Information-centric networking has been touted as an alternative to the current Internet architecture. Our work addresses a crucial part of such a proposal, namely the design of a network node within an information-centric networking architecture. Special attention is given in providing a platform for development and experimentation in an emerging network research area; an area that questions many starting points of the current Internet. In this paper, we describe the service model exposed to applications and provide background on the operation of the platform. For illustration, we present current efforts in deployment and experimentation with demo applications presented, too.

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We study the use of network coding to speed up content distribution in peer-to-peer (P2P) networks. Our goal is to get the underlying reason for network coding's improved performance in P2P content distribution and to optimize resource consumption of network coding. We observe analytically and experimentally that in pure P2P networks, a considerable amount of data is sent multiple times from one peer to another when there are multiple paths connecting those two particular peers. Network coding, on the other hand, when applied at upstream peers, eliminates information duplication on paths to downstream peers, which results in more efficient content distribution. Based on that insight, we propose a network coder placement algorithm which achieves comparable distribution time as network coding, yet substantially reduces the number of encoders compared to a pure network coding solution in which all peers have to encode. Our placement method puts encoders at critical network positions to eliminate information duplication the most, thus, effectively shortens distribution time with just a portion of encoders.

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Lately, access loads on servers are increasing due to larger content size and higher request frequency in content distribution networks. Breadcrumbs (BC), an architecture with guidance information for locating a content cache, is designed to reduce the server load and to form content-oriented network autonomously in cooperation with cached contents over IP network. We also proposed Breadcrumbs+ which solves BC's endless routing loop problem. However, Breadcrumbs takes only a passive approach; BC entries are created only when a content is downloaded and only at routers on the download path but not at any other routers. We expect that active and adaptive control of guidance information with simple complexity improves its performance with keeping scalability. In this paper, we propose Active Breadcrumbs which achieves efficient content retrieval and load-balancing through active and adaptive control of guidance information by cache-nodes themselves. In addition, we show the effectiveness of Active Breadcrumbs through the extensive computer simulation.

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In DHT network, a node can get/put a requested data by only log N look-up steps. However, conventional DHT network only supports single query look-up to search data. From the reason, each node in a DHT network must execute look-up process for each query even if a large number of put and get operations are executed. Therefore, this results in high network load in massive data management such as MapReduce, sensor network, and web information. To address the problem, we propose multiple queries look-up architecture using range information feedback (MARIF). MARIF extends the conventional KBR protocol to supports range information that is a scope of ID space a node keeps. When a source node receives range information from a destination node, the source node checks all queries in the range information and forwards queries matching the range information to the destination node directly. This effectively reduces the number of look-up queries and the network load for the IP network. In addition, MARIF can be implemented into conventional DHT networks and can easily be combined to effective DHT routing algorithms such as Chord, Kademlia, Pastry, and one-hop DHT. In evaluation, we implement MARIF into three DHT networks and compare its performance with that of conventional query bundling mechanisms based on the KBR protocol. The results show that MARIF reduces by up to 40% the total number of forwarding queries to put data compared with other mechanisms. In addition, MARIF saves the number of forwarding queries per look-up process by up to 85% compared to other mechanisms with low bundling overhead.

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Delay and Disruption Tolerant Networks (DTN) can provide an underlying base to support mobility environments. DTN is equipped with advanced features such as custody transfer and hop by hop routing which can tackle the frequent disconnections of mobile devices by buffering bundles and dynamically making hop-by-hop routing decisions under intermittent connectivity environment. In this paper, we have proposed a DTN routing protocol HALF (Handoff-based And Limited Flooding) which can manage and improve performance of disrupted and challenging communication between mobile nodes in the presence of an infrastructure network consisting of fixed interconnected nodes (routers). HALF makes use of the general handoff mechanisms intended for the IP network, in a DTN way and also integrates a limited flooding technique to it. Simulation results show that HALF attains better performance than other existing DTN routing protocols under diverse network conditions. As the traffic intensity changes from low to high, delivery ratio of other DTN routing protocols decreased by 50% to 75% whereas in HALF such ratio is reduced by less than 5%. HALF can deliver about 3 times more messages than the other protocols when the disrupted network has to deal with larger size of messages. If we calculate the overhead ratio in terms of ‘how many extra (successful) transfer’ is needed for each delivery, HALF gives less than 20% overhead ratio while providing a good delivery ratio.

