Duobinary signaling has been introduced into asymmetric multi-chip communications such as DRAM or display interfaces, which allows a controlled amount of ISI to reduce signaling bandwidth by 2/3. A × 2 oversampled equalization has been developed to realize Duobinary signaling. Symbol-rate clock recovery form Duobinary signal has been developed to reduce power consumption for receivers. A Duobinary transmitter test chip was fabricated with 90-nm CMOS process. A 3.5 dB increase in eye height and a 1.5 times increase in eye width was observed.

This paper proposes a modified per-survivor iterative timing recovery scheme, which exploits a new split-preamble strategy in conjunction with a per-survivor processing soft-output Viterbi algorithm (PSP-SOVA). The conventional split-preamble strategy places a preamble at the beginning of a data sector and uses it to run a phase-locked loop during acquisition to find an initial phase/frequency offset. However, the proposed scheme splits the preamble into two parts. The first part is placed at the beginning of the data sector, whereas the second part is divided into small clusters, each of which is then embedded uniformly within the data stream. This split preamble is utilized to adjust the branch metric calculation in PSP-SOVA to ensure that the survivor path occurs in a correct direction. Results indicate that the proposed scheme yields a better performance than a conventional receiver with separate timing recovery and turbo equalization, and the iterative timing recovery scheme proposed in [1],[2], especially when the timing jitter is large. In addition, we also show that the proposed scheme can automatically correct a cycle slip much more efficiently than the others.

Field programmable gate arrays (FPGAs) are widely used in reliability-critical systems due to their reconfiguration ability. However, with the shrinking device feature size and increasing die area, nowadays FPGAs can be deeply affected by the errors induced by electromigration and radiation. To improve the reliability of FPGA-based reconfigurable systems, a permanent fault recovery approach using a domain partition model is proposed in this paper. In the proposed approach, the fault-tolerant FPGA recovery from faults is realized by reloading a proper configuration from a pool of multiple alternative configurations with overlaps. The overlaps are presented as a set of vectors in the domain partition model. To enhance the reliability, a technical procedure is also presented in which the set of vectors are heuristically filtered so that the corresponding small overlaps can be merged into big ones. Experimental results are provided to demonstrate the effectiveness of the proposed approach through applying it to several benchmark circuits. Compared with previous approaches, the proposed approach increased MTTF by up to 18.87%.

Reliable data transmission is desirable in wireless sensor networks due to the high packet loss rate during multi-hop transmissions. To reliably transmit data for event-driven applications, packet loss recovery mechanism is needed. For loss recovery, sensor nodes need to keep packets in their buffers until transmissions successfully complete. However, since sensor nodes have limited memory, packets cannot be buffered for a long period of time. This letter proposes an efficient buffer management technique that caches data packets for appropriate amount of time to minimize the resource requirements and at the same time provide reliable data transmission among sensor nodes.

In this paper, a novel approach to speech reinforcement in a low-bit-rate speech coder under ambient noise environments is proposed. The excitation vector of ambient noise is efficiently obtained at the near-end and then combined with the excitation signal of the far-end for a suitable reinforcement gain within the G.729 CS-ACELP Annex. B framework. For this reason, this can be clearly different from previous approaches in that the present approach does not require an additional arithmetic step such as the discrete Fourier transform (DFT). Experimental results indicate that the proposed method shows better performance than or at least comparable to conventional approaches with a lower computational burden.

At some point in a digital communications receiver, the received analog signal must be sampled. Good performance requires that these samples be taken at the right times. The process of synchronizing the sampler with the received analog waveform is known as timing recovery. Conventional timing recovery techniques perform well only when operating at high signal-to-noise ratio (SNR). Nonetheless, iterative error-control codes allow reliable communication at very low SNR, where conventional techniques fail. This paper provides a detailed review on the timing recovery strategies based on per-survivor processing (PSP) that are capable of working at low SNR. We also investigate their performance in magnetic recording systems because magnetic recording is a primary method of storage for a variety of applications, including desktop, mobile, and server systems. Results indicate that the timing recovery strategies based on PSP perform better than the conventional ones and are thus worth being employed in magnetic recording systems.

