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Statistics that are obtained from the demodulator are used in a direct-sequence spread-spectrum receiver to provide an estimate of the signal-to-noise ratio. We evaluate the applicability to spread-spectrum multiple-access systems of an SNR estimator that was proposed previously for SNR estimation in systems for which the only disturbance is thermal noise. The proposed estimate does not require the...
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...
Frequency-hopping (FH) spread-spectrum anti-jam systems are susceptible to degraded performance by follower jammers, which intercept the transmitted signal, attempt to determine in which of a number of bins the hop is located, and then jam in that bin only. Three factors are addressed that provide some protection against follower jammers. One is the differential time delay between the direct intended...
This paper investigates the invariant detection problem of quadrature phase-shift keying (QPSK) direct sequence spread spectrum (DS-SS) signals in additive white Gaussian noise (AWGN). Using the complex Gaussian mixture signal model and invariance principle, we consider the constant-false-alarm-rate (CFAR) invariant detectors and other sub-optimal invariant tests, including the uniformly-most-powerful-invariant...
As cellular technologies evolve, evaluation of modulation schemes with frequency selective fading is an important consideration. We present methods to evaluate a high data rate DS-SS BPSK reverse link, over a wideband channel, with filters and a modified delayed signature dual finger RAKE. For several years the standard Gaussian approximation has been used to estimate error rate of DS-SS BPSK. We...
This paper considers a synchronous DS-CDMA system where channel state information at the base station is acquired via uplink training and channel feedback is used to provide the terminals with the optimal uplink signatures. We examine the tradeoffs involved in the proportioning of a resource block between training, data, and feedback symbols, with linear (matched filter and minimum mean-square error)...
The mobile user objective system (MUOS) is a geo-satellite communications system derived from the terrestrial cellular WCDMA air interface. WCDMA power control with the long geo-satellite round trip time presents substantial challenges. This paper describes the Point-to-Point power control system with simulation results using time-varying channel models specified by the MUOS program office.
In this paper we propose a novel medium access control (MAC) protocol that provides spectrum agile bandwidth allocation for cognitive radios. Our MAC protocol, called spectrum agile multiple access or simply SAMA, harnesses the frequency agility of cognitive radios in allocating fair and contention free bandwidth under a heterogeneous spectrum environment. SAMA accomplishes its bandwidth allocation...
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...
Wireless sensor networks (WSNs) for tactical environments have been considered as the fundamentals for realizing the future combat system (FCS) supporting network-centric warfare (NCW). Much research related to tactical WSN architecture has been conducted. However, a research about randomly distributed WSNs for military tactical scenarios considering functionalities from bootstrap to data transmission...
Statistics obtained during demodulation are used in a direct-sequence spread-spectrum packet radio network to govern the adjustment of transmitter power within the first few packets of a session. The statistics are also employed by an adaptive transmission protocol to select the modulation parameters and the rate of the error-control code for each packet. The power-adjustment protocol uses the statistics...
The Link-16 is the tactical data link utilized by the Joint Tactical Information Distribution System (JTIDS). The JTIDS system is important due to its wide use by U.S. armed forces, NATO, and other allied militaries. Link-16 is a hybrid frequency-hopped/direct sequence spread spectrum system that utilizes minimum-shift keying (MSK) to modulate the chips, cyclical code-shift keying (CCSK) to modulate...
Iterative signal processing has gained in popularity over the last decade as a way of reducing the effects of interference in a communication system. In previous work, the expectation maximization (EM) algorithm was used to estimate the parameters and data of colliding transmissions in a slow frequency-hopping spread-spectrum (FHSS) system using binary frequency-shift keying (BFSK). As in many FHSS...
The Joint Tactical Information Distribution System (JTIDS) is the Link-16 communication terminal. JTIDS is a hybrid direct sequence/frequency-hopping spread spectrum system and features Reed-Solomon (RS) codes for channel coding. In this paper, the performance with an errors-and-erasures decoder (EED) in the JTIDS receiver is evaluated by a combination of analysis and simulation assuming perfect frequency...
We investigate a transmission scheduling protocol that exploits direct-sequence spread-spectrum (DSSS) modulation to improve the performance of a mobile, ad hoc network. Since DSSS allows for packet capture in the presence of other nearby transmissions, multiple-access interference is less detrimental to network performance. We design a new transmission scheduling protocol that takes advantage of...
The current low throughput of wireless ad hoc networks is greatly caused by the inefficiency of spectrum usage. With distributed scheduling/spectrum allocation, better spectrum efficiency can be achieved. However, most distributed algorithms consider the neighbors' traffic independent of each other and ignore the multi-hop nature of flows, leading to the spectrum wastage and inefficiency. By incorporating...
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