Smart Planning and Operation in Cellular Networks

Abstract

Cellular networks are less and less regular as operators add base stations (BSs) to increase coverage and performance. Given these facts, we explore the network planning and operation stages of the downlink of a multi-cell Orthogonal Frequency Division Multiple Access (OFDMA)-based network. In the planning stage, which is an offline process, we look at improving expected performance while maintaining good coverage. To do so, we parameterize offline a simple power map assignment to be used by all BSs. In the operation stage, which is an online process, we look at improving performance by handling load imbalance and hotspots in the network. To do so, we propose a heuristic that modifies the power map (from the planning stage) by allocating subchannels to BSs, and specifying for each BS the transmit power to use on the subchannels.

The research questions are as follows: i) Is conventional planning good enough in view of the fact that networks are less and less regular? ii) BS subchannel allocation is typically done only in the planning stage, can we (re)do it more often (i.e., during the operation stage) to improve performance? iii) How can we take load imbalance and hotspots into account when operating a network?

To answer these questions, we propose and investigate one planning scheme and one simple and practical operation scheme in the downlink. We evaluate these schemes on three different network topologies (i.e., 19-cell regular, highly irregular, and lightly irregular). For each we consider both uniform and non-uniform distributions of users (i.e., hotspots). The simulations take place in a dynamic setting with arriving and departing users.

The contributions are as follows: i) We propose a simple power map assignment that we parameterize to offer good performance and good coverage even in highly irregular networks, ii) We propose a heuristic based on BS coordination that allocates subchannels to BSs and specifies for each BS the transmit power to use on the subchannels to handle load imbalance and hotspots, and iii) A practical heuristic implementation that reduces BS coordination.