Abstract The paper presents a method developed for control of walking robots. We used, in this work, a hierarchical fuzzy controller. We applied this method on the control of seven degrees of freedom planar biped into free area and without obstacles. First, we use a classical PID controller. Then, we used hierarchical fuzzy logic controller (HFLC) to command our system (the... The paper presents a method developed for control of walking robots. We used, in this work, a hierarchical fuzzy controller. We applied this method on the control of seven degrees of freedom planar biped into free area and without obstacles. First, we use a classical PID controller. Then, we used hierarchical fuzzy logic controller (HFLC) to command our system (the biped robot). The HFLC is introduced to monitor the control system by the conventional PID for position tracking of various joint biped robots driven by electric motors. Read More Read Less

Abstract The expansion of the wireless networks is one of the main reasons of the doubtless growth of the VoIP communications during the last years. This technology has been extensively studied by the research community from several points of views, such as, (i) the effect of delay, packet loss rate, jitter, etc. on the quality of the VoIP calls, or (ii)... The expansion of the wireless networks is one of the main reasons of the doubtless growth of the VoIP communications during the last years. This technology has been extensively studied by the research community from several points of views, such as, (i) the effect of delay, packet loss rate, jitter, etc. on the quality of the VoIP calls, or (ii) the systems capacities evaluating different bandwidths and coding schemes. However, very few works detailing the effect of the wireless physical layer can be found in the related literature. In this work we employ the Nakagami-m propagation model in order to evaluate the effect of fading channels on VoIP traffic for IEEE 802.11 systems and its influence on the Quality of user Experience (QoE). The results obtained employing this propagation model, which permit us to characterize the wireless channel with different levels of hostility (fading), are compared with those attained in a Free Space environment. We simulate several scenarios, with different codecs, different packetization time-intervals, and different bandwidths in order to study the impact of fading over system capacity, coverage range, and QoE, which is estimated by the E-Model. From our results, we observe that fading channels provoke a noticeable decrease in the system maximum capacity and coverage range. Furthermore, VoIP communications suffer a noticeable drop on the achieved QoE in scenarios affected by fading channels, mainly affecting to low bit-rate codecs. Read More Read Less

Abstract In this paper, we propose an enhancement to the secure routing protocol SecOPP. SecOPP provides the most security services such as integrity, authentication, confidentiality and freshness of data. All these services are obtained with low energy consummation. In addition, this protocol is characterized by little stockade places and reduced computational cost. Despite its robustness against attacks and its scalability, SecOPP... In this paper, we propose an enhancement to the secure routing protocol SecOPP. SecOPP provides the most security services such as integrity, authentication, confidentiality and freshness of data. All these services are obtained with low energy consummation. In addition, this protocol is characterized by little stockade places and reduced computational cost. Despite its robustness against attacks and its scalability, SecOPP in its current application is static. It does not allow secure addition of new nodes. Each node has a limited life time, when batteries became empty, node dies. We propose to securely add new nodes on network to increase its longevity, making it more reliable and robust. This is well verified through simulations with TOSSIM using NesC language. Read More Read Less

Abstract Long Term Evolution (LTE) is designed as a wireless broadband technology for a last generation of Universal Mobile for Telecommunication System (UMTS) to provide multimedia services for the users. In order to study the effect of Hybrid Adaptive Repeat and Request (HARQ) procedure with multiple antenna technique on the performance of LTE system, this paper deals with HARQ procedure in... Long Term Evolution (LTE) is designed as a wireless broadband technology for a last generation of Universal Mobile for Telecommunication System (UMTS) to provide multimedia services for the users. In order to study the effect of Hybrid Adaptive Repeat and Request (HARQ) procedure with multiple antenna technique on the performance of LTE system, this paper deals with HARQ procedure in case of one and two retransmitting. On the other hand, this paper submits Multiple Input Single Output (MISO) technique using two antenna elements at the transmitter side to improve the capability of the system with low complexity for the system. The results showed that the block error rate (BLER) and the throughput of the system are improved when the HARQ procedure and MISO technique are employed together in a three cases study of the Channel Quality Indicator (CQI) of the user. The results explained that the amount of improvement which offered by the procedure of HARQ with two retransmitting be very slight compared with the case of one retransmitting. Read More Read Less