Reza Saadat | Yazd University (original) (raw)

Papers by Reza Saadat

2011 Third International Conference on Computational Intelligence, Communication Systems and Networks, 2011

Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the qualit... more Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the quality of service and traffic engineering requirements. In the literature, there are many forwarding strategies proposed by researchers to overcome this challenge. One ...

2008 Second International Conference on Electrical Engineering, 2008

ABSTRACT Cross ambiguity function is a common method for joint estimation of TDOA/FDOA. CAF perfo... more ABSTRACT Cross ambiguity function is a common method for joint estimation of TDOA/FDOA. CAF performance degrades in wideband situation. The maximum likelihood estimator in wideband model contains data resampling. Because of intensive computational burden data resampling isnpsilat viewed as a practical method. Calculation of short time CAFs and summation of them is suggested as a practical alternative method. Different summation methods were suggested for compensation of TDOA variation in the integration time. In this paper first with an experimental test we find the areas in which FDOA variations is noticeable and we indicate that these regions are big enough not to be ignored. Then a new method for summation of sequential CAFs is presented. The proposed method compensates variation of both TDOA and FDOA together and via this method, detection ability of peak in combined CAF is improved. The proposed method is based on recti linear constant speed (RLSC) motion.

IEICE Transactions on Communications, 2012

ABSTRACT We focus on the cooperative mobile positioning based on the received signal strength for... more ABSTRACT We focus on the cooperative mobile positioning based on the received signal strength for heterogeneous environments. We use the least squares method to estimate the channel attenuation coefficients, and hyperbolic method to determine the position. For increasing accuracy, we use different weighting to the adjacent users' data in the attenuation coefficients estimation.

Hyperfine Interactions, 2012

The nonanuclear coordination compound [Mo IV {(CN)Fe III (3-methylsaldptn)} 8 ]Cl 4 exhibits mult... more The nonanuclear coordination compound [Mo IV {(CN)Fe III (3-methylsaldptn)} 8 ]Cl 4 exhibits multiple spin transitions (3-methyl-saldptn = N,N -bis(3methyl-2 -hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. Mössbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid.

2015 IEEE Electrical Power and Energy Conference (EPEC), 2015

Advances in Computer Science and Engineering, 2009

In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogon... more In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogonality between physical channels, in order to increasing system capacity. The Orthogonal Variable Spreading Factor (OVSF) codes are used as the channelization codes in this system. In WCDMA, it is possible to provide multi-rate service by employing the OVSF codes, which can be generated in the form of tree structure. This scheme is known as OVSF-CDMA. One important limitation of OVSF-CDMA is that the system must maintain the orthogonality among the assigned codes. The maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity. This research compares the performance of OVSF code assignment schemes, in terms of code blocking probability and number of required code reassignment.

13Th International Conference on Advanced Communication Technology, Feb 1, 2011

In this paper we consider a relaying communication system over Rician fading channels. In this sy... more In this paper we consider a relaying communication system over Rician fading channels. In this system we assume simple Incremental-Selective Decode-and-Forward (ISDF) protocol, which is jointly combining incremental and selective DF relaying protocols. In this protocol, storage or retransmission of the first phase signal are not allowed. We analyze the symbol error rate (SER) performance of the recommended protocol with

2014 22nd Iranian Conference on Electrical Engineering, May 1, 2014

13Th International Conference on Advanced Communication Technology, 2011

ABSTRACT In this paper we consider a cooperative communication systems over Rayleigh fading chann... more ABSTRACT In this paper we consider a cooperative communication systems over Rayleigh fading channels. The system utilizes a combination of incremental and selective decode-and-forward (ISDF) relaying protocols. The symbol error rate (SER) of M-PSK modulation for the ISDF protocol is derived. Using an approximation of the SER expression, the optimal power allocation is investigated. In order to reduce the complexity of the receiver, we used a modified version of the ISDF protocol which does not use the storage or retransmission of the first phase signal. We also derived optimal power allocation coefficient for modified ISDF. It has been noted that for the optimal power allocation in the ISDF protocol, at least 2/3 of total power must be used by the direct link. For the modified ISDF protocol this portion should be reduced to 1/2. Also the optimal power allocation coefficient is not dependent on SNR.

