+ Internship subject: Connectionless Transmission in IoT Networks
During the recent years, there has been a lot of interest in the research community on different aspects of IoT communication systems [1]; the studies have focused on technologies involving short-range, medium-range or long-range radio.
The particular case of long-range radio has been popular recently, as it perfectly fits a new scenario for IoT: the scenario where communications are infrequent (such as a few messages per hour) but coming from a massive number of devices. Such
scenarios are handled by unlicensed band technologies such as LoRa, Sigfox, etc., and, in the cellular world, NB-IoT, and the upcoming massive access in 5G networks (and beyond).
The design trade-offs for such communications departs from the traditional cellular network design, as the signalling cost and delay of maintaining a connection, may dominate. For that reason, a recent trend has been to focus on reducing the
signalling cost, in particular with connectionless transmissions at the network level, and from the physical layer point of view, with Non-Orthogonal Multiple Access (NOMA) [2].
One recent family of such methods is the family of Coded Slotted Aloha methods [3].
It is conceptually simpler than some other NOMA methods since it operates as follows: it consists in retransmitting replicas of each packet (possibly with a
predefined error correcting scheme), and introducing the mechanism of physically and successively removing the signal of every packet that has been successfully retrieved at the position of its replicas. In the classical Slotted Aloha setting where collisions are considered as losses, it can achieve the maximum throughput of one retrieved packet per slot [3]. In real deployments of IoT networks, the signal strength from different nodes can be widely different and therefore simultaneous
transmissions do not necessarily result in “collision”, but can result in a “capture” if one signal is stronger. Preliminary work has been done illustrating the good
performance of Coded Slotted Aloha with capture [4].
The subject is around constructing next generation IoT access protocols. Several directions are possible; one or two of them will be followed during the internship.
They include:
- Network/MAC protocol design: by combining the concept of multihop routing with coded slotted aloha, the performance of the protocol can be improved in a number of ways. Tools: simulations (ns-2, ns-3, matlab, …) or simplified models.
- Network/MAC protocol design: in unlicensed band (such as with LoRa networks), where transmitters are uncoordinated, it is a challenge to coordinate the node in a distributed way with few messages, before apply more sophisticated methods (matlab, python simulation, …).
- MAC Protocol design: in standard coded slotted aloha, no feedback, or minimal feedback is assumed. By introducing some for of feedback we expect that 1) the performance of number of nodes will be improved, 2) the loss rate could be easily improved, moving in the ultra-reliable low-latency field. Tools: simulations on simplified network models.
- Performance evaluation through modelling: two aspects are best captured by modelling, it is the capture effect through stochastic geometry, and the evolution of the decoding process (as iterative equations). Tools: mathematical modelling with stochastic geometry.
Supervisors: Cédric Adjih (Inria Saclay), Paul Mühlethaler (Inria Paris), and Amira
Alloum (Nokia Bell Labs), Philippe Jacquet (Nokia Bell Labs) Place: Inria Paris or Inria Saclay
Duration: ~6 months
Stipend: ~550 EUR /month
Contact: Cedric.Adjih@inria.fr and Paul.Muhlethaler@inria.fr
[1] Shariatmadari, Hamidreza, et al. "Machine-type communications: current status and future perspectives toward 5G systems." Communications Magazine, IEEE 53.9 (2015): 10-17.
[2] Dai, L., Wang, B., Yuan, Y., Han, S., Chih-Lin, I., & Wang, Z. (2015). Non- orthogonal multiple access for 5G: solutions, challenges, opportunities, and future research trends. Communications Magazine, IEEE, 53(9), 74-81.
[3] E. Paolini, C. Stefanovic, G. Liva, and P. Popovski, “Coded random access:
applying codes on graphs to design random access protocols,” IEEE Communications Magazine, vol. 53, no. 6, pp. 144–150, 2015.
[4] E. E. Khaleghi, C. Adjih, A. Alloum, and P. Muhlethaler, “Near-Far Effect on Coded Slotted ALOHA”, IoT Workshop, PIMRC 2017, oct. 2017.
