Publications 2003

J. Kurjenniemi, J. Leino, Y. Kaipainen and T. Ristaniemi, “Closed Loop Mode 1 Transmit Diversity with High Speed Downlink Packet Access“, Proc. of the IEEE International Conference on Communication Technology, Beijing, China, 9-11 April, 2003, pp. 757-761.

In this paper we consider the performance of a closed loop mode 1 transmit diversity in WCDMA network when high speed downlink packet access (HSDPA) scheme is used.

Motivation for the use of multiple antennas arises from the expected gains in the performance of a wireless link. In closed loop mode 1 technique base station uses a suitable weight, which corresponds to phase adjustment, for its second transmission antenna according to UE’s feedback commands.

The study of the effects of it to the system’s performance in a dynamic environment is extremely crucial due to the fact that phase adjustment may lead to destructive combining or received phases due to mobility and feedback errors and, as a consequence, might even lead to performance losses rather than gains for the system.

In this paper we study the effect of mobility, feedback errors and feedback delays to the system performance and draw conclusions about the achieved capacity gains/losses.

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J. Kurjenniemi, O. Lehtinen and T. Ristaniemi, “Improving UTRA TDD Downlink Power Control With Asymmetrical Steps“, Proc. of the IEEE Vehicular Technology Conference, Jeju, Korea, April 21-24, 2003.

This paper discusses downlink power control of dedicated channels in UTRA TDD. The current UTRA TDD downlink power control is similar to the one in UTRA FDD mode, that comprises of closed inner loop and quality based outer loop.

However, due to the time division feature and associated flexibility with asymmetry of TDD, the inner loop can not react as fast as in FDD and it is affected by rapid changes in environment.

Therefore, the effect of the inner loop algorithm to the performance of UTRA TDD network is studied in this paper. Especially, the use of asymmetrical step sizes in power adjustment is proposed, and the achieved gains are highlighted by the means of dynamic system simulations.

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J. Kurjenniemi and O. Lehtinen, “UTRA TDD Dynamic Channel Allocation in Uplink with Slow Reallocation“, Proc. of the IEEE Vehicular Technology Conference, Jeju, Korea, April 21-24, 2003.

Efficient dynamic channel allocation (DCA) algorithms are needed to take full advantage of flexibility and dynamic nature of TDD operation. DCA algorithms can be divided in two parts where slow DCA allocates resources to cells and fast DCA to bearer services.

This paper discusses uplink dynamic channel allocation in UTRA TDD with slow reallocation. The TDD operation has traditionally exploited the possibility of DCA functions to avoid or minimise the interference and improve the system capacity. For UTRA TDD the promise of advanced receivers alleviates the intra cell interference, but this emphasises the importance of minimising the interference between different cells.

There are several methods that can be used to aid the channel allocation process, but they all have inherent limitations. A model for analysis of protocol and measurement errors impact is proposed.

These studies are based on dynamic system simulations that are carried out to find out how the different elements in the DCA process impact the UL system capacity. Effect of random and interference based channel allocation with and without slow DCA information is studied in presence of signalling delays and measurement errors.

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J. Kurjenniemi and O. Lehtinen, “Comparison of Dynamic Channel Allocation Schemes in Downlink in UTRA TDD“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications, Beijing, China, September 7-10, 2003.

Dynamic channel allocation (DCA) has been seen as a promising method for improving quality and capacity in cellular networks.

In theoretical studies very significant quality and capacity improvements has been achieved. However, in real systems DCA performance is limited by several factors so theoretical limits might not be reached.

To exploit full possibilities of TDD system efficient, DCA algorithms are needed to guarantee quality of service in rapidly changing channel conditions and in mixed traffic scenarios.

In this paper UTRA TDD down-link system capacity is analyzed with different DCA schemes. Dynamic system simulations are carried out to find out how the different elements in the DCA process impact the downlink system capacity. Effect of random and downlink transmission power based channel allocation with and without slow DCA information is studied in presence of signaling delays.

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J. Kurjenniemi, J. Äijänen and O. Lehtinen, “Frame Configuration Impact to the Performance of UTRA TDD System“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications, Beijing, China, September 7-10, 2003.

In this paper we consider the performance of a UTRA TDD system with various slot configurations. UTRA TDD supports flexible and dynamic channel allocations thus it can he configured to different service needs.

Uplink and downlink transmissions have different characteristics and in this study we are concentrating on the requirements for symmetrical services in dedicated channels. Effect of number of beacon channels per radio frame and effect of different uplink and downlink partitioning to TDD system capacity are analyzed with dynamic system level simulator.

Although this study is limited to circuit-switched data service these findings can be used as a starting point when building up mixed traffic scenarios with asymmetrical services.