Showing papers by "Preben Mogensen published in 2006"

Performance of Downlink Frequency Domain Packet Scheduling for the UTRAN Long Term Evolution

Abstract: In this paper we investigate the potential of downlink frequency domain packet scheduling (FDPS) for the 3GPP UTRAN long-term evolution. Utilizing frequency-domain channel quality reports, the scheduler flexibly multiplexes users on different portions of the system bandwidth. Compared to frequency-blind, but time-opportunistic scheduling, FDPS shows gains in both average system capacity and cell-edge data rates on the order of 40%. However, the FDPS performance is shown to depend significantly on the frequency-domain scheduling resolution as well as the accuracy of the channel state reports. Assuming Typical Urban channel profile, studies show that the scheduling resolution should preferably be as low as 375 kHz to yield significant FDPS gain with two-branch receive diversity and in 20 MHz. Further, to have convincing FDPS gain the std. of error of radio state reports needs to be kept within 1.5-2 dB.

Method, apparatus and computer program to dynamically adjust segmentation at a protocol layer, such as at the medium access control (MAC) layer

Abstract: In one exemplary aspect thereof the invention provides a method that operates to receive information through at least one input of a protocol layer packet segmentation unit and to dynamically vary packet segment size in accordance with the received information prior to transmission to a receiver. The information received through the at least one input may include information related to channel quality for a channel through which packet data are transmitted to the receiver. The information received through the at least one input may also be or may include information received from at least one of a higher protocol layer or a lower protocol layer.

Baseline E-UTRA Downlink Spectral Efficiency Evaluation

Abstract: This paper evaluates spectral efficiency performance of the 3GPP Evolved UTRA (E-UTRA) downlink with baseline settings. A detailed link level tool has been developed including the majority of 3GPP E-UTRA link chain processing modules such as time-domain link adaptation and LI HARQ. Since MIMO is an integral part of the new system, we include four basic multiple antenna configurations in the analysis, namely the SISO, 1x2 SIMO, 2x2 SFC and 2x2 BLAST schemes. Since the BLAST is very sensitive to channel estimation error in cell edge, a case denoted as adapMIMO is considered as well, where the SFC is taken as a backup for the BLAST in cell edge. The system bandwidth is fixed at 20 MHz and a Typical Urban channel model is assumed for both macrocell and microcell evaluations. Simulation results show that in macrocell scenario, the spectral efficiency performance gain of SIMO over SISO is up to 54%, while SFC shows an additional gain of 14% over SIMO. Although the adapMIMO scheme has similar performance as SFC in the macrocellular case, it produces about 30% spectral efficiency gain in the microcell scenario.

Overview of QoS options for HSDPA

Abstract: The functional split between the centralized radio network controller and the base station (Node-B) presents new challenges and opportunities for implementing QoS control for HSDPA. In this article we present different options for implementing QoS over HSDPA ranging from quality-based HSDPA access control algorithms to QoS-aware Node-B packet schedulers. The article concludes with network performance results for different services over HSDPA.

Apparatus, method and computer program product providing closed loop transmit antenna operation for systems using multiple antennas

Abstract: A method includes determining weights corresponding to each of a plurality of antennas used to transmit data signals, each weight suitable to modify a corresponding one of the data signals prior to transmission using a corresponding one of the antennas; and transmitting information corresponding to at least one of the weights, the information allowing at least the at least one weight to be determined. Another method includes receiving information corresponding to at least one of a plurality of weights, the plurality of weights corresponding to a plurality of first antennas used to transmit first data signals, where each weight was used to modify a corresponding one of the first data signals prior to transmission using a corresponding one of the first antennas; using the received information, determining the plurality of weights corresponding to the plurality of first antennas; and using at least the plurality of weights; and decoding second data signals received using a plurality of second antennas to create at least one output signal.

