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The development of information technology has brought changes in industrial technology. Traditional industry is declining and intelligent industry is rising. Compared with the traditional industry, intelligent industry has a stronger demand for computing resources and is more sensitive to delay. To meet these requirements, this paper designs a computing platform integrating edge and cloud resources. The platform is mainly composed of edge computing nodes, cloud system, and AI(Artificial Intelligence) component. Edge computing nodes provide network services and computing offload services, which can quickly respond to industrial tasks. Cloud system provides computing resources and storage services for high resource consumption tasks in industry. AI components make full use of idle resources in the edge network to form clusters to accelerate AI inference. Facing different industrial scenarios, the platform can flexibly allocate computing resources in the network and provide computing offload service for tasks in the industry. Finally, we designed three experimental scenarios to verify the effectiveness of our platform. In the three experimental scenarios, compared with the traditional task execution method, our platform has brought obvious productivity improvement and accelerated the completion speed of the task.

Cloud computing has been widely used in the field of information services. However, large-scale Internet of things (IoT) applications are raising new challenges to cloud computing architecture. Edge computing, which complements cloud computing, is considered to be the way to address these challenges. Volunteer computing, which harvests idle resources in the network can improve the hardware utilization rate and support tens of billions of IoT devices. In view of the limitations of traditional volunteer computing that cannot provide realtime services and has no mechanism to reward services in existing volunteer clouds, this paper presents blockchain-based volunteer edge cloud. A common runtime environment is provided by container technology, and blockchain smart contract is used for critical business steps and computing service payment. Volunteer edge cloud systems based on blockchain is introduced from a top-level perspective, and a prototype system build on Ethereum and KubeEdge is described in detail. On top of the prototype system, we deployed an example IoT application of robot formation control. It demonstrates the benefits of volunteer edge cloud in reducing the complexity of IoT devices, improving the flexibility of software development, and paying the computing service.

Fog computing shows great potential advantages over legacy cloud computing in terms of latency and efficiency. While it also poses huge challenges in task scheduling and resource allocation, which are key to reap the full benefits of fog computing. Facing the new characteristics of fog computing, distributed task scheduling and resource allocation algorithms are necessary but challenging, which will be investigated in this paper. To minimize the latency in a distributed manner, a many-to-one matching game with externalities is formulated for task scheduling problems in fog networks, considering the inter-dependency among tasks in both communication and computation. Further, a distributed algorithm called Distributed Two-sided Stable Task Scheduling (DTS2) algorithm is proposed to find a two-sided exchange-stable solution. Analytical and simulation results show that the proposed DTS2 algorithm can converge to a sub-optimal two-sided exchange-stable solution with low-complexity. Specifically, the DTS2 algorithm can greatly reduce the service delay than the one-sided stable matching. Besides, it can offer sub-optimal performance in system average delay but serve more users, compared with the optimal solution.

Fog computing has been promoted to support delay-sensitive applications in future Internet of Things (IoT) and wireless networks. For a general heterogeneous fog network consisting of many dispersive Fog Nodes (FNs) with diverse resources and capabilities, some of them have delay-sensitive tasks to process, i.e., Task Nodes (TNs), while some have spare resources to help their neighboring TNs to process tasks, i.e., Helper Nodes (HNs). How to effectively map multiple tasks or TNs into multiple HNs to minimize every task's service delay in a distributed manner is a fundamental challenge, which is key to reap the full benefits of fog computing. The problem becomes more challenging when tasks can be divided into multiple subtasks to further reduce the service delay via distributed computing. To tackle this challenge, in this paper, a generalized nash equilibrium (NE) game called Parallel Scheduling of Multiple Tasks (PSMT) is formulated and studied. The structure properties of the problem are deduced and thus the existence of NE is proven by the fixed point theorem. Further, the corresponding distributed task scheduling algorithm/mechanism is developed via Gauss-Seidel-type method. Simulation results show that the proposed PSMT algorithm can converge in a fast way and offer much better performance in system average delay and number of beneficial TNs, comparing to the Paired Offloading of Multiple Tasks (POMT) solution to the counterpart problem not supporting distributed computing.

