Harri Posti

Capacity reduction of WCDMA downlink in the presence of interference from adjacent narrow-band system

One of the main challenges when implementing the future mobile multimedia networks is the cost-effective network evolution from second- to third-generation systems. This evolution path may include the use of different technologies at the same frequency band. The performance of the wide-band code-division multiple-access (WCDMA) downlink is studied in the case when there are narrow-band (NB) interference sources at the adjacent frequencies. A simple, analytical method to calculate the downlink capacity reduction of the WCDMA macrocell in this case is presented. The analysis takes into account different downlink interference mechanisms: wide-band noise from the transmitter as well as adjacent channel interference, intermodulation, and cross-modulation originating in the mobile receiver. The effect of each interference component to the capacity of the WCDMA macrocellular network has been evaluated with numerical examples. The analysis shows that capacity per cell is sensitive to the cell size, and therefore very careful network planning is needed in order to operate the WCDMA networks efficiently. The results of this paper can be utilized when implementing the WCDMA system to the same band with existing narrow-band systems, for instance, with the PCS 1900 band in United States and GSM 1800 band in Europe.

Wireless Internet — IMT-2000/Wireless LAN interworking

Ongoing standardization effort on 3G cellular systems in 3GPP (UMTS) is based on GPRS core network and promises a global standard for systems capable of offering ubiquitous access to Internet for mobile users. Considered radio access systems (FDD CDMA, TDD CDMA, and EDGE) are optimized for robust mobile use. However, there are alternative relatively high-rate radio interfaces being standardized for WLAN (IEEE 802.11 and HIPERLAN/2) which are capable of delivering significantly higher data rates to static or semi-static terminals with much less overhead. Also WPANs (BLUETOOTH, IEEE 802.15), which will be present in virtually every mobile handset in the near future, are offering low cost and considerable access data rate and thus are very attractive for interworking scenarios. The prospect of using these interfaces as alternative RANs in the modular UMTS architecture is very promising. Additionally, the recent inclusion of MIP in the UMTS R99 standard opens the way for IP-level interfacing to the core network. This article offers an overview into WLAN-Cellular interworking. A brief overview of GPRS, UMTS cellular architectures and relevant WLAN standards is given. Possible interworking architectures are presented.

WCDMA Downlink Coverage Reduction Due to Adjacent Channel Interference

This paper determines the coverage reduction of the Wideband CDMA (WCDMA) downlink in the case of interference, due to adjacent narrowband system. The coverage reduction has been evaluated in terms of blocking area around the interfering base station. The analysis takes into account different interference mechanisms and their individual effects to the coverage. The interference mechanisms which have been considered here are the out-of-band emissions of the base station transmitter, the adjacent channel interference due to non-ideal sideband filtering, the intermodulation and the crossmodulation. The coverage effects in realistic network environment have been computed by using accurate ray-tracing propagation models designed for the path loss calculation in the urban environment. In the numerical examples, the effect of GSM interference has been demonstrated, but the method can be utilized with other narrowband systems as well. The results can be utilized in radio system design, radio network planning (RNP) and the frequency allocation of the WCDMA systems.