Keynote on Massive and Ultra-Reliable Access at IEEE ICC Workshops

I have given a keynote speech at the IEEE MASSAP Workshop at ICC 2015 in London. The talk is on wireless massive and ultra-reliable communications, which are seen as two new modes that will be featured in 5G. There is, of course, a technical part in the talk, but there is also a part which argues why the research on wireless and communication theory is still vital. The slides can be found here:

Wireless Lowband Communications: Massive and Ultra-Reliable Access

How Many Smart Meters can be Deployed in a GSM cell?

The need to deploy large number of wireless devices, such as electricity or water meters, is becoming a key challenge for any utility. Furthermore, such a deployment should be functional for more than a decade. Many cellular operators consider LTE to be the single long-term solution for wide area connectivity serving all types of wireless traffic. GSM/GPRS is a well-adopted technology and represents a valuable asset to build M2M infrastructure due to the good coverage, device maturity, and low cost. We recently submitted a paper in which we assess the potential of GSM to operate as a dedicated network for M2M communications. In order to enable M2M-dedicated operation in the near future, we reengineer the GSM/GPRS/EDGE protocol in a way that requires only minor software updates of the protocol stack. We propose different schemes to boost the number of M2M devices in the system without affecting the network stability. We show that GSM a single cell can support simultaneous low-data rate connections (e. g. to smart meters) in the order of 10^4 devices.

Ideal system in which the bandwidth is shared among the multiplexed devices. The protocol operation is limiting the number of devices, despite the application requirements.
Ideal system in which the bandwidth is shared among the multiplexed devices. The protocol operation is limiting the number of devices, despite the application requirements.

Ideally, a TDMA system should be able to allocate as many as possible devices as long as the quality of service is guaranteed. However, in practice, systems are typically not able to operate in this manner. GSM and GPRS are an example of a TDMA system limited by the protocol rather than the application requirements of the smart meters. Specifically, for smart metering, a payload below 1000 bytes is expected. Moreover, the traffic patters corresponds to device originated with periodical reporting in the range of 5 mins, 15 mins, 1 hour and 6 hours. These devices tolerate a delay up to the next scheduled transmission opportunity if the message was not successfully delivered.

The main idea is that resources are pre-allocated according the application needs. In this manner, thousands of simultaneous connections can take place in a single cell (a single frequency is considered). In addition, we analyze the probability of reports exceed the deadline.  This probability is presented in the following figure, where it is noticeable that for the most demanding case when RI=1min, a single cell could provide service for up to 5 · 10^3 simultaneous connections with a reliability of 99.99%. This number rises to outstanding value of 5 · 10^4 simultaneous connections that are served with 99.99%, if the reporting interval is set to 15 min.

Probabilty report arriving after deadline as a function of report interval RI, report size 100 bytes.
Probability report arriving after deadline as a function of report interval RI, report size 100 bytes.

The paper has been submitted to ICC’13 (Second IEEE Workshop on Telecommunication Standards). Download

First impressions on the IEEE 802.11ah standard amendment

As highlighted in the previous blog post, there is a new emerging standard in the M2M arena based on the IEEE 802.11 standards family. This standard is being developed under the IEEE 802.11ah group, and aims to define the physical (PHY) and medium access control (MAC) layers that operate at radio frequencies below 1 GHz. One of the goals of this standard is to ensure that the transmission ranges up to 1 km and that the data rates per user are above 100 kbit/s.

The standard is currently being drafted, but some essential details about this new standard are already available, which we will highlight in this blog post. It is important to emphasize that although the IEEE 802.11ah standard will define operations below 1 GHz, it will not use the TV white space bands (54-698 MHz in the US), which are targeted instead by IEEE 802.11af.

The PHY transmission in IEEE 802.11ah is an OFDM based waveform consisting of a total of 64 tones/sub-carriers (including tones allocated as pilot, guard and DC), which are spaced by 31.25 kHz. The modulations supported include BPSK, QPSK and 16 to 256 QAM. It will support multi user MIMO and single user beam forming.

In [1] is stated that stations will support the reception of 1 MHz and 2 MHz PHY transmissions. The channelization (i.e. operating frequency) depends on the region. In Europe it will be within 863-868 MHz, allowing either five 1 MHz channels or two 2 MHz channels. While in the US the available band will be within 902-928 MHz, allowing either twenty-six 1MHz channels or thirteen 2MHz channels. In Japan, the available band is within 916.5-927.5 MHz, with eleven 1MHz channels. In China the available band will be within 755-787 MHz, with thirty-two 1 MHz channels. South Korea and Singapore also have specific channelizations that can be found in [1].

