Packet Data Services Research Articles

EV-do revision C: Evolution of the cdma2000* data optimized system to higher spectral efficiencies and enhanced services

Wireless packet data services are poised to be a major growth area, as wireless voice services have reached a fair level of maturity. An effort by the 3rd Generation Partnership Project 2 (3GPP2) standards body to continue to develop the successful data-optimized 1x EV-DO high rate packet data (HRPD) 3G system is under way. Alcatel-Lucent along with partners is proposing several novel techniques beyond the state of the art. Some of the key technologies are orthogonal frequency code division multiple access (OFCDMA), multi-carrier as well as wideband transmission, both frequency division duplex (FDD) and time division duplex (TDD) modes, multiple antenna techniques such as space division multiple access (SDMA) and multiple input multiple output (MIMO), interference mitigation techniques, and frequency domain interference cancellation. These are described in detail along with the resulting benefits. The design goals are to provide flexibility, backward compatibility (both loose and strict), a boost in the spectral efficiency and peak rates, a reduction in latency for real-time services, and a reduction in complexity in the base stations (BS) and mobile stations (MS). In this paper, we describe the underlying design philosophy and the associated technologies of 1x EV-DO Revision C with a focus on Alcatel-Lucent's contribution and provide associated performance results. The standard is expected to be completed in 2Q 2007. © 2007 Alcatel-Lucent.

TEDS: A high speed digital mobile communication air interface for professional users

The TETRA enhanced data service (TEDS) standard has been developed within the Technical Committee TETRA of the European Telecommunications Standards Institute as a major upgrade to the existing narrow-band ETSI TETRA system to supply professional users with high-speed IP packet data services over wireless mobile channels. Multicarrier-based modulation format, powerful payload and header encoding and link adaptation methods are among techniques employed for this purpose. The above enhancements are efficiently combined with improved higher layer protocols enabling a number of new services such as multiple multimedia access with QoS re-negotiation during the session, various priority mechanisms, provision of scheduled access for delay-sensitive applications and support for sectored antenna usage. The aim of this paper is to give a comprehensive overview of the TEDS features with particular emphasis on the physical layer and medium access control features together with representative link and system performance results

TraX: a device-centric middleware framework for location-based services

Location-based services turned out not to be the big thing following the success stories of GSM and SMS. The reasons for this are manifold and range from inaccurate cellular positioning technologies to a lack of competition in this field, both being closely related to the fact that positioning is controlled by a network-centric approach where the mobile network operator has the unique selling point for making position data available to third parties. However, things change: small, low-cost GPS receivers, either attachable to mobile devices or even integrated, are enjoying great popularity since their recent inception and are expected to become a standard feature of cell phones in the near future. In conjunction with mobile packet data services, they provide a basis for device-centric LBS platforms, where position data can be obtained directly from the mobile device. In this article the device-centric LBS middleware TraX, which focuses particularly on position management, advanced functions for interrelating the position data of several targets, and privacy protection, is presented. Due to its generic and open design, TraX can be reused for a broad range of different LBSs and thus fosters service diversity and multiprovider environments, both of which are essential for making the next generation of LBSs a success

Development and Comparison Between Resource Allocation Strategies Based on Intelligent Scheme and Traditional Distributed Dynamic Resource Allocation Strategies in Mobile Communication Networks

The third generation of mobile communication aims to transmit not only voice and text but also videos and multimedia data. Furthermore, in the future it is expected to involve web browsing, file transfer, and database access. This requires wireless cellular networks to efficiently support packet data traffic. Therefore, challenge in the design of wireless networks is to support both voice and packet data service of traffic with different QoS-parameters. On the other hand one aspect of this challenge is to develop an efficient scheme for assigning resources to new arriving calls or handoff of different traffic types. Since the blocking probability is one of the most important QoS- parameters, the QoS of wireless cellular networks are often measured in terms of two probabilities, the first is the new call blocking probability that a new call cannot be satisfied because of the unavailability of a proper free channel, and the second is the handoff blocking probability that a proper free channel is not available when a mobile station (MS) wants to move into a neighboring cell. To meet this aspect of the challenge, this proposal proposes a new assignment scheme based on intelligent methodologies to utilize frequency spectrum efficiently and to reduce call blocking probabilities.