In key-recovery methods using smart cards, a user can recover the disk encryption key in cooperation with the system administrator, even if the user has lost the smart card including the disk encryption key. However, the disk encryption key is known to the system administrator in advance in most key-recovery methods. Hence user's disk data may be read by the system administrator. Furthermore, if the disk encryption key is not known to the system administrator in advance, it is difficult to achieve a key authentication. In this paper, we propose a scheme which enables to recover the disk encryption key when the user's smart card is lost. In our scheme, the disk encryption key is not preserved anywhere and then the system administrator cannot know the key before key-recovery phase. Only someone who has a user's smart card and knows the user's password can decrypt that user's disk data. Furthermore, we measured the processing time required for user authentication in an experimental environment using a virtual machine monitor. As a result, we found that this processing time is short enough to be practical.

This paper describes a channel-adaptive packet scheduler for improved error control performance in a peer-cooperative distributed media streaming system. The proposed packet-scheduling algorithm was designed for the case in which streaming server peers rely on an error-recovery strategy using retransmission and application-layer automatic repeat request rather than error protection using forward error correction. The proposed scheduler can maximize retransmission opportunities and reduce the frame loss rate by using the observed channel status from each server peer. Simulation results show that the proposed algorithm enhances error-recovery performance in distributed multimedia streaming better than other schedulers.

In this paper, we present practical password recovery attacks against two challenge and response authentication protocols using MD4. For attacks on protocols, the number of queries is one of the most important factors because the opportunity where an attacker can ask queries is very limited in real protocols. When responses are computed as MD4(Password||Challenge), which is called prefix approach, previous work needs to ask 237 queries to recover a password. Asking 237 queries in real protocols is almost impossible. In our attack, to recover up to 8-octet passwords, we only need 1 time the amount of eavesdropping, 17 queries, and 234 MD4 off-line computations. To recover up to 12-octet passwords, we only need 210 times the amount of eavesdropping, 210 queries, and 241 off-line MD4 computations. When responses are computed as MD4(Password||Challenge||Password), which is called hybrid approach, previous work needs to ask 263 queries, while in our attack, up to 8-octet passwords are practically recovered by 28 times the amount of eavesdropping, 28 queries, and 239 off-line MD4 computations. Our idea is guessing a part of passwords so that we can simulate values of intermediate chaining variables from observed hash values. This enables us to use a short local collision that occurs with a very high probability, and thus the number of queries becomes practical.

Since the compressed data, which are frequently used in computer systems and communication systems, are very sensitive to errors, several error recovery methods for data compression have been proposed. Error recovery method for LZ77 coding, one of the most popular universal data compression methods, has been proposed. This cannot be applied to LZSS coding, a variation of LZ77 coding, because its compressed data consist of variable-length codewords. This paper proposes a burst error recovery method for LZSS coding. The error sensitive part of the compressed data are encoded by unary coding and moved to the beginning of the compressed data. After these data, a synchronization sequence is inserted. By searching the synchronization sequence, errors in the error sensitive part are detected. The errors are recovered by using a copy of the part. Computer simulation says that the compression ratio of the proposed method is almost equal to that of LZ77 coding and that it has very high error recovery capability.

Traditional TCP has a good congestion control strategy that adapts its sending rate in accordance with network congestion. In addition, a fast recovery algorithm can help TCP achieve better throughput by responding to temporary network congestion well. However, if multiple packet losses occur, the time to enter congestion avoidance phase would be delayed due to the long recovery time. Moreover, during the recovery phase, TCP freezes congestion window size until all lost packets are recovered, and this can make recovery time much longer resulting in performance degradation. To mitigate such recovery overhead, we propose Momentary recovery algorithm that recovers packet loss without an extra recovery phase. As other TCP and variants, our algorithm also halves the congestion window size when packet drop is detected, but it performs congestion avoidance phase immediately as if loss recovery is completed. For lost packets, TCP sender transmits them along with normal packets as long as congestion window permits rather than performs fast retransmission. In this manner, we can eliminate recovery overhead efficiently and reach steady state momentarily after network congestion. Finally, we provide a simulation based study on TCP recovery behaviors and confirm that our Momentary recovery algorithm always shows better performance compared with NewReno, SACK, and FACK.

Motivated by different error characteristics of each path, we propose a study-based error recovery scheme for Networks-on-Chip (NoC). In this scheme, two study processes are executed respectively to obtain the characteristics of the errors in every link first; and then, according to the study results and the selection rule inferred by us, this scheme selects a better error recovery scheme for every path. Simulation results show that compared with traditional simple retransmission scheme and hybrid single-error-correction, multi-error-retransmission scheme, this scheme greatly improves the throughput and cuts down the energy consumption with little area increase.

