T. Nihtilä, “Performance of Advanced Transmission and Reception Algorithms for High Speed Downlink Packet Access“, Ph.D. thesis, University of Jyväskylä, Finland, 2008.
This work studies the system level performance of several advanced techniques developed for Wideband Code Division Multiple Access (WCDMA) which is the most widely adopted technique for the air interface of 3rd generation (3G) wireless networks.
The performance is evaluated particularly with High Speed Downlink Packet Access (HSDPA) concept of WCDMA. The analysis considers the performance of advanced signal reception algorithms in combination with antenna diversity techniques in various realistic HSDPA network scenarios.
The performance of conventional Rake receiver is compared to a Linear Minimum Mean Squared Error (LMMSE) chip level equalizer being capable of intra- and inter-cell interference suppression. The receiver performance is evaluated with and without receive diversity and different transmit antenna diversity techniques, namely Space-Time Transmit Diversity (STTD) from open loop concepts and single and dual stream Transmit Antenna Array (TxAA) from the closed loop transmit diversity techniques. Also the impact of different HSDPA packet scheduling strategies, namely round robin and proportional fair scheduling, are observed.
The performance evaluation is done by changing several network attributes such as UE velocity, channel profiles and cell sizes. The study is done by means of extensive system level simulations using a comprehensive dynamic WCDMA network simulation tool, which comprises detailed modeling of signal propagation models, user mobility, traffic models, physical layer, radio resource management (RRM) algorithms and part of the upper layers of a WCDMA radio access network.
O. Alanen, A. Sayenko and T. Hämäläinen, “Scheduling Solution for the IEEE 802.16 Base Station“, Computer Networks 52(1), 2008, pp. 96-115.
The IEEE 802.16 standard defines a wireless broadband access network technology called WiMAX. It introduces several advantages, one of which is the support for QoS at the MAC level.
To ensure meeting the QoS requirements, the 802.16 base station must run some algorithm to allocate slots between connections. This algorithm is not defined in the 802.16 specification but rather is open for alternative implementations.
We propose a simple, yet efficient, solution that is capable of allocating slots based on the QoS requirements, bandwidth request sizes, and the 802.16 network parameters. To test the proposed solution, we have implemented the 802.16 MAC and PHY layers in the NS-2 simulator. Several simulation scenarios are presented that demonstrate how the scheduling solution allocates resources in various cases. According to the simulation results, the proposed scheduling solution ensures the QoS requirements of all 802.16 service classes. The solution shares free resources fairly and demonstrates work-conserving behaviour.
O. Alanen, H. Martikainen, A. Sayenko and V. Tykhomyrov, “Optimal MAC PDU Size in IEEE 802.16“, Proc. of the International Telecommunication Networking Workshop on QoS in Multiservice IP Networks, Venice, Italy, February 13-15, 2008.
In the IEEE 802.16 the number of errors and the MAC PDU size have an impact on the performance of the network.
We present a way to estimate the optimal PDU size and we run a number of simulation scenarios to study these parameters and how they impact on the performance of application protocols.
The simulation results reveal that the channel bit error rate has a major impact on the optimal PDU size in the IEEE 802.16 networks. Also, the ARQ block rearrangement influences the performance.
J. Puttonen, T. Väärämäki and G. Fèkete, “Next Generation Network Related Standardization – Enablers for the Convergence“, Proc. of the International Conference on Networks, Cancun, Mexico, April 13-18, 2008.
In this article we present the on-going standardization work related to the Next Generation Network (NGN) standardization.
Several standardization organizations are working on different aspects of NGN, such as Internet Engineering Task Force (IETF), Institute of Electrical and Electronics Engineers (IEEE) and 3rd Generation Partnership Project.
We present the current work and status of each standardization organizations and provide a use-case type example of the use, benefits and relations of the NGN research.
To achieve the visions of next generation networks presented by e.g. International Telecommunication Union (ITU) an efficient usage of the upcoming standards as well as co-ordination between standardization bodies are needed.