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Resource discovery is an essential function for distributed mobile applications integrated in vehicular communication systems. Key requirements of the mobile resource discovery are wide-area geographic-based discovery and scalable resource discovery not only inside a vehicular ad-hoc network but also through the Internet. While a number of resource discovery solutions have been proposed, most of them have focused on specific scale of network. Furthermore, managing a large number of mobile resources in the Internet raises a scalability issue due to the mobility of vehicles. In this paper, we design a solution to wide area geographical mobile resource discovery in heterogeneous networks composed of numerous mobile networks possibly connected to the Internet. The proposed system relies on a hierarchical publish-subscribe architecture and geographic routing so that users can locate resources according to geographical coordinates without scalability issue. Furthermore we propose a location management mechanism for mobile resources, which enables to reduce periodic updates of geographical location. Numerical analysis and simulation results show that our system can discover mobile resources without overloading both mobile network and the Internet.

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In order to prevent the degradation of TCP performance while traversing two WLANs, we present an implementation design of an inter-domain TCP handover method based on cross-layer and multi-homing. The proposed handover manager (HM) in the transport layer uses two TCP connections previously established via two WLANs (multi-homing) and switches the communication path between the two connections according to the handover trigger and the comparison of new/old APs. The handover trigger and comparison are conducted by assessing the wireless link quality using the frame-retry information obtained from the MAC layer (cross-layer). In a previous study, we proposed a preliminary concept for this method and evaluated its functional effectiveness through simulations. In the present study, we design an implementation considering a real system and then examine the effective performance in a real environment because a real system has several system constraints and suffers from fluctuations in an actual wireless environment. Indeed, depending on the cross-layer design, the implementation often degrades the system performance even if the method exhibits good functional performance. Moreover, the simple assessments of wireless link quality in the previous study indicated unnecessary handovers and inappropriate AP selection in a real environment. Therefore, we herein propose a new architecture that performs cross-layer collaboration between the MAC layer and the transport layer while avoiding degradation of system performance. In addition, we use a new assessment scheme of wireless link quality, i.e., double thresholds of frame retry and comparison of frame retry ratio, in order to prevent handover oscillation caused by fluctuations in the wireless environment. The experimental results demonstrate that the prototype system works well by controlling two TCP connections based on assessments of wireless link quality thereby achieving efficient inter-domain TCP handover in a real WLAN environment.

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This paper proposes a session state migration architecture for flexible server consolidation. One of technical challenges is how to split a session state from a connection and bind the session state to another connection in any servers. A conventional server and client application assumes that a session state is statically bound to a connection once the connection has been established. The proposed architecture reduces the migration latency, compared to an existing study by splitting the session state from the connection. This paper classifies common procedures of session state migration for various services. The session state migration architecture enables service providers to conduct server maintenance at their own convenience, and to conserve energy consumption at servers by consolidating them. A simulation to evaluate server consolidation reveals that the session state migration reduces the number of servers for accommdating users, compared to virtual machine migration. This paper also shows implementation of the session state migration architecture. Experimental results reveal that the impact caused by the proposed architecture on real-time applications is small.

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We present the design of a secure identifier-based inter-domain routing, SIR, for the identifier/locator split network. On the one hand, SIR is a distributed path-vector protocol inheriting the flexibility of BGP. On the other hand, SIR separates ASes into several groups called trust groups, which assure the trust relationships among ASes by enforceable control and provides strict isolation properties to localize attacks and failures. Security analysis shows that SIR can provide control plane security that can avoid routing attacks including some smart attacks which S-BGP/soBGP can be deceived. Meanwhile, emulation experiments based on the current Internet topology with 47,000 ASes from the CAIDA database are presented, in which we compare the number of influenced ASes under attacks of subverting routing policy between SIR and S-BGP/BGP. The results show that, the number of influenced ASes decreases substantially by deploying SIR.

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A botnet attacks any Victim Hosts via the multiple Command and Control (C&C) Servers, which are controlled by a botmaster. This makes it more difficult to detect the botnet attacks and harder to trace the source country of the botmaster due to the lack of the logged data about the attacks. To locate the C&C Servers during malware/bot downloading phase, we have analyzed the source IP addresses of downloads to more than 90 independent Honeypots in Japan in the CCC (Cyber Clean Center) dataset 2010 comprising over 1 million data records and almost 1 thousand malware names. Based on GeoIP services, a Time Zone Correlation model has been proposed to determine the correlation coefficient between bot downloads from Japan and other source countries. We found a strong correlation between active malware/bot downloads and time zone of the C&C Servers. As a result, our model confirms that malware/bot downloads are synchronized with time zone (country) of the corresponding C&C Servers so that the botmaster can be possibly traced.

