K. Aho, “Performance enhancements of MBMS and VoIP services in WCDMA/HSPA networks“, Licenciate Thesis, ISBN 978-951-39-3687-7, University of Jyväskylä, August, 2009.
The purpose of this thesis is to address the performance of Multimedia Broadcast Multicast Service (MBMS) and Voice over IP (VoIP) services in Wideband Code Division Multiple Access (WCDMA)/High Speed Packet Access (HSPA) networks. MBMS and VoIP services have already gained vast popularity in the fixed networks and thus it is very likely that they will also be key concepts in wireless cellular networks in the near future.
Special attention in this thesis will be paid on the mobility aspect of both of those services. Studies include the performance evaluation of MBMS with macro diversity combining with and without receive diversity. From the perspective of macro diversity soft and selective combining are evaluated. In addition, concept called Rx-switching is evaluated in order to provide some battery saving opportunities for MBMS terminals employing multiple receive antennas.
This thesis evaluates the performance with help of fully dynamic system simulator where user mobility, fading, propagation and radio resource management functionalities are explicitly taken into account.
I. Repo, K. Aho, T. Nihtilä, and T. Ristaniemi, “Analysis of RRM Limitations and Restricted Transmission Periods for VoIP over HSDPA“, Proc. of 5th Asian Internet Engineering Conference (AINTEC), Bangkok, Thailand, November 18-20, 2009.
This paper studies how the performance of Voice over IP (VoIP) over High Speed Downlink Packet Access (HS-DPA) networks is affected if transmission to a User Equipment (UE) is stopped for specific amount of time during handover procedure.
This paper also addresses the situation when it might be necessary to limit the number of UEs in a cell.
The study showed that parameter settings for Radio Resource Management (RRM) algorithms can have an effect to the VoIP capacity: If handover lasts long enough for VoIP packets to be lost, or severe congestion occurs in a cell, VoIP capacity may be degraded.
The aim of this paper is to evaluate how Discontinuous Reception (DRX) cycles and related timers take effect to Voice over IP (VoIP) performance when High Speed Downlink Packet Access (HSDPA) networks are in question.
DRX cycles limit the scheduling freedom of users and increase battery saving opportunities in the User Equipment (UE) by allowing it to turn its receiver circuitry off for some periods of time.
Prior work has concentrated mainly on optimizing the usage of radio resources when small bit rate delay critical services, like VoIP, are considered. However, the battery life of small handheld devices might become a limiting factor in providing satisfactory user experience.
Thus, this paper evaluates the performance also from the battery life perspective when DRX cycles together with VoIP are considered. The performance is evaluated with a fully dynamic system level tool in which the mobility of the users, radio resource management functionalities and the interactions between them are explicitly taken into account.
The study indicated that the longer the DRX cycle is the higher are the battery saving opportunities but at the same time VoIP over HSDPA capacity can be compromised. Capacity degeneration in pure VoIP traffic simulations was, however, possible to be mitigated by using an adequately long inactivity timer. In mixed traffic scenarios including both VoIP and Best Effort (BE) traffic, higher cell throughput was achieved by allowing more scheduling time for BE users with adequately long DRX cycle and a short inactivity timer.
J. Puttonen, N. Kolehmainen, T. Henttonen and J. Kaikkonen, “On Idle Mode Mobility State Detection in Evolved UTRAN“, Proc. of International Conference on Information Technology: New Generations, Las Vegas, Nevada, USA, April 27-29, 2009.
In this paper we present different idle mode mobility state detection mechanisms targeted for 3GPP Evolved UTRAN.
The purpose is to study the reliability of the mobility state detection mechanism specified in 3GPP TS 36.304 for 3GPP Release 8 in varying conditions, such as different re-selection thresholds, UE velocities and inter-site distances. Three mobility states have been defined in TS 36.304 based on occurred cell re-selections in a certain time window.
According to small inter-site distance simulations, pedestrian speeds (normal mobility state) can be detected with a quite satisfactory accuracy but distinguishing the medium and high mobility states is quite challenging, since UEs are experiencing quite large variance in number of re-selections with the same UE velocities. Simulations with large inter-site distances show similar results.