T. Nihtilä and V. Haikola, “HSDPA MIMO System Performance in Macro Cell Network“, Proc. of the IEEE Sarnoff Symposium, Princeton, NJ, USA, April 28-30, 2008.
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) is 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.
T. Nihtilä, “Increasing Femto Cell Throughput with HSDPA Using Higher Order Modulation“, Proc. of the International Networking and Communications Conference, Lahore, Pakistan, May 1-3, 2008.
In femto base station concept homes and small offices can be equipped with very low transmission power base stations to offer users high signal to interference and noise ratios (SINR) due to the close proximity of the base station unit.
In the first release of high speed downlink packet access (HSDPA) specification the highest supported modulation scheme, 16 quadrature amplitude modulation (16QAM), might not be efficient enough to fully exploit the superior signal quality offered by the femto base stations making the use of a higher order modulation desirable.
This paper presents a performance evaluation of using higher order modulation scheme, namely 64QAM, with HSDPA in a combined single frequency macro and femto cell scenario with advanced receivers used at mobile terminals.
The impact of femto cells and 64QAM is also analyzed as a function of indoor user penetration. The analysis is done using dynamic system level simulations.
P. Kela, J. Puttonen, N. Kolehmainen, T. Ristaniemi, T. Henttonen and M. Moisio, “Dynamic Packet Scheduling Performance in UTRA Long Term Evolution Downlink“, Proc. of the IEEE International Symposium of Wireless Pervasive Computing, Santorini, Greece, May 7-9, 2008.
In this paper we evaluate the performance of dynamic Packet Scheduling (PS) of 3GPP UTRAN Long Term Evolution (LTE) Downlink. Packet scheduling is of utmost importance in 3G LTE, because all traffic types with different Quality of Service requirements are competing of the resources.
We present a decoupled time and frequency domain packet scheduling framework for LTE downlink. Simulation results with three basic packet scheduler combinations with different amount of fairness are presented in four different 3GPP macro simulation cases to show the both extremes in tradeoff between fairness and spectral efficiency.
In addition, the effect of multiuser diversity on packet scheduling performance is studied. It is shown that by dividing the packet scheduler into a time domain and a frequency domain and utilizing different algorithms in both domains, the throughput fairness between users can be effectively controlled.
J.Kurjenniemi and V. Vartiainen, “MBMS Performance with Single Frequency Network Operation on WCDMA Network“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
The aim of this paper is to evaluate the system level performance of point-to-multipoint (p-t-m) multimedia broadcast multicast service (MBMS) using single frequency network (SFN) operation on WCDMA network.
This scheme is denoted as MBSFN within the 3rd Generation Partnership Project (3GPP). In MBSFN all Node Bs are using common scrambling code and transmissions are tightly synchronized between different Node Bs on dedicated carrier.
Due to common scrambling and usage of same channelization code transmissions from different Node Bs seems like a transmissions from single source through highly dispersive channel. Usage of common scrambling code removes inter-cell interference and only intra-cell interference is present, which can be effectively mitigated by, e.g., chip level equalization.
In this paper transmit power requirement for 95 % coverage with MBSFN is evaluated with dynamic system simulations. Emphasis is put on the receiver performance and effect of different non- idealities are evaluated, e.g., practical channel estimation.
N. Kolehmainen, J. Puttonen, P. Kela, T. Ristaniemi, T. Henttonen and M. Moisio, “Channel Quality Indication Reporting Schemes for UTRAN Long Term Evolution Downlink“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
In this paper we evaluate the performance of channel quality indicator (CQI) reporting schemes in 3GPP UTRAN long term evolution (LTE) downlink (DL).
In LTE, time and frequency dependent CQI is needed for DL packet scheduling (PS) and fast link adaptation (LA). Studies have indicated that frequency domain PS (FD-PS) and LA are essential techniques in improving the LTE performance, giving e.g. both cell throughput and coverage gain of around 40 % over a distributed multiplexing scheme.
However, there is a tradeoff with signaling overhead related to the CQI feedback and overall LA and PS performance, which is rather overlooked in the literature.
