Scheduling Policies in Time and Frequency Domains for LTE Downlink Channel: A Performance Comparison

A key feature of the Long-Term Evolution (LTE) system is that the packet scheduler can make use of the channel quality information (CQI), which is periodically reported by user equipment either in an aggregate form for the whole downlink channel or distinguished for each available subchannel. This mechanism allows for wide discretion in resource allocation, thus promoting the flourishing of several scheduling algorithms, with different purposes. It is therefore of great interest to compare the performance of such algorithms under different scenarios. Here, we carry out a thorough performance analysis of different scheduling algorithms for saturated User Datagram Protocol (UDP) and Transmission Control Protocol (TCP) traffic sources, as well as consider both the time- and frequency-domain versions of the schedulers and for both flat and frequency-selective channels. The analysis makes it possible to appreciate the difference among the scheduling algorithms and to assess the performance gain, in terms of cell capacity, users' fairness, and packet service time, obtained by exploiting the richer, but heavier, information carried by subchannel CQI. An important part of this analysis is a throughput guarantee scheduler, which we propose in this paper. The analysis reveals that the proposed scheduler provides a good tradeoff between cell capacity and fairness both for TCP and UDP traffic sources

3GPP QoS-based scheduling framework for LTE

This paper proposes the design of a scheduling framework for the downlink of the Long Term Evolution (LTE) system with the objective of meeting the Quality of Service (QoS) requirements as defined by the QoS architecture of the 3G Partnership Project (3GPP) specifications. We carry out a thorough review of 3GPP specifications analyzing the requirements of the 3GPP QoS architecture. LTE bearers may be associated with a Guaranteed Bit Rate (i.e., GBR bearers) or not (i.e., non-GBR bearers). Additionally, the specifications establish a Packet Delay Budget (PDB) to limit the maximum packet transfer delay. To achieve our goal, we design a channel-aware service discipline for GBR bearers which is able to fulfill not only the GBR but also the PDB. Additionally, we also design an algorithm for prioritizing GBR and non-GBR bearers from different QoS Class Identifiers (QCIs) following 3GPP QoS rules. We compare the proposed framework with two reference schedulers by means of network-level simulations. The results will show the ability of the proposed framework to address the QoS requirements from 3GPP specifications while providing an interesting performance from a spectral efficiency viewpoint.This work is partially supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (project TIN2013-46223-P)