Abstract—Whereas cellular wireless communication systems are subject to short-and long-term fading. The effect of wireless channel has largely been ignored in most of the teletraffic assessment researches. In this paper, a mathematical teletraffic model is proposed to estimate blocking and forced termination probabilities of cellular wireless networks as a result of teletraffic behavior as well as the outage of the propagation channel. To evaluate the proposed teletraffic model, gamma inter-arrival and general service time distributions have been considered based on wireless channel fading effect. The performance is evaluated and compared with the classical model. The proposed model is dedicated and investigated in different operational conditions. These conditions will consider not only the arrival rate process, but also, the different faded channels models. Keywords—Cellular wireless networks, outage probability, traffic model, gamma inter-arrival distribution. I. INTRODUCTION IRELESS services have become of great importance for its different categories and classes. This causes extensive growth rate of the network’s sizes. Considerable studies have discussed the problem when the call is blocked due to insufficient radio resources (time, frequency or code) [1]–[2]. The performance evaluation of a certain mobile communication network as well as the call behavior characteristics are usually analyzed or simulated based on the assumption that the channel can reliably combat the signal degradation, So that the call level is not affected by the erroneous wireless channel. In wireless communication systems, the received signal is subjected to the adverse effects of the channel in the form of short- and long-term fading, also known as shadowing [3]. Short-term fading arises from the existence of multiple paths between transmitter and receiver, shadowing is the result of the topographical terrains structure elements such as tall buildings, trees and other structures in the transmission path. Dropped calls are increased as a result of bad channel conditions. For instance, the main cause and criteria for handoff is essentially the weak signal power resulting from the severe channel degradation. Hence, it is more reasonable to study the call-level performance and packet-level performance with the effect of wireless channel impairment characteristics in the mobile network [4]. Eman S. El-Din is the communication engineer in network planning department, National Telecommunication Institute, Cairo, Egypt (phone: 202- 24048563; fax: 202-22636802; e-mail :emanserag@gmail.com). Hesham.M.Elbadawy is the head of network planning department, National Telecommunication Institute, Cairo, Egypt (phone: 202-24048563; fax: 202-22636802; e-mail :heshamelbadawy@ieee.org). Salwa.H.Elramly is a professor doctor in electronics and communication department , Faculty of Engineering , University of Ain Shams, Cairo, Egypt, (e-mail: sramlye@netscape.net). In general, if the received signal-to-noise ratio (SNR) is becoming lower than a certain level (SNR threshold) for more than a specific period of time (time threshold) [2], the physical connection is considered as an unreliable link. A fresh call can be blocked or a handoff call can be dropped due to lack of resources or operational conditions. Call arrivals are traditionally assumed to be independent Poisson process with a rate as that of call attempted or originated. In such an environment, the blocking probability can be estimated as a function of the traffic load of the originating calls, number of channels in a cell and the users’ mobility using Erlang-B approximation [3]. Anand et.al. [4] evaluated the network performance distinguishing fresh and handoff calls. Hong et.al. [5], introduced the concept of guard channel for priority processing of the handoff calls. Nasser [6] estimates the drop-call probability considering a multimedia wireless network. An adaptive bandwidth allocation algorithm is exploited to improve system performance and to reduce, in particular, handoff-blocking probability. [7] analyzed the system performance with finite user population. In those papers, exponential inter-arrival and service times had been the basic assumption [8]. This concept is well suited for wireless networks like fixed telephone networks, in the present cellular wireless network, connectivity is provided by a radio link. In addition to the lack of channels, there are other reasons (like prepaid account balance, service plan subscribed, power supply of the mobile devices, the users mobility mechanism, electromagnetic propagation condition and handoff) that influence the drop or rejection of a call attempt [9]. In [10], the relationship between handover failure and call dropping is analyzed. Therefore, all attempted calls do not survive to be considered for channel allocation while passing through different phases like electromagnetic propagation, authentication and authorization and handoff. Hence, the arrival rate of calls that are considered for channel allocation may not be the same as the rate of call origination. The current paper will focus on the evaluation of system performance in case of the lack of channel, propagation conditions and investigate most of call drop reasons such as user mobility. A teletraffic model, with gamma inter-arrival time and general service time distributions, has been derived concerning the outage of wireless system in the form of short- and long-term fading. The system performance, in terms of blocking and forced termination probabilities, has been evaluated under guard channel mechanisms. The rest of the paper is organized as follows: in section II, system model description is provided. Section III, discusses the assessment criteria. Numerical results and analysis is provided in section IV. Finally, the paper is concluded in section V. Eman S. El-Din, Hesham M. El-Badawy, Salwa H. Elramly Assessment of Channel Unavailability Effect on the Wireless Networks Teletraffic Modeling and Analysis W World Academy of Science, Engineering and Technology 69 2012 1061