Increase System Capacity Research Articles

Turning Point: implications for collaborative governance

PurposeThe purpose of this paper is to show how the Turning Point Initiative to improve the health of populations by improving the USA public health system has many lessons on collaboration for governance systems.Design/methodology/approachThe article synthesizes published literature outlining the results of a Robert Wood Johnson Foundation/W.K. Kellogg Foundation grant program to 21 USA states and 43 communities and relationships to administrative practice.FindingsTurning Point's creation of a formalized network of public health partners across the USA has led to innovations in collaboration, increased system capacity, and alternative structures for improving health.Originality/valueTurning Point's efficacy in community health system improvement can be mirrored in clinical governance. A major potential for improvement in clinical delivery systems is available by re‐thinking key partners, organizational structures, and system administrative capacity.

Link quality-aware call admission strategy for mobile cellular networks with link adaptation

In this paper, the performance of mobile cellular systems with link adaptation (LA) is analytically evaluated. Half- and full-rate vocoders are considered in the analysis. Mathematical expressions for the new call blocking, handoff failure, and forced termination probabilities are obtained. To our knowledge, no similar analysis considering LA exists in the literature. Also, the link quality-aware dual fractional channel reservation (LQA DFCR) scheme is proposed. In LQA DFCR, user differentiation is implemented in terms of link quality. Preference is given to users with good link quality because they require fewer resources than users with bad link quality. Numerical results show that the proposed LQA DFCR scheme effectively increases system capacity: LQA DFCR achieves more than a 11% capacity gain relative to systems with the non priority scheme (NPS) and with LA, and approximately 3% relative to the fair access prioritisation scheme (FAPS) strategy. Numerical results also show that LA yields an approximately 18% capacity increase relative to a cellular system without LA when no admission control is employed (admission control strategies further increase system capacity.) The synergy between LA and admission control strategies yields more than a 31% capacity gain

DS-CDMA downlink system capacity enhancement through interference suppression

In the downlink of direct-sequence code-division multiple-access (DS-CDMA) cellular systems, system capacity is limited by multiuser interference. This interference can be suppressed at the receiver by interference whitening approaches such as chip equalization and generalized RAKE (G-RAKE) reception. In this paper, we show how these advanced receivers can increase system capacity. First, the G-RAKE receiver formulation is extended to include soft handoff and other-cell interference. Then, voice capacity is evaluated, including the effects of fast fading, interference correlation, power control, orthogonality properties of own-cell signals, and soft handoff. Numerical results for the wideband CDMA system show that when the channel is dispersive, advanced receivers improve capacity by 30-34%

An opportunistic power control algorithm for cellular network

We propose an opportunistic power control algorithm, which exploits channel fluctuation in order to maximize system throughput. The basic idea is that it instructs a transmitter to increase its power when the channel is good and to decrease its power when the channel is bad. The transmission rate is adjusted according to the received signal-to-interference ratio. The proposed algorithm is distributed and can be applied to systems in which the transmitters are connected to different receivers. We prove that the algorithm always converge to a unique fixed point and thus is stable. Simulation results show that a tremendous increase in system capacity can be achieved, when compared with other power control algorithms. Furthermore, the algorithm works well for nonreal-time terminals when other real-time terminals employ the target-tracking power control. It can also be extended to cases where maximum power constraint is imposed and soft handoff is executed.

A Baseband Demonstrator Using Multi Antenna Techniques to Improve Capacity of Fixed Broadband Wireless Access

In the last five years, transmissions using multiple sensors at both ends of the link have been a major research topic. Many transmission schemes are studied such as point to point links using diversity coding, point to point links using multiplexing, tradeoffs between both and at last multi-point to point links. This last scheme was already covered by Space Division Multiple Access (SDMA) processing but a step forward was made with multiple subscriber detection. This paper asses the multi-point to point links for uplink and point to multi-point for the downlink based on OFDM waveform in the frame of the Wireless Metropolitan Area Network (WMAN) IEEE Std 802.16-2004 or HIPERMAN standard. It describes a realistic implementation of transceivers for Physical (PHY) layer to Medium Access Control (MAC) layer allowing a system capacity increase with minor modifications of the standard and with a low impact on the complexity of the subscriber equipment. In this context, this paper proposes to focus on based-band techniques: The Obele algorithm based on the channel knowledge in the downlink and multiple-user detection in the uplink. The algorithm complexity and the tradeoffs for implementation are extensively discussed.

