On the Performance of the AAA Systems in 3G Cellular Networks

This paper analyzes the performance of a system architecture for the authentication, authorization, and accounting (AAA), in a scenario where 3G users generate traffic and invoke signaling messages towards the AAA system. The AAA system performance, in terms of input arrival rate, retransmissions, timeouts, and number of proxy servers, is particularly critical in today's 3G networks due to the traditional separation of radio and IP engineering. Whereas the traffic generated by the wireless users is a known parameter to radio engineers, 3G operators lack practical methods for obtaining the corresponding parameters at the AAA side. This problem is even more complex for roaming scenarios where the AAA functions are configured in proxy server chains. To address these issues, we analyze an AAA system architecture based on the RADIUS protocol, which is currently the main AAA protocol adopted by the telecommunications industry. We present an analytical model for obtaining the RADIUS signaling rate, and verify it by simulations. We also analyze two typical application scenarios: 1xEV-DO and roaming. Based on the achieved results, we propose new and practical approaches to optimize the AAA system performance both in terms of signaling and normalized server load.