Raja Ali Riaz

Vertical Handover Necessity Estimation Based on a New Dwell Time Prediction Model for Minimizing Unnecessary Handovers to a WLAN Cell

In this work, we devise a vertical handover necessity estimation (HNE) method to minimize unnecessary handovers for a mobile node (MN) entering a WLAN cell. The method relies on a new model for prediction of dwell time and computation of certain threshold values. By comparing the predicted dwell time with those thresholds, a MN is able to make decision whether it should perform handover to a WLAN cell, while keeping the probability of handover failure and probability of unnecessary handover within bounds. Simulation results obtained from Monte-Carlo experiments prove validity of the proposed model. We also compare this model with existing models for minimizing unnecessary handovers. We further enhance the analytical model by incorporating the throughput gain in HNE and show that this can further optimize handover decision in heterogenous networks.

Distributed Self-Concatenated Coding for Cooperative Communication

In this paper, we propose a power-efficient distributed binary self-concatenated coding scheme using iterative decoding (DSECCC-ID) for cooperative communications. The DSECCC-ID scheme is designed with the aid of binary extrinsic information transfer (EXIT) charts. The source node transmits self-concatenated convolutional coded (SECCC) symbols to both the relay and destination nodes during the first transmission period. The relay performs SECCC-ID decoding, where it may or may not encounter decoding errors. It then reencodes the information bits using a recursive systematic convolutional (RSC) code during the second transmission period. The resultant symbols transmitted from the source and relay nodes can be viewed as the coded symbols of a three-component parallel concatenated encoder. At the destination node, three-component DSECCC-ID decoding is performed. The EXIT chart gives us an insight into operation of the distributed coding scheme, which enables us to significantly reduce the transmit power by about 3.3 dB in signal-to-noise ratio (SNR) terms, as compared with a noncooperative SECCC-ID scheme at a bit error rate (BER) of 10-5. Finally, the proposed system is capable of performing within about 1.5 dB from the two-hop relay-aided networks capacity at a BER of 10-5, even if there may be decoding errors at the relay.

Near-Capacity Iteratively Decoded Binary Self-Concatenated Code Design Using EXIT Charts

In this treatise extrinsic information transfer (EXIT) charts are used to design binary self-concatenated convolutional codes employing iterative decoding (SECCC-ID) for communicating over both uncorrelated Rayleigh fading and additive white Gaussian noise (AWGN) channels. Recursive Systematic Convolutional (RSC) codes are selected as constituent codes, an interleaver is used for randomising the extrinsic information exchange of the constituent codes, while a puncturer assists us in increasing the achievable bandwidth efficiency. At the receiver, self-iterative decoding is invoked for exchanging extrinsic information between the hypothetical decoder components. The convergence behaviour of the decoder is analysed with the aid of bit-based EXIT charts. Finally, we propose an attractive system configuration, which is capable of operating within about 1 dB of the information-theoretic limits.

Near-capacity iterative decoding of binary self-concatenated codes using soft decision demapping and 3-D EXIT charts

In this paper 3-D Extrinsic Information Transfer (EXIT) charts are used to design binary Self-Concatenated Convolutional Codes employing Iterative Decoding (SECCC-ID), exchanging extrinsic information with the soft-decision demapper to approach the channel capacity. Recursive Systematic Convolutional (RSC) codes are selected as constituent codes, an interleaver is used for randomising the extrinsic information exchange of the constituent codes, while a puncturer helps to increase the achievable bandwidth efficiency. The convergence behaviour of the decoder is analysed with the aid of bit-based 3-D EXIT charts, for accurately calculating the operating EbN0 threshold, especially when SP based soft demapper is employed. Finally, we propose an attractive system configuration, which is capable of operating within about 1 dB from the channel capacity.

A new method for handover triggering condition estimation

It is desirable to maximize the WLAN usage in integrated heterogeneous network environment due to its high speed access and low access cost. We have modeled under geometry and mobility effects to dynamically estimate the distance of a mobile terminal from the access point at which the handover must be triggered to keep probability of handover failure within desired bounds while maximizing the WLAN usage. Monte-Carlo simulations are provided and they are in good conformance with our analytical findings.

Convergence Analysis of Iteratively Detected Time Hopping and DS-CDMA Ultrawide Bandwidth Systems by EXIT Charts

This paper presents a novel analysis on the decoding convergence of Time Hopping (TH) and Direct Sequence (DS) Code-Division Multiple-Access (CDMA) Ultrawide Bandwidth (UWB) systems when communicating over multipath Nakagami channels. The analysis is based on the Extrinsic Information Transfer (EXIT) chart where the UWB systems are serially concatenated pulse-position modulated TH and code-synchronous DS-CDMA. It is shown from an EXIT chart analysis that the multipath diversity can yield a larger area under the EXIT curve of the inner detector. This area is related to the achievable rate of the system and it can be exploited with the aid of iterative detection. Simulation results of the iteratively detected TH and DS-CDMA UWB schemes verify the EXIT chart analysis.

