A hardware spinal decoder

Spinal codes are a recently proposed capacity-achieving rateless code. While hardware encoding of spinal codes is straightforward, the design of an efficient, high-speed hardware decoder poses significant challenges. We present the first such decoder. By relaxing data dependencies inherent in the classic M-algorithm decoder, we obtain area and throughput competitive with 3GPP turbo codes as well as greatly reduced latency and complexity. The enabling architectural feature is a novel alpha-beta incremental approximate selection algorithm. We also present a method for obtaining hints which anticipate successful or failed decoding, permitting early termination and/or feedback-driven adaptation of the decoding parameters. We have validated our implementation in FPGA with on-air testing. Provisional hardware synthesis suggests that a near-capacity implementation of spinal codes can achieve a throughput of 12.5 Mbps in a 65 nm technology while using substantially less area than competitive 3GPP turbo code implementations.Irwin Mark Jacobs and Joan Klein Jacobs Presidential FellowshipIntel Corporation (Fellowship)Claude E. Shannon Research Assistantshi

Short Block-length Codes for Ultra-Reliable Low-Latency Communications

This paper reviews the state of the art channel coding techniques for ultra-reliable low latency communication (URLLC). The stringent requirements of URLLC services, such as ultra-high reliability and low latency, have made it the most challenging feature of the fifth generation (5G) mobile systems. The problem is even more challenging for the services beyond the 5G promise, such as tele-surgery and factory automation, which require latencies less than 1ms and failure rate as low as $10^{-9}$. The very low latency requirements of URLLC do not allow traditional approaches such as re-transmission to be used to increase the reliability. On the other hand, to guarantee the delay requirements, the block length needs to be small, so conventional channel codes, originally designed and optimised for moderate-to-long block-lengths, show notable deficiencies for short blocks. This paper provides an overview on channel coding techniques for short block lengths and compares them in terms of performance and complexity. Several important research directions are identified and discussed in more detail with several possible solutions.Comment: Accepted for publication in IEEE Communications Magazin

Integrating spinal codes into wireless systems

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (p. 85-88).Rateless spinal codes [47] promise performance gains for future wireless systems. These gains can be realized in the form of higher data rates, longer operational ranges, reduced power consumption, and greater reliability. This is due in part to the manner in which rateless codes exploit the instantaneous characteristics of the wireless medium, including unpredictable fluctuations. By contrast, traditional rated codes can accommodate variability only by making overly conservative assumptions. Before spinal codes reach practical deployment, they must be integrated into the networking stacks of real devices, and they must be instantiated in compact, ecient silicon. This thesis addresses fundamental challenges in each of these two areas, covering a body of work reported in previous publications by this author and others [27, 26]. On the networking side, this thesis explores a rateless analogue of link-layer retransmission schemes, capturing the idea of rate adaptation and generalizing the approach of hybrid ARQ/incremental redundancy systems such as LTE [29]. On the silicon side, this thesis presents the development of a VLSI architecture that exploits the inherent parallelism of the spinal decoder.by Peter Anthony Iannucci.S.M

A New Class of Multiple-rate Codes Based on Block Markov Superposition Transmission

Hadamard transform~(HT) as over the binary field provides a natural way to implement multiple-rate codes~(referred to as {\em HT-coset codes}), where the code length $N=2^p$ is fixed but the code dimension $K$ can be varied from $1$ to $N-1$ by adjusting the set of frozen bits. The HT-coset codes, including Reed-Muller~(RM) codes and polar codes as typical examples, can share a pair of encoder and decoder with implementation complexity of order $O(N \log N)$. However, to guarantee that all codes with designated rates perform well, HT-coset coding usually requires a sufficiently large code length, which in turn causes difficulties in the determination of which bits are better for being frozen. In this paper, we propose to transmit short HT-coset codes in the so-called block Markov superposition transmission~(BMST) manner. At the transmitter, signals are spatially coupled via superposition, resulting in long codes. At the receiver, these coupled signals are recovered by a sliding-window iterative soft successive cancellation decoding algorithm. Most importantly, the performance around or below the bit-error-rate~(BER) of $10^{-5}$ can be predicted by a simple genie-aided lower bound. Both these bounds and simulation results show that the BMST of short HT-coset codes performs well~(within one dB away from the corresponding Shannon limits) in a wide range of code rates

