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In this paper, a new technique has been proposed to enhance the impedance bandwidth of the COCO (Coaxial Collinear) antenna. The technique is rotating the coaxial-cable subsections of the antenna. The HFSS is adopted to prove its validity, and the simulated results indicate that the proposed method can widen the bandwidth from 4.2% to 13.5%.
Based on the application of active networks in congestion control, this paper introduces the traditional congestion control policy and analyses their principles and feasibilities. Active networks congestion control policy introduces the active detection and the passive notification mechanism, the random early detect (RED) queue management and the load balance technology based on the traditional congestion...
In order to enhance the survivability of ASON, ASON must provide efficient recovery techniques to guarantee service continuity. This paper proposed a new path restoration algorithm with SRLG constraint to handle single-link failures in GMPLS-Based ASON (RSGA), whose restoration paths are pre-computed and stored in the routing table at each node. This algorithm can efficiently find physically disjoint...
One of the major design issues in heterogeneous wireless networks is the support of vertical handoff. Vertical handoff occurs when a user with a multi-interface terminal changes association from one type of wireless access technology to another while maintaining an active session. It is believed that vertical handoff decision will be based on multiple criteria. In this paper, new handoff criteria...
In this paper, two frequency measurement methods of radar signals are presented at first, and then we focus on the introduction of the FFT frequency measurement and its advantages. After that, combining with the characteristics of the radar signal, we introduce a digital frequency measurement structure for the radar signal, which is based on the generous software radio structure. Finally, we discuss...
A novel printed monopole antenna with two ellipses is proposed to operate from 3 to 11.5 GHz, which is fed by a microstrip line. The antenna is very small in size with dimension of 20 by 24 mm and has an approximate omnidirectional pattern across the major bandwidth. This antenna can be especially applied as the element of ultrawide-band(UWB) antenna arrays for UWB application.
This paper presents the simulation and experimental investigations of a special printed microstrip slot antenna, which is formed by cutting a Log Periodic meandered dipole slot in the microstrip patch. According to the special configuration of the Log Periodic meandered dipole slot, we estimate the new microstrip slot antenna has the similar characteristic of Log Periodic antenna, such as wide bandwidth...
Because most practical communication systems need possessing higher bandwidth efficiency, this article increases the bandwidth efficiency through the two aspects of code rate and modulation mode, that is, by combining CTC(convolutional turbo code) in WiMax protocol with MSK modulation and applying them in the practical communication systems. The simulation result shows the combination of CTC and MSK...
A novel aperture-coupled circularly polarized metallic patch antenna for UHF RFID reader is proposed. In the particular configuration studied, a square patch is placed above a common plane and is fed by means of an aperture-coupled feed network, which adopts sequential rotation technique. The aperture-coupled configuration and multilayer dielectric substrates have the advantage of miniaturizing the...
Multiband ultra wide band(UWB) schemes are proposed in IEEE 802.15 TG3a and terrestrial short-range high-speed UWB communications have been mature. In this paper, the possibility of UWB SATCOM systems using cognitive radio(CR) is considered. CR is an emerging approach for a more flexible usage of the precious radio spectrum resources. UWB technology as one of the transmission techniques suitable for...
Congestion is a natural phenomenon in any network queuing system, and is unavoidable if the queuing system is operated near capacity. In this paper, we study how to set rules of a satellite queuing system so that all the users have self-interest in controlling congestion when it happens. Most of the mechanisms proposed to accomplish this in terrestrial Internet involve complicated packet scheduling...
TCP-friendly rate control (TFRC) is a congestion control mechanism that can compete fairly with TCP while maintaining a much smoother transmission rate. The smoothness is achieved at the cost of responsiveness, which makes it slow to settle down when handed-over to a different network. In this paper we will study how to improve the TFRC performance when the available bandwidth is changed during a...
Research work of dynamic routing based on traffic engineering is investigated firstly and a new routing algorithm with bandwidth guaranteed is introduced for MPLS networks. It is characterized by taking into account network topology, traffic distribution condition and available bandwidth of links. In this algorithm traffic engineering objective can be translated into path constraint, which combines...
To investigate the blind symbol rate estimation of any linear base-band digital modulation scheme with square root raised cosine filter, an algorithm based on cyclic correlation and Haar wavelet transform estimator is proposed. First we use FFT to estimate the bandwidth roughly. Then we set the sampling frequency and range scale of wavelet transform according to bandwidth. Using the signals filtered...
As we know, fast mobile IPv6 (FMIPV6), hierarchical mobile IPv6 (HMIPV6) and fast-hierarchical mobile IPv6 (F-HMIPv6) are enhancements to the standard mobile IPv6 (SMIPV6) protocol for reducing handover latency and data loss, and for localized mobility management. But, some problems still remain, bandwidth within a MAP region is not satisfying yet and lots of IP addresses in HMIPV6 and F-HMIPv6 scheme...
A novel double band ceramic fractal antenna working at 2.4 GHz and 5.8 GHz is designed for the minimization requirement of RFID tag antenna. The simulated results show that when VSWR (vertical standing wave ratio) is less than 2, the antenna absolute bandwidths are up to 0.39 GHz and 1.85 GHz in 2.4 GHz and 5.8 GHz respectively , with relative bandwidths up to 15.20% and 35.82% respectively,. Considering...
Although UNB is scorned by the advanced in the art, a new view of understanding it is presented through power spectra and bandwidth analysis. Bandwidths of UNB modulation schemes such as VMSK are analyzed by deducing their power spectrum analytical forms. Both mathematical analysis and simulation results show that UNB modulation schemes cannot attain high bandwidth efficiency. A conclusion is reached...
With the development of multimedia Web sites and increasingly diversified services, there is a growing demand for different levels of quality of service (QoS) on scalable Web servers to meet changing resource availability and to satisfy different client requirement. Most Web servers in practical use a queuing policy based on the best effort model, which employs the first-come-first-service (FCFS)...
In IEEE 802.16e mobile WiMAX system, since mobile stations (MSs) send bandwidth request (BR) messages to base station (BS) during contention period when they need uplink channel to transmit data in the case of multicast polling or broadcast polling, the uplink performance is affected by the size of the contention period in the uplink subframe. The access delay will be increased if the size of the...
IEEE 802.16 standard supports two topologies: Point-to-multipoint (PMP) and Mesh. In this paper, Optimal Base Station Scheduler of IEEE 802.16 Mesh mode is proposed. We propose Optimal Base Station Scheduler (OBSS) that makes scheduling decisions based on the time required of each Mesh Subscriber Station (MSS) and the granting time given to all MSSs in the network. Different services should deal with...
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