Ville Haikola

HSDPA MIMO System Performance in Macro Cell Network

This paper studies the performance of dual-stream transmit antenna array (D-TxAA) technique in a macro cell high speed downlink packet access (HSDPA) network. 3rd generation partnership project (3GPP) responsible of the standardization of 3G systems selected D-TxAA as the multiple input-multiple output (MIMO) scheme for HSDPA in 3GPP specification Release 7. MIMO transmission doubles the theoretical peak data rate of HSDPA from 14.4 Mbps to 28.8 Mbps. However, successful reception of dual stream MIMO transmissions requires good signal conditions. Thus, employing MIMO is generally considered beneficial only in small cells due to the fact that in a macro cell network the channel conditions are seldom favourable to MIMO usage because the distances may be large between the base station and the mobile terminals. The objective of this paper is to study the actual impact of D-TxAA MIMO technique to user and system throughput in a macro cell HSDPA network. Using dynamic system simulations the performance of MIMO transmission is compared to a scenario where only conventional receive diversity is employed at the user entities.

System Level Performance of Multimedia Broadcast Multicast Service (MBMS) with Macro Diversity

The aim of this paper is to evaluate the system level performance of multimedia broadcast multicast service (MBMS) in WCDMA networks. To enhance coverage and data rates of MBMS users, two macro diversity concepts were introduced in 3GPP release 6: soft and selective combining. Prior work on the evaluation of MBMS with macro diversity schemes has been restricted to link level studies or to very limited scenarios in system level studies. This paper examines the concepts in more detail with dynamic system level tool in which e.g. mobility of users and interactions of the radio resource management functionalities are explicitly taken into account. The evaluation of combining set size and data rates with different thresholds and delays in the combining procedures are especially emphasized. Considering point-to-multipoint (p-t-m) mode of MBMS, the studies indicated clear performance improvements to be gained with macro diversity. In addition, the impact of delays in combining set update procedures was observed to be rather small.

Performance Enhancement of Multimedia Broadcast Multicast Service (MBMS) with Receive Diversity

The aim of this paper is to evaluate the effect of receive diversity on multimedia broadcast multicast service (MBMS) performance in wideband code division multiple access (WCDMA) networks. In addition to time diversity provided by long interleaving and receive diversity provided by multiple receive antennas, 3GPP release 6 specifications for MBMS introduce two macro diversity schemes: soft and selective combining. Diversity techniques are introduced in order to improve the MBMS performance. Improvements help especially the cell edge MBMS users who suffer most from the fading channel conditions. As receive diversity is one of the most efficient diversity techniques this paper examines the system level performance of MBMS point-to-multipoint (p-t-m) mode with receive diversity together with and without macro diversity schemes. These concepts are studied with dynamic system level tool in which e.g. mobility of users and interactions of the radio resource management functionalities are explicitly taken into account. Our studies indicate that the receive diversity brings significant gains to the MBMS performance. Receive diversity together with macro diversity schemes improves the performance even more.

HSDPA Performance with Dual Stream MIMO in a Combined Macro-Femto Cell Network

3rd Generation Partnership Project (3GPP) responsible of the standardization of 3G systems selected dual stream Transmit Antenna Array (D-TxAA) as the Multiple Input - Multiple Output (MIMO) scheme for High Speed Downlink Packet Access (HSDPA) in 3GPP specification Release 7. MIMO doubles the theoretical peak data rate of HSDPA from 14.4 Mbps to 28.8 Mbps. However, successful reception of dual stream MIMO transmissions requires good signal conditions. Very high signal to noise ratios can be achieved with the use of femto base stations in small isolated areas with insufficient or no macro cell coverage. This paper studies the effect of D-TxAA concept in a combined single frequency macro and femto cell scenario with Linear Minimum Mean Squared Error (LMMSE) chip-level equalizer receivers used at user entities (UE). The impact of receivers employing MIMO transmission mode is analyzed as a function of indoor user penetration using fully dynamic system level simulations.

