The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
As the need for high speed connectivity in mobile environments increases, it becomes necessary to understand the impact of mobility on performance characteristics of wireless communication system. This paper presents an investigation of the mobility impact on performance of a WiMAX 802.16e downlink system deployed via Stratospheric platform for a ground user. It shows how user velocity and physical...
In this paper, we study the performance of VoIP over WiMAX systems. We assume a two-path model for airport surface communications and experiment by using a multipath fading simulator. We evaluate the R-factor when the mobile speed and delay time are changed. We use an R-factor of 80 which is defined in ED-136 as a threshold where VoIP can be used for air traffic control (ATC). When the delay time...
Worldwide interoperability for microwave access (WiMAX) is an IEEE802.16 standard that provides low cost, high-speed and long-range wireless communications, where the 802.16m is the latest version of WiMAX standard fully optimized for fixed and pedestrian speeds. Due to dynamic multipath fading and high Doppler shift, there is service degradation on quality of service (QoS) and data rate. In this...
In this paper, We extended our previous work of QR-RLS based MIMO(Multiple input Multiple output) channel estimation to Mobile Wimax 802.16m system. Mobile wimax system provides high data rate, also fulfills user's requirement like VOD(Video on demand)at very high vehicle speed and also provides better cell coverage area. Channel estimation is crucial part to achieve this goals especially in fast...
In this article we propose a new simulation module for NS-2 able to reproduce the performance of fixed terminals operating in a wireless network with one or more antennas at the receive end, based on empirical models validated on the literature. This is relevant to perform accurate cross layer analyses of fixed wireless systems as Wireless Local Loop, relay networks, WiMax for fixed or repositionable...
The present article describes the experimental result of victim system detection by UWB wireless system to contribute for Japanese UWB regulatory discussion, in which a mitigation, including detect-and-avoid (DAA), technology implementation in the frequency range of 3.4 to 4.8 GHz is a major technical topic. A FPGA based MB-OFDM UWB receiver with 528 MHz sampling rate and 128 points FFT capability...
To protect vital control information from deep fades, repetition coding is recommended in mobile WiMAX. This paper considers repetition coding as a maximum ratio combining process and proposes an expression for the coding gain and its effect on BER. A 10-state finite state Markov channel (FSMC) model is also proposed for the implementation of the adaptive modulation and coding (AMC) scheme in mobile...
The emerging mobile WiMAX (IEEE 802.16e) has gained serious attention as a means of providing wireless broadband access to mobile users. 802.16e supports high data rates and QoS for various applications, and is thus a powerful contender for next generation wireless access technology. On the other hand, IEEE 802.11 a/b/g/n have already been widely used to provide high data rates in a limited area....
Security in wireless networks has traditionally been considered to be an issue to be addressed at the higher layers of the network. However, with the emergence of ad hoc and other less centralized networking architectures, there has been an increase in interest in the potential of the wireless physical layer to provide communications security. Information theory provides a natural framework for the...
Simulation models are key factors in evaluating the performance of any current communication systems. In addition, evaluating the improvements carried out along the optimization of a system requires access to information about behavioural changes induced on it. For Wimax and other wireless standards simulation results depend on many particular aspects regarding to link level models. This work summarizes...
A lot of conventional algorithms have tried to cancel the residual frame synchronization error (RFSE), which causes the performance degradation of channel estimation when using interpolation between pilot sub-carriers in comb-type pilot-aided OFDM systems. Among them, a tracking method has been attractive to provide good performance by eliminating the effects of RFSE. However, it requires high computational...
WiMAX (IEEE 802.16) is a broadband wireless access technology that enables convergence of mobile and fixed broadband networks through scalable OFDMA (Orthogonal Frequency Division Multiple Access) technology. This paper presents an analytical study of WiMAX propagation channel and estimates the channel capacity through simulation. WiMAX channel performance of different spectrum frequency bands applied...
Users mobility in wireless networks has the obvious effect of increasing the channel fading fluctuation rate, hence the efficiency of opportunistic scheduling algorithms. In time-slotted wireless systems, the chosen slot size has to be compatible with the average channel access time (AAT) in order to preserve the multiuser diversity gain of the scheduling algorithm. This paper proposes to determine...
The IEEE 802.16e mobile WiMAX system may not be quite suitable in some applications where the uplink (UL) requires higher transmission rate than the downlink (DL). In particular, many cases in military applications often require higher transmission rate in the uplink. In this paper, we propose a new mobile WiMAX scheme that provides the DL to UL ratio (DUR) to be 9:33 by modify the frame structure...
In this paper, we present an efficient interleaver, designed for future personal mobile satellite services. Burst errors incurred by long term fading of mobile satellite channels will seriously degrade the service quality. Interleaving is an effective solution to this situation, by randomizing the errors before the channel decoders. This paper describes the design and the simulation results of a convolutional...
Recent mobile multimedia innovations evolved for the present society, is a mandatory requirement. To achieve this goal various forums have come forward with several design proposals to suit the group of applications in the Mobile multimedia networks (MMNs). In this regard, a new multi-protocol architecture for the medium access control is required to seamless mobile multimedia networking. Hence a...
Mobile WiMAX, based on IEEE 802.16e, has been developed and is expected to be commercialized in late 2008 or early 2009. To further improve the system performance, spatial division multiple access (SDMA) enabled by adaptive antenna system (AAS) has been considered. In this paper, the relative performance improvement of SDMA based mobile WiMAX is investigated. Results show that AAS-enabled SDMA can...
In this paper, a dynamic scan initiation scheme in a 802.16e network is proposed in order for a mobile station to avoid waste of resources while meeting given handover time. Using statistical analysis on the received signal strength, a mobile station can trigger a scanning process only when a handover is anticipated regardless of random errors in radio propagation environments.
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.