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Reed Solomon (RS) forward error correction (FEC) coding in conjunction with M-ary hyper phase-shift keying (MHPSK) and soft decision decoding is considered in order to improve the robustness of a high spectral efficiency, non-linear satellite communications link. In this paper, a system that utilizes RS encoding of the information symbols which are then transmitted with MHPSK is evaluated in terms...
In this work, we consider a multi-hop cognitive radio network with multiple flows. The challenges induced by the random behaviors of the primary users are investigated in a stochastic network utility maximization framework. To fully utilize the scarce network resource, we propose an optimal traffic splitting scheme for each source node to explore multiple paths effectively. In addition, the algorithm...
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...
A critical aspect of spectrum sensing involves determining the number and type of transmitters in the band of interest. We present a technique that exploits a combination of temporal and frequency-based analysis to enable significantly more accurate frequency offset measurements than would be possible with frequency domain measurements alone, thus enabling improved RF fingerprinting for 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...
Parallel efforts are underway in the frequency management and the radio and waveform design communities to support data communications over HF radio channels wider than conventional 3 kHz allocations. In this paper, we analyze the potential performance of such ??wideband?? HF data channels as a function of spectrum allocation, coding, channel characteristics, and waveform overhead.
With the phenomenal success and productivity of terrestrial networks, there is interest in using similar technology in space. For instance, there currently are projects aimed at deploying Internet routers in space. In this paper, we discuss the general concept of connecting a cluster of satellites with a local area network. We discuss the advantages and challenges of such a network, as well as possible...
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...
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...
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...
Ultra-wideband (UWB) has been considered a viable and an innovative solution for future short-range high-speed wireless communication systems. One of the big concerns for UWB devices to function properly is the narrow band interference (NBI) issue, which must be carefully studied. For this purpose, the performance of UWB communication system over indoor Lognormal fading channel in the presence of...
In this paper, we provide a feasibility analysis of non-contiguous orthogonal frequency division multiplexing (NC-OFDM) transceivers based on different operating configurations. The selection of these configurations conform to the constraints defined by the spectral masks of the Federal Communications Commission's (FCC), such as out-of-band radiation. Actual spectrum measurement data collected from...
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