We analyze four different CQI reporting schemes with respect to system spectral efficiency and conclude that the best-M average and threshold based CQI reporting schemes seem to be the most promising in terms of the compromise between system performance and signaling overhead.
J. Puttonen, N. Kolehmainen, T. Henttonen, K. Aschan, P. Kela, M. Moisio and J. Ojala, “Performance of VoIP with Mobility in UTRA Long Term Evolution“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
In this paper, we study VoIP capacity in UTRA Long Term Evolution downlink under different mobility conditions. Since LTE is designed to be a wide area system supporting very high mobility, VoIP capacity for different mobility conditions is an important measure for the LTE system.
We show how the mobility dynamics affect the VoIP capacity, using a dynamic system simulator to model the effects of both Robust Header Compression (ROHC) and handovers.
The results indicate that the effect of non-ideal ROHC to VoIP system capacity is minimal, especially when compared to the mobility effects to system capacity.
J. Puttonen, T. Henttonen, N. Kolehmainen, K. Aschan, M. Moisio and P. Kela, “Voice-over-IP Performance in UTRA Long Term Evolution Downlink“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
In this paper, we study voice-over-IP (VoIP) performance in UTRA long term evolution (LTE) downlink (DL).
We have utilized fully dynamic system simulations to study the VoIP adaptive multi-rate (AMR) 12.2 codec capacity in four different 3GPP simulation cases. The effects of link adaptation (LA), packet bundling, control channel capacity and number of HARQ processes on VoIP capacity have also been considered.
The results present the absolute VoIP capacity numbers of LTE DL. We also show that LA together with packet bundling provides clear gain on the VoIP capacity, because more VoIP packets can be scheduled in each TTI. Also, the control channel limitations can be effectively compensated by packet bundling.
J. Äijänen, K. Aho, P. Lunden, and T. Ristaniemi, “Performance of VoIP over HSDPA in Mobility Scenarios“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
This paper presents an evaluation of Voice over IP (VoIP) system level performance in High Speed Downlink Packet Access (HSDPA) network.
The main purpose is to determine how VoIP over HSDPA performance is affected by HSDPA handover i.e. serving High Speed Downlink Shared Channel (HS-DSCH) cell change. This paper studies how sensitive the capacity of VoIP service is to handover delay and User Equipment (UE) velocity.
Additionally, the reliability of handover related signaling in downlink is evaluated. The system level performance of VoIP in the mobility related scenarios is evaluated with fully dynamic system level tool in which mobility of users, radio resource management functionalities and the interactions between them are explicitly taken into account.
The simulation results indicated moderate sensitivity of VoIP capacity to the UE velocity. High velocities lead to capacity loss for VoIP over HSDPA. Handover delays started to have significant effect only at UE velocity of 50 km/h or more. Reliability of handover signaling does not pose any problems even at high velocity and incurs only 1% resource overhead when transmitted over HSDPA.
K. Aho, J. Äijänen and T. Ristaniemi, “Impact of Mobility to the VoIP over HSUPA System Level Performance“, Proc. of the IEEE Vehicular Technology Conference, Singapore, May 11-14, 2008.
The aim of this paper is to evaluate the impact of mobility to the performance of voice over IP (VoIP) service in high speed uplink packet access (HSUPA) network.
The focus in the paper is on the uplink performance of VoIP as the uplink is considered most often to limit the overall coverage. When considering user’s mobility in the network, it is crucial to know how it impacts to overall performance, so that possible corrective measures can be taken. In this paper, the mobility is studied with detailed handover modeling including the effect of handover delays and active set sizes in different scenarios.
The system performance is evaluated with dynamic system level tool in which mobility of users, radio resource management functionalities and the interactions between them are explicitly taken into account.
The study indicated that the system performance is significantly affected by user mobility. Handover delay proved to have rather minor impact on the performance with low user velocities as performance loss remained within 10 % provided that the delay stayed within reasonable limits.
Limiting the active set size was observed to reduce the VoIP capacity only slightly as long as at least two links were allowed in the active set. In addition, silence indication frames specified for VoIP caused only a slight additional performance loss in mobility scenarios.
