Robert Bestak

The study of handover procedure in LTE-based femtocell network

Wireless systems have the capability to address broad geographic area without the costly infrastructure deployment. However, the main drawback resides in the bandwidth limitation and the coverage for single access point. The deployment of Femtocell as the promising wireless access technology becomes one of the possible solution. In this paper the handover procedure in femtocell network is studied. The 3GPP LTE based handover is analysed in three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive and proactive handover strategy is also proposed as the handover decision policy to diminish the very frequent and unnecessary handovers.

WiMAX throughput evaluation of conventional relaying

The paper analyses performance of IEEE 802.16 standard, also known as WiMAX, when relay stations are introduced. Thanks to this feature, coverage area and throughput of the system may be significantly enhanced. The article defines the increase of system capacity of the relay based cell deployment compared to a conventional single hop deployment of the same area size. Further, the parameters that have main impact on the system with relays and its capacity are determined.

WiMAX Performance Evaluation

In recent time, new advanced wireless systems emerged at the world markets. One of the most promising is undoubtedly IEEE 802.16 standard, also known as WiMAX. For both, service providers and potential customers, is necessary to know its basic capabilities, such as the number of supported subscriber per BS or transferred data rate that may be delivered. This paper is aimed at 802.16-2004 standard that is intend to fixed broadband wireless access.

Handover procedure and decision strategy in LTE-based femtocell network

Wireless systems have the capability to serve users over broad geographic area without using a costly network infrastructure. However, the main drawback of these systems represents the bandwidth restrictions and coverage. Deployment of femtocell as the emerging promising wireless access technology becomes one of possible solution how to overcome some of the drawbacks. In this paper, we investigate the handover procedure in femtocell network considering, both types of handovers, horizontal and vertical. The 3GPP LTE based handover procedure is analysed for three scenarios: hand-in, hand-out and inter-FAP. In addition, the reactive handover decision policy, based on the prediction of user movement and the prediction of target-FAP, is proposed as a way to eliminate frequent and unnecessary handovers.

Femtocells in 3G Mobile Networks

This paper investigates influence of femtocells to the traditional mobile network hierarchy and their features. This upcoming technology is supposed to be widely deployed in the upcoming wireless and mobile networks. These small base stations are designed to improve indoors capacity, reducing macro cell traffic or to provide services in locations without signal or with weak coverage. The paper discusses usage of femtocell and related challenges, such as interferences, frequency spectrum planning, handovers or integration of femtocells into mobile networks.

Impact of Handover on VoIP Speech Quality in WiMAX Networks

VoIP is one of the most emerging technologies in the area of speech communications. VoIP is widely deployed in fixed line access networks. However, user’s requirements on the mobility within communication and on the quality of the speech communications are increasing. Therefore, VoIP technology is more and more integrated into broadband wireless networks with QoS support such as WiMAX. The latest version of WiMAX standard, based on IEEE 802.16e, has implemented a full mobility support. The mobility is allowed due to a handover procedure. IEEE 802.16e specifies only one mandatory handover procedure: hard handover. This handover type is easy to implement, but it increases end-to-end packet delay that is critical for delay sensitive services such as VoIP. This paper evaluates an impact of the handover on the speech quality in VoIP networks.

Delay Performance of Session Establishment Signaling in IP Multimedia Subsystem

In this paper we investigate and analyze SIP delay during the session establishment signaling process in the IMS system. The delay for end-to-end link scenarios such as WiMAX-to-WiMAX, UMTS- to-UMTS, UMTS-to-WiMAX and vice versa are examined. For the analysis, we consider three types of delays: transmission delay, processing delay and queuing delay. The results show that the main delay of session establishment signaling process is due to the processing delay. In addition, the lower channel rate in the UMTS network as well as IMS service rate has significant impact to the session establishment signaling delay. In this paper, we review and analyze the delay of the session establishment signaling process. We present the structure of session establishment signaling process that is based on the standard. We analyze the delay, not only during the IMS processes where the S-CSCF, P-CSCF, I-CSCF and HSS take part, but also the transmission delay and the delay when the SIP messages are queued in the network. The transmission delay is analyzed as end-to-end delay where the source terminal (ST) and the destination terminal (DT) are either UMTS or WiMAX terminals. In term of transmission delay, the RLC (Radio Link Control) delay at the UMTS network and the non RLC delay at the WiMAX network are considered. The queuing delay is analyzed for the M/M/1 scheme. We also examine which delay among the transmission, processing and queuing delays that contributes the most significant delay in the system.

Overhead of ARQ mechanism in IEEE 802.16 networks

Different techniques for error correction such as automatic repeat request, forward error correction or combination of both methods also known as hybrid automatic repeat request are utilized in today’s wireless networks. All these techniques require an implementation of control and management mechanisms to ensure its proper work. These mechanisms increase the management overhead and consume a part of network capacity. It leads to the reduction of data throughput dedicated to users. Besides, the control mechanism can negatively influence a packet delay. This paper proposes three alternatives of automatic repeat request mechanism to minimize the management overhead without a negative impact on the packet delay. Description of all proposed mechanisms, their evaluation and comparison with conventional techniques used in the IEEE 802.16 networks are presented in this paper.

Optimization of handover scanning procedure in WiMAX networks with relay stations

This paper proposes an optimization of management messages and their exchange during a scanning procedure of mobile stationpsilas neighborhood in WiMAX based networks with relay stations. The scanning procedure allows a mobile station to obtain information about handover target access stations. In IEEE 802.16e standard, where the relay stations are not considered, the exchange of requested information for handover execution is done among base stations and backbone network. When taking into account the relay stations, a new wireless interface among the base stations and relay stations emerged. Thus, a new communication scheme over the radio interface has to be proposed and optimized in order to reduce the management information overhead and to maximize the user data throughput.

Optimization of network entry procedure in relay based WiMAX networks

The paper focuses on a network entry procedure in the IEEE 802.16 standards. The procedure in PMP mode is briefly described and further contemplates how the original procedure is modified when introducing relay stations into the system. On the basis of simulation, the paper proposes an enhancement to the original association procedure in relay scenarios by adding a new phase called Path selection. Thanks to this feature, the overall system performance may be increased.