Muthaiah Venkatachalam

System architecture and cross-layer optimization of video broadcast over WiMAX

Video broadcast and mobile TV have received significant interests from both academia and industry recently. The emerging mobile WiMAX (802.16e) is capable of providing high data rate and flexible quality of service (QoS) mechanisms, making the support of mobile TV very attractive. However, how to efficiently deliver video broadcast over WiMAX is not straightforward, especially in the multi-BS mode. The multi-BS mode requires multiple BSs to be synchronized in the transmission of common multicast/broadcast data. In this paper, we first identify the key design issues for video broadcast over WiMAX in the multi-BS mode. Then, we present an end-to-end solution which fully addresses key issues such as synchronization, energy efficiency and robust video quality. Moreover, we propose a methodology to optimize the coverage, the spectrum efficiency and the video quality. Results show that our proposed scheme can significantly improve the coverage and spectrum efficiency while satisfying video quality requirements.

alpha-Optimal User Association and Cell Load Balancing in Wireless Networks

In this paper we develop a framework for user association in infrastructure-based wireless networks, specifically focused on flow-level cell load balancing under spatially inhomogeneous traffic distributions. Our work encompasses several different user association policies: rate-optimal, throughput- optimal, delay-optimal, and load-equalizing, which we collectively denote α-optimal user association. We prove that the optimal load vector ρ∗ that minimizes a generalized system performance function is the fixed point of a certain mapping. Based on this mapping we propose and analyze an iterative distributed user association policy that adapts to spatial traffic loads and converges to a globally optimal allocation.

All-IP network architecture for mobile WiMAX

The mobile broadband wireless industry is in the midst of a significant transition in terms of capabilities and means of delivering multimedia IP services anytime, anywhere. This paper describes the network architecture for mobile WiMAX, a next-generation OFDMA-based broadband wireless technology developed and published by the IEEE as 802.16e-2005. The all-IP mobile network specification is being defined by the Network Working Group (NWG) in the WiMAX Forum. The adoption of all-IP functional architecture tenets and IETF-standardized protocols enables mobile WiMAX to deliver a wider selection of IP services while lowering capital and operational expenditures with a much faster time to market realization. This paper presents some of the inherent technical challenges and proposed solutions in developing the mobile WiMAX network architecture including support for both low-latency applications and non-real-time applications. We offer the details for some of the key functions realized in the network including handover and low-power idle mode operation. A sequel to this paper will address remaining key functions including network discovery and selection, radio resource management, QoS management and security that are integral to the initial network specification and more advanced IP services that will be supported in the next revision of the specification

Mobile relay and group mobility for 4G WiMAX networks

Relay is one of the key features being considered for IMT-Advanced systems. The relay architectures defined in IEEE 802.16m and 3GPP LTE-Advanced are optimized only for non-mobile relay, i.e., the Relay Station is attached to a designated Base Station and becomes a part of the fixed access network. A mobile relay architecture, where relay may switch attached BS according to operation demand, will promise more resilient relay deployment. In this paper, we first highlight three use cases where mobile relays can offer useful deployment options. Next, we propose an enhanced handover mechanism for relay-based group mobility by extending the IEEE 802.16m specification on relay. To this end, we describe the handover architecture for mobile relay highlighting the C-plane and U-plane enhancements required in order to support group mobility of mobile stations. Using illustration and comparisons, we show that mobile relay will offer significant benefits of signaling overhead reduction and provide users seamless mobility experience compared to fixed relays.

Distributed mobility management for efficient video delivery over all-IP mobile networks: Competing approaches

The recent proliferation of multimedia mobile devices and a variety of mobile applications are generating an enormous amount of data traffic over mobile networks. The key driver of the mobile traffic growth is mobile video. Currently, mobile networks are evolving to the 4G system, which has a flatter architecture and provides all-IP-based mobile broadband service. In all-IP mobile networks, IP mobility management is a key function that allows mobile nodes to continue their communications even when their point of attachment to the IP network changes. Existing mobile networks employ a centralized mobility management scheme where all intelligence is concentrated in one end-point system, rather than being distributed through the internet. However, this cannot satisfactorily support mobile videos, which demand a large volume of data and often require QoS such as session continuity and low delay. This motivates distributed mobility management (DMM) solutions that can efficiently handle mobile video traffic. In this article, we survey different approaches for DMM in standards development organizations such as IETF and 3GPP, and also in research organizations. We focus on three different DMM approaches that are currently being considered by the IETF: PMIPv6-based, MIPv6-based, and routing-based DMMs. We provide a qualitative analysis to compare the three DMM approaches and discuss which DMM approaches are more suitable for efficient mobile video delivery.

