Influence of the packet size on the one-way delay on the down-link in 3G networks

The number of mobile broadband users is increasing. Furthermore, these users have high expectations into the capabilities of mobile broadband, comparable to those in fixed networks. On the other hand, the capacity assignment process on mobile access links is far from transparent to the user, and its properties need to be known in order to minimize the impact of the network on application performance. This paper investigates the impact of the packet size on the characteristics of the oneway delay for the down-link in third-generation mobile networks. For interactive and real-time applications such as VoIP, one-way delays are of major importance for user perception; however, they are challenging to measure due to their sensitivity to clock synchronization. Therefore, the paper applies a robust and innovative method to assure the quality of these measurements. We focus on the down-link as this is still the link that carries the most traffic to the user, and the quality of it will have a significant impact on all IP-based services. Results from measurements from several Swedish mobile operators reveal the possibility to partly control one-way delay and its variability by choosing appropriate packet sizes. In particular, packet sizes leading to the use of WCDMA entail significant but hardly varying one-way delays. On the other hand, we also show that HDSPA networks can deliver large amounts of data at rather high speed, but the cost is a huge variability in the one-way delay.