Magnus Almgren

An infrastructure cost evaluation of single- and multi-access networks with heterogeneous traffic density

Traditional performance measures like capacity, cell radius and supported QoS are often insufficient when comparing wireless networks with different network architectures and cost structures. Instead, in this paper, infrastructure cost is used to compare different operator deployed single- and multi-access wireless networks, including 3G, WLAN and proposed 4G radio access technologies. For this purpose a model for the geographical distribution of traffic is introduced. Despite the spatially non-uniform traffic demand, single-access solutions like WCDMA high-speed downlink packet access (HSDPA) or long-term 3G evolved, with high capacity macro cellular base stations, typically yield the lowest costs per user. In particular this holds for a hypothetical long-term 3G evolved system operating in 450 MHz spectrum, which indicates the importance of good coverage. Operator deployed WLAN-only solutions are more expensive even for small fractions of supported users. Multi-access solutions, combining for example WCDMA DCH or HSDPA with WLAN, do not seem to provide better cost efficiency than standard hierarchical cell structures in single-access systems. Instead, multi-access solutions have to be motivated by other factors like peak data rates and spectrum availability.

Simplified Interference Modeling in Multi-Cell Multi-Antenna Radio Network Simulations

This paper outlines and evaluates a simplified interference model applicable in multi-cell multi-antenna radio network simulations. Based on the path-loss, the model classifies interferers as either strong or weak and the channels of strong interferers together with the channel of the desired signal are accurately modeled using a spatial channel model (SCM). The SCM assures that the spatial signature of the signals is accounted for in the evaluations. The channels of weak interferers are simply characterized by the path-loss and interference is modeled as additive white Gaussian noise (AWGN). The model is verified by means of simulations of a 57 sector OFDM/TDMA network and by comparing results achieved using the simplified model to results from simulations with full interference modeling, i.e., to the case when all interferers are accurately modeled. The verification results demonstrate that the simplified model with at least eight links accurately modeled provides a high modeling accuracy and results are comparable to results achieved with full interference modeling. Moreover, in the employed simulation tool this reduces the simulation time by up to a factor of four. The model may hence be used as a means to speed up simulations of multi-cell multi-antenna radio networks.

Joint capacity and quality evaluation for AMR telephony speech in WCDMA systems

The adaptive multi-rate (AMR) speech codec is the mandatory speech codec for WCDMA systems. The codec supports eight different source rates ranging from 12.2 kbit/s down to 4.75 kbit/s. This paper evaluates different ways of allocating AMR rates to users on the downlink in a WCDMA system. A novel system performance concept is introduced based on a user satisfaction metric that tries to combine the user experience from different speech quality levels as well as events like blocking and dropping. System simulations show that the AMR codec introduces a significant trade-off between capacity and quality for the speech service. By allocating AMR modes based on the system load, the quality and capacity trade-off can be efficiently balanced and high system performance can be achieved for a wide range of offered loads.

A power control and scheduling concept for EGPRS

In existing cellular systems power control is used to save battery and to increase radio network capacity. In packet radio systems scheduling and channel allocation have similar characteristics: the quality (data rate) can be increased at the cost of higher energy use. In this paper a concept combining the functions in order to minimize energy use is presented. Furthermore, an interference area model is introduced. With this model the concept can be extended to minimize interference. The concept can be applied to the design of battery saving and spectrum efficient algorithms.