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For all companies that consider their Information Technology Department to be of strategic value, it is important to incorporate an innovation value chain into their software development lifecycles to enhance their teams' performance. One model is TDD (Test-Driven Development), which is a process that detects failures and improves the productivity and quality of the team’s work. Data were collected from a Financial Company with 3,500 employees to demonstrate that software projects that require more than 4,000 hours of development benefit from TDD if a clear knowledge conversion step occurs between the client and the developers.

The results of developing a method of distribution of the frequency and time resources downlink technology LTE were presented. The proposed method is aimed to ensure the quality of service of wireless for users by allocating the user station required capacity in the downlink. A comparative analysis were done of the proposed method with known solutions of distribution time-frequency resources of LTE technology in terms of the overall performance of the downlink, the degree of balancing capacity, as well as the confidence level allocating user stations required capacity. [ABSTRACT FROM AUTHOR]

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This paper proposed an uplink CSI based adaptive pre-repeat GBN-HARQ scheme to solve the problem that the throughput and delay of traditional pre-repeat GBN-ARQ scheme declined greatly at low BER. First, transmitter encoded the data with FEC and obtained different redundant versions. And then, the method adaptively chose the number of redundant versions for retransmission packets according to the uplink CSI, transmitted multiple redundant versions to ensure the reliability of pre-repeat transmission in the poor condition of wireless channel and reduce delay caused by the error in retransmission and it used few redundancies to ensure high throughput in the good condition of wireless channel. Finally, it compared and analysed the throughput for the traditional GBN-ARQ scheme, pre-repeat GBN-ARQ scheme and adaptive pre-repeat GBN-HARQ scheme. The simulation results show the throughput of adaptive pre-repeat GBN-HARQ scheme improves about 0. 1 than traditional GBN-ARQ scheme and about 0. 05 than pre-repeat GBN-ARQ scheme as the BER exceeds 10, that is to say, the uplink CSI based adaptive pre-repeat GBN-HARQ scheme can further guarantee the reliability at high BER. [ABSTRACT FROM AUTHOR]

Usually we read about agile development practices that seem like no more than hand waving. If that's how you feel, you'll enjoy traveling this detailed design journey and seeing up close how test-driven development (TDD) and refactoring are done in an agile environment. This article is especially insightful because of the collaborative shepherding by Rebecca Wirfs-Brock. [ABSTRACT FROM PUBLISHER]

In this paper, we develop an uplink pilot and downlink link adaptation approach to improve the energy efficiency (EE) of mobile users in time division duplexing (TDD) multi-user multiple input and multiple output (MU-MIMO) systems. Assuming reciprocity between uplink and downlink channels, the downlink transmission is based on uplink channel estimation. While more uplink pilot power ensures more accurate channel estimation and better downlink performance, it incurs higher energy consumption of mobile users. This paper reveals the relationship and tradeoff among pilot power, channel estimation, and downlink link adaptation that achieves the highest energy efficiency for mobile users. We show that the energy efficiency of different users can be decoupled because the downlink average throughput of each user is independent of the pilot powers of other users and energy-efficient design can be done on a per-user basis. Based on the analysis, we propose an uplink pilot and downlink link adaptation algorithm to improve the EE of mobile users. Simulation results are finally provided to demonstrate the significant gain in energy efficiency for mobile users. [ABSTRACT FROM PUBLISHER]

Innovation and new molecular entity production by the pharmaceutical industry has been below expectations. Surprisingly, more first-in-class small-molecule drugs approved by the U.S. Food and Drug Administration (FDA) between 1999 and 2008 were identified by functional phenotypic lead generation strategies reminiscent of pre-genomics pharmacology than contemporary molecular targeted strategies that encompass the vast majority of lead generation efforts. This observation, in conjunction with the difficulty in validating molecular targets for drug discovery, has diminished the impact of the “genomics revolution” and has led to a growing grassroots movement and now broader trend in pharma to reconsider the use of modern physiology-based or phenotypic drug discovery (PDD) strategies. This “From the Guest Editors” column provides an introduction and overview of the two-part special issues of Journal of Biomolecular Screening on PDD. Terminology and the business case for use of PDD are defined. Key issues such as assay performance, chemical optimization, target identification, and challenges to the organization and implementation of PDD are discussed. Possible solutions for these challenges and a new neoclassic vision for PDD that combines phenotypic and functional approaches with technology innovations resulting from the genomics-driven era of target-based drug discovery (TDD) are also described. Finally, an overview of the manuscripts in this special edition is provided. [ABSTRACT FROM PUBLISHER]

