The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Multiband tactical communication modems must employ different waveforms to meet various demands in quality and nature of data. Range maximization, high data throughput and power conservation requirements are usually not fulfilled by a single waveform. To effectively deliver tactical multimedia data including coded audio, text, video, map and navigation information using radio, multiple choice of frequency...
In this paper, we propose a novel sidelobe suppression approach for cognitive radio systems employing orthogonal frequency division multiplexing (OFDM) transmission. OFDM is a promising solution for future overlay wireless access due to its high data rate and flexibility. However, OFDM and its variants employ sinc-type pulses in representing the symbols transmitted over all subcarriers during one...
This paper proposes a low-complexity equalizer for orthogonal frequency division multiplexing (OFDM) systems under time-varying frequency-selective fading environments. The equalization uses suboptimum maximum likelihood sequence estimation (MLSE) in cooperation with semi-blind linear prediction (SBLP) in the estimation of the channel frequency responses. When the number of pilot subcarriers is far...
This paper investigates the issue of resource allocation in multicarrier wireless networks, where users have a choice between multiple service providers. We investigate the feasibility of modeling the allocation problem as a probabilistic voting game. In other words, competing transmitters are modeled as candidates in an election, while the receivers form the electorate. The specific example analyzed...
In this paper we formulate OFDM signals based on explicit pulse shaping filtering. A rectangular pulse in time domain for shaping filtering is most often used, but it has SNR loss compared to a shaping filter with a brick-wall frequency domain filter since in practice both require guard time or guard band. Our formulation of OFDM signal based purely on shaping filter may provide a common platform,...
Most communication styles in tactical networks are one-to-many communications, which is multicast transmission. Recently, tactical networks has been evolving to Ad-Hoc-like distributed networks with OFDM-based Wideband Networking Waveform (WNW). In this paper, novel rate-adaptive multicast transmission method over OFDM-based wireless networks is proposed. Transmission rate for wireless multicast over...
If binary signaling is used in an n-channel OFDM link, the maximum possible bit rate is n bits per OFDM symbol duration. We show a simple scheme based on selective channel use that increases this capacity by nearly 60%. By using only k channels out of the n, we show how to use the choice of the k channels as an additional auxiliary channel. For proper choice of parameters, the information transferred...
In this paper, we propose two modified proportional fair scheduling algorithms for multiuser multicarrier systems. Compared to the existing proportional fair scheduling algorithms, our proposed algorithms are devised to support the delay constraint for the real-time applications as well as to guarantee a certain level of fairness. The simulation results show that the proposed scheduling algorithms...
OFDM offers high bandwidth efficiency and low receiver equalization complexity; consequently OFDM is growing in popularity for adoption into robust high data rate services in wireless multipath channels. While these advantages have been proven for many wireless applications (including numerous IEEE wireless standards), one potential disadvantage of OFDM is that it exhibits high peak-to-average power...
A new and novel spread spectrum approach employing orthogonal frequency coding (OFC) for a SAW sensor/tag is presented. This approach provides ultra wide band operation, multi-device interrogation, and reduced loss as compared to conventional SAW CDMA approaches. A traditional SAW CDMA tag consists of an input transducer that launches a surface wave on the substrate towards an array of single frequency...
Multiple antenna systems have been shown to provide significant performance improvements for network nodes; however, the vast majority of nodes in military networks will be limited to single channel devices due to mobility (size and power) and ease of use considerations. In this paper we apply a new joint synchronization-pilot sequence (JSPS) optimization design technique to multiple transmitter OFDM...
Peak-to-average power ratio (PAR) reduction algorithms have been thoroughly studied for single system multicarrier signals that tend to have low power efficiency. However, an emerging application for PAR reduction, namely asynchronous multi-plexed signals, has not been examined. This paper frames the problem arising in modern base stations where multiple frequency-division OFDM waveforms are multiplexed...
Tactical mobile ad hoc networks (MANETs) have a continued growth in bandwidth demand mainly driven by the introduction of new user services and applications. Everything over IP is one of the main requirements of the next generation tactical MANETs. As part of an initial investigation to provide enhanced tactical IP networking capabilities, an adaptive VHF/UHF system that attempts to satisfy the mobility,...
This paper will present a comparison of the basic resource definition in an OFDMA MAC/PHY layers for WiMAX and the TDMA/OFDM MAC/PHY. The majority of current radios in development for the US Army use TDMA/OFDM. This comparison will be conducted by defining and discussing the basic unit of system resource, e.g. the ??slot??. Following the protocol comparison, some simulation results comparing the performance...
In this paper, we present three novel priority-based spectrum allocation techniques for enabling dynamic spectrum access (DSA) networking for non-contiguous orthogonal frequency division multiplexing (NC-OFDM) transmission. With each communication link in the network possessing a specified pair of bit error rate (BER) and throughput requirements for supporting a specific application, the proposed...
The robustness to jamming signal is an important property for military communication systems. Some previous work has shown that the frequency domain code division multiplexing (CDM) efficiently rejects the interference. In general, however, the jamming signal has higher power than ordinary interference which leads to insufficient jamming rejection performance of these schemes. To mitigate this insufficiency,...
In this paper, we investigate the information theoretical performance of a cooperative OFDM (orthogonal frequency division multiplexing) system with imperfect channel estimation. Assuming the deployment of a training-aided channel estimator, we derive a lower bound on the achievable rate for the cooperative OFDM system with amplify-and-forward relaying over frequency-selective Rayleigh fading channels...
OFDM signals suffer significant distortion when transmitted through practical power amplifiers. In this paper, we examine the channel estimation performance of OFDM systems under channels with such a peak power constraint. We consider the effects of null edge subcarriers added for spectral shaping and derive the Crame??r-Rao bound for channel estimation performance of this system both with pilot power...
It is a well known fact that orthogonal frequency division multiplexing (OFDM) suffers from high peak to average power ratio (PAPR). The nonlinear distortion introduced by an OFDM signal through practical amplifiers can further degrade the system performance. Due to the limited bandwidth in the radio frequency spectrum, it is impossible that wireless communication systems can operate in an environment...
Interference alignment (IA) has been shown to achieve linear sum capacity growth, at high SNR, with the number of users in the interference channel by cooperatively precoding transmitted signals to align interference subspaces at the receivers. The theory of IA was derived under assumptions about the richness of the propagation channel; practical channels do not guarantee such ideal decorrelation...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.