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Rateless erasure code is an error correction code that is able to encode a message of k uncoded symbols into an infinite number of coded symbols. One may reconstruct the original message from any k(1+ε) coded symbols, where ε denotes the decoding inefficiency. This paper proposes a hybrid code that combines the stepping code and random code and name it as Stepping-Random (SR) code. The Part I (first k) coded symbols of SR code are generated with stepping code. The rest of the coded symbols are generated with random code and denoted as Part II coded symbols. The numerical results show that the new hybrid code is able to achieve a complete decoding with no extra coded symbol (ε=0) if all the Part I coded symbols are received without loss. However, if only a portion of Part I coded symbols are received, a high probability of complete decoding is still achievable with k+10 coded symbols from the combination of Part I and II. SR code has a decoding complexity of O(k) in the former and O((βk)³) in the latter, where β∈R for 0≤β≤1, is the fraction of uncoded symbols that fails to be reconstructed from Part I coded symbols.

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In this paper, an area-efficient decoder architecture is proposed for the quasi-cyclic low-density parity check (QC-LDPC) codes specified in the IEEE 802.16e WiMAX standard. The decoder supports all the code rates and codeword lengths defined in the standard. In order to achieve low area and maximize hardware utilization, the decoder utilizes 4 decoding function units, which is the greatest common divisor of the expansion factors. In addition, the decoder adopts a novel scheduling scheme named stride scheduling, which stores the extrinsic messages in non-sequential order to replace the conventional complex flexible permutation network with simple small-sized cyclic shifters and also minimize the number of memory accesses. To further minimize the complexity, the number of extrinsic memory instances for 24 block columns is reduced to 5 banks by identifying independent sets. All the memory instances used in the decoder are single-port memories which cost less area and price compared to dual-port ones. Finally, the decoding function units have partially parallel structure to make the decoding throughput sufficiently over the requirement of the WiMAX standard. The proposed decoder is synthesized with 49K equivalent gates and 54,144bits of memory, and the implementation occupies 0.40mm² in a 65nm CMOS technology.

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In a multihop wireless network, wireless interference is a crucial factor in the maximum multiflow (MMF) problem, which studies the maximum throughput between multiple pairs of sources and sinks with a link schedule to support it. In this paper, we observe that network coding could help to decrease the impact of wireless interference, and thus propose a framework to study the MMF problem for multihop wireless networks with network coding. Firstly, a network model is established to describe the new conflict relations and schedulability modified by network coding. Next, we formulate the MMF problem to compute the maximum throughput of multiple unicast flows supported by the multihop wireless network with network coding, and show that its capacity region could be enlarged by performing network coding. Finally, we show that determining the capacity region of a multihop wireless network with network coding is an NP-hard problem, and thus propose a greedy heuristic algorithm, called coding-first collecting (CFC), to determine a capacity subregion of the network. We also show that finding an optimal hyperarc schedule to meet a given link demand function is NP-hard, and propose a polynomial algorithm, called coding-first scheduling (CFS), to find an approximate fractional hyperarc schedule in the multihop wireless network with network coding. A numerical analysis of a grid wireless network and a random wireless network is presented to demonstrate the efficiencies of the CFC algorithm and the CFS algorithm based on the framework.

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The capacity of general mobile ad hoc networks (MANETs) remains largely unknown up to now, which significantly hinders the development and commercialization of such networks. Available throughput capacity studies of MANETs mainly focus on either the order sense capacity scaling laws, the exact throughput capacity under a specific algorithm, or the exact throughput capacity without a careful consideration of critical wireless interference and transmission range issues. In this paper, we explore the exact throughput capacity for a class of MANETs, where we adopt group-based scheduling to schedule simultaneous link transmissions for interference avoidance and allow the transmission range of each node to be adjusted. We first determine a general throughput capacity upper bound for the concerned MANETs, which holds for any feasible packet delivery algorithm in such networks. We then prove that the upper bound we determined is just the exact throughput capacity for this class of MANETs by showing that for any traffic input rate within the throughput capacity upper bound, there exists a corresponding two-hop relay algorithm to stabilize such networks. A closed-form upper bound for packet delay is further derived under any traffic input rate within the throughput capacity. Finally, based on the network capacity result, we examine the impacts of transmission range and node density upon network capacity.

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In order to cope with the continuous evolution in cyber threats, many security products (e.g., IDS/IPS, TMS, Firewalls) are being deployed in the network of organizations, but it is not so easy to monitor and analyze the security events triggered by the security products constantly and effectively. Thus, in many cases, real-time incident analysis and response activities for each organization are assigned to an external dedicated security center. However, since the external security center deploys its security appliances to only the boundary or the single point of the network, it is very difficult to understand the entire network situation and respond to security incidents rapidly and accurately if they depend on only a single type of security information. In addition, security appliances trigger an unmanageable amount of alerts (in fact, by some estimates, several thousands of alerts are raised everyday, and about 99% of them are false positives), this situation makes it difficult for the analyst to investigate all of them and to identify which alerts are more serious and which are not. In this paper, therefore, we propose an advanced incident response methodology to overcome the limitations of the existing incident response scheme. The main idea of our methodology is to utilize polymorphic security events which can be easily obtained from the security appliances deployed in each organization, and to subject them to correlation analysis. We evaluate the proposed methodology using diverse types of real security information and the results show the effectiveness and superiority of the proposed incident response methodology.