The MAC layer will include a power saving mechanism and an alternative approach to perform channel access, which will allow an access point to support thousands of stations, as required for M2M applications. The channel access also supports a mode of operation where only a restricted number of stations can transmit.

There are several use cases for this standard [2], which include:

  • Sensor Networks – where the IEEE 802.11ah is used as the communication medium for the transmission of short-burst data messages from sensors, which include smart metering;
  • Backhaul networks for sensors – where the IEEE 802.11ah can be used to create the backhaul of mesh networks created by IEEE 802.15.4 networks;
  • Extended Wi-Fi range for cellular traffic off-loading – where the IEEE 802.11ah can be used to off-load traffic from a cellular network. The caveat is that the performance should be at least comparable with the one from the cellular network;
  • M2M communications – Whereas current systems are optimized more for human-to-human (H2H) communications, IEEE 802.11ah standard will mainly consider sensing applications.
  • Rural communication – Wireless communication in rural areas has led to some effort that is also titled as bridging the digital divide. Large potential is given by sub 1 GHz due to the wider supported range.

In future blog posts, we will follow up with the standardization activities in IEEE 802.11ah.

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M2M @ IEEE Globecom 2012

M2M has been a notable topic in IEEE Globecom 2012, ranging from tutorials, industry fora and a dedicated workshop, featuring technical papers and a panel. Perhaps the most interesting discussions were circling around the question which of the wide area wireless technologies will prevail and transform itself into a dominant M2M solution.

2G (GSM/GPRS) is a very mature technology, long abandoned by the cutting-edge research in wireless communications, but the one that has won the trust of the end users due to its ubiquity, reliability, energy efficiency and low cost. Our groups will soon publish a paper where we show that GSM/GPRS, using only rather minor software updates of the protocol stack, can be converted into M2M-dedicated system, in which a single cell can support 10000 simultaneous low-data rate connections (e. g. to smart meters). But, although technologically possible, 2Gmay not survive as a dedicated M2M solution on a long run due to other factors. First, in many countries 2G is scheduled to be closed down and release the frequency. the plan is to refarm the spectrum for LTE. Second, even if 2G can keep the operating frequency, the operators will not be willing to maintain multiple technologies in their network, and in that case LTE is a clear winner.

But, if 2G can technologically support various M2M applications, perhaps it can re-emerge in another form. For example, operate on a single frequency, keeping a narrow band and being owned by a M2M service provider i. e. not necessarily by a company that is also a mobile LTE-based provider. A more radical thought could be to put 2G in a certain license-exempt spectrum and large M2M users (e. g. utilities) may have their own 2G cells; the license-exempt operation could be created in a way to facilitate interference management among 2G cells that have different owners and are in proximity where they can cause interference. How about porting 2G into a “cognitive M2M radio”, by re-engineering it through protocol (software) updates?

Another thing is the role of 3G. The M2M discussion is very often between 2G and 4G; however, Qualcomm presented their solution in which CDMA-based protocols are re-engineered to support different M2M requirements (latency, reduced access overhead, etc.). Considering the impact of Qualcomm, it is clear that 3G should also be considered in the M2M discussion.

Finally, an emerging technology in the M2M arena is the sub-GHz WiFi specified as IEEE 802.11ah, dedicated to sensor networks and smart metering, and scheduled for finalization in May 2015.

MASS M2M at 3rd ETSI Workshop

Two of our researchers (German and Nuno) are at the 3rd ETSI Workshop presenting a poster about our ongoing work in enhancing the capacity of GPRS and LTE in the Radio Access Network.


There are more than 220 participants attending the workshop.

German and Nuno will post a summary of the events in the workshop in the end of the day.

If you are around come and visit them in the poster section during the coffee breaks.

M2M workshop at FTW in Vienna, September 26, 2012

Our research group was represented at the 1-way workshop on M2M communications arranged by FTW in Vienna. The program can be found here:

Petar’s presentation was about “Communication protocols for mass M2M access” and the slides can be found here.

The Rise and the Research of Machine-to-Machine (M2M) Communication

This is a research blog dedicated the communication technologies that are related to Machine-to-Machine (M2M) communication. We will primarily provide information related to our research project MassM2M, but also analysis of the relevant literature, technology trends, and research ideas.

