Wireless communications and networking have had tremendous developments in recent years. Recently, some proposals are presented in the literature to build hybrid structures out of different wireless systems. Also, architectures have been proposed for co-operating cellular and WLAN systems. Due to high complexity of mobile networks, proposed protocols and algorithms are usually evaluated by simulations. In these simulations, when real mobility is considered, a certain mobility model must be used. A number of mobility models have been proposed for ad hoc networks. Different mobility models have different properties in terms of node distribution, stability and reality. In a cellular system, hotspots are locations with a large number of subscribers. In hybrid WLAN/Cellular systems, WLANs are used to cover the hotspots. Evaluation of the performance of these hybrid networks should be performed through simulations or analytical modeling. Therefore, special mobility models are needed for this purpose. In this paper, we propose a mobility model based on the original version of random waypoint. This model is applicable for the simulating of the hybrid WLAN/Cellular systems. The proposed strategy is analyzed through simulations and analytical modeling.

The wireless communication with delivering variety of services to users is growing rapidly in recent years. The third generation of cellular networks (3G), and local wireless networks (WLAN) are the two widely used technologies in wireless networks.3G networks have the capability of covering a vast area; while, WLAN networks provide higher transmission rates with less coverage. Since the two networks have complementary properties, some attempts are made for their integration which could lead to an advantageous heterogeneous network. In such a heterogeneous network, provision of services like authentication, billing and quality of service are essential. In this article, a new mutual authentication protocol, namely, Non-Reputation Billing Protocol (NRBP) is proposed based on extensible authentication protocols. This authentication scheme provides a non-repudiation property for the billing problem. The proposed scheme is analyzed based on di erent security features and computation overhead. In comparison with previous approaches, this protocol contains all the considered security parameters. Moreover, the computation overhead of this protocol is less than other schemes.

The WiFi offloading has emerged as a solution to mitigate the surge of traffic in cellular networks. The design of WiFi networks and the placement of Access Points (APs) has a considerable impact on the overall performance and the corresponding capital and operational expenditure (CAPEX/OPEX). Therefore, the minimum required number of APs without severe performance degradation is one of the challenges in WiFi offloading. In this paper, we investigate the impact of multi-rate WiFi APs on the offloading performance. A numerical analysis is presented to compare the minimum required number of APs in two modes of single-rate and multi-rate of IEEE 802. 11 WLAN. The analysis results indicate the privilege of multi-rate WiFi AP when compared to single-rate WiFi AP. Moreover, the evaluation results show that required WiFi APs in multi-rate are 30% less than single rate WiFi APs.

CPW structure is became common structure for UWB and multi band antenna design and SRR structure is well-known kind of metamaterial that has been used in antenna and filter design for multi band application. In this paper, a SRR dual band monopole antenna with CPW-fed for WLAN and WiMAX is presented. The prototype antenna is designed for wireless communication such as WLAN and WIMAX respectively at 2.4 GHz and 5 GHz. The HFSS and CST microwave studio are used to simulate the prototype antenna for two different FEM and time domain method and they have also been compared with the experimental results. The total size of the antenna is 60mm×55mm×1.6mm and it is fabricated on FR-4 low cost substrate. The antenna is connected to a 50 W CPW feed line. Its bandwidth is around 3% for 2.45 GHz (2.4-2.5 GHz) and 33% for 5.15GHz (4.3-6 GHz).Its limited bandwidth in 2.4 GHz frequency is benefit for power saving at indoor application. The antenna has 2-7 dBi gain in the mentioned bands with an Omni-directional pattern. The antenna experimental result shows good similarity to simulation kind for return loss and pattern. Here, the effect of parasitic SRR on current distribution has been studied in presence and absence of parasitic element. The simulation of polarization is confirmed that the antenna has linear polarization. Here comparison between antenna return losses in absence of each parasitic element is presented.

This paper presents an active down-conversion mixer for wireless local area networks (WLAN) application. The proposed down-conversion mixer is designed for 2-3 GHz radio frequency (RF) band and an intermediate frequency (IF) of 100 MHz using RFTSMC CMOS 0. 18 μ m technology. A new fully differential Darlington cell is introduced in the RF transconductance stage to suppress third-order nonlinearity and improve mixer linearity. In addition, the conversion gain (CG) and noise performance of the proposed mixer are improved by using a diode-connected active load and current bleeding technique. The proposed mixer has been simulated by Advanced Design System (ADS) and Spectre-RF softwares. The results of post-layout simulation show the third-order input intercept point (IIP3) can be improved up to 12. 5 dBm by optimum biasing of the Darlington cell. The proposed mixer achieves high isolation between ports, the high conversion gain of 14 dB and the low double side-band noise figure (DSB-NF) of 5 dB at the input frequency of 2. 4 GHz. The mixer operates at the supply voltage of 1. 8 V with power consumption of 17 mW.

In this paper a novel dual-band printed diversity monopole antenna integrated on a PCMCIA network card is proposed and studied. The antenna which consists of two monopoles with symmetric configuration operates at 2.4/5.2 GHz WLAN with very high isolation over two operational bands. The effects of some important parameters of proposed antenna are studied. The diversity performance is evaluated by calculating the envelope correlation coefficient and mean effective gain (MEG) of each element. These evaluations show that the proposed diversity antenna can provide spatial and pattern diversity to combat multi-path fading in mobile devices and WLAN applications.