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Amplitude phase shift keying (APSK) constellation with Gray mapping was proposed recently. Inspired by the simplified soft demapping for regular Gray-QAM, a simplified soft demapping algorithm for Gray-APSK is proposed in this paper. Compared with conventional soft demapping schemes, its complexity is greatly reduced with only a little SNR loss, which is validated by the complexity analysis and FPGA compilation results.

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Network traffic keeps increasing due to the increasing popularity of video streaming services. Routers and switches in wire-line networks require guaranteed line rates as high as 20Gbp/s as well as advanced quality of service (QoS). Hybrid SRAM and DRAM architecture previously presented with the benefit of high-speed and high-density, but it requires complex memory management. As a result, it has hardly supported large numbers of queue, which is an effective approach to satisfying the QoS requirements. This paper proposes an intelligent memory management unit (MMU) which is based on the hybrid architecture, where over 16k multi queues are integrated. The performance examined by the system board is zero-packet loss under the seamless traffic with 60-1.5kByte packet-length (deterministic manner). Noticeable feature in this paper's architecture is eliminating the need for any premium memories but only low-cost commodity SRAMs and DRAMs are used. The intelligent MMU employs the head buffer architecture, which is suitable for supporting a large numbers of FIFO queues. An experimental board based on this architecture is embedded into a Router system to evaluate the performance. Using 16k queues at 20Gbps, zero-packet loss is examined with 64-Byte to 1,500-Byte packet-length.

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To establish seamless and highly robust content distribution, we proposed the new concept of Inter-Stream Forward Error Correction (FEC), an efficient data recovery method leveraging several video streams. Our previous research showed that Inter-Stream FEC had significant recovery capability compared with the conventional FEC method under ideal modeling conditions and assumptions. In this paper, we design the Inter-Stream FEC architecture in detail with a view to practical application. The functional requirements for practical feasibility are investigated, such as simplicity and flexibility. Further, the investigation clarifies a challenging problem: the increase in processing delay created by the asynchronous arrival of packets. To solve this problem, we propose a pragmatic parity stream construction method. We implement and evaluate experimentally a prototype system with Inter-Stream FEC. The results demonstrate that the proposed system could achieve high recovery performance in our experimental environment.

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This paper proposes a device discovery method for consolidated IP and ZigBee home networks. The method broadcasts an IP multicasted device discovery request of UPnP, m-search, in the ZigBee network as a Constrained Application Protocol (CoAP) message. Upon receiving the m-search broadcast, ZigBee devices respond after a constant time delay with their device description Universal Resource Name (URN). We refer to this device discovery mechanism as transparent m-search. Transparent m-search enables reliable and swift device discovery in home networks which may include constrained networks such as ZigBee. It is revealed by an experiment with 41 ZigBee devices that the delayed response from ZigBee devices is essential to avoid collisions between m-search broadcast and responses from devices and, as a result, to secure the reliability of device discovery. Since the transparent m-search requires the receiving ZigBee devices to respond with their device description URNs, the execution time of device discovery is significantly improved. In our experiment with 41 ZigBee devices, a conventional m-search took 38.1 second to complete device discovery while that of transparent m-search took only 6.3 second.

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It is believed that the wavelength switched optical network (WSON) technology is moving towards being adopted by large-scale networks. Wavelength conversion and signal regeneration through reamplifying, reshaping, and retiming (3R) are beneficial to support the expansion of WSON. In many cases, these two functions can be technically integrated into a single shared physical component, namely the wavelength convertible 3R regenerator (WC3R). However, fully deploying such devices is infeasible due to their excessive cost. Thus, this topic serves as a motivation behind the investigation of the sparse placement issue of WC3Rs presented in this paper. A series of strategies are proposed based on knowledge of the network. Moreover, a novel adaptive routing and joint resource assignment algorithm is presented to provision the lightpaths in WSON with sparsely placed WC3Rs. Extensive simulation trials are conducted under even and uneven distribution of WC3R resource. Each strategic feature is examined for its efficiency in lowering the blocking probability. The results reveal that carefully designed sparse placement of WC3Rs can achieve performance comparable to that of full WC3R placement scenario. Furthermore, the expenditure of WC3R deployment also depends on the type of used WC3Rs characterized by the wavelength convertibility, i.e., fixed WC3R or tunable WC3R. This paper also investigates WSON from the perspective of cost and benefit by employing different types of WC3Rs in order to find the possibility of more efficient WC3R investment.

