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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.

Opportunistic Uplilnk Scheduling for 3G LTE Systems

In this paper we propose a heuristic opportunistic scheduler that is consistent with the resource allocation constraints of the uplink channel for 3G long term evolution (LTE) systems. Retransmission processes as well as channel conditions are taken into account in the formation of the scheduling decision. The heuristic scheduler could be seen a reasonable choice for solving the constrained resource allocation maximization problem since it is computationally feasible and can find a practical solution. We also formulate an integer programming problem that provides a theoretical optimal solution. The heuristic scheduler was found to perform relatively well when compared to the optimal solution.

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.

On the performance of Heuristic opportunistic scheduling in the uplink of 3G LTE networks

In this paper we study the performance of the heuristic localized gradient algorithm (HLGA) that was designed for uplink scheduling in 3G long term evolution (LTE) systems. The performance of the algorithm is examined when dynamic traffic models are assumed. With dynamic traffic, users will have different buffer occupancies. The amount of resources granted to a user need to be mapped to the size of those occupancies. We suggest for that, a procedure called dasiapruningpsila where resources are given to users who maximize a certain criteria and later on prune the extra resources and allocate them to other users. We also study the performance loss caused by more realistic assumptions on base station knowledge of the terminalpsilas buffer state. We first assume no delay in the reporting of the buffer occupancy but later evaluate the effect of buffer reporting delays and quantification of data used to report the status of a buffer.

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.

Overload Control of Best-Effort Traffic in the UTRAN Transport Network

In this work, it is shown that overload of the UTRAN transport network can result in a severe degradation of the end-user throughput and quality of service. In particular, for dedicated transport channels carrying non-guaranteed traffic in the downlink, a loss of more than 50% of the traffic is observed already at quite modest overload levels. To counteract these adverse effects, we propose a method to gracefully regulate transport network overload by temporarily limiting the available transport formats in the UTRAN MAC layer. Results show that the proposed method is capable of delivering both good end-user quality and a low level of losses at times of transport network overload. With the present method, it is therefore possible to relax the admission criteria to the UTRAN transport network, resulting in reduced connection blocking, higher transport network utilization, and better end-user satisfaction

Channel-aware inter-cell interference coordination for the uplink of 3G LTE networks

In this paper we propose a heuristic inter-cell coordination scheme for scheduling users in an opportunistic multi-cell network. The scheme is mainly designed to be implemented in the uplink of networks that utilize the Third Generation Partnership Project Long Term Evolution (3GPP LTE) technology. The objective of the scheme is to coordinate the uplink transmission in neighboring cells such that inter-cell interference is mitigated and the aggregate utility of the mobile users is maximized. In addition to the heuristic approach we formulate the inter-cell scheduling coordination as an integer programming problem. While the optimal solution cannot be realized in practice due to the computational complexity, it provides good insights of how well different algorithms perform. Numerical results show that the proposed coordination method delivers near-optimal performance in the exemplified cases.

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.