This paper presents an overview of ultrawideband (UWB) communications systems, i.e., systems with very large relative and/or absolute bandwidth. The large bandwidth and low power spectral density mandated for UWB systems allows to use them as overlay over existing (legacy) systems, i.e., they can be used in the same frequency range as existing systems without causing undue interference. We also...

The problem of communication among nodes in an extended network is considered, where radio power decay and interference are limiting factors. It has been shown previously that, with simple multi-hopping, the achievable total communication rate in such a network is at most Θ( √ N). In this work, we study the benefit of node cooperation in conjunction with multi-hopping on the network capacity. W...

In modulated scattering antenna array (MSAA) system it has at the receiver side encountered low levels of scattering signals [1, 2] and interferences in addition to the desired signal. In this paper, we propose to utilize the frequency hopping scheme to improve the performance of scattering signals under the influence of narrow band strong interferences. From the numerical results, it concludes...

This paper investigates spectrum sharing issues in the unlicensed industrial, scientific, and medical (ISM) bands. It presents a radio frequency measurement setup and measurement results in 2.4 GHz. It then develops an analytical model to characterize the coexistence interference in the ISM bands, based on radio frequency measurement results in the 2.4 GHz. Outage performance using the interfer...

We present a cognitive spectrum access solution for FH-CDMA ad hoc networks. Building on a cluster-based split phase multi-channel MAC protocol, we propose a mechanism for local interference avoidance through distributed hopset adaptation. Its goal is to identify and substitute channels not suitable for reliable communication. Substitution rules replace channels by locally unused hopsets. This ...

Orthogonal Frequency Division Multiplexing (OFDM) is a multi-carrier modulation scheme that provides efficient bandwidth utilization and robustness against time dispersive channels. This paper deals with the basic system model for OFDM based systems and with self-interference, or the corruption of desired signal by itself in OFDM systems. A simple transceiver based on OFDM modulation is present...

In today’s cellular networks it becomes harder to provide the resources for the increasing and fluctuating traffic demand exactly in the place and at the time where and when they are needed. Moreover, frequency planning for a hierarchical cellular network, especially to cover indoor areas and hot-spots is a complicated and expensive task. Therefore, we study the ability of hierarchical cellular...

In order to reduce the optical beat interference (OBI) in an optical frequency-hopping code division multiple access (FH-CDMA) network, we propose applying coherence multiplexing (CM) technique into the optical FHCDMA network. Since the CM technique achieves multiplexing by using time delays exceeding the coherence time of the light sources, crosstalk between CM channels depends on a space of d...

The aim of this article is to quantify and analyze mutual interference of Frequency Hopping with Collision Avoidance (FH/CA) systems. The FH/CA system is a frequency hopping system where stations select the least jammed channel from several possible before the next jump. The article describes a mathematical model that allows determining the upper limit of the probability of collision of multipl...

The medium-access control (MAC) protocols for wireless networks proposed or implemented to date based on collision-avoidance handshakes between sender and receiver either require carrier sensing or the assignment of unique codes to nodes to ensure that intended receivers hear data packets without interference from hidden sources (i.e. IEEE 802.11). We present and analyze a receiver-initiated ch...