2011 19thtelecommunications Forum Proceedings of Papers, Nov 1, 2011

2011 19th Iranian Conference on Electrical Engineering, May 17, 2011

ABSTRACT Ethernet networks rely on Spanning Tree Protocol (STP) that guarantees a loop-free tree ... more ABSTRACT Ethernet networks rely on Spanning Tree Protocol (STP) that guarantees a loop-free tree topology in the network. STP does this task by pruning the redundant links. This protocol doesn't have any traffic engineering mechanism for load balancing since the tree construction in this protocol is only based on the shortest path criterion. In this paper, we propose an efficient fast algorithm to find the best spanning tree by modeling and solving objective functions based on load balancing criterions. By using this objective we can balance the traffic load on links and switches. Finally through some simulations on a typical network, we show the effectiveness of our approach.

2012 14th International Conference on Advanced Communication Technology, 2012

ABSTRACT Current Ethernet technology relies on Spanning Tree Protocol (STP). As the name suggests... more ABSTRACT Current Ethernet technology relies on Spanning Tree Protocol (STP). As the name suggests, STP creates a spanning tree within a network of connected layer-2 Ethernet switches, and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes. Because of lack of any traffic engineering mechanism in STP, there is not any load balancing on links and switches. This causes a huge load on some links and switches especially close to the root node. In our previous works, we have suggested some forwarding strategies such as: BST and SSS to overcome this problem. In this paper, we propose a new forwarding strategy based on hierarchical addressing named Hierarchical Forwarding Strategy (HFS), to improve the performance of the previous forwarding strategies. Simulation results show the improvements of HFS in comparison to STP and SSS.

Ieice Transactions on Communications, 2009

Mobile positioning using Received Signal Strength (RSS) measurements is regarded as a low cost so... more Mobile positioning using Received Signal Strength (RSS) measurements is regarded as a low cost solution which is applicable in a wide range of wireless networks. In this paper, we propose a cooperative RSS-based positioning algorithm, that relies on the promising idea of mobile to mobile communications in the next generation of cellular networks. Simulations performed in this paper indicate that utilizing the additional RSS data of the short range communications between Mobile Stations (MS's), enhances the accuracy of the traditional RSS-based positioning algorithms.

2011 19th Iranian Conference on Electrical Engineering, May 17, 2011

ABSTRACT Ethernet is becoming a preferred technology to be deployed in metro domain due to its lo... more ABSTRACT Ethernet is becoming a preferred technology to be deployed in metro domain due to its low cost, simplicity and ubiquity. Nevertheless, Ethernet was originally designed as a LAN technology; therefore, it lacks fast fault-protection which is very important in the new real-time applications. On the other hand, most of the failure recovery algorithms proposed in literature are offline in nature or they are very complex to be used in Ethernet networks. In this paper, we propose an Online Fast Failure Recovery Strategy (OFFRS) to find the best redundant paths with minimum cost for each protected link. OFFRS is a simple, fast and online approach useful to be applied in metro Ethernet networks. Simulation results will show the effectiveness of OFFRS.

2010 2nd International Conference on Education Technology and Computer, 2010

ABSTRACT Spanning Tree Protocol (STP) is an IEEE approved standard that provides path redundancy ... more ABSTRACT Spanning Tree Protocol (STP) is an IEEE approved standard that provides path redundancy while preventing undesirable loops in the Ethernet networks. STP uses a single tree for the entire network which may result in inefficient bandwidth allocation since the non-spanning-tree links will not carry traffic at all. As a solution, the IEEE 802.1s working group has introduced a Multiple Spanning Tree Protocol (MSTP) that allows a switch to participate in multiple spanning trees, one tree per group of VLANs. In our previous work, we introduced a graph theoretic approach named Best Multiple Spanning Tree (BMST) algorithm for ranking all of the possible solutions for selection of the proper trees in a network running MSTP and for finding the best solution based on load balancing on links and switches. Although, BMST algorithm can find the best answer for small networks, but its complexity is too large in large scale networks. In this paper, we propose a simple approach named Multiple Best Spanning Tree (MBST) to reduce the computational complexity of the BMST.

2011 Third International Conference on Computational Intelligence, Communication Systems and Networks, 2011

Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the qualit... more Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the quality of service and traffic engineering requirements. In the literature, there are many forwarding strategies proposed by researchers to overcome this challenge. One ...