Coordinated load balancing, handoff/cell-site selection, and scheduling in multi-cell packet data systems

We investigate a wireless system of multiple cells, each having a downlink shared channel in support of high-speed packet data services. In practice, such a system consists of hierarchically organized entities including a central server, Base Stations (BSs), and Mobile Stations (MSs). Our goal is to improve global resource utilization and reduce regional congestion given asymmetric arrivals and departures of mobile users, a goal requiring load balancing among multiple cells. For this purpose, we propose a scalable cross-layer framework to coordinate packet-level scheduling, call-level cell-site selection and handoff, and system-level cell coverage based on load, throughput, and channel measurements. In this framework, an opportunistic scheduling algorithm--the weighted Alpha-Rule--exploits the gain of multiuser diversity in each cell independently, trading aggregate (mean) down-link throughput for fairness and minimum rate guarantees among MSs. Each MS adapts to its channel dynamics and the load fluctuations in neighboring cells, in accordance with MSs' mobility or their arrival and departure, by initiating load-aware handoff and cell-site selection. The central server adjusts schedulers of all cells to coordinate their coverage by prompting cell breathing or distributed MS handoffs. Across the whole system, BSs and MSs constantly monitor their load, throughput, or channel quality in order to facilitate the overall system coordination. Our specific contributions in such a framework are highlighted by the minimum-rate guaranteed weighted Alpha-Rule scheduling, the load-aware MS handoff/cell-site selection, and the Media Access Control (MAC)-layer cell breathing. Our evaluations show that the proposed framework can improve global resource utilization and load balancing, resulting in a smaller blocking rate of MS arrivals without extra resources while the aggregate throughput remains roughly the same or improved at the hot-spots. Our simulation tests also show that the coordinated system is robust to dynamic load fluctuations and is scalable to both the system dimension and the size of MS population.

Quality of Service provisioning for UMTS network users with immediate and advance radio resource reservations

Wideband code division multiple access (WCDMA) is selected as the air interface scheme for 3G wireless networks. This scheme offers a high data rate that makes the wireless networks a suitable environment for real-time packet data services. 3G networks can be used to deliver multimedia traffic with guaranteed quality of service, but faces the scalability challenge in terms of the number of connections that can be setup in the cellular network. The more connections take place in WCDMA based network, the more interference is created, which yields more QoS degradation. To handle this issue, several algorithms that are collectively alleviate the QoS degradation have been developed and implemented. In this paper, we provide a system link simulator that models the WCDMA cellular network with the necessary radio resource management algorithms. The downlink direction has been simulated as it is usually the limiting link in setting up multimedia sessions, and interactive web sessions. The simulation environment provides, through the implementation of new wrap-around technique, a fair source of intra-cell and inter-cell interference, and avoids session disconnections due to the limited simulation area. Then, we suggest an admission control algorithm for admitting immediate and advance radio resource reservation requests. The admission control algorithm decision is based on the amount of interference that the new request will add to the network. The algorithm relies on the radio resource reservation states that stores all admitted immediate and advance sessions.