Real-time data transmission, especially video delivery over high-speed networks have very stringent constraints in terms of network connectivity and offered data rate. However, in high-speed vehicular networks, direct communication between vehicles and road side units (RSU) often breaks down, resulting in loss of information. On the other hand, a peer-to-peer based multihop network topology is not sufficient for efficient data communication due to large packet loss and delay. In this paper, a novel 'moving cluster multiple forward' (MCMF) architecture is proposed and investigated for efficient real-time data communication in high speed vehicular networks. MCMF involves novel aspects in relation to the formation of clusters and managing the communication between groups of vehicles and introduction of a hierarchical multiple forwarding mechanism which enables communication between any vehicle and RSU via other vehicles. Additionally, a novel protocol called 'alternate cluster resource reuse' (ACRR) is proposed and its detailed communication mechanism is presented. Simulation tests show how the use of MCMF and the ACRR protocol results in superior bit-rate performance-around three times that obtained in peer-to-peer multihop communications and twice that of MCMF with no ACRR protocol. Further, the average delay in MCMF-based transmissions from vehicle to RSU is around 50 % that of a peer-to-peer multihop communication mechanism. MCMF/ACRR has the potential to support multimedia traffic according to the IEEE 802.11p standard, even with a sparse investment in the infrastructure. [ABSTRACT FROM AUTHOR]

The combination of OFDM with joint pre-processing in adaptive multi-antenna systems offers both an ease of equalization in frequency-selective channels and keeping the signal processing at the mobile stations simple. In addition, the spatial dimension can be efficiently exploited to ensure high system throughput. With the utilization of higher-order modulation the performance of the system is highly sensitive to multiple access interference and nonorthogonal subchannels due to hardware impairments or insufficient adaptation to the current channel conditions. A further source of error in TDD systems are the non-reciprocal transceivers inhibiting the baseband-to-baseband channel reciprocity required for accurate channel state acquisition based on the uplink channel estimate. In this paper, measurement results of a low-cost hardware-based calibration are presented and the drawbacks are discussed leading to the utilization of a recently introduced relative calibration. The latter is applied to an OFDM system and achieves or at least approximates the baseband-to-baseband reciprocity. Thus, it enables the link adaptation using the uplink channel state information. Furthermore, preliminary hardware implementations of the relative calibration running on a real-time system show accurate results. [ABSTRACT FROM AUTHOR]

This paper proposes a sub-harmonic injection-locked frequency synthesizer with frequency calibration scheme for millimeter-wave Time-division Duplexing (TDD) transceivers. The proposed synthesizer is capable of supporting all 60 GHz channels (58.1–65 GHz) including channel-bonding defined by 60 GHz wireless standards for short-range high-speed wireless communications. In order to guarantee a robust performance over process-voltage-temperature (PVT) variations of the conventional frequency synthesizer, a frequency calibration scheme is proposed to automatically correct a frequency drift of quadrature injection locked oscillators. Implemented by a 65 nm CMOS process, the frequency synthesizer achieves a typical phase noise of -117 dBc/Hz @ 10 MHz offset from a carrier frequency of 61.56 GHz while consuming 72 mW from a 1.2 V supply. The calibration system consumes 65 mW additionally. [ABSTRACT FROM PUBLISHER]

IEEE Software Editor in Chief Forrest Shull discuss the state of research in software engineering, focusing on empirical software engineering (ESE) and the expanded goal—question—metric strategies (GQM+Strategies) to tie specific measurements to the technical goals that they address. He also welcomes Girish Suryanarayana as the magazine's newest member of its Industry Advisory Board. [ABSTRACT FROM PUBLISHER]