20th Iranian Conference on Electrical Engineering (ICEE2012), 2012

ABSTRACT One of the most important operations of the Wireless Sensor Networks (WSNs) is data coll... more ABSTRACT One of the most important operations of the Wireless Sensor Networks (WSNs) is data collection. Due to power limitation of sensors, the process of data collection from nodes in the network towards the sink must be simple and energy-aware. In this regard, tree routing is suitable for data collection in WSNs, because each node only needs to know its parent to forward data packets. However, a non load-balancing tree makes some nodes consume energy faster than others. In this paper, a new tree routing protocol is introduced which prolongs the network lifetime via load-balancing. It is named Efficient Convergecast Tree (ECT). ECT is a distributed algorithm that constructs an approximate load-balanced shortest-path spanning tree by using local information. Simulation results show that ECT protocol fairly increases the network lifetime and throughput.

Communications in Computer and Information Science, 2009

ABSTRACT In Wideband Code Division Multiple Access, Channelization codes are used to preserve the... more ABSTRACT In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogonality between physical channels, in order to increasing system capacity. The Orthogonal Variable Spreading Factor (OVSF) codes are used as the channelization codes in this system. In WCDMA, it is possible to provide multi-rate service by employing the OVSF codes, which can be generated in the form of tree structure. This scheme is known as OVSF-CDMA. One important limitation of OVSF-CDMA is that the system must maintain the orthogonality among the assigned codes. The maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity. This research compares the performance of OVSF code assignment schemes, in terms of code blocking probability and number of required code reassignment.

2008 International Conference on Computer and Communication Engineering, 2008

ABSTRACT This research compares the performance of static and dynamic OVSF code assignment scheme... more ABSTRACT This research compares the performance of static and dynamic OVSF code assignment schemes, in terms of call blocking probability and number of required call reassignment. In wideband code division multiple access (CDMA), in order to increasing system capacity, channelization codes are used to preserve the orthogonality between physical channels. The orthogonal variable spreading factor (OVSF) codes are used as the channelization codes in this system. The spectral efficiency of the system depends on the code assignment schemes. In addition, the maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity.

2011 Third International Conference on Computational Intelligence, Communication Systems and Networks, 2011

Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the qualit... more Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the quality of service and traffic engineering requirements. In the literature, there are many forwarding strategies proposed by researchers to overcome this challenge. One ...

2008 Second International Conference on Electrical Engineering, 2008

ABSTRACT Cross ambiguity function is a common method for joint estimation of TDOA/FDOA. CAF perfo... more ABSTRACT Cross ambiguity function is a common method for joint estimation of TDOA/FDOA. CAF performance degrades in wideband situation. The maximum likelihood estimator in wideband model contains data resampling. Because of intensive computational burden data resampling isnpsilat viewed as a practical method. Calculation of short time CAFs and summation of them is suggested as a practical alternative method. Different summation methods were suggested for compensation of TDOA variation in the integration time. In this paper first with an experimental test we find the areas in which FDOA variations is noticeable and we indicate that these regions are big enough not to be ignored. Then a new method for summation of sequential CAFs is presented. The proposed method compensates variation of both TDOA and FDOA together and via this method, detection ability of peak in combined CAF is improved. The proposed method is based on recti linear constant speed (RLSC) motion.

IEICE Transactions on Communications, 2012

ABSTRACT We focus on the cooperative mobile positioning based on the received signal strength for... more ABSTRACT We focus on the cooperative mobile positioning based on the received signal strength for heterogeneous environments. We use the least squares method to estimate the channel attenuation coefficients, and hyperbolic method to determine the position. For increasing accuracy, we use different weighting to the adjacent users' data in the attenuation coefficients estimation.

Hyperfine Interactions, 2012

The nonanuclear coordination compound [Mo IV {(CN)Fe III (3-methylsaldptn)} 8 ]Cl 4 exhibits mult... more The nonanuclear coordination compound [Mo IV {(CN)Fe III (3-methylsaldptn)} 8 ]Cl 4 exhibits multiple spin transitions (3-methyl-saldptn = N,N -bis(3methyl-2 -hydroxy-benzyliden)-1,7-diamino-4-azaheptane). This spin crossover cluster is bound via a self-assembled monolayer onto a two dimensional array gold surface. Mössbauer spectroscopy indicates that the thermally and optically induced spin crossover of the compound is maintained. Thereby, the foundation for its potential practical application (e.g. in the field of information storage) was laid.

