Wireless Access Services Research Articles

Joint Link Scheduling and Brightness Control for Greening VLC-Based Indoor Access Networks

Demands for broadband wireless access services are expected to outstrip the capacity in the near-term spectrum crunch. Deploying additional femtocells to address this challenge is cost-inefficient due to the backhaul challenge and the exorbitant system maintenance. According to an Alcatel-Lucent report, most mobile Internet access traffic happens indoors. Leveraging power line communication and the available indoor infrastructure, visible light communication (VLC) can be utilized with a small one-time cost. VLC also facilitates the great advantage of being able to jointly perform illumination and communications, and little extra power beyond illumination is required to empower communications, thus rendering wireless access with small power consumption. In this study, we investigate the problem of minimizing total power consumption of a general multiuser VLC indoor network while satisfying users' traffic demands and maintaining an acceptable level of illumination. We utilize the column-generation method to obtain an e-bounded solution. Several practical implementation issues are integrated with the proposed algorithm, including different configurations of light source and ways of resolving the interference among VLC links. Through extensive simulations, we show that our approach reduces the power consumption of the state-of-the-art VLC-based scheduling algorithms by more than 60% while maintaining the required illumination.

무선 네트워크에서 자연계 동기화 현상을 모방한 자율적 부하 균형 기법

Inspired by the synchronization phenomena observed in the Nature, we propose an autonomous load balancing method for a wireless network. We model the load balancing problem of cells providing wireless access services as a synchronization problem in the Nature and design an algorithm for each cell to distribute loads in a self-determining way based on the load differences among its neighbor cells. Through simulations, we verify the feasibility of the proposed method in that cell loads can be balanced efficiently eve if cells make decision autonomously using their local information.

Cooperative weighted-fair control strategy for spectrum self-coexistence in multi-cell WRAN systems

The emerging IEEE 802.22-based Wireless Regional Area Network (WRAN) is the first wireless standard based on the Cognitive Radio (CR) technology. WRAN is designed to offer wireless access services in a large coverage area by allowing Secondary Users (SUs) to opportunistically exploit the under-utilized licensed portion of spectrum that is primarily allocated for TV services. To enable efficient WRAN communications, the operation of a WRAN system should address two types of coexistence problem: incumbent co-existence and self-coexistence. In this paper, we investigate the self-coexistence problem in a multi-cell WRAN system that adopts an exclusive spectrum sharing policy. Specifically, we present an adaptive channel allocation scheme based on a cooperative max–min weighted fair allocation strategy. The proposed scheme is based on a centralized sensing mechanism that identifies the available spectrum opportunities for the WRAN cells. Our scheme dynamically allocates the available spectrum (idle channels) to the WRAN cells based on their expected traffic loads such that the total number of simultaneously admitted SU transmissions in the WRAN system is maximized. The expected traffic load is accurately estimated using a sample mean estimator based on previously monitored traffic in each cell. Simulation results indicate that our scheme is quite robust to traffic estimation error. Compared to reference spectrum allocation schemes, simulation results indicate that the proposed scheme effectively exploits the available spectrum opportunities by increasing the total number of served SU transmissions, which consequently results in a significant enhancement in the overall WRAN system performance.

Investigation on electromagnetic environment of radio-over-fiber-based broadband wireless access scheme in aircraft cabin

Broadband wireless access services inside aircraft cabin are highly desired, but they may bring severe electromagnetic interference (EMI) threats to the avionic system and the flight safety. A radio-over-fiber (ROF)-based distributed scheme is proposed to provide onboard wireless access services. Due to the low emission power of the ROF-based distributed antennas and the electromagnetic radiation-free fiber links, the proposed scheme can effectively reduce the EMI threats from the in-flight wireless access. To evaluate the electromagnetic environment of the ROF-based distributed access scheme, the coupling electric field inside the cabin is calculated by using EMPIRE-XCcel (electromagnetic simulation software). Taking the aircraft-Advanced Regional Jet for the twenty-first century (ARJ21) for example, the results show that inside the cabin, a reduction of 4–8 dB in the coupling electric field strength is achieved using the ROF-based access scheme, compared with that in conventional centralized system. Meanwhile, a higher energy efficiency is ensured as well. Likewise, lower coupling electric field strength can also be provided for other large-size aircrafts of Airbus and Boeing, by using the ROF-based distributed scheme.