This paper addresses the application of a new strategy in pulse wide modulation (PWM) technique called inverted-sine PWM (ISPWM). This technique can be used to control voltage source converters (VSC) in the light HVDC transmission systems. In this strategy, the proposed switching technique uses a sinusoidal reference signal and an inverted-sine as a carrier signal. The ISPWM technique generates lower voltage total harmonic distortion (THD) in comparison with conventional sinusoidal PWM (SPWM) technique. The new modulation technique has been studied on power transmission, THD of output voltage, TDD of current injected to load and utility network and the number of interharmonic components in output voltage and current injected from VSC to the utility network. A detailed study of the proposed modulation technique is carried out through MATLAB /SIMULINK. Simulation results show the effectiveness of the ISPWM technique to reducing of THD, TDD, interharmonic and increase the power transferred from VSC-HVDC to the power utility. [ABSTRACT FROM AUTHOR]

An advantage of time division duplex (TDD) wireless networks over frequency division duplex (FDD) is that the UL-DL switching point may be flexibly adapted to asymmetric traffic loads. This enables more efficient spectrum use, but on the other hand may lead to harmful cross-link interference between cells. As a result, the net gain (or loss) from flexible TDD depends on the traffic characteristics and network scenario. In this paper we address the problem in local area packet data networks, such as small- or femto-cell network, where high fluctuation in short term traffic loads is expected. We show through analysis and system level simulations that in such a scenario a significant gain in effective user throughput and packet delays may be achieved under low traffic loads. At high load the gain becomes smaller as packets accumulate in queues and there is both UL and DL traffic to transmit with high probability. When the UL and DL transmit powers are not balanced and switching point adaptation is applied the link direction with lower power may provide degraded performance. We show that introducing interference awareness at the scheduler provides more balanced performance and lowers the packet delays further. [ABSTRACT FROM AUTHOR]

This paper deals with the determination of downlink (DL) and uplink (UL) channel split ratio for time division duplex (TDD) based long term evolution (LTE) networks. In a TDD system, UL and DL transmissions are carried out at different time intervals, but share the same frequency band. The TDD framing in LTE is adaptive in the sense that the DL to UL bandwidth ratio may vary with time. This paper proposes an adaptive split ratio (ASR) scheme for LTE networks to automatically adjust the bandwidth ratio of DL to UL, according to the current traffic profile, wireless interference, and transport layer parameters. This provides the maximum aggregate throughput in LTE systems. The performance analysis shows that ASR scheme outperforms static allocation in terms of higher aggregate throughput and better adaptively to network dynamics. Further, it is also observed that the ASR scheme performs well for LTE, compared to worldwide interoperability for microwave access (WiMAX) system. [ABSTRACT FROM AUTHOR]

A software product is said to have high quality if it is having high customer satisfaction. The same is said to have lack of quality if it is not satisfying all the customer requirements. In conventional development methods series of life cycle activities are followed very strictly. Conventional methods are process oriented approaches. In conventional approaches, to deal with complex software products many quality measures and models like ISO, CMMI, SPICE, SIX SIGMA etc; are introduced. Agile development totally changed the way software is developed. Agile is a family of development methods also called as Lightweight Processes. Change can be introduced at any point of time by using agile methods. Pair programming and Test-Driven Development (TDD) are some of the key practices of agile development to achieve quality in software products. In Agile methods quality activities are done as part of the development not as a separate activity. The role of QA practices in agile projects needs to be redefined to achieve high quality. The method proposed is use of an extra layer of QA in agile development projects. The proposed approach is developer must not test his own written code, but in agile development most of the testing is done by developer that must be kept on minimum level in order to enhance quality. [ABSTRACT FROM AUTHOR]

