Data transmission systems

The research proposed and elaborated in this dissertation is concerned with the development of new and smart techniques for subchannel allocation in the asymmetric digital subscriber lines (ADSLs). The ADSL refers to a class of access technology adopted currently in modern telecommunications to make use of the available channel capacity on the twisted copper-wires, which exist in the "last-mile" between the central office and subscribers. This available spectrum on the voice grade copper-lines is judiciously used to transport broadband data over the last mile regime. For this purpose, the channel capacity on the access lines is segmented in subchannels and the traffic to be transported is placed on the subchannels matching the bit-rates of the traffic to the subchannel capacity (as dictated by Hartley-Shannon law). The available subchannels for downstream and upstreams are of different extents (640 kbps for upstream and 9 Mbps for downstream); and, hence are qualified as asymmetric transports. Relevant to the subchannel allocation as above, the specific research, carried out can be enumerated as follows: (1) Development of a subchannel allocation metric (SAM) on the basis of information-theoretic considerations and duly accounting for noise/interference effects on the access lines and BER-based information-impairments on the trunks (feeding the access lines); (2) Use of SAM as an algorithmic support to train an artificial neural network (ANN), which is facilitated at the ADSL modem performing subchannel allocation. A new version of ANN training (and subchannel allocation prediction) strategies is developed by implementing the ANN operation in the entropy-plane. This technique allows a fast convergence of the ANN compatible for telecommunication transports. The incorporation of ANN in the modem renders the subchannel allocation smart; (3) Fuzzy considerations are also included in the ANN indicated above and operation of ADSL modem is then tuned to function as an intelligent neuro inference engine in its efforts towards subchannel allocation; (4) ATM support on ADSL lines is investigated and a scheme for allocating the permanent and switched virtual circuits (supporting ATM specified traffic) on the subchannels of access lines is developed. Relevant call-blocking probabilities are assessed; (5) Lastly, the EMI/RFI, and crosstalks on access lines are studied in the framework of practical considerations and mitigatory efforts are suggested thereof. Simulated results using data commensurate with practical aspects of ADSL transport are furnished and discussed. Background literature is comprehensively presented chapterwise and scope for future work is identified via open questions in the concluding chapter.

Multimedia applications incorporate the use of more than one type of media, i.e., voice, video, data, text and image. With the advances in high-speed communication, the ability to transmit multimedia is becoming widely available. One of the means of transport for multimedia in distributed networks is Broadband Integrated Services Digital Network (B-ISDN). B-ISDN supports the transport of large volumes of data with a low error rate. It also handles the burstiness of multimedia traffic by providing dynamic bandwidth allocation. When multimedia is requested for transport in a distributed network, different Quality of Service (QOS) may be required for each type of media. For example, video can withstand more errors than voice. In order to provide, the most efficient form of transfer, different QOS media are sent using different channels. By using different channels for transport, jitter can impose skews on the temporal relations between the media. Jitter is caused by errors and buffering delays. Since B-ISDN uses Asynchronous Transfer Mode (ATM) as its transfer mode, the jitter that is incurred can be assumed to be bounded if traffic management principles such as admission control and resource reservation are employed. Another network that can assume bounded buffering is the 16 Mbps token-ring LAN when the LAN Server (LS) Ultimedia(TM) software is applied over the OS/2 LAN Server(TM) (using OS/2(TM)). LS Ultimedia(TM) reserves critical resources such as disk, server processor, and network resources for multimedia use. In addition, it also enforces admission control(1). Since jitter is bounded on the networks chosen, buffers can be used to realign the temporal relations in the media. This dissertation presents a solution to this problem by proposing a Feedback-based Multimedia Synchronization Technique (FMST) to correct and compensate for the jitter that is incurred when media are received over high speed communication channels and played back in real time. FMST has been implemented at the session layer for the playback of the streams. A personal computer was used to perform their synchronized playback from a 16 Mbps token-ring and from a simulated B-ISDN network.