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Recently, environmental monitoring applications or home automation systems often deal with wireless sensor data. These applications deal with multi-dimensional sensing data and most processing operations involves skyline queries. In this paper, we focus on skyline queries in WSNs. However, as the number of data dimensions increases, the results of skyline queries become unmanageably large which reduces the lifetime of the sensor network. To solve these problems, we propose a novel k-dominant skyline query processing method using filtering mechanisms. The filter is designed by considering the data property and the data transmission cost. Extensive experiments show that our proposed method results in significant performance improvements over the existing method.

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This work investigates the cell range expansion (CRE) possible with time-domain multiplexing inter-cell interference coordination (TDM ICIC) in heterogeneous cellular networks (HCN). CRE is proposed to enable a user to connect to a picocell even when it is not the cell with the strongest received power. However, the users in the expanded region suffer severe interference from the macrocells. To alleviate the cross-tier interference, TDM ICIC is proposed to improve the SIR of pico users. In contrast to previous studies on CRE with TDM ICIC, which rely mostly on simulations, we give theoretical analysis results for different types of users in HCN with CRE and TDM ICIC under the Poisson Point Process (PPP) model, especially for the users in the expanded region of picocells. We analyze the outage probability and average ergodic rate based on the connect probability and statistical distance we obtain in advance. Furthermore, we analyze the optimal ratio of almost blank subframes (ABS) and bias factor of picocells in terms of the network fairness, which is useful in the parameter design of a two-tier HCN.

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In recent years, real-time streaming has become widespread as a major service on the Internet. However, real-time streaming has a strict playback deadline. Application level multicasts using multiple distribution trees, which are known as forests, are an effective approach for reducing delay and jitter. However, the failure or departure of nodes during forest-based multicast transfer can severely affect the performance of other nodes. Thus, the multimedia data quality is degraded until the distribution trees are repaired. This means that increasing the speed of recovery from isolation is very important, especially in real-time streaming services. In this paper, we propose three methods for resolving this problem. The first method is a random-based proactive method that achieves rapid recovery from isolation and gives efficient “Randomized Forwarding” via cooperation among distribution trees. Each node forwards the data it receives to child nodes in its tree, and then, the node randomly transferring it to other trees with a predetermined probability. The second method is a reactive method, which provides a reliable isolation recovery method with low overheads. In this method, an isolated node requests “Continuous Forwarding” from other nodes if it detects a problem with a parent node. Forwarding to the nearest nodes in the IP network ensures that this method is efficient. The third method is a hybrid method that combines these two methods to achieve further performance improvements. We evaluated the performances of these proposed methods using computer simulations. The simulation results demonstrated that our proposed methods delivered isolation recovery and that the hybrid method was the most suitable for real-time streaming.

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Proxy Mobile IPv6 (PMIPv6) is a network-based localized mobility management protocol that is independent of global mobility management protocols. In a single local mobility domain, the mobile node (MN) is not involved in any IP mobility-related signaling, but when the MN moves into another local mobility domain, the MN must change its PMIPv6 home address. In this case, host-based mobility signaling is activated, and PMIPv6's network-based mobility cannot be retained. Additionally, if the MN does not support global mobility, it cannot maintain its communication sessions with its correspondent node. In this paper, we propose a solution for network-based global mobility support in PMIPv6 networks, which allows the MN to maintain active communication sessions without mobility protocol stacks when the MN moves into another local mobility domain. In the proposed mechanism, the MN remains unaware of its movement when it moves to another local mobility domain, and it is forced to use only its MIPv6 home address for all its communication. Thus, the MN is not involved in any IP mobility-related signaling, despite its movement. The proposed protocol provides for global mobility while retaining the advantages of the network-based localized mobility in the Proxy Mobile IPv6 protocol. In this paper, we propose a solution for global mobility support in PMIPv6 networks by which the MAG (Mobile Access Gateway) can maintain the MN's communication sessions during inter-domain handover. In the proposed mechanism, the MN remains unaware of its movement when it moves to another local mobility domain, and it is forced to use only its MIPv6 home address for all its communication. Thus, the MN is not involved in any IP mobility-related signaling, despite its movement. We evaluate and compare network performance between our proposed solution and PMIPv6 and the main host-based mobility protocol. We evaluate and compare handover delays, and packet loss cost of the two protocols.