A DVB/Inmarsat hybrid architecture for asymmetrical broadband mobile satellite services

AbstractIn order to bridge the gap, both regulatory and technologically, between offering mobile satellite services at L‐band today and broadband mobile services at C‐band, Ku‐band or Ka‐band in the future, a short‐term solution is foreseen. Therefore, a DVB/Inmarsat hybrid service offering bi‐directional asymmetrical satellite connectivity, with a broadband receive channel at Ku‐band based on DVB‐S, and with a transmit channel at L‐band based on Inmarsat Mobile Packet Data Service, has successfully been developed, implemented and tested. The article focuses on the rationale for, and a technical solution, and how this can be evolved to support use of Inmarsat Broadband Global Area Access as transmit channel at L‐band. There are no regulatory issues associated with global operation of such a system, and the users can access the services using cost‐efficient off‐the‐shelf equipment, since the well established Inmarsat and DVB standards are utilized. The system has proved its feasibility to offer services like Internet access, email access, fast file transfers, and IP streaming of audio and video, in addition to the traditional Inmarsat services. Copyright © 2006 John Wiley & Sons, Ltd.

Physical-layer design for next-generation cellular wireless systems

The conventional cellular architecture will remain an integral part of next-generation wireless systems, providing high-speed packet data services directly to mobile users and also backhaul service for local area networks. In this paper, we present several proposals addressing the challenges associated with the critical design issues for the next-generation cellular wireless physical layer. These proposals include an orthogonal frequency division multiplexed (OFDM) or multicarrier code division multiple access (MC-CDMA) air interface for wide channel bandwidths, considerations for resource allocation, multiple antenna techniques, a hybrid duplexing technique combining the benefits of time division and frequency division duplexing, and coordinated networks for reducing intercell interference and increasing overall spectral efficiency.

A study on switching voice traffic seamlessly between GSM and GPRS cellular networks

As cellular carriers start deploying packet data services such as General Packet Radio Service (GPRS) and 3G cellular networks, packet-switched voice services such as VoIP will be available over the cellular network in the near future. When the existing circuit-switched radio interface and the newly deployed packet-switched radio interface coexist in a cell, the mobile station user may have an option between the circuit-switched call and the VoIP call. While the circuit-switched voice offers a better call quality, the VoIP connection offers a better radio resource utilization. In this paper, we introduce dynamic QoS control schemes for voice traffic, where Class-A GPRS mobile station users can switch their ongoing GSM calls to VoIP calls and vice versa seamlessly in the SIP-enabled GSM/GPRS cellular network based on their desired quality of service. Due to the VoIP's less radio resource demand, these schemes can also be used by the base station controller to handle the dynamically changing load in a cell.

A bandwidth-on-demand strategy for GPRS

General packet radio service (GPRS) is a global system for mobile communications (GSM) packet data service. In order to efficiently accommodate GPRS traffic while maintaining the desired service quality of GSM calls, we propose a GPRS bandwidth-allocation strategy called the bandwidth-on-demand (BoD) strategy. The BoD strategy is adaptive to the change of traffic conditions, and thus can dynamically adjust the number of channels for GSM and GPRS traffic. Taking the effect of packet dropping due to movements of mobile stations into account, this paper develops an analytical model to study the BoD performance in terms of GSM-call-blocking probability and GPRS-packet-dropping probability.

Comparative Radio Packet Scheduling Issues in cdma2000 1x and 1xEV Systems

Radio packet schedulers are currently being implemented in cdma2000 1x and 1xEV. cdma2000 1x stems from TIA/EIA-95 that was optimised to support circuit-based voice communications and is now extended to support high speed data transmission up to 153.6kbps. IxEV is primarily for wireless Internet access and can support up to maximally 2.4Mbps. Compared with other 3G mobile systems that focus on voice services and guaranteed quality of the services, 1xEV exploits the delay-tolerant transmission of the packet data services so as to achieve spectral efficiency and reduce the cost of providing such services. Supporting multimedia transfer including real-time as well as delay-tolerant data transmission, however, is a must in designing packet schedulers for future mobile systems. In this letter, we address design issues of a packet scheduler by comparing two existing different schedulers: WQDS (Weighted Queuing Rate Scheduler) for cdma2000 1x and PFRS (Proportional Fairness Rate Scheduler) for 1xEV. Comparisons are made on the structure of schedulers as well as by numerical evaluations of performance.

