Goodbye, ALOHA

Hi all,

I am very proud to announce that our paper “Goodbye, ALOHA” has been published in the IEEE Access Journal. This is an open-access paper, which means that it is for FREE. You can access the full paper clicking here.

In this paper we discuss why it is now time to go away from ALOHA-based communication protocols (used in LTE, WiFi, Zigbee, Lora, Sigfox, RFID, etc.), and instead shift to something more advanced. The era of DQ is coming.

This is the full abstract:

The vision of the Internet of Things (IoT) to interconnect and Internet-connect everyday people, objects, and machines poses new challenges in the design of wireless communication networks. The design of medium access control (MAC) protocols has been traditionally an intense area of research due to their high impact on the overall performance of wireless communications. The majority of research activities in this field deal with different variations of protocols somehow based on ALOHA, either with or without listen before talk, i.e., carrier sensing multiple access. These protocols operate well under low traffic loads and low number of simultaneous devices. However, they suffer from congestion as the traffic load and the number of devices increase. For this reason, unless revisited, the MAC layer can become a bottleneck for the success of the IoT. In this paper, we provide an overview of the existing MAC solutions for the IoT, describing current limitations and envisioned challenges for the near future. Motivated by those, we identify a family of simple algorithms based on distributed queueing (DQ), which can operate for an infinite number of devices generating any traffic load and pattern. A description of the DQ mechanism is provided and most relevant existing studies of DQ applied in different scenarios are described in this paper. In addition, we provide a novel performance evaluation of DQ when applied for the IoT. Finally, a description of the very first demo of DQ for its use in the IoT is also included in this paper.




Cellular Networks for the Smart Grid

Hello World,

Our latest paper “Cellular Communications for Smart Grid Neighborhood Area Networks: A Survey“, published at the prestigious IEEE Access Journal, has been already made available for the audience. Access is open and free. You can reach the paper in this link:

This is the result of a joint work with ABB, in Sweden. Putting together ICT and the grid together is quite a tough challenge, but we are getting there.

The abstract of the paper is as follows:

This paper surveys the literature related to the evolution of cellular communications as a key enabling technology for fundamental operations of smart grid Neighborhood Area Networks (NANs). The latest releases of the LTE standard, representing the recent advancements in cellular technology, offer significant benefits to the modernization of the aging power distribution grid compared to other communication technologies. However, since LTE was not originally designed for smart grid applications, important challenges remain unsolved before it can efficiently support advanced NAN functionalities. This survey identifies the limitations of LTE and provides a comprehensive review of the most relevant proposed architectural and protocol enhancements for the communication infrastructure associated with smart grid NANs that can be found in the literature to date. As Device-to-Device (D2D) communications in LTE standards are a promising technology for reducing delay and boost reliability, this paper dwells on the potential gains that can be achieved by enabling direct communication using cellular networks, and also discusses in detail LTE-D2D applicability in representative NAN use cases in the power distribution grid. We conclude by stating open issues and providing research directions for future research in the field. This paper constitutes the first comprehensive survey of proposed LTE-enhancement and D2D solutions for smart grid NANs.

Hope you enjoy the read.



Associate Professor at UPF

Hi all,

I am very happy to share with you that since April 2016, I will be Associate Professor at Universitat Pompeu i Fabra (UPF) in Barcelona (Spain). I am not changing job; this is an activity that I will do in addition to my current position at CTTC. At UPF, I will be teaching during the Spring semester on the topic of Internet of Things: reviewing market and business concepts, wireless technology trends and technologies, and offering a hands-on experience creating IoT prototypes using Arduino and Xbee modules. Let’s say, it will be an end-to-end IoT experience for the students, and also for me, of course.

I think that this lecturing position at one of the best universities in Spain will be a great opportunity for me to spread the IoT word and to be in contact with the new generation of engineers that will be part of the IoT arena in the very near-future.



Dear friends,

Today I write this post to talk about one of our new ventures:

What is this?

A new website and blog related to the IoT, with particular focus on wireless technology and applications.


There is so much information out there in the Internet related to the IoT that it becomes sometimes hard to keep focus on what is really worth reading. I personally spend lots of time in surfing the web and twitter to discover really worthy news and information related to the IoT.

After some random thoughts, I decided to set up a website with that information that I think is very interesting and relevant related to the IoT. And this is

What will be there?