2015 IEEE Electrical Power and Energy Conference (EPEC), 2015

Advances in Computer Science and Engineering, 2009

In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogon... more In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogonality between physical channels, in order to increasing system capacity. The Orthogonal Variable Spreading Factor (OVSF) codes are used as the channelization codes in this system. In WCDMA, it is possible to provide multi-rate service by employing the OVSF codes, which can be generated in the form of tree structure. This scheme is known as OVSF-CDMA. One important limitation of OVSF-CDMA is that the system must maintain the orthogonality among the assigned codes. The maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity. This research compares the performance of OVSF code assignment schemes, in terms of code blocking probability and number of required code reassignment.

13Th International Conference on Advanced Communication Technology, Feb 1, 2011

In this paper we consider a relaying communication system over Rician fading channels. In this sy... more In this paper we consider a relaying communication system over Rician fading channels. In this system we assume simple Incremental-Selective Decode-and-Forward (ISDF) protocol, which is jointly combining incremental and selective DF relaying protocols. In this protocol, storage or retransmission of the first phase signal are not allowed. We analyze the symbol error rate (SER) performance of the recommended protocol with

2014 22nd Iranian Conference on Electrical Engineering, May 1, 2014

13Th International Conference on Advanced Communication Technology, 2011

ABSTRACT In this paper we consider a cooperative communication systems over Rayleigh fading chann... more ABSTRACT In this paper we consider a cooperative communication systems over Rayleigh fading channels. The system utilizes a combination of incremental and selective decode-and-forward (ISDF) relaying protocols. The symbol error rate (SER) of M-PSK modulation for the ISDF protocol is derived. Using an approximation of the SER expression, the optimal power allocation is investigated. In order to reduce the complexity of the receiver, we used a modified version of the ISDF protocol which does not use the storage or retransmission of the first phase signal. We also derived optimal power allocation coefficient for modified ISDF. It has been noted that for the optimal power allocation in the ISDF protocol, at least 2/3 of total power must be used by the direct link. For the modified ISDF protocol this portion should be reduced to 1/2. Also the optimal power allocation coefficient is not dependent on SNR.

2011 19thtelecommunications Forum Proceedings of Papers, Nov 1, 2011

2011 19th Iranian Conference on Electrical Engineering, May 17, 2011

ABSTRACT Ethernet networks rely on Spanning Tree Protocol (STP) that guarantees a loop-free tree ... more ABSTRACT Ethernet networks rely on Spanning Tree Protocol (STP) that guarantees a loop-free tree topology in the network. STP does this task by pruning the redundant links. This protocol doesn't have any traffic engineering mechanism for load balancing since the tree construction in this protocol is only based on the shortest path criterion. In this paper, we propose an efficient fast algorithm to find the best spanning tree by modeling and solving objective functions based on load balancing criterions. By using this objective we can balance the traffic load on links and switches. Finally through some simulations on a typical network, we show the effectiveness of our approach.

2012 14th International Conference on Advanced Communication Technology, 2012

ABSTRACT Current Ethernet technology relies on Spanning Tree Protocol (STP). As the name suggests... more ABSTRACT Current Ethernet technology relies on Spanning Tree Protocol (STP). As the name suggests, STP creates a spanning tree within a network of connected layer-2 Ethernet switches, and disables those links that are not part of the spanning tree, leaving a single active path between any two network nodes. Because of lack of any traffic engineering mechanism in STP, there is not any load balancing on links and switches. This causes a huge load on some links and switches especially close to the root node. In our previous works, we have suggested some forwarding strategies such as: BST and SSS to overcome this problem. In this paper, we propose a new forwarding strategy based on hierarchical addressing named Hierarchical Forwarding Strategy (HFS), to improve the performance of the previous forwarding strategies. Simulation results show the improvements of HFS in comparison to STP and SSS.

Ieice Transactions on Communications, 2009

Mobile positioning using Received Signal Strength (RSS) measurements is regarded as a low cost so... more Mobile positioning using Received Signal Strength (RSS) measurements is regarded as a low cost solution which is applicable in a wide range of wireless networks. In this paper, we propose a cooperative RSS-based positioning algorithm, that relies on the promising idea of mobile to mobile communications in the next generation of cellular networks. Simulations performed in this paper indicate that utilizing the additional RSS data of the short range communications between Mobile Stations (MS's), enhances the accuracy of the traditional RSS-based positioning algorithms.

