Publications 2004

Journal articles (1)

J. Kurjenniemi, O. Lehtinen and T. Ristaniemi, “Signaled Step Size for Downlink Power Control of Dedicated Channels in UTRA TDD“, Wireless Personal Communications, vol. 31, no. 3-4, December 2004, pp. 161-180.

This paper discusses downlink inner loop power control of dedicated channels in UTRA TDD. The current UTRA TDD downlink power control is similar to 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 asymmetric step sizes for “power up” and “power down” commands is evaluated in contrast to the conventional symmetric power adjustment.

Since it would be beneficial for the downlink inner loop power control to reach the target SIR as fast as possible, the power control step size based on the difference between the UE measured SIR and target SIR would be the most desirable power adjustment.

Since the effectiveness of this type of an algorithm depends on available signaling bandwidth that is used, a study is carried out to find the tradeoff between the signaling bandwidth and related network performance.

Conference articles (2)

J. Kurjenniemi, J. Leino and M. Rinne, “Analysis of Fast Alpha Switching for Closed Loop Mode 1 Transmit Diversity with High Speed Downlink Packet Access“, Proc. of the IEEE Vehicular Technology Conference, Los Angeles, California, USA, September 26-29, 2004.

We present an analysis of the fast alpha switching (FAS) technique in WCDMA using closed loop (CL) mode 1 transmit diversity and utilizing the high speed physical downlink shared channel (HS-PDSCH) for data service.

When applied on the HS-PDSCH channel, CL mode 1 utilizes the antenna weights used on the associated dedicated physical channel (DPCH). Therefore, when the terminal is in soft handover (SHO) in the DPCH, i.e., connected to more than one sector, the antenna weight, which is optimized for all sectors in the SHO, is hardly optimal for the HS-PDSCH, which is always received from a single sector.

In the FAS technique, antenna weight calculation is based on the received pilot from the HS-PDSCH sector when the HS-PDSCH is in use and otherwise calculation is based on the pilots of all sectors in SHO. At first sight, this seems a desirable feature, but several more factors have to be considered before drawing any conclusions.

The FAS technique is affected by the weight feedback delay, thus the applied weight is not always optimal for the HS-PDSCH. Moreover, the SHO probability is important for the analysis, since the gain can be achieved only when the terminals are in SHO. Therefore, dynamic system simulations are necessary to study what are the expected gains from the FAS technique in realistic scenarios.

J. Kurjenniemi, J. Äijänen, M. Rinne and T. Ristaniemi, “UTRA TDD Intra-Frequency Handover Performance“, Proc. of the Global Mobile Congress, Shanghai, China, October 11-13, 2004, pp. 227-231.

In this paper intra-frequency handover in UTRA TDD network is addressed. A simple WCDMA handover, tailored to a TDD operation, is considered. This gives rise to careful setting of different handover parameters, and in here we now give an emphasis to the effects of handover delays.

This is crucial in determining the robustness of a certain parameter selection in reality when e.g. signaling and measurements naturally takes some time before certain RRM action can be executed. In addition to handover delay we pay attention to a setting of handover hysteresis and effect of handover measurement error to system capacity.

A dynamic system level simulator, where all the relevant radio resource management procedures and their interactions are modeled, is used for this purpose.