Etienne F. Chaponniere

Effect of physical layer bandwidth variation on TCP performance in cdma2000

A cdma2000/spl trade/ end user can experience wide variations in the physical layer bandwidth allocated to him. This happens as a result of a high rate supplemental channel (SCH) being allocated and deallocated to the user in a bursty manner. This swing of physical layer rates can have an adverse effect on the end-end TCP operation, i.e., this rate variation can cause TCP timeouts and retransmissions even though no packet was lost on the physical layer. In this paper, we study this effect in detail. First, we propose a simple model for TCP over cdma2000. Using this model and subsequent analysis, we study the effects of different TCP parameters and different burst parameters (rate and duration) on the operation of TCP. We perform extensive lab tests to investigate how different TCP parameters and physical layer data rates affect the TCP throughput. Although the studies are done for a cdma2000 system, the results and conclusions hold in general for any system running TCP over a physical layer with varying bandwidth.

Impact of TCP and RLP parameters on cdma2000 performance

The packet data user experience achieved by cdma2000/spl trade/ is influenced by the interaction of user applications such as FTP, HTTP, and WAP with the underlying transport protocol, normally TCP. In addition, the interaction of TCP with the cdma2000 radio link protocol (RLP) also affects system performance. In this paper, we study these interactions in both simulation and lab environments. Our results show that optimizing these parameters can, in a number of cases, have a significant impact on system throughput performance.

On optimizing FER target for cdma2000 downlink

The cdma2000 /sup TM/ standard provides to each user an optional supplemental channel (SCH) in addition to the fundamental channel (FCH). The FCH, which carries signaling and control messages, is typically operated at 1% frame error rate (FER). The SCH carries user data which is typically more delay/error tolerant, and thus on the downlink, the base station has the option of operating the SCH at a higher FER. Transmitting to a user at a higher FER lowers the power requirement for that user and enables the base station to support more users. However, having high physical layer FER results in a low TCP layer throughput. It is not clear what value of target FER has to be used for the downlink SCH to obtain the maximum sector throughput. This paper studies this issue in more detail.

Optimizing TCP performance over cdma2000

In a cdma2000 system, most user applications operate using protocols such as HTTP, FTP, and WAP that are run over TCP. Consequently, optimizing TCP performance over cdma2000 is essential for providing good user experience and for optimizing system capacity. In this paper, we study a number of issues that affect TCP performance, and show that TCP parameter optimization can, in a number of cases, have a significant impact on system performance. We finally suggest suitable TCP parameter values to use and other methods to optimize system throughput.