Background and Objectives: with the developments of technology, contact with various frequencies of electromagnetic fields (EMF) has significantly increased, while the abundant benefits of using microwaves in routine life cannot be neglected. During recent years there have been reports of adverse effects caused by contact with electric and magnetic fields of these waves that spread from BTS antennas. The purpose of this study is the measurement of microwaves spreading around BTS antennas in Tehran.Materials and Methods:  according to the location of BTS antennas in Tehran, power density of electromagnetic waves around 63 antennas in near and distant fields in different distances was measured. The measurements were performed using the standard method of IEEE Std C95.1 by Hi-4333 device .in order to analysis data we used spss 16 and descriptive and deductive statistical tests.Results: results of this study show that in the near field, with increase of distance from the foot of antenna, the average power density of electromagnetic waves increase in a way that in the distance of 10 meters from the antenna foot, the increase of average power density is hardly conceivable and from 10 to 15 meters distance is perfectly noticeable. But in the distant field, with increase of distance from 20 meters, the average power density of the electromagnetic waves decreases; and from 100 meter and further, the gradient of the diagram will get almost linear and the rate of power density reaches the base limit in a way that with the increase of distance there would be no significant decrease.Conclusion: All the measures of power density of electromagnetic waves caused by BTSs are about 0.06% of recommended measures of environmental standards and 0.0000013% of occupational standards. The results of this study are close to the results of other studies.

A Reflectarray Antenna is designed to operate at X-band as a Local Multipoint Distribution Service (LMDS) base station antenna. It is a center-fed single layer reflectarray consisting of 23×27 elements. The unit cell of the reflectarray has linear polarization with more than 400° linear phase shift and its geometrical parameters have been optimized to achieve wide bandwidth and low cross polarization (XP) level for the reflectarray. An iterative design procedure, that is valid for obtaining any arbitrary pattern, has been implemented to achieve the specified radiation pattern over a desired frequency range. The method has been successfully applied to a LMDS base station antenna, characterized by a sectorial cosecant squared beam in the frequency range of 9.3 GHz - 11.5 GHz. The simulation results are in a good agreement with the design requirements. The antenna has cosecant squared pattern over the bandwidth of 21%, XP level better than -30 dB, and SLL less than -20 dB in both elevation and azimuth planes. The total size of the 23×27-element array is 246×289 mm2 , and its 1dB gain bandwidth is wider than 19%. The proposed antenna performs significantly better than similar structures and has all the features and standards required for LMDS base station antenna

Resource allocation has always been one of the main challenges in the design of wireless cellular networks. Suitable resource allocation, more specifically that includes suitable base station selection and bandwidth allocation can play an effective role in interference mitigation and users’ quality of service requirement satisfaction. In this paper, a game theoretic approach is proposed to solve the BS selection problem in two-tier wireless femtocell networks. We formulate the competitive behavior of users as evolutionary game theory. We calculate the probability of a user choosing a BS, compute the cell load of each BS, and analyze the demand rejection probability of the user associated with the BS. The proposed approach maximizes network throughput as well as meeting the QoS requirements of the users. Finally, we propose a decentralized learning algorithm based on EXP3 algorithm to achieve the evolutionary equilibrium as the solution of the game. Simulation results show that the proposed approach achieves a desirable performance and guarantees users’ QoS requirements.

Using full duplex communication systems called FD, is a new technique for increasing the spectral efficiency. That`s why it has been considered seriously in the new generation of communication systems. The main challenge of the full-duplex system is the self-interference, which has to be decreased properly. In this paper, we consider a full-duplex cellular network base station and using the antenna selection technique to reduce its self-interference issue. For appropriate antenna selection, we present a new criterion. In this new criterion, antenna selection has been modeled and solved as a multi-objective optimization problem. In this new criterion, antennas which simultaneously minimizes interference channel gain and maximizes uplink (UL) and downlink (DL) channel gains are selected for transmission and reception. Since the goal of the base station is a good performance in both the UL and DL channels and reduction of the self-interference simultaneously, the multi-objective criterion has a better performance when compared to single-objective criteria. In the common single-objective criteria, only the UL and DL channels or interference channel is considered. Finally, simulation results show that the new criterion has more throughput rate than the other single-objective antenna selection technique in the full duplex systems.

The demand for mobile communication systems with high data rate has drawn attention to the millimeter-wave frequencies to increases the channel capacity compared to current 4G cellular networks. So, the fifth generation (5G) mobile communications is presented which is to work in mm-wave frequency band to improve data rate, capacity and latency. One of the challenges of 5G application is the base station and mobile antennas which should be robust against fading. Therefore, in this paper, a two port substrate integrated waveguide (SIW) slot base station antenna for 5G application at 28 GHz is presented. The realized gain of the two-port antenna with a high isolation (20 dB) and circular polarization is 6. 35 dBi. The 5-element array of the two-port antenna with the same excitation can increase the gain 8 dB, but it has some nulls. With phase shift for excitation ports, the nulls are cancelled.

Introduction: Over the last decade, exposure to electromagnetic waves due to base station antenna has increased. This in vivo study was planned for evaluating the effects of 950 MHz waves of GSM mobile phone system on dentate gyrus long-term potentiation.Materials and Methods: 32 naive male Wistar rats (3 months old, 220 + 15 g) were randomly divided into four groups (sham--exposed, continuous 950 MHz, 950 MHz with modulation and 950 MHz GSM field exposed).The exposure program was planned for 10 sessions at 3 days. Animals were exposed to electromagnetic field for 4500n in a circular plastic chamber (mean electric field = 50.4 V/m).Immediately after ending exposure, anesthesia was induced for LTP induction. Field potentials were recorded and analyzed using the population spike amplitude, EPSP slope, EPSP slope maintenance and EPSP duration for 60-min.Results: There were no significant differences in population spike amplitude, EPSP slope and EPSP slope maintenance and EPSP duration among the four groups.Conclusion: This experiment provides no evidence indicating that rat's long-term potentiation can be affected by the whole-body exposure to 950 MHz field of GSM mobile phone system.

The limited energy supply of wireless sensor networks poses a great challenge for the deployment of wireless sensor nodes. In this paper, a sensor network of nodes with wireless transceiver capabilities and limited energy is considered. Clustering is one of the most efficient techniques to save more energy in these networks. Therefore, the proper selection of the cluster heads plays important role to save the energy of sensor nodes for data transmission in the network. In this paper, we propose an energy efficient data transmission by determining the proper cluster heads in wireless sensor networks. We also obtain the optimal location of the base station according to the cluster heads to prolong the network lifetime. An efficient method is considered based on particle swarm algorithm (PSO) which is a nature inspired swarm intelligence based algorithm, modelled after observing the choreography of a flock of birds, to solve a sensor network optimization problem. In the proposed energy-efficient algorithm, cluster heads distance from the base station and their residual energy of the sensors nodes are important parameters for cluster head selection and base station localization. The simulation results show that our proposed algorithm improves the network lifetime and also more alive sensors are remained in the wireless network compared to the baseline algorithms in different situations.