Adaptive Spectrum Management of Cognitive Radio in Intelligent Transportation System

With the rapid development of urban rail transit, the demand of the public in rail transportationto take real-time, reliable and efficient wireless access services, has become the focus of mobilebroadband communications. Wireless cognitive radio (CR) over urban rail transit is a newly emergingparadigm that attempts to opportunistically transmit in licensed frequencies, without affecting the preassignedusers of these bands. To enable this functionality, such a radio must predict its operationalparameters, such as transmit power and spectrum. These tasks, collectively called spectrum management,is difficult to achieve in a dynamic distributed environment, in which CR users may only takelocal decisions, and react to the environmental changes. In this paper, we propose a reinforcementlearning based approach for spectrum management. Our approach uses value functions to evaluate thedesirability of choosing different transmission parameters, and enables efficient assignment of spectrumsand transmit powers by maximizing long-term reward. We then investigate various real-worldscenarios, and compare the communication performance using different sets of learning parameters.The results proves our reinforcement learning based spectrum management can significantly reduceinterference to licensed users, while maintaining a high probability of successful transmissions in acognitive radio ad hoc network.

Phased Scheduling for Resource-Constrained Mobile Devices in Mobile Cloud Computing

Mobile cloud computing combines wireless access service and cloud computing to improve the performance of mobile applications. Mobile cloud computing can balance the application distribution between the mobile device and the cloud, in order to achieve faster interactions, battery savings and better resource utilization. To support mobile cloud computing, the paper proposes a phased scheduling model of mobile cloud such that mobile device's users experience lower interaction times and extended battery life. The phased scheduling optimization is solved by two subproblems: mobile device's batch application optimization and mobile device's job level optimization. At the first stage, the mobile cloud global scheduling optimization implements the allocation of the cloud resources to the mobile device's batch applications. At the second stage, mobile device's job level optimization adjusts the cloud resource usages to optimize the utility of single mobile device's application. In the simulations, compared with other algorithm, our proposed mobile cloud phased scheduling algorithms achieve the better performance with acceptable overhead.

Design of Femtocell-Based Smart Home System Gateway

With the development of Internet technology and communication technology, traditional base station has been unable to meet the demand for high data services. In view of this, we propose the system core with Samsung S3C2440X processor constructs smart home hardware platform and using ADI ADF4602 single-chip, multiband 3G Femtocell transceiver to establish 3G home base stations, designed and realized an embedded gateway server through the house gateway to realize the family appliance equipment remote monitoring. Of software design, focusing on smart home control system, transplantation of embedded operating system uClinux to manage system resources, constructed a complete family gateway hardware and software platform, which can reduce the load of Microcell, improve the whole network capacity, and provide high-speed and high-quality indoor wireless access services.

WDM-PON access network with lightwave source centralized full-duplex link based on SSB-OOFDM for wired and 60 GHz band wireless alternative accesses

A novel lightwave centralized full-duplex WDM-PON access network based on single sideband optical orthogonal frequency-division multiplexing (SSB-OOFDM) is proposed for providing wired and 60-GHz band wireless accesses alternately. At the OLT, the multi-channels with 10-Gb/s 4-QAM-RF-OFDM signals are SSB modulated on the optical local oscillators (OLOs). At the RN, one OOFDM signal along with two OLOs is abstracted and switched to the corresponding HONU, where the signal can be downconverted to the 10-GHz or 60-GHz band RF-OFDM signal by one OLO for wired or wireless access, while the other one is used to bear the uplink signal. Since the HONU is free from the light sources, the system complexity and cost are reduced. Full duplex transmission over 25km fiber have been demonstrated that the error vector magnitude (EVM) of the down- and up-link signals are much below the FEC limit for both the wired and 60-GHz band wireless access services.