What is M2M?

Probably today you have used M2M communication if you paid by a credit card. The terminal (a machine) in the shop connects to a server (another machine) in order to approve the transaction. M2M is about communication between devices, objects, things, which is different from Human-to-Machine (H2M) (e. g. “Googling”) or Human-to-Human (H2H) (e. g. “Skyping”).

Techno-economical forecasts indicate that in the coming years M2M communication will become massive, connecting tens of billions devices. Wireless chips have grown in capability and power efficiency, while shrinking in size and cost. It becomes affordable to embed wireless chips in many diverse objects and make them “digitally visible”, similar to the way a person is digitally visible through Facebook.

M2M becomes massive also in terms of diversity across applications. Wireless M2M networks are instrumental to manage the complexity of tracking, fleet, and asset management. The industrial sector can widely apply M2M in monitoring and control of processes and equipment. Radio Frequency Identification (RFID) in the retail industry is an example where M2M enables real-time visibility of the individual items. The M2M showcase is the smart grid: the evolved power grid where a rich information flow is used to balance the electricity production (e. g. windmills), distribution, storage, and consumption (e. g. large industrial capacities).

M2M has a large transformational power to make the processes more efficient by saving time, costs, and energy. But the present optimism about M2M is also fueled by its promise for new business models and the large innovation potential. The companies that use M2M, such as the industrial sector, can introduce novel features in their products and deploy new, information-intensive services. The companies that provide M2M services, such as the telecom operators, see them as important alternatives to the flat-data-rate-like services.

Skeptics may question the upcoming M2M revolution, pointing, for example, that RFID has been around for years, but failing to become massive. This is true; but it was also true that the phrase “smart phone” had been around from 1992, while it lifted off with the iPhone in 2007. Recall that the mobile phone started with voice as a single application at its focus, only to become our assistant and chief entertainer. M2M communication has started slowly with a wide range of applications, so our expectations should be very high for the upcoming billion connected devices.

Research on M2M

M2M services are already up and running in the networks of many mobile operators. Furthermore, there is are very active standardization processes related to M2M in different bodies, such as ETSI or 3GPP. So, is there a need/space for carrying out fundamental research on M2M communication technologies?

Our answer is (clearly) yes. Specifically, there are two (expected or predicted?) features of M2M communication that allow one to pose new and interesting research questions:

  • The “Massive” feature: Technology predictions say that by 2020 there will be 50 billion connected wireless devices, spanning a wide application range: smart grid, metering, control/monitoring of homes and industry, e-health, etc. Wireless networks need a revolutionary reengineering to be able to embrace the massive number of devices. In many cases M2M traffic will feature short data packets, where the useful data is comparable in size to the signaling overhead used to send that packet. To- day the networks can efficiently carry large data from few devices; the problem is how to carry few bytes from a large set of devices (machines). In a nutshell, sending 100000 bytes from one device is very different form sending 1 byte from 100000 different devices; the latter will clearly consume much more resources for signalling/coordination.
    •    The requirement for dependability. M2M communication becomes vital for various control, monitoring, and industrial processes, where it is critical to keep the wireless link alive during 99.99+% of the time. This is in a stark contrast to many existing systems, such as WiFi, which works fine around 95% of the time, but offers zero data rate under harsh receiving conditions. Increased dependability means that the wireless link is available almost all the time and, under harsh conditions, it can scale down the data rate in order to maintain reliable connection.

Other M2M issues that pose interesting research questions are security and device management. They are only peripherally related to our research, but it has to be noted that they also essential for wide adoption of wireless M2M deployments.

Regarding our research approach, we have two different tracks. In one track we investigate protocols and algorithms for rather generic communication systems. An example is Frameless ALOHA, where we are exploring a new concept for massive random access. In the second track we adapt our research context to a particular system, such as LTE, see the article on Code-Expanded Access in LTE. Although it may seem far from the cutting-edge research, we are very interested in the GSM system. We believe that the GSM networks should not be put out of use, but rather to be re-engineered and dedicated to M2M traffic. Even the research on GSM can become fundamental if we understand the GSM protocols and structure as design constraints for new protocols and signalling schemes that should be built on top of it. Our initial activities related to dependable wireless communication have been chiefly related to the university spinoff Wisecan.