T. Ojanpera’s research while affiliated with Nokia and other places

Mobile communication has expanded the basic need for humans to communicate to “from anywhere at any time,” which was unthinkable only 25 years ago. It has touched almost every person, rich or poor, child or adult, around the globe. Increasingly, new developments in wireless data and mobile internet are augmenting the voice communication experience with much richer multimedia content consisting of text, video, and images. In not too distant a future, wireless data connectivity between the machines and sensors is destined to reshape the environment we live in and impact our lives in ways that we can hardly imagine. The emerging economies are already skipping legacy technologies, going for the next generation, and will be the hotbed of some of the innovations that would find their way to the affluent economies.

Broadband wireless access (BWA) is moving into IP era. New open interoperability standards, HiperAccess and IEEE802.16, optimized for IP traffic are being developed enabling low cost, mass market systems. In this paper BWA standardization, system design and regulation are discussed

Considering the importance of DS-CDMA for the third generation mobile communication systems, evaluating the performance of DS-CDMA systems is crucial. Several techniques have been developed to evaluate DS-CDMA system performance, each with its (dis)advantages. In this paper a novel technique is presented, which is accurate and simple. Furthermore, a range of scenarios can be captured in one formula

This paper presents the performance of groupwise successive interference cancellation (GSIC) in a DS-CDMA system with multiple data rates (multirate). The performance is evaluated both in AWGN and Rayleigh fading channels. In the GSIC scheme users with the same data rate are grouped and detected, using either a matched filter or a parallel interference cancellation (PIC) receiver, interference between the groups is cancelled in a successive order. The results show that in a multirate system the GSIC yields a better performance than the PIC receiver. Further a delay error of 0.1 T_c is found to be tolerable

This paper presents the impact of timing error on the performance of multirate direct sequence code division multiple access (DS-CDMA) systems based on variable spreading factor (VSF) using multiuser detection techniques such as the parallel interference cancellation (PIC) detector. The performance is evaluated for a single-rate and a three-rate system using Monte-Carlo simulation in the additive white Gaussian noise (AWGN) channel without multipath fading. The bit error probability (BEP) of the matched filter (MF) and the PIC detector with and without timing errors are compared

This paper presents the results of a groupwise weighted parallel interference cancellation (GW-PIC) receiver in a multirate MPG (multiple processing gain) DS-CDMA environment. The BER performance of this receiver in AWGN channels is better than the BER performance of the ordinary PIC receiver. Applying weights in a groupwise way to a PIC receiver in Rayleigh faded channels does not result in a better performance than the ordinary PIC receiver. A delay estimation error of one-tenth of a chip time is found to be tolerable

Summary form only given. Facing the challenge of tomorrow's information society we can already witness today the birth of mobile multimedia services such as speech, video, and data. GSM, the most widespread mobile wireless system today with over 100 million users worldwide, will offer rich possibilities to provide wideband wireless multimedia services. The emergence of high speed circuit switched services (HSCSD) with data rates up to 56 kbps, general packet radio service (GPRS) with data rates up to 115 kbps, and universal mobile telecommunications system (UMTS) based on wideband CDMA as part of the IMT-2000 family of systems with data rates up to 2 Mbps, will provide the end users of the GSM system with freedom of choice to access a wide range of services with revolutionary characteristics. And all this is based on evolution of the GSM core network platform supporting any kind of radio access. Only the fundamental laws of physics will put limits to the evolution of wireless communications. These will be examined in this paper, and based on this, future projections of the future of wireless communications will be presented

For a code division multiple access (CDMA) model we compare the bit error probability (BEP) without interference cancellation, with the BEP after interference cancellation. Using large deviation theory we calculate for both cases the exponential rates, defined as the limit of log(BEP)/n, for the processing gain n→∞. We show that the exponential rate with interference cancellation is larger than without interference cancellation, which demonstrates that the BEP, after interference cancellation is considerably smaller than before interference cancellation. Furthermore, we give the second order asymptotics of the BEP with interference cancellation for the case with 3 or more users. Finally, we compute the second order asymptotics of the BEP after interference cancellation for the case of 3 users

In this paper, the performance of the hard decision (HD) parallel interference cancellation (PIC) detector (HD-PIC) is studied in a multirate direct-sequence code division multiple access (DS-CDMA) system. The performance is measured in terms of bit error rate, in an additive white Gaussian noise (AWGN) channel under the impact of imperfect delay estimation and the near-far conditions. The performance results are evaluated for a single-rate and a three-rate system. Monte-Carlo computer simulations have been used to generate the results

An overview of third-generation wireless personal communications is presented, and the challenges to meet its demands are examined. At the ITU level, the third generation is known as IMT-2000. In Europe, the third generation of wireless personal communications is known as UMTS. Special attention has been paid in giving a brief description of the research and development, standardization, and regulatory activities. The UMTS terrestrial radio access (UTRA) concept is presented. The different ACTS projects involved in making UMTS a success are introduced