Keying

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

Simulation of bit error performance of FSK, BPSK, and pi /4 DQPSK in flat fading indoor radio channels using a measurement-based channel model

Abstract: The results of a simulation study that provides insight into the simulation methodology and bit error rate (BER) performance of frequency-shift keying (FSK), binary phase-shift keying (BPSK), and pi /4 differential phase-shift keying ( pi /4 DQPSK) in flat fading channels inside open plan buildings are presented. A detailed measurement-based propagation channel model, SIRCIM (simulation of indoor radio channel impulse response models), which generates over 1000 closely spaced baseband equivalent complex impulse responses for a mobile radio operating at 1.3 GHz and traveling over a 1-m path, is used. The small-scale channel model, the communication system models used in the analysis and the methods used to predict BER are described. The channel simulator and the systems models have been thoroughly tested, and results from average instantaneous BER simulations are shown. The BER performances of the modulation techniques are presented. It is found that BPSK offers between a 2.8-dB and 3.0-dB improvement over pi /4 DQPSK, although the latter offers a 3-dB increase in capacity for a given spectrum allocation. >

A wireless internet access method and system

Abstract: A wireless Internet access system (100) and method supports the transmission and reception of multiple types of traffic between mobile subscriber units (105, 106) and existing networks (120). A frame structure is used that can support the transmission of multiple types of traffic and adapt to changes in the traffic types needed and the amount of data for a particular traffic type. In addition, data transmission is performed using orthogonal frequency division multiplexing and differential phase shift keying to avoid inter-symbol interference. Receiving units in the mobile subscriber units (105, 106) and existing networks (120) include antenna arrays to provide a multipath transmission.

Hierarchical deterministic pairwise key predistribution scheme

Abstract: A security system for a hierarchical network (10) includes L hierarchical levels each corresponding to a security domain level (16), and a plurality of local network nodes (A, B,..., Z). A keying material generator (24) generates a set (30) of correlated keying material for each network node. Each set (30) of keying material is composed of L sub-sets (32) of keying material one for each security domain level (16). A set up server (34) distributes the generated sets (30) of keying material to each network node (A, B,, Z) to enable the network nodes (A, B,, Z) to communicate with one another at a security domain of a hierarchical level k by a use of a corresponding sub-set (32) of the security keying material.

Spatial Modulation for Molecular Communication

Abstract: In this paper, we propose an energy-efficient spatial modulation based molecular communication (SM-MC) scheme, in which a transmitted symbol is composed of two parts, i.e., a space derived symbol and a concentration derived symbol. The space symbol is transmitted by embedding the information into the index of a single activated transmitter nanomachine. The concentration symbol is drawn according to the conventional concentration shift keying (CSK) constellation. Befitting from a single active transmitter during each symbol transmission period, SM-MC can avoid the inter-link interference problem existing in the current multiple-input multiple-output (MIMO) MC schemes, which hence enables low-complexity symbol detection and performance improvement. Specifically, in our low-complexity scheme, the space symbol is first detected by energy comparison, and then the concentration symbol is detected by the equal gain combining assisted CSK demodulation. In this paper, we analyze the symbol error rate (SER) of the SM-MC and its special case, namely the space shift keying based MC (SSK-MC), where only space symbol is transmitted and no CSK modulation is invoked. Finally, the analytical results are validated by computer simulations, and our studies demonstrate that both the SM-MC and SSK-MC are capable of achieving better SER performance than the conventional MIMO-MC and single-input single-output MC (SISO-MC) when the same symbol rate is assumed.

Tamper-resistant television signal scrambling

Abstract: A method and apparatus for blocking the reception of a subscription television program while substituting a replacement program at a blocked receiver, provide security against detuning an unauthorized receiver to receive the subscription program. A security carrier signal is provided in a subscription television signal at the frequency of the audio carrier of the lower adjacent channel and is alternately amplitude modulated with bursts from first and second interference frequencies at a third or keying frequency. The television signal also includes an interfering carrier signal intermediate the audio and video carriers in the channel and the interfering carrier is modulated with a substitute television program. When a receiver is properly tuned to the channel, the security carrier has no effect on reception and either the subscription or substitute program is received, depending on whether the receiver is authorized or not. Should an attempt be made to receive the subscription program in an unauthorized receiver by detuning the receiver, the security carrier interferes with or blocks video reception in the detuned receiver and the modulation of that carrier produces a moving visual pattern which is extremely annoying to a viewer.