Soft handoff and connection reliability in cellular CDMA downlinks

A two-phase soft handoff scheme, which includes an initial power allocation phase followed by a power redistribution phase, is proposed. The initial power allocation phase makes a handoff decision for each connection by assigning a connection to the BS with the best link quality and allocating a minimum amount of power from the BS for the connection. The initial handoff decisions are made for individual connections independent of other connections or the BS power availability. Therefore, there might be heavily loaded and lightly loaded BSs because (i) traffic load may not be equally distributed in all cells, and (ii) the channel condition of the connections is random. The power re-distribution phase is to smooth out the loading on the system by coordinating the power allocations among neighboring BSs so that more connections can receive reliable transmissions. We then develop an analytical model for studying the connection reliability with the proposed soft handoff scheme. Our results show that the proposed two-phase soft handoff scheme can significantly improve connection reliability and increase system capacity in downlink transmissions.

Performance of Adaptive Subchannel Assignment-Based MIMO/OFDM Systems over Multipath Fading Channels

Adaptive antenna arrays at both the base and mobile stations can further increase system capacity and improve the quality of service of conventional orthogonal frequency division multiplexing (OFDM) systems. Conventional adaptive antenna array-based multiple-input multiple-output (MIMO)/OFDM systems use the sub-carriers characterized by the largest eigenvalue to transmit the OFDM symbols. This paper describes the performance of adaptive subchannel assignment-based MIMO/OFDM systems over multipath fading channels. The system adaptively selects the eigenvectors associated with the relatively large subchannel eigenvalues to generate the antenna array weights at the base and mobile stations and then adaptively assigns the corresponding best subchannels to transmit the OFDM symbols. Simulation results show that the proposed system can achieve better performance than the conventional adaptive antenna array-based MIMO/OFDM system over multipath fading channels.

Semantic mining and web service discovery techniques for media resources management

The proposed techniques facilitate semantic discovery and interoperability of web services that manage and deliver web media content. As a test-bed, a web management system is discussed that provides vocational monographs for occupational guidance. The key idea of the proposed web service based architecture is that the WS of participating members share their vocational monographs and related resources, resulting in the overall system capacity increase. Mechanisms and techniques are presented concerning: an 'information desk', which provides an adaptive search user interface; discovery functions based on semantic representation of the WS' monographs; mining into monographs based on their semantic representation; a metric-based evaluation model for the web monographs; dynamic ranking of retrieved content list; consumption mechanisms for the career counsellors' local WS; e-payment; universal usability access. This analysis can be exploited in the practice of a new Occupational Guidance Policy.

On Array Failure Mitigation With Respect to Probability of Failure, Using Constant Excitation Coefficients and a Genetic Algorithm

Switched-beam antenna arrays (SBAs) are widely used in communications systems in order to increase system capacity and spectral efficiency. If an element fails during operation, a significant degradation of the array's performance is observed, even after redistribution of the array's excitation coefficients. Furthermore, redistribution of the excitation coefficients is not always possible. In this letter, a study on the effect of an element failure to an array's radiation patterns, with respect to the probability of failure, is performed. It is shown that mitigation of failure effects is possible if the possibility of failure is taken into account during early design stages. This is accomplished by using a modified genetic algorithm (GA). With the proposed methodology, mitigation is achieved even without the need to redistribute the array's excitation coefficients.

A novel adaptive joint power control algorithm with channel estimation in a CDMA cellular system

Joint power control has advantages of multi-user detection and power control; and it can combat the multi-access interference and the near-far problem. A novel adaptive joint power control algorithm with channel estimation in a CDMA cellular system was designed. Simulation results show that the algorithm can control the power not only quickly but also precisely with a time change. The method is useful for increasing system capacity.

Design and analysis of Bluetooth scatternet for mobile multimedia applications

PurposeTo present a combination of Bluetooth handoff techniques and scatternet formation to adapt to varying topologies and traffic changes.Design/methodology/approachThrough ad hoc networking with Bluetooth, devices could participate in multiple piconets, which form the scatternet. Although the details of scatternet implementation are not specified in the Bluetooth specification, much research has been carried out to propose different models of implementation. This paper presents a combination of the techniques of handoff and scatternet formation to adapt to varying topologies and traffic changes. Analysis of network performance is presented to confirm the feasibility of real implementation.FindingsProvides a novel and practical design, compatible with Bluetooth specification, which is shown by experimental results to be an efficient design in providing a scatternet formation approach, while at the same time maintaining a low data error rate to support data and voice.Originality/valueThis paper presents Bluetooth handoff and scatternet formation techniques to extend geographical coverage and increase system capacity with adaptation to varying topologies and traffic changes. The techniques presented are compatible with Bluetooth specifications 1.0, 1.1 and 1.2.

