Hanane Fathi

Mobility management for VoIP in 3G systems: evaluation of low-latency handoff schemes

The introduction of IP-based real-time services in next-generation mobile systems requires coupling mobility with quality of service. The mobility of the node can disrupt or even intermittently disconnect an ongoing real-time session. The duration of such an interruption is called disruption time or handover latency, and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good quality of VoIP services. In this article, we focus on network-layer mobility and mobile IP since it is a natural candidate for providing such mobility. We evaluate different low-latency schemes based on mobile IP and compare their performances in terms of disruption time for VoIP services. Low-latency handoffs are performed by anticipating and/or postponing the mobile IP registration process. With these methods, disruption time is reduced to 200 ms in most considered cases.

Optimization of SIP Session Setup Delay for VoIP in 3G Wireless Networks

Wireless networks beyond 2G aim at supporting real-time applications such as VoIP. Before a user can start a VoIP session, the end-user terminal has to establish the session using signaling protocols such as H.323 and session initiation protocol (SIP) in order to negotiate media parameters. The time interval to perform the session setup is called the session setup time. It can be affected by the quality of the wireless link, measured in terms of frame error rate (FER), which can result in retransmissions of packets lost and can lengthen the session setup time. Therefore, such protocols should have a session setup time optimized against loss. One way to do so is by choosing the appropriate retransmission timer and the underlying protocols. In this paper, we focus on SIP session setup delay and propose optimizing it using an adaptive retransmission timer. We also evaluate SIP session setup performances with various underlying protocols (transport control protocol (TCP), user datagram protocol (UDP), radio link protocols (RLPs)) as a function of the FER. For 19.2 Kbps channel, the SIP session setup time can be up to 6.12 s with UDP and 7 s with TCP when the FER is up to 10 percent. The use of RLP (1, 2, 3) and RLP (1, 1, 1, 1, 1, 1) puts the session setup time down to 3.4 s under UDP and 4 s under TCP for the same FER and the same channel bandwidth. We also compare SIP and H.323 performances using an adaptive retransmission timer: SIP outperforms H.323, especially for a FER higher than 2 percent

Optimization of Mobile IPv6-Based Handovers to Support VoIP Services in Wireless Heterogeneous Networks

The support of voice over Internet Protocol (VoIP) services in next-generation wireless systems requires the coupling of mobility with quality of service. The mobile node can experience disruptions or even intermittent disconnections of an ongoing real-time session due to handovers. The duration of such interruptions is called disruption time or handover delay and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good-quality VoIP services. In this paper, the focus is on the network layer mobility, specifically on mobile Internet Protocols (MIPs), since they are natural candidates for providing mobility at layer 3. Using analytical models, the authors evaluate MIPv4, MIPv6, fast MIPv6 (FMIPv6), and hierarchical MIPv6 (HMIPv6) and compare their performances in terms of handover delay for VoIP services. To optimize the handover delay, the authors propose to use the adaptive retransmission timer described in this paper. The results obtained using the adaptive timer technique show that for a 3% frame error rate and a 128-kb/s channel, the handoff delay is about 0.075 s (predictive) and 0.051 s (reactive) for FMIPv6. It is around 0.047 s [intra-mobile anchor point (MAP)] and 1.47 s (inter-MAP) for HMIPv6, around 1 s for MIPv6, and 0.26 s for MIPv4

On SIP session setup delay for VoIP services over correlated fading channels

In this paper, the session setup delay of the session initiation protocol (SIP) is studied. The transmissions on both the forward and reverse channel are assumed to experience Markovian errors. The session setup delay is evaluated for different transport protocols, and with the use of the radio link protocol (RLP). An adaptive retransmission timer is used to optimize SIP performances. Using numerical results, we find that SIP over user datagram protocol (UDP) instead of transport control protocol (TCP) can make the session setup up to 30% shorter. Also, RLP drastically reduces the session setup delay down to 4 to 5 s, even in environments with high frame error rates (10%) and significant correlation in the fading process (f/sub D/T=0.02). SIP is compared with its competitor H.323. SIP session setup delay with compressed messages outperforms H.323 session setup delay.

LR-AKE-Based AAA for Network Mobility (NEMO) Over Wireless Links

Network mobility introduces far more complexity than host mobility. Therefore, host mobility protocols such as Mobile IPv6 (MIPv6) need to be extended to support this new type of mobility. To address the extensions needed for network mobility, the IETF NEMO working group has recently standardized the network mobility basic support protocol in RFC 3963. However, in this RFC, it is not mentioned how authentication authorization and accounting (AAA) issues are handled in NEMO environment. Also, the use of IPsec to secure NEMO procedures does not provide robustness against leakage of stored secrets. To address this security issue and to achieve AAA with mobility, we propose new handover procedures to be performed by mobile routers and by visiting mobile nodes. This new handover procedure is based on leakage resilient-authenticated key establishment (LR-AKE) protocol. Using analytical models, we evaluate the proposed handover procedure in terms of handover delay which affects the session continuity. Our performance evaluation is based on transmission, queueing and encryption delays over wireless links

