Matti Raustia

Method selection diversity approach to interference suppression

The interference suppression problem has introduced a large variety of suppression algorithms. A large majority of cases, the proposed algorithms are targeted against a specific type of interference and fail to suppress other types of interfering signals. We propose a SINR estimator based method to select between several relatively simple interference suppression methods to overcome this problem. We combine three suppression algorithms, namely CME-notch-, RLS- and polar-suppression filters. The approach is to use a DPSK-modulated hybrid direct sequence (DS) frequency hopping (FH) system model, but the suppression method is also applicable to pure DS-systems or MC-CDMA-systems. The performance results show that this approach has the capability of operating under a wide range of interference parameters.

Implementation of spectrum sensing on wireless open-access research platform

Opportunistic spectrum usage is one application of the so called cognitive communication systems that enables efficient spectrum usage in future wireless communication systems. One of the key features in opportunistic spectrum usage is a spectrum opportunity estimation method. Energy detection has the benefit that knowledge about the licensed users is not required. In this paper, energy detection method called the localization algorithm based on double-thresholding (LAD) is implemented on the wireless open-access research platform (WARP). The simulation measurements proved that the implementation was done correctly. Results included important information of consumed FPGA resources and processing latencies for the LAD method implementation.

Frequency hopping mobile ad hoc and sensor network synchronization

The time synchronization is one of the main issues in frequency hopping mobile ad hoc networks (FH MANET) or time synchronous wireless sensor networks (TWSN). In the former case a network wide time reference is needed in FH code phase synchronization and in the latter case, e.g., in time stamping of the sensed phenomenon. Herein, a distributed decision making method (s) that solves the problems considering initial time synchronization, FH code phase synchronization, late-entry nodes and subnetwork merging cases of tactical FH MANETs and TWSNs is proposed. One of the starting points is a recently developed robust control channel method that enables the nodes to exchange the necessary synchronization messages prior the frequency hopping synchronism, i.e., out-of-phase. The proposed method is master free and based on node identifiers and local information that a node collects from the surroundings, namely local density and local data-activity. Simulation results are given that prove the functionality and the potentiality of the proposed methods.

FH-Code Phase Synchronization in a Wireless Multi-Hop FH/DSSS Adhoc Network

A military ad hoc network has to have a good LPI (low probability of intercept) and LPJ (low probability of jamming) capabilities. These requirements can be met by using a combined frequency hopping/direct sequence (FH/DS) spread spectrum (SS) system. Due to characteristics of an ad hoc network, the network wide synchronization has to be achieved distributely, which makes especially FH-code phase synchronization a challenging task. Here, we present an FH-code phase synchronization method suitable for very long FH-codes and unknown code-patterns. The synchronization data is spread using a specific synchronization DS-code (DS(s)-code), i.e., the control channel is in the code-space. Synchronization messages are broadcasted periodically to allow single nodes or subnetworks with different FH-code phases to synchronize as a one network. Divergent synchronization hops are not needed, thus providing excellent LPI & LPJ properties. In order to achieve and maintain a common FH-code phase a network time synchronization algorithm has to be used. Simulations of an ad hoc network with a simple network time synchronization algorithm has been made and the results are presented in this paper. The simulations prove that the chosen algorithm can maintain a common timing at a satisfactory level as long as the connectiveness in a network is tolerable. The effects of clock drift and the synchronization message size have also been studied

Demonstration of distributed TDMA MAC protocol implementation with OLSR on linux enriched WARP

In this demo we present software extension for the Wireless open Access Research Platform (WARP), named as Linux Enriched WARP (LE-WARP). The objective of the LE-WARP is twofold. First, to make the WARP more independent from external systems, e.g., need for external PC to be part of the WARPs network layer. This is achieved by introducing Linux OS to the platform. The second objective is to utilize a secondary network for coordinated statistics gathering from the WARPs. To demonstrate these features of LE-WARP, a prototype implementation consisting of distributed Time Division Multiple Access (TDMA) based MAC protocol with distributed time synchronization algorithm and the Optimized Link State Routing (OLSR) protocol for ad hoc networks is presented. The demonstration highlights the LE-WARPs ability to monitor the multihop test network consisting four nodes while utilizing the presented prototype implementation.

Synchronization of FH/DS Signal with Interference Suppression Diversity

The interference suppression problem has introduced a large variety of suppression algorithms. A large majority of the proposed algorithms is targeted against a specific type of interference signal and fail to suppress other types of interfering signals. In this paper we examine a earlier proposed SINR estimator based method to select between several relatively simple interference suppression methods. In this paper we examine the applicability and performance of the approach in timing synchronization. In this study the interference suppression selection is made between pure matched filter, CME-notch, and Polar-suppression filters. The approach in the paper is to use a DPSK-modulated hybrid direct sequence (DS) frequency hopping (FH) system model but the suppression method is also applicable to pure DS-system or MC/CDMA-system. The performance results show that this approach has the capability to operate under wide range of interference parameters

New tactical radio systems in Finland

This article describes the developments in the field of emerging new military radio systems to be deployed in Finland, Finnish software radio programme is the tool to deploy these new systems. The demonstrator platform, that is being build, is a software defined radio wherein the developed wideband applications can be demonstrated. The systems that will be deployed on the demonstrator platform - tactical radio communication system (TRCS) and national tactical positioning system (NTPS) - are introduced in this paper. Brief introduction of the adaptive antenna system to be applied in the demonstrator is also given

Effects of Rayleigh fading to method-selection in interference suppression

The interference suppression problem has introduced a large variety of suppression algorithms. A large majority of the proposed algorithms is targeted against a specific type of interference signal and fail to suppress other types of interfering signals. In this paper we examine a earlier proposed SINR estimator based method to select between several relatively simple interference suppression methods in Rayleigh fading channel. In this study the interference suppression selection is made between CME-notch-, RLSand polar-suppression filters. The approach in the paper is to use a DPSK-modulated hybrid direct sequence (DS) frequency hopping (FH) system model but the suppression method is also applicable to pure DS-system or MC/CDMA-system. The performance results show that this approach has the capability to operate under wide range of interference parameters and Rayleigh fading

Mvdr-Based Smart Antenna Mac for Manets

Capacity and interference suppression capabilities of mobile ad hoc networks (MANETs) can be greatly enhanced when directional antennas are used. The main capacity gain is achieved because of the spatial reuse which enables simultaneous connections even in dense networks. If conventional directional antennas are used, the directioning is limited by mechanical properties of the antenna steering system. adaptive antennas (a.k.a. smart antennas) offer a great advantage because of the near instantaneous modification of the radiation patterns and possibilities to suppress intentional jamming. The use of directional antennas presents a severe hidden node problem if no special methods in the MAC layer are used. We present a MAC method which can take advantage of the adaptive antenna system, needs no dedicated control channel and can suppress network self-interference and intentional jamming. This work is a continuation of previously presented bi-code channel access (BCCA) MAC method

Combining method for FH-DS communications

Large number of interference suppression methods has been presented during the years of active spread spectrum research. Most of the methods presented and all the practical methods are tailored to suppress some specific interference waveform, which reduces their usability. Seldom presented method for rejecting the effects of jamming in frequency hopping direct sequence systems is diversity, which offers significant gains in jamming tolerance. In this paper, we present a combining method utilizing signal-to-interference-and-noise ratio (SINK) estimates, which can be used to combat interference in frequency hopping direct sequence military communications. The method presented in this paper combines the good sides of both selection combining and equal gain combining.