Abstract: Test-Driven Development (TDD) is an extreme programming development method in which a software system is developed in short iterations. In this paper we present the Test-Driven Conceptual Modeling (TDCM) method, which is an application of TDD for conceptual modeling, and we show how to develop a conceptual schema using it. In TDCM, a system''s conceptual schema is incrementally obtained by performing three kinds of tasks: (1) Write a test the system should pass; (2) Change the schema to pass the test; and (3) Refactor the schema to improve its qualities. We also describe an integration approach of TDCM into a broad set of software development methodologies, including the Unified Process development methodology, the MDD-based approaches, the storytest-driven agile methods and the goal and scenario-oriented requirements engineering methods. We deal with schemas written in UML/OCL, but the TDCM method could be adapted to the development of schemas in other languages. [Copyright &y& Elsevier]

O'Connell MA, Donath S, Cameron FJ. Poor adherence to integral daily tasks limits the efficacy of CSII in youth. Introduction/Aims: Many young people experience improved glycemia with continuous subcutaneous insulin infusion (CSII) regimens; however, sustained glycemic benefit eludes a significant proportion. Our aims were to assess adherence to recommended CSII-related behaviors in a representative pediatric cohort and to identify potentially modifiable behaviors that impact on HbA1c in youth. Research Design and Methods: Data uploaded from insulin pump devices of 100 youth with type 1 diabetes were analyzed. Results: Ability to translate recommended behaviors into daily self-management varied widely in youth. Mean bolus frequency was 6.1/d; however, 69/100 entered <4 blood glucose levels (BGL)/d. HbA1c decreased by 0.2% for each additional BGL (p = 0.001) and bolus event (p < 0.001) per day. Prandial insulin omission was common and associated with significantly increased HbA1c. On average, if breakfast insulin was missed ≥4 times per fortnight, HbA1c increased 1.0% (p < 0.001). If one or more days per fortnight with ≤2 food boluses/d were recorded, then HbA1c increased 0.8% (p = 0.001). Increasing age and duration of CSII correlated with poorer adherence to recommended behaviors. Conclusions: Glycemic advantage obtained with CSII regimens is closely related to the manner in which CSII is employed. Poor adherence to integral CSII-related tasks is frequently encountered in adolescents and limits the efficacy of CSII in these youth. [ABSTRACT FROM AUTHOR]

As the migration from code division multiple access (CDMA) to orthogonal frequency-division multiple access (OFDMA) involves a technological revolution in physical layer, the high speed packet access (HSPA) evolution (HSPA+) has been proposed for a smooth migration. HSPA+ is an effort to further improve radio performance of HSPA, and wideband CDMA (WCDMA) HSPA+ and time division-synchronous CDMA (TD-SCDMA) HSPA+ (TD-HSPA+) are two HSPA+ systems evolving from WCDMA and TD-SCDMA, respectively. Different from WCDMA HSPA+ system, TD-HSPA+ system utilizes eight antennas at Node B and two antennas at user equipment (UE) for 8\, \times \,2 Multi-Input and Multi-Output (MIMO) transmission to achieve antenna array gain and diversity gain. Furthermore, to facilitate 8\, \times \,2 MIMO configuration, the antenna elements are partitioned into two groups for dual-polarization transmissions. This paper focuses on 8\, \times \,2 MIMO schemes in TD-HSPA+ systems, including the traditional single polarized MIMO (SP-MIMO), the separated and the joint singular value decomposition (SVD) based precoding dual-polarized MIMO (DP-MIMO) schemes. Performances of these TD-HSPA+ MIMO schemes are evaluated for both urban macro and micro scenarios. The simulation results show that the separated SVD based precoding DP-MIMO scheme performs better than the joint SVD based precoding DP-MIMO scheme, and the DP-MIMO scheme offers almost the same performance as the SP-MIMO due to the beamforming diversity gain and multiplex gain in TD-HSPA+ systems. [ABSTRACT FROM PUBLISHER]

