Francesco Davide Calabrese

Performance of Uplink Fractional Power Control in UTRAN LTE

UTRAN long term evolution is currently being standardized in 3GPP with the aim of more than twice the capacity over high-speed packet access. The chosen multiple access for uplink is single carrier FDMA, which avoids the intra-cell interference typical of CDMA systems, but it is still sensitive to inter-cell interference. As a result, the role of the power control becomes decisive to provide the required SINR, while controlling at the same time the interference caused to neighboring cells. This is the target of the fractional power control (FPC) algorithm lately approved in 3GPP. This paper evaluates in detail the impact of a FPC scheme on the SINR and interference distributions in order to provide a sub-optimal configuration tuned for both interference- and noise-limited scenarios.

Performance Evaluation of Received Signal Strength Based Hard Handover for UTRAN LTE

This paper evaluates the hard handover performance for UTRAN LTE system. The focus is on the impact that received signal strength based hard handover algorithm have on the system performance measured in terms of number of handovers, time between two consecutive handovers and uplink SINR for a user about to experience a handover. A handover algorithm based on received signal strength measurements has been designed and implemented in a dynamic system level simulator and has been studied for different parameter sets in a 3GPP UTRAN LTE recommended simulation scenario. The results suggest that a downlink measurement bandwidth of 1.25 MHz and a handover margin of 2 dB to 6 dB are the parameters that will lead to the best compromise between average number of handovers and average uplink SINR for user speeds of 3 kmph to 120 kmph.

Adaptive Transmission Bandwidth Based Packet Scheduling for LTE Uplink

UTRAN long term evolution is currently under standardization within 3GPP with the aim of providing a spectral efficiency 2 to 4 times higher than its predecessor HSUPA/HSDPA release 6. Single carrier FDMA has been selected as multiple access for the uplink. This technology requires the subcarriers allocated to a single user to be adjacent. The consequence is a reduced allocation flexibility which makes it challenging to design effective packet scheduling algorithms. This paper proposes a channel aware packet scheduling algorithm which exploits the bandwidth flexibility offered by the system to perform an allocation which closely resembles the frequency domain envelope of the metric to be optimized. Compared to a fixed bandwidth approach, the proposed algorithm provides a greater flexibility given the inbuilt adaptation to different scenarios and loads, as well as an improvement in term of performance for the Macro 3 case. In this case the uplink capacity is increased by approximately 20% in average cell throughput and 10% in UE outage compared to a fixed bandwidth channel aware approach.

Search-Tree Based Uplink Channel Aware Packet Scheduling for UTRAN LTE

UTRAN long term evolution is currently under standardization within 3GPP with the aim of providing a spectral efficiency 2 to 4 times higher than its predecessor HSUPA/HSDPA release 6. Single carrier FDMA has been selected as multiple access for the uplink. This technology requires the subcarriers allocated to a single user to be adjacent. The consequence is a reduced allocation flexibility which makes it challenging to design effective packet scheduling algorithms. This paper provides a search-tree based channel aware packet scheduling algorithm and evaluates its performance in terms of throughput and noise rise distributions. It is shown that, despite measurement errors and high inter-cell interference variability, the proposed algorithm can increase the uplink capacity by 24% for the macro 1 scenario and 19% for the macro 3 scenario.

Performance Analysis of Handover Measurements and Layer 3 Filtering for Utran LTE

Handover is one of the key functionalities which tries to keep a user equipment (UE) connected to the best base station (eNodeB). Handover is usually based on the downlink received signal strength (RSS) and carrier-to-interference ratio (CIR) measurements. Processing of the handover measurement is usually done in Layer 1 (LI) and Layer 3 (L3) by the UE, and handover is initiated by the serving eNodeB if certain event criteria are met. L3 filtering can be done in linear domain or decibel (dB) domain. A hard handover algorithm based on the downlink RSS and CIR measurements along with linear and dB domain L3 filtering has been studied by using a dynamic system level simulator for a 3GPP UTRAN LTE recommended scenario. The results suggest that RSS measurement with linear or dB domain L3 filtering is a better criterion for handover in terms of reduced number of handovers for a small penalty on the downlink CIR.

Interference Based Power Control Performance in LTE Uplink

In LTE uplink, the slow varying path gain and shadowing are compensated by the standardized open loop power control (OLPC). Further optimization of the system performance can be done via closed loop power control commands. In this contribution, it is shown that using such commands to control the interference caused by users to the system, it is possible to achieve a gain in the order of 20% on the average cell throughput while maintaining the same outage cell throughput compared to the performance of the OLPC. Furthermore, gain on both average and outage cell throughput can be achieved by tuning the parameters of the proposed scheme.

Combined Admission Control and Scheduling for QoS Differentiation in LTE Uplink

Long term evolution (LTE) architecture shall support end-to-end quality of service (QoS). For the QoS support and service differentiation it is important that the admission control and packet scheduling functionalities are QoS-aware. In this paper a combined admission control and a decoupled time-frequency domain scheduling framework for LTE uplink is presented. The proposed framework is shown to effectively differentiate QoS user classes in a mixed traffic scenario.

QoS-Aware Single Cell Admission Control for UTRAN LTE Uplink

UTRAN Long Term Evolution (LTE) architecture shall support end-to-end quality of service (QoS). To maintain the QoS of in-progress sessions in a cell it is important to admit a new radio bearer only if all the existing sessions and the new bearer can be guaranteed QoS according to their requirements. Hence admission control (AC) has an important role to play for QoS provisioning. In this paper we propose an AC algorithm for LTE uplink utilizing the fractional power control formula agreed in 3GPP. The proposed AC algorithm is compared with a reference AC algorithm. It is shown that at 10% unsatisfied user probability the carried traffic gain of the proposed AC algorithm can be up to around 29% over the reference AC algorithm. Furthermore, the proposed AC algorithm inherently tunes itself for varying load conditions without additional complexity.

Performance of proportional fair frequency and time domain scheduling in LTE uplink

Channel-aware scheduling is one of the advanced features introduced in the uplink of Long Term Evolution (LTE) in order to improve the system spectral efficiency. In the uplink of LTE channel-aware scheduling is possible thanks to the transmission of sounding reference signals. In this paper the performance of frequency and time domain scheduling in LTE uplink is investigated. In particular, we focus on the performance impact of various scheduling metrics which try to achieve proportional fairness in throughput or resource allocation. Our analysis shows that a combination of a throughput-based metric in the time domain and an SINR-based metric in the frequency domain is able to provide the highest performance. For example, in a noise-limited propagation environment with high inter-site distance the sector throughput gain compared to performing throughput-based proportional fair scheduling in both time and frequency domain is above 20%.

Performance of a Radio Resource Allocation Algorithm for UTRAN LTE Uplink

UTRAN LTE uplink is a SC-FDMA based system currently under development within 3GPP. The decision of basing the system on the packet switched technology attracts a lot of attention about the possible designs of resource allocation strategies. In this work we propose an algorithm which distributes the available bandwidth proportionally to the channel conditions while meeting the SINR target by means of power control. A simple resource allocation scheme which is fair with respect to bandwidth allocation is used as baseline reference. The comparison is carried out in terms of SINR distribution, user throughput and cell throughput. The results show that the proposed algorithm, when combined with slow power control, is able to improve the average cell throughput by approximately 23% with almost no reduction of the 5% outage average user throughput.