Kjell Larsson

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.

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.

Outer-loop power control based on hybrid ARQ protocol for WCDMA enhanced uplink

In this article, a node B-located outer-loop power control (OLPC) algorithm for WCDMA enhanced uplink (E-UL) based on the number of hybrid automatic repeat request (HARQ) transmission attempts is introduced. The proposed OLPC algorithm can take full advantage of the HARQ protocol since its operation is not affected by the signaling delay between node B and radio network controller (RNC). However, when the Node B-located OLPC is considered in a soft handover (SHO) situation, the Carrier-to-interference Ratio (CIR)-drift problem that emerges compromises the OLPC performance, and some mechanism to compensate for the CIR-drift problem is required. Both an aggressively tuned anti-windup function and an retransmission sequence number (RSN)-based functionality handle this problem. The proposed Node B-located OLPC is evaluated for 2 ms and 10 ms transmission time intervals (TTIs). It is observed that the Node B-located OLPC provides gains in terms of lower CIR and is more beneficial for 2 ms TTI, since the RNC signaling delay has rather severe impact in a shorter round trip time (RTT).

RNC-Located Filtering-Based OLPC Solution for E-UL

In this article, systemic aspects related to the outer-loop power control (OLPC) for enhanced uplink are investigated. A feasibility study of a filter-based OLPC algorithm located in the radio network controller (RNC) is driven. The RNC-located filtering-based OLPC solution presents interesting performance results in the evaluated scenarios. The proposed filter solution presents carrier-to-interference ratio (CIR) results performance similar to the standard-jump OLPC algorithm. It is worthy to notice that the performance results of the filtering-based OLPC solution provide a first insight on the applicability of this mechanism as an alternative to the standard jump algorithm

Real Life LTE In-Building Deployment Demonstrating Multi-Cell Capacity

In Building Solutions (IBS) are a well-established approach to providing indoor cellular coverage. The increasing wireless mobile broadband traffic and the fact that most broadband data is consumed indoors increases the interest to understand the IBS capacity potential. For a given available spectrum, a straightforward capacity solution is cell-splitting. In this paper, measurement results from a full-scale real life deployment with a Long Term Evolution (LTE) IBS solution are presented. Two cell-splitting scenarios in a three floor, 7500 m2 office building have been tested, both by collecting traffic and radio statistics from actual users, as well as performing controlled walk-tests in the building. It is found that cell splitting is an excellent way to enable increased indoor capacity. The isolation between floors as well as within a floor is higher than in a typical macro scenario. High throughput and fraction of spatial multiplexing is maintained even with artificially generated 100% activity. The capacity is assessed to around 2 kbps/m2/MHz with a 6 cell solution.

Node B-Located OLPC for Enhanced Uplink

In this article, systemic aspects related to the outer-loop power control (OLPC) for WCDMA enhanced uplink are investigated. A Node B-located OLPC algorithm based on the number of hybrid automatic repeat request (HARQ) transmission attempts is introduced. Traditionally, the OLPC functionality is located in the radio network controller (RNC) and operates on the radio link control (RLC) block error rate (BLER) striving to maintain the pre-established QoS requirement. In the enhanced uplink (E-UL), the utilization of a correctly working Node B HARQ operation diminishes the RLC BLER remarkably. The proposed Node B-located OLPC can take full advantage of the number of HARQ retransmissions since its operation is not affected by the signaling exchanged between Node B and RNC entities over the Iub interface. However, when the Node B-located OLPC is considered in a soft handover (SHO) situation, the CIR-drift problem that emerges compromises the OLPC performance, and some mechanism to compensate for the CIR-drift problem is required. Both an aggressively tuned anti-windup function and an retransmission sequence number (RSN)-based functionality handle this problem. It is observed that the Node B-located OLPC provides gains in terms of lower CIR since there is no delay due to the signaling exchange between RNC and Node B network entities