TCP-Aware Channel Allocation in CDMA Networks

Abstract

Abstract-This paper explores the use of rate adaptation in cellular networks to maximize throughput of long-lived TCP sessions. Modern cellular networks incorporate RF technology that allows them to dynamically vary the wireless channel rate in response to user demands and channel conditions. However, the set of data rates as well as the scheduler's rate adaptation policy are typically chosen to maximize the throughput of inelastic connections. We focus on the problem of maximizing the throughput of TCP connections and propose a joint optimization of MAC and physical layer parameters with respect to TCP sending rate. In particular, we propose a simple TCP-aware channel scheduler that adapts the wireless channel rate to changes in the TCP sending rate and explore its performance for both single and multiple concurrent sessions. In the case of a single TCP session, we develop a fluid model of its steady-state behavior in such a system that adapts between two channel rates. The accuracy of the model, its utility in selecting optimal rates as well as the performance of systems with up to three channel rates are explored with ns-2 simulations. Our results indicate that a two-rate scheme improves TCP throughput by 15 to 20 percent over a system that does not exploit rate adaptation and that little additional benefit accrues from the addition of a third channel rate. Finally, we extend the framework to scenarios where bandwidth is shared by multiple TCP sessions. We propose two channel allocation algorithms, one relying on detailed TCP state information, the other not, and explore their performance through simulation. Our results indicate that TCP throughput is relatively insensitive to either channel allocation algorithm, and adaptive rate variation is the dominant factor in performance.

Using traffic asymmetry to enhance TCP performance

“…TCP-aware resource allocation algorithms over a CDMA network are studied in [18], the objective being to maximize throughput. The proposed algorithm in that paper uses information on the TCP state (slow start or congestion avoidance) to allocate the data rate more appropriately at the wireless link.…”

Optimal channel access for TCP performance improvement in cognitive radio networks

“…As a consequence, given that sensed outcomes and design parameters, data rate r and BER can be determined. Furthermore, in wireless TCP networks, packets loss mainly caused by wireless fading channel, which is a common assumption in the literature [14]. Consequently, the packet loss probability p is approximately equal to the packet error rate which is closely related to BER and data-link layer settings, such as frame size and ARQ.…”

“…Cross-layer optimization is a concept that considers the possibilities of communicating among multiple layer to obtain better performance outcomes. In [14], the authors explore the use of rate adaptation in cellular networks to maximize TCP throughput. Based on TCP congestion window dynamics and wireless channel conditions, link layer transmission modes are selected to maximize TCP throughput in [15].…”

Cross-Layer Design for TCP Performance Improvement in Cognitive Radio Networks

“…As a consequence, for given sensed outcomes and design parameters in CR networks, the data rate r and BER can be obtained. Furthermore, in wireless TCP networks, the packet loss is mainly due to wireless fading channels, which is a common assumption in the literature [24]. Consequently, the packet loss probability p is approximately equal to the packet error rate, which is a function of BER and data-link layer parameters, such as frame size and ARQ.…”

“…The authors in [23] jointly consider adaptive modulation and coding (AMC) at the physical layer and automatic repeat request (ARQ) at the data-link layer to maximize the physical throughput. In [24], the authors explore the use of rate adaptation in cellular networks to maximize the TCP throughput. Based on TCP congestion window dynamics and wireless channel conditions, link-layer transmission modes are selected to maximize the TCP throughput in [25].…”