6,652 research outputs found
A Hybrid Model to Extend Vehicular Intercommunication V2V through D2D Architecture
In the recent years, many solutions for Vehicle to Vehicle (V2V)
communication were proposed to overcome failure problems (also known as dead
ends). This paper proposes a novel framework for V2V failure recovery using
Device-to-Device (D2D) communications. Based on the unified Intelligent
Transportation Systems (ITS) architecture, LTE-based D2D mechanisms can improve
V2V dead ends failure recovery delays. This new paradigm of hybrid V2V-D2D
communications overcomes the limitations of traditional V2V routing techniques.
According to NS2 simulation results, the proposed hybrid model decreases the
end to end delay (E2E) of messages delivery. A complete comparison of different
D2D use cases (best & worst scenarios) is presented to show the enhancements
brought by our solution compared to traditional V2V techniques.Comment: 6 page
On the Minimization of Handover Decision Instability in Wireless Local Area Networks
This paper addresses handover decision instability which impacts negatively
on both user perception and network performances. To this aim, a new technique
called The HandOver Decision STAbility Technique (HODSTAT) is proposed for
horizontal handover in Wireless Local Area Networks (WLAN) based on IEEE
802.11standard. HODSTAT is based on a hysteresis margin analysis that, combined
with a utilitybased function, evaluates the need for the handover and
determines if the handover is needed or avoided. Indeed, if a Mobile Terminal
(MT) only transiently hands over to a better network, the gain from using this
new network may be diminished by the handover overhead and short usage
duration. The approach that we adopt throughout this article aims at reducing
the minimum handover occurrence that leads to the interruption of network
connectivity (this is due to the nature of handover in WLAN which is a break
before make which causes additional delay and packet loss). To this end, MT
rather performs a handover only if the connectivity of the current network is
threatened or if the performance of a neighboring network is really better
comparing the current one with a hysteresis margin. This hysteresis should make
a tradeoff between handover occurrence and the necessity to change the current
network of attachment. Our extensive simulation results show that our proposed
algorithm outperforms other decision stability approaches for handover decision
algorithm.Comment: 13 Pages, IJWM
Interworking Architectures in Heterogeneous Wireless Networks: An Algorithmic Overview
The scarce availability of spectrum and the proliferation of
smartphones, social networking applications, online gaming
etc., mobile network operators (MNOs) are faced with an
exponential growth in packet switched data requirements on
their networks. Haven invested in legacy systems (such as
HSPA, WCDMA, WiMAX, Cdma2000, LTE, etc.) that have
hitherto withstood the current and imminent data usage
demand, future and projected usage surpass the capabilities of the evolution of these individual technologies. Hence, a more critical, cost-effective and flexible approach to provide ubiquitous coverage for the user using available spectrum is of high demand. Heterogeneous Networks make use of these legacy systems by allowing users to connect to the best network available and most importantly seamlessly handover active sessions amidst them. This paper presents a survey of interworking architectures between IMT 2000 candidate networks that employ the use of IEFT protocols such as MIP, mSCTP, HIP, MOBIKE, IKEV2 and SIP etc. to bring about this much needed capacity
EVM as generic QoS trigger for heterogeneous wieless overlay network
Fourth Generation (4G) Wireless System will integrate heterogeneous wireless
overlay systems i.e. interworking of WLAN/ GSM/ CDMA/ WiMAX/ LTE/ etc with
guaranteed Quality of Service (QoS) and Experience (QoE).QoS(E) vary from
network to network and is application sensitive. User needs an optimal mobility
solution while roaming in Overlaid wireless environment i.e. user could
seamlessly transfer his session/ call to a best available network bearing
guaranteed Quality of Experience. And If this Seamless transfer of session is
executed between two networks having different access standards then it is
called Vertical Handover (VHO). Contemporary VHO decision algorithms are based
on generic QoS metrics viz. SNR, bandwidth, jitter, BER and delay. In this
paper, Error Vector Magnitude (EVM) is proposed to be a generic QoS trigger for
VHO execution. EVM is defined as the deviation of inphase/ quadrature (I/Q)
values from ideal signal states and thus provides a measure of signal quality.
In 4G Interoperable environment, OFDM is the leading Modulation scheme (more
prone to multi-path fading). EVM (modulation error) properly characterises the
wireless link/ channel for accurate VHO decision. EVM depends on the inherent
transmission impairments viz. frequency offset, phase noise,
non-linear-impairment, skewness etc. for a given wireless link. Paper provides
an insight to the analytical aspect of EVM & measures EVM (%) for key
management subframes like association/re-association/disassociation/ probe
request/response frames. EVM relation is explored for different possible
NAV-Network Allocation Vectors (frame duration). Finally EVM is compared with
SNR, BER and investigation concludes EVM as a promising QoS trigger for OFDM
based emerging wireless standards.Comment: 12 pages, 7 figures, IJWMN 2010 august issue vol. 2, no.
Handover Necessity Estimation for 4G Heterogeneous Networks
One of the most challenges of 4G network is to have a unified network of
heterogeneous wireless networks. To achieve seamless mobility in such a diverse
environment, vertical hand off is still a challenging problem. In many
situations handover failures and unnecessary handoffs are triggered causing
degradation of services, reduction in throughput and increase the blocking
probability and packet loss. In this paper a new vertical handoff decision
algorithm handover necessity estimation (HNE), is proposed to minimize the
number of handover failure and unnecessary handover in heterogeneous wireless
networks. we have proposed a multi criteria vertical handoff decision algorithm
based on two parts: traveling time estimation and time threshold calculation.
Our proposed methods are compared against two other methods: (a) the fixed RSS
threshold based method, in which handovers between the cellular network and the
WLAN are initiated when the RSS from the WLAN reaches a fixed threshold, and
(b) the hysteresis based method, in which a hysteresis is introduced to prevent
the ping-pong effect. Simulation results show that, this method reduced the
number of handover failures and unnecessary handovers up to 80% and 70%,
respectively
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