Interference Potential of FSS and BWA on the Extended C-Band

The Indonesian government has allocated the 3.3-3.4 GHz band, which is adjacent to the extended C-band 3.4-3.7 GHz, for Broadband Wireless Access (BWA) services. The country has been using the extended C-band for Fixed Satellite Service (FSS). This research shows the interference potential between the two systems if an adjacent band is allocated for them. Using a clutter loss of 10 dB and site shielding of 40 dB, a BWA network consisting of 57 base-stations will potentially intefere an FSS with probability 56.16% if the protection distance used is 1.55 km. The interference potential will decrease to 0% if the protection distance is increased to 3 km. With a BWA network consisting of 20 base-stations, the interference probability is 10.72% and 0% for a protection distance of 1.55 km and 2 km, respectively. With this interference potential it is urgent that Indonesia enforces interference mitigation techniques to protect FSS from disruptive interference.

Dynamic Service Selection and Bandwidth Allocation in IEEE 802.16m Mobile Relay Networks

Cooperative relay network will be supported in IEEE 802.16m to improve the coverage and performance of mobile broadband wireless access service. In this paper, we jointly consider the problem of dynamic service selection and bandwidth allocation in IEEE 802.16m mobile relay networks. Specifically, the advanced mobile stations (AMSs) perform the selection of advanced base station (ABS) and transmission mode (i.e., direct transmission or relay-cooperation transmission) for a better service quality. The ABSs allocate the bandwidth for different transmission modes to maintain the desired queue level at base stations and user distribution for satisfying performance requirements. This problem is challenging when the strategies of both ABSs and AMSs influence each other and the decisions are made dynamically. To address this problem, a two-level dynamic game framework based on an evolutionary game and a differential game is developed. Since the mobile stations can adapt their strategies according to the received service quality, the dynamic service selection is modeled as an evolutionary game at the lower level. At the upper level, a differential game is formulated for a dynamic bandwidth allocation of base stations and a closed-loop Nash equilibrium is obtained as the solution. Viewing the fluctuation of traffic flow rate as disturbance, the robust bandwidth allocation strategy design is performed. Both stochastic optimal control and H_∞ optimal control approaches are adopted for average performance and worst-case performance design, respectively.

ISAR: Improved Situation-Aware Routing Method for Wireless Mesh Backbones

Due to the increasing performance requirements of wireless access services, adaptive interference resistant routing is crucial for providing reliable access and high bandwidth services via wireless mesh networks. In this letter, we propose an improved method for situation-aware routing, which extends the existing routing protocols via a refined situation-aware routing metric and a greedy load-balancing routing scheme. Simulation results demonstrate that the proposed method can achieve a higher throughput with lower transmission delay compared to previous routing schemes.

Efficient Delivery of Integrated Wired and Wireless Services in UDWDM-RoF-PON Coherent Access Network

A high-capacity coherent ultradense wavelength-division multiplexing passive optical network integrated with a 60-GHz radio-over-fiber system has been designed and experimentally demonstrated for the first time. In this proposed architecture, millimeter-wave signal generation is achieved by coherent technology, in place of the optical carrier suppression technique, which requires modulators with large bandwidth and precise optical interleavers. The system fully exploits advantages of coherent access networks to provide both multigigabit wired and wireless access services with high spectral and power efficiencies. Successful wireless transmission of multichannel 3.3-Gb/s quadrature phase-shift keying signals with 10-GHz channel spacing over 50-km single-mode fiber (SMF-28) has been achieved.

POINT-POINT FIXED WIRELESS AND BROADCASTING SERVICES COEXISTENCE WITH IMT-ADVANCED SYSTEM

Spectrum sharing analysis is remarkably important in investigating the possibility for coexistence between IMT-Advanced system and existing wireless services when operating in the same or adjacent frequency channel. The frequency band, 470{862MHz, is currently allocating to TV broadcasting services (TVBS) and sub- bands within it are also allocated to flxed wireless access (FWA) service. Recently, international telecommunication union-radio (ITU- R) sector has allocated sub-bands within 470{862MHz for IMT- Advanced systems. This concurrent operation causes destructive interference that in∞uences the coexisting feasibility between IMT- Advanced and these existing services, FWA and broadcasting. This paper addresses a timely and topical problem dealing with spectrum sharing and coexistence between IMT-Advanced systems and both FWA and TVBS within 790{862MHz. Co-channel and adjacent channel with an overlapping band and with or without guard band are intersystem interference scenarios investigated. The deterministic analysis is carried out by spectral emission mask (SEM) technique as well as interference to noise ratio graph. Various signiflcant factors such as channel width, propagation path lengths, environments losses, and additional losses due to antenna discrimination which in∞uence the feasibility of coexistence are evaluated. Feasible coexistence coordination procedures in terms of carrier frequency ofiset, separation