On feedback-based rateless codes for data collection in vehicular networks

The ability to transfer data reliably and with low delay over an unreliable service is intrinsic to a number of emerging technologies, including digital video broadcasting, over-the-air software updates, public/private cloud storage, and, recently, wireless vehicular networks. In particular, modern vehicles incorporate tens of sensors to provide vital sensor information to electronic control units (ECUs). In the current architecture, vehicle sensors are connected to ECUs via physical wires, which increase the cost, weight and maintenance effort of the car, especially as the number of electronic components keeps increasing. To mitigate the issues with physical wires, wireless sensor networks (WSN) have been contemplated for replacing the current wires with wireless links, making modern cars cheaper, lighter, and more efficient. However, the ability to reliably communicate with the ECUs is complicated by the dynamic channel properties that the car experiences as it travels through areas with different radio interference patterns, such as urban versus highway driving, or even different road quality, which may physically perturb the wireless sensors. This thesis develops a suite of reliable and efficient communication schemes built upon feedback-based rateless codes, and with a target application of vehicular networks. In particular, we first investigate the feasibility of multi-hop networking for intra-car WSN, and illustrate the potential gains of using the Collection Tree Protocol (CTP), the current state of the art in multi-hop data aggregation. Our results demonstrate, for example, that the packet delivery rate of a node using a single-hop topology protocol can be below 80% in practical scenarios, whereas CTP improves reliability performance beyond 95% across all nodes while simultaneously reducing radio energy consumption. Next, in order to migrate from a wired intra-car network to a wireless system, we consider an intermediate step to deploy a hybrid communication structure, wherein wired and wireless networks coexist. Towards this goal, we design a hybrid link scheduling algorithm that guarantees reliability and robustness under harsh vehicular environments. We further enhance the hybrid link scheduler with the rateless codes such that information leakage to an eavesdropper is almost zero for finite block lengths. In addition to reliability, one key requirement for coded communication schemes is to achieve a fast decoding rate. This feature is vital in a wide spectrum of communication systems, including multimedia and streaming applications (possibly inside vehicles) with real-time playback requirements, and delay-sensitive services, where the receiver needs to recover some data symbols before the recovery of entire frame. To address this issue, we develop feedback-based rateless codes with dynamically-adjusted nonuniform symbol selection distributions. Our simulation results, backed by analysis, show that feedback information paired with a nonuniform distribution significantly improves the decoding rate compared with the state of the art algorithms. We further demonstrate that amount of feedback sent can be tuned to the specific transmission properties of a given feedback channel

An Investigation of Decoding Complexity and Coding Rate Performance of Raptor Codes

This thesis examines two aspects of wireless transmissions using Raptor codes: (i) decoding complexity and (ii) rate performance. First, observing that the high complexity of Raptor decoding process is mainly due to the required number of decoding attempts, a strategy is proposed to reduce the decoding complexity by choosing an appropriate time to start the first decoding attempt and thus keeping a small number of decoding attempts. Simulations results show that the proposed strategy, when combined with a decoding algorithm, can achieve a significant reduction in Raptor decoding complexity. Another threshold strategy is also investigated, aiming to further reduce the decoding complexity by providing only "reliable" bits for Raptor decoding process. The effect of this considered strategy can be interpreted as simulating a better transmission channel and techniques to estimate its effective channel quality improvement are developed and evaluated. Second, the Raptor coding rate performance over Nakagami-m fading channels and in a cooperative relaying network using Binary Phase Shift Keying (BPSK) is studied. The simulation results show that the Raptor-coded BPSK scheme can provide a transmission rate closely approaching the channel capacity for different fading conditions at low SNR. For cooperative relaying network using Raptor-coded BPSK scheme, two cooperative protocols are considered: the existing Time Division (TD) and the modified Phase-2 Simultaneous Transmission (PST). Their performance is investigated in terms of average time and energy required for a successful transmission under various conditions of the Relay-Destination (RD) link. The simulation results show that the PST protocol often outperforms the TD protocol in terms of average transmission time and the TD protocol only has lower average transmission energy when the RD link's quality is better that of the Source-Destination (SD) link

Network streaming and compression for mixed reality tele-immersion

Bulterman, D.C.A. [Promotor]Cesar, P.S. [Copromotor

Sequence codes

Véase documento adjunt