Ultra-Sparse Binary LDPC Codes with CSK Signals for Increased Data Rates in Future GNSS

The combination of multiple-input multiple-output (MIMO) and bit-interleaved coded modulation (BICM)/BICM with iterative demapping (BICM-ID) is one of the key technologies to meet the high-transmission-rate requirement of the next generation broadcasting systems. However, conventional low-density parity check (LDPC) coded MIMO BICM schemes always show poor performance with iterative demapping, and vice versa. In this paper, a subset of spatially coupled codes, finite-length spatially coupled (SC-) quasi-cyclic (QC-) LDPC code, is proposed and the universality of spatially coupled codes is utilized to achieve a good tradeoff between MIMO BICM and BICM-ID schemes. Due to the specific code structure of SC-QC-LDPC, the tool of multi-edge type density evolution (MET-DE) is employed for the performance analysis and code optimization. As an example, a finite-length SC-QC-LDPC code is optimized in binary-input additive white Gaussian noise channel, and then bit error rate simulations are carried out to verify the universality of the designed code in MIMO BICM and BICM-ID schemes.

This paper investigates an iterative multiuser detection for nonbinary low density parity check (LDPC) coded multicarrier multiple level frequency shift keying system to increase system performance under specific signal-to-noise ratio and data rate. We propose three-level hard-limited detection probabilities over both additive white Gaussian noise (AWGN) channels and Rayleigh fading channels. During multiuser detection (MUD) process, the hard-limited detection probabilities are computed in advanced and stored in tables. By using table looking up, the MUD soft outputs can be computed efficiently. We test the reliability of soft outputs from nonbinary LDPC channel decoder for all users. If the soft output exceeds a reliability threshold, the user is declared as a reliable user. For each symbol, we count the number of reliable users on it, and, use this information to update the soft output of MUD during the iterative multiuser detection and decoding process, which cancel multiple access interference iteratively. Numerical results show that the performances of three-level hard-limited systems outperform two-level hard-limited systems over AWGN channels and Rayleigh fading channels.

This paper presents a concept, “Cookie,” for a satellite particularly suited for dense spatial sampling by future Global Navigation Satellite Systems (GNSS) remote sensing constellations. Solely based on the reception of the direct and reflected signals transmitted by the GNSS, the satellite can provide observations of the Earth useful for a wide range of scientific and operational applications. The Cookie is capable of receiving direct and reflected signals, in both right- and left-hand circular polarizations, from any of the GNSS systems, and from virtually any arrival direction in both the upper and lower field-of-view hemispheres, i.e., providing nearly full 4π spherical coverage toward any navigation satellite not eclipsed by the Earth. The on-board remote sensing payload produces interferometric observables, e.g., the auto- and cross-correlation of several adequate combinations of the received signals. The interferometric processing is general, the same, and transparent, with respect to any of the signals transmitted by the current or planned GNSS systems. The instrument can implement any other suitable processing schemes too. Such payload can provide, in parallel, accurate GNSS Radio-Occultation (GNSS-RO) observations of the atmosphere and forward and backward GNSS Reflectometry (GNSS-R) measurements from the Earth surface. Several Cookies can be piled up inside the fairing of a rocket minimizing the launch cost of a constellation. A constellation of three Cookies has been simulated and its sampling performance characterized. The key concepts of the Cookie payload could be demonstrated through ESA's GNSS Reflectometry, Radio-Occultation, and Scatterometry experiment on board the International Space Station (GEROS-ISS).

Bit-interleaved coded modulation (BICM) transceivers often use equally spaced constellations and a random interleaver. In this paper, we propose a new BICM design, which considers hierarchical (nonequally spaced) constellations, a bit-level multiplexer, and multiple interleavers. It is shown that this new scheme increases the degrees of freedom that can be exploited in order to improve its performance. Analytical bounds on the bit error rate (BER) of the system in terms of the constellation parameters and the multiplexing rules are developed for the additive white Gaussian Noise (AWGN) and Nakagami-m fading channels. These bounds are then used to design the BICM transceiver. Numerical results show that, compared to conventional BICM designs, and for a target BER of 10^{-6}, gains up to 3 dB in the AWGN channel are obtained. For fading channels, the gains depend on the fading parameter, and reach 2 dB for a target BER of 10^{-7} and m=5.

This paper investigates linear precoding for bit-interleaved coded modulation (BICM) on additive white Gaussian noise (AWGN) channels. Concatenating a linear precoder as an inner encoder with an outer (convolutional) encoder produces a powerful code with a limited decoding complexity. Linear precoders are examined and optimized for two scenarios: using (i) a noniterative decoding strategy and (ii) an iterative decoding strategy under a perfect feedback assumption. The precoder design is based on an information-theoretical approach, on the one hand, and a pair-wise error probability (PEP) analysis, on the other hand. Both approaches render convenient precoder design rules. For a binary phase-shift keying (BPSK) signal set, the optimal precoders that result from these rules are also derived. Numerical results confirm the analytical findings and simulations illustrate the effectiveness of the approach.