WiMAX-UMTS Converging Architecture with IMS Signalling Analysis to Achieve QoS

The third-generation partnership project (3GPP) and 3GPP2 have standardized the IP multimedia subsystem (IMS) to provide ubiquitous and access network-independent IP-based services for next-generation networks via merging cellular networks and the Internet. The IEEE 802.16 worldwide interoperability for microwave access (WiMAX) promises to provide high data rate broadband wireless access services. The IP Multimedia Subsystem (IMS) seems to be the technology that will prevail in Next Generation Networks (NGN s), since the interworking environment and the service flexibility that this technology offers to the currently deployed wireless broadband technologies makes it appealing to users, service developers and network operators. In this paper we propose a heterogeneous network model based on the IMS that integrates the Worldwide Interoperability for Microwave Access (WiMAX), Universal Mobile Telecommunications System (UMTS) and provides guaranteed QoS. In this paper, hybrid interworking architecture to integrate 3G (UMTS) and WiMAX networks with QoS is proposed. Moreover, IMS based signaling along with QoS algorithm was analyzed for UMTS and WiMAX interworking Architectures. QoS parameters such as Ethernet load and delay, IP Packet end to end delay, TCP delay, Active TCP connection count and TCP retransmission count, Email download response and upload response, Voice jitter, Voice packet delay variations and voice traffic received were analyzed.

Network Selection in Heterogeneous Wireless Networks based on Fuzzy Multiple Criteria Decision Making

Next generation wireless networks are expected to exhibit heterogeneity in terms of wireless access technologies, services and application requirements. These heterogeneous wireless access networks consist of the integration of various wireless networks especially Wi-Fi (WLAN), Wi-Max and 3G/B3G cellular networks. One of the challenging problems is to choose the optimal network depending upon the type of the demanding application. Vertical handoff occurs when a mobile terminal decides to switch to the selected network from the current network. This paper mainly deals with a network selection algorithm based on Fuzzy Multiple Attribute Decision Making. The algorithm considers the factors of Received Signal Strength(RSS), Monetary cost(C), Band Width (BW), Velocity (V) and user preference (P). It finds the Network selection function (NSF) that measures the efficiency in utilizing radio resources by handing off to a particular network. The network that provides highest NSF is selected as the best network to hand off from the current access network.

An iWBC consumer application for 'always best connected and best served': design and implementation

This paper describes the design and implementation of a new consumer product, namely a generic intelligent iWBC client application. This application sits on a mobile terminal (MT) and operates in the background in support of the mobile consumer-user becoming fully aware of all relevant wireless services available in the location of the MT and which are advertised according to a structured format over wireless billboard channels (WBCs) which are broadcasted and receivable in the same location. The WBCs' role primarily is to facilitate wireless access networks advertising their wireless communication access services to consumers, on their MTs and do this in a background neartransparent way. Information about available services is proactively pushed to users' MTs. The MTs can thus discover the services and all the necessary details about these service offerings sufficient to make informed `always best connected and best served' (ABC&S) decisions about using them, including knowing how to associate with the access networks to obtain these services in the best possible way through an advertisement, discovery and association (ADA) procedure. Other teleservice providers can also advertise their service offerings via WBC and have them handled by this iWBC application in a similar way. Hence this novel iWBC application amounts to a significant advance in consumerdriven ABC&S capabilities and services.

