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A Minimum-Spanning-Tree-Inspired Algorithm for Channel Assignment in 802.11 Networks

Dolińska I., Jakubowski M., Masiukiewicz A., Rządkowski G., Piórczyński K.

International Journal of Electronics and Telecommunications

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2016

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Vol. 62, No. 4

379--388

EN

Channel assignment in 2.4 GHz band of 802.11 standard is still important issue as a lot of 2.4 GHz devices are in use. This band offers only three non-overlapping channels, so in crowded environment users can suffer from high interference level. In this paper, a greedy algorithm inspired by the Prim’s algorithm for finding minimum spanning trees (MSTs) in undirected graphs is considered for channel assignment in this type of networks. The proposed solution tested for example network distributions achieves results close to the exhaustive approach and is, in many cases, several orders of magnitude faster.

2

Determination of continuous shifts in the term structure of interest rates against which a bond portfolio is immunized

Zaremba L. S., Rządkowski G.

Control and Cybernetics

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2016

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Vol. 45, no. 4

525--537

EN

In this paper we identify those shifts (continuous functions) of the term structure of interest rates, against which a given bond portfolio (BP) is immunized. The set of such shifts (IMMU) happens to be an (m − 1)-dimensional linear subspace in an m-dimensional linear space of all admissible shifts. In the proof we use triangular (Lagrange) functions, by means of which we build a base for IMMU. How this IMMU space varies in response to changes in the cash ﬂow generated by bond portfolio, BP, is also discussed in the last section of the paper.

3

Collision in DCF scheme used in 802.11 standard networks

Dolińska I., Masiukiewicz A., Rządkowski G.

Przegląd Telekomunikacyjny + Wiadomości Telekomunikacyjne

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2014

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nr 2-3

44--46

EN

Due to the structure and functionality of Media Access layer of the 802.11 standard and the necessity of fighting for access by the stations the collisions are something unavoidable. The high number of collisions could impact the system throughput. The authors used two methods for potential collision ratio calculation First the mathematical model than the simulation sheet with Monte Carlo statistical method. The results of both methods were compared.

PL

Ze względu na strukturę i funkcjonalność warstwy MAC standardu 802.11 oraz konieczność walki o uzyskanie dostępu do nośnika przez stacje, kolizje są zjawiskiem nieuniknionym. Duża liczba kolizji może wpływać na przepływność systemu Autorzy wykorzystali dwie metody do wyliczenia potencjalnej liczby kolizji. Pierwsza metoda opierała się na modelu matematycznym, w drugiej wykorzystano symulacje z zastosowaniem arkusza obliczeniowego i statystycznej metody Monte Carlo. Porównano wyniki uzyskane za pomocą obu metod.

4

Collision impact on transmission QoS in 802.11n networks

Dolińska I., Masiukiewicz A., Rządkowski G.

Elektronika : konstrukcje, technologie, zastosowania

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2013

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Vol. 54, nr 12

74-75

EN

The collisions in 802.11 networks are unavoidable. The issue is how many collision we have in analyzed time period. The increased collision number can reduce the final throughput however the results depends strongly on current CW and TBO values. This means unfairness from the point of view of different stations and dynamic behavior of QoS which could significantly differ for each transmission session.

PL

Nie można uniknąć kolizji w sieciach standardu 802.11. Kwestią analiz i optymalizacji może być jedynie ilość kolizji w jednostce czasu. Wzrost ilości kolizji może zredukować osiąganą przepustowość kanału jakkolwiek końcowa wartość przepustowości silnie zależy od bieżących wartości CW i TBO. Oznacza to w praktyce nierówność warunków dostępu z punktu widzenia różnych stacji, a w konsekwencji duża dynamikę QoS, które może się znacząco zmieniać dla każdej sesji transmisyjnej.

5

Extension of Khang's Immunization Formula

Zaremba L.S., Rządkowski G.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2001

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vol. 49, nr 3

527-536

EN

The paper presents two theorems on immunization in the continuous context when a liability consists of a single outflow at a known future date. It is assumed in Theorem 1 that interest rates h(O, t) shift to their new values h * (O, t) = h(O, t) + f()..)a(t) where ).. is a random parameter "chosen" by a financial market under consideration, while a(t) is a continuous function and f()..) is twice continuously differentiable with f(O) = O, f' (O) #- O. It is proved that the local immunization is achieved and a formula for the immunizing duration is derived. Theorem 2 provides a formula for the immunizing duration of the portfolio combined with two cash flows. These two theorems extend validity of all similar type results presented by Bierwag (1983).