Error Correction on an Insertion/Deletion Channel Applying Codes From RFID Standards

Abstract-This paper 1 investigates how to improve the performance of a passive RFID tag-to-reader communication channel with imperfect timing, by using codes mandated by international RFID standards. I. SHORTCUT This brief section is intended for those who want to skip the practical motivation and jump directly to the theoretical problem setting. Essentially, we have a binary channel which transmits information in terms of the length of runs of identical symbols. The valid runlengths are one or two, and if the receiver can determine exactly the time of each transition, she can also acquire the transmitted information sent. Due to a noisy process and with probability p, a given length-one run is detected as a length-two run, in which case a symbol has been inserted. Vice versa, with probability p, a given lengthtwo run is detected as a length-one run, in which case a symbol has been deleted. Thus, this is a special case of an insertion/deletion channel. The uncoded information is totally vulnerable to the noise of this channel. In order to protect the information, an error correction code is applied. In this paper, the error correcting code is actually a CRC-CCITT code, mandated by many international standard protocols (but intended for error detection). Now, if you also know about cyclic redundancy check (CRC) codes, you can go to Section VI if you want to skip the introduction. II. INTRODUCTION Inductive coupling is a technique by which energy from one circuit is transferred to another without wires. This is a fundamental technology for near-field passive radio frequency identification (RFID) applications as well as lightweight sensor applications. In the passive RFID application, a reader, containing or attached to a power source, controls and powers a communication session with a tag; a device without a separate power source. The purpose of the communication session may be, for examples, object identification, access control, or acquisition of sensor data. The operating range of a reader-tag pair is determined by communications requirements as well as by power transfer requirements. To meet the communications requirements, the reader-to-tag and the tag-to-reader communication channels satisfy specified demands on communication transfer rate and reliability. To meet the power transfer requirements, the received power at the tag must be sufficiently large as to provide operating power at the tag. In [1], a discretized Gaussian shift channel is proposed as a modified bit-shift channel to model synchronization loss. In this paper, we will apply the same model to the tag-toreader channel. In terms of coding, the practical difference is that the tag-to-reader channel allows more elaborate decoding schemes, especially since the volume of data transmitted and the transmission rates are modest. We will investigate the performance of Manchester coding, which is a standardized modulation technique for RFID applications. As a stand-alone code this code was studied i

Polar Codes are Optimal for Lossy Source Coding

We consider lossy source compression of a binary symmetric source using polar codes and the low-complexity successive encoding algorithm. It was recently shown by Arikan that polar codes achieve the capacity of arbitrary symmetric binary-input discrete memoryless channels under a successive decoding strategy. We show the equivalent result for lossy source compression, i.e., we show that this combination achieves the rate-distortion bound for a binary symmetric source. We further show the optimality of polar codes for various problems including the binary Wyner-Ziv and the binary Gelfand-Pinsker problemComment: 15 pages, submitted to Transactions on Information Theor

Soft information based protocols in network coded relay networks

Future wireless networks aim at providing higher quality of service (QoS) to mobile users. The emergence of relay technologies has shed light on new methodologies through which the system capacity can be dramatically increased with low deployment cost. In this thesis, novel relay technologies have been proposed in two practical scenarios: wireless sensor networks (WSN) and cellular networks. In practical WSN designs, energy conservation is the single most important requirement. This thesis draws attention to a multiple access relay channels model in the WSN. The network coded symbol for the received signals from correlated sources has been derived; the network coded symbol vector is then converted into a sparse vector, after which a compressive sensing (CS) technique is applied over the sparse signals. A theoretical proof analysis is derived regarding the reliability of the network coded symbol formed in the proposed protocol. The proposed protocol results in a better bit error rate (BER) performance in comparison to the direct implementation of CS on the EF protocol. Simulation results validate our analyses. Another hot topic is the application of relay technologies to the cellular networks. In this thesis, a practical two-way transmission scheme is proposed based on the EF protocol and the network coding technique. A trellis coded quantization/modulation (TCQ/M) scheme is used in the network coding process. The soft network coded symbols are quantized into only one bit thus requiring the same transmission bandwidth as the simplest decode-and-forward protocol. The probability density function of the network coded symbol is derived to help to form the quantization codebook for the TCQ. Simulations show that the proposed soft forwarding protocol can achieve full diversity with only a transmission rate of 1, and its BER performance is equivalent to that of an unquantized EF protocol

Soft information based protocols in network coded relay networks

Future wireless networks aim at providing higher quality of service (QoS) to mobile users. The emergence of relay technologies has shed light on new methodologies through which the system capacity can be dramatically increased with low deployment cost. In this thesis, novel relay technologies have been proposed in two practical scenarios: wireless sensor networks (WSN) and cellular networks. In practical WSN designs, energy conservation is the single most important requirement. This thesis draws attention to a multiple access relay channels model in the WSN. The network coded symbol for the received signals from correlated sources has been derived; the network coded symbol vector is then converted into a sparse vector, after which a compressive sensing (CS) technique is applied over the sparse signals. A theoretical proof analysis is derived regarding the reliability of the network coded symbol formed in the proposed protocol. The proposed protocol results in a better bit error rate (BER) performance in comparison to the direct implementation of CS on the EF protocol. Simulation results validate our analyses. Another hot topic is the application of relay technologies to the cellular networks. In this thesis, a practical two-way transmission scheme is proposed based on the EF protocol and the network coding technique. A trellis coded quantization/modulation (TCQ/M) scheme is used in the network coding process. The soft network coded symbols are quantized into only one bit thus requiring the same transmission bandwidth as the simplest decode-and-forward protocol. The probability density function of the network coded symbol is derived to help to form the quantization codebook for the TCQ. Simulations show that the proposed soft forwarding protocol can achieve full diversity with only a transmission rate of 1, and its BER performance is equivalent to that of an unquantized EF protocol