This paper concerns the design, implementation and subsequent experimental validation of a low-voltage analog CMOS switch based on a gate-bootstrapped method. The main part of the proposed circuit is a new low-voltage and low-stress CMOS clock voltage doubler. Through the use of a dummy switch, the charge injection induced by the bootstrapped switch is greatly reduced resulting in improved sample-and-hold accuracy. An important attribute of the design is that the ON-resistance is nearly constant. A test chip has been designed and fabricated using a TSMC 0.18 µm CMOS process (single poly, n-well) to confirm the operation of the circuit for a supply voltage of down to 0.65 V.

An ad hoc network is formed by a group of mobile hosts communicating over wireless channels. There is no any fixed network interaction and centralized administration. Because a routing protocol needs an efficient medium access control (MAC) protocol to support, to design an efficient MAC protocol is important and fundamental in ad hoc networks. So far, no other MAC protocol has stable broadcast performance in the dense mobile ad hoc network. In this paper, we address the issue of reliable broadcast and stable performance at the MAC layer. We present a reliable and adaptive broadcast MAC protocol RAMAC which is a TDMA-based distributed MAC protocol for the broadcast reservation in mobile ad hoc networks. We divide the area into many grid cells with the support of GPS. We use the properties of grid cells to design an efficient protocol. RAMAC is characterized by five important features: (i) A dynamic frame size is generated in every contention. This dynamic frame size can let RAMAC adapt to the network load. (ii) Our well-designed reservation protocol can avoid the deadlock problem. (iii) When the network is dense, RAMAC can still work stably; however, no other MAC protocols can work well in the dense network. (iv) We propose a reservation protocol that can efficiently and fast reserve data slots. (v) The well-designed grid architecture makes the senders of unicast in a grid cell transmit concurrently as many as possible, so RAMAC is highly parallel in unicast.

Since mobile ad-hoc networks have certain constraints, including power shortages, an unstable wireless environment, and node mobility, more power-efficient and reliable routing protocols are needed. Accordingly, this paper propose a new routing protocol, PERRA (Power Efficient Reliable Routing protocol for mobile Ad-hoc networks), that includes the advantages of on-demand protocols, while also providing power- efficient and reliable packet transmission. PERRA uses a new cost function to select the optimum path based on considering the minimum residual energy of the nodes on a path, the total energy consumed by a path to transmit and process a packet, and the path's stability in accordance with the node mobility. As a result, the proposed method increases the power efficiency, decreases the route-reconstructions due to residual power shortages and node mobility, and provides effective route maintenance mechanisms. The performance of PERRA is evaluated by simulations under various conditions.

The reliability-based heuristic search methods for maximum likelihood decoding (MLD) generate test error patterns (or, equivalently, candidate codewords) according to their heuristic values. Test error patterns are stored in lists and its space complexity is crucially large for MLD of long block codes. Based on the decoding algorithms both of Battail and Fang and of its generalized version suggested by Valembois and Fossorier, we propose a new method for reducing the space complexity of the heuristic search methods for MLD including the well-known decoding algorithm of Han et al. If the heuristic function satisfies a certain condition, the proposed method guarantees to reduce the space complexity of both the Battail-Fang and Han et al. decoding algorithms. Simulation results show the high efficiency of the proposed method.

A wireless sensor network is comprised of a large number of battery-limited sensor nodes communicating with unreliable radio links. The nodes are deployed in an ad hoc fashion and a reverse multicast tree is formed in the target domain. The sink node disseminates a query and collects responses from the sensors over pre-established links. Survivability in wireless sensor networks reflects the ability of the network to continue to detect events in the case of individual node failures. We present a sender initiated path switching algorithm that enables the immediate sender to change the packet's route dynamically when its parent on the reverse path is down. The overall effect of path switching on the survivability is analyzed as a measure of reliable event delivery. Using independent battery capacities, an analytical model of a multihop network is derived. The model is used to predict the maximum network lifetime in terms of total transmitted messages; which is in turn used to verify the correctness of our simulations. The results have revealed that dynamic path switching has a better performance than static multipath routing and salvaging schemes. It has also been shown that the proposed approach enhances reliability up to 30% in some topologies.

