Shantidev Mohanty

NeXt generation/dynamic spectrum access/cognitive radio wireless networks: a survey

Todays wireless networks are characterized by a fixed spectrum assignment policy. However, a large portion of the assigned spectrum is used sporadically and geographical variations in the utilization of assigned spectrum ranges from 15% to 85% with a high variance in time. The limited available spectrum and the inefficiency in the spectrum usage necessitate a new communication paradigm to exploit the existing wireless spectrum opportunistically. This new networking paradigm is referred to as NeXt Generation (xG) Networks as well as Dynamic Spectrum Access (DSA) and cognitive radio networks. The term xG networks is used throughout the paper. The novel functionalities and current research challenges of the xG networks are explained in detail. More specifically, a brief overview of the cognitive radio technology is provided and the xG network architecture is introduced. Moreover, the xG network functions such as spectrum management, spectrum mobility and spectrum sharing are explained in detail. The influence of these functions on the performance of the upper layer protocols such as routing and transport are investigated and open research issues in these areas are also outlined. Finally, the cross-layer design challenges in xG networks are discussed.

A survey on spectrum management in cognitive radio networks

Cognitive radio networks will provide high bandwidth to mobile users via heterogeneous wireless architectures and dynamic spectrum access techniques. However, CR networks impose challenges due to the fluctuating nature of the available spectrum, as well as the diverse QoS requirements of various applications. Spectrum management functions can address these challenges for the realization of this new network paradigm. To provide a better understanding of CR networks, this article presents recent developments and open research issues in spectrum management in CR networks. More specifically, the discussion is focused on the development of CR networks that require no modification of existing networks. First, a brief overview of cognitive radio and the CR network architecture is provided. Then four main challenges of spectrum management are discussed: spectrum sensing, spectrum decision, spectrum sharing, and spectrum mobility.

A survey of mobility management in next-generation all-IP-based wireless systems

Next-generation wireless systems are envisioned to have an IP-based infrastructure with the support of heterogeneous access technologies. One of the research challenges for next generation all-IP-based wireless systems is the design of intelligent mobility management techniques that take advantage of IP-based technologies to achieve global roaming among various access technologies. Next-generation wireless systems call for the integration and interoperation of mobility management techniques in heterogeneous networks. In this article the current state of the art for mobility management in next-generation all-IP-based wireless systems is presented. The previously proposed solutions based on different layers are reviewed, and their qualitative comparisons are given. A new wireless network architecture for mobility management is introduced, and related open research issues are discussed in detail.

A Cross-Layer (Layer 2 + 3) Handoff Management Protocol for Next-Generation Wireless Systems

Next-generation wireless systems (NGWS) integrate different wireless networks, each of which is optimized for some specific services and coverage area to provide ubiquitous communications to the mobile users. It is an important and challenging issue to support seamless handoff management in this integrated architecture. The existing handoff management protocols are not sufficient to guarantee handoff support that is transparent to the applications in NGWS. In this work, a cross-layer (layer 2 + 3) handoff management protocol, CHMP, is developed to support seamless intra and intersystem handoff management in NGWS. Cross-layer handoff management protocol uses mobiles speed and handoff signaling delay information to enhance the handoff performance of mobile IP that is proposed to support mobility management in wireless IP networks. First, the handoff performance of mobile IP is analyzed with respect to its sensitivity to the link layer (layer 2) and network layer (layer 3) parameters. Then, a cross-layer handoff management architecture is developed using the insights learnt from the analysis. Based on this architecture, the detailed design of CHMP is carried out. Finally, extensive simulation experiments are carried out to evaluate the performance of CHMP. The theoretical analysis and simulation results show that CHMP significantly enhances the performance of both intra and intersystem handoffsNext-generation wireless systems (NGWS) integrate different wireless networks, each of which is optimized for some specific services and coverage area to provide ubiquitous communications to the mo...

A ubiquitous mobile communication architecture for next-generation heterogeneous wireless systems

Rapid progress in research and development of wireless networking and communication technologies have created different types of wireless systems (e.g., Bluetooth, IEEE 802.11, UMTS, and satellite networks). These systems are envisioned to coordinate with each other to provide ubiquitous high-data-rate services to mobile users. In this article, the architecture for ubiquitous mobile communications (AMC) is introduced that integrates these heterogeneous wireless systems. AMC eliminates the need for direct service level agreements among service providers by using a third party, a network interoperating agent. Instead of deploying a totally new infrastructure, AMC extends the existing infrastructure to integrate heterogeneous wireless systems. It uses IP as the interconnection protocol. By using IP as the gluing protocol, transparency to the heterogeneities of the individual systems is achieved in AMC. Third-party-based authentication and billing algorithms are designed for AMC. New mobility management protocols are also developed to support seamless roaming between different wireless systems.

