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A hepta-band bandpass filter (HB-BPF) based on folded cross-loaded stepped impedance resonator (SIR) was investigated. A cross-loaded SIR microstrip structure was arranged to produce several transmission zeros. In order to reduce the filter size, a folded cross-loaded SIR was proposed. The HB-BPF was designed on FR4 microstrip substrate with ε r = 4.4, thickness h = 0.8 mm, and tan δ = 0.0265. This HB-BPF achieves transmission coefficients of 0.

Internet users have grown substantially over the last decade, especially following the emergence of mobile technology. Most Internet connections nowadays are accessed using mobile devices in order to stay connected all the time and everywhere. Owing to the limited coverage of such access points as well as base stations, mobile devices are required to handover connectivity if there is a move to other locations. Horizontal handover is conducted when the movement is within the same network. Otherwise, there must be vertical handover when external network infrastructure is encountered. However, as the Internet is an open network that naturally lacks trust between users, the mobile nodes that move to an external network are susceptible to various attacking activities. Compromising mobile nodes may cause users to lose their data as well as destroy their mobile devices in terms of both software and hardware. Securing mobile devices is crucial in order to avoid losses in terms of not only money but also facilities. Although mobile nodes have been developed with certain security features, some researchers have found vulnerabilities. This paper surveys in detail the security vulnerabilities of mobile IPv6 vertical handover and the current relevant mitigation methods. Furthermore, we describe the mechanism of mobile IPv6 vertical handover and its security vulnerability as well as security mechanisms proposed by researchers. Based on the survey, there are apparently weaknesses in current security features that are in need of solutions to minimize the effect of malicious activities. An open direction of future research on mobile IPv6 vertical handover security is elaborated at the end of this paper.

<span lang="EN-US">In this paper, circular-shaped microstrip antenna was simulated, fabricated, and measured accordingly. As the novelty, to enhance bandwidth and reduce antenna size, beleved half-cut microstrip structure is proposed. Further, this proposed antenna structure will be applied to multiple input multiple output (MIMO) antenna 2</span><span lang="EN-US">´</span><span lang="EN-US">2. Therefore, this research was investigated conventional circular shape antenna (CCSA), circular shaped beleved antenna (CSBA), and MIMO circular shaped beleved antenna (MIMO-CBSA) as Model 1, Model 2, and Model 3, respectively. An FR4 substrate with er= 4.4, thickness h=1.6 mm, and tan d=0.0265 was used. The simulation has been conducted using Advanced Design System (ADS). The antenna CCSA/CSBA/ MIMO-CBSA achieve 1.831GHz/2.265 GHz/2.256 GHz, -15.13dB/-17.37dB/-17.25 dB, 1.42/1.31/1.33, and 1.474/2.332/2.322 for center frequency, reflection coefficient, VSWR, and bandwidth, respectively. This antenna has a size 63x90 mm and 51.5x90 mm for CCSA (Model 1) and CSBA (Model 2), respectively. After the structure of MIMO 2</span><span lang="EN-US">´</span><span lang="EN-US">2 was applied, the size of antenna MIMO-CBSA (Model 3) became 180 mm x 180 mm with a mutual coupling (S₂₁)=-26.18 dB and mutual coupling (S₃₁)=-26.41 dB. The result showed that proposed antenna CSBA (Model 2) has wider-bandwidth of 58,2% and smaller-size of 18.2%. Furthermore, after CSBA (Model 2) structure was applied to MIMO 2</span><span lang="EN-US">´</span><span lang="EN-US">2 (Model 3) and the MIMO antenna obtain good mutual coupling (&lt;-15dB). Moreover, the measured results are good agreement with the simulated results. In conclusion, all of these advantages make it particularly valuable in multistandard antenna applications design such as GSM950, WCDMA1800, LTE2300, and WLAN2400.</span>

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