Fog computing is a promising paradigm to perform low-latency computation for supporting the internet of things (IoT) applications. It enables provisioning resources and services to be closer for end users. Limited by the computing and storage resources, end users offload the computation-intensive tasks to the nearby fog nodes. However, due to mobility feature of the fog nodes, it's challenging to realize efficient task offloading. We rigorously formulate the task offloading problem for dynamic fog networks as an online stochastic optimization problem, and design offloading policies when the network is in stationary status and non-stationary status. When the fog network is in stationary status, we propose task offloading for the stationary status (TOS) algorithm to minimize the long-term average offloading delay. When the fog network is in non-stationary status, we propose two algorithms as task offloading for the non-stationary status using a sliding window (TON-SW) and task offloading for non-stationary status using a discount factor (TON-D) to minimize the average offloading delay. Besides, learning regret bounds of our algorithms are given. Numerical simulations show that our algorithms achieve a significant performance improvement compared to the upper-confidence bound (UCB) algorithm.

In this paper, a comprehensive analytical model that considers circuit, computation, offloading energy consumptions is developed for accurately evaluating the overall energy efficiency in homogeneous fog networks. With this model, the tradeoff between performance gains and energy costs in collaborative task offloading is investigated, thus enabling us to formulate the energy efficiency optimization problem for future intelligent internet of things (IoT) applications with practical constraints in available computing resources at helper nodes and unused spectrum in neighboring environments. Based on rigorous mathematical analysis, a maximal energy efficient task scheduling (MEETS) algorithm is proposed to derive the optimal scheduling decision for a task node and multiple neighboring helper nodes under feasible modulation schemes and time allocations. Extensive simulation results demonstrate the tradeoff relationship between energy efficiency and task scheduling performance in homogeneous fog networks. Compared with traditional strategies, the proposed MEETS algorithm can achieve much better energy efficiency performance under different network parameters and service conditions.

In this paper, we revisit the idea of using deep neural network for channel equalization to account for nonlinear channel distortions as well as temporal variations of radio signals. Our insight is leveraging the the shift-invariant properties of the convolutional neural network (CNN) to learn matched filters analogous to the tap weights of conventional equalizer. Then we feed the learned filters into a subsequent recurrent neural network (RNN) with long-short-term-memory (LSTM) cells for temporal modeling of the channel. We train our proposed CNN-RNN (CRNN) equalizer based on real testbed collected data and enlarge the generalization ability of the learned network model as much as we can to adapt to different channel conditions. Experimental results show that the SER performance for our designated single-input single-output (SISO) system which utilises quadrature phase shift keying (QPSK) modulation scheme with the proposed CRNN-based channel equalizer outperforms that of other equalizers by average 2 to 5 dB at low signal-to-noise ratio (SNR).

Fog computing is regarded as a promising architecture to support various services on demand. Hand-held devices (or fog nodes) are becoming more and more powerful and can help each other to communicate and compute. In particular, the proximity-based communication through the device-to-device (D2D) links is one important paradigm of fog computing. In this paper, we look into the time reuse problem in a fog-enabled cooperative network. Even though the number of possible time reuse patterns increases exponentially with the quantity of the devices, we first show that the optimal network performance can be achieved by only activating a limited number of reuse patterns. Furthermore, when limited to a specific set of time reuse patterns, the optimal allocation problem becomes a biconvex one. Based on the alternate convex search (ACS) method and the alternating-direction method of multipliers (ADMM), a semi-distributed algorithm of low complexity, namely alternate distributed allocation of time reuse patterns (ADARP), is proposed to identify the optimal time reuse profile and the corresponding optimal association strategies. This semi-distributed nature renders our proposed solution suitable for fog-enabled cooperative D2D networks. Numerical simulations are carried out to corroborate our designs.

In next generation cellular networks, small cell base stations (BSs) with ultra-dense deployments are likely to cooperate together to manage interference and provide users with high data rates. But users may still experience large drops in throughput due to lack of available resources even with high received signal strength. In this paper, we propose a congestion-aware user-centric cooperative BS selection method in ultra-dense networks. Each user chooses its cooperative BSs based on not only the received signal-to-interference-pulse-noise ratio (SINR), but also the predicted load of BS, which is called congestion metric. The congestion metric is calculated by each BS according to the current load of BS and the predicted load brought by the users who are ready to access the BS. In order to maximize the objective function which considers both received SINR and congestion metric, we propose two suboptimal greedy algorithms which have much lower computational complexity than exhaustive search procedure. Simulation results show that the user average data rate and system spectral efficiency of proposed congestion-aware schemes are much higher than that of the SINR-based user-centric clustering scheme. It is also shown that the greedy algorithms perform closely to exhaustive search procedure, while having much lower computational complexity.