In the current communications age, the capabilities of mobile devices are increasing. The mobiles are capable of communicating at data rates of hundreds of mbps on 4G networks. This enables playback of rich multimedia content comparable to internet and television networks. However, mobile networks need to be spectrum-efficient to be affordable to users. Multimedia Broadcast Multicast Systems (MBMS) is a wireless broadcasting standard that is being drafted to enable multimedia broadcast while focusing on being spectrum-efficient. The hybrid video coding techniques facilitate low bitrate transmission, but result in dependencies across frames. With a mobile environment being error prone, no error correction technique can guarantee error free transmission. Such errors propagate, resulting in quality degradation. With numerous mobiles sharing the broadcast session, any error resilient scheme should account for heterogeneous device capabilities and channel conditions. The current research on wireless video broadcasting focuses on network based techniques such as FEC and retransmissions, which add bandwidth overhead. There is a need to design innovative error resilient techniques that make video codec robust with minimal bandwidth overhead. This Dissertation introduces novel techniques in the area of MBMS systems. First, robust video structures are proposed in Periodic Intra Frame based Prediction (PIFBP) and Periodic Anchor Frame based Prediction (PAFBP) schemes. In these schemes, the Intra frames or anchor frames serve as reference frames for prediction during GOP period. The intermediate frames are independent of others; any errors in such frames are not propagated, thereby resulting in error resilience. In prior art, intra block rate is adapted based on the channel characteristics for error resilience. This scheme has been generalized in multicasting to address a group of users sharing the same session. Average packet loss is used to determine the intra block rate. This improves performance of the overall group and strives for consistent performance. Also, the inherent diversity in the broadcasting session can be used for its advantage. With mobile devices capable of accessing a WLAN during broadcast, they form an adhoc network on a WLAN to recover lost packets. New error recovery schemes are proposed for error recovery and their performance comparison is presented.

This dissertation describes an architecture for a special purpose communications protocol processor (CPP) that has been developed for open systems interconnection (OSI) type layered protocol processing. There exists a performance problem with the implementation and processing of communication protocols and the problem can have an impact on the throughput of future network interfaces. This problem revolves around two issues, (i) communication processing bottlenecks to fully utilize high speed transmission mediums; (ii) mechanism used in the implementation of communications functions. It is the objective of this work to address this problem and develop a first of its kind processor that is dedicated to protocol processing. At first trends in computer communications technology are discussed along with issues that influence throughput in front end controllers for network interfaces that support OSI. Network interface requirements and a survey of existing technology are presented and the state of the art of layered communication is evaluated and specific parameters that contribute to the performance of communications processors are identified. Based on this evaluation a new set of instructions is developed to support the necessary functions. Each component of the new architecture is explained with respect to the mechanism for implementation. The CPP contains special-purpose circuits dedicated to quick performance (e.g. single machine cycle execution) of functions needed to process header and frame information, functions which are repeatedly encountered in all protocol layers, and instructions designed to take advantage of these circuits. The header processing functions include priority branch determination functions, register bit reshaping (rearranging) functions, and instruction address processing functions. Frame processing functions include CRC (cyclic redundancy check) computations, bit insertion/deletion operations and special character detection operations. Justifications for new techniques are provided and their advantages over existing technology are discussed. A hardware register transfer level model is developed to simulate the new architecture for path length computations. A performance queueing model is also developed to analyze the processor characteristics with various load parameters. Finally, a brief discussion indicates how such a processor would apply to future network interfaces along with possible trends.

Promoting healthcare and wellbeing requires the dedication of a multi-tiered health service delivery system, which is comprised of specialists, medical doctors and nurses. A holistic view to a patient care perspective involves emotional, mental and physical healthcare needs, in which caring is understood as the essence of nursing. Properly and efficiently capturing and managing nursing knowledge is essential to advocating health promotion and illness prevention. This thesis proposes a document-indexing framework for automating classification of nursing knowledge based on nursing theory and practice model. The documents defining the numerous categories in nursing care model are structured with the help of expert nurse practitioners and professionals. These documents are indexed and used as a benchmark for the process of automatic mapping of each expression in the assessment form of a patient to the corresponding category in the nursing theory model. As an illustration of the proposed methodology, a prototype application is developed using the Latent Semantic Indexing (LSI) technique. The prototype application is tested in a nursing practice environment to validate the accuracy of the proposed algorithm. The simulation results are also compared with an application using Lucene indexing technique that internally uses modified vector space model for indexing. The result comparison showed that the LSI strategy gives 87.5% accurate results compared to the Lucene indexing technique that gives 80% accuracy. Both indexing methods maintain 100% consistency in the results.