O. Alanen, A. Sayenko and T. Hämäläinen, “ARQ Aware Scheduling for the IEEE 802.16 Base Station“, Proc. of the IEEE International Conference on Communications, Beijing, China, May 19-23, 2008.
The IEEE 802.16 technology defines the ARQ mechanism that enables a connection to resend data at the MAC level if an error is detected.
In this paper, we analyze the ARQ aware scheduling for the 802.16 base station. In particular, we consider how the BS scheduler can account for the ARQ block size, absence of the ARQ block rearrangement, and the ARQ transmission window.
We propose a set of constraints that can be applied to any base station scheduler algorithm. To test them, we run a number of simulation scenarios. The simulations results confirm that the ARQ aware scheduling can improve the overall performance.
O. Alanen, V. Tykhomyrov, A. Sayenko, H. Martikainen and T. Hämäläinen, “On ARQ Feedback Intensity of the IEEE 802.16 ARQ Mechanism“, Proc. of the International Conference on Telecommunications, St. Petersburg, Russia, June 16-19, 2008.
The IEEE 802.16 standard defines the ARQ mechanism as a part of the MAC layer. The functioning of the ARQ mechanism depends on a number of parameters. The IEEE 802.16 specification defines them but it does not provide concrete values and solutions.
We ran simulation scenarios to study how the ARQ feedback intensity impacts the performance of application protocols. The simulation results reveal that a low ARQ feedback intensity results only in a marginal improvement.
Though it is possible to optimize the ARQ feedback intensity, it is reasonable to rely upon more frequent ARQ feedback messages as they do not result in a performance degradation. At the same time, ARQ connections, which work on top of HARQ, can delay the ARQ feedbacks up to the ARQ retry timeout to optimize the performance.
T. Nihtilä, “Capacity Improvement by Employing Femto Cells in a Macro Cell HSDPA Network“, Proc. of the IEEE Symposium on Computers and Communications, Marrakech, Marocco, July 6-9, 2008.
Very low transmission power (femto) base stations can be used in small isolated areas with insufficient or no macro cell coverage to provide very high bit rates to users at close proximity of the base stations.
In this paper the impact of femto cells operating on the same frequency as macro cells is evaluated in terms of several performance indicators in a realistically modeled single carrier HSDPA network by dynamic system level simulations. Conventional Rake and an advanced linear minimum mean squared error (LMMSE) equalizer receivers with and without receive diversity at the mobile terminals are considered.
The results showed that co-channel femto cells offer considerable gains from both user and network perspective with all receivers even if the femto cell users are not concentrated near the femto base stations.
O. Alanen, H. Martikainen and V. Tykhomyrov, “Impact of Portable Device Restrictions on IEEE 802.16 performance“, Proc. of the IEEE International Interdisciplinary Conference on Portable Information Devices, August 17-20, 2008
IEEE 802.16 is a good alternative for fast wireless connection in the next generation portable information devices (PID). However it was not originally designed for portable devices, but mobility was added later to the specification. This means that the lack of resources on portable devices might have a significant impact on which IEEE 802.16 features should be chosen and how they should be used.
Proper usage of ARQ can increase the IEEE 802.16 performance but it can also require much resources from PIDs.
In this paper we focus on how ARQ features are affected by limited resources on PID and how much the limitations affect on the performance.
J. Puttonen, N. Kolehmainen, T. Henttonen, M. Moisio and M. Rinne, “Mixed Traffic Packet Scheduling UTRAN Long Term Evolution Downlink“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications, Cannes, France, September 15-18, 2008.
In this paper we study the packet scheduling of mixed traffic in UTRAN long term evolution downlink.
A dynamic packet scheduling (PS) architecture with service classification, queue specific sorting and scheduling algorithms as well as frequency domain PS has been presented to differentiate scheduling of different traffic classes.
Simulation results have been provided by using control data, voice-over-IP (VoIP) and best effort (BE) traffic types. The results show that VoIP prioritizing is needed to keep the VoIP UEs satisfied. However, the strict prioritizing decreases the system spectral efficiency to around 70-80% of the pure BE spectral efficiency due to small VoIP packets.