Open-loop MIMO extensions for HSDPA with practical constraints

In this paper, we investigate three different open-loop multi antenna schemes and compare their performance to the traditional receive diversity in high speed downlink packet access (HSDPA) system, which is a packet enhancement to the third generation wideband code division multiple access (WCDMA) mobile communication system. The studied schemes are per antenna rate control (PARC), space time transmit diversity (SITD) and matrix modulation (MaMo) each with 2times2 antenna configuration. In this study a chip equalizer based receiver is used, because the optimal receiver is prohibitively complex for practical implementation. The link throughput results show that multiple-input multiple-output (MIMO) schemes outperform the traditional receive diversity in low delay spread channels especially, if up-to-date and error free link adaptation feedback is available. However, with practical constraints on the link adaptation feedback , geometry distribution and delay spread, the receive diversity performs almost as well as the studied MIMO schemes

Adaptive filtering for fading channel estimation in WCDMA downlink

In order to perform coherent demodulation in fading channel conditions, channel phase and amplitude estimation is necessary. In a WCDMA downlink, the common pilot code channel is used for channel estimation in order to facilitate multipath diversity combining. The quality of the channel estimates may be improved by averaging or filtering over several pilot symbols. However, the optimal form and bandwidth of the estimation filter depend on the channel fading statistics and signal-to-interference ratio. In this paper, we investigate pilot aided channel estimation through adaptive filtering. Thus, near optimum channel estimates are obtained with different fading channel speeds and frequency offsets.

Multimedia Broadcast Multicast Service Performance and its Enhancements in WCDMA Networks

Multimedia Broadcast Multicast Service (MBMS) in Wideband Code Division Multiple Access (WCDMA) networks is used to transmit information from one source to vast amount of recipients. The MBMS technique eases the load of the network and therefore allows network to serve more subscribers. The very aim of this study is to evaluate the performance of Release 6 MBMS and its performance enhancements in WCDMA networks. Special attention will be focused on macro and receive diversity which are considered in addition to time diversity provided by long interleaving as enhancements on MBMS performance. 3GPP Release 6 specifications for MBMS introduce two macro diversity schemes: soft and selective combining. The effect of those combining scheme concepts together with and without receive diversity provided by multiple receive antennas are examined. Also, a concept closely related to the receive diversity called Rx-switching i.e., turning the another receive antenna off in good channel situations for power saving purposes is studied. The system level performance of MBMS point-to-multipoint (p-t-m) mode is evaluated with dynamic system level tool in which e.g., mobility of users and interactions of the radio resource management functionalities are explicitly taken into account. Our studies indicate that macro diversity brings significant gains to the MBMS performance. Receive diversity together with macro diversity schemes improves the performance even more and therefore enhances the cell throughput that MBMS can offer. Furthermore, based on the findings of this study it seems that 2Rx Rake receiver can operate with a single antenna significant amount of time without sacrificing desired coverage and thus provide clear power saving opportunities.

Advanced high speed packet access receiver for WCDMA multicode transmissions with high-order modulation

High speed downlink packet access (HSDPA) is underway, supporting the evolution of third-generation systems to meet the rapidly developing needs for high data rates. High order modulation has been proposed for the adaptive modulation and coding sets to increase the transmission data rate for users with high signal-to-noise-plus-interference ratio. However, high order modulation is significantly less robust to noise, interference, and channel estimation errors. An advanced HSDPA receiver using equalized parallel interference cancellation is presented to suppress the interference. Link level simulations for WCDMA multicode transmissions in frequency-selective Rayleigh fading channels indicate significant performance advantages over conventional RAKE receiver with only 2-3 times complexity increase.

High speed packet access with parallel interference cancellation and high-order modulation for coded FDD CDMA communications

The high-order modulation increases the transmission data rate, but apparently is more sensitive to amplitude and phase errors. For CDMA downlink transmissions, the common pilot channel reserves 10% of the total transmission power at base stations with the result of perfect channel estimation at mobile stations. Therefore the multiple access interference and co-channel interference can be successfully suppressed by parallel interference cancellation (PIC). Motivated by this, a high speed packet access (HSPA) scheme using PIC and flexible high-order modulation is proposed in this paper for frequency division duplex downlink CDMA communications. The proposed HSPA scheme has been evaluated by system level simulations in frequency selective Rayleigh fading channel with soft-decision channel decoding. The numerical results showed that the target coded bit error rate could be achieved by the HSPA receiver using 16-QAM with reasonable increase in signal-to-noise ratios, but the data rates can be doubled compared with the RAKE receiver using QPSK modulation.

HSDPA performance with parallel interference cancellation

We investigate an advanced receiver technique called multistage parallel interference cancellation applied to high speed downlink packet access (HSDPA), which is a packet enhancement to the third generation wideband code division multiple access (WCDMA) mobile communication system. The advanced receiver packet error rate and throughput performance is compared to conventional rake receiver with link level simulations in single antenna case, and the results show that considerable gain is possible by using the advanced receiver in multipath fading channels, where the rake has already reached error floor.