Due to the pruning and joining of members, multicast groups are dynamic. Both the topology and the total number of links change during multicast sessions, and the multicast performance, measured in terms of the bandwidth consumption, will change accordingly. In this paper, we investigate the dynamic performance of multicast communication with homogeneous packet loss probability; indeed, we evaluate the effects of the pruning of receivers and of subnets, after which we find the optimal placements of repair servers. A new 3-phase algorithm for adapting the optimal repair server placements to the dynamic changes of network topologies is presented and analyzed.

In this paper, we propose the design of a scalable reliable mobile multicast scheme--SRMoM. SRMoM uses well-known Scalable Reliable Multicast (SRM) in the wired networks and a NAK-based ARQ with adaptive Forward Error Correction (AFEC) in the wireless networks. In AFEC, the probability of needing retransmission of original multicast packets after FEC recovery is selectable. This selective property enables the control of channel utilization in the wireless segment for different numbers of Mobile Hosts (MHs). Using this property, the channel utilization of SRMoM is made to be virtually independent of the number of MHs, thus making it extremely scalable. The performance of SRMoM is analyzed with three adaptive FEC algorithms based on three wireless loss models, namely a Gilbert-Elliott channel, a simplified Gilbert-Elliott channel, and a binary symmetric channel, analytically as well as through simulation. Furthermore, the performance of SRMoM is compared with SRM and MRMoM (NAK-based protocol without FEC) through simulation. Using the average number of transmissions per original multicast packet, and wireless link utilization as metrics, we demonstrate that the performance of SRMoM is indeed virtually independent of the number of MHs, and that it results in the lowest number of packet transmissions and lowest channel utilization of reliable mobile multicast protocols that have been proposed to date.

For the efficient multicast distribution services on the Internet, suppressing the influence of packet loss is important issues. As a solution of this problem, Forward Error Correction (FEC) based on Reed-Solomon codes is usually used. However, in the case of content delivery services for a large amount of data, this approach is not suitable. In this paper, we focus on the erasure codes which are new approach of FEC and propose the efficient multicast video distribution method which combines the multicast distribution using erasure codes and direct request to the server. We implement proposal method and confirm its efficiency from the viewpoints of redundancy and processing time.

Existing reliable multicast protocols are designed to perform well in wired networking environments. However, in mobile networking environments, these reliable mobile multicast protocols are not optimal as they do not take into account the limitations of power (energy), storage capacity, processing power, impairments of wireless communication channels, and the frequent changes of location and the resulting loss of network connectivity. This paper analyses four hybrid reliable multicast schemes, namely NAK-based schemes, ACK-based schemes, ACK-based schemes with FEC (Forward Error Correction), and NAK-based schemes with FEC that are suitable for mobile networking environments and quantifies their performance. These four schemes differ from the generic sender-initiated and receiver-initiated reliable multicast protocols in that they rely on a mixture of multicasting and unicasting for providing reliability. This analysis is used to show that NAK-based schemes with FEC is best suited for reliable multicasting in mobile environments as they provide excellent performance in terms of average wireless channel utilization and average processing time, independently of the number of MHs.

This study investigates nonlinear reliable output tracking control issues. Both passive and active reliable control laws are proposed using Variable Structure Control technique. These reliable laws need not the solution of Hamilton-Jacobi (HJ) equation or inequality, which are essential for optimal approaches such as LQR and H reliable designs. As a matter of fact, this approach is able to relax the computational burden for solving the HJ equation. The proposed reliable designs are also applied to a bank-to-turn missile system to illustrate their benefits.