J. Puttonen, N. Kolehmainen, T. Henttonen and M. Moisio, “Persistent Packet Scheduling Performance for Voice-over-IP in Evolved UTRAN Downlink“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications, Cannes, France, September 15-18, 2008.
In this paper we present and analyze different packet scheduling mechanisms for Voice-over-IP (VoIP) in UTRAN Long Term Evolution Downlink.
Dynamic packet scheduling provides multi-user and frequency domain scheduling gain, but at the expence of high control channel utilization. VoIP service with high number of simultaneous users and small packets can cause the control channel consumption to be the bottleneck for VoIP performance. Thus several persistent packet scheduling mechanisms have been proposed in 3GPP, such as fully persistent, talk-spurt based persistent and semi-persistent packet scheduling.
We analyze the VoIP performance of different packet scheduling mechanisms by using fully dynamic system level simulations.
We observe that with dynamic packet scheduling the VoIP capacity is restricted by the control channel capacity, whereas with persistent scheduling the capacity is restricted by the delay budget due to worse PRB SINR and resulting increased number of retransmissions.
J. Kurjenniemi and T. Henttonen, “Effect of Measurement Bandwidth to the Accuracy of Inter-frequency RSRP Measurements in LTE“, Proc. of the IEEE Symposium on Personal, Indoor and Mobile Radio Communications, Cannes, France, September 15-18, 2008.
In this paper we study the effect of reference signal received power (RSRP) measurement bandwidth on the accuracy of handovers and the UTRAN Long Term Evolution (LTE) system performance.
In 3rd Generation Partnership Project (3GPP) it has been agreed that inter-frequency RSRP measurement requirements would be developed assuming 6 middle physical resource blocks measurement bandwidth, which has also been agreed to be used for developing intra-frequency RSRP measurement requirements.
Wider handover measurement bandwidth could potentially provide better averaging against fading and thus, reduce the time required for performing inter-frequency handover measurements.
These studies are conducted with fully dynamic time-driven system simulator and simulations are done with different RSRP measurement bandwidths and different filters. Based on these studies wider bandwidth provides only minor improvement in measurement accuracy and it does not clearly reduce the time required for performing measurements.
J. Kurjenniemi and T. Henttonen, “Suitability of RSRQ for Quality Based Inter-Frequency Handover in LTE“, Proc. of the IEEE International Symposium on Wireless Communication Systems, Reykjavik, Iceland, October 21-24, 2008.
The purpose of this paper is to evaluate the suitability of reference signal received quality (RSRQ) measurement for quality based inter-frequency handover in UTRAN long term evolution (LTE).
Intra-frequency handovers in LTE are done based on reference signal received power (RSRP) measurements, which should ensure that users are always connected to the cell with the highest received power.
However, in certain environments where interference causes service quality degradation for the user (which RSRP measurement is not able to detect) there might be situation where a quality-based measurement would enable better system performance.
In this paper, we evaluate the success and correctness of RSRQ based inter-frequency handovers as means for preventing service degradation using dynamic system simulations.
However, comparison of RSRQ and RSRP based triggering suggest that RSRQ is not able to provide robust detection of service quality degradation. Furthermore, RSRQ is found to be heavily dependent on current system loading and the measurement strategy.
J. Turkka and M. Renfors, “Path Loss Measurements for a Non-line-of-sight Mobile-to-Mobile Environment“, Proc. of the International Conference on Intelligent Transport System Telecommunications, Phuket, Thailand, October 22-24, 2008
This paper shows results of narrowband path loss measurements in a typical urban and suburban mobile-to-mobile radio environment at 900 MHz band. The measurements were made with two omni-directional antennas with a transmitter and a receiver antenna height of 1.5 meters.
The results of measurements provide practical values for path loss exponent and standard deviation of shadowing in a non-line-of-sight radio environment.
These parameters can be used with a simple power law path loss model to predict reliable communication ranges for future communication systems operating in a mobile-to-mobile environment, such as a relay extended cellular networks, non-line-of-sight vehicle-to-vehicle communications or relay assisted positioning applications.
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