Joint protocol-channel decoding for robust frame synchronization (original) (raw)

Sliding-Trellis Based Frame Synchronization

2011 IEEE International Conference on Communications (ICC), 2011

Frame Synchronization (FS) is required in several communication standards in order to recover the individual frames that have been aggregated in a burst. This paper proposes a low-delay and reducedcomplexity Sliding Trellis (ST)-based FS technique, compared to our previously proposed trellis-based FS method. Each burst is divided into overlapping windows in which FS is performed. Useful information is propagated from one window to the next. The proposed method makes use of soft information provided by the channel, but also of all sources of redundancy present in the protocol stack. An illustration of our STbased approach for the WiMAX Media Access Control (MAC) layer is provided. When FS is performed on bursts transmitted over Rayleigh fading channel, the ST-based approach reduces the FS latency and complexity at the cost of a very small performance degradation compared to our full complexity trellis-based FS and outperforms state-of-the-art FS techniques.

Cross-layer frame synchronization for H.264 video over WIMAX

2010

In the WIMAX (802.16e) standard several small medium access control (MAC) packets may be aggregated to form a MAC burst, forwarded to the physical (PHY) layer [1] The burst transmission is a mechanism to allow multiple MAC protocol data units (PDUs) belonging to the same video channel to be transmitted / received in an aggregated way, in order to enable power saving at the mobile station, by putting the transceiver in sleep mode during off-burst interval. As a consequence of it, at the receiver side individual packets should be isolated within a burst, i.e. frame synchronization should be performed. We propose here to forward soft values from the PHY to the MAC layer, and to use our previous results on frame synchronization based on soft values [2] [3]. In addition, we exploit here a-priori information on the prevalence of 1's or 0's in the video bitstream and in packet headers, by performing application-aware and channel-aware MAC layer frame synchronization. Results show that the proposed approach results in an evident gain, at the expense of a small additional complexity.

Frame Synchronization for Variable-Length Packets

IEEE Journal on Selected Areas in Communications, 2008

A cognitive radio can sense its environment and adapt some of its features, such as carrier frequency, transmission bandwidth, transmission power, and modulation, thus allowing dynamic reuse of the available spectrum. Due to their high degree of adaptability to environmental variations, cognitive radios are expected to utilize packet-based transmission with variablelength frames. Packet-based transmission requires the receiver to perform frame synchronization, an important enabling step that allows adaptation in cognitive radios. However, proper metrics to characterize the performance of frame synchronization for transmission of variable-length frames are currently unavailable. To address this issue, we put forth two performance metrics, namely the expected duration to complete frame synchronization and the probability of correct acquisition within a given duration. We then develop analytical expressions for these important metrics. This paper advances our understanding of frame synchronization for the continuous transmission of variable-length frames and for bursty transmission.

Decoder Assisted Channel Estimation and Frame Synchronization

2001

In regards to turbo codes, to the author's knowledge, previous literature has treated decoder assisted frame synchronization and channel estimation as separate processes. Here a joint decoder assisted process of channel estimation and frame synchronization is proposed. In brief, the method entails using a sync word (SW) embedded mid-packet for both channel estimation and frame synchronization. The method will use a correlation-based frame synchronization that passes a list of possible delays to the turbo decoder. The turbo decoder will draw upon pilot symbol assisted modulation (PSAM) techniques for channel estimation using the coded SW.

Protocol-Assisted Channel Decoding

IEEE Signal Processing Letters, 2000

This paper describes how the channel decoder at Physical layer of a communication system can benefit from information brought either by careful examination of the standard, or by already received packets. In other words, the improvement exploits the cross-layer information redundancy and successive frame correlation in the wireless communication. It is shown that a suboptimal estimator, making use of explicitly known bits as pilot bits in the channel decoder may provide noticeable gains in terms of frame error rate. Our method is simulated on 802.11a radio interface using BPSK modulation over AWGN channel. The performance on robust recovery of PHY and MAC headers shows a substantial link budget improvement without modifying the standard, while introducing an additional interleaver also allows a significant improvement in terms of frame error rate.