Capacity and Coverage Increase With Repeaters in UMTS Urban Cellular Mobile Communication Environment

In this letter, we propose to use repeaters to increase system information capacity in urban areas, where path loss exponents are higher (as much as 3.4 or more). There is at least a 10% increase in coverage area when repeaters are placed in every cell within the network to increase system capacity. The overall system information capacity is doubled at propagation exponent 3.7-3.9.

Network optimization trials of a vendor-independent methodology using the Ocelot® tool

Bell Labs Research and Lucent Worldwide Services (LWS) have developed a radio frequency (RF) optimization service to improve performance of cellular networks. This service utilizes the Bell Labs-developed Ocelot® software platform, which can simultaneously optimize coverage and capacity of the wireless air interface utilizing automated optimization routines. Field trials of the Ocelot platform have been conducted on two major wireless providers' networks. The first trial, conducted in a 20-cell region, showed an 18% increase in capacity, a 36% reduction of blocked calls, and a 20% reduction of dropped calls. The second trial, conducted in a 44-cell region, showed a 22% increase in capacity, a 10% reduction in blocked calls, and a 7% reduction in dropped calls. The Ocelot-related network improvements were achieved by making adjustments to antenna tilt/azimuth/pattern and transmit powers. The increased system capacity deferred (and in some cases reduced) the purchase of additional hardware. The methodology and the Ocelot tool are vendor independent. As a result of these trials, LWS has introduced new service offerings based on this tool.

An adaptive cross-layer scheduler for improved QoS support of multiclass data services on wireless systems

With the rapid growth of the Internet and other Internet protocol-related applications, wireless systems have shifted toward supporting a wider variety of data services. This has placed an enormous strain on the already tight capacity of wireless systems. Many improvements have been made at the link layer in second- and third-generation wireless systems. However, further improvements in packet data admission, scheduling, and policing are necessary to maximize capacity and user satisfaction. Of the three, efficient scheduling has the greatest impact on increased system capacity. In addition, proper scheduling can greatly improve user satisfaction. We introduce an adaptive cross-layer packet scheduler, which outperforms popular packet schedulers with respect to both packet delay and user throughput.

Adaptive Joint Detection of Cochannel Signals for TDMA Handsets

In mobile communication systems, downlink (forward link) system capacity is limited by the ability of mobile receivers to recover the desired signal in the presence of cochannel interference (CCI). Joint detection of the desired and cochannel signals is a useful approach to improving receiver performance, thus increasing system capacity. In this paper, we show that a practical single-antenna joint-detection receiver can provide significant gains in system capacity for the time-division multiple-access (TDMA) standard Telecommunications Industry Association/Electronic Industry Association/Interim Standard-136 (TIA/EIA/IS-136 or IS-136). For a sectorized system, joint detection provides a capacity gain of 47% in a typical urban environment. When used in conjunction with transmit beamforming, the synergy between the two approaches leads to a capacity gain of over 200%. In determining these gains, practical aspects of the IS-136 system are considered, namely, unsynchronized networks, limited receiver complexity, and adaptability. A semiblind acquisition process, which uses the training sequence of the desired user only, is employed, because the desired and interfering base stations are not synchronized. The receiver complexity is controlled by processing only one sample per symbol period, even though it is shown that multiple samples per symbol period should ideally be used. Finally, because receiver performance may be limited by its own intersymbol interference instead of CCI, an adaptive joint-detection process is used which selects between joint demodulation and single-user equalization for each slot.

Multiple-logical-channel subsystems: Increasing zSeries I/O scalability and connectivity

With the advent of the z990 multi-book multiprocessor family of server offerings, significant increases in total system capacity and scalability can be realized. Essential to an increased processing capacity is the corresponding need for significant increases in total I/O scalability and connectivity. With the z990, increased I/O capacity is provided by increasing the number of physical I/O channels that can be configured to the system and by restructuring the physical channel subsystem (CSS) into logically distinct channel subsystems. This restructuring is commonly called the multiple-channel subsystem (MCSS) facility. Each logical CSS is then assigned to one or more logical partitions as necessary in order to provide the total I/O connectivity necessary to accommodate the increased processing capacity of the system. An overview of the z990 MCSS architecture is presented with respect to how it is structured, the channel-subsystem constraints that have been removed, and how MCSS functions are provided to the operating systems executing in each of the system's logical partitions (LPARs) in a predominantly transparent manner. Also discussed is the channel-subsystem ardware and firmware (embedded software) design necessary to accommodate the MCSS architecture, as well as overviews of the MCSS I/O configuration process and the z/OS® programming support necessary to accommodate the MCSS facility. Finally, enhancements to the MCSS I/O measurement facility necessary to facilitate autonomic computing are discussed.