Exploiting the MAC layer flexibility of WiMAX to systematically enhance TCP performance

TCP performance over wireless network has been extensively studied in the literature and many cross-layer optimization schemes are proposed. Nevertheless, new technologies such as WiMAX, based on IEEE 802.16, offer new dimensions for system optimization that limited research has explored. In this paper, we show that the flexible WiMAX MAC layer allows cross-layer optimization to be done at the fine granularity of each connection or each service class. We also highlight that in a WiMAX broadband wireless access network, aggregate system performance is more important than the performance of an individual application instance, particularly from a network operator point of view. To this end, we propose an asymmetric link adaptation strategy for TCP-based applications. Coupled with ARQ, the aggregate system performance is enhanced without significantly compromising the performance of individual TCP flow. In addition, we argue that schedulers should be designed specifically for different service classes. We propose a scheduler for TCP-based best-effort service class that achieves both good aggregate throughput and fairness. The proposed design concepts not only help to achieve a good end-to-end TCP performance along with enhanced spectral efficiency, but also open many possibilities for optimizing the performance of other applications with similar techniques in WiMAX

Location services in WiMax networks

Location-based services have become a requisite feature for most wireless networks. There are two primary use cases: newer applications such as navigation, tracking of assets and personnel, and Points of Interest lookup, and emergency services (e.g., E911), where the users location is reported to the public safety answering point from which emergency responders are dispatched. Within this space of applications, location accuracies ranging from less than 5 m to hundreds of meters may be acceptable, depending on the specific use case. This article presents the end-to-end framework for location-based services in WiMAX technology, including both the mobile managed location approach with minimal network support as well as different network managed location solutions with assistance from mobile stations.

Adaptive Polling Service for Next-Generation IEEE 802.16 WiMAX Networks

WiMAX technology, based on IEEE 802.16 standard, is a promising broadband wireless technology for future 4G network. WiMAX provides radio access with centralized control, where bandwidth resources are managed and allocated by base station (BS) for both uplink (UL) and downlink (DL). Current WiMAX standard defines several bandwidth request (BWReq) mechanisms to serve a variety of applications, which however may not be efficient for on-off bursty traffic patterns. In this paper, we propose a novel adaptive polling service (aPS), with the advantage of significantly reducing the signaling overhead associated with the bandwidth request process without compromising the delay performance of real-time applications. Extensive simulations demonstrate that aPS outperforms existing scheduling services in terms of overall efficiency for a wide range of applications.

Advanced Mechanisms for Sleep Mode Optimization of VoIP Traffic over IEEE 802.16m

Since mobile devices are equipped with limited battery power, it is essential to have efficient power management mechanisms in mobile broadband networks such as mobile WiMAX that enable always on connectivity and provide high throughputs. In recent times Voice over IP (VoIP) has emerged as an important and dominant application in broadband mobile networks such as WiMAX. VoIP traffic is uniquely characterized by small packets sent regularly at periodic intervals and are bound by strict latency requirements for satisfactory user experience. This paper presents novel mechanisms to achieve enhanced power saving during a VoIP session by exploiting unique characteristics of VoIP traffic in next generation mobile WiMAX networks based on IEEE 802.16m standard. The analytical model and simulation results indicate that proposed methods reduce the average power consumption during a VoIP call by up to 70% compared to the existing IEEE 802.16m draft specifications. Moreover, the simulation results closely match our proposed analytical model.

Implementing Voice over AAL2 on a Network Processor

Publisher Summary The flexibility and programmability of next-generation network-processing units (NPU) make them a key component of next-generation telecommunications equipment. NPUs can support a variety of packet-processing applications, with a variety of different requirements. This chapter discusses the special requirements and challenges presented by the Voice over AAL2 (VoAAL2) application. The architecture and design of a VoAAL2 application developed for the Intel IXP2400 processor is described, and the features of an NPU that are required to support this type of application are discussed. With strict quality of service requirements and asynchronous inputs, VoAAL2 can be performed on an NPU. The application is most naturally implemented using an asynchronous programming model. It is found that the IXP2400 naturally supports such a programming model. Support for asynchronous components that span microengines can be improved by adding support for a distributed lock manager.