The wireless edge router: A network processor-based packet data serving node for a CDMA2000* network

A network processing unit (NPU) is increasingly becoming the processor of choice for building custom packet-processing gateways. In this paper, we present an NPU-based design and architecture for a packet data serving node (PDSN) in a CDMA2000∗ network. A PDSN is a packet-processing gateway that interfaces between the Internet and the wireless radio access network to provide packet data services to mobile users. We map the different functions of the PDSN onto the packet-processing engines and the core processor of an NPU. This involves a complete separation of the control plane, which is implemented in the core processor, and the data plane, which is implemented using a multistage packet pipeline mapped onto the packet-processing engines. We describe resource allocation schemes for packet buffering and processing and also a flexible communication method with the core processor. The mechanisms described in the paper are general enough to be used to implement other NPU-based packet-processing gateways. We also present a prototype implementation of the PDSN on an NPU and show its superiority to commercial products by means of measurement experiments.

Delay Analysis of Packet Scheduling with Multi-Users Diversity in Wireless CDMA Systems

There have been a number of studies that investigate efficient packet scheduling schemes to support quality of service of multiple real-time data users and to increase capacity of non-real-time users sharing a wireless channel. We consider the problem of scheduling transmissions of multiple data users sharing the same wireless channel so as to satisfy delay or throughput and present a general packet scheduling, called MBCS (Multi-users Best Channel Scheduling) which takes advantage of the multi-user diversity of a mobile wireless system. In this paper, a queuing model that represents radio resource management for supporting packet data services is developed for the purpose of evaluating the performance of wireless CDMA systems. Numerical results show that delay performance of the proposed scheduler is higher than that of the Single-user Best Channel Scheduler (SBCS) depending on the time-varying channel status.

Rate Scheduling in Multiple Antenna Downlink Wireless Systems

We consider scheduling strategies for multiantenna and multibeam cellular wireless systems for high-speed packet data services on the downlink. We establish a fundamental connection between the stability region of the queuing system and the set of feasible transmission rates, which provides the basis for the scheduling algorithm proposed in this paper. Transmission using adaptive steerable beams and fixed sector beams are considered and average delay versus throughput results are obtained through simulations for the proposed scheduling scheme in each case. While in single antenna systems multiuser diversity gains are achieved by the scheduling algorithms that transmit to a single user in each scheduling interval, our results show that with multiple antennas, transmitting to a carefully chosen subset of users has superior performance. The multiantenna scheduling problem is closely related to the problem of coordinated scheduling for transmission through multiple base stations, where a user can receive signals from several base stations simultaneously. We consider the special case when three single-antenna base stations are allowed to cooperate and transmit to the users in the triangular region between the base stations and propose scheduling strategies that demonstrate significant gains.

Reverse high-speed packet data physical layer enhancements in cdma2000 1/spl times/EV-DV

The rapid growth of Internet-based applications calls for design of a high-speed wireless packet data communication system. This anticipated increase in future mobile wireless packet data services has challenged the current 3G standardization bodies to respond with evolved 3G system specifications capable of providing increased data throughput. In response to such a need, 3GPP2 recently completed the enhanced reverse link standardization effort of the CDMA technology flagship, cdma2000/spl reg/ by completing the definition of the 1/spl times/EV-DV 1/spl times/ system. 1/spl times/EV-DV achieves higher data throughput while simultaneously providing coexisting and backward-compatible voice services within the same spectrum. This feature of 1/spl times/EV-DV allows wireless operators to manage the voice and data loading in their system more efficiently. This article describes the physical layer reverse link enhancements in cdma2000 revision D that are necessary to support 1/spl times/EV-DV.