QoS Considerations for HSDPA and Performance Results for Different Services

Abstract: The functional split between the centralized radio network controller (RNC) and the base station (node-B) presents new challenges and opportunities for implementing QoS control for HSDPA. In this paper we present different options for implementing QoS over HSDPA, and we focus particularly on the shared responsibility between the QoS aware algorithms at the RNC and the node-B. Different strategies for QoS aware node-B packet schedulers are discussed. The paper is concluded with network performance results for different services over HSDPA, ranging from simple best effort traffic, to constant bit rate streaming, and voice over IP. For these services we show capacity gains of up to 40% from using QoS-aware packet scheduling.

Subjective evaluation of packet service performance in UMTS and heterogeneous networks

Abstract: Quality of Service in mobile telecommunication systems is usually identified by some basic performance metrics such as delay, throughput and jitter However, the main impact of service quality is on the end user, and as such a detailed study of service performance should involve the end user In this paper, such an approach is taken where subjective performance evaluation is undertaken for web browsing and video streaming services in Universal Mobile Telecommunication System (UMTS) and a heterogeneous network comprised of UMTS and Wireless LAN (WLAN)Using a real-time network emulation testbed, users rated the perceived quality of the services under different network conditions The users' ratings are analyzed and the results showed clear trends with very few outliers The objective and subjective measures also were found to be in line except for one case where a higher layer effect influenced the users' perception

Tackling MIMO-OFDMA Feedback Load Through Feedback Encoding

Abstract: In an FDD MIMO-OFDMA system instantaneous downlink channel knowledge cannot be obtained from uplink pilot signalling, but has to be fed back from the receiver. To exploit tx diversity and tx antenna array gain one tx antenna weight-set is ideally fed back per OFDMA subcarrier. Usually the uplink bandwidth limits the amount of permissible feedback. Thus feedback compression techniques are essential, three of which are explored in this paper within the framework of 3GPP UTRA long term evolution. The tx antenna weight- sets are chosen from Grassmannian code books for 2times2 and 4times2 antenna configurations. Combining subcarriers in subgroups, and feeding back only one antenna weigh set per subgroup is shown to be a simple and effective technique. It reduces the feedback load by up to 96% for a typical urban channel profile, while maintaining the system performance within 3% from the optimum. Methods on the basis of run-length encoding are also shown to decrease the fed back load significantly, however, when forced to reduce the feedback to the same level as with subgroup encoding, their performance turns out to be inferior.

Apparatus, method and computer program product providing frequency domain multiplexed multicast and unicast transmissions

Abstract: A method is provided for applying frequency domain multiplexing of unicast and multicast services on a single carrier, such that both services can operate at the same time, and may be received with the same RF front end and A/D converter. In order to reduce subcarrier interference between unicast and multicast tones a guardband is introduced between the unicast and multicast bands, where the guardband can be fixed or variable within a sub-frame. Also disclosed is a device and computer program product operable with the device.

Analysis and Evaluation of Link Adaptation Including MIMO Adaptation

Abstract: This paper addresses the potential gain of including MIMO adaptation into Link adaptation (LA) Layer. Theoretical analysis is carried out from a new perspective, namely the distribution of unified instantaneous signal to interference and noise ratio (unified SINR) which encompasses MIMO schemes with different number of effective spatial streams and/or different receiver structures. Based on that, the capacity of LA including MIMO adaptation is formulated. Besides the theoretical analysis, issues concerning the practical application of LA including MIMO adaptation are discussed. A two dimensional lookup table (LUT) based on average SINR and SINR ratio is investigated for the selection of MIMO, modulation and coding set every transmission time interval. Results from simulations with real time domain LA show that significant spectral efficiency gain can be achieved as compared to the case of LA without MIMO adaptation.

