Keying

About: Keying is a research topic. Over the lifetime, 6598 publications have been published within this topic receiving 82943 citations.

Method and apparatus for secure content delivery over broadband access networks

Abstract: A system for secure delivery of on-demand content over broadband access networks utilizes a pair of servers and security mechanisms to prevent client processes from accessing and executing content without authorization. A plurality of encrypted titles are stored on a content server coupled to the network. An access server also coupled to the network contains the network addresses of the titles and various keying and authorization data necessary to decrypt and execute a title. A client application executing on a user's local computer system is required to retrieve the address, keying and authorization data from the access server before retrieving a title from the content server and enabling execution of the title on a user's local computer system.

Unified analysis of certain coherent and noncoherent binary communications systems

Abstract: A general result is presented for the error-rate performance of common binary signaling-detection techniques for reception in additive Gaussian noise, including {\em all} possible conditions of nonorthogonality of signal, and correlations in the noise processes. These forms include frequency-shift keying with non-coherent detection, generalized to {\em all} noncoherent detection systems utilizing two basic waveforms, and phase-shift keying with a noisy reference signal, generalized to {\em all} coherent detection systems utilizing a single basic waveform. The unified result is achieved by exploiting a fundamental relationship between noncoherent and coherent operation. Also, some useful and not widely-known mathematical techniques involving the Q function are presented and utilized in the derivations.

Comparison of return-to-zero differential phase-shift keying and ON-OFF keying in long-haul dispersion managed transmission

Abstract: Performance of return-to-zero (RZ) differential phase-shift keying (DPSK) in ultralong-haul dense wavelength-division-multiplexing (WDM) dispersion managed transmission is studied experimentally and compared with conventional ON-OFF keying (OOK) in a 10-Gb/s system. We show that, while OOK out-performs phase-shift keying in a low spectral efficiency WDM system, the performance of DPSK is comparable to OOK at 10-Gb/s transmission with a spectral efficiency of 0.2. Furthermore, RZ DPSK is advantageous in a high spectral efficiency (e.g., >0.4) system and our numerical simulation results show superior performance of DPSK at 10 Gb/s with 25-GHz channel separation.

The phase of a vector perturbed by Gaussian noise and differentially coherent receivers

Abstract: Some results are presented regarding the asymptotic distribution of the phase of a vector perturbed by Gaussian noise. It is shown that for large signal-to-noise ratio, the asymptotic distribution of the phase is of the Tikhonov type. This framework is then used for the synthesis of differentially coherent receiver structures, one for M-ary phase-shift keying (MPSK) and the other for minimum-shift keying (MSK). The first structure bridges the performance gap between coherent and differentially coherent demodulation of MPSK. The MSK receiver uses matched filtering with differential demodulation. >

Generalized Space-Time Shift Keying Designed for Flexible Diversity-, Multiplexing- and Complexity-Tradeoffs

Abstract: In this paper, motivated by the recent concept of Spatial Modulation (SM), we propose a novel Generalized Space-Time Shift Keying (G-STSK) architecture, which acts as a unified Multiple-Input Multiple-Output (MIMO) framework. More specifically, our G-STSK scheme is based on the rationale that P out of Q dispersion matrices are selected and linearly combined in conjunction with the classic PSK/QAM modulation, where activating P out of Q dispersion matrices provides an implicit means of conveying information bits in addition to the classic modem. Due to its substantial flexibility, our G-STSK framework includes diverse MIMO arrangements, such as SM, Space-Shift Keying (SSK), Linear Dispersion Codes (LDCs), Space-Time Block Codes (STBCs) and Bell Lab's Layered Space-Time (BLAST) scheme. Hence it has the potential of subsuming all of them, when flexibly adapting a set of system parameters. Moreover, we also derive the Discrete-input Continuous-output Memoryless Channel (DCMC) capacity for our G-STSK scheme, which serves as the unified capacity limit, hence quantifying the capacity of the class of MIMO arrangements. Furthermore, EXtrinsic Information Transfer (EXIT) chart analysis is used for designing our G-STSK scheme and for characterizing its iterative decoding convergence.