Assignment Protocol Research Articles

Multihop Cellular Networks: Dynamic Channel Assignment and Routing Protocol for Improving Performance

Multihop cellular Networks has the problem of channel assignment when connections are established between the adjacent cells and due to more number of nodes in the path between the sender and the receiver relay delay occurs and cause unwanted delay in the overall end to end communication. To overcome the problems associated with the relay delay and the overall performance in the Multihop Cellular Networks a new protocol is introduced which combines the merits of both the modified Minimum Slot Waiting First Algorithm and the modified Distance Vector Routing. Through the proposed new protocol, we can provide solution for the problem of routing and relay delay in Multihop Cellular Networks and the performance of the packet transmission can be improved.

Structural Integrity of the B24 Site in Human Insulin Is Important for Hormone Functionality

Despite the recent first structural insight into the insulin-insulin receptor complex, the role of the C terminus of the B-chain of insulin in this assembly remains unresolved. Previous studies have suggested that this part of insulin must rearrange to reveal amino acids crucial for interaction with the receptor. The role of the invariant Phe(B24), one of the key residues of the hormone, in this process remains unclear. For example, the B24 site functionally tolerates substitutions to D-amino acids but not to L-amino acids. Here, we prepared and characterized a series of B24-modified insulin analogues, also determining the structures of [D-HisB24]-insulin and [HisB24]-insulin. The inactive [HisB24]-insulin molecule is remarkably rigid due to a tight accommodation of the L-His side chain in the B24 binding pocket that results in the stronger tethering of B25-B28 residues to the protein core. In contrast, the highly active [D-HisB24]-insulin is more flexible, and the reverse chirality of the B24C(α) atom swayed the D-His(B24) side chain into the solvent. Furthermore, the pocket vacated by Phe(B24) is filled by Phe(B25), which mimics the Phe(B24) side and main chains. The B25→B24 downshift results in a subsequent downshift of Tyr(B26) into the B25 site and the departure of B26-B30 residues away from the insulin core. Our data indicate the importance of the aromatic L-amino acid at the B24 site and the structural invariance/integrity of this position for an effective binding of insulin to its receptor. Moreover, they also suggest limited, B25-B30 only, unfolding of the C terminus of the B-chain upon insulin activation.

Auto Rate Dynamic Channel Assignment Protocol in Ad Hoc Networks

Auto Rate Dynamic Channel Assignment Protocol in Ad Hoc Networks

Fourier-space TEM reconstructions with symmetry adapted functions for all rotational point groups

A general-purpose and simple expression for the coefficients of symmetry adapted functions referred to conveniently oriented symmetry axes is given for all rotational point groups. The expression involves the computation of reduced Wigner-matrix elements corresponding to an angle specific to each group and has the computational advantage of leading to Fourier-space TEM (transmission electron microscopy) reconstruction procedures involving only real valued unknowns. Using this expression, a protocol for ab initio view and center assignment and reconstruction so far used for icosahedral particles has been tested with experimental data in other point groups.

Adaptive TDMA slot assignment protocol for vehicular ad-hoc networks

This paper proposes a novel adaptive time division multiple access (TDMA) slot assignment protocol (ATSA) for vehicular ad-hoc networks. ATSA divides different sets of time slots according to vehicles moving in opposite directions. When a node accesses the networks, it choices a frame length and competes a slot based on its direction and location to communication with the other nodes. Based on the binary tree algorithm, the frame length is dynamically doubled or shortened, and the ratio of two slot sets is adjusted to decrease the probability of transmission collisions. The theoretical analysis proves ATSA protocol can reduce the time delay at least 20% than the media access control protocol for vehicular ad-hoc networks (VeMAC) and 30% than the ad-hoc. The simulation experiment shows that ATSA has a good scalability and the collisions would be reduced about 50% than VeMAC, channel utilization is significantly improved than several existing protocols.

