Root raised cosine roll-off (RRC) filter is one of the most fundamental elements in modern digital communications. This paper proposes a new method to efficiently realize the RRC filter. The method employs cubic Hermite interpolation to obtain a piecewise-polynomial approximation for the impulse response of the RRC filter. Then, the approximated impulse response is efficiently realized by using a transversal filter with a very small number of taps followed by integrators with a simple recursive structure, named cascaded recursive finite impulse response (CR-FIR) filter. As an example, an RRC filter with roll-off factor 0.5 is constructed by using the CR-FIR filter with only nine multipliers. Performance of the RRC filter in matched filtering is examined by computer simulations. Then, it is shown that the constructed RRC matched filter has nearly the same performance as the ideal filter.

In this paper, we propose a new automatic repeat request (ARQ) scheme, named Go-Back-i-symbol (GBi) ARQ scheme, suitable to Meteor Burst Communications (MBC). The scheme realizes symbol-wise ARQ by using the Viterbi decoding algorithm for convolutional codes. We also propose a practical transmission protocol for applying the GBi-ARQ scheme to packet communications over time varying short burst channels such as meteor burst channels. Fundamental performances of the GBi-ARQ scheme in MBC are evaluated by computer simulations. Effectiveness of the GBi-ARQ scheme is shown by comparing the performance with that of a conventional block-wise ARQ scheme.

In this paper, we propose a new ARQ scheme, named Go-Back-i-symbol (GBi) ARQ scheme which is suitable to Meteor Burst Communications (MBC). The scheme is based on the Viterbi decoding algorithm for convolutional codes and can achieve symbol-wise retransmission, so that it has high throughput performance for packet communication systems over time varying short burst channels such as MBC channels. We also propose a practical transmission protocol for applying the GBi-ARQ scheme to MBC systems. Comparing to a conventional block-wise ARQ scheme, the effectiveness of the proposed scheme is shown by computer simulations.

Studies a queueing scheme of calls in cellular radio systems where priority is given to handoff calls by assigning several channels exclusively for them. The remaining channels are shared by both the originating and handoff calls. In this scheme both the originating and handoff calls make their own queues. A handoff call queues up if on arrival it finds no idle channels. An originating call also queues if on arrival it finds that the number of available channels is less than or equal to that of the reserved channels. Important performance measures of the system such as forced termination probability, and queue lengths are obtained. Solutions for some special systems such as ones with a queue only for the handoff calls and without queues for any calls were also investigated.>

The M/sup (m)//M/K and M/sup (m)//M/ infinity models with synchronous fluctuation of traffic intensity are considered. The phase process is assumed to make changes according to an irreducible m-phase Markov chain. In contrast to the model with asynchronous fluctuation of parameters, a phase change may occur only in synchronization with an arrival or beginning of service of a customer. The authors study the steady-state regime of their models and observe that closed-form solutions for the limiting probabilities are generally difficult to obtain. They give a necessary and sufficient condition for the steady state to be attained. Numerical examples are discussed that demonstrate the behavior of the system under different traffic conditions.>