Showing papers on "Channel allocation schemes published in 1979"
TL;DR: The distribution of the message delay difference under the corresponding TDMA and FDMA schemes, for any message arrival stream, any service ordering discipline and at any time, is derived and is shown to be equal to that of a simple random variable associated with the message arrivals stream.
Abstract: Message delays under a Time Division Multiple Access (TDMA) scheme and the corresponding Frequency Division Multiple Access (FDMA) scheme are studied and compared. Under a TDMA scheme, a network station is assigned a number of slots for each time frame. Under the corresponding FDMA scheme, this station is allocated a separate frequency band for which the ratio between its width and the channel bandwidth is equal to the corresponding time portion allocated by the TDMA scheme. The distribution of the message delay difference under the corresponding TDMA and FDMA schemes, for any message arrival stream, any service ordering discipline and at any time, is derived. This distribution is shown to be equal to that of a simple random variable associated with the message arrival stream. Message delays under a TDMA scheme are shown to be always lower than those under the corresponding FDMA scheme, but the difference value is lower than the time frame duration. Station-buffer queue sizes under both schemes are shown to be essentially the same.
82 citations
27 Mar 1979
TL;DR: In this article, the authors estimate the spectrum efficiency of a Frequency-Hopped-DPSK modulation technique proposed for use in urban mobile radio systems, based on simple models for the factors influencing system performance, and require no computer simulations.
Abstract: We estimate the spectrum efficiency (bits/sec. per unit bandwidth) of a Frequency-Hopped-DPSK modulation technique proposed for use in urban mobile radio systems. The analysis is based on simple models for the factors influencing system performance, and requires no computer simulations. It permits straightforward evaluation of spectrum efficiency over a broad range of system parameters. For an isolated service area (cell) with no propagation impairments, the efficiency is 0.12 at a bit error rate of 10-3. When interference from nearby cells is considered (assuming centrally located base stations with omnidirectional antennas), the efficiency falls to 0.03 - 0.05, depending on how much performance degradation can be tolerated near the cell boundaries. Finally, the effects of multipath (Rayleigh) fading reduce system efficiency to 0.02 - 0.04.
13 citations
TL;DR: The FDMA/DAMA traffic load allowed by spectrum constraints falls off as a function of the manner in which frequency channels and traffic are distributed over the terminals, and a linearized traffic model is presented for making such an analysis.
Abstract: A problem in the use of satellite Demand-Assigned Multiple Access (DAMA) results from spectrum limitations at each ground terminal due to avoiding frequency interference to nearby terrestrial microwave radio relay. Frequency Division Multiple Access (FDMA/DAMA) can operate with a terminal-by-terminal assignment of frequency channels out of the total band available to the satellite. Time Division Multiple Access (TDMA) requires the use of the full band at all the terminals. The effect on satellite bandwidth utilization must be evaluated to determine the advantage, if any, of FDMA channel-by-channel assignment. A linearized traffic model is presented for making such an analysis. The FDMA/DAMA traffic load allowed by spectrum constraints falls off as a function of the manner in which frequency channels and traffic are distributed over the terminals. Additionally, a somewhat more complex geometric model is proposed.
2 citations
27 Mar 1979
TL;DR: The paper discusses the implications of channel splitting and examines the objections which have been raised against reducing channel widths below 25 kHz and shows clearly that spectrum efficiency is improved as bandwidths are reduced.
Abstract: The paper discusses the implications of channel splitting and examines the objections which have been raised against reducing channel widths below 25 kHz. It shows that, although the intermodulation products multiply in number, with suitable planning procedures the increase, if anything, tends to improve the choice of frequencies to be allocated. This is particularly so in the case of two frequency operation. Reuse is examined in relation to various layout configurations and shows clearly that spectrum efficiency is improved as bandwidths are reduced.
2 citations
Journal Article•
1 citations