It is shown that, particularly for terrestrial cellular telephony, the interference-suppression feature of CDMA (code division multiple access) can result in a many-fold increase in capacity over analog and even over competing digital techniques. A single-cell system, such as a hubbed satellite network, is addressed, and the basic expression for capacity is developed. The corresponding expressions for a multiple-cell system are derived. and the distribution on the number of users supportable per cell is determined. It is concluded that properly augmented and power-controlled multiple-cell CDMA promises a quantum increase in current cellular capacity. >

On the capacity of a cellular CDMA system

IoT security: Review, blockchain solutions, and open challenges

Location-aware technologies will revolutionize many aspects of commercial, public service, and military sectors, and are expected to spawn numerous unforeseen applications. A new era of highly accurate ubiquitous location-awareness is on the horizon, enabled by a paradigm of cooperation between nodes. In this paper, we give an overview of cooperative localization approaches and apply them to ultrawide bandwidth (UWB) wireless networks. UWB transmission technology is particularly attractive for short- to medium-range localization, especially in GPS-denied environments: wide transmission bandwidths enable robust communication in dense multipath scenarios, and the ability to resolve subnanosecond delays results in centimeter-level distance resolution. We will describe several cooperative localization algorithms and quantify their performance, based on realistic UWB ranging models developed through an extensive measurement campaign using FCC-compliant UWB radios. We will also present a powerful localization algorithm by mapping a graphical model for statistical inference onto the network topology, which results in a net-factor graph, and by developing a suitable net-message passing schedule. The resulting algorithm (SPAWN) is fully distributed, can cope with a wide variety of scenarios, and requires little communication overhead to achieve accurate and robust localization.

Cooperative Localization in Wireless Networks

Over the coming decades, high-definition situationally-aware networks have the potential to create revolutionary applications in the social, scientific, commercial, and military sectors Ultrawide bandwidth (UWB) technology is a viable candidate for enabling accurate localization capabilities through time-of-arrival (TOA)-based ranging techniques These techniques exploit the fine delay resolution property of UWB signals by estimating the TOA of the first signal path Exploiting the full capabilities of UWB TOA estimation can be challenging, especially when operating in harsh propagation environments, since the direct path may not exist or it may not be the strongest In this paper, we first give an overview of ranging techniques together with the primary sources of TOA error (including propagation effects, clock drift, and interference) We then describe fundamental TOA bounds (such as the Cramer-Rao bound and the tighter Ziv-Zakai bound) in both ideal and multipath environments These bounds serve as useful benchmarks in assessing the performance of TOA estimation techniques We also explore practical low-complexity TOA estimation techniques and analyze their performance in the presence of multipath and interference using IEEE 802154a channel models as well as experimental data measured in indoor residential environments

/pdf/ranging-with-ultrawide-bandwidth-signals-in-multipath-illizjdvoz.pdf

Ranging With Ultrawide Bandwidth Signals in Multipath Environments

In recent years, indoor positioning has emerged as a critical function in many end-user applications; including military, civilian, disaster relief and peacekeeping missions. In comparison with outdoor environments, sensing location information in indoor environments requires a higher precision and is a more challenging task in part because various objects reflect and disperse signals. Ultra WideBand (UWB) is an emerging technology in the field of indoor positioning that has shown better performance compared to others. In order to set the stage for this work, we provide a survey of the state-of-the-art technologies in indoor positioning, followed by a detailed comparative analysis of UWB positioning technologies. We also provide an analysis of strengths, weaknesses, opportunities, and threats (SWOT) to analyze the present state of UWB positioning technologies. While SWOT is not a quantitative approach, it helps in assessing the real status and in revealing the potential of UWB positioning to effectively address the indoor positioning problem. Unlike previous studies, this paper presents new taxonomies, reviews some major recent advances, and argues for further exploration by the research community of this challenging problem space.

https://www.mdpi.com/1424-8220/16/5/707/pdf

Ultra Wideband Indoor Positioning Technologies: Analysis and Recent Advances.

Abstract 6G networks have the burden to provide not only higher performance compared to 5G, but also to enable new service domains as well as to open the door over a new paradigm of mobile communication. This paper presents an overview on the role and key challenges of signal processing (SP) in future 6G systems and networks from the conditioning of the signal at transmission to MIMO precoding and detection, from channel coding to channel estimation, from multicarrier and non-orthogonal multiple access (NOMA) to optical wireless communications and physical layer security (PLS). We describe also the core future research challenges on technologies including machine learning based 6G design, integrated communications and sensing (ISAC), and the internet of bio-nano-things. 

/pdf/signal-processing-techniques-for-6g-1tsakgql.pdf

Signal Processing Techniques for 6G

Development of an innovative 3D position monitoring system for emergency applications based on wireless sensor network technology

A fundamental problem for signal processing in wireless communications is the separation multiple signals/users from their mixture. The problem would be simpler if they are non-overlapping in either time domain or frequency domain. Two signals may be overlapping in both time and frequency, but they still can be easily separated if they are uncorrelated (orthogonal), like in Code Division Multiple Access system (CDMA). It may be interesting to know that two signals may be overlapping in both the frequency and time domain and also are not orthogonal to each other, but they can still be separated if each autocorrelation function at the receiver is separable in the domain of time-lags. In this paper, we will show how the Noise-Loop (NL) modulation, originally thought to produce security at physical layer, can be used to effectively separate uncoordinated/unorthogonal users sharing the same time and frequency band. In order to show the potential of noise-loop multiple access (NLMA) scheme, the theoretical solution is derived as well as numerical semi-analytical simulations. It can be shown that the NLMA is able to distinguish the bit stream of the users. This feature together with the intrinsic security make the NL an interesting scheme for wireless technology.

/pdf/noise-loop-multiple-access-for-wireless-communications-1njpieg8o2.pdf

Noise-Loop Multiple Access for wireless communications

In the third generation communication system, due to the average increase of the radio link bandwidth requirements and the power constraints at the mobile S-UMTS terminal, the system capacity will meet its physical limitations even in a moderated deployment scenario. In the 3GPP standard, due to the complexity constraints at the user equipment, the DTX implementation on the uplink channel is heavily limited. The transmission scheme presented in this paper is an extension of the traditional informative symbol set with a zero energy symbol. The silence symbols are integrated with the informative ones and delivered to the radio link layer for transmission. The paper presents a theoretical formulation of the optimum two-state receiver. Comparisons with the traditional single-states receiver are obtained with a theoretical approach and through computer simulations. In the latter case a real Globalstar-like S-UMTS environment show the better performances of the proposed scheme for fast varying sources.

/pdf/two-state-cdma-reception-for-satellite-umts-33t637fssy.pdf

Two-state CDMA reception for satellite UMTS

This paper deals with a comparative analysis of the performances of two different communications standards for wireless body area networks (WBAN): ETSI SmartBAN and Bluetooth low energy (BLE). The performance comparison is carried out in additive white Gaussian noise (AWGN) channel as well as in multipath fading channel. Aggregate interference is also taken into account to show which technology tolerates interference better. Both SmartBAN and BLE are possible wireless solutions to implement services like delivering individual's health-related data. The results show that the SmartBAN can outperform BLE in both AWGN and fading channel, in particular, when interference is present, since SmartBAN can take advantage of BCH and repetition features.

Lorenzo Mucchi

Papers

Signal Processing Techniques for 6G

Development of an innovative 3D position monitoring system for emergency applications based on wireless sensor network technology

Noise-Loop Multiple Access for wireless communications

Two-state CDMA reception for satellite UMTS

Performance of wireless body area networks for health: ETSI SmartBAN or Bluetooth?