Chien-Ching Lin

Design of a power-reduction Viterbi decoder for WLAN applications

In this paper, a 64-state four-bit soft-decision Viterbi decoder with power saving mechanism for high speed wireless local area network applications is presented. Based on path merging and prediction techniques, a survivor memory unit with hierarchical memory design is proposed to reduce memory access operations. It is found that more than 70% memory access can be reduced by taking advantage of locality. Moreover, a low complexity compare-select-add unit is also presented, leading to save 15% area and 14.3% power dissipation as compared to conventional add-compare-select design. A test chip has been designed and implemented in 0.18-/spl mu/m standard CMOS process. The test results show that 30/spl sim/40% power dissipation can be reduced, and the power efficiency reaches 0.75 mW per Mb/s at 6 Mb/s and 1.26 mW per Mb/s at 54 Mb/s as specified in IEEE 802.11a.

A 3.33Gb/s (1200,720) low-density parity check code decoder

In this paper, a (1200,720) LDPC decoder based on an irregular parity check matrix is presented. For achieving higher chip density and less critical path delay, the proposed architecture features a data reordering such that only one specific data bus exists between message memories and computational units. Moreover, the LDPC decoder can also process two different codewords concurrently to increase throughput and datapath efficiency. After chip implementation, a 3.33Gb/s data rate is achieved with 8 decoding iterations in the 21.23mm/sup 2/ 0.18/spl mu/m silicon area. The other 0.13/spl mu/m chip with the 10.24mm/sup 2/ core can further reach a 5.92Gb/s data rate under 1.02V supply.

A 480Mb/s LDPC-COFDM-based UWB baseband transceiver

A low-density parity-check (LDPC) coded OFDM-based UWB baseband transceiver features a semi-regular LDPC CODEC, a parallel pipelined FFT, and a division-free channel equalizer. The chip is implemented in a standard 0.18 /spl mu/m CMOS process and achieves a 480Mbit/s data rate with an energy consumption of 1.2nJ/b.

Design of a Multimode QC-LDPC Decoder Based on Shift-Routing Network

A reconfigurable message-passing network is proposed to facilitate message transportation in decoding multimode quasi-cyclic low-density parity-check (QC-LDPC) codes. By exploiting the shift-routing network (SRN) features, the decoding messages are routed in parallel to fully support those specific 19 and 3 submatrix sizes defined in IEEE 802.16e and IEEE 802.11n applications with less hardware complexity. A 6.22- mm2 QC-LDPC decoder with SRN is implemented in a 90-nm 1-Poly 9-Metal (1P9M) CMOS process. Postlayout simulation results show that the operation frequency can achieve 300 MHz, which is sufficient to process the 212-Mb/s 2304-bit and 178-Mb/s 1944-bit codeword streams for IEEE 802.16e and IEEE 802.11n systems, respectively.

A low-power Reed-Solomon decoder for STM-16 optical communications

In this paper, a low-power Reed-Solomon (RS) decoder for STM-16 optical communications is presented. It mainly contains one (255,239) RS decoder and four 2 K-bit embedded memory for correcting the received codewords. Except the novel syndrome calculator reducing half the syndrome computations, our proposal also features a modified Berlekamp-Massey algorithm in the key equation solver and a terminated mechanism in the Chien search circuit. The (255,239) RS decoder is implemented by 0.25 /spl mu/m CMOS 1P5M standard cells with gate counts of 32.9 K and area of 2.03 mm/sup 2/. Simulation results show our approach can work successfully at the data rate of 2.5-Gbps and achieve 80% reduction of power dissipation on the average.

