Comparison of Propagations Models in Mobile Telecommunication Systems

Wireless channels are subject to random fluctuations in received signal powerarising from multipath propagation and shadowing arising from the multiplescattering conditions. Considerable efforts have been devoted to the statisticalmodeling and characterization of these different effects, resulting in a range ofmodels for wireless channels which depend on the particular propagationenvironment and underlying communication scenario. The comparative analysis ofdifferent theoretical and empirical propagation models, such as Okumura, Hata,COST-231 Hata, and Longley-Rice, is given in this paper. After a brief introductionand description of these models, we present some numerical results usingMATLAB and RadioWORKS

User dependent cryptography for security in future mobile telecommunication systems

In this paper we propose a user dependent scheme for enhancing security of the transmitted content in the future telecommunication systems. In order to achieve a higher level of security we introduce a scheme where the user identity gets involved in the encryption/decryption processes using an additional component for the block cipher which represents the user’s behavioural model. Applying such a scheme, in addition to introducing more difficulties to an attacker due to the user dependency of the cipher algorithm, gives the mobile operator the opportunity to ensure that a licensed service has not been shared by the customer. To show the feasibility of our approach we use the concept of invertible Boolean functions as an example

Mean waiting time in the M/H2/s queue: application to mobile communications Systems

In this paper a procedure to approximately calculate the mean waiting time in the M/H2/s queue is presented. The approximation is heuristic although based in the intuitive symmetry between the deterministic and balanced hyperexponential-2 distributions. The three parameters which fully describe the H2 distribution are considered, so the approximation can also be used for the M/G/s queue when the first three moments are known. If only the first two moments of the holding time distribution are known, the estimation can also be applied accepting a lesser accuracy. The estimation proposed is a closed formula extremely easy to compute and the results are very accurate. This features makes it helpful in the design of mobile telecommunication systems with more than one channel and queueing allowed (like trunking Private Mobile Radio PMR systems), where holding time distributions with coefficients of variation higher than one may appear. As a second stage, the possibility of calls owning a certain level of priority is studied. Two service classes are considered according to a non-preemtive priority scheme (also known as Head Of the Line or HOL). This priority feature is often required in mobile telecommunications systems to improve the access delay of some special calls by degrading the delay suffered by the rest. If the proportion of calls owning priority is kept low, the degradation is shared by many calls and then kept small. In this paper a procedure to estimate the mean waiting time in queue for each priority class is presented. This procedure is also very easy to compute. The environment for which the results of this paper are intended suggests medium or heavy overall load and light priority load (priority proportion is kept low). This is the situation under which the accuracy of the proposed method is checked. Although simulations are necessary in the final phase of the design, the procedure presented here is helpful as a first quick insight into the system performance.Peer ReviewedPostprint (published version

Mobile satellite services: International co-ordination, co-operation and competition

In the context of a discussion of international cooperation, coordination and competition regarding mobile satellite services, it is asserted that: there will be more than one civil mobile satellite service in the 1990's; competition between these separate mobile satellite systems is inevitable; no system should enjoy monopoly protection or subsidies; and coordination and cooperation are desirable and necessary, since the available L-band spectrum is in short supply

Electromagnetic Radiation Measurements and Safety Issues of some Cellular

As the mobile telecommunication systems are tremendously growing allover the world then the numbers of handheld andbase stations are also rapidly growing and it became very popular to see these base stations distributed everywhere in theneighborhood and on roof tops which has caused a considerable amount of panic to the public in Palestine concerning witherthe radiated electromagnetic field from these base stations may cause any health effect or hazard. This paper focuses on theradiated electromagnetic energy from some typical mobile base stations around the city of Nablus. The exposure levels dueto these stations were measured and compared to some international standard guidelines like ICNIRP and FCC to see if itmeets these standards, this is in order to answer some of the public fear and concern. The results are presented and somecomments are made on the other sources of electromagnetic radiation in the 200 kHz to 3 GHz range

Two-dimensional packing problems in telecommunications

We present the transcript of the IFORS distinguished lecture delivered by the author on invitation of SOBRAPO and IFORS. The lecture concerned the development of an interdisciplinary research motivated by an application in mobile telecommunication systems, a project jointly developed by four research teams. The presentation follows the typical steps of a classical operations research study, and aims at reviewing the main theoretical and practical results that were obtained