Time-hopping (TH) communication techniques have gathered increasing attention since the introduction of ultra-wide-band impulse-radio, by Scholtz, in 1993. In these systems, the design of TH sequences is a critical point, since they constitute the only source of diversity that protects the transmitted signal from the interference caused by multipath and by the presence of other users. Moreover,...

This paper presents a new subband allocation scheme for multiuser OFDMA systems. Adaptive OFDMA systems have focused on adapting the allocation of subcarriers and power to the instantaneous channel conditions of all users. Using frequency hopping pattern in OFDMA system allow users to minimize intercell and intracell interference, and perform frequency diversity. In contrast to conventional FH-...

Bluetooth is a wireless technology that enables devices to communicate in the 2.4 GHz industrial, scientific, and medical (ISM) license free frequency band. Bluetooth avoid the interference by using a frequency hopping (FH) spread spectrum technology with hop rate of 1600 hops per second. This paper studies schemes to avoid local interference observed by the devices. It tries to come up with a ...

When the up-link frequency band repeated by a communications satellite is hopped in a periodic manner, when users are divided so that a group of them can transmit only when a particular frequency band is repeated, and when message arrivals for one user are independent of message arrivals for any other user, the users in a group are independent. When the frequency hopping is done in a pseudorand...

Ranging with energy detectors enables low-cost implementation. However, any interference can be quite detrimental to range accuracy. We develop a method that performs nonlinear filtering on the received signal energy to mitigate multiuser interference (MUI); and we test it over time-hopping and direct sequence impulse radio ultrawideband signals. Simulations conducted over IEEE 802.15.4a reside...

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. We present and analyze a new collision-avoidance MAC protocol tha...

Frequency-hopping communication has the capability to resist narrowband interference, which is in direct proportion to the hopping rate. In frequency-hopping system, interference signals exist in partial de-hopping frequency-hopping signals, equivalent to time-varying interference signals existed in the frequency-hopping signals. Through integrating the diversity combining techniques of fast fr...

Wireless networking occurs on a shared medium which renders communication vulnerable to disruption from other networks, environmental interference, and even malicious jammers. The standard solution to this problem is to deploy coordinated spread spectrum technologies that require pre-shared secrets between communicating devices. These secrets can be used to coordinate hopping patterns or spread...

This report is a tutorial introduction to spread spectrum communication systems, and it should be accessible for a reader who has basic knowledge of digital modulation and channel coding. The authors have chosen to present the more advanced topics in the report from a signal space and channel coding point of view. While other approaches are certainly possible, the authors feel that the chosen a...

In this paper, we present a RF directional modulation technique using a switched antenna array for physical layer secure communication. The main idea is that a switching scheme of the switched antenna array is designed according to a spreading sequence for the purpose of spreading spectrum of the transmit signal. The transmit signal is associated with the spreading sequence and the direction of...