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Single-packet attack can be tracked with logging-based IP traceback approaches, whereas DDoS attack can be tracked with marking-based approaches. However, both approaches have their limits. Logging-based approaches incur heavy overhead for packet-digest storage as well as time overhead for both path recording and recovery. Marking-based approaches incur little traceback overhead but are unable to track single packets. Simply deploying both approaches in the same network to deal with single-packet and DDoS attacks is not an efficient solution due to the heavy traceback overhead. Recent studies suggest that hybrid approaches are more efficient as they consume less router memory to store packet digests and require fewer attack packets to recover attack paths. Thus, the hybrid single packet traceback approach is more promising in efficiently tracking both single-packet and DDoS attacks. The major challenge lies in reducing storage and time overhead while maintaining single-packet traceback capability. We present in this paper a new hybrid approach to efficiently track single-packet attacks by designing a novel path fragment encoding scheme using the orthogonality of Walsh matrix and the degree distribution characteristic of router-level topologies. Compared to HIT (Hybrid IP Traceback), which, to the best of our knowledge, is the most efficient hybrid approach for single-packet traceback, our approach has three advantages. First, it reduces the overhead by 2/3 in both storage and time for recording packet paths. Second, the time overhead for recovering packet paths is also reduced by a calculatable amount. Finally, our approach generates no more than 2/3 of the false-positive paths generated by HIT.

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Estimating the packet loss ratio of TCP transfers is essential for passively measuring Quality of Service (QoS) on the Internet traffic. However, only a few studies have been conducted on this issue. The Benko-Veres algorithm is one technique for estimating the packet loss ratio of two networks separated by a measurement point. However, this study shows that it leads to an estimation error of a few hundred percent in the particular environment where the packet loss probabilities between the two networks are asymmetrical. We propose a passive method for packet loss estimation that offers improved estimation accuracy by introducing classification conditions for the TCP retransmission timeout. An experiment shows that our proposed algorithm suppressed the maximum estimation error to less than 15%.

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Overlay networking makes it easy for users add new network functionalities while keeping existing Internet connectivity intact. This paper introduces SCONE (Service-COmposable InterNEt) as a networking service to facilitate the management of service overlay networking. By looking into the structure of programmable overlay nodes, SCONE provides programmable IP service gateways (PSGs) that ensure high-speed per-flow packet processing for overlay networking. In order to meet the data-rate requirements of various host applications, each PSG is accelerated by hardware packet processing for its data plane. It also leverages the space-efficient pattern matching of entity cloning and provides localized (i.e., de-centralized) services to assist the scalable support for software-defined networking (SDN). An experiment result shows that the proposed PSGs can support high-fidelity overlay networking from both performance and scalability perspectives.

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A new path loss model of interference between mobile terminals in a residential area is proposed. The model uses invertible formulas and considers the effects on path loss characteristics produced by paths having many corners or corners with various angles. Angular profile and height pattern measurements clarify three paths that are dominant in terms of their effect on the accurate modeling of path loss characteristics in residential areas: paths along a road, paths between houses, and over-roof propagation paths. Measurements taken in a residential area to verify the model's validity show that the model is able to predict path loss with greater accuracy than conventional models.

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Parasitic antenna elements with tunable terminations can be used for interference suppression in multi-antenna systems without using the degrees of freedom. The authors have proposed a fast non-iterative algorithm for optimizing the termination conditions. However, this method cannot be used for suppressing the interference from unknown systems since it requires the channel state information. In this paper, a fast non-iterative algorithm based on the correlation matrix, which can be obtained even from unknown interference sources, is proposed for the multi-antenna system with parasitic antenna elements. The correlation matrix including both receiving and parasitic antennas can be estimated from a few observations of the signals even without receiving signals at the parasitic antenna. By using this correlation matrix, the power of the interference with the arbitrary termination conditions can be easily estimated. Therefore, the termination condition, which minimizes the interference power, can be calculated without knowledge of the channel state information or additional estimations. The results of a numerical analysis indicate that proposed method works well in suppressing the interference without the perfect channel state information.

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In cognitive radio networks, the primary user (PU) can lease a fraction of its licensed spectrum to the secondary users (SUs) in exchange for their cooperative transmission if it has a minimum transmission rate requirement and is experiencing a bad channel condition. However, due to the selfish nature of the SUs, they may not cooperate to meet the PU's Quality of Service (QoS) requirement. On the other hand, the SUs may not exploit efficiently the benefit from cooperation if they compete with each other and collaborate with the PU independently. Therefore, when SUs belong to the same organization and can work as a group, how to stimulate them to cooperate with the PU and thus guarantee the PU's QoS requirement, and how to coordinate the usage of rewarded spectrum among these SUs after cooperation are critical challenges. In this paper, we propose a two-level bargaining framework to address the aforementioned problems. In the proposed framework, the interactions between the PU and the SUs are modeled as the upper level bargaining game while the lower level bargaining game is used to formulate the SUs' decision making process on spectrum sharing. We analyze the optimal actions of the users and derive the theoretic results for the one-PU one-SU scenario. To find the solutions for the one-PU multi-SU scenario, we put forward a revised numerical searching algorithm and prove its convergence. Finally, we demonstrate the effectiveness and efficiency of the proposed scheme through simulations.