3G Spectrum Auctions in India: A Critical Appraisal

The spate of controversy and the flurry of charges surrounding the allocation of spectrum for the second generation (2G) mobile telephony services on a First Come First Served (FCFS) basis stands out in stark contrast to the near universal acclaim for the allocation of spectrum for the Third Generation (3G) and Broadband Wireless Access (BWA) services by an open and a transparent auction process. Prima facie, the obvious inference is that auction should be a preferred route to allocate scarce resources such as spectrum. However, such an unqualified conclusion warrants an important caveat: that this is conditional upon getting the auction design right. There have been several instances of ill-designed auctions that had unintended consequences of allocating resources at throwaway prices or having fetched such high revenues as to impede the roll-out of services, besides endangering the financial health of the entire sector. Thus the strategic choices made in the auction design have an important bearing on the ends that one seeks to achieve vide the auctions viz. revenue realization, efficient allocation, a more competitive post auction market structure resulting in lower cost of access for the consumers.In this paper, we analyze the design employed in the auctions for spectrum to roll out Third Generation mobile services (3G) & Broadband Wireless Access services (BWA) in India and its success or otherwise on the above mentioned parameters. We find that while the auction has been successful in mobilizing revenue for the government, has created little adverse impact for the consumers by maintaining the level of competitiveness in the mobile services market but the gains seem to have been partially offset by compromising the efficiency parameter. It is argued that, in making the Lowest Accepted Bid as a preferred pricing rule, the Government accorded primacy to the revenue realization motive over maximization of allocational efficiencies although the reverse has been stated as policy objective in going for the auction. A few alternative design elements have been suggested that would have served the stated objective of enhancing allocational efficiencies better

A Novel Transmitter and Receiver Structure for Cognitive Radio Based OFDM Systems

Wireless regional area network (WRAN) is intended to offer the fixed wireless access services using cognitive radio technology in the TV white space. Therefore, WRAN shall minimize the transmission power so that harmful interference is not imposed on the licensed users operating in the TV bands. In this paper, we propose a processing block that offers improvements in the SNR and diversity gain using the block to algebraically process two constellation symbols. Thus, the transmission power can be reduced by an amount equal to the gains. The simulation result shows that the proposed scheme has a better bit error performance than the transmission scheme defined in the IEEE 802.22 draft standard.

Broadband Openness Rules are Fully Justified by Economic Research

This paper responds to arguments made in filings in the FCC’s broadband openness proceeding (GN Dkt. 09-191) and incorporates data made available since my January 14th filing in that proceeding. Newly available data confirm that there is limited competition in the broadband access marketplace. Contrary to some others’ arguments, wireless broadband access services are unlikely to act as effective economic substitutes for wireline broadband access services (whether offered by telephone companies or cable operators) and instead are likely to act as a complement. Nor will competition in the Internet backbone marketplace constrain broadband providers’ behavior in providing “last mile” broadband access services. The last mile, concentrated market structure, combined with high switching costs, provides last mile broadband network providers with the ability to engage in practices that will reduce social welfare in the absence of open broadband rules. Furthermore, the effect of open broadband rules on broadband provider revenues is likely to be small and can be either positive or negative.Unfortunately, various filings have misstated or mischaracterized the results on the economics of two-sided markets. Contrary to what some have argued, allowing broadband providers to charge third party content providers will not necessarily result in lower prices being charged to residential Internet subscribers. This is true under a robust set of assumptions. Despite some parties’ mischaracterization of the economic literature, price discrimination by broadband providers against third party applications and content providers will reduce societal welfare for numerous reasons. This reduction in societal welfare is especially acute when price discrimination is taken to the extreme of exclusive dealing between broadband providers and content providers. Antitrust and consumer protection laws are insufficient to protect societal welfare in the absence of open broadband rules.

Traffic characterization of a residential wireless Internet access

Traffic characterization is an important means for Internet Service Providers (ISPs) to adapt and to optimize their networks to the requirements of the customers. Most network measurements are performed in the backbone of these ISPs, showing both, residential and business Internet traffic. However, the traffic characteristics of business and home users differ significantly. Therefore, we have performed measurements of home users at a broadband wireless access service provider in order to reflect only home user traffic characteristics. In this paper, we present the results of these measurements, showing daily traffic fluctuations, flow statistics as well as application distributions. The results show a difference to backbone traffic characteristics. Furthermore, we observed a shift from web and Peer-to-Peer (P2P) file sharing traffic to streaming applications.