Efficient Role Assignment Scheme for Multichannel Wireless Mesh Networks

a wireless mesh network (WMN) is cost-effective access network architecture. The performance of multi-hop communication quickly reduces as the number of hops becomes larger. Nassiri et al. proposed a Molecular MAC protocol for autonomic assignment and use of multiple channels to improve network performance. In the Molecular MAC protocol, each node forms a shortest path-spanning tree to a gateway node linked to a wired Internet. After a tree is formed, the nodes with an even-numbered depth and an odd-numbered depth are assigned with the roles of a nucleus and an electron, respectively. After such roles are assigned, each nucleus selects an idle channel. However, this protocol has the following drawback; since the nodes with an even-numbered depth are assigned with the role of a nucleus, there are many nuclei in the topology. The number of assigned channels tends to increase, since each nucleus selects an idle channel that is not currently being occupied by its neighboring nuclei. In wireless communications networks, channels are very important resources. Thus, it is necessary to assign the minimum number of channels as little as possible. To do so, this paper proposes an efficient role assignment scheme, which can reduce the number of assigned channels by reducing the number of nodes assigned as nuclei and preventing nodes within the transmission range of each other from becoming nuclei. Based on various simulation results, the proposed scheme was verified.

Interference Aware Channel Assignment Scheme in Multichannel Wireless Mesh Networks

Wireless mesh networks (WMNs) are gaining significant attention to provide wireless broadband service. Nodes in a wireless mesh network can communicate with each other directly or through one or more intermediate nodes. Because of multi-hop transmissions with multiple contending and compet¬ing channels, performance of wireless mesh networks decreases. Supporting high performance is an important challenge in multi-hop mesh networks. Nassiri et al. proposed a Molecular MAC protocol for autonomic assignment and use of multiple channels to improve network performance. In the Molecular MAC protocol, nodes are either nuclei or electrons in an atom. Neighboring atoms use orthogonal channels to operate in parallel data transmissions. Each nucleus selects an idle channel that is not currently being occupied by its neighboring atoms with the assistance from electrons in the same atom. However, this protocol has the following drawback; since a nucleus allocates a channel with help from the electrons in its own transmission range, it is not able to recognize the existence of those atoms in the interference range. Therefore, allocating the same channel to neighboring atoms results in the deterioration of network performance. In order to resolve this problem, we propose a channel allocation scheme with the interference issue taken into account. Based on various simulation results, the proposed scheme was verified that different channels could be allocated to those neighboring atoms in the interference range.

An efficient joint channel assignment and QoS routing protocol for IEEE 802.11 multi-radio multi-channel wireless mesh networks

With the emerging of video, voice over IP (VoIP) and other real-time multimedia services, more and more people pay attention to quality of service (QoS) issues in terms of the bandwidth, delay and jitter, etc. As one effective way of broadband wireless access, it has become imperative for wireless mesh networks (WMNs) to provide QoS guarantee. Existing works mostly modify QoS architecture dedicated for ad hoc or sensor networks, and focus on single radio and single channel case. Meanwhile, they study the QoS routing or MAC protocol from view of isolated layer. In this paper, we propose a novel cross-layer QoS-aware routing protocol on OLSR (CLQ-OLSR) to support real-time multimedia communication by efficiently exploiting multi-radio and multi-channel method. By constructing multi-layer virtual logical mapping over physical topology, we implement two sets of routing mechanisms, physical modified OLSR protocol (M-OLSR) and logical routing, to accommodate network traffic. The proposed CLQ-OLSR is based on a distributed bandwidth estimation scheme, implemented at each node for estimating the available bandwidth on each associated channel. By piggybacking the bandwidth information in HELLO and topology control (TC) messages, each node disseminates information of topology and available bandwidth to other nodes in the whole network in an efficient way. From topology and bandwidth information, the optimized path can be identified. Finally, we conduct extensive simulation to verify the performance of CLQ-OLSR in different scenarios on QualNet platform. The results demonstrate that our proposed CLQ-OLSR outperforms single radio OLSR, multi-radio OLSR and OLSR with differentiated services (DiffServ) in terms of network aggregate throughput, end-to-end packet delivery ratio, delay and delay jitter with reasonable message overheads and hardware costs. In particular, the network aggregate throughput for CLQ-OLSR can almost be improved by 300% compared with the single radio case.

Hospital Status Admission Determination

To evaluate methods of logic, set theory, and information theory in developing a conceptual framework that would be useful in an educational process as well as in developing a consistent and rational method for hospital status determination. To implement these methods on a daily basis in interaction with nurse case managers, physicians, and in documentation of the process. A tertiary private, not-for-profit institution within the department of case management and utilization review. These methods were well accepted by those involved in the decision process and allowed a Case Management Assignment Protocol to function well in the hospital environment with a low level of disagreement and conflict. Medical information can be processed effectively with conceptual models of logic and information theory. The used commercial screening systems are described well by set theory and are intersecting sets of patient variables and characteristics. These methods can be used in educational processes in practice settings apart from those using the Case Management Assignment Protocol. It provides a basis for evaluation of patients' presentations that use important factors such as clinical uncertainty, patient specific data, and reference to preexisting admission criteria.