Performance Analysis of Handoff Techniques Based on Mobile IP, TCP-Migrate, and SIP

Mobility management protocols operating from different layers of the classical protocol stack (e.g., link, network, transport, and application layers) have been proposed in the last several years. These protocols achieve different handoff performance for different types of applications. In this paper, mobile applications are grouped into five different classes, class A through class E, based on their mobility management requirements. Analytical models are developed to investigate the handoff performance of the existing mobility management protocols for these application classes. The analysis shows that applications of a particular class experience different handoff performance when different mobility management protocols are used. Handoff performance comparisons of different mobility management protocols are carried out to decide on the suitable mobility management protocol for a particular application class. The results of mathematical analysis advocate the use of transport layer mobility management for class B and class C applications, mobile IP for non-real-time class D and class E applications, and session initiation protocol-based mobility management for real-time class D and class E applications. Moreover, through analytical modeling, the parameters that influence the handoff performance of mobility management protocols are identified. These parameters can be used to design new application-adaptive techniques to enhance the handoff performance of the existing mobility management protocols.

VEPSD: a novel velocity estimation algorithm for next-generation wireless systems

A novel algorithm called velocity estimation using the power spectral density (VEPSD), which uses the Doppler spread in the received signal envelope to estimate the velocity of a mobile user (MU), is introduced in this paper. The Doppler spread is estimated using the slope of the power spectral density (PSD) of the received signal envelope. The performance of the VEPSD algorithm is evaluated in both Rayleigh and Rician fading environments. The sensitivity of the estimation error to additive white Gaussian noise (AWGN), Rice factor (K), and the angle of arrival of the line-of-sight (LOS) component is analyzed and compared with the level crossing rate (LCR) and covariance-based velocity estimators. Simulation results show that VEPSD estimates the velocity of MUs accurately. It is also shown that VEPSD can be used for velocity estimation under nonisotropic scattering and is well suited for next-generation wireless systems (NGWSs).

Runs based traffic estimator (RATE): a simple, memory efficient scheme for per-flow rate estimation

Per-flow network traffic measurements are needed for effective network traffic management, network performance assessment, and detection of anomalous network events such as incipient DoS attacks. Explicit measurement of per-flow traffic statistics is difficult in backbone networks because tracking the possibly hundreds of thousands of flows needs correspondingly large high-speed memories. To reduce the measurement overhead, many previous papers have proposed the use of random sampling and this is also used in commercial routers (Ciscos Net Flow). Our goal is to develop a new scheme that has very low memory requirements and has quick convergence to within a prespecified accuracy. We achieve this by use of a novel approach based on sampling two-runs to estimate per-flow traffic. (A flow has a two-run when two consecutive samples belong to the same flow). Sampling two-runs automatically biases the samples towards the larger flows thereby making the estimation of these sources more accurate. This biased sampling leads to significantly smaller memory requirement compared to random sampling schemes. The scheme is very simple to implement and performs extremely well

Advanced power management techniques in next-generation wireless networks [Topics in Wireless Communications]

Because mobile devices are equipped with a limited amount of battery power, it is essential to have efficient power management mechanisms in mobile broadband networks such as mobile WiMAX and 3GPP Long Term Evolution that enable always on connectivity. This article presents the state-of-the-art power management methods in next-generation wireless networks with a focus on IEEE 802.16m based next-generation WiMAX networks and 3GPP LTE. To minimize and optimize user equipment power consumption, and further to support various services and large amounts of data transmissions, advanced power conservation mechanisms are being developed in IEEE 802.16m and 3GPP. Two advanced power conservation mechanisms, sleep and idle modes, which are enhanced versions of the legacy IEEE 802.16 systems sleep and idle modes, were proposed and adopted in IEEE 802.16m. Similarly, 3GPP LTE adopts a discontinuous reception mechanism for power conservation in RRC_CONNECTED and RRC_IDLE states. Power management techniques in WiMAX and 3GPP LTE provide less control signaling and operational overhead while providing more efficient power saving, and use simpler operation procedures than the existing power management techniques.

Performance analysis of a novel architecture to integrate heterogeneous wireless systems

Current wireless world witnesses multiple heterogeneous systems such as Bluetooth, IEEE 802.11, UMTS, and satellite networks. These systems are envisioned to coordinate with each other to provide ubiquitous communications to mobile users. A novel architecture, Architecture for ubiquitous Mobile Communications (AMC), is introduced in this paper that integrates these heterogeneous wireless systems. AMC eliminates the need for direct Service Level Agreements (SLAs) among service providers by using a third party, Network Inter-operating Agent (NIA). Instead of developing a new architecture, AMC extends the existing infrastructure to integrate heterogeneous wireless systems. It uses IP as the inter-connection protocol to provide transparency to the heterogeneities of individual systems. Third-party-based authentication and billing algorithms are designed for AMC. New handoff management protocols are also designed to support seamless vertical handoffs between different wireless systems in AMC. Performance analysis is carried out to determine the latency associated with vertical handoffs and the load on the NIA that arises because of these vertical handoffs. Toward this, a network deployment scenario that consists of three types of wireless systems: WLAN, 3G, and satellite networks is considered. Moreover, the number of SLAs required in AMC is also determined for a given number of network operators. It is also shown that by using hierarchical structure, AMC can realize the integration of heterogeneous wireless systems around the globe.