Optimization of Satellite Access Lower Layers for the Transport of IP Datagrams

This paper presents a novel solution optimizing satellite access lower layers and system performances called variable size packets (VSPs) designed for the transport of Internet protocol (IP) datagrams or any packet type from the network layers characterized by a highly variable size. VSP objective is to maximize the efficiency of layers 1 and 2 through a joint optimization of access and transport mechanisms mainly for satellite systems addressing residential or corporate terminals market through a multiple-access scheme. It is particularly attractive for the return link of next-generation satellite systems to be IP-based, as a possible evolution of the digital video broadcast-return channel via satellite (DVB-RCS) standard. The VSP solution relies on the definition of multiple encapsulation sizes, and is associated to a waveform and an access adapted to variable size packets' transport. It uses the traffic's variable size nature to increase encapsulation efficiency, coding, and spectral efficiency performances, and system flexibility. It is well adapted to systems using an adaptive waveform leading to system capacity's increase and better performances. This paper describes the VSP principle, advantages and possible high-level system tradeoffs. It then focuses on one critical issue, the coding, and presents a suitable coding scheme's choice with regards to performances and implementation complexity.

Optimum Traffic Distribution Algorithm for Multiple-Satellite Systems Under Power Constraints

In satellite communications systems, in addition to frequency resources, total satellite transmitting power, (i.e., satellite power) is a crucial radio resource, due to the limited capacity of onboard electric generators. To increase system capacity, satellite power constraints have to be taken into account, as well as the frequency constraints. As one approach to this issue, we propose a traffic distribution algorithm using linear programming, which maximizes the accommodated traffic in a multiple-satellite system under satellite power constraints. The algorithms are applicable to all types of satellite systems with multiple satellites (geosynchronous Earth orbit, medium Earth orbit, low Earth orbit, or a combination of any) to increase system capacity with respect to the total amount of traffic accommodated by the systems. Finally, this paper evaluates the performance of the proposed algorithm by distributing traffic demand on the earth's surface to cells irradiated by spot-beams of a satellite and allocating frequency resources to the cells. By using the algorithm that permits power constraints, the ratio of accommodated traffic in a system was improved 12% compared with the case when no power constraints were used.

Two-hop-relay architecture for next-generation WWAN/WLAN integration

Next-generation wireless systems (4G and beyond) are envisioned to provide ubiquitous high-speed access over heterogeneous radio technologies. The integration of cellular WWANs and WLANs has drawn considerable attention from the research and commercial communities (e.g., 3G+802.11). Emerging dualmode mobile terminals could provide flexibility and system performance enhancement by providing seamless roaming between WWANs and WLANs. In this article we propose a novel integrated WWAN/WLAN two-hop-relay architecture that both enhances the system capacity of existing WWAN systems and extends the system coverage of WLAN terminals. The proposed two-hop-relay architecture can be considered as a system-level macro diversity technique that utilizes temporal channel quality variation to achieve increased system capacity. Significant capacity gain is achieved with the proposed twohop-relay architecture in both a fixed-rate uplink CDMA system and a variable data rate downlink HDR-like system.

Enhancing the Capacity of DS-CDMA System Using Hybrid Spreading Sequences

A new direct-sequence code-division multiple-access (DS-CDMA) system using hybrid spreading sequences in order to increase system capacity is proposed. This scheme permits accommodating more than N users, where N is the processing gain of the spreading sequences. Users are divided into two classes. The centerpiece idea is to synchronously assign N mutually orthogonal codes to class-1 users, and asynchronously assign quasi-orthogonal codes to class-2 users. The proposed architecture is realized through the DS-CDMA and multicode CDMA (MC-CDMA) techniques for class-1 and class-2 users, respectively, and the system capacity is considerably enhanced as compared with Sari et al.. The new approach still excels over Vanhaverbeke et al. when the number of class-1 users K/sub 1/ is large; but our desire is to expand system capacity. Compared with Sari et al. and Vanhaverbeke et al., the new design is able to support multirate applications, and is especially suitable for high-speed multimedia transmissions. Furthermore, the performance of the MC-CDMA system over an additive white Gaussian noise channel is evaluated for various primary codes and mutually orthogonal subcodes. It is shown that orthogonal Gold codes concatenated with Hadamard sequences yield the lowest bit-error rate when the signal-to-noise ratio lies between 0 and 30 dB.