T. Nihtilä, K. Aho and I. Repo, “On Serving Cell Change Reliability in HSDPA Network“, Proc. of IEEE Wireless Communications & Networking Conference, Budapest, Hungary, April 5-8, 2009.
In Wideband Code Division Multiple Access (WCDMA) networks the Signaling Radio Bearer (SRB) is transmitted downlink to inform the user i.a. when it needs to make a handover.
When transmitting e.g. Voice over IP (VoIP) on High Speed Downlink Packet Access (HSDPA) SRB is mapped on HSDPA user data channel, high-speed downlink shared channel (HS-DSCH) in order to maximize voice capacity.
The lack of support for soft handover (SHO) of HS-DSCH may compromise the reception of SRB and thus also a possible incoming serving HSDPA cell change command especially at the cell borders. This can lead to serious VoIP service degradation due to prolonged camping on a poor cell and in the worst case even to call dropping, if the cell change command is not received before VoIP call drop criterion is met.
This paper considers the performance of SRB transmission on source cell HS-DSCH during a handover process. Also a strategy of transmitting the serving cell change command from the target cell is analyzed. The study is done by the means of fully dynamic system simulations and they consider both macro-cell and manhattan scenarios.
The results show that a relatively low SRB/handover error rate is experienced in a macro cell scenario but in a more challenging manhattan scenario the error rate is higher. Transmitting the serving cell change command from the target cell HS-SCCH results in similar handover failure rates in manhattan scenario than using SRB on HS-DSCH in macro-cell scenario when static power allocation for HS-SCCH is in use.
J. Puttonen, G. Fèkete, T. Väärämäki and T. Hämäläinen, “Multiple Interface Management of Multihomed Mobile Hosts in Heterogeneous Wireless Environments“, Proc. of the International Conference on Networks, Cancun, Mexico, March 1-6, 2009.
In this paper we present our solution for intelligent network interface selection and (vertical) handover control for heterogeneous multi-access environments.
The 4th generation mobile communication system is seen as a combination of several access technologies optimized for different purposes. A combination of these access technologies can constitute, with intelligent control, a 4G access with capabilities to support various application and user requirements and preferences.
A policy based vertical handover controller system, called VERHO, utilizes input from several cross-layer sources, the Mobile IPv6 protocol and network interface selection to achieve both proactive and intelligent vertical handovers between a variety of access interfaces. Real-time link status information, access point scanning support, user profiles, policies and Multiple Attribute Decision Making algorithms provide flexibility in interface selection and result in an Always-Best-Connected access for the user.
We present the VERHO architecture along with discussing and showing the possible benefits of such system in the future.
O. Alanen, A. Sayenko, H. Martikainen, V. Tykhomyrov, A. Puchko and T. Hämäläinen, “WINSE: WiMAX NS-2 Extension“, Proc. of the International Conference on Simulation Tools and Techniques, Rome, Italy, March 2-6, 2009.
IEEE 802.16 standard defines the wireless broadband technology called WiMAX. When compared to other wireless technologies, it introduces many interesting advantages at PHY, MAC, and QoS layers. Heavy simulations are needed to study IEEE 802.16 performance and propose further enhancements to this standard.
Link level simulations are not always sufficient, while system level simulators are not always accurate to capture MAC and transport protocol details. We implemented a 802.16 extension for the NS-2 network simulator. It includes upper PHY modeling, almost all the features of the 802.16 MAC layer, as well as the QoS framework.
This article describes the implemented features, simulation methodology, and shares our experience that can be used with other NS-2 modules. An overview of research papers, where this implementation was used, is given.
O. Alanen, H. Martikainen and A. Sayenko, “ARQ Parameters for VoIP in IEEE 802.16 Networks“, Proc. of the Wireless Telecommunication Symposium, Prague, Czech Republic, April 22-24, 2009.
IEEE 802.16 standard defines two data retransmission mechanisms. HARQ provides fast retransmissions in cost of slightly increased overhead. On the contrary, ARQ has less overhead in cost of bit longer delays. It is therefore often used with BE connections. In addition to delay tolerant applications, BE can also be used for real-time services.
Therefore, in this paper we analyze the ARQ mechanism and provide guidelines on how to set the ARQ parameters to achieve a good balance between the VoIP delay and packet loss.
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