Throughput Analysis of Large Wireless Networks with Regular Topologies

Using directional antennas to reduce interference and improve throughput in multihop wireless networks has attracted much attention from the research community in recent years. In this paper, we consider the issue of minimum delay broadcast in multirate wireless mesh networks using directional antennas. We are given a set of mesh routers equipped with directional antennas, one of which is the gateway node and the source of the broadcast. Our objective is to minimize the total transmission delay for all the other nodes to receive a broadcast packet from the source, by determining the set of relay nodes and computing the number and orientations of beams formed by each relay node. We propose a heuristic solution with two steps. Firstly, we construct a broadcast routing tree by defining a new routing metric to select the relay nodes and compute the optimal antenna beams for each relay node. Then, we use a greedy method to make scheduling of concurrent transmissions without causing beam interference. Extensive simulations have demonstrated that our proposed method can reduce the broadcast delay significantly compared with the methods using omnidirectional antennas and single-rate transmission. In addition, the results also show that our method performs better than the method with fixed antenna beams. Copyright © 2012 John Wiley & Sons, Ltd.

The vision of Large Scale Network Analysis (LSNA) states on large amounts of network data, which are produced by social media applications like Facebook, Twitter, and the competitive domain of biological networks as well as their needs for network data extraction and analysis. That raises data management challenges which are addressed by biological, data mining and linked (web) data management communities. So far, mainly these domains were considered when identifying research topics and measuring approaches and progress. We argue that an important domain, the Business Network Management (BNM), representing business and (technical) integration data, implicitely linked and available in enterprises, has been neglected. Not only do enterprises need visibilities into their business networks, they need ad-hoc analysis capabilities on them. In this paper, we introduce BNM as domain, which comes with large scale network data. We discuss how linked business data can be made explicit by what we called Network Mining (NM) from dynamic, heterogeneous enterprise environments to combine it to a (cross-) enterprise linked business data network and state on its different facets w.r.t large network analysis and highlight challenges and opportunities.

This paper analyzes the impact of error propagation on the achievable throughput and throughput-delay tradeoff in wireless networks. It addresses the particular class of multihop routing schemes for parallel unicast that achieve a throughput scaling of Θ(n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1/2</sup> ) per node in a network of n nodes. It is shown that in the finite-block-length case, necessitated by finite decoding memory at the nodes, the guaranteed per-node throughput in the network cannot scale better than o (n <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-r</sup> ) per node for any r > 0. This bound on the guaranteed per-node throughput is tighter than the O (1/n) bound shown previously. Instead of focusing on the probability of error for each link, which is intractable, an approach of bounding mutual information is employed to show tight results on the achievable throughput and throughput-delay tradeoffs. It is shown that for multihop transmission protocols, error propagation leads to significant changes in the tradeoff between the throughput T(n) and the delay D(n), compared to previous results. The best known scaling behavior is only D(n) = Θ (n (log n) T(n)) under maximum throughput scaling, where the block length required scales as Ω (log n). When decoding memory at nodes is constrained to be O (log log n), the achievable tradeoff worsens to D(n) = Θ (n (log n) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> T(n)).

One of the traditional MAC protocols used in wireless ad hoc networks is Distributed Coordination Function IEEE 802.11 (DCF). In such protocols, nodes are allowed to access the channel without any base station and omni-directional antennas are used for packet transmission. The main problem in IEEE 802.11 DCF is the existence of silent area which leads to channel spatial reuse reduction and using directional antennas at the nodes can battle this problem. However, using directional antennas itself leads to other problems such as new hidden terminal and deafness problems. In this paper, we propose a new multichannel MAC protocol based on CDMA technique in which directional antennas and CDMA codes are used to specify the channels for different users. In the proposed protocol, a common control channel is used for RTS/CTS handshaking, and other channels are used for data transmission. Simulation results show that the proposed protocol, by using even lower number of codes, improves the network throughput and achieves higher spatial reuse of wireless channel compared with 802.11 DCF, or other traditional protocols such as DMAC (basic Directional MAC) and CDMA based MAC protocols.

