Dimensioning of the downlink in OFDMA cellular networks via an Erlang's loss model

Abstract

In this paper we propose the following approach to the dimensioning of the radio part of the downlink in OFDMA networks. First, we use information theory to characterize the bitrate in the channel from a base station to its mobile. It depends on the power and bandwidth allocated to this mobile. Then, we describe the resource (power and bandwidth) allocation problem and characterise feasible configurations of bit-rates of all users. As the key element, we propose some particular sufficient condition (in a multi-Erlang form) for a given configuration of bit-rates to be feasible. Finally, we consider an Erlang's loss model, in which streaming arrivals whose admission would lead to the violation of this sufficient condition are blocked and lost. In this model, the blocking probabilities can be calculated using Kaufman-Roberts algorithm. We propose it to evaluate the minimal density of base stations assuring acceptable blocking probabilities for a streaming traffic of a given load per surface unit. We validate this approach by comparison of the blocking probabilities to these simulated in the similar model in which the admission control is based on the original feasibility property (instead of its sufficient condition). Our sufficient bit-rate feasibility condition can also be used to dimension the network with respect to the elastic traffic.

Analytical expressions for blocking and dropping probabilities for mobile streaming users in wireless cellular networks

“…In this case, some results of the present paper such as (6) are sufficiently general to hold true also in this case. Moreover, there is no obvious reason so that an approximation such as (7) is not accurate any more. Nevertheless, it is interesting in future work to check (7) in the case of shadowing.…”

“…It is shown in [7] that a sufficient condition for the feasibility of resource allocation is that each base station u respects the following inequality for the users of its own cell Z…”

“…In this approach, a given configuration of users with predefined bit-rates is feasible if there exists a resource allocation which respects the information theory constraint as well as the maximal power and total bandwidth constraints (see [7] for more details). However, solving the resource allocation problem for a large network is a very complicated task.…”

“…2 Recent cellular networks use OFDMA. 3 For such networks, we will consider that the capacity constraint is that the resource (power and bandwidth) allocation is feasible as proposed in [7] (more details will be given in Sect. 4.1).…”

Automatic UMTS system resource dimensioning based on service traffic analysis

“…Blaszczyszyn and Karray [23] use an Erlang's loss model to dimension downlink in OFDMA networks. Karray [24] particularizes the downlink QoS study to streaming and elastic traffics.…”