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This paper investigates a preprocessing technique for a multiuser MIMO downlink system. An efficient joint precoder design with adaptive power allocation is proposed by adopting the channel-diagonalization technique and the minimum mean square error (MMSE) criterion. By exploiting an MMSE-based decoder, we propose an iterative algorithm to design the precoder with further derived closed-form solutions for implementing adaptive power allocation. Simulation results verify the effectiveness of our proposed approach. Compared with conventional benchmark schemes, they show that our proposal matches the performance but with reduced computational complexity.

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This paper presents an adaptive amplify-and-forward (AF)-type relay method appropriate for the cellular downlink. The proposed method adaptively selects active relay stations (RSs) based on the path loss between each set of user equipment (UE) and the base station (BS) and that between each RS in order to avoid unnecessary enhancement of inter-cell interference and bandwidth reduction due to transmission relay. Furthermore, to enhance the spectrum efficiency under relay transmission, the frequency used for the relay transmission from the RS to the cell-edge user is reused for the direct transmission from the BS to the cell-center user. Based on computer simulations, the system-level average throughput and cell-edge user throughput of the proposed method are compared to those for cases using no relaying or a conventional repeater. The simulation results show the effectiveness of the proposed method.

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Practical, low complexity time of arrival (TOA) estimation method with high accuracy are attractive in ultra wideband (UWB) ranging and localization. In this paper, a generalized maximum likelihood energy detection (GML-ED) ranging method is proposed and implemented. It offers low complexity and can be applied in various environments. An error model is first introduced for TOA accuracy evaluation, by which the optimal integration interval can be determined. Aiming to suppress the significant error created by the false alarm events, multiple pulses are utilized for accuracy promotion at the cost of extra energy consumption. For this reason, an energy efficiency model is also proposed based on the transmitted pulse number. The performance of the analytical research is evaluated and verified through practical experiments in a typical indoor environment.

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This paper focuses on learning the economic behaviour of the access point (AP) and users in wireless local area networks (WLANs), and using a game theoretic approach to analyze the interactions among them. Recent studies have shown that the AP would adopt a simple, yet optimal, fixed rate pricing strategy when the AP has an unlimited uplink bandwidth to the Internet and the channel capacity of WLAN is unlimited. However, the fixed rate strategy fails to be optimal if a more realistic model with limited capacity is considered. A substitute pricing scheme for access service provisioning is hence proposed. In particular, the AP first estimates the probable utility degradation of existing users consequent upon the admission of an incoming user. Second, the AP decides: (i) whether the incoming user should be accepted; and (ii) the price to be announced in order to try to maximize the overall revenue. The condition, under which the proposed scheme results in a perfect Bayesian equilibrium (PBE), is investigated.

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This paper investigates the transmission capacity of open-loop spatial multiplexing with zero-forcing receivers in overlaid ad hoc networks. We first derive asymptotic closed-form expressions for the transmission capacity of two coexisting networks (a primary network vs. a secondary network). We then address a special case with equal numbers of transmit and receive antennas through exact analysis. Numerical results validate the accuracy of our expressions. Our findings show that the overall transmission capacity of coexisting networks will improve significantly over that of a single network if the primary network can tolerate a slight outage probability increase. This improvement can be further boosted if more streams are configured in the spatial multiplexing scheme; less improvement is achieved by placing more antennas at the receive side than the transmit side. However, when the stream number exceeds a certain limit, spatial multiplexing will produce negative effect for the overlaid network.