Integration of the MPLS network and the optical mesh network is a promising approach to realize an efficient backbone network. Because large volumes of traffic incur damage from failure, survivability is important in the backbone network. In the MPLS over optical networks, a pair of primary LSP (Label Switched Path) and secondary LSP needs to be established on two optical link-disjoint routes assuming all single optical link failures. However, two link-disjoint routes in the MPLS layer may not correspond to two link-disjoint routes in the optical layer. Thus, a pair of primary and secondary LSPs should be routed considering link-disjointness in the optical layer. In the MPLS over optical networks, secondary LSPs can mutually share lightpath bandwidth if those secondary LSPs correspond to the primary LSPs that never fail simultaneously. Thus, routing of secondary LSPs should promote sharing of the lightpath bandwidth among the secondary LSPs. The primary and secondary LSPs with variable bandwidths should efficiently be packed into fewer lightpaths with a fixed bandwidth. Moreover, if all the LSPs accommodated in a lightpath can be re-routed to other lightpaths, this lightpath can then be released. By re-routing only secondary LSPs, unnecessary lightpaths may be released without disturbance of the conveyed traffic. This paper proposes an efficient routing scheme to establish primary and secondary LSPs with variable bandwidths through the MPLS over optical network. This routing scheme satisfies the above conditions. The bandwidth of each lightpath is efficiently utilized by this routing scheme, and the loss rate of LSP requests can be reduced. This paper also proposes an efficient re-routing scheme to remove secondary LSPs from selected lightpaths through which the efficiency of channel utilization in the optical links is increased, and the loss rate of LSP requests can be reduced as a result. Both the proposed routing and re-routing schemes are quantitatively evaluated and the effectiveness of those schemes is verified by computer simulation.

As the Internet proliferates, there has been a growing interest in supporting multiparty collaborative applications. It has led to the emergence of many-to-ma ny reliable multicast. Congestion control is a key task in reliable multicast along with error control. However, existing tree-based congestion control schemes such as TRAMCC and MTCP are designed for one-to-many reliable multicast and have some drawbacks when they are used for many-to-many reliable multicast. We propose an efficient congestion control mechanism, MTRMCC, for tree-based many-to-many reliable multicast protocols. The proposed scheme is based on the congestion windowing mechanism and a rate controller is used in addition. The feedback for error recovery is exploited for congestion control as well to minimize the overhead at the receivers. The ACK timer and the NACK timers are set dynamically reflecting the network traffic changes. The rate regulation algorithm in the proposed scheme is designed to help the flows sharing the same link to achieve the fair share quickly. The performance of the proposed scheme is evaluated using network simulator ns-2. The simulation results show that the proposed scheme outperforms TRAMCC in terms of intra-session fairness and supports responsiveness, TCP-friendliness, and scalability.

IP multicast is an efficient means of sending to a group, but the packets are sent unreliably. Mobility complicates the problem because many multicast protocols are inefficient when faced with frequent membership or location change. In this paper, we propose a new protocol to additionally achieve fault recovery of multicast applications in IP internetwork with mobile participants. Unlike many studies which use the basic unicast routing capability of Mobile IP as the foundation, our protocol is built on top of the existing static hosts IP unicast and multicast forwarding services to avoid triangle routing which always occurs in Mobile IP. Relying only on the existing multicast service model and reconstructing the delivery tree every time a multicast member and/or source move is not always a good solution. By applying the ideas of bi-directional tunneled multicast, our protocol attempts to hide host mobility from all other members of the group. Therefore, the multicast distribution tree will not be updated for the sake of member location change. Furthermore, our protocol has near shortest delivery paths like remote subscription protocol. Exploiting the randomized forwarding service called randomcast in the repair process for packet losses, our protocol achieves local recovery and improves robustness. Additionally, our system structure can minimize the request implosion and duplicate replies. Simulation results show that our protocol has the distinct performance advantages in local recovery and robustness by using randomcast. Our protocol can also adapt to the fluctuation of both host movement and the number of mobile members (i.e., having mobility and scalability properties).

In this paper, we study reliable decentralized supervisory control of discrete event systems with a control architecture where certain controllable events are controlled under the conjunctive fusion rule, and certain others are controlled under the disjunctive fusion rule. We first introduce a notion of reliable co-observability with respect to such a partition of the controllable event set. We then prove that reliable co-observability together with Lm(G)-closure and controllability is a necessary and sufficient condition for the existence of a reliable decentralized supervisor under a given partition. Moreover, we present necessary and sufficient conditions for the existence of a partition of the controllable event set under which a given specification language is reliably co-observable.

Several reliability based code search algorithms for maximum likelihood decoding have been proposed. These algorithms search the most likely codeword, using the most reliable information set where the leftmost k (the dimension of code) columns of generator matrix are the most reliable and linearly independent. Especially, D. Gazelle and J. Snyders have proposed an efficient decoding algorithm and this algorithm requires small number of candidate codewords to find out the most likely codeword. In this paper, we propose new efficient methods for both generating candidate codewords and computing metrics of candidate codewords to obtain the most likely codeword at the decoder. The candidate codewords constructed by the proposed method are identical those in the decoding algorithm of Gazelle et al. Consequently, the proposed decoding algorithm reduces the time complexity in total, compared to the decoding algorithm of Gazelle et al. without the degradation in error performance.