The principle of coding in the signal space follows directly from Shannon’s analysis of waveform Gaussian channels subject to an input constraint. The early design of communication systems focused separately on modulation, namely signal design and detection, and error correcting codes, which deal with errors introduced at the demodulator of the underlying waveform channel. The correct perspective of signal-space coding, although never out of sight of information theorists, was brought back into the focus of coding theorists and system designers by Imai’s and Ungerböck’s pioneering works on coded modulation. More recently, powerful families of binary codes with a good tradeoff between performance and decoding complexity have been (re-)discovered. Bit-Interleaved Coded Modulation (BICM) is a pragmatic approach combining the best out of both worlds: it takes advantage of the signal-space coding perspective, whilst allowing for the use of powerful families of binary codes with virtually any modulation format. BICM avoids the need for the complicated and somewhat less flexible design typical of coded modulation. As a matter of fact, most of today’s systems that achieve high spectral efficiency such as DSL, Wireless LANs, WiMax and evolutions thereof, as well as systems based on low spectral efficiency orthogonal modulation, feature BICM, making BICM the de-facto general coding technique for waveform channels. The theoretical characterization of BICM is at the basis of efficient coding design techniques and also of improved BICM decoders, e.g., those based on the belief propagation iterative algorithm and approximations thereof. In this text, we review the theoretical foundations of BICM under the unified framework of error exponents for mismatched decoding. This framework allows an accurate analysis without any particular assumptions on the length of the interleaver or independence between the multiple bits in a symbol. We further consider the sensitivity of the BICM capacity with respect to the signal-to-noise ratio (SNR), and obtain a wideband regime (or low-SNR regime) characterization. We review efficient tools for the error probability analysis of BICM that go beyond the standard approach of considering infinite interleaving and take into consideration the dependency of the coded bit observations introduced by the modulation. We also present bounds that improve upon the union bound in the region beyond the cutoff rate, and are essential to characterize the performance of modern randomlike codes used in concatenation with BICM. Finally, we turn our attention to BICM with iterative decoding, we review extrinsic information transfer charts, the area theorem and code design via curve fitting. We conclude with an overview of some applications of BICM beyond the classical coherent Gaussian channel.

Experimental measurements have shown that the noise in many communication channels is non-Gaussian. Bit interleaved coded modulation (BICM) is very popular for spectrally efficient transmission. Recent results have shown that the performance of BICM using convolutional codes in non-fading channels can be significantly improved if the coded bits are not interleaved at all. This particular BICM design is called BICM trivial (BICM-T). In this paper, we analyze the performance of a generalized BICM-T design for communication over Gaussian mixture noise (GMN) channels. The results disclose that for an optimal bit error rate (BER) performance, the use of an interleaver in BICM for GMN channels depends upon the strength of the impulsive noise components in the Gaussian mixture. The results presented for 16-QAM show that the BICM-T can result in gains up to 1.5 dB for a target BER of 10 -6 if the impulsive noise in the Gaussian mixture is below a certain threshold level. The simulation results verify the tightness of developed union bound (UB) on BER performance.

Future Global Navigation Satellite Systems (GNSS) will significantly improve the performance of current navigation systems, providing new and enhanced capabilities. This will enable the implementation of innovative and advanced services and applications closer to the user's needs. In this framework, the road sector is one of the major potential markets for GNSS applications and, therefore, it is very promising for future EGNOS and GALILEO related applications. Satellite navigation receivers are now commonly installed in cars as a key tool for proving new services to people on the move such as electronic charging, real-time traffic information, emergency calls, route guidance, fleet management, or advance driving assistance systems. Specifically, a very important commercial opportunity is represented by the tolling-related applications. This paper describes the Vehicular Remote Tolling (VeRT) Project sponsored by Galileo Joint Undertaking (GJU) and performed in the frame of the first GJU Call under the EC VI Framework Programme. The overall design of the service provision architecture is also presented in this paper, together with the main topics related to the following activities focused on the service prototype demonstrator development.

It has been recognized that the risk from the vulnerability of GPS can lead to the extreme damage in the infrastructure of the civil and military in recent years. As an example, the intentional interference to GPS signal, named GPS jamming, was really performed to misguide GPS guided weapons during Iraq war in 2003, and the fact has also followed by the serious issues on GPS in civilian community. In the modernized military society, the navigation warfare(NAVWAR) based on the GPS jamming has been emerged and introduced as a military operation. The intentional interference to the future global navigation satellite system(GNSS) involving GPS must be also an important issue to civilian users in near future. This study is focused on the fundamental research prior to the research on "Potential principle of NAVWAR" under NAVWAR of the future warfare. In this paper, we would study on the investigation of NAVWAR based on electronic warfare(EW) and analyze characteristics of the jamming against GNSS's receivers. Then the general mechanism on GNSS jamming is proposed.