2011 19th Iranian Conference on Electrical Engineering, May 17, 2011

ABSTRACT Ethernet is becoming a preferred technology to be deployed in metro domain due to its lo... more ABSTRACT Ethernet is becoming a preferred technology to be deployed in metro domain due to its low cost, simplicity and ubiquity. Nevertheless, Ethernet was originally designed as a LAN technology; therefore, it lacks fast fault-protection which is very important in the new real-time applications. On the other hand, most of the failure recovery algorithms proposed in literature are offline in nature or they are very complex to be used in Ethernet networks. In this paper, we propose an Online Fast Failure Recovery Strategy (OFFRS) to find the best redundant paths with minimum cost for each protected link. OFFRS is a simple, fast and online approach useful to be applied in metro Ethernet networks. Simulation results will show the effectiveness of OFFRS.

2010 2nd International Conference on Education Technology and Computer, 2010

ABSTRACT Spanning Tree Protocol (STP) is an IEEE approved standard that provides path redundancy ... more ABSTRACT Spanning Tree Protocol (STP) is an IEEE approved standard that provides path redundancy while preventing undesirable loops in the Ethernet networks. STP uses a single tree for the entire network which may result in inefficient bandwidth allocation since the non-spanning-tree links will not carry traffic at all. As a solution, the IEEE 802.1s working group has introduced a Multiple Spanning Tree Protocol (MSTP) that allows a switch to participate in multiple spanning trees, one tree per group of VLANs. In our previous work, we introduced a graph theoretic approach named Best Multiple Spanning Tree (BMST) algorithm for ranking all of the possible solutions for selection of the proper trees in a network running MSTP and for finding the best solution based on load balancing on links and switches. Although, BMST algorithm can find the best answer for small networks, but its complexity is too large in large scale networks. In this paper, we propose a simple approach named Multiple Best Spanning Tree (MBST) to reduce the computational complexity of the BMST.

2011 Third International Conference on Computational Intelligence, Communication Systems and Networks, 2011

Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the qualit... more Abstract Major Challenge for deploying Ethernet in metro area networks is to guarantee the quality of service and traffic engineering requirements. In the literature, there are many forwarding strategies proposed by researchers to overcome this challenge. One ...

20th Iranian Conference on Electrical Engineering (ICEE2012), 2012

ABSTRACT One of the most important operations of the Wireless Sensor Networks (WSNs) is data coll... more ABSTRACT One of the most important operations of the Wireless Sensor Networks (WSNs) is data collection. Due to power limitation of sensors, the process of data collection from nodes in the network towards the sink must be simple and energy-aware. In this regard, tree routing is suitable for data collection in WSNs, because each node only needs to know its parent to forward data packets. However, a non load-balancing tree makes some nodes consume energy faster than others. In this paper, a new tree routing protocol is introduced which prolongs the network lifetime via load-balancing. It is named Efficient Convergecast Tree (ECT). ECT is a distributed algorithm that constructs an approximate load-balanced shortest-path spanning tree by using local information. Simulation results show that ECT protocol fairly increases the network lifetime and throughput.

Communications in Computer and Information Science, 2009

ABSTRACT In Wideband Code Division Multiple Access, Channelization codes are used to preserve the... more ABSTRACT In Wideband Code Division Multiple Access, Channelization codes are used to preserve the orthogonality between physical channels, in order to increasing system capacity. The Orthogonal Variable Spreading Factor (OVSF) codes are used as the channelization codes in this system. In WCDMA, it is possible to provide multi-rate service by employing the OVSF codes, which can be generated in the form of tree structure. This scheme is known as OVSF-CDMA. One important limitation of OVSF-CDMA is that the system must maintain the orthogonality among the assigned codes. The maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity. This research compares the performance of OVSF code assignment schemes, in terms of code blocking probability and number of required code reassignment.

2008 International Conference on Computer and Communication Engineering, 2008

ABSTRACT This research compares the performance of static and dynamic OVSF code assignment scheme... more ABSTRACT This research compares the performance of static and dynamic OVSF code assignment schemes, in terms of call blocking probability and number of required call reassignment. In wideband code division multiple access (CDMA), in order to increasing system capacity, channelization codes are used to preserve the orthogonality between physical channels. The orthogonal variable spreading factor (OVSF) codes are used as the channelization codes in this system. The spectral efficiency of the system depends on the code assignment schemes. In addition, the maintenance of the orthogonality among the assigned OVSF codes causes the code blocking problem. Efficient channelization code management, result in high efficiency of code utilization and increasing system capacity.