Direct Sequential Hit Strategy for Unambiguous and Accurate Backbone Assignment of 13C/15N Labeled Proteins

Backbone assignment is the very first and key requirement of any study of protein by NMR. However, the process is generally made difficult by severe amide shift degeneracy commonly exhibited by higher MW (>15 kDa in size) alpha-helical and structurally disordered proteins. Pulse sequences and novel strategies have been reported earlier relying heavily on well dispersed nitrogen chemical shifts. In this context, we present here extension of HNN and HN(C)N based assignment protocol (Panchal et al., J Biomol NMR 20:135–147, 2001) by exploiting carbon chemical shifts to resolve the ambiguities arising because of amide 15N/1H shift degeneracy. The resulted modifications have been termed as hNCAnH and hNcoCAnH, respectively and based on the complementary and mutually exclusive information contained in these two spectra, an efficient strategy -named here as strategy—has been presented for unambiguous and accurate backbone assignment of 13C/15N labeled proteins. The strategy provides directly the coordinates of sequential amide peaks (H i−1, N i−1 and H i+1, N i+1) for a particular amide cross peak (H i , N i ), just after performing the simple manual peak picking step. Thus, the sequential (i to i − 1 or i to i + 1) connectivities between the backbone amide cross peaks (H i , N i ) are established directly without making cumbersome search through various planes of the 3D spectrum as is the case with other presently used approaches for backbone assignment. The strategy have been demonstrated here using an intrinsically unfolded 164-residue protein named DLC1 binding domain of nNOS (residues 134–298).

Rapid protein global fold determination using ultrasparse sampling, high-dynamic range artifact suppression, and time-shared NOESY.

In structural studies of large proteins by NMR, global fold determination plays an increasingly important role in providing a first look at a target's topology and reducing assignment ambiguity in NOESY spectra of fully protonated samples. In this work, we demonstrate the use of ultrasparse sampling, a new data processing algorithm, and a 4-D time-shared NOESY experiment (1) to collect all NOEs in (2)H/(13)C/(15)N-labeled protein samples with selectively protonated amide and ILV methyl groups at high resolution in only four days, and (2) to calculate global folds from this data using fully automated resonance assignment. The new algorithm, SCRUB, incorporates the CLEAN method for iterative artifact removal but applies an additional level of iteration, permitting real signals to be distinguished from noise and allowing nearly all artifacts generated by real signals to be eliminated. In simulations with 1.2% of the data required by Nyquist sampling, SCRUB achieves a dynamic range over 10000:1 (250× better artifact suppression than CLEAN) and completely quantitative reproduction of signal intensities, volumes, and line shapes. Applied to 4-D time-shared NOESY data, SCRUB processing dramatically reduces aliasing noise from strong diagonal signals, enabling the identification of weak NOE crosspeaks with intensities 100× less than those of diagonal signals. Nearly all of the expected peaks for interproton distances under 5 Å were observed. The practical benefit of this method is demonstrated with structure calculations for 23 kDa and 29 kDa test proteins using the automated assignment protocol of CYANA, in which unassigned 4-D time-shared NOESY peak lists produce accurate and well-converged global fold ensembles, whereas 3-D peak lists either fail to converge or produce significantly less accurate folds. The approach presented here succeeds with an order of magnitude less sampling than required by alternative methods for processing sparse 4-D data.

Probabilistic quality-aware routing in cognitive radio networks under dynamically varying spectrum opportunities

In this paper, we introduce a probabilistic routing metric that considers the peculiar characteristics of the operating environment of cognitive radio networks (CRNs). This metric captures the dynamic changes in channel availabilities due to the randomness of primary user’s activity and the rich channel diversity due to the fact that a CRN is expected to operate over highly separated frequency channels with different propagation characteristics. Our metric, Probability of Success (PoS), statistically quantifies the chances of a successful cognitive radio (CR) packet transmission over a given channel. Based on the PoS metric, we propose a joint probabilistic routing and channel assignment protocol for multi-hop CRNs that attempts at selecting the path with the maximum probability of success among all possible paths for a given CR source-destination pair. Selecting such a path results in minimizing the number of disruptions to CR packet transmissions, which consequently improves network throughput. Simulation results verify the significant throughput improvement achieved by our protocol compared to reference CRN routing protocols.

