Constraints on capacity allocation are investigated for circuit-switched demand access to a common transmission resource by user communities with differing traffic intensity and capacity requirements. A simple birth-death steady-state traffic model is used together with a geometrical representation of any given set of constraints placed upon user access. State probabilities have a simple product form which holds for a wide class of constraint sets. Performance characteristics are intrinsic to the upper surface of the constraint set.

A Multi-User-Class, Blocked-Calls-Cleared, Demand Access Model

Summary
In this survey paper, we review the random access (RA) techniques with particular emphasis on the issues and the possible solutions applicable to satellite networks. RA dates back to the 1970s when the ALOHA protocol was developed to solve the problem of interconnecting university computers located in different Hawaiian islands. Since then, several evolutions of the ALOHA protocol have been developed. In particular, solutions were devised to mitigate the problem of packet collisions severely degrading the RA protocols performance. The approach followed for many years has been to avoid the occurrence of collisions rather than solving them. More recently, techniques tackling the RA packet collision problem have appeared triggered by the need of improving RA performance in satellite and terrestrial wireless networks. In particular, satellite networks large propagation delay does not allow the adoption of enhanced terrestrial RA techniques based on channel sensing. Adopting conventional demand assignment multiple access protocols is not suitable for supporting a large number of sensors or devices transmitting small-size low duty cycle packets as required for machine-to-machine communications. This provided the stimulus to exploit successive interference cancelation schemes to solve packet collision issues. The use of successive interference cancelation in RA is relatively new and has opened up a promising research area. We provide an extensive review of recent high-performance RA techniques achieving more than three orders of magnitude throughput increase compared with the original ALOHA at low packet loss rate. In this survey, we cover both slotted and unslotted techniques. Finally, we review the use of RA in satellite systems and related standards including recent proposals for machine-to-machine applications. Copyright © 2016 John Wiley & Sons, Ltd.

Random access schemes for satellite networks, from VSAT to M2M: a survey

A multiserver queueing system with two classes of customers is considered: a type-1 (narrowband, NB) customer requires a single server, while each type-2 (wideband, WB) customer requests n of the m servers (n is not random) Severs allocated to a type-2 customer are seized and released simultaneously Service times are exponentially distributed with mean 1//sub mu i/ for type i customers (i=1, 2) Blocked type-1 customers are cleared while blocked type-2 customers may be delayed in an infinite waiting room A type-1 customer enters service immediately upon arrival if at least one server is free, irrespective of the status of the type-2 queue WB customers have restricted access to the service facility; a cutoff parameter specifies the maximum number of type-2 customers that can be in service at the same time Two approaches, moment-generating functions and matrix-geometric techniques, are considered for the computation of the system performance, that is, the mean waiting time in queue and the probability of delay (ie nonzero waiting time) for type-2 customers, as well as the probability of blocking for type-1 customers >

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A multiserver queue with narrow- and wide-band customers and wide-band restricted access

Several allocation strategies are investigated for sharing the satellite capacity among user communities requiring circuit-switched or store-and-forward (message-switched) communication service. Teletraffic and queueing models are used to obtain analytical results by which the allocation strategies are compared. It is shown that the capacity required to provide a specified grade of service is strongly dependent upon the particular allocation strategy chosen. Therefore, an allocation strategy can be selected which requires less capacity and hence provides more efficient utilization of the satellite capacity for a specified grade of service.

Satellite capacity allocation

Communication Networks And Systems

Demand assignment of satellite power on a call-call-by-call basis results in increased system capacity The probability that a call is blocked is not readily available, and standard formulas commonly used for the Poisson and Erlang B traffic model cannot be directly applied Expressions for blocking probabilities are derived here for fully variable, variable-source, and variable-destination demand assignments A numerical example is given for their application in a network of terminals of varying sizes and known point-to-point traffic

The Grade of Service in Multiple-Access Satellite Communications Systems with Demand Assignments

The lane ambiguity problem prevents the utilization of the Omega system for many applications such as locating buoys and balloons. The method of multiple lines of position introduced herein uses signals from four or more Omega stations for ambiguity resolution. The coordinates of the candidate points are determined first through the use of the Newton iterative procedure. Subsequently, a likelihood function is generated for each point, and the ambiguity is resolved by selecting the most likely point. The method was tested through simulation.

G. Frenkel

Papers

The Grade of Service in Multiple-Access Satellite Communications Systems with Demand Assignments

Ambiguity Resolution in Systems Using Omega for Position Location