Byung K. Yi

Throughput comparison of random access methods for M2M service over LTE networks

It is one of the key issues in the 4-th generation (4G) cellular networks how to efficiently handle the heavy random access (RA) load caused by newly accommodating the huge population of Machine-to-Machine or Machine-Type Communication (M2M or MTC) customers/devices. We consider two major candidate methods for RA preamble allocation and management, which are under consideration for possible adoption in Long Term Evolution (LTE)-Advanced. One method, Method 1, is to completely split the set of available RA preambles into two disjoint subsets: one is for human-to-human (H2H) customers and the other for M2M customers/devices. The other method, Method 2, is also to split the set into two subsets: one is for H2H customers only whereas the other is for both H2H and M2M customers. We model and analyze the throughput performance of two methods. Our results demonstrate that there is a boundary of RA load below which Method 2 performs slightly better than Method 1 but above which Method 2 degrades throughput to a large extent. Our modeling and analysis can be utilized as a guideline to design the RA preamble resource management method.

On enhancing hierarchical modulation

Hierarchical modulation offers an important coverage/throughput tradeoff for wireless communication, however it has received relatively little attention to date. Regular hierarchical modulation suffers from the interference between layers. It results in both achievable capacity decrease and bit- error rate increase. In this paper, an enhanced hierarchical modulation technique along with three optimization schemes, in which the enhancement-layer signal constellation is rotated, are presented and analyzed. The first optimization scheme is proposed to maximize the achievable spectral efficiency with rotating the enhancement-layer signal constellation. The second scheme is proposed to lower the demodulation symbol-error rate with maximizing the modulation efficiency and asymptotic modulation efficiency. The parameters, modulation efficiency and asymptotic modulation efficiency, are formulated for quantizing inter-layer interference. The last one is proposed to maximize RF power amplifier efficiency with reducing the peak-to-average- power ratio of modulated symbols. This perspective is especially important for multi-carrier communications. All proposed schemes are simple and efficient. They can help recover the performance loss of regular hierarchical modulation due to inter-layer interference with little complexity increase. Computer simulations are provided to support our conclusions.

User interfaces for mobile content

The UI must be designed to facilitate the widespread and increased use of mobile content. Current UI approaches in the computing domain - such as windows, icons, menus, and pointing (WIMP) - are inadequate and inappropriate for mobile applications. Mobile device constraints pose several UI design challenges. UIs for emerging mobile devices consist of hardware and software combinations such as additional buttons for text input and special functional keys, touch-sensitive screens, audio/visual interfaces, and haptic interfaces to provide virtual-reality (VR) experiences. Analysts expect that third-generation mobile phones and beyond will be conduits for enormous amounts of multimedia content. Several major issues along a variety of dimensions must be addressed in the design and provision of content to these mobile devices. Because they are crucial for enhancing the user experience and enabling the effective consumption of mobile content, UIs are therefore among the major issues that need further study and work.

Enhancing the User Experience in Mobile Phones

To remain competitive, mobile-device vendors, developers, and network operators must provide end users with a rich and satisfying experience.

LTE Part I: Core network

Part I of this Feature Topic covers several key aspects of the evolved packet system (EPS) architecture.

Utility model for on-demand digital content

Rapid and converging technological advances in computing, communications, and consumer electronics have caused an explosion in the generation, processing, storage, transmission, and consumption of enormous amounts of digital content. Analysts expect these trends to accelerate in the near future and to have profound effects on content delivery and consumption. The term content generally refers to movies, songs, news, or educational material that spans various application domains, including personal entertainment, business, and education and training. The technology model currently used to supply this content seems inefficient and ineffective today. Newer models must be developed to support the ubiquitous, transparent, and cost-effective on-demand delivery of digital content, as driven by user preferences. We propose a content-utility system model for digital content delivery and consumption that resembles traditional utilities such as electrical power and water supply systems.

LTE part II: Radio access

Part II of this Feature Topic provides insight into the inner workings of the long term evolution (LTE) air interface.Part II of this Feature Topic provides insight into the inner workings of the long term evolution (LTE) air interface.

On MIMO Relay with Finite-Rate Feedback and Imperfect Channel Estimation

We investigate how finite-rate feedback and imperfect channel estimation impact MIMO relay network throughput and design in this paper. We start from multi-antenna transceiver with random beamforming and formulate the SNR and capacity loss due to channel estimation and quantization errors. We thereafter extend the analysis to multi-antenna relay network with multiple MIMO relay hops and discuss how the end-to-end throughput is scaled by MIMO pilot size, codebook size, relay network size and inter-beam interference. Some tradeoffs for MIMO relay network design are revealed. Computer simulations are provided to demonstrate our results.

3G wireless and cdma2000 1/spl times/ evolution in Korea

The cdma2000/spl reg/ I/spl times/EV-DV system is designed to meet the ever-increasing demand for high-speed packet data transmission while providing the same level of revenue generated by conventional voice communications on existing cdma2000 1/spl times/ systems. It supports concurrent voice and high-speed data on a single cdma 1.25 MHz carrier, and offers improved flexibility for operators to manage data and voice services cost efficiently. However, the Korean market has proved that providing higher bandwidth to the user does not guarantee the success of mobile data service. Users tend not to use expensive mobile wireless data services such as video streaming, video on demand, and MP3 music download service that they feel do not provide enough justification for their costs. The problem LG Telecom faces now as a mobile operator is not only to evolve technologies that enable various services, but also to find a way to provide attractive services at reasonable prices. This article describes experiences in the wireless data market in Korea as well as the market needs and driving forces for cdma2000 1/spl times/EV-DV developments.

Packet-level scheduling for implant communications using forward error correction in an erasure correction mode for reliable u-healthcare service

In u-healthcare services based on wireless body sensor networks, reliable connection is very important as many types of information, including vital signals, are transmitted through the networks. The transmit power requirements are very stringent in the case of in-body networks for implant communication. Further- more, the wireless link in an in-body environment has a high degree of path loss (e.g., the path loss exponent is around 6.2 for deep tissue). Because of such inherently bad settings of the communication nodes, a multi-hop network topology is preferred in order to meet the transmit power requirements and to increase the battery lifetime of sensor nodes. This will ensure that the live body of a patient receiving the healthcare service has a reduced level of specific absorption ratio (SAR) when exposed to long-lasting radiation. We propose an efficient method for delivering delay-intolerant data packets over multiple hops. We consider forward error correction (FEC) in an erasure correction mode and develop a mathematical formulation for packet-level scheduling of delay-intolerant FEC packets over multiple hops. The proposed method can be used as a simple guideline for applications to setting up a topology for a medical body sensor network of each individual patient, which is connected to a remote server for u-healthcare service applications.