Control Law Design for Propofol Infusion to Regulate Depth of Hypnosis: A Nonlinear Control Strategy

Maintaining the depth of hypnosis (DOH) during surgery is one of the major objectives of anesthesia infusion system. Continuous administration of Propofol infusion during surgical procedures is essential but increases the undue load of an anesthetist in operating room working in a multitasking setup. Manual and target controlled infusion (TCI) systems are not good at handling instabilities like blood pressure changes and heart rate variability arising due to interpatient variability. Patient safety, large interindividual variability, and less postoperative effects are the main factors to motivate automation in anesthesia. The idea of automated system for Propofol infusion excites the control engineers to come up with a more sophisticated and safe system that handles optimum delivery of drug during surgery and avoids postoperative effects. In contrast to most of the investigations with linear control strategies, the originality of this research work lies in employing a nonlinear control technique, backstepping, to track the desired hypnosis level of patients during surgery. This effort is envisioned to unleash the true capabilities of this nonlinear control technique for anesthesia systems used today in biomedical field. The working of the designed controller is studied on the real dataset of five patients undergoing surgery. The controller tracks the desired hypnosis level within the acceptable range for surgery.

Reduced bit low power VLSI architectures for motion estimation

Low power and real time very large scale integration (VLSI) architectures of motion estimation (ME) algorithms for mobile devices and applications are presented. The power reduction is achieved by devising a novel correction recovery mechanism based on algorithms which allow the use of reduced bit sum of absolute difference (RBSAD) metric for calculating matching error and conversion to full resolution sum of absolute difference (SAD) metric whenever necessary. Parallel and pipelined architectures for high throughput of full search ME corresponding to both the full resolution SAD and the generalized RBSAD algorithm are synthesized using Xilinx Synthesis Tools (XST), where the ME designs based on reduced bit (RB) algorithms demonstrate the reduction in power consumption up to 45% and/or the reduction in area up to 38%.

EXIT-Chart-Aided Three-Stage Concatenated Ultrawideband Time-Hopping Spread-Spectrum Impulse Radio Design

A serially concatenated and iteratively decoded irregular variable-length coding (IrVLC) scheme is amalgamated with a unity-rate precoded time-hopping (TH) pulse-position-modulation (PPM)-aided ultrawideband (UWB) spread-spectrum (SS) impulse radio design. The proposed design is capable of operating at low SNRs in Nakagami-m fading channels contaminated by partial band noise jamming (PBNJ) as a benefit of lossless IrVLC joint source and channel coding. Although this scheme may readily be used for lossless video or audio compression, for example, we only used it here for lossless near-capacity data transmission. A number of component variable-length-coding (VLC) codebooks having different coding rates are utilized by the IrVLC scheme for encoding specific fractions of the input source symbol stream. EXtrinsic Information Transfer (EXIT) charts are used to appropriately select these fractions to shape the inverted EXIT curve of the IrVLC and, hence, to match that of the inner decoder, which allows us to achieve an infinitesimally low bit error ratio (BER) at near-capacity SNR values.

A Review of Modern Control Strategies for Clinical Evaluation of Propofol Anesthesia Administration Employing Hypnosis Level Regulation

Regulating the depth of hypnosis during surgery is one of the major objectives of an anesthesia infusion system. Continuous administration of Propofol infusion during surgical procedures is essential but it unduly increases the load of an anesthetist working in a multitasking scenario in the operation theatre. Manual and target controlled infusion systems are not appropriate to handle instabilities like blood pressure and heart rate changes arising due to interpatient and intrapatient variability. Patient safety, large interindividual variability, and less postoperative effects are the main factors motivating automation in anesthesia administration. The idea of automated system for Propofol infusion excites control engineers to come up with more sophisticated systems that can handle optimum delivery of anesthetic drugs during surgery and avoid postoperative effects. A linear control technique is applied initially using three compartmental pharmacokinetic and pharmacodynamic models. Later on, sliding mode control and model predicative control achieve considerable results with nonlinear sigmoid model. Chattering and uncertainties are further improved by employing adaptive fuzzy control and H∞ control. The proposed sliding mode control scheme can easily handle the nonlinearities and achieve an optimum hypnosis level as compared to linear control schemes, hence preventing mishaps such as underdosing and overdosing of anesthesia.