Efficient anomaly detection in urban water distribution networks is crucial for sustainable resource management. Identifying abnormal patterns in time-series data from sensors is a common task within industrial settings and automated methods can enhance efficiency and reduce costs. However, supervised learning is often impractical due to the scarcity of labeled anomalous data in settings of practical interest. Consequently, unsupervised techniques are typically used, identifying anomalies as deviations from normal behavior. This paper introduces a framework that combines Long Short-Term Memory (LSTM) and Transformer encoder-decoder networks in a hierarchical structure to predict future water usage and detect anomalies in an unsupervised manner. Our method optimizes the use of available data within practical settings, where partial information might not be available at some points, ensuring high inference efficiency and enabling near real-time anomaly detection. It is adaptable to various data configurations, making it suitable for different environments. Our approach, applied to data from the metropolitan area of Barcelona, highlights its potential to refine early anomaly detection, prevent resource loss, and promote sustainable consumption.

Smart cities have been receiving great focus during the recent years. One important topic that it covers is the use of technologies to help the connection between smart cities and citizens. These links can influence different cities services and governance such as transport, politics, education, public transparency, citizens' rights, among others. Those services work much better when they are connected, interconnected, participative and transparent. Any kind of environment requires these improvements, both in underdeveloped and developed countries. In this sense, for this cultural and evolution process, it is important to understand how the citizens are responding to these technological stimulus. This work describes and investigates how these themes are treated in the literature, using bibliometric method and data from SCOPUS, Web of Science (WoS), IEEEXplore. In this study, discussions will be focused on the technological area, however, with efforts in reaching distinct strategical areas that are nowadays working side by side on it.

The traditional IEEE 802.11 DCF allows only one node to access the channel each time. In order to take the benefit of multiple simultaneous uplink transmissions when the AP is equipped with multiple antennas, a new MAC protocol called DCF/USDMA is presented in this paper. DCF/USDMA extends the IEEE 802.11 Distributed Coordination Function (DCF) by introducing a second contention round, which is used to accommodate the multiple simultaneous transmissions from multiple stations. Results show that the DCF/USDMA protocol is able to achieve a significant performance gain compared to that of the conventional DCF, the analysis of which also provides some insights about how the different parameters that control the DCF/USDMA operation can be optimized.

This paper presents CSMA/ECA, which combines the efficiency of reservation-based protocols and the simplicity of random access mechanisms. The maximum efficiency of CSMA/CA with optimal parameter adjustment is easily exceeded by CSMA/ECA, even when fixed parameters are used by the latter. CSMA/ECA stations fairly coexist with legacy CSMA/CA and increase the portion of time that is devoted to successful transmissions while decreasing the number of collisions and empty slots. The proposed mechanism initially behaves as a CSMA/CA network, but it progressively converges to a collision-free deterministic operation. The convergence process can be modelled as a Markov Chain to assess the duration of the transitory phase.

Guifi is a community-based telecommunications network that originated in a rural area of the Spanish region of Catalonia. Guifi primarily uses unlicensed spectrum for its communications links, and its users create network nodes on a volunteer basis from state-of-the-art yet inexpensive off-the-shelf WiFi equipment. Guifi's self-organizing community is governed by a Wireless Commons charter that views unlicensed spectrum as a public asset, which means that Guifi satisfies the definition of both an open Commons (an open network with free access) and a closed Commons (a self regulating community with a well defined charter). This article identifies key factors for the exponential growth and success of the WiFi network, which has put some rural areas in Catalonia well above European average for broadband penetration. Moreover, this article identifies the threats that Guifi faces as both an open and closed Commons, and explores what Guifi does or should do to mitigate them. These threats are referred to in literature as the “Tragedy of the Commons”. Finally, the article also considers possible consequences of Guifi's intentions to expand its network with fiber connections.

Carrier Sense Multiple Access with Enhanced Collision Avoidance (CSMA/ECA) is a recently proposed modification to the well-known CSMA/CA protocol. By using a deterministic backoff after successful transmissions, the number of collisions decreases. This article presents a model that captures the behaviour of CSMA/ECA in both saturated and non-saturated scenarios. The results, which are validated by simulations, show that CSMA/ECA effectively prevents collisions and, therefore, it can deliver a higher throughput than CSMA/CA.

Multi-user MIMO allows the simultaneous transmission of several link-layer frames directed to different users by exploiting the channel's spatial streams, increasing proportionally the effective channel capacity. Nevertheless, the system performance can be further increased if several frames directed to the same user are combined together on a temporal scale (i.e. packet aggregation), taking benefit from both space and time dimensions. In this paper, a novel finitebuffer space-time general-distributed batch-service queueing model for such a system is presented. Results show the flexibility and accuracy of our queuing model, providing also a first insight on the relation between the space and temporal aggregation parameters and how they can be adjusted to maximise the system performance.

CSMA with Enhanced Collision Avoidance (CSMA/ECA) uses a deterministic backoff after successful transmissions to significantly reduce the number of collisions. This paper assesses by means of simulations the throughput and conditional collision probability obtained from a single-hop ad-hoc network using CSMA/ECA. A comparison with the legacy CSMA/CA reveals that the proposed protocol outperforms the legacy one in all considered scenarios. Specifically, it is shown that CSMA/ECA presents advantages for both rigid and elastic flows.

A novel flow admission control mechanism for infrastructure IEEE 802.11e EDCA-based WLANs is presented. The proposed admission control works jointly with a tuning algorithm which decides the most suitable configuration of the MAC parameters each time a new flow arrives or leaves the system. It is designed to work in heterogeneous scenarios with both elastic and real-time flows, so it aims to: i) guarantee the QoS requirements for real-time flows (like VoIP) and ii) maximize the best-effort throughput (such as TCP web browsing or P2P transfers). Results, compared with the use of the DCF (distributed coordination function) and EDCA (enhanced distributed channel access) with static parameters, show a clear improvement on the overall HotSpot performance. Our mechanism provides better QoS, uplink versus downlink fairness and a more efficient use of the transmission resources.

GSM/GPRS networks have been designed to carry both voice and data traffic. Our aims are to study the behaviour of the GPRS mechanisms (RLC/MAC layer and radio resource scheduler) when the application layer carries packetized voice, and determine if the quality of service provided by the network is suitable for the VoIP service. The paper includes a discussion about the voice source model, an analysis of the effects in capacity of a GPRS carrier when feed with VoIP packets, measurements of statistical parameters of the voice traffic stream and a discussion of the influence in the quality of the service.

We propose a variable reservation scheme for cellular networks, based on prioritization of hand-off calls over new calls. This problem has been extensively studied in the literature, and several schemes consisting of call-request queuing, fixed reservation of channels or combinations of both have been proposed. We take advantage of the information reported by the mobile terminal to adaptively establish the number of channels to be reserved in the target cell. The effect of progressive channel degradation in the overlapping zone between cells is also taken into account. Performance evaluation is done using infinite two-dimensional Markov chains. A noticeable improvement in blocking and call-dropping probabilities is achieved using this new mechanism.

An evaluation of the capacity of the GPRS, as a packet-switched access mode for the GSM system, is studied. The work has been done assuming an air interface proposed in an ETSI draft document and taking two traffic models also standardised by this institution. Statistical multiplexing allows several users to share radio channels increasing the capacity of the system. Thus, the results obtained are: throughput and access delay depending on the number of subscribers each of them with an identical activity factor. We have also studied the 95th percentile of access delay and delay distributions in order to assure the QoS of the system.