General Packet Radio Service System Research Articles

Deterministic process-based generative models for characterizing packet-level bursty error sequences

Errors encountered in digital wireless channels are not independent but rather form bursts or clusters. Error models aim to investigate the statistical properties of bursty error sequences at either packet level or bit level. Packet-level error models are crucial to the design and performance evaluation of high-layer wireless communication protocols. This paper proposes a general design procedure for a packet-level generative model based on a sampled deterministic process with a threshold detector and two parallel mappers. In order to assess the proposed method, target packet error sequences are derived by computer simulations of a coded enhanced general packet radio service system. The target error sequences are compared with the generated error sequences from the deterministic process-based generative model using some widely used burst error statistics, such as error-free run distribution, error-free burst distribution, error burst distribution, error cluster distribution, gap distribution, block error probability distribution, block burst probability distribution, packet error correlation function, normalized covariance function, gap correlation function, and multigap distribution. The deterministic process-based generative model is observed to outperform the widely used Markov models. Copyright © 2013 John Wiley & Sons, Ltd.

QoS Reliability in GPRS Systems

Wireless link quality is closely related to the received signal strength. Hence, transmit power control can be used to adjust the communication link quality to avoid asymmetric or weak links. This paper proposes a spatial radio resource model for quality of service (QoS) reliability in General Packet Radio Service (GPRS) networks. To model the propagation parameters, we adopt the empirical modeling approach by measuring signal outages at various base stations from a well established network, operating in Nigeria. We collect these data over a period of three months and apply the resultant data as parameters to the proposed model. We simulate the model under ideal conditions and evaluate the system’s performance as well as the power control tradeoff. A qualitative analysis using processed GIS maps, calls for effective power control in the system. Simulation results indicate that the existing system still requires further improvements to enhance its QoS reliability.

A Game-Theoretic Analysis of Link Adaptation in Cellular Radio Networks

Game theory is a promising approach for the system-level analysis of power control (PC) in wireless networks. This paper extends game-theoretic analysis to the study of link adaptation, which involves the variation of modulation parameters, in addition to PC. We use the link adaptation scheme in general packet radio service (GPRS) as an example, although the basic approach is applicable to any centralized wireless system with power and rate control. The action space of a player in our proposed game, which is called the link adaptation game (LAG), consists of power, as usual, and a discrete-valued adaptable link parameter (ALP), e.g., code rate. The utility function is a sigmoid (which is fitted to the throughput characteristics of a link adaptation scheme) priced by the square of power. We first show the existence of a Nash equilibrium (NE) in the game. Next, we propose a distributed algorithm to discover the NE. The algorithm is analytically shown to converge to an NE by treating it as a point-to-set map. Simulation results using the GPRS system demonstrate superior throughput and fair system-wide allocation of resources in comparison with other non game-theoretic methods.

Design and Analysis of a Mobility Gateway for GPRS–WLAN Integration

This paper presents the design and analysis of general packet radio service (GPRS)-wireless local area network (WLAN) mobility gateway (GWMG) for the integration of GPRS and WLANs. The interworking between GPRS and WLANs is achieved by the GWMG that resides on the border of GPRS and WLAN systems. The design goal is to minimize the modifications in GPRS and WLANs as both systems are already widely available. By deploying the GWMG, users can seamlessly roam among the two systems. Unlike other related work, the proposed GWMG could be used when either the GPRS or WLAN is a user's home network. Both mathematical analysis and simulation are developed to analyze the performance. The proposed GWMG has also been implemented in a testbed comprising a commercial GPRS system. The results show that the GWMG could achieve a design goal that will effectively integrate GPRS and WLANs.

GPRS system enhancement by employing LDPC codes

AbstractWe address the application and design of low‐density parity‐check (LDPC) codes to enhance the General Packet Radio Service (GPRS) system in order to support services such as the Multimedia Broadcast Multicast Service (MBMS). Advances in coding theory and further reduction in integrated circuit size have promoted LDPC codes to become one of the most attractive forward error correction (FEC) technologies in practice. The GPRS as well as enhanced GPRS (EGPRS) system currently uses the well‐known convolutional code (CC) as an FEC mechanism, and the Viterbi algorithm for decoding. With the recent introduction of MBMS, new applications that require more bandwidth and reliability are foreseen. It is known that the current (E)GPRS system does not perform well enough without further modifications, therefore, more efficient information distribution schemes need to be considered. To meet these increased requirements, especially for MBMS, we study the introduction of carefully designed LDPC codes at the physical layer. To exploit the full benefit of the superior performance of LDPC codes for large data block lengths, a modification in the GPRS protocol stack is proposed where larger RLC/MAC blocks are allowed, and its impact on the existing GPRS protocol stack is minimised. Copyright © 2007 John Wiley & Sons, Ltd.