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The optimization of polarimetric contract enhancement (OPCE) is one of the important problems in radar polarimetry since it provides a substantial benefit for target enhancement. Considering different scattering mechanisms between the desired targets and the undesired targets, Yang et al. extended the OPCE model to the generalized OPCE (GOPCE) problem. Based on a modified GOPCE model and the linear discriminant analysis, a ship detector is proposed in this paper to improve the detection performance for polarimetric Synthetic Aperture Radar (SAR) imagery. In the proposed method, we modify the combination form of the three polarimetric parameters (i.e., the plane scattering similarity parameter, the diplane scattering similarity parameter and the Cloude entropy), then use an optimization function resembling the classical Fisher criterion to optimize the optimal polarization states corresponding to the radar received power and the fusion vector corresponding to the polarimetric parameters. The principle of the optimization detailed in this paper lies in maximizing the difference between the desired targets and sea clutter, and minimizing the clutter variance at the same time. RADARSAT-2 polarimetric SAR data acquired over Tanggu Port (Tianjin, China) on June 23, 2011 are used for validation. The experimental results show that the proposed method improves the contrast of the targets and sea clutter and meanwhile reduces the clutter variance. In comparison to another GOPCE based ship detector and the classical polarimetric whitening filter (PWF), the proposed method shows a better performance for weak targets. In addition, we also use the RADARSAT-2 data acquired over San-Francisco on April 9, 2008 to further demonstrate the improvement of this method for target contrast.

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Ultra-wideband pulse radar is a promising technology for the imaging sensors of rescue robots operating in disaster scenarios, where optical sensors are not applicable because of thick smog or high-density gas. For the above application, while one promising ultra-wideband radar imaging algorithm for a target with arbitrary motion has already been proposed with a compact observation model, it is based on an ellipsoidal approximation of the target boundary, and is difficult to apply to complex target shapes. To tackle the above problem, this paper proposes a non-parametric and robust imaging algorithm for a target with arbitrary motion including rotation and translation being observed by multi-static radar, which is based on the matching of target boundary points obtained by the range points migration (RPM) algorithm extended to the multi-static radar model. To enhance the imaging accuracy in situations having lower signal-to-noise ratios, the proposed method also adopts an integration scheme for the obtained range points, the antenna location part of which is correctly compensated for the estimated target motion. Results from numerical simulations show that the proposed method accurately extracts the surface of a moving target, and estimates the motion of the target, without any target or motion model.

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In this paper, we propose a novel scheme for efficient video broadcasting over WLANs using the IEEE 802.11e HCCA MAC and H.264/SVC. We rearrange the outgoing sequence of H.264/SVC NAL units according to their dimension, temporal, and quality scalability. In addition, our proposed scheme broadcasts the NAL units at various data-rates by using the link adaptation function of IEEE 802.11 PHY. Our scheme is verified using NCTUns network simulator, and is evaluated in terms of throughput, delay, and quality of experience (QoE) using structural similarity (SSIM) rather than mean square error (MSE). We employee a real video clip to increase the reliability of the simulation in which the video clip is compressed as VBR with 24 scalable layers by JSVM reference codec of the H.264/SVC. In the simulation topology, a host broadcasts the video clip to 10 wireless stations which are within 150 meters from an AP. We present performance comparisons between our proposed scheme and the scheme provided by the IEEE 802.11e HCCA standard, which is to be referred to as the simple scheme in this paper. The proposed scheme noticeably enhances in the three performance metrics. All wireless stations by the proposed scheme receive more video data than the simple scheme around 25∼30% within a delay bound of 1 second. The proposed scheme controls the end-to-end delay to 5∼10% under that of the simple scheme. As for the throughput and the delay performance, the proposed scheme enhances the video quality by up to 6∼7% compared to the simple scheme in SSIM evaluation.

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Multi-view video consists of multiple video sequences which are captured by multiple closely spaced cameras from different angles and positions. It enables each user to freely switch viewpoints by playing different video sequences. However, the transmission of multi-view video requires more bandwidth than conventional multimedia. To reduce the bandwidth, UDMVT (User Dependent Multi-view Video Transmission) based on MVC (Multi-view Video Coding) for a single user has been proposed. In UDMVT, the same frames are encoded into different versions for different users, which increases the redundant transmission. To overcome this problem and extend UDMVT to multiple users' environment, this paper proposes UMSM (User dependent Multi-view video Streaming for Multi-users). UMSM calculates the overlapping and un-overlapping frame area for multiple users from all frames based on feedback information at a server. Proposed UMSM exploits the combination of multicasting overlapping area to multiple users and unicasting un-overlapping area to each user. By means of this concept, UMSM only transmits required frames for each user. To achieve further reduction of the traffic, UMSM combines other two features with this concept. The first one is that offset of the requests from multiple users is aligned periodically to maximize the overlapping frame area. The second one is that the SP-frames standardized in H.264/AVC are exploited as the anchor frame of overlapping frame area to prevent redundant transmissions of overlapping frames. The combination of these three techniques achieves substantial reduction of the transmission bitrate for multiple users in multi-view video streaming. Simulation results using benchmark test sequences provided by MERL show that UMSM decreases the transmission bit-rate 47.2% on average for 4 users are watching the same multi-view video compared to UDMVT.

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