The European Union (EU), through the European Commission (EC), and the United States (US) have engaged in a dialogue on the possibility of developing the proposed future Global Navigation Satellite System (GNSS) known as Galileo in a manner that is at least compatible, if not fully interoperable, with the Global Positioning System (GPS). This paper discusses GPS and Galileo co-existence within a hierarchical framework ranging from simple compatibility (independent but non-interfering operation), to truly seamless global interoperability. Currently known system design parameters in the areas of timing, geodesy, and signal structure are addressed within this framework, and the US perspective on the importance of compatibility and interoperability between the two systems will be discussed.

Versions of this paper were first presented at the Royal Institute of Navigation GNSS Vulnerabilities and Solutions Conference held at Baska, Croatia in September 2008 and the Royal Institute of Navigation NAV 08 Conference held at Church House, Westminster, London in October 2008.The US Global Positioning System (GPS) is currently the primary source of Position, Navigation and Timing (PNT) information in maritime applications, whether stand-alone or augmented with additional systems. This situation will continue in the future with GPS, possibly together with other Global Navigation Satellite Systems (GNSS) e.g. Galileo, being the core PNT technology for e-Navigation – the future digital maritime architecture. GPS signals, measured at the surface on the Earth, are very weak. As such, the system is vulnerable to unintentional interference and jamming, resulting in possible denial of service over large geographical areas. The result of such interference could be the complete failure of the mariner's GPS receiver or, possibly worse, the presentation to the mariner of hazardously misleading information (HMI) for navigation and situational awareness, depending on how the GPS receiver reacts to the jamming incident. Recognising this, the General Lighthouse Authorities of the United Kingdom and Ireland (GLA), in collaboration with the UK Ministry of Defence (MOD) Defence Science and Technology Laboratory (DSTL), have conducted a series of sea-trials with the aim of identifying the full effects of GPS jamming on safe navigation at sea.This paper presents the key findings of these trials and provides important information on the effect of GPS denial. The GLA are playing a pivotal role in the establishment of eLoran as an independent source of PNT, taking advantage of eLoran's complementary nature, having dissimilar failure modes to GPS and the future GNSS. This paper provides information on the performance of an eLoran receiver in an area of GPS service denial. The paper presents the rationale for the work, details the system architecture employed, the data gathering efforts and finally the data analysis procedures, results and conclusions.

In a digital matched filter (DMF) the degradation of signal quality depends on the pre-sampling filter bandwidth and on the number of analogue to digital) converter (ADC) bits. Digital matched filters are used in the acquisition of Global navigation satellite systems (GNSS) signals. Automatic gain control (AGC) in the GNSS receivers is used to determine the maximum level of quantization by the ADC. In (Chang, 1982), the quantization degradation for different pre sampling bandwidths and adc bits is analysed in the presence of Additive Gaussian white noise (AGWN). Bandwidths of more than once (or twice) the data bit rate contribute only about 0.4 dB (or (0.2 dB) to the overall degradation of the DMF. Also 2 bit uniform step quantization with optimum ADC threshold setting is shown to recover most of the digital implementation degradation. In this paper by focusing on pre-sampling filter bandwidth equal to the data bit rate and 2 bit ADC, the effect of quantization on the received GNSS signal quality in the presence of continuous wave (CW) radio frequency interference (RFI) is analysed. It is shown that a one bit ADC can have much higher degradation than the 3.5 dB in the AGWN case. It is also shown that the effect of AGC on the quantization degradation has to do with both power and frequency of CW RFI. In the presence of CW RFI, the optimal value for ratio of maximum threshold of ADC to the effective noise RMS is shown to be about 1.35 which is higher than the case when RFI does not exist (0.8).

Coding Schemes for Energy Constrained IoT Devices

Low-density parity-check (LDPC) codes have been a focus in the research of error-correcting coding in recent years. Moreover, it may be desirable to combine these marvelous codes, which have exhibited an excellent performance, with spectral efficient modulations to improve the transmission capacity in bandwidth limited channels. In this paper we present a new coding and modulation scheme in this way, using LDPC codes, and in the bit-interleaved coded modulation (BICM) style. Several simulation results show that this scheme can provide a substantial coding gain both on Gaussian channels and Rayleigh channels.

In this paper a coded modulation method for the additive white Gaussian noise channel is presented which incorporates signal shaping. The scheme uses a modulation map to map bits to channel inputs. A modulation map is considered that has the advantage it is can easily be combined with binary error-correcting codes. The decoding strategy is a combination of bit-interleaved coded modulation and multistage decoding. The number of required decoding stages is only small compared to other multistage decoding schemes for coded modulation. It is shown that modulation maps can be designed with a constrained capacity limit very close to the capacity of the AWGN channel. When combined with low-density parity-check codes, simulation results show that a near-capacity performance is achieved for high spectral efficiencies.