It is necessary to optimize the energy-efficient (EE) performance for millimeter-wave (mmWave) wireless systems, since the power consumption problem becomes increasingly crucial at high frequency bands. In hybrid precoding mmWave systems, the EE-oriented optimized elements include the analog and digital precoders at the transmitter, the analog and digital combiners at the receiver, as well as the corresponding number of opened radio frequency (RF) chains. In contrary to calculate the optimal precoding/combining matrices exhaustively for all possible numbers of RF chains as in the existing works, this paper proposes a two-stage alternative method with nearly optimal sum rate performance and much lower computation complexity. It firstly calculates the optimal number of opened RF chains, and then the nearly optimal precoder and combiner are directly obtained within only one round calculation. The complicated calculations of all the elements in optimization are decoupled by exploring the asymptotical property of the mmWave system with large antenna arrays, as well as the sparsity characteristic of the mmWave fading channel. Simulation results are further provided to verify the validation of the proposed method.

Time synchronization is one of the key technologies in Industrial Wireless Sensor Networks (IWSNs). Considering the demand of low energy consumption, fast convergence and robustness for IWSNs, this paper presents a novel Cluster-based Maximum consensus Time Synchronization method. Based on the theory of distributed consensus, the method utilizes the maximum consensus approach to realize the intra- cluster time synchronization. In the inter-cluster time synchronization, adjacent clusters exchange the time messages via overlapping nodes to synchronize with each other. In addition, the clustering technique is incorporated in the method, which can effectively reduce the redundant data. And the hops can be controlled, which improves the energy efficiency and convergence rate very well. At last, the simulation results show that our method reduces the communication overhead and improves the convergence rate in comparison to existing works.

Cooperative spectrum sensing (CSS) achieves spatial diversity and is used to combat shadowing and fading in sensing. In reality, spectrum sensing in TV band may also face challenges caused by interference from secondary users (SU). Unfortunately, this issue has not yet been sufficiently discussed. In this work, we propose a CSS to mitigate impact of SU interference and maintain robust sensing. After discussing the reality that spectrum sensing in TV band could suffer SU interference, we describe a sensing scenario that truly exists. Under the scenario, sensing is conducted by IEEE 802.22 standard compliant devices for detecting TV signal in an area with some other heterogeneous SU networks, such as IEEE 802.11af network, operating in nearby. The proposed CSS is conducted by selected sensors and detects instant power change between two consecutive sensing durations. Computer simulation is conducted to verify novelty of the proposed CSS in mitigating impact of noise uncertainty and SU interference.

This paper presents the performance and coexistence analysis of multiple IEEE 802 wireless communication systems operating in TV White Space (TVWS). Three IEEE 802 groups with systems operating in TVWS, namely IEEE 802.15.4m Low-Rate Wireless Personal Area Network (LR-WPAN), IEEE 802.11af Wireless Local Area Network (WLAN) and IEEE 802.22 Wireless Regional Area Network (WRAN) are investigated. First, system performance and achievable operating range for these systems in the absence of interference are evaluated, in accordance to design parameters suited to targeted application scenarios respectively. Then, assuming operation in close proximity, the three systems in the presence of interference are investigated to assess their error performance and critical distances to interfering device. The results highlighted several insightful critical parameter settings such as interferer-to-victim separation and interferer transmit power, beyond or below which, cause intolerable degradation to victim systems as quantified by the minimum required error rate performance.

This paper presents the network performance analysis of a low energy IEEE 802.15.4/4e/4m LR-WPAN operating in TV White Space. An energy-efficient mechanism optimizing the tradeoff between device sleep time and synchronization strategy is utilized to reduce the total power consumption in a non-beacon-enabled network. To evaluate the performance of the network, we have modeled a cross-layer system starting from the application, transport, network layers, to the MAC layer where the energy-efficient mechanism resides, to the PHY layer where the FSK PHY resides, down to the propagation channel where the VHF/UHF channels applies. Extensive computer simulations were conducted to investigate the performance of this low energy LR-WPAN system. As a result, we have found that a device may consume up to 40% and 2% of its total operation time to perform channel scanning and transmission, respectively. Applying the proposed energy-efficient mechanism, the achievable reduction of channel scanning time and transmission time are 20% and 1% respectively. We have also observed that the average residual battery capacity can be most effectively preserved when the number of devices in the network reaches approximately 30.