Optimal Sequential Frame Synchronization for Fading Channel

2015

In [1], Chandar et al studied a problem of sequential frame synchronization for a frame transmitted randomly and Uniformly in an interval of size A slots. For a discrete memoryless channel, they showed that the frame length N must scale as e > A for the frame detection error to go to zero (asymptotically with A). α(Q) is defined as the synchronization threshold for the discrete memory-less channel and depends on the channel transition probabilities Q. In our paper, we study the sequential frame synchronization problem for a fading channel and additive noise and seek to characterize the effect of fading. For a discrete ON-OFF fading channel (with ON probability p) and additive noise (with channel transition probabilities Qn), we characterise the synchronisation threshold of the composite channel α(Q) and show that α(Q) ≤ α(Qn)× p. We then characterize the synchronization threshold for Rayleigh fading and AWGN channel as a function of the fading and noise parameters. The asynchrono...

Joint Frame Synchronization and Channel Estimation: Sparse Recovery Approach and USRP Implementation

IEEE Access

Correlation-based techniques used for frame synchronization can suffer significant performance degradation over multi-path frequency-selective channels. In this paper, we propose a joint frame synchronization and channel estimation (JFSCE) framework as a remedy to this problem. This framework, however, increases the size of the resulting combined channel vector which should capture both the channel impulse response (CIR) vector and the frame boundary offset and, therefore, its estimation becomes more challenging. On the other hand, because the combined channel vector is sparse, sparse channel estimation methods can be applied. We propose several JFSCE methods using popular sparse signal recovery (SSR) algorithms which exploit the sparsity of the combined channel vector. Subsequently, the sparse channel vector estimate is used to design a sparse equalizer. Our simulation results and experimental measurements using software defined radios (SDRs) show that in some scenarios our proposed method improves the overall system performance significantly, in terms of the mean square error (MSE) between the transmitted and the equalized symbols compared to the conventional method.

On sequential frame synchronization in AWGN channels

IEEE Transactions on Communications, 2006

We present a framework for the analysis of frame synchronization based on synchronization words (SWs), where the detection is based on the following sequential algorithm. The received samples are observed over a window of length equal to the SW; over this window, a metric (e.g., correlation) is computed; an SW is declared if the computed metric is greater than a proper threshold, otherwise the observation window is time-shifted one sample. We assume a Gaussian channel, antipodal signaling, equally distributed data symbols, and coherent detection, where soft values are provided to the frame synchronizer. We state the problem starting from the hypothesis testing theory, deriving the optimum metric [optimum likelihood ratio test (LRT)] according to the Neyman-Pearson lemma. When the data distribution is unknown, we design a simple and effective test based on the generalized LRT (GLRT). We also analyze the performance of the commonly used correlation metric, both with "hard" and "soft" values at the synchronizer input. We show that synchronization can be greatly improved by using the LRT and GLRT metrics instead of correlation and that, among correlation-based tests, sometimes hard correlation is better than soft correlation. The obtained closed-form expressions allow the derivation of the receiver operating characteristic (ROC) curves for the LRT and GLRT synchronizers, showing a remarkable gain with respect to synchronization based on correlation metric.

Novel frame synchronization for WiMAX OFDM systems

2010

Frame synchronization is a critical factor for effective operation of Orthogonal Frequency Division Multiplexing (OFDM) schemes. This paper studies the frame synchronization of OFDM based wireless systems and proposes a new method for IEEE 802.16 (WiMAX) to improve its performance. The preamble, which is used in this method, is consists of two identical halves, and our method uses the correlation between these two parts in a new efficient form. Our metric calculates the start point within two levels. It finds some possible points as start point in the first level and removes the irrelevant candidates at the second level. The performance of proposed metric and existing ones is compared in terms of mean square error (MSE) and probability of correct detection in AWGN and multipath fading channels. Simulation results show that the proposed method has better performances than famous methods, which were proposed by Schmidl, Minn, Park, Kim, Meng, and in both AWGN and multipath fading Rayleigh channels. Also, compared to new methods with more accurate performance, proposed method has egual performance with less complexity.

Frame Synchronization based on robust header recovery and Bayesian testing

Personal Indoor and Mobile Radio …

Abstract—Video transmission on wireless links usually requires some frame aggregation, so that the overhead due to the headers is not a too large percentage of the bit-stream. In such a situation, header error detection is essential, because any error in the header may cause ...