Ying AK, Lairson DR, Giardino AP, Bondy ML, Zaheer I, Haymond MW, Heptulla RA. Predictors of direct costs of diabetes care in pediatric patients with type 1 diabetes. Objective: This study examines factors that predict elevated direct costs of pediatric patients with type 1 diabetes. Methods: A cohort of 784 children with type 1 diabetes at least 6 months postdiagnosis and managed by pediatric endocrinologists at Texas Children's Hospital were included in this study. Actual reimbursed costs from January 2004 to December 2005 were obtained. Medication and supply costs were based on estimates from insulin dosage and type of insulin regimen prescribed, respectively. We examined utilization of care, total diabetes-related direct medical costs, and predictors of direct costs and hospitalization. Results: Annually, 7% (58/784) of patients (excluding initial hospitalization at diagnosis) had a diabetes-related hospitalization and median length of stay was days. Mean total diabetes-related direct cost per person-year was $4730 [95% confidence interval (CI), 4516-4944]. Supplies accounted for 38% and medications 33% of costs, respectively. Older age, hemoglobin A (HbA) > 8.5%, use of a multi-injection or pump regimen, living in a non-married household, and female gender were associated with higher annual costs. HbA > 8.5%, living in a non-married household, and female gender increased the odds of a diabetes-related hospitalization. Discussion: Better metabolic control in patients with type 1 diabetes was associated with lower direct medical costs and lower odds of hospitalization. Marital status of the primary caregiver, irrespective of type of insurance, impacts the patient's healthcare costs and risk of hospitalization. This large single-center US study analyzes cost distribution in children with diabetes and is informative for payers and providers focused on effective management and improving healthcare costs. [ABSTRACT FROM AUTHOR]

Abstract: Wide band mesh or star oriented networks have recently become a subject of greater interest. Providing wideband multimedia access for a variety of applications has led to the inception of mesh networks. Classic access techniques such as FDMA and TDMA have been the norm for such networks. CDMA maximum transmitter power is much less than TDMA and FDMA counter parts, which is an important asset for mobile operation. In this paper we introduce a code division multiple access/time division duplex technique CDMA/TDD for such networks. The CDMA approach is an almost play and plug technology for wireless access, making it amenable for implementation by the mesh network service station, SS. Further it inherently allows mesh network service stations to use a combination of turbo coding and dynamic parallel orthogonal transmission to improve network efficiency. We outline briefly the new transmitter and receiver structures then evaluate the efficiency, delay and delay jitter. By analysis we show the advantages over classic counter parts with respect to the total network efficiency achievable especially for larger number of hops. [ABSTRACT FROM AUTHOR]

This paper proposes two space-frequency schemes with a multi-user pre-filtering technique for downlink (DL) multicarrier code division multiple access (MC-CDMA) systems. We consider the use of antenna arrays at the base station (BS) and a single antenna at the mobile terminal (MT) and derive the proposed multi-user pre-filtering technique that modulates the transmitted signal to eliminate the effects of multiple access interference (MAI) and channel distortions at the mobile terminals, while maintaining low MT complexity. Two types of detectors are considered at the MT: simple despreading and single user equalizers. The performances of the proposed schemes are compared to those of other transmit signal design approaches that have been recently proposed for DL MC-CDMA, considering both typical indoor and pedestrian scenarios, and channel coding based on UMTS specifications. [ABSTRACT FROM AUTHOR]

Multihop cellular networks (MCNs) enhance the capacity and coverage and alleviate the dead-spot and hot-spot problems of cellular networks. They also allow faster and cheaper deployment of cellular networks. A fundamental issue of these networks is packet delay because multihop relaying for signals is involved. An effective channel assignment is the key to reducing delay. In this paper, we propose an optimal and a heuristic channel assignment scheme, called OCA and minimum slot waiting first (MSWF), respectively, for a time division duplex (TDD) wideband code division multiple access (W-CDMA) MCN. OCA provides an optimal solution in minimizing packet delay and can be used as an unbiased or benchmark tool for comparison among different network conditions or networking schemes. However, OCA is computationally expensive and, thus, inefficient for large real-time channel assignment problem. In this case, MSWF is more appropriate. Simulation results show that MSWF achieves on average 95 percent of the delay performance of OCA and is effective in achieving high throughput and low packet delay in conditions of different cell sizes. [ABSTRACT FROM AUTHOR]