This paper reports measurements and characterizations of broadband indoor Television White Space (TVWS) channel with center frequency of 670 MHz. The measurements have been carried out in small- and medium-size mixed office and lab indoor environments recently. Channel multipath delay spread of both line-of-sight (LOS) and non-LOS (NLOS) connections are identified by using BPSK signaling of 20-Mbps data rate. The root-mean-square (RMS) delay spreads are found between 20 ns to 32 ns for LOS and 32 ns to 41 ns for NLOS in small-size office and lab environment, and is found about 38 ns for LOS and 39 ns for NLOS in medium-size indoor environment. A general complex low-pass impulse response model is proposed based on our findings and the classic Saleh-Valenzuela (S-V) channel model. With the proposed channel impulse response model, ray clusters may appear before and after the strongest cluster and rays may exist on both sides of the strongest ray in a cluster. Model parameters are extracted from the measurement results. Extensive simulation results show that the model fits the measurements well.

This paper provides an overview on motivations and process behind the forming of the first low rate (LR) wireless personal area networks (WPAN) operating in the TV white space (TVWS), IEEE 802.15.4m. There are three main forces driving the LR-WPAN community to expand its operational band to the TVWS. First, the change in TVWS-related regulations that opens up new spectrum resources is the key triggering factor. Secondly, there are many potential applications addressed by LR-WPAN systems that are anticipated to benefit from the expansion of the spectrum. Thirdly, the emergence of multiple standardizations targeting on the same types of applications in the same conventional frequency bands, indicating potential congestion and heterogeneous coexistence issues, is also one of the main pushing factor. In this paper, a comprehensive summary of different regulations, list of potential usage models and interactions among conventional LR-WPAN system are presented. A general discussion on how these factors fall in place to realize the forming of IEEE 802.15.4m is given. Finally, the paper concludes with expected functional requirements for the IEEE 802.15.4m system.

This paper presents research status on public broadband wireless communication (PBB) system. The PBB system uses VHF band between 170 MHz and 205 MHz that is available after termination of analogue TV broadcasting service on July 24, 2011. This paper summarizes the transition of television service from analogue to digital and fundamental specification on spectrum usage, physical and MAC layers.

Recently, various wireless networks are emerging and it leads to spectrum congestions. Cognitive radio, which allows users of the emerging wireless networks to opportunistically utilize the unused bands of the existing primary systems, can alleviate this problem. As one of the emerging wireless networks, 802.16 networks are suggested to explore TV “White Space” and then it is necessary to study cognitive operations of this network. In this paper, we propose enhanced frame structure and new channel accessing algorithms to enable cognitive operation of the WiMAX Mesh networks. With the novel algorithms for dynamically accessing the frequency channels for the control messages transmissions, no extra common control channels and operations of mesh clusters are needed, thus the spectrum resource can be saved and the network operation becomes simpler. The performance of the algorithms and the MAC protocol are analyzed theoretically and evaluated numerically. Results show that our algorithms can achieve, e.g., 3 times gain, in getting control messages received by neighbors, when compared to the scheme of mesh clusters. It also shows that with the parameter values presented, the normalized saturation throughput can be, e.g., as high as 75%.

There is a lack of high-speed and low-cost wireless network at sea to meet the increasing need of maritime users. With this observation, we have envisaged a WiMAX mesh network for high-speed ship- to-ship/shore communications. Analysis of interference range in such maritime WiMAX mesh networks is presented in this paper. And based on the findings, scheduling transmission of MAC control messages and data packets within three-hop neighborhood is investigated for the purpose of minimizing interference. A model is developed for analysis of the interference range in maritime environment. With parameter values that are derived from measurements at sea, we show that by scheduling among three-hop neighborhood the probability a transmission being interfered by a concurrent transmission drops about 30%. Simulation results show that, with the simulation settings in this paper, by scheduling among three-hop neighborhood, the initial packet delay and the average packet delay can be reduced by about 17% and 15.6% in sea state 3.0, respectively. In sea state 6.0, the performance improvement in initial packet delay and average packet delay are about 45% and 19.3%, respectively.