Optimizing the ARQ performance in downlink packet data systems with scheduling

Third generation wireless systems typically employ adaptive coding and modulation, scheduling, and Hybrid Automatic Repeat reQuest (HARQ) techniques to provide high-speed packet data service on the downlink. Two main considerations in designing such a system are algorithms for the selection of coding and modulation schemes based on the channel quality of the link and algorithms for the selection of the user to whom a particular slot is assigned. We propose a systematic approach to optimize the mapping between signal-to-interference-and-noise ratio (SINR) and modulation and coding scheme (MCS) to maximize the throughput by taking into account the type of HARQ scheme employed. We also propose to incorporate frame error rate (FER) and retransmission information as a part of the scheduling decision. The proposed scheduler ranking methods based on using an effective rate rather than the instantaneous rate provide natural priority to retransmissions over new transmissions, and priority to users with better channel quality. Extensive simulation results comparing performance of the proposed methods to conventional methods are presented.

The new paradigm for wireless network optimization: a synergy of automated processes and human intervention

With the evolution of wireless technologies, the optimization process for the radio access network has undergone a dramatic increase in complexity. This trend is driven by the introduction of multiple objectives for packet data services, the increasing network heterogeneity resulting from technology overlays, and the growing demand for nondisruptive optimization of operating networks. In a multidisciplinary effort, Bell Laboratories has developed a new optimization methodology that tackles these challenges using automated processes. We show that the paradigm shift toward automation requires the development of several interdependent algorithms each designed to cope with a particular optimization task. In the application described, human intervention proves indispensable; it demands a new kind of expertise that combines understanding of the automated processes with knowledge of network operation. Through examples we illustrate the variety of tasks that have to be automated and where guidance is needed through human control. The development of these automated processes is an important step toward dynamic optimization routines that are integrated into the network and adjust the network in a real-time manner.

Link adaptation algorithm for improved wireless transmission of delay-sensitive packet data services

Link adaptation is a radio resource management technique that selects a transport mode based on the experienced channel conditions. The optimum mode is commonly determined so as to maximise the throughput. Although, this approach is suitable for best-effort services, it is not tailored for real-time services. Presented is a new link adaptation algorithm designed to improve the transmission of delay-sensitive services. The results demonstrate that significant improvements in terms of transmission delay, throughput and operation of link adaptation itself, can be obtained with the proposed scheme.

Predictive call admission control for multimedia streaming in CDMA cellular environments

Third-generation (3G) wireless networks based on code-division multiple access (CDMA) have been engineered to provide mobile users with voice as well as advanced packet data services. Support of Internet-based multimedia streaming services is considered a critical factor for future deployment of such networks. Provisioning streaming services in a dependable way, however, requires supporting data transmission at relatively high data rates while maintaining session quality during both intracell and intercell user movements. In this paper, an adaptive bandwidth allocation and admission control scheme is proposed for managing network resources for a streaming service. Streaming requests are assumed to be served by an adaptive server capable of choosing suitable video streaming parameters (e.g., video resolution, frame rate, and encoding parameters) in response to possible requests from the wireless network to vary the currently allocated bandwidth. The devised admission control scheme exploits a priori knowledge of user mobility patterns to minimize the risk of running into an overload condition after acceptance of a new multimedia streaming connection. The obtained simulation results show that, compared to a nonpredictive admission control scheme, the proposed scheme achieves a lower forced-termination probability and higher throughput, while consuming less base-station transmission energy.

Performance analysis of low earth orbit satellites for power system communication

In this paper the main performances of communication services based on low earth orbit satellites (LEOs) have been analyzed in order to evaluate their suitability for a typical set of power system monitoring functionalities. As an experimental test bed, an intelligent electronic device (IED) for remote monitoring and protection of power components equipped with a bi-directional communication system based on the LEO satellites of the Globalstar ® consortium has been prototyped. Thanks to the adoption of this facility the main parameters characterizing the performance of the satellite TCP/IP services have been evaluated. They comprise in particular the connection time, the degradation of service and data latency for both packet and asynchronous data services. The experimental results obtained show that the application of LEO satellites based communication technologies exhibits a set of intrinsic advantages that could be particularly useful in several fields of power system communication.