Most of the multimedia and Internet services today are asymmetric in nature and require high data rate support. Allocating equal band width in both uplink and downlink is not a prudent solution, as most of the time user requirements are either greater in uplink or downlink. The Multi Carrier Code Division Multiple Access (MC-CDMA) system with Time Division Duplex (TDD) mode can easily meet this requirement by dynamically declaring traffic direction in the TDD slot and adaptively allocating the sub channels. In this paper, we propose an adaptive slot and sub carrier allocation algorithm that can be independently implemented in each cell of a mobile communication network. Our analytical model is the generalization of two cell concept to represent a multi cell model. Based on the two cell concept, four cases of interference pattern have been considered and simulated separately in presence of Additive White Gaussian Noise (AWGN) and Rayleigh Channel. The simulated result suggests the requirement of approximately 9dB of Signal to Noise Ratio (SNR) to maintain Bit Error Rate (BER) below 10-3. We also analyze the average delay incurred by the proposed algorithm in allocating resources. [ABSTRACT FROM AUTHOR]

In this paper, we study the determination of down-link (DL) and uplink (UL) channel split ratio for Time Division Duplex (TDD)-based IEEE 802.16 (WiMAX) wireless networks. In a TDD system, uplink and downlink transmissions share the same frequency at different time intervals. The TDD framing in WiMAX is adaptive in the sense that the downlink to uplink bandwidth ratio may vary with time. In this work, we focus on TCP based traffic and explore the impact of improper bandwidth allocation to DL and UL channels on the performance of TCP. We then propose an Adaptive Split Ratio (ASR) scheme which adjusts the bandwidth ratio of DL to UL adaptively according to the current traffic profile, wireless interference, and transport layer parameters, so as to maximize the aggregate throughput of TCP based traffic. Our scheme can also cooperate with the Base Station (BS) scheduler to throttle the TCP source when acknowledgements (ACKs) are transmitted infrequently. The performance of the proposed ASR scheme is validated via ns-2 simulations. The results show that our scheme outperforms static allocation (such as the default value specified in the WiMAX standard and other possible settings in existing access networks) in terms of higher aggregate throughput and better adaptivity to network dynamics. [ABSTRACT FROM AUTHOR]

This paper introduces a new Typed Mind Map extension for a data model in a parse-tree-based online referee system with a TDD (Test-Driven Development) model and DALM (DICE adaptive learning model) model named DICE. Typed Mind Maps and a semantic node are defined by OWL-DL. Typed Mind Maps are now widely used in the DICE system as a uniform data model for the system, instructors, learners and materials. The Mind Maps are used for system configuration, system deployment, learner's information, organization of training materials, answer parsing and some widgets. An implementation based on this data model has been working for years in a real teaching and learning environment. [ABSTRACT FROM AUTHOR]

Cyclic delay diversity (CDD) is considered a simple approach to exploit the frequency diversity, to improve the system performance in orthogonal frequency division multiplexing (OFDM) systems. Also, the linear precoding technique can significantly improve the performance of communication systems by exploiting the channel state information (CSI). In order to achieve enhanced performance, we propose applying linear precoding to the conventional CDD-OFDM transmit diversity schemes over Rayleigh fading channels. The proposed scheme works effectively with the accurate CSI in time-division-duplex (TDD) OFDM systems with CDD, where the reciprocity is assumed instead of channel state feedback. For a BER of 10-4 and the mobility of 3 km/h, simulation results show that a gain of 6 dB is achieved by the proposed scheme over both flat fading and Pedestrian A (Ped A) channels, compared to the conventional CDD-OFDM system. On the other hand, for a mobility of 120 km/h, a gain of 2.7 dB and 3.8 dB is achieved in flat fading and Vehicular A (Veh A) channels, respectively. [ABSTRACT FROM AUTHOR]