Wireless mesh ad hoc network is envisaged by us recently for maritime communications because of the lack of high-speed and low-cost communication systems in sea. A maritime simulator is developed for the purpose to simulate the sea environment and evaluate designs and protocols used in maritime mesh networks. In maritime simulator, modeling direction of arrival (DoA) of radio signal is critical since it determines antenna gain and received radio signal power at a receiver. In this paper, we propose an analysis model of DoA in maritime environment based on modeling sea wave movement as Trochoid wave and analyzing orientations of ships in various sea states. Simulations have been carried out and the results match very well with measured. The model can be used in simulation of wireless ship-to-ship/shore communications, and in finding maximum loss of antenna gain due to sea wave movement, which needs being considered in link budget when do network planning.

We envisage extending the coverage of existing terrestrial wireless broadband wireless networks to the sea so that cost-efficient wireless access is available to the ships near the shore. The coverage extension is achieved through a multi-hop WiMAX wireless mesh networks where ships, maritime beacons and buoys are the nodes. In such a multi-hop network, routing protocol plays an important role in ensuring reliable end-to-end packet delivery. Compared to AOMDV and OLSR, AODV has been found as a more suitable routing protocol in terms of average packet delay, packet delivery ratio, and implementation complexity. AODV requires route request messages being broadcast during route discovery process. However, WiMAX mesh MAC protocol is not efficient in supporting broadcast of data packets that carry the route request. This inefficiency is due to need of performing the three-way-handshaking process in reserving a data slot before transmitting each route request. As a result, AODV suffers from large initial packet delay and average packet delay. In view of the problem, this paper proposes a method to efficiently deliver the AODV routing messages by piggybacking them on the existing WiMAX mesh MAC control messages. As such, the three-way-handshaking is avoided leading to a faster transmission of routing messages. Simulation results confirm that the proposed scheme can lead to an improvement in initial packet delay, weighted average delay, and packet delivery ratio.

We envisage extending radio coverage of the existing terrestrial wireless broadband networks to the sea to provide ships with cost-efficient high-speed connection to the Internet. This is achieved by forming a WiMAX based maritime wireless mesh network where ships are network nodes connected to the land station across multiple hops. In such a maritime wireless mesh network, time slot allocation is an important issue as it affects the performance in terms of throughout and delay. This papers proposes a distributed adaptive time slot allocation (DATSA) scheme for WiMAX mesh MAC protocol. DATSA is a distributed scheme that allocates time slots robustly by taking into consideration difference between radio reception range and interference range, and latency in scheduling control messages. DATSA has a method to monitor reception quality of an allocated time slot, in order to detect the effect of topology changes due to ship mobility, etc. Based on the monitoring outcome, the method adaptively changes the time slot allocation if necessary. We have evaluated DATSA through random event simulation using QualNet. The simulation results confirm that DATSA outperforms the original WiMAX mesh MAC protocol that has no adaptive time slot allocation, in terms of throughput, average packet delay, and packet delivery ratio.

We envisage extending radio coverage of the existing terrestrial wireless broadband networks to the sea to provide ships with high speed connection to the Internet. This is achieved by forming a WiMAX-based maritime wireless mesh network where ships are network nodes connected to the land station across multiple hops. In such a wireless mesh network, routing protocol plays an important role in providing efficient and reliable communications. This paper proposes a routing protocol, called MRPT (MAC-based Routing Protocol for TRITON), that piggybacks routing information on WiMAX mesh MAC control messages. This provides proactiveness and readily available multi-path for traffic from ship to land station. For traffic from land station to ship, the proposed routing protocol uses a bitmap encoding to efficiently inform land station of the constructed routing tree. Simulation results confirm that MRPT outperforms AODV, AOMDV and OLSR in terms of delay and throughput.

Existing communications from ships via satellites are expensive. We are motivated to extend the cheaper terrestrial communication coverage to sea via multi-hop networking. Maritime environment presents new challenges because sea surface moves randomly resulting in wave occlusion that breaks communication links. This paper models the maritime communication link after considering the wave occlusion and propagation impairments. Based on characteristics of the link, this paper proposes an aggregated-path routing approach that forms a route connecting virtual nodes, where each virtual node is a collection of nodes that are within the radio range of all nodes in its previous virtual node. Simulation and analytical results confirm that aggregated-path routing is significantly better than traditional single-path routing in terms of efficiency.

