Abstracts Mathematics

Μοντέλα απωλειών κλήσεων μονοδιάστατης ή πολυδιάστατης τηλεπικοινωνιακής κίνησης σε ασύρματα δίκτυα τεχνολογίας cloud RAN

by Iskanter-Alexandros Chousainov

The cloud radio access network (C-RAN) is considered as a promising fifth generation (5G) network architecture. The C-RAN architecture implies that a number of distributed base stations (BSs) form a centralized network. Each BS is split into two components: the remote radio head (RRH), that includes the antennas and the baseband signal processing server, named baseband unit (BBU). The BBUs are centralized and implemented as virtualized BBUs (V-BBUs) by a computer data center. The pool of V-BBUs is connected to the RRHs via fronthaul links. We consider the C-RAN from the aspect of a loss system. In order for an arriving call to be served by the C-RAN, resource units should be allocated by the RRH (in which the call arrived) and the V-BBU pool (i.e., by the data center). The capacity of the RRH is expressed in radio resource units, while the capacity of the V-BBU pool is expressed in computational resource units. The RRHs are distinguished into homogeneous, when they have same capacity, and into heterogeneous, when they have different capacity of radio resource units. When all calls require the same amount of resource units, then we have single-service traffic, otherwise, when different calls require different amount of resource units, then we have multi-service traffic. In this dissertation, C-RAN systems are examined as loss models. In the first part, we present 14 loss models (of which 12 are novel and proposed), that consider the following cases: the C-RAN has either homogeneous or heterogeneous RRH, the call traffic is either single-service or multi-service and the call arrival process is either random (i.e., Poisson process), quasi-random (i.e., calls are generated by a finite number of users), or compound Poisson (i.e., calls arrive in batches, the size of a batch is random, while the batch arrival follows a Poisson process).The second part of the dissertation examines multi-service loss systems under the so called Threshold Call Admission (TCA) policy. Two loss models are presented (of which one is novel and proposed) that consider a random or quasi-random call arrival process. In the multi-service loss models with TCA policy, calls of the same service-class are distinguished into: new calls and handover calls. The TCA policy sets a threshold (that express a number of in-service calls) for each service class. When the threshold is reached, then new arriving calls are blocked and lost, while handover calls are accepted, in case there are available resource units for the service-class to which they belong. All models, in this dissertation, are analyzed as continuous time Markov chains and for each such Markov chain it is proved that there exists steady-state distribution which is expressed by a product form solution. Based on the product form solution, a convolution algorithm is proposed for the calculation of the congestion probabilities and the system’s capacity utilization. The analytical results of the convolution algorithms were validated with the simulation results via examples. Στην πέμπτη γενιά (5G)…