Most research on scheduling problems focuses on increasing production efficiency. For instance, the shortest processing time (SPT) and earliest due date (EDD) dispatching rules perform well in minimizing mean flow time and reducing maximum tardiness, respectively. However, those indices ignore the financial impact (material cost and order price) on the factory. Previous studies focused mainly on cycle time and due date. However, the theory of constraint (TOC) considers not only the effect of time, but also financial factors. Therefore, TOC addresses the concepts of throughput-dollar-day (TDD) and inventory-dollar-day (IDD). The former index (TDD) represents penalties for tardy deliveries, while the latter index (IDD) refers to the material holding cost. Based on these two indices, this investigation creates a novel mixed TDD/IDD weighted value ( Z value) to replace the other traditional indices for taking measurements in various factories. This study also designs a heuristic dynamic scheduling algorithm (mixed TDD/IDD dispatching rule) for reducing the system Z value. Some traditional dispatching rules are compared with the proposed rule in terms of TDD, IDD, and Z value. Analytical results indicate that the mixed TDD/IDD dispatching rule is feasible and generally outperforms other conventional dispatching rules in terms of Z value under various factories. [ABSTRACT FROM AUTHOR]

Current uplink power control algorithm of code division multiple access (CDMA) time division duplex(TDD) system contains signal-to-interference-ratio(SIR) and interference measurement, which is based on history information. However, the adjustment of transmission power of one user equipment(UE) will affect SIR of the others, because the power control is done independently of the power adjustment of other UE’s. So the convergence speed of power control is not fast and the system performance degrades. In the proposed algorithm, all UE’s assigned in same time slot adjust their transmission power based on current information, which takes into account the adjustments of transmission power of all UE’s. The simulation results indicated that the proposed algorithm outperforms the old algorithm. [ABSTRACT FROM AUTHOR]

As RF and baseband engineers strive to satisfy the demand for ever higher data rates in next generation wireless systems, they are faced with three challenging requirements: both spectral efficiency and bandwidth have to be increased, and the cost per bit has to be kept low. A combination of MIMO, OFDM and TDD is a promising candidate technology to meet these objectives. However, realizing the potential gains of this approach requires tackling a number of new challenges: real MIMO channels, real-"Dirty"-RF and tough real-time constraints [ABSTRACT FROM PUBLISHER]

Abstract: Four different kinds of silicon materials (standard float zone—FZ, oxygen enriched FZ—DOFZ, Czochralski—Cz and thin epitaxial layers grown on Cz substrates—Epi/Cz) have been investigated in this work. They have been irradiated with 60Co-γ-radiation and 24GeV/c protons. The differences in the changes observed in the effective doping concentration (N eff) after proton irradiation of Cz and Epi silicon can be explained by the balance between the formation of two types of defects—a deep acceptor (the I center, referred to as Ip in this paper in order to avoid any confusion with interstitials) and a shallow donor (the bistable donor (BD) complex). While the formation of the I p center depends on the concentration of interstitial oxygen, the BD is generated in materials with high concentration of oxygen dimers. Following the generation of the IO2i defect—detected after low irradiation fluences only in Epi and Cz material—the average dimer concentration in 50μm Epi/Cz was estimated to be of only 2.7 times lower than in Cz diodes. A value of ∼2.7×10−12 cm2 for the electron capture cross-section of the Thermal Double Donors (TDDs), present in the Cz material, was also measured for the first time. The positive space charge introduced by ionization of the BD centers in Epi diodes was directly determined from TSC experiments for two irradiation fluences. The determined values show a linear fluence dependence for the formation of BD centers. By taking into account the BD and the Ip center generation as well as the donor removal, the change of the effective doping concentration N eff at 20°C in Epi/Cz and Cz diodes after an annealing time of 120min at 60°C can be explained up to a negative space charge introduction rate of ∼2.2×10−2 cm−1 thought to be determined by negatively charged clusters. Long-time annealing experiments at 80°C have shown that the generation of BDs represents a stable damage. [Copyright &y& Elsevier]