WiMAX Mesh networking is of many advantages for intelligent transportation systems (ITS) applications. In long-hop-distance ITS networks, multi-channel transmission may alleviate problem of insufficiency of bandwidth when a network uses single frequency channel. This paper presents algorithm of multi-channel bandwidth allocation in WiMAX mesh networks. Simulation is carried out with a maritime simulator, by which performance of multi-channel WiMAX mesh transmission is evaluated for high-speed ship-to-ship/shore communications in sea. Simulated results show that with multi-channel operations, in terms of packet delivery ratio and average end-to-end delay, the network performance is improved, in both sea state 3.0 and 6.0. In more rough sea and with more heavy traffic load, the improvement is observed clearer.

The 60-GHz band wireless link using microwave photonics technologies for gigabit wireless applications is presented. The microwave photonic frequency upconverter utilizing the fiber-optic wavelength conversion is adopted as a method for the wireless downlink and the seamless integration of wired and wireless networks. The proposed system shows the spurious-free dynamic range of 81.2 dBmiddotHz2/3. The optically generated carrier at 62.75 GHz has the phase noise of -73.8 dBc/Hz at a 10-kHz offset. The system performance is optimized by controlling optical parameters for error-free transmission. Error-free transmission of the 1.25-Gb/s data carried in 62.75 GHz is achieved for 20-km fiber transmission between the central station and the remote base stations (BSs) including 1-m aerial transmission between the BSs and the customer unit using horn antennas.

This paper details a novel approach of developing a low-cost and high speed maritime ship-to-ship/shore mesh network to complement or replace satellite communications in narrow water channels or traffic lanes close to shorelines. To design the system, we gathered requirements from typical users of the system. We then carried out preliminary studies such as radio channel propagation over sea water, ship movement patterns, ship rocking and its effect on radio transmission and network connectivity to determine the feasibility of using a mesh network for maritime networks. We present the architecture and detail some of our routing and scheduling design considerations that address the unique challenges of the maritime environment and provide us with framework for providing fair and equal opportunity access to users.

We envisage coverage extension of the high bit rate terrestrial communication networks to the ships to reduce the cost in maritime communications. The coverage extension is achieved by forming a mobile wireless mesh network amongst neighboring ships, marine beacons and buoys. The wireless mesh network will be connected to the terrestrial networks across multiple hops via land stations at shore. In such a multi-hop wireless network, routing protocol is important. This paper compares the performance of three existing routing protocols in a maritime communication environment. The three routing protocols are OLSR, AODV and AOMDV. The performance comparison is done via simulation. In the simulation, the wireless mesh network is formed using WiMAX mesh MAC protocol. Also, the random sea surface movement and maritime communication link characteristic are simulated. From the simulation results, we found that OLSR is not as efficient as AODV and AOMDV. Also, compared to AODV, the performance of AOMDV is less affected by sea condition.

An IEEE 802.16 MESH network is envisaged for multihop inter-ship communications and its MAC performance is investigated by simulations. Results show that, with respect to throughput, delivery ratio, and average delay, when sea wave direction is perpendicular to the nodes connection direction, good MESH MAC performance can be achieved in sea states 1.0, 3.0, 5.0, and 7.0, for both 1-hop and 2-hop CBR connections with hop distance more than 10 km. With relative parallel wave direction, in sea states 1.0 and 3.0, the MAC performance is close to that of the perpendicular case while it drops in sea state 5.0 and 7.0; however the delivery ratio can still be more than 60 percent. With increase in 1-hop CBR data flows, the network throughput increases linearly in sea state 1.0; but the increase in throughput becomes slower in higher sea states.

As a fundamental component in wireless networks, location management consists of two operations: location update and paging. These two supplementary operations enable the mobile user ubiquitous mobility. However, in case of failed location update, a significant consequence is the obsolete location identity in the network databases and thereafter the incapability in establishing the valid route for the potential call connection, which will seriously degrade the network quality-of-service (QoS). This issue is not theoretically studied in the literature. In this paper, we perform a quantitative analysis of the location management effect on QoS in the wireless networks. The metrics call blocking probability and the average number of blocked calls are introduced to reflect the QoS. For the sake of general applicability, the performance metrics are formulated with the relaxed tele-traffic parameters. Namely, the call inter-arrival time, cell residence time, location area residence time and location update inter-arrival time follow a general probability density function. The formulae are additionally specified in the static and several dynamic location management mechanisms. Numerical examples are presented to show the interaction between the performance metrics and location management schemes. The discussions on the sensitivity of tele-parameters are also given.

