A Comparison of Information Policies for Minimum Delay Routing Algorithms

The problem of routing in a computer networks is dealt with by separating the information problem and the control problem. Several classes of information policies are examined, and numerical comparisons are made of their performance, using representative values of network parameters. Routing based on the expected values of delay, rather than actual values of delay, is shown to be superior to the other algorithms considered.     

Multi-tasking control system for real-time processing of biomedical signals

A general multi-tasking control system has been developed for real-time signal processing. This control system, written in the language PASCAL, enables tasks (expressed as PASCAL procedures) to be performed as separate, concurrent processes, with adjustable priority levels. Modifications of this system such as the addition of new processes and a change of the number of priority levels can be realised easily. The system has been used for the implementation of the real-time algorithms involved in monitoring exercise electrocardiograms. For this application an LSI 11/23 is used with the support of a slave processor for the calculation of inner products. The control system is also suitable for other real-time applications when process requirements are not too heavy.     

Symmetric team problems and multi access wire communication

In this paper we deal with the problem of sharing one communication wire among a (possibly large) number of communication stations. The fact that all communication stations are considered identical and that they share one objective of using the communication wire as efficiently as possible leads to the concept of symmetric team problems. For symmetric team problems we define a symmetric solution by the restriction that all decision makers must have identical decision rules. In the first section of this paper the concepts of symmetric team problems and symmetric solutions are developed and motivated. A theorem is given that relates symmetric solutions to randomized decision rules. An example is given which illustrates that the concept of symmetric solutions explains some everyday phenomena. In the second section the access problem in multi-access wire communication is considered as a symmetric team problem. It is shown that the symmetric solution, which corresponds to randomized access rules, tends to give as good performance as the unrestricted solution when the number of stations becomes large (asymptotic optimality). The solutions are also determined numerically, giving quantitative information on the asymptotic behavior.     

Dynamic Frame Length ALOHA

Adding frame structure to slotted ALOHA makes it very convenient to control the ALOHA channel and eliminate instability. The frame length is adjusted dynamically according to the number of garbled, successful, and empty timeslots in the past. Each terminal that has a packet to transmit selects at random one of thentimeslots of a frame. Dynamic frame length ALOHA achieves a throughput (expected number of successful packets per timeslot) of 0.426 which compares favorably with the1/e (approx0.368)upper bound of ordinary slotted ALOHA.     

Optimal queueing policies for fast packet switching of mixedtraffic

The power of ATM (asynchronous transfer mode) is its ability to provide bandwidth on demand, different sources can have different bandwidth requirements. Sources also differ in performance requirements, some ask for minimal delay variations, whereas others must have extremely low cell loss probabilities. It is shown how these complementary performance requirements can be explained with an LDOLL (low delay or low loss) queue, where sources get either service priority or storage priority. The space of possible LDOLL queuing policies is very large, even after a justified reduction, the size is still O (2^Q2), Q being the maximum number of ATM cells in the LDOLL queue. Using Markov decision theory and concepts of linear programming, only Q so-called efficient solutions are achieved. These are the LDOLL threshold policies, which are conceptually appealing, robust in performance, and practical from the implementation viewpoint