check (LDPC) decoders

• Algorithms• Architecture• High energy efficiency• High throughput

• LDPC codes applications• 10 Gigabit Ethernet (10GBASE-T)• WiMAX• Digital Video Broadcasting (DVB-S2)

• T. Mohsenin et al., ICCD, Oct 2006• T. Mohsenin et al., ICASSP, Apr 2007• A. Blanksby et al., JSSC, Mar 2002

Encoder Decoder

Noise

Channel

ethernet cablewirelesshard disk

ISSCC 2008 Student Forum

Multi-Split-Row vs. Standard Decoder

Mem

ColRow

Standard decoder

Multi-Split-Row decoderSp1Sp0 Spn-1

MemMem

Col Col

Mem

ColRowRowRow

SignSp0_1

SignSp1_0

SignSp1_2

SignSp2_1SignSpn-2_n-1SignSpn-1_n-2

H =

11

11

11

11

11

1

1

1

1

11

11

11

11

1

1

11

1 1

1

1

1

1

1

1

11

1

1

1

11 1

1

1

11

1

11

1

1

HSplit-Sp0 HSplit-Sp1 HSplit-Spn-1

H =

11

11

11

11

11

1

1

1

1

11

11

11

11

1

1

11

1 1

1

1

1

1

1

1

11

1

1

1

11 1

1

1

11

1

11

1

1

N columnsrow weight=Wr

N/Spn columnsrow weight=Wr/Spn

N/Spn columnsrow weight=Wr/Spn

N/Spn columnsrow weight=Wr/Spn

ISSCC 2008 Student Forum

0 2 4 6 8 100

0.5

1

1.5

2

2.5

18.2 mm2 8.8 mm2 5.0 mm2

Split-4 decoder

Split-2 decoder

standard decoder

Decoder Implementation Results

10GBASE-T Code

65 nm, 1.3 V

Standard Split-2 Split-4

Split-4 Improve.

Area Utilization 25% 50% 90% 3.6x

Avg. Wire length (μm) 175.2 115.5 73.8 2.4x

Speed (MHz) 12.5 45 133 10.6x

Throughput (Gbps) 1.7 6.1 18.2 10.6x

Energy per bit (pJ/bit) 141 79 46 3.1x

• (2048,1723) LDPC code adopted by 10GBASE-T

This work

Energy per Decoded bit per Iter (pJ/bit/iter)

Nor

mal

ized

Thr

ough

put

per

Are

a (G

bps/

mm

2 )

In the plot:• 65 nm, 0.85 V• Throughput normalized to 15 iterations• Area: quadratically scaled with feature size, adjusted with row and column weights• Speed: linearly scaled with feature size• Energy: linearly scaled with feature size, quadratically scaled with voltage

[1] A. Blanksby et al., JSSC, Mar 2002[2] M. Mansour et al., JSSC, Mar 2006[3] A. Darabiha et al., CICC, Sep 2007

Darabiha

Mansour

Blanksby

Higher performance per

area, and lower energy