Applying directional antennas in wireless ad hoc networks can theoretically achieve higher spatial multiplexing gain and, thus, higher network throughput. However, in practice, deafness, hidden-terminal, and exposed terminal problems are exaggerated with directional antennas, and they cause the degradation of the overall network performance. Although there are several random-access-based medium-access control (MAC) protocols being proposed in the literature for networks with directional antennas, the deafness, hidden-terminal, and exposed terminal problems have yet to be fully solved. In this paper, we present a new MAC protocol called the dual-sensing directional MAC (DSDMAC) protocol for wireless ad hoc networks with directional antennas. Different from existing protocols, the DSDMAC protocol relies on the dual-sensing strategy to identify deafness, resolve the hidden-terminal problem, and avoid unnecessary blocking. The integrity of the DSDMAC protocol is verified and validated using , which is a formal protocol verification and validation tool. We further develop an analytical framework to quantify the performance of the DSDMAC protocol and conduct extensive simulations, which verify the accuracy of the analysis. The protocol verification, analysis, and simulation results show the robustness and superior performance of the DSDMAC protocol, which can achieve a much higher network throughput and lower delay utilizing the spatial multiplexing gain of the directional antennas. The results presented in this paper show that the proposed DSDMAC protocol can substantially outperform the state-of-the-art protocols.

VLSI designs contain very large resistive networks consisting of hundreds of millions (10e11) of resistors. Accurate parasitic extraction and analysis of such large networks is essential in many phases of the VLSI design flow. Existing techniques to analyze large resistive networks using linear solvers, despite recent optimizations, still take prohibitive computation time. In this paper a new technique based on low-distortion embedding to estimate point-to-point effective resistance is presented. Our proposed method employs recently discovered techniques from theoretical computer science to compute an e-approximate resistance embedding matrix from which effective resistances of all node pairs can be estimated as easily as taking the Euclidean norm of column differences. The proposed method runs in almost linear time (linear in the number of resistors), and the accuracy (e) is user specified. The method has been implemented and experimental results on large networks containing upto 10e11 nodes are presented. Compared to existing method using sparse linear solvers, our methods are more than 10 times faster on mesh networks and more importantly given a network of n nodes, allow computation of effective resistance between arbitrary node pairs in O(lg(n)) time (lg denotes logarithm to base 2).

Proposing a centralized algorithm to minimize message broadcasting energy in wireless sensor networks using directional antennas

The limited channel capacity and the varying propagation conditions of radio signals have motivated research for boosting the achievable throughput in wireless networks. Among the effective optimization strategies is to dynamically adjust the packet size either to better suit the channel conditions or to minimize the number of overhead bits in the individual packets. However, multi‐levels of security requirements impose constraints on the data mix in the packet payload and may diminish the gains achievable by contemporary packet‐size optimization schemes. This paper presents a novel bandwidth optimization algorithm for wireless data acquisition networks where strict confidentiality requirements and access restriction policies have to be observed. The algorithm exploits the classification of data in minimizing the number of packet transmissions as well as the overhead within the individual packets. The idea is to combine the transmission of packets based on the time sensitivity and security attributes of the data in the payload. The performance of the proposed algorithm is validated through mathematical analysis and through simulation. The simulation results confirm the effectiveness of the algorithm in boosting data throughput in the network. Copyright © 2010 John Wiley &amp; Sons, Ltd.

In this paper, we consider a device-to-device (D2D) millimeter Wave (mmWave) network that allocates a spectrum band with bandwidth B<inf>c</inf> Hz exclusively to support communication of N cooperative D2D pairs over Rayleigh fading channels. The available bandwidth is divided into N<inf>c</inf> non-overlapping sub-bands. Each node is equipped with a directional antenna that is capable of steering its beam within its field of view. Also, each transmitter can adjust its transmit power. Aiming at maximizing the network throughput, the cooperative D2D pairs form N<inf>c</inf> disjoint coalitions, where the D2D pairs in a particular coalition share the same sub-band for communication and hence cause co-channel interference. We address this question: What is the best coalition among the D2D pairs, the optimal beams steering angles of directional antennas of the D2D pairs within each coalition, and the optimal transmit powers such that the network throughput is maximized? We formulate the network throughput maximization problem, subject to certain constraints, and we propose an iterative method, based on the block coordinate descent (BCD) algorithm, to solve the constrained optimization problem. Specially, we propose a coalitional game approach for coalition formation among the D2D pairs. We numerically investigate the effects of different system parameters (e.g., N, N<inf>c</inf>, the antenna gain, the maximum allowed total transmit power), as well as the impact of optimizing coalition formation only, and optimizing transmit power only, on the network throughput maximization.