Facile backbone (1H, 15N, 13Ca, and 13C′) assignment of 13C/15N-labeled proteins using orthogonal projection planes of HNN and HN(C)N experiments and its automation

Recently, we introduced an efficient high-throughput protocol for backbone assignment of small folded proteins based on two-dimensional (2D) projections of HN(C)N suite of experiments and its automation [Borkar et al., J. Biomol. NMR 2011, 50(3), 285-297]. This strategy provides complete sequence-specific assignment of backbone ((1)H, (15)N, (13)C(α), and (13)C') resonances in less than a day; thus, it has great implications for high-throughput structural proteomics. However, in cases when such small folded protein exhibits substantial amide (1)H shift degeneracy (typically seen in alpha-helical proteins), the strategy may fail or lead to ambiguities. Another limitation is with respect to the identification of checkpoints from the variants of 2D-hncNH spectrum. For example, a protein with many GG, GA, AA, SS, TS, TT, and TS types of dipeptide stretches along its sequence, thus the identification of NH cross-peak corresponding to second G, A, S, or T becomes difficult. In this backdrop, we present here two improvements to enhance the utility of the proposed high-throughput AUTOmatic Backbone Assignment protocol: (i) use of 2D-hNnH spectrum and its variants that display additional (1)H-(15)N correlations and thus help to resolve ambiguities arising because of amide (1)H shift degeneracy and (ii) optimization of the τ(CN) delay in the 2D-hncNH experiment that, when properly adjusted, is observed to help remove ambiguities in the identification of the checkpoints. These improvements have also been incorporated in the automation program AUTOmatic Backbone Assignment. Finally, the performance of the strategy and the automation has been demonstrated using the chicken SH3 domain protein.

Reduced dimensionality 3D HNCAN for unambiguous HN, CA and N assignment in proteins

We present here an improvisation of HNN (Panchal, Bhavesh et al., 2001) called RD 3D HNCAN for backbone (HN, CA and 15N) assignment in both folded and unfolded proteins. This is a reduced dimensionality experiment which employs CA chemical shifts to improve dispersion. Distinct positive and negative peak patterns of various triplet segments along the polypeptide chain observed in HNN are retained and these provide start and check points for the sequential walk. Because of co-incrementing of CA and 15N, peaks along one of the dimensions appear at sums and differences of the CA and 15N chemical shifts. This changes the backbone assignment protocol slightly and we present this in explicit detail. The performance of the experiment has been demonstrated using Ubiquitin and Plasmodium falciparum P2 proteins. The experiment is particularly valuable when two neighboring amino acid residues have nearly identical backbone 15N chemical shifts.

How to improve the peer review method: Free-selection vs assigned-pair protocol evaluated in a computer networking course

This study provides field research evidence on the efficiency of a “free-selection” peer review assignment protocol as compared to the typically implemented “assigned-pair” protocol. The study employed 54 sophomore students who were randomly assigned into three groups: Assigned-Pair (AP) (the teacher assigns student works for review to student pairs), Free-Selection (FS) (students are allowed to freely explore and select peer work for review), and No Review (NR) (control group). AP and FS student groups studied and reviewed peer work in the domain of Computer Networking, supported by a web-based environment designed to facilitate the two peer review protocols. Our results indicate that students following the Free Selection protocol demonstrate (a) better domain learning outcomes, and (b) better reviewer skills, compared to the AP condition. Overall, the study analyzes the benefits and shortcomings of the FS vs AP review assignment protocol, providing evidence that the FS condition can be multiply beneficial to students who engage in peer review activities.

F-DSA: A Fast Dynamic Slot Assignment Protocol for Ad Hoc Networks

In this letter, we propose a fast dynamic slot assignment (F-DSA) protocol to reduce timeslot access delay of a newly arrived node in ad hoc networks. As there is no central coordinator, a newly arrived node needs separate negotiation with all the neighboring nodes for assigning slots to itself. Thus, it may result in network join delay and this becomes an obstacle for nodes to dynamically join and leave networks. In order to deal with this issue better, F-DSA simplifies the slot assignment process. It provides frequent opportunities to assign slots by using mini-slots to share control packets in a short time. Numerical analysis and extensive simulation show that F-DSA can significantly reduce the timeslot access delay compared with other existing slot assignment protocols. In addition, we investigate the effect of the mini-slot overhead on the performance.