Turbo Decoder Using Contention-Free Interleaver and Parallel Architecture

This paper introduces a turbo decoder that utilizes multiple soft-in/soft-out (SISO) decoders to decode one codeword. In addition, each SISO decoder is modified to allow simultaneous execution over multiple successive trellis stages. The design issues related to the architecture with parallel high-radix SISO decoders are discussed. First, a contention-free interleaver for the hybrid parallelism is presented to overcome the complicated collision problem as well as reduce interconnection network complexity. Second, two techniques for the high-speed add-compare-select (ACS) circuits are given to lessen area overhead of the SISO decoder. Third, a modification of the processing schedule is made for higher operating efficiency. Two designs with parallel architecture have been implemented. The first design with 32 SISO decoders, each of which processes 2 symbols per cycle, has 160 Mb/s and 0.22 nJ/b/iter after measurement. The second design uses 16 SISO decoders to deal with 4 symbols per cycle and achieves 100% efficiency, leading to 1000 Mb/s and 0.15 nJ/b/iter in post-layout simulation.

A low power turbo/Viterbi decoder for 3GPP2 applications

This paper presents a channel decoder that completes both turbo and Viterbi decodings, which are pervasive in many wireless communication systems, especially those that require very low signal-to-noise ratios. The trellis decoding algorithm merges them with less redundancy. However, the implementation is still challenging due to the power consumption in wearable devices. This research investigates an optimized memory scheme and rescheduled data flow to reduce power consumption and chip area. The memory access is reduced by buffering the input symbols, and the area is reduced by reducing the embedded interleaver memory. A test chip is fabricated in a 1.8 V 0.18-/spl mu/m standard CMOS technology and verified to provide 4.25-Mb/s turbo decoding and 5.26-Mb/s Viterbi decoding. The measured power dissipation is 83 mW, while decoding a 3.1 Mb/s turbo encoded data stream with six iterations for each block. The power consumption in Viterbi decoding is 25.1 mW in the 1-Mb/s data rate. The measurement shows the power dissipation is 83 mW for the turbo decoding with six iterations at 3.1 Mb/s, and 25.1 mW for the Viterbi decoding at 1 Mb/s.

Multi-mode message passing switch networks applied for QC-LDPC decoder

The multi-mode message passing switch networks for multi-standard QC-LDPC decoder are presented. An enhanced self-routing switch network with only one barrel shifter permutation structure and a shifter-based two-way duplicated switch network are proposed to support 19 and 3 different sub-matrices defined in IEEE 802.16e and IEEE 802.11n. These proposed switch networks can route the decoding message in parallel by different sizes without signal congestion. The enhanced self-routing switch network can switch the messages at different expansion factors with the lowest hardware complexity. Under the condition of a smaller expansion factor, the decoder throughput can be enhanced from the two-way duplicated switch network by increasing the parallelism. In the 130 nm CMOS synthesis result, the proposed enhanced self-routing and the two-way duplicated switch network gate counts are 21.9 k and 37.4 k at 384 MHz operation frequency.

A 1.8V 250mW COFDM baseband receiver for DVB-T/H applications

A DVB-T/H baseband receiver with multi-stage power control, 2D linear channel equalizer, synchronizer, 2/4/8k-point FFT, and Viterbi/RS decoder is implemented in 0.18mum CMOS. At the highest data rate of 31.67Mb/s, it overcomes 70Hz Doppler frequency and consumes 250mW with a die size of 6.9 times 5.8mm2

A 952MS/s Max-Log MAP Decoder Chip using Radix-4 × 4 ACS Architecture

In this paper, a high-speed Max-Log MAP decoder is presented for soft-in and soft-out trellis decoding. The high throughput is achieved with a two-dimensional ACS design on the high-radix trellis structure, resulting in a highly parallel and area-efficient decoder. We further apply the retiming technique to reduce the critical path delay of ACS operation. After 0.13 mum CMOS chip implementation, the decoder occupies 1.96 mm2 area containing 220 K gates. The estimated timing under the 1.08 V supply and the worst case corner shows that the test chip can achieve the maximum 952 MS/s throughput. To our knowledge, the present Max-Log MAP decoder has the highest throughput with the modest hardware cost.