The 3GPP has raised the need to revisit the design of next generations of cellular networks in order to make them capable and efficient to provide M2M services. One of the key challenges that has been identified is the need to enhance the operation of the random access channel of LTE and LTE-A. The current mechanism to request access to the system is known to suffer from congestion and overloading in the presence of a huge number of devices. For this reason, different research groups around the globe are working towards the design of more efficient ways of managing the access to these networks in such circumstances. This paper aims to provide a survey of the alternatives that have been proposed over the last years to improve the operation of the random access channel of LTE and LTE-A. A comprehensive discussion of the different alternatives is provided, identifying strengths and weaknesses of each one of them, while drawing future trends to steer the efforts over the same shooting line. In addition, while existing literature has been focused on the performance in terms of delay, the energy efficiency of the access mechanism of LTE will play a key role in the deployment of M2M networks. For this reason, a comprehensive performance evaluation of the energy efficiency of the random access mechanism of LTE is provided in this paper. The aim of this computer-based simulation study is to set a baseline performance upon which new and more energy-efficient mechanisms can be designed in the near future.

Is the Random Access Channel of LTE and LTE-A Suitable for M2M Communications? A Survey of Alternatives

Machine-to-machine communication, a promising technology for the smart city concept, enables ubiquitous connectivity between one or more autonomous devices without or with minimal human interaction. M2M communication is the key technology to support data transfer among sensors and actuators to facilitate various smart city applications (e.g., smart metering, surveillance and security, infrastructure management, city automation, and eHealth). To support massive numbers of machine type communication (MTC) devices, one of the challenging issues is to provide an efficient way for multiple access in the network and to minimize network overload. In this article, we review the M2M communication techniques in Long Term Evolution- Advanced cellular networks and outline the major research issues. Also, we review the different random access overload control mechanisms to avoid congestion caused by random channel access of MTC devices. To this end, we propose a reinforcement learning-based eNB selection algorithm that allows the MTC devices to choose the eNBs (or base stations) to transmit packets in a self-organizing fashion.

Random access for machine-to-machine communication in LTE-advanced networks: issues and approaches

Increase in system capacity and data rates can be achieved efficiently in a wireless system by getting the transmitter and receiver closer to each other. Femtocells deployed in the macrocell significantly improve the indoor coverage and provide better user experience. The femtocell base station called as Femtocell Access Point (FAP) is fully user deployed and hence reduces the infrastructure, maintenance and operational cost of the operator while at the same time providing good Quality of Service (QoS) to the end user and high network capacity gains. However, the mass deployment of femtocell faces a number of challenges, among which interference management is of much importance, as the fundamental limits of capacity and achievable data rates mainly depends on the interference faced by the femtocell network. To cope with the technical challenges including interference management faced by the femtocells, researchers have suggested a variety of solutions. These solutions vary depending on the physical layer technology and the specific scenarios considered. Furthermore, the cognitive capabilities, as a functionality of femtocell have also been discussed in this survey. This article summarises the main concepts of femtocells that are covered in literature and the major challenges faced in its large scale deployment. The main challenge of interference management is discussed in detail with its types in femtocells and the solutions proposed over the years to manage interference have been summarised. In addition an overview of the current femtocell standardisation and the future research direction of femtocells have also been provided.

Interference Management in Femtocells

A method for intercepting calls from a remote or mobile device for customer self-support detects when users or subscribers dial one or more predetermined numbers. If the number corresponds to one of the predetermined numbers (such as a customer support number), the phone may intercept the call and display a list of potential solutions to the subscriber's problems. Various other features and embodiments art disclosed.

Call intercept methods, such as for customer self-support on a mobile device

Facilitating Cooperation for Wireless Systems Cooperative Communications: Hardware, Channel & PHY focuses on issues pertaining to the PHY layer of wireless communication networks, offering a rigorous taxonomy of this dispersed field, along with a range of application scenarios for cooperative and distributed schemes, demonstrating how these techniques can be employed. The authors discuss hardware, complexity and power consumption issues, which are vital for understanding what can be realized at the PHY layer, showing how wireless channel models differ from more traditional models, and highlighting the reliance of PHY algorithm performance on the underlying channel models. Numerous transparent and regenerative relaying protocols are described in detail for a variety of transparent and regenerative cooperative schemes. Key Features: Introduces background, concepts, applications, milestones and thorough taxonomy Identifies the potential in this emerging technology applied to e.g. LTE/WiMAX, WSN Discusses latest wireless channel models for transparent and regenerative protocols Addresses the fundamentals as well as latest emerging PHY protocols Introduces transparent distributed STBC, STTC, multiplexing and beamforming protocols Quantifies regenerative distributed space-time, channel and network coding protocols Explores system optimization, such as distributed power allocation and relay selection Introduces and compares analog and digital hardware architectures Quantifies complexity, memory and power consumption of 3G UMTS & 4G LTE/WiMAX relay Highlights future research challenges within the cooperative communications field This book is an invaluable guide for professionals and researchers in communications fields. It will also be of interest to graduates of communications and electronic engineering courses. It forms part of an entire series dedicated to cooperative wireless systems.

Cooperative Communications: Hardware, Channel and PHY

We propose a new blind multiuser signal model and detection framework for solving the near-far problem in synchronous CDMA in this paper. Compared with existing blind detectors, the proposed framework requires a minimum number of previously received signals, which is about the number of interfering users, and no sub-space separation or sequence estimation. Hence its computation complexity and detection delay are much reduced. Following this framework, several blind multiuser detectors are developed using least squares (LS) estimation, best least unbiased (BLU) estimation and minimum mean-square error (MMSE) estimation criteria and a recursively adaptive procedure is developed for further decreasing the complexity. All these can be easily extended for asynchronous CDMA. The near-far performance of this framework and the trade-off between the complexity and performance are discussed. Computer simulations are provided to demonstrate the performance of the proposed schemes too

Blind adaptive multiuser detection

Location Based Services for Mobiles :Technologies and Standards

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.

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

A method of transmitting and receiving data using superposition modulation in a wireless communication system having multiple antennas is disclosed. More specifically, the method comprises encoding the at least one inputted data stream by a channel coding scheme, puncturing the at least one inputted coded data stream into at least two sub-streams, layer-modulating the at least two sub-streams using layer-modulation schemes, transmitting the layered-modulated sub-streams via the multiple antennas, wherein transmission power of each antenna is based channel condition, and receiving by at least one user the layered-modulated sub-stream, wherein the each user uses different demodulation scheme.

A method of transmitting and receiving data using superposition modulation in a wireless communication system

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.

Byung K. Yi

Papers

Blind adaptive multiuser detection

Location Based Services for Mobiles :Technologies and Standards

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

A method of transmitting and receiving data using superposition modulation in a wireless communication system

On enhancing hierarchical modulation