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In this paper, three reverse link access protocols (AP) enabling discontinuous transmission (DTX) in DS-CDMA personal communication systems are introduced and discussed. The first protocol is synchronous (SDTX-AP), and it uses a so-called synchronous reservation channel to accommodate access requests in a time slotted frame structure. The second uses an asynchronous approach (ADTX-AP) with a spread slotted ALOHA protocol for access requests; access request messages consist of a synchronizing preamble and a user identifier appendix. The third one employs a synchronous structure of overlapping slots, offset in time by a minimum interval (mini-slot) necessary to enable resolution of overlapping access probes sent by different mobile users (MSDTX-AP). Instead of using different spreading codes for different mobile transmitters, all transmitters are assigned the same spreading code to send their access request messages on the access reservation channel. Analysis considers the mean access delay and throughput of the protocols in a multipath fading channel. Numerical results indicate that at high values of offered traffic of access requests mean access delays of ADTX-AP and SDTX-AP are comparable. The mean access delay for the MSDTX-AP depends on the number of minislots or users within each frame, but its throughput is much higher than that of either SDTX-AP or ADTX-AP.

Combined error correction and detection techniques, or hybrid automatic-repeat-request (ARQ) schemes with negative acknowledgment are considered for highly reliable reverse link data transmission in direct sequence code division multiple access (DS-CDMA) personal communication systems. The proposed selective repeat hybrid ARQ scheme employs an inner convolutional code for error correction and an outer shortened BCH code for error detection. Each negative acknowledgment message contains all packet sequence numbers that have been detected in error, and it is both error-correction and error-detection encoded. Accepted packet error rate and throughput are derived as a function of the error correction encoded frame error rate. An optimum signal-to-interference ratio (SIR) assignment maximizing the system's capacity is also found. A comprehensive simulation is conducted to evaluate performance of the data transmission system. Analysis and simulations show that by applying the proposed type I hybrid ARQ scheme with properly selected system parameters, virtually error free and highly efficient data transmission in CDMA personal communication systems is possible.

Introduction: for realizing detection of drowsiness, a method based on Tsallis entropy of EEG signal is proposed. Materials and Methods: EEG signals with bipolar montage C4-P4 and T4-T6 were collected from 20 healthy subjects during wake and drowsiness. After four kinds of EEG rhythms were extracted, the each rhythm complexity for the EEG signals was analyzed with Tsallis entropy. Results and Discussion: the results show that the Tsallis entropy of EEG theta rhythms either C4-P4 or T4-T6 in wake is obviously higher than drowsiness. So the drowsiness could be reliably detected in real-time by the Tsallis entropy of theta rhythm on C4-P4 or T4-T6.

The paper considers optimal forward link power allocation for data transmission in DS-CDMA systems. Acceptable quality voice communications in DS-CDMA can be achieved through the application of the forward error correction (FEC). Due to stringent requirements on signal delay, no retransmission is allowed in voice only systems. Highly reliable data transmission over wireless channels, however, can be achieved with hybrid automatic-repeat-request (ARQ) schemes. The average power allocated to data users then needs to be calculated as the actual link transmitted power times the average number of times that a data packet must be transmitted before it is accepted. Since a base station's total power available to mobiles is limited, there is an optimum power allocated to every data user in the cell, which maximizes the system capacity. The optimal power allocation can be described as the stochastic nonlinear programming optimization problem. Numerical results are presented to illustrate the problem. The powers allocated to data users are location dependent, but the numerical results demonstrate that the mean signal-to-interference ratio (SIR) is location independent when the optimal power allocation is achieved.

Capacity analysis of a multi-service CDMA communication system when both continuous and discontinuous transmission schemes are employed, is presented. Data messages treated in this paper include long ones for which closed loop power control can be implemented, and short ones for which only open loop power control is feasible. The effect of the discontinuous transmission's overhead on the system Erlang capacity is evaluated. For data transmission, when a negative-acknowledgment ARQ protocol is employed, its impact on the call admission control (CAC) is also investigated. The concept of equivalent bandwidth has been introduced which makes the analysis of an interference-limited system similar to that of a bandwidth-limited system without fixed channel assignment. The proposed CAC algorithms can be employed in a system supporting multi-rate data services. Simulations are conducted to validate the analysis.

This paper considers two types of digital matched filter-based synchronizers. One is applied with biphase spreading, and the other with quadri-phase spreading. The synchronizers are primarily designed for application on reverse links of the IS-95 type systems, but with minor modifications they can also be used in other DS-CDMA systems. Probabilities of correct acquisition and false alarm for both Gaussian and Rayleigh fading channels are derived. The differential approach is considered to reduce the number of required operations. Numerical results are presented when a specially designed packet synchronization preamble is used, and the mean acquisition time is evaluated.

Combined error correction and detection techniques, or hybrid automatic-repeat-request (ARQ) schemes with negative acknowledgment are considered for highly reliable reverse link data transmission in direct sequence code division multiple access (DS-CDMA) personal communication systems. In this paper a coherent link using OQPSK and continuous pilot signal assisted radio channel estimation is analyzed. The proposed selective repeat hybrid ARQ scheme employs an inner convolutional code for error correction and an outer shortened BCH code for error detection. Accepted packet error rate and throughput are derived as a function of the error correction encoded frame error rate. An optimum signal-to-interference ratio (SIR) assignment maximizing the system's capacity is also found. Analysis and simulations show that by applying the proposed type I hybrid ARQ scheme with properly selected system parameters, virtually error free and highly efficient data transmission in CDMA personal communication systems is possible.