Using Priority, Buffering, Threshold Control, and Reservation Techniques to Improve Channel-Allocation Schemes for the GPRS System

Taking a comprehensive approach, we investigate effects on the channel allocation for the general packet radio service (GPRS) system caused by priority strategy, buffering, threshold control on the buffer, and channel reservation. Moreover, four new dynamic channel-allocation schemes based on various combinations of these techniques are proposed and analyzed using the Markov chain approach. Analytical results obtained include blocking/forced-termination/dropping probabilities, cost-function definition based on the above metrics, and (mean) delay times. Through numerical examples, we demonstrate that: 1) priority and threshold control are efficient strategies to differentiate the quality of service (QoS) between a new voice call and a handoff voice call; 2) buffering allows more admitted rates of voice calls or data packets, but increases the delay time; and 3) channel reservation may directly improve a specific service, but it degrades performance of other services much. At last, better schemes suitable for the GPRS system are suggested after a thorough comparison of system performance.

Dynamic scheduling framework on an rlc/mac layer for general packet radio service

We present a traffic-scheduling framework that can dynamically allocate radio resources to a general packet radio service (GPRS) mobile station (MS) based on the interference levels of the radio links and the quality of service (QoS) specification of the MS. The underlying idea of this scheduling scheme is to preserve more bandwidth for use by those MSs that are within a low interference region so that the limited radio resources can be used more effectively. In this scheme, an MS uses a low transmission rate for data transfer when the MS is within a high interference region to avoid wasting bandwidth by transmitting data in a condition with high interference. In order to compensate for the service loss of the MS, we allocate more bandwidth to the MS when it is within a low interference region. In addition, we also propose an analytical model that can be used to derive the transmission rate for an MS in a low interference region based on the delay-bound requirement of the MS. The performance results show that our dynamic scheme can utilize the bandwidth more effectively to satisfy various QoS requirements of the MSs in the GPRS system without changing the convolution-coding rate.

Fluid-flow modelling of internet traffic in GSM/GPRS networks

In order to find an analytical solution for performance evaluation of Internet access over the General Packet Radio Service (GPRS), the packet-switched extension of the GSM mobile radio network, we evaluate the well-known Fluid-flow modelling (FFM) approach. Mobile Internet users are modeled by an ON/OFF source with exponentially distributed sojourn times in the ON and OFF state. We choose the IP datagram delay at the radio interface as quantity of interest. As Fluid-flow analysis only delivers the mean equilibrium buffer content, we present some additional methodology to calculate the sojourn time in the Fluid-flow model, taking specific characteristics of the GPRS into account. ON/OFF source parameters are determined representing the mean offered traffic in typical GPRS load scenarios by stochastic simulation, using the GPRS emulation system GPRSim. The GPRSim comprises load generators representing typical GPRS usage and a prototypical implementation of the GPRS protocols. Comparison of simulation results and analysis is performed using the same traffic source model for both simulation and analysis, eliminating approximation of WWW traffic characteristics as a reason for deviations between simulation results and analysis. Additionally analytical results are compared with results of the GPRSim using a detailed WWW model for traffic generation. The results illustrate the influence of accurate source modelling and the limitations of the FFM to model the GPRS system with elastic traffic. It is shown that the FFM is not able to depict the elastic property of TCP-based Internet traffic, but is capable of modelling the multiplexing of inelastic traffic like generated by streaming or real-time applications over the GPRS radio link in sufficient detail for performance estimations.

Performance of service disciplines in GPRS systems with heterogeneous traffic

Analysis is made of the behaviour of service disciplines with quality of service (QoS) for General Packet Radio Service (GPRS). Two scheduling algorithms, namely minimum laxity threshold (MLT) and modified earliest deadline (MED), are evaluated. The results show that MTL performs better than MED but with higher implementation complexity.

Quality of Service Management in GPRS-Based Radio Access Networks

In this article, the performance and capacity gain achievable with quality of service (QoS) management in packet switched radio networks based on the General Packet Radio Service (GPRS) are examined. Both the functions defined in the GPRS specification for QoS support and implementation-specific strategies for subscriber- and application-based Connection Admission Control (CAC) and scheduling are introduced. The feasibility of QoS provisioning in mobile core networks with use of DiffServ compared to present IP technology realizing a pure Best-effort service is examined in addition. To achieve this, simulation results of GPRS performance and system measures for different load situations are produced with the simulation tool GPRSim that models the realistic traffic behavior of a GPRS network.

Analysis of Snoop TCP protocol in GPRS system

The General Packet Radio Service system provides an easy adaptation to bursty traffic generated by Internet applications, e.g. e-mail, WWW and FTP. These applications use TCP as the transport protocol and therefore good interaction is necessary between the TCP and GPRS protocols. The performance of the Snoop TCP protocol in a GPRS network is analysed.

Understanding GPRS: the GSM packet radio service

The general packet radio service (GPRS), a data extension of the mobile telephony standard GSM is emerging as the first true packet-switched architecture to allow mobile subscribers to benefit from high-speed transmission rates and run data applications from their mobile terminals. A high-level description of the GPRS system is given with emphasis on services and architectural aspects.

General packet radio service in GSM

In the Global System for Mobile Communications (GSM) Phase 2+ development, one major activity is to specify the general packet radio service (GPRS). The standardization is expected to be completed at the end of 1997. The purpose of GPRSI like other packet data services, is to efficiently accommodate data sources that are bursty in nature. Another important goal of the technology is to make it possible for GSM license holders to share physical resources on a dynamic, flexible basis between packet data services and other GSM services. The authors present a detailed description of the GPRS system, emphasizing the radio link protocol, and demonstrate its performance. The performance measures have been obtained from the WINLAB GPRS simulator.