Jan Christoffersson

Improving SigComp performance through extended operations

This paper demonstrates the efficiency gains achievable for the compression scheme SigComp using extended operations where information from previously sent and received messages is used. The calculations are performed for a call setup using SIP in a typical 3GPP scenario. It is estimated that the transmission time over the air interface can be reduced by approximately 2/3. Also, the performance in terms of compression efficiency can be doubled, compared to using message by message compression with SigComp.

LTE Outdoor & Indoor Interference Assessment Based on UE Measurements

Cell isolation or the inter-cell interference is an important characteristic of radio networks. The cell isolation together with link performance limits the achievable user throughput and the capacity for a 1-reuse link adaptive packet access systems such as LTE. In this paper, cell isolation is measured as geometry factors and assessed through UE measurements in two different networks utilizing different access techniques, LTE and GSM. The use of UE measurements are beneficial in the sense that the mobile position is always known, making it possible to distinguish between indoor and outdoor positions. It is found that the geometry factor is higher indoor than outdoor. The GSM measurements provide better accuracy because of the sparse frequency reuse and more mature mobiles detecting a large set of neighbor cells. These GSM measurements also confirm previous system measurements on commercial traffic in the same area.

Energy Efficiency by Cell Reconfiguration: MIMO to Non-MIMO and 3-Cell Sites to Omni

Altering the network configuration in order to reduce the energy consumption in a WCDMA network is under study in this paper. The baseline configuration is a MIMO enabled network with 3-cell sites. In case there are no MIMO users in a cell, one of the MIMO antennas and the corresponding power amplifier in this cell is turned off. Furthermore, if the user distribution is such that the traffic can be handled by an Omni configuration, the site is re-configured to an Omni site. The transmission powers for the different configurations are assessed through system simulations and fed into a base station energy consumption model, based on the predicted network configuration assuming different loads of fixed bit rate users. It is found that in a low load scenario, the energy savings can be up to 15-25 percent simply by turning off one of the MIMO antennas when the fraction of MIMO enabled users is 25-75 percent. If reconfiguring to Omni cell as well as turning off one MIMO antenna when permitted, the savings can be up to 40 to 50 percent with the same fraction of MIMO users in a low load situation. Savings by reconfiguration to Omni cells when there are no MIMO users in the system gives saving of up to 28 percent in a low load scenario. It is concluded that the proposed techniques has the potential to yield substantial energy savings in low load scenarios without degrading the user performance.

Prediction based energy efficient mobile positioning

Many smartphone applications or services require position information, e.g., location based services including mobile advertisement, mobile social network, etc. In this paper, we propose a prediction based mobile positioning mechanism which utilizes history mobility information in a smartphone. The proposed solution is implemented in an Android phone and has been evaluated in real-life for a period of three months. During the evaluation period the proposed mechanism has reduced energy consumption for positioning with 60% compared to GPS positioning. The accuracy is increased by around 76% compared to network based positioning only. Thus it provides significant benefit for those location-based services which needs longer time usage but less accuracy than GPS positioning.