Physical and Control Layer Solutions for Reliable Machine-Type Random Access

Thumbnail Image

Files

isbn9789526084183.pdf (3.38 MB)

URL

Journal Title

Journal ISSN

Volume Title

School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2019-03-08
Unless otherwise stated, all rights belong to the author. You may download, display and print this publication for Your own personal use. Commercial use is prohibited.

Authors

Date

2019

Department

Tietoliikenne- ja tietoverkkotekniikan laitos
Department of Communications and Networking

Major/Subject

Mcode

Degree programme

Language

en

Pages

94 + app. 62

Series

Aalto University publication series DOCTORAL DISSERTATIONS, 27/2019

Abstract

Machine-type communications (MTC), in both the massive (mMTC) and ultra-reliable (uMTC) variety, will facilitate many new types of applications in 5G networks. Many of these applications will have service requirements that current wireless systems cannot meet. A particular challenge is providing reliable access to the large number of uncoordinated and infrequently active devices that characterise MTC. Restrictions on latencies preclude the traditional use of re-transmissions and lengthy resource scheduling procedures for reliability in the random access channel (RACH), encouraging instead a grant-free access paradigm. In such contention-based access, medium access control (MAC) layer coding schemes that provide repetition diversity are critical for limiting packet losses. This thesis considers Combinatorial Code Designs (CCD) for achieving the targets set for ultra-reliable low-latency communications (URLLC) in the 5G RACH. In contrast to coded access schemes which use random coding, we show that uniquely pre-allocating repetition patterns to users from a code designed specifically for use with successive interference cancellation (SIC) is a better solution for URLLC. We introduce interference cancelling (IC) codes that guarantee successful reception of all simultaneously accessing users up to a given number, which are shown to be particularly robust to packet loss when user activity is low, as in MTC. Simulations demonstrate that these codes outperform ALOHA-type schemes and meet the "five nines" reliability target of URLLC in both a simple collision model and a more realistic scenario that models both the MAC and physical (PHY) layers. Fully characterising the impact of the PHY layer uplink waveform on reliability is also paramount in designing an ultra-reliable random access procedure for 5G. As such, this thesis considers measures of time-frequency localisation (TFL) for stochastic signals. Such measures are complementary to those traditionally used in prototype filter design. We derive a generalised Heisenberg measure for multi-dimensional stochastic signals, consider the specific case of Gabor systems, and discern relevant bounds. The generalised TFL measure describes how well multiplexed waveform packets are contained inside their time-frequency resources, and thus their inter-user interference potential in a multiple-access scenario. We confirm the measure's veracity by simulating an asynchronous, grant-free random access system, and comparing the performance of small packets of common waveforms. At lower user activity, where out-of-band emissions are the limiting factor to reliability, the respective performances of these waveforms is consistent with the presented theory.

Description

Supervising professor

Tirkkonen, Olav, Prof., Aalto University, Department of Communications and Networking, Finland

Thesis advisor

Vehkalahti, Roope, Dr., Aalto University, Department of Communications and Networking, Finland

Keywords

ultra-reliable low-latency communications, random access, combinatorial code designs, interference cancellation, time-frequency localisation

Other note

Parts

  • [Publication 1]: C. Boyd, R. Vehkalahti, O. Tirkkonen. Combinatorial Code Designs for Ultra-Reliable IoT Random Access. In IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), 2017, Montreal, pp. 1-5.
    DOI: 10.1109/PIMRC.2017.8292784 View at publisher
  • [Publication 2]: C. Boyd, R. Vehkalahti, O. Tirkkonen. Interference Cancelling Codes for Ultra-Reliable Random Access. International Journal of Wireless Information Networks (IJWIN), 2018. Full Text in Acris/Aaltodoc: http://urn.fi/URN:NBN:fi:aalto-201808214698.
    DOI: 10.1007/s10776-018-0411-6 View at publisher
  • [Publication 3]: C. Boyd, R. Vehkalahti, O. Tirkkonen. Grant-Free Access in URLLC with Combinatorial Codes and Interference Cancellation. In IEEE Global Communications Conference (GLOBECOM), Abu Dhabi, December 2018.
  • [Publication 4]: Y. Beyene, C. Boyd, K. Ruttik, C. Bockelmann, O. Tirkkonen, R. Jäntti. Compressive Sensing for MTC in New LTE Uplink Multi-User Random Access Channel. In AFRICON, Addis Ababa, 2015, pp. 1-5.
    DOI: 10.1109/AFRCON.2015.7331960 View at publisher
  • [Publication 5]: C. Boyd, R.-A. Pitaval, O. Tirkkonen,R. Wichman. On the Time-Frequency Localisation of 5G Candidate Waveforms. In IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC), Stockholm, 2015, pp. 101-105.
    DOI: 10.1109/SPAWC.2015.7227008 View at publisher
  • [Publication 6]: C. Boyd, R.-A. Pitaval, O. Tirkkonen, R. Wichman. Localization Measures for Orthogonally Multiplexed Signals. Submitted to IEEE Transactions on Communications, September 2018.

Citation

Permanent link to this item

https://urn.fi/URN:ISBN:978-952-60-8418-3

Collections

[diss] Sähkötekniikan korkeakoulu / ELEC