Janne Peisa

WCDMA enhanced uplink - principles and basic operation

The WCDMA uplink has recently been enhanced with hybrid ARQ, scheduling, and shorter TTI to provide improved performance for packet data services in terms of reduced delays, improved availability of high data rates, and increased capacity. This paper gives an overview of the design targets, the basic principles, and how they are integrated into WCDMA.

Queue management for TCP traffic over 3G links

We propose a novel active queue management scheme tailored to the specific characteristics of third generation (3G) cellular networks. Such links are often the bottleneck for an end-to-end connection and dedicated to one host. Taking advantage of these specific characteristics, we developed a queuing scheme that is simpler than popular random early detection (RED) schemes. Despite its simplicity, our solution yields superior performance for 3G links in terms of high link utilization, low queuing delay, and high end-to-end throughput for TCP bulk data transfers. Our simulation results show a clear win over both conventional drop-tail queuing and also a comparable RED scheme.

High Speed Packet Access Evolution - Concept and Technologies

In this paper we present the main concepts of high speed packet access evolution currently being standardized in 3GPP. In general HSPA evolution consists of introduction of MIMO, higher order modulation, and protocol optimizations and optimizations for voice over IP. We describe these improvements in detail and show that HSPA Evolution can reach performance comparable to those of long term evolution of UMTS terrestrial radio access network in a 5 MHz deployment.

TCP performance over HS-DSCH

Both the performance of transmission control protocol (TCP) based applications and the effect of TCP on system capacity in a WCDMA system using high speed downlink shared channel (HS-DSCH) are evaluated. It is found that the HS-DSCH improves both the application performance and the system capacity. The effect of TCP on application performance is much stronger than the effect on the system capacity.

Buffer management for rate-varying 3G wireless links supporting TCP traffic

Radio resource management functions in third generation cellular systems allocate capacity based on both demand and available capacity. A 3G wireless link may therefore be subject to considerable rate variations. These rate variations impose particular challenges on the buffer design. A well performing buffer should secure a high degree of link utilization without introducing excessive buffering delays. Meeting both objectives under highly varying link conditions is not possible with a conventional, fixed-size buffer. In this work, we evaluate a novel active queue management scheme tailored to the specific characteristics of 3G links. The method uses a simple algorithm to achieve favorable interaction with TCP. At the same time, the link state is reflected in the buffer control parameters. Based on an analysis of the pipe capacity of wireless links, we evaluate the required buffer size for different link rates. The analysis is verified using simulations. We show that the proposed method of using adaptive buffer sizes is a feasible approach resulting in adequate performance at different link conditions.

End-to-end performance of WCDMA enhanced uplink

In this paper we study the end-to-end performance of the enhanced uplink of WCDMA. We present results for latency and TCP performance on both uplink and downlink when using the enhanced uplink. The results show that the enhanced uplink can significantly improve the end-to-end performance of both for up- and downlink oriented traffic when compared to the uplink provided by 3GPP R5. The expected performance depends strongly on the configuration of the enhanced uplink, especially on the HARQ operating point.

Transmission offset adaptation in UTRAN

We propose an adaptive frame transmission offset method for systems supporting soft handover. With the suggested method, the transmission offset is continuously adapted to the momentary network delay. The solution is targeted for interactive class packet data traffic, for which the end-to-end delay has a crucial effect on the performance. The application studied is a UMTS terrestrial radio access network (UTRAN). Our results show the clear advantages of the proposed method over commonly used solutions.

Analytic Study of TCP Performance over a Soft Rate Switching WCDMA Bearer

In this paper a soft rate switching principle for CDMA is suggested combining the selection of processing gain and BLER-target. An analytical model for TCP performance is developed and an evaluation is done for a best-effort TCP service over a downlink WCDMA bearer. Results show that the combined selection can smoothly control the trade-off between high TCP service quality and high capacity. Also the quality and coverage trade-off can be managed with the same principle

Enhancing Packet Data Access in WCDMA

In this paper, the first step of evolving WCDMA beyond IMT-2000 is outlined and elaborated upon. It is shown how techniques such as fast link adaptation, fast hybrid ARQ and fast scheduling, among others, can be applied to WCDMA, leading to increased throughput for best-effort services, lower delays, and downlink peak rates in the order of 10 Mbit/s. The end-to-end protocol architecture is discussed, and using protocol simulations the benefit of having a hybrid type II ARQ scheme in Node B is shown.