Enrico Jugl

Force-based load balancing in co-located UMTS/GSM networks

Currently UMTS networks are rolled out to compliment existing GSM networks. As most UMTS mobiles will also support GSM, the question of which system to select for a given service emerges. In order to exploit the differences between radio access technologies, common radio resource management (CRRM) is employed, i.e. common management of the whole radio resources such that the assignment of mobiles to different radio technologies is flexible and considers the specific advantages of each system. The focus of the paper is on intelligent algorithms to decide the balancing of the load between the different radio technologies. We study algorithms for optimum assignment of mobiles to a radio technology during call setup as well as during the call. The decision is based on an intelligent evaluation of various aspects of the radio link. Our algorithm is based on an approach previously employed to balance the load of distributed computing systems.

Radio resource management in HSDPA and HSUPA

This paper discusses the interaction between high speed downlink packet access (HSDPA) and high speed uplink packet access (HSUPA) scheduling algorithms running in the Node B and other resource management algorithms in the radio network controller (RNC), which are still required to satisfy user-perceived quality. We investigate the effect of load sharing with legacy dedicated channel transmission, and discuss load control algorithms suitable for HSDPA and HSUPA packet transmission. The main concepts of resource allocation are discussed together with results obtained from a dynamic system simulator developed by Alcatel-Lucent.

Intelligent management of radio resources in UMTS access networks

The efficient management of scarce radio resources is the heart of any mobile communication system. By the means of power control, load control, and handover, any cellular system can be kept in a stable operational state for all traffic and radio environment conditions. This control mechanism is called radio resource management (RRM). Essentially, RRM algorithms affect the mobile system performance and provide service quality. Therefore, RRM efficiency is a major differentiating factor with regard to the radio access network realizations, especially as the algorithms typically are not standardized. Lucent Technologies has conducted extensive studies to verify the design, evaluate the performance, and prove the excellence of the realized algorithms in the Universal Mobile Telecommunications System (UMTS) access network. This paper describes the theoretical background of WCDMA/UMTS system performance evaluations and shows how this knowledge was turned into a flexible simulation tool. This tool can handle dynamic effects of RRM algorithms in cellular network models by incorporating realistic radio propagation with moving mobile stations generating a mixture of voice and data traffic. The paper further provides examples from a huge series of studies investigating the dynamics of code division multiple access (CDMA) radio systems. These studies and Lucents long experience with developing, deploying, and optimizing CDMA networks will contribute to shortening the introduction phase of the new UMTS radio network technology.

Analysis of analytical mobility models with respect to the applicability for handover modeling and to the estimation of signaling cost

This paper analyzes two analytical mobility models for their suitability to handover modeling and to the estimation of signaling cost. Some insufficiencies of the often employed Hong/Rappaport model are detected. Here, an infinite mean dwell time occurs which is not suitable for performance evaluation of mobile communications systems. Therefore, handover modeling is not possible. To prevent infinite dwell times, an universal condition for the velocity distribution is derived. The biased sampling formula of the velocity distribution fulfills our universal condition. Finally, the consequences of the biased sampling of the velocity for the signaling traffic are discussed for the modified Hong/Rappaport model and a highway model. In contrast to the analytical calculations without consideration of biased sampling, we detect a significant increase of signaling traffic. It is shown that the probability density function of the velocity of the boundary-crossing subscribers is given by the biased sampling formula. Thus, for handover modeling and the exact estimation of signaling traffic the biased sampling formula of the velocity has to be taken into account in analytical calculations in any case.

New techniques for the calculation of the average SIR and the outage probability of the uplink of CDMA systems

New techniques for the calculation of the average signal-to-interference ratio (SIR) and the outage probability of the uplink of a single cell CDMA based mobile communications system are introduced. We show the differences between the often employed lower bound on the average SIR and the exact value of the average SIR. These differences are significant if the variance of the SIR gets higher which will affect the outage probability. A high signal to-noise ratio, a low voice activity factor and a high grade of imperfection of the power control system cause a higher variance of the SIR. These effect is emphasized especially if there is a few number of subscribers. Usually in the literature the capacity of such CDMA based mobile systems is often calculated by employing a lower bound on the average SIR. Generally, our basic approach shows that this is not possible.

Time/wavelength coding for diffuse infrared communication systems with multiple optical carriers

We propose two possibilities to combine multiple optical wavelengths with code division multiple access (CDMA) to achieve asynchronous access in diffuse IR-systems. A serial coding type which combines D-ary wavelength-shift keying with incoherent CDMA and a parallel coding type where the channels are distinguished by time/wavelength-matrices are investigated. We analyze the theoretical performance and show numerical results for different code families.

Downlink beamforming and data rate adaptation applied for packet data transmission over the UMTS dedicated channel

In this paper system level simulation results from the performance evaluation of applicable downlink beamforming concepts for UMTS are presented. For the first time the combination of beamforming and packet data services over UMTS dedicated channels in conjunction with data rate adaptation is investigated. The main focus of this paper is to assess realistic system capacity gains of the different beamforming concepts regarding UMTS specific conditions. Special focus is paid on the comparison of 3/6 sector scenarios with fixed beam switching (FBS) and beam pointing (BP). When applying FBS and BP with 4 antenna elements (4 beams for FBS) a cell throughput gain of about 180...190 % is reached compared to 3 sectors scenario. This gain is coming along with a reduction of the required downlink transmit power dedicated to a specific user. Moreover, due to the lower complexity of the FBS concept and the comparable capacity gain, FBS is preferred to BP

Dwell time modeling for wireless communication systems and problems of the velocity distribution

The distribution of the dwell time, which represents a higher level of abstraction than the use of mobility models, is often required for the performance evaluation of mobile communication systems. This contribution investigates the problem of the dwell time modeling. Using the often employed model for a constant movement, it is shown that a suitable choice of the velocity distribution is very important. Thus, a condition for the probability density function (PDF) of the velocity is derived, which prevents an unbounded mean dwell time. Since an infinite mean dwell time causes some problems for the estimation of the mobility-related signaling traffic, it is important that the mean dwell time is finite. Furthermore, some basic models for the PDF of the travel length of a subscriber within a radio cell are introduced and the relation with realistic mobility patterns are shown.