Reliable multicast is an interesting application of distributing data to lots of clients at the same time. In heterogeneous environment, it is necessary to adjust the transmitting rate corresponding to the bandwidth of receivers. Placed at a network bottleneck point, an active server can buffer the multicast packets and control the transmitting rate to the downstream multicast receivers independently so as to absorb bandwidth differences. If wireless and wired receivers coexist, the best position for the active server is at the edge of the wired and wireless links because the bandwidth of wireless receivers are lower than that of wired receivers. However, it is not enough that an active server only controls the transmitting rate in such environment because wireless receivers tend to lose packet by the wireless transmission error. This paper proposes a scheme in which the active server independently controls a reliable multicast scheme that is robust against packet loss due to wireless transmission error. Simulation results show that rate-based reliable multicast congestion control is more appropriate than window-based control for wireless links. We also show that FEC applied only to the wireless link improves the throughput of wireless multicast receivers. Finally, we show that combining rate-based reliable multicast congestion control scheme with FEC only for the wireless link makes reliable multicast more practical and friendly with TCP even if packets are lost due to transmission errors.

One of the most important technical problems in reliable multicast protocol is reducing redundant feedback information, e.g. NAKs, to avoid feedback implosion. A number of feedback suppression mechanisms have been proposed to deal with this problem. In the MBONE, which is a virtual multicast network and makes multi-point communication across the Internet feasible, the source link, the links directly connected to or very close to the source, is reported to contribute high percentile packet loss. When a well-known NAK suppression mechanism is applied, in the case of the source link loss, all receivers suffer the same packet loss and NAK suppression mechanism does not work effectively. In this paper we propose a Reliable Multicast Protocol Applying Local FEC, called Local FEC, where the source link loss is recovered with FEC applied locally only to the source link. To investigate performance of our proposed protocol, it is compared with a popular reliable multicast protocol with NAK suppression mechanism. Our performance analysis results with mathematical analysis and computer simulation show that our proposed protocol outperforms the NAK suppression protocol from the viewpoint of scalability and wasted bandwidth.

In this paper, to investigate the processing requirements at each node and offered network load of receiver-based and router-based protocols, we analyze the number of packet transmissions on each link until all receivers receive a packet for an arbitrary multicast-tree topology and packet loss probability considering the correlation between loss events of a packet for different receivers. In order to show the effectiveness of the analytical results, we demonstrate the numerical examples for various conditions. The numerical results show that local recovery protocols, especially router-based protocol can reduce the offered network load due to data packets and their acknowledgements, and can decentralize processing requirement of sending nodes effectively. Further, we reveal the influence of the locations of group senders on the performance of both protocols.

Algorithms are presented for the four elementary arithmetic operations, to perform reliable floating-point arithmetic operations. These arithmetic operations can be achieved by applying residue techniques to the weighted number systems and performed with no accuracy lost in the process of the computing. The arithmetic operations presented can be used as elementary tools (on many existing architectures) to ensure the reliability of numerical computations. Simulation results especially for the solutions of ill-conditioned problems are given with emphasis on the practical usability of the tools.

In the paper, we propose a congestion control scheme for reliable multicast communication which enables TCP fairness and prevents a drop-to-zero problem. The proposed congestion control scheme is rate-based one based on NAKs from receivers and cooperatively works with a flow control scheme. The congestion control scheme consists of two components of a rate-based controller and a selection mechanism of a representative. The rate-based controller runs between the sender and the representative and achieves TCP fairness and fast response to losses at the representative. The selection mechanism of the representative allows the sender to select the representative in a scalable manner, in which the sender makes use of NAKs from receivers to select it. In the paper, we also propose the switchover mechanism of the flow and congestion control schemes which enables the sender to use either of them adaptively based on network situations. When the network is congested, the congestion control scheme works to share network resources fairly with competing TCP flows. Otherwise, the flow control scheme works to adapt the transmission rate to the slowest receiver. We verify the performance of our proposed schemes by using computer simulation.