Previous results show that a node's throughput scales poorly as the network size increases when every node has traffic. However, in many cases, only a fraction of nodes in large networks have data to send or receive at any given time, while other nodes can act as relays/routers. Therefore, in this paper, we study the scaling behavior from a user's viewpoint (a user is a node with traffic). We first derive an upper bound on per user throughput. To derive the lower bound, we propose a simple scheduling scheme that enables users to cooperate with relay nodes and fully utilize the networks capacity. We show that per user throughput depends on the network size, the number of users, and the node deployment schemes, and is in general much more optimistic. Our scheme also sheds light on designing efficient cooperation protocols in heterogeneous networks and cognitive radio networks.

This paper deals with two representative unbalanced traffic cases for two-hop wireless relay access systems employing network coding and a slotted ALOHA protocol. Network coding is a recent and highly regarded technology for capacity enhancement with multiple unicast and multisource multicast networks. We have analyzed the performance of network coding on a two-hop wireless relay access system employing the slotted ALOHA under a balanced bidirectional traffic. The relay nodes will generally undergo this unbalanced multidirectional traffic but the impact of this unbalanced traffic on network coding has not been analyzed. This paper provides closed-form expressions for the throughput and packet delay for two-hop unbalanced bidirectional traffic cases both with and without network coding even if the buffers on nodes are unsaturated. The analytical results are mainly derived by solving queueing systems for the buffer behavior at the relay node. The results show that the transmission probability of the relay node is a design parameter that is crucial to maximizing the achievable throughput of wireless network coding in slotted ALOHA on two-hop unbalanced traffic cases. Furthermore, we show that the throughput is enhanced even if the traffic at the relay node is unbalanced.

Provisioning of high throughput in wireless mesh networks (WMNs) is a challenging issue for medium access control (MAC) protocol. This is due to not only some difficult problems present in such networks such as the hidden and exposed terminal problems but also the fact that a WMN is often used as a backbone network requiring more reliable and efficient performance. Note that multi-channel based MAC protocols were proposed in the literature to handle the hidden and exposed terminal problems in multi-hop wireless ad hoc networks. Here this approach is advocated for WMNs since many literature studies show that it can much outperform the singlechannel based MAC protocols but at the expense of increased implementation complexity, which however should be acceptable in backbone WMNs. However, most existing multi-channel based MAC protocols use dedicated control channels (DCC). DCCs not only causes channel wastage but also may become a performance bottlenecks, both of which are undesirable for WMNs. In this paper, we discuss a new MAC scheme which does not use any DCCs and only requires one transceiver per node for the implementation. The simulation studies show that this scheme can outperform the one using DCCs especially in the case of heavy traffic loads.

Slotted Aloha and carrier sensing multiple access (CSMA) are effective random access protocols, which can also be important elements of more advanced media access protocols. In this paper, we investigate slotted Aloha and CSMA protocols in a cognitive radio network, where primary users have higher priority than secondary users and secondary users need to monitor the channel to avoid interference to the primary users, it is thus proposed that slotted Aloha is used for primary users to access the channel and secondary users use slotted CSMA to sense the time slots of slotted Aloha and transmit their packets during idle time slots. A Rayleigh fading channel is considered and we derive the throughput of slotted Aloha and CSMA for the primary and secondary users.

Many applications in wireless networks impose locally distributed traffic on the network. We consider the effect of traffic localization on throughput of large wireless networks in the scaling sense. We show that by careful exploitation of traffic localization, one can enhance the throughput of various schemes in wireless networks. Also, the important case of Small World traffic distribution in wireless networks is addressed. In this type of traffic, in addition to the local traffic, a non-negligible amount of global traffic should be handled by the network. It is shown that a non-negligible amount of network-wide traffic can be tolerated by network without any performance degradation in the scaling sense.

Interference optimization for multicast and broadcast traffics in multi-radio multi-channel WMNs equipped with directional antennas