Leakage-resilient security architecture for mobile IPv6 in wireless overlay networks

The coupling of mobility and quality-of-service with security is a challenge that should be addressed in future wireless overlay systems. The mobility of a node can disrupt or even intermittently disconnect an ongoing real-time session because a secure handover must be performed to ensure continuous connectivity. The duration of the such interruptions is called disruption time or handover delay and can heavily affect the user satisfaction. The handover procedure needs to protect its integrity and confidentiality-otherwise, the packets may be rerouted to a malicious node and the legitimate handover may not be performed. The security procedure to ensure this should not lengthen significantly the handover delay to provide good quality real-time services. In this paper, we focus on the network-layer mobility, specifically, on Mobile Internet protocol version 6 (MIPv6) since it is the natural candidate for providing such mobility in future systems. To solve the problem of on-path attackers and prevent leakage of secrets, we propose a security architecture for MIPv6 based on leakage resilient-authenticated key establishment (LR-AKE) protocol and its cooperation with public key infrastructure. The proposed architecture prevents against on-path attackers which was not addressed in the specifications of MIPv6, and also provides robustness against leakage of secret values. Using analytical models, we evaluate MIPv6 handover delay for real-time services. We identify the crucial factors affecting the handover delay among transmission delays of MIPv6, security and LR-AKE messages, queueing delays and en/decryption delays.

Designing socially robust 4G wireless services

The difficulties and technical limitations of the third generation (3G) of wireless mobile communication systems as well as the emergence of new mobile broadband technologies on the market have prompted university and industry researchers to thoroughly reflect on the fourth generation (4G) of these technologies. In this article, we outline the interaction between technology and society that shall help to develop 4G in a way that maximize its acceptance and penetration in the market, while minimizing the downside risk of its failure. This presupposes that the user is considered as the cornerstone in the design of 4G. As a consequence, we sum up the relevant service design rules derived from such a user-centric model and propose innovative 4G services

A pragmatic methodology to design 4g: from the user to the technology

The ever-increasing growth of user demands, the limitations of the Third Generation of Mobile Communication Systems (3G) and the emergence of new mobile broadband technologies on the market have brought researchers and industries to a throughout reflection on the Fourth Generation (4G). Many prophetic visions have appeared in literature presenting the future generation as the ultimate boundary of the wireless mobile communication without any limit in its potential, but practically not giving any designing rules and thus any definition of it. In this paper we hence propose a new user-oriented methodology that considers the user as “the angular stone in the design of 4G” and identifies his functional needs and expectations, reflecting and illustrating them in everyday life situations. In this way, we devise fundamental user scenarios where new services are significant assets for the user. The latter implicitly reveal the key features of 4G, which are then explicated in a new framework – the “user-centric” system – that, through a satellite hierarchical vision, describes the various level of interdependency among them. This approach consequently brings to the identification of the designing rules and therefore to a more pragmatic definition of 4G. Finally, an example of a new 4G application is also given in order to demonstrate the validity of the overall methodology.

Mobility management for VoIP: evaluation of mobile IP-based protocols

The support of IP-based real-time services in the next-generation mobile systems requires the coupling of mobility with quality of service. The mobile node can experience disruptions or even intermittent disconnections of an ongoing real-time session due to handovers. The duration of such interruptions is called disruption time or handover delay and can heavily affect user satisfaction. Therefore, this delay needs to be minimized to provide good quality VoIP services. In this paper, we focus on the network-layer mobility, specifically on mobile Internet protocols (MIP) since they are natural candidates for providing network layer mobility. Using analytical models, we evaluate MIPv4 and MIPv6 and compare their performances in terms of handover delay for VoIP services. To optimize the handover delay, we propose to use the adaptive retransmission timer described in this paper. The results obtained using the adaptive timer technique show that for 3% frame error rate and a 9.6 Kbps channel, the handoff delay is about 0.67 s for MIPv6 and 0.32 s for MIPv4. MIPv4 gives an appropriate support to VoIP services in terms of handover delay but the end-to-end delay may be affected by the triangular routing avoided in MIPv6.

On the impact of security on latency in WLAN 802.11b

In wireless networks, security is an essential feature that can be provided using a variety of protocols. On the other hand, the security protocols can affect applications to varying degrees depending on the network conditions. In this paper, we propose to evaluate the overhead introduced by the security mechanisms in WLAN such as authentication. To do so, we develop an analytical model based on random errors to evaluate the authentication delay for various error rates taking into account the reliability mechanisms involved. We also measure the authentication delay for WLAN 802.11b using CISCO access point and client cards. We generate the average, minimum and maximum delay for the different authentication configuration available in the CISCO security suite. The analytical and the experimental results are compliant. The major contributor of the authentication delay is the probing time needed to detect the surrounding access point.