Abstract

Since wireless networks which can carry high bit rates have become ubiquitous, mobile computing is no longer just spoken about. Mobile computing always implies access through a wireless network to an IP network such as the Internet. In order to understand the performance of such links, we propose an analytic model for the down link delay of IP traffic between the Mobile Gateway Server and the End User in a UMTS mobile network. Traffic arriving at the Gateway Server is considered to be bursty in nature and we use a Batch Markovian Arrival Process (BMAP) to model this arrival process. We model the wireless link itself as a modified multi-state Gilbert–Elliot Markov model which takes into account the number of interfering users and whether the channel experiences Ricean fading or not for what we consider a typical indoor, IP-centric environment. We also account in both the analytical model and the simulation for the Forward Error Correction provided by Turbo coding in UMTS to establish realistic packet retransmission rates. Finally we calibrate and verify the correctness of the model with a discrete event simulator.

Keywords: Mobile computing; IP traffic; BMAP; WCDMA; Turbo coding; Ricean fading; BMAP/D/1 queue

Article Outline

1. Introduction

2. End-to-end model

3. Modeling the wireless link

3.1. Performance metrics

3.2. Hidden Markov model

3.3. User signal model

3.4. Interfering signal model

3.5. Turbo coding

4. Simulation

5. Model calibration

6. Model validation and results

7. Conclusion

References

Vitae