Spectral Efficiency of Closed-Loop Transmit Diversity with Limited Feedback for UTRA Long Term Evolution

Abstract: Performance evaluation of closed-loop transmit diversity (CETD) for 3GPP UTRA long term evolution (ETE) is addressed in this paper. To reduce the feedback and keep comparable performance with optimum weighting, we reduce the feedback by means of quantization and subcarrier grouping. Theoretical analysis on loss of different quantization resolution and size of groups shows the tradeoffs between signalling overhead and performance. Although CETD can bring array and diversity gain, the interaction of CETD with some of the essential features of UTRA ETE system like adaptive modulation coding (AMC)-based time domain link adaptation and hybrid ARQ may affect the attainable spectral efficiency gain from CETD. In this paper, detailed link level simulation is carried out to investigate this interaction with two transmit antennas assuming one or two receive antennas. Simulation results show that the cell level gain is quite limited for CETD, in which only 9.8% and 18% gain is observed in micro- and macro- cell respectively with two receive antennas and a grouping size of 25

Apparatus, method and computer program product providing common channel arrangements for soft frequency reuse

Abstract: A device includes circuitry adapted to place at least a portion of at least one common channel on a fraction of an available bandwidth of a cell in a cellular communication system that uses soft reuse such that different orthogonal transmission resources are transmitted with different transmission powers and power usage is planned on a cell-by-cell basis; and a transmitter to transmit the common channel into the cell for reception by a plurality of receivers. Also disclosed is a method and a computer program product operable with the device.

Effect of Phase Noise on Spectral Efficiency for Utra Long Term Evolution

Abstract: In this paper, the effects of phase noise on the spectral efficiency of the next generation of OFDM based mobile systems with channel estimation is investigated. The simulation context and parameter settings are taken from the 3GPP Evolved UTRA (E-UTRA) study item, focusing on an OFDM downlink single antenna system in 20 MHz bandwidth. Phase noise is modeled as a Wiener-Levy process and several phase noise powers are evaluated. The OFDM coherent detection method is based on Pilot Assisted Channel Estimation (PACE) with Wiener based frequency domain interpolation and second order gaussian interpolation for the time domain interpolation. The cell level spectral efficiency is also evaluated for micro and macro-cell scenarios. The simulation results indicate that the phase noise effect in E-UTRA downlink can be reduced by using high performance local oscillator or by placing pilots in every OFDM symbols.

Impact of the Pilot Signal per Beam on the Ideal Number of Beams and Capacity Gain of Switched Beam Forming for WCDMA

Abstract: This study devises a simple mathematical model that predicts the number of beams that maximizes system capacity for different WCDMA network configurations. The ideal number of beams to be synthesized within a cell by an antenna array (AA) with a fixed number of elements at the base station (BS) is primarily influenced by the average antenna gain and the relative power allocated to the secondary common pilot channel (S-CPICH) transmitted on each directional beam. It is shown that for a fixed maximum Node-B transmit power the overall system capacity gain in the downlink (DL) provided by switched beam forming (SBF) decreases with the cell size, that is, as more power is needed by the pilot channels to assure coverage. Predictions from our model are compared with simulation results obtained from a detailed dynamic system level simulator in order to be validated. A remarkably good match is observed.

Network Performance of Node-B Switched, Beamforming and Dual Antenna User Equipment in, WCDMA

Abstract: We analyse the downlink (DL) cell throughput for a WCDMA system using switched beamforming (SBF) with 4-element antenna array at the base station (Node-B) and dual antenna (2Rx) user equipment (UE). We investigate the performance as a function of the penetration rate of 2Rx UEs. The performance assessment is conducted with dynamic system simulations, which are supplemented with simple theoretical analysis. Code blocking (CB) occurs when a UE is denied access in the cell due to lack of a DL channelisation code under the primary scrambling code for that cell. When the code-blocking problem is circumvented, it is observed from the simulation results that at 100% penetration rate of 2Rx UEs, the combined feature offers more than the multiplicative gain in the capacity improvement. The numerical result obtained from the theoretical analysis complements the simulation results. The SBF-2Rx code-unrestricted (CU) capacity gain is 327% compared to a 3-sector single directional antenna transmission at the Node-B and single antenna reception at the UE.