This letter proposes a new retransmission persistence management scheme for selective repeat automatic repeat request (SR-ARQ). By considering the overall traffic load that has to be managed by SR-ARQ, the proposed scheme arbitrates the retransmission persistence to prevent an abrupt delay increment due to excessive link-level local retransmissions. OPNET simulations show that SR-ARQ performs better with the proposed scheme than with a fixed value of retransmission persistence in terms of the throughput of transmission control protocol (TCP).

We propose a novel adaptive segment repair mechanism to improve traditional MPLS (Multi-Protocol Label Switching) failure recovery. The proposed mechanism protects one or more contiguous high failure probability links by dynamic setup of segment protection. Simulations demonstrate that the proposed mechanism reduces failure recovery time while also increasing network resource utilization.

In this letter, we propose a speech reinforcement technique based on soft decision under both the far-end and near-end noise environments. We amplify the estimated clean speech signal at the far-end based on the estimated ambient noise spectrum at the near-end, as opposed to reinforcing the noisy far-end speech signal, so that it can be heard more intelligibly in far-end noisy environments. To obtain an effective reinforcement technique, we adopt the soft decision scheme incorporating a speech absence probability (SAP) in the frequency dependent signal-to-noise ratio (SNR) recovery method where the clean speech spectrum is estimated and the reinforcement gain is inherently derived and modified within the unified framework. Performance of the proposed method is evaluated by a subjective testing under various noisy environments. This is an improvement over previous approaches.

A hidden Markov model (HMM)-based parameter estimation scheme is proposed for wideband speech recovery. In each Markov state, the estimation efficiency is improved using a new mapping function derived from the weighted least squares of vector deviations. The experimental results reveal that the performance of the proposed scheme is superior to that combining the HMM and Gaussian mixture model (GMM).

A novel DC-to-960 MHz impulse radio ultra-wideband (IR-UWB) transceiver based on threshold detection technique is developed. It features a digital pulse-shaping transmitter, a DC power-free pulse discriminator and an error-recovery phase-frequency detector. The developed transceiver in 90 nm CMOS achieves the lowest energy consumption of 2.2 pJ/bit transmitter and 1.9 pJ/bit receiver at 100 Mbps in the UWB transceivers.

We present a recovery scheme based on Self-protected Spanning Tree (SST), which recovers from failure all by itself. In the recovery scheme, the links are assigned birthdays to denote the order in which they are to be considered for adding to the SST. The recovery mechanism, named Birthday-based Link Replacing Mechanism (BLRM), is able to transform a SST into a new spanning tree by replacing some tree links with some non-tree links of the same birthday, which ensures the network connectivity after any single link or node failure. First, we theoretically prove that the SST-based recovery scheme can be applied to arbitrary two-edge connected or two connected networks. Then, the recovery time of BLRM is analyzed and evaluated using Ethernet, and the simulation results demonstrate the effectiveness of BLRM in achieving fast recovery. Also, we point out that BLRM provides a novel load balancing mechanism by fast changing the topology of the SST.

We propose a stereo transmission technique using infrared rays and pulse density modulation (PDM) for digital wireless audio headphone systems. The main feature of the proposed technique is the use of two channels for transmission: the PDM data channel and the synchronized clock channel. This technique improves receiver characteristics to a noise floor of -80 dB and a second distortion of 62 dB and achieves a very low power consumption of 3.5 mW.

In this paper, we propose an effective key recovery attack on stream ciphers Py and Pypy with chosen IVs. Our method uses an internal-state correlation based on the vulnerability that the randomization of the internal state in the KSA is inadequate, and it improves two previous attacks proposed by Wu and Preneel (a WP-1 attack and a WP-2 attack). For a 128-bit key and a 128-bit IV, the WP-1 attack can recover a key with 223 chosen IVs and time complexity 272. First, we improve the WP-1 attack by using the internal-state correlation (called a P-1 attack). For a 128-bit key and a 128-bit IV, the P-1 attack can recover a key with 223 chosen IVs and time complexity 248, which is 1/224 of that of the WP-1 attack. The WP-2 attack is another improvement on the WP-1 attack, and it has been known as the best previous attack against Py and Pypy. For a 128-bit key and a 128-bit IV, the WP-2 attack can recover a key with 223 chosen IVs and time complexity 224. Second, we improve the WP-2 attack by using the internal-state correlation as well as the P-1 attack (called a P-2 attack). For a 128-bit key and a 128-bit IV, the P-2 attack can recover a key with 223 chosen IVs and time complexity 224, which is the same capability as that of the WP-2 attack. However, when the IV size is from 64 bits to 120 bits, the P-2 attack is more effective than the WP-2 attack. Thus, the P-2 attack is the known best attack against Py and Pypy.