– Links to interesting companies, alliances, products, etc.

– A Blog and Video Blog with entries written by myself talking about topics related to the IoT.

– A blog with entries written by contributors; these are people I trust which I would love to invite to contribute to the website. If you’re interested in becoming a contributor, drop me an e-mail at ““.

Hope to see you around!



Long Range WPAN Extensions in ns-3

Dr. Tatjana Predojev, formed PhD Candidate at CTTC, has released today part of her work carried out over the last 4 years while conducting her PhD Thesis on Long Range Low Power Wireless Technologies.

She extended the lr-wpan code of ns-3 to introduce duty-cycling based on Time Division Multiplex Access (TDMA) which resembles the Time Synchronized Channel Hopping (TSCH) protocol proposed in:

IEEE Standard, “Low rate wireless personal area networks (LR-WPANs) amendment 1: MAC sublayer,” IEEE Standard 802.15.4e, 2012.

The implementation includes all Medium Access Control (MAC) features except for the the channel hopping.

The repository of the code is now public and you are welcome to use it:

In concrete, the most significant changes introduced are in the following modules:

=> implemented packet acknowledgements (ACKs), duty-cycling, link scheduler
refactored code to introduce MAC state

=> implemented log-normally distributed, time-correlated shadowing

Aris Gkoutzos , an undergraduate student supervised by Dr. Predojev, implemented


A detailed description of the implemented algorithm can be found in the open access journal:

T. Predojev, J. Alonso-Zarate, M. Dohler, and L. Alonso, Energy Consumption Optimisation for Duty-Cycled Schemes in Shadowed Environments, International Journal of Distributed Sensor Networks, Hindawi,, 2014.

There are no guarantees for any functionality, nor was the standard implemented in detail.
Nevertheless, we hope someone will find it useful.


A member of our M2M team has been Awarded by KTH (Sweden)

Charalampos Kalalas, member of our M2M team, has been awarded with the KTH ISSLS 2000 Foundation Scholarship in Sweden.

Charalampos has been awarded on November 2014 with the Swedish ISSLS 2000 Foundation Scholarship of KTH for the M.Sc. Thesis Project “Enabling LTE for Control System Applications in a Smart Grid Context”.

The purpose of the foundation is to facilitate scientific research and education within the telecommunication area, specifically those areas which are or will be of importance for the development of various types of access networks. Relevant for this grant is also education within adjacent fields that are of importance for the continuing developments of communication based services.

The scholarship is awarded to students that excel in a distinguished way through a degree project at the M.Sc. level which is well executed, insightful and of high quality. The results from the project should furthermore be expected to make a valuable contribution to the development of various types of access networks or the development of services for communication networks.

Charalampos Kalalas is now a Marie Curie fellow within the research project ADVANTAGE (FP7-607774), hosted by CTTC, and is currently pursuing his PhD in ICT technologies for the Smart Grid at the PhD Program of the Department of Signal Theory and Communications of the Universitat Politècnica de Catalunya (UPC).


4,000 downloads of a book chapter!

Science and research is about impact. This can be measured in many different ways. A typical one consists is counting the number of citations of a given publication. Unfortunately, in some cases this might be tricky due to the use of self-citations (citations by the same author) and the creation of communities of scientists citing each other because of other reasons beyond scientific connection. Another measure of impact is the number of times that a paper, when freely available to the audience (open-access) has been accessed and downloaded from different IP connections (in order to avoid robots accessing a given paper many times).

Today, one of our papers, written in collaboration with Cristian Crespo and Dr. Luis Alonso from Universitat Politècnica de Catalunya in the year 2011, has reached the hit of 4,000 downloads. Wow!!

The research work is entitled “Hybrid Access Techniques for Densely Populated Wireless Local Area Networks” and belongs to the entire book entitled “Advances in Vehicular Networking Technologies”, published by IN-TECH. This chapter describes the design of a novel Medium Access Control (MAC) protocol for Wireless Local Area Networks (WLANs) which can boost the performance of so-called WiFi networks when the number of connected devices is very high. This becomes particularly relevant in dense deployments, as it can be the case of vehicular networks (networks of cars, essentially), or the Internet of Things (IoT).

The paper can be accessed in the following link:

The book can be accessed in the following link:

Let’s keep the spirit!