The impact of Doppler frequency hopping on code tracking performance is simulated. A design on pseudonoise (PN) Code Tracking Loop aided by the carrier tracking loop according to the carrier frequency hoping pattern is proposed in this paper. This scheme can be applied in the Telemetry, Tracking, and Commanding system which uses Direct Sequence/Frequency Hopping Spread Spectrum (DS/FH) hybrid s...

In this Letter, a frequency-domain pre-rake transmission is presented for a direct sequence spread spectrum with time division duplex (DSSS/TDD) system under a frequency-selective fading channel. The mathematical relationship between frequency-domain and time-domain pre-rake transmissions is discussed. It is confirmed by the computer simulation that, similar to the time-domain pre-rake transmis...

The performance of an infrared wireless system using direct sequence spread spectrum techniques in multipath channels depends very much on the partial correlation properties of the spreading sequences used. Ideally, a spreading sequence should have zero sidelobes in its periodic and aperiodic auto-correlation functions in order to eliminate multipath dispersion. Unfortunately, no such ideal seq...

Signals with direct spread spectrum are widespread in modern communication and navigation systems. Often for channels which such signals used, significant changes the carrier frequency relation to information speeds of received characteristic. In particular, Doppler shift. Therefore, estimation plays a key role solving problem initial synchronization demodulators spectral broadening. first part...

The authors consider a low-complexity technique for direct-sequence spread spectrum code acquisition. They present performance analysis in Rayleigh fading channels, and with carrier frequency offset in the receiver. They derive analytical expressions for acquisition probabilities, and use them to determine the mean and variance of the acquisition time. It is shown that acceptable performance ca...

In this doctoral thesis, initial code synchronization (i.e., code acquisition) of a direct sequence spread spectrum (DS/SS) system is studied when a smart antenna is used in a receiver. Code synchronization means time synchronization of the used spreading code in the receiver. After an introduction to the topic, a literature review of code acquisition is presented. In addition, a review of the ...

Absti-ucfThis paper investigates the performance of directsequence spread-spectrum packet radio networks in the presence of the near/far problem. It is found that the maximum throughput of the network suffers degradation due to the near/ far problem. However, analysis also shows that, under high traffic conditions, a network with the near/far problem delivers higher throughput than another with...

If direct-sequence spread-spectrum (DS/SS) modulation is employed, the receiver must acquire the chip timing for incoming messages before these messages can be demodulated. If the system or network employs DS/SS multiple access, also known as code-division multiple access (CDMA), the acquisition process is more difficult because multiple messages are transmitted simultaneously and in the same f...

In this thesis we investigate efficient modulation and detection techniques for the uplink (i.e. transmission from mobile to base station) of a DS-CDMA network. Specifically, the thesis contains three parts. In the first part, we focus on the mobile transmitter. In particular, we evaluate and compare the spectral efficiency of two promising variable rate DS-CDMA transmission techniques, multico...