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This paper presents an ultra-wideband (UWB) bandpass filter for UWB applications and notch filter for the purpose of reducing interference from the WLAN (802.11a) when it coexist with UWB radio system. The bandpass filter consists of a hexagonal shaped multiple mode resonator (MMR) with interdigital coupling at both sides. The notch filter consists of four identical open ended stubs nearby the MMR...
Future wireless access will involve a variety of integrated and interworking technologies. Depending on the conditions (e.g., the specific application, the quality of service requirements, the user mobility) each session will be served through the most suited access network; following some event, there will be a variation of the access technology, which is called vertical handover. Although the use...
In this work, we investigate secret key generation from channel states. We point out, by means of a packet-delay-based attack, that observing its own channel states is not the only way an adversary can learn about the channel states of the legitimate communicating parties. The attack suggests that it is not secure to transmit data via the channel whose states generate secret keys. However, not using...
This paper proposes an adaptive bandwidth control scheme for autonomous distributed networks. Based on the consideration that the carrier sense multiple access with collision avoidance (CSMA/CA) is not efficient in terms of throughput due to its strict collision avoidance process, this paper employs a dynamic spectrum control (DSC) in which a certain number of discrete spectra having the highest signal...
Stream Control Transmission Protocol (SCTP) is a new transport layer protocol that is due to replace TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) protocols in future IP networks. Currently, it is implemented in such operating systems like BSD, Linux, HP-UX or Sun Solaris. It is also supported in Cisco network devices operating system (Cisco IOS) and may be used in Windows....
This paper presents experimental results of the implementation of network steganography method called RSTEG (Retransmission Steganography). The main idea of RSTEG is to not acknowledge a successfully received packet to intentionally invoke retransmission. The retransmitted packet carries a steganogram instead of user data in the payload field. RSTEG can be applied to many network protocols that utilize...
The number of multi-homed hosts with multiple network interfaces has been increasing due to cheaper network interface devices and network diversification. Concurrent Multipath Transfer (CMT) using SCTP multihoming is a mechanism that simultaneously transmits data via multiple end-to-end paths compatible with today's network environment. Present studies on CMT have assumed that each path uses a homogeneous...
In this paper, we define and address a new problem that arises when a base station in a broadband wireless network wishes to multicast information to a large group of nodes and to guarantee some level of reliability using Application-layer forward error correction (FEC) codes. Every data block to be multicast is translated into a sequence of packets, from which every receiver must receive at least...
This paper presents results of experiments on characterization of wireless channels inside a tall building in Hung Hom, Hong Kong with the transmitter located atop the DE Block of the Hong Kong Polytechnic University and the channel measurements are made inside a nearby tall residential building. The channel probing signal centered at 1.8 GHz had a bandwidth of 60 MHz. The results were analyzed for...
Orthogonal Frequency Division Multiplexing (OFDM) has emerged as a potential application for the delivery of broad band wireless access. Both DS and FH systems reduce the average power spectral density of a signal and affects by broadband noise. Narrowband interference impacts severely on an FH signal than a DS signal on the same channel. The combination of OFDM with Direct Sequence Spread Spectrum...
As one of the most popular high speed networks, InfiniBand demonstrates several enhanced features, such as RDMA and zero-copy mechanisms, which offer high bandwidth and low latency. Communication stacks IPoIB and SDP (Sockets Direct Protocol) have been proposed on InfiniBand for sockets based applications to take advantage of these features. However, these protocols are inefficient to utilize the...
This paper presents results of channel sounding experiments conducted in two types of corridors in an academic building - one enclosed from the top with recesses for windows on sides and the other open at the top with regularly spaced concrete columns on both sides. The corridors have also openings on either sides leading to hallways. The measurements were made at 1.80 GHz using a channel probing...
Different propagation mechanisms of the transmitted signal take place from the surrounding objects in an indoor scenario. The prediction of the reflection phenomenon is one of the important parameter of the ultra wideband (UWB) channel modeling. This paper presents a model of wave propagation in indoor environments for multiple reflections of UWB signal inside the building wall. The main objective...
In this paper we characterize, in the context of vector space precoding strategies, the degrees of freedom of the parallel three-user interference channel as a function of the channel diversity L. A channel diversity of L is modeled by L independently fading real-valued parallel channels. Our results also apply to the case of parallel complex-valued channels, where the channel matrices Hij ?? Cl??l...
In this paper the design of a high gain low noise amplifier is presented. The LNA was successfully designed to operate over VHF and UHF ranges according to DVB-T specifications. The novelty of the design lies in the achievement of low noise figure across a wide bandwidth and high reverse isolation level. The latter was required in order to integrate the front-end block to a direct-conversion receiver...
The performance of TCP will get worsen in wireless condition which has changing bandwidth, random transmission errors and sharing medium. We present an improved TCP acknowledge mechanism, and provide a new receiver-driven TCP congestion control method which calculates current bandwidth and round-turn time (RTT) at receiver, and deduces next available bandwidth used by the sender according to previous...
Integrated 60 GHz transmitter and receiver GaAs front-end MMICs as well as a packaged transceiver module used for wireless communication link are presented. The data transmission capacity of the chips is examined using binary ASK modulation. A broadband 60 GHz direct carrier quadrature modulator is proposed to be integrated with the transmitter for realizing complex modulation schemes to increase...
This paper deals with the problem of realizing wideband receiver front-ends in downscaled CMOS technologies, which are highly wanted for multi-standard radio receivers and cognitive radio applications. Instead of using many narrowband inductor based receivers, we prefer the use of one wideband receiver with sufficient bandwidth to cover all popular frequency bands up to 6 GHz or even 10 GHz. To relax...
We present in this paper a simulation-based comparison of two single-rate multicast congestion control schemes (TFMCC and PGMCC) against our proposed adaptive smooth multicast protocol (ASMP). ASMP consists of a single-rate multicast congestion control, which takes advantage of RTCP sender (SR) and receiver reports (RR). The innovation in ASMP lays in the "smooth" transmission rate, which...
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