Bo Göransson

A Wideband Spatial Channel Model for System-Wide Simulations

A wideband space-time channel model is defined, which captures the multiple dependencies and variability in multicell system-wide operating environments. The model provides a unified treatment of spatial and temporal parameters, giving their statistical description and dependencies across a large geographical area for three outdoor environments pertinent to third-generation cellular system simulations. Parameter values are drawn from a broad base of recently published wideband and multiple-antenna measurements. A methodology is given to generate fast-fading coefficients between a base station and a mobile user based on the summation of directional plane waves derived from the statistics of the space-time parameters. Extensions to the baseline channel model, such as polarized antennas, are given to provide a greater variety of spatial environments. Despite its comprehensive nature, the models implementation complexity is reasonable so it can be used in simulating large-scale systems. Output statistics and capacities are used to illustrate the main characteristics of the model

Transmit diversity in WCDMA: link and system level results

In the current WCDMA standard, support for transmit diversity is provided in the down-link to combat fading and changing interference situations. The base station (node B) is equipped with two transmit antennas, while the terminal (user equipment, UE) uses only a single antenna. This arrangement is advantageous compared to receive diversity as it removes the need for two antennas in the terminal. This paper describes the various transmit diversity schemes in WCDMA and gives simulation results, both at the link and system levels. It is found that transmit diversity can greatly improve the system capacity.

High Speed Packet Access Evolution - Concept and Technologies

In this paper we present the main concepts of high speed packet access evolution currently being standardized in 3GPP. In general HSPA evolution consists of introduction of MIMO, higher order modulation, and protocol optimizations and optimizations for voice over IP. We describe these improvements in detail and show that HSPA Evolution can reach performance comparable to those of long term evolution of UMTS terrestrial radio access network in a 5 MHz deployment.

Effect of transmitter and receiver impairments on the performance of MIMO in HSDPA

In this contribution we study the impact of transmitter and receiver impairments on the throughput for MIMO and 64 QAM transmissions in an evolved HSDPA system. A simple additive white Gaussian noise model is used to model impairments in the transmitter and receiver chain. The investigation is performed through computer simulations both on link and system level. It is found that the impact from transmitter and receiver distortions is rather small for MIMO with 16 QAM while the impact when 64 QAM is used is more pronounced.

Advanced antenna systems for WCDMA: link and system level results

This contribution presents some link and system level simulation results obtained by a WCDMA base station equipped with an adaptive antenna system. The results show that the performance gain obtained by an advanced antenna system could be substantial compared to an ordinary sector covering system. The link simulations show that for a given SIR target in a single cell system, the capacity is increased considerably compared to a conventional single sector covering antenna system. It is also shown that the difference between the different adaptive antenna algorithms is marginal. The system level simulations have shown that the capacity performance is basically proportional to the number of orthogonal beams used in the base station. In cases where the conventional three sector reference system is not truly interference limited, the performance gain can be even higher. The system simulations have also shown that using more beam positions than those defining the set of orthogonal fixed beams slightly improves the performance. However the number of beam positions can be kept relatively small, in the order of twice the number of orthogonal beams, without significant loss.

Adaptive antennas in WCDMA systems-link level simulation results based on typical user scenarios

This contribution presents some simulation results obtained by a WCDMA base station equipped with an adaptive antenna system. The results show that the performance gain obtained by an advanced antenna system could be substantial compared to an ordinary sector covering system. Migrating some existing sites/sectors to adaptive antenna systems can be seen as one attractive solution that increases capacity in a coverage area without condensing the system by building additional cell sites. To find out where this grow-on-site migration strategy is most beneficiary, it is important to evaluate the systems by taking typical user scenarios into account. The user scenarios includes spatially distribution of users as well as the expected user behavior related to the actual application (or user data rate). It has been shown that the gains using adaptive antennas for the investigated scenarios of non-uniformly distributed mixed service users are substantial.

Evolution of WCDMA high speed packet access and broadcast services

This paper addresses the latest approaches for improving the data rates and spectral efficiency of the high speed packet access (HSPA) mode of wideband CDMA (WCDMA). The improvements are due to advances in modulation techniques, interference suppression, and broadcast channel reception relative to previously standardized approaches. The new modulation techniques include 2times2 MIMO and 64QAM on the downlink, and 16QAM on the uplink. Interference suppression has been augmented to more accurately model multiple sources of interference. Broadcast channel reception has been restructured for the case of multimedia services. A single frequency network option has been added to allow for macro-diversity to enable comprehensive coverage with interference suppression. We discuss all these advances and evaluate the respective performance impacts based on system and/or link simulations.

A Simplified Approach to Applying the 3GPP Spatial Channel Model

This paper reports on a set of channel models that have been proposed for the evaluation of system concepts for the long-term evolution of third generation mobile communications systems. Conflicting requirements between simplicity of implementation and accuracy in reproducing the radio channel are presented, and the resulting modeling choices are discussed. The channel models have been derived by combining a spatial channel model with several different antenna arrangements that are envisioned to be typical for the systems in question. These antenna arrangements include both spatial separation of elements and polarization. The channel models are supplied as tapped delay lines with correlation parameters for simulating full MIMO channels of size up to 4times4

Downlink capacity comparison between different smart antenna concepts in a mixed service W-CDMA system

The capacity of W-CDMA systems in which base stations are equipped with adaptive antennas (AA) is investigated in mixed service scenarios. The simulations show that generally, a threefold downlink (DL) capacity increase can be gained by employing a fixed or steered beam antenna system. For some scenarios, DL capacity gains of 4 to 6 times can be achieved. Further, a DL capacity comparison between the steered beam concept and the fixed (multi) beam AA concept is presented.

Interference distributions in mixed service WCDMA systems-opportunities for advanced antenna systems

We present spatial downlink power distributions in a WCDMA-FDD system. Several scenarios of user distributions have been studied in mixed service environments where the results have been obtained by system level simulations. The investigated scenarios include concentrated (hot-spot) and distributed high data rate user scenarios. The simulated traffic types cover speech, streaming and Web services of different data rates. The aim of this contribution is to highlight the opportunities of advanced antenna systems in mixed service environments of WCDMA networks.