Truthful Relay Assignment for Cooperative Communication in Wireless Networks with Selfish Source-Destination Pairs

Cooperative communication is shown to be a promising technology to significantly increase the capacity of wireless networks. Due to the competition among multiple source-destination pairs for the same relay node set in the relay assignment problem, each pair may cheat others to achieve a more individual revenue. However, the cheating behavior may decrease the overall performance of the network greatly. Thus, there is a challenge for designing a truthful protocol that maximizes a pair’s payoff only when this pair reveals its true individual information. In this paper, we propose a relay assignment protocol (RA-VCG) for cooperative communication to maximize the total social value (i.e., the total true value of all pairs) while guaranteeing truthfulness in an auction-theoretic sense by charging each pair an extra payment. Specially, RA-VCG implements a variation of the well-known VCG mechanism for the truthful relay assignment problem in the network with selfish source-destination pairs. Then, we prove the validity of this protocol and also show several surprising properties (such as no positive transfer and individual rationality) associated with this protocol. The simulation results show that the total social value achieved when each node takes untruthfully is about 23.3% less than that achieved when nodes behave truthfully.

A Quality of Service Supported Time Division Multiple Access Slot Assignment Protocol with Cross Layer Design

A Quality of Service Supported Time Division Multiple Access Slot Assignment Protocol with Cross Layer Design

Capacity and Outage Analysis of MIMO and Cooperative Communication Systems in Underground Tunnels

In underground mine and road tunnels, multipath fading is much more severe than in the terrestrial wireless channels. To overcome the multipath fading in underground tunnels, MIMO (Multiple Input Multiple Output) and Cooperative Communication system can be utilized. Since the underground channel characteristics are significantly different from those in terrestrial environments, the channel capacity and the outage behavior of such systems need to be investigated based on underground tunnel channel models, which had not been addressed by the research community yet. In this paper, the capacity distribution and outage probability of MIMO and cooperative communication systems are investigated in underground tunnel environments. Explicit formulas of the capacity distribution and outage probability are developed as functions of environmental conditions and system configurations. Based on the capacity and outage analysis in underground tunnels, the optimal MIMO antenna geometry design scheme is proposed for MIMO systems; and the cooperative relay assignment protocol is developed for cooperative communication systems. Simulations are conducted to validate the theoretical results.

Performance analysis of multicast routing and wavelength assignment protocol with dynamic traffic grooming in WDM networks

The need for on-demand provisioning of wavelength-routed channels with service-differentiated offerings within the transport layer has become more essential because of the recent emergence of high bit rate Internet protocol IP network applications. Diverse optical transport network architectures have been proposed to achieve the above requirements. This approach is determined by fundamental advances in wavelength division multiplexing WDM technologies. Because of the availability of ultra long-reach transport and all-optical switching, the deployment of all-optical networks has been made possible. The concurrent transmission of multiple streams of data with the assistance of special properties of fiber optics is called WDM. The WDM network provides the capability of transferring huge amounts of data at high speeds by the users over large distances. There are several network applications that require the support of QoS multicast, such as multimedia conferencing systems, video-on-demand systems, real-time control systems, etc. In a WDM network, the route decision and wavelength assignment of lightpath connections are based mainly on the routing and wavelength assignment RWA. The multicast RWA's task is to maximize the number of multicast groups admitted or minimize the call-blocking probability. The dynamic traffic-grooming problem in wavelength-routed networks is generally a two-layered routing problem in which traffic connections are routed over lightpaths in the virtual topology layer and lightpaths are routed over physical links in the physical topology layer. In this paper, a multicast RWA protocol for capacity improvement in WDM networks is designed. In the wavelength assignment technique, paths from the source node to each of the destination nodes and the potential paths are divided into fragments by the junction nodes and these junction nodes have the wavelength conversion capability. By using the concept of fragmentation and grouping, the proposed scheme can be generally applied for the wavelength assignment of multicast in WDM networks. An optimized dynamic traffic grooming algorithm is also developed to address the traffic grooming problem in mesh networks in the multicast scenario for maximizing the resource utilization and minimizing the blocking probability. Copyright © 2011 John Wiley & Sons, Ltd.