Resource allocation in wireless access network : A queueing theoretic approach

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2016-08-11
Degree programme
130 + app. 152
Aalto University publication series DOCTORAL DISSERTATIONS, 137/2016
To meet its performance targets, the future 5G networks need to greatly optimize the Radio Access Networks (RANs), which connect the end users to the core network. In this thesis, we develop mathematical models to study three aspects of the operation of the RAN in modern wireless systems. The models are analyzed using  the techniques borrowed mainly from queueing theory and stochastic control. Also, simulations are extensively used to gain further insights. First, we provide a detailed Markov model of the random access process in LTE. From this, we observe that the bottleneck in the signaling channel causes congestion in the  access  when a large number of M2M devices attempt to enter the network. Then, in the context of the so-called Heterogeneous networks (HetNets), we suggest  dynamic load balancing schemes that alleviate this congestion and reduce the overall access delay. We then use flow-level models for elastic data traffic to study the problem of coordinating the activities of the neighboring base stations.  We seek to minimize the flow-level delay when there are various classes of users. We classify the users based on their locations, or, in dynamic TDD systems, on the direction of service the network is providing to them. Using interacting queues and different operating policies of running such queues, we study the amount of gain the dynamic policies can provide over the static probabilistic policies. Our results show that simple dynamic policies can  provide very good performance in the cases considered. Finally, we consider the problem of opportunistically scheduling the flows of users with time-varying channels  taking into account   the size of data they need to transfer. Using flow-level models in a system with homogeneous channels, we provide the optimal scheduling policy when there are  no new job arrivals. We also suggest the method to implement such a policy in a time-slotted system. With heterogeneous channels, the problem is intractable for the flow-level techniques. Therefore, we utilize the framework of the restless-multi-armed-bandit (RMAB) problems employing the so-called Whittle index approach. The Whittle index approach, by relaxing the scheduling constraints, makes the problem separable, and thereby provides an exact solution to the modified problem. Our simulations suggest that when  this solution is applied as a heuristic to the original problem, it gives good performance, even with dynamic job arrivals.
Supervising professor
Jäntti, Riku, Prof., Aalto University, Department of Communications and Networking, Finland
Thesis advisor
Aalto, Samuli, Docent, Aalto University, Finland
Lassila, Pasi, Docent, Aalto University, Finland
resource allocation, wireless network, queueing theory, scheduling
Other note
  • [Publication 1]: Prajwal Osti, Pasi Lassila, Samuli Aalto, Anna Larmo, Tuomas Tirronen. Analysis of PDCCH performance for M2M traffic in LTE. IEEE Transactions on Vehicular Technology, Vol. 63, No. 9, pages 4357–4371, November 2014.
    DOI: 10.1109/TVT.2014.2314532 View at publisher
  • [Publication 2]: Prajwal Osti, Samuli Aalto, Pasi Lassila. Load balancing for M2M random access in LTE HetNets. In Proceedings of IEEE 22nd International Symposium on Modeling, Analysis and Simulation of Computer and Telecommunication Systems (MASCOTS 2014), pages 132–141, Paris, France, September 2014.
    DOI: 10.1109/MASCOTS.2014.25 View at publisher
  • [Publication 3]: Prajwal Osti, Samuli Aalto, Pasi Lassila. Minimizing access delay for M2M traffic in multi-RAT HetNets. In Proceedings of the 18th ACM International Conference on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWiM’15), pages 161–170, Cancun, Mexico, November 2015.
    DOI: 10.1145/2811587.2811602 View at publisher
  • [Publication 4]: Prajwal Osti, Samuli Aalto, Pasi Lassila. Optimal intercell coordination for multiple user classes with elastic traffic. In Proceedings of the 8th EURO-NGI Conference on Next Generation Internet (NGI 2012), pages 25–32, Karlskrona, Sweden, June 2012.
    DOI: 10.1109/NGI.2012.6252161 View at publisher
  • [Publication 5]: Prajwal Osti, Samuli Aalto, Pasi Lassila. Flow-level modeling and optimization of intercell coordination with dynamic TDD. In Proceedings of the 10th ACM Symposium on QoS and Security for Wireless and Mobile Networks (Q2SWinet’14), pages 109–118, Montréal, Canada, September 2014.
    DOI: 10.1145/2642687.2642698 View at publisher
  • [Publication 6]: Prajwal Osti, Samuli Aalto, Pasi Lassila. Performance and optimization of dynamic-TDD intercell coordination with elastic traffic. Accepted for publication in Telecommunication Systems, 2016.
  • [Publication 7]: Samuli Aalto, Aleksi Penttinen, Pasi Lassila, Prajwal Osti. On the optimal trade-off between SRPT and opportunistic scheduling. In Proceedings of the ACM SIGMETRICS International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS ’11), pages 185–195, San Jose, USA, June 2011.
    DOI: 10.1145/1993744.1993761 View at publisher
  • [Publication 8]: Samuli Aalto, Aleksi Penttinen, Pasi Lassila, Prajwal Osti. Optimal size-based opportunistic scheduler for wireless systems. Queueing Systems, Vol. 72, No. 1, pages 5–30, March 2012.
    DOI: 10.1007/s11134-012-9285-y View at publisher
  • [Publication 9]: Samuli Aalto, Pasi Lassila, Prajwal Osti. Whittle index approach to size-aware scheduling with time-varying channels. In Proceedings of the ACM SIGMETRICS International Conference on Measurement and Modeling of Computer Systems (SIGMETRICS ’15), pages 57–69, Portland, USA, June 2015.
    DOI: 10.1145/2745844.2745851 View at publisher