A novel cost-effective technique is proposed to enhance the optical modulation depth of the fiber downlink and simultaneously recover the downlink optical carrier in an antenna base station in a millimeter-wave fiber-wireless system. With the proposed structure, the downlink optical modulation depth is enhanced with the help of a low-cost 2times2 all-fiber optical interleaver so that the optical receiver sensitivity is improved, and the recovered optical carrier can be reused for fiber uplink transmission to simplify the upstream optical interface. The effectiveness of the proposed scheme is demonstrated by experiment

RF power degradation introduced by optical polarization mismatch in dual-wavelength millimeter-wave fiber-radio systems is analyzed and presented. We show that, when effect of polarization-mode dispersion (PMD) can be ignored, both mismatch of polarization projects and polarization phase delays may influence the power of the generated millimeter-wave signal. When effect of polarization-mode dispersion is counted, the power degradation due to PMD can be aggravated or alleviated by polarization mismatch between the two optical wavelengths. All the above effects are numerically illustrated in the paper

Due to the inherent flexibility, scalability and reliability advantages of mesh networking architecture, the IEEE 802.16 working group is actively standardizing the mesh mode for the mobility scenarios. Comparing with the point-to-multipoint (PMP) mode providing Quality-of-service (QoS) mechanisms, the newly introduced mesh mode has not specified solutions for the mesh mode. In this paper, we propose and analyze an effective scheme achieving QoS in the WiMAX mesh networking mode for the Maritime ITS applications. Illustrative numerical examples are presented to indicate the effectiveness of the proposed strategy, and also the impact of key parameters in differentiating the diverse requirements.

A low cost radio-over-fiber (ROF) transmitter has been built based on extremely low cost 850 nm vertical-cavity surface-emitting laser (VCSEL) diode using spherical-ended multimode fiber (MMF) coupling technique. This technique has been shown to deliver excellent light launching characteristics for VCSEL lasers in short haul ROF applications. Transmission distance of more than 600 m has been demonstrated experimentally with consistent performance highly desired for transmitting WLAN RF signals in both 2.45 and 5.25 GHz in a directly modulated MMF VCSEL short haul ROF link. Various coupling methods and the bonding process of mating the VCSEL to MM fiber have been investigated to optimize the optical power coupling for cost reduction and low complexity. The results show that the transmitter coupled by spherical-ended MMF provides 30% more optical coupling efficiency and enhanced noise figure performance than the lens-less flat cleaved alternative

In this paper, a simple and effective coplanar structure has been adopted to suppress harmonics in microstrip antenna element and array based on quarter wavelength microstrip step impedance resonators (SIR). This circuit is more compact than the previous coplanar harmonic rejection structure and can be restrained within one-twelfth wavelength region near to the antenna. It is a valuable technology for antenna design in the future RF front-end system-in-package (SIP).

There are two major contributions in this paper. The first is to exam the Poisson assumption for the authentication traffic process triggered by the location update (LU) requests. For this, we develop an analytical model and efficient, recursive algorithm to derive the LU inter-arrival time in static as well as dynamic location management scheme. The analysis is validated by simulation and the numerical investigation indicates that the Poisson process is invalid in approximating the authentication requests. The second goal is to investigate the issue: whether different mobility management schemes have a significant effect on the authentication traffic evaluation. To answer this, we propose a system model to incorporate different LU policies. Via simulation, we evaluate the authentication traffics under static and dynamic location management schemes. The comparison demonstrates that, due to the diverse network architecture as well as the different event triggering LU message, there are significant discrepancy in generating authentication traffic load. The result reveals the fact that the performance of security management and the mobility management in wireless mobile networks interact with each other.

Traditionally, the wireless networks tele-traffic modeling is performed without taking into account the physical link inherent unreliability. In order to reflect the unique characteristics of the channel erroneous property, we introduce the concept resource occupancy time (ROT) and derive its property in terms of probability density function and statistical moments under the general scenarios, i.e. general call holding time and the generalized wireless channel model. Numerical investigation is carried out to discuss the impacts of the call holding time and the wireless channel characteristics upon ROT.

With standard fiber and conventional optical double-sideband modulations, the fiber transmission distances of millimeter-wave signals are severely limited under several kilometers due to dispersion-induced signal fading. This limitation could be minimized by employing optical single-sideband (OSSB) modulation. This paper presents experiment of optical single-sideband modulation at 60 GHz, using two individual electro-absorption modulators in parallel. Stabilizing the achieved OSSB spectrum is also discussed.