Abstract
This PhD thesis focuses on system level analysis of Multi-Component Carrier (CC) management for Long Term Evolution (LTE)-Advanced. Cases where multiple
CCs are aggregated to form a larger bandwidth are studied. The analysis is performed for both local area and wide area networks.
In local area, Time Division Duplexing (TDD) is chosen as the duplexing mode in this study. The performance with different network time synchronization levels
is compared, and it is observed that achieving time synchronization significantly improves the uplink performance without penalizing much of the downlink transmission. Next the technique of frequency reuse is investigated. As compared to reuse-1, using different frequency channels in neighboring cells reduces the interference to offer large performance gain. To avoid the frequency planning, several decentralized algorithms are developed for interference reduction. Compared to the case of reuse-1, they achieve a gain of 50∼500% in cell edge user throughput, with small or no loss in average cell throughput.
For the wide area network, effort is devoted to the downlink of LTE-Advanced. Such a system is assumed to be backwards compatible to LTE release 8, i.e., some users can access all CCs (LTE-Advanced users), whereas some are restricted to operate within a single CC (release 8 users). First, load balancing across the multiple CCs is analyzed. Several known approaches are studied and the best one is identified. A cross-CC packet scheduler is afterwards proposed. It improves the cell edge user throughput by up to 90% over the independent scheduling with full buffer transmission and 40% with finite buffer transmission, depending primarily on the ratio of LTE-Advanced users. Meanwhile, there is no loss in the average cell throughput.
The channel aware packet scheduling and link adaptation require feedback of Channel Quality Indicator (CQI) and acknowledgement of packet receptions (ACK/NACKs) across the CCs. This gives rise to potentially high uplink overhead. Reduction of the feedback overhead is therefore investigated. A load adaptive CQI reduction scheme is recommended. It reduces the CQI by 94% at low load, and 79∼93% at medium to high load, with reasonable loss in downlink performance. To reduce the ACK/NACK feedback, multiple ACK/NACKs can be bundled, with slightly degraded downlink throughput.
CCs are aggregated to form a larger bandwidth are studied. The analysis is performed for both local area and wide area networks.
In local area, Time Division Duplexing (TDD) is chosen as the duplexing mode in this study. The performance with different network time synchronization levels
is compared, and it is observed that achieving time synchronization significantly improves the uplink performance without penalizing much of the downlink transmission. Next the technique of frequency reuse is investigated. As compared to reuse-1, using different frequency channels in neighboring cells reduces the interference to offer large performance gain. To avoid the frequency planning, several decentralized algorithms are developed for interference reduction. Compared to the case of reuse-1, they achieve a gain of 50∼500% in cell edge user throughput, with small or no loss in average cell throughput.
For the wide area network, effort is devoted to the downlink of LTE-Advanced. Such a system is assumed to be backwards compatible to LTE release 8, i.e., some users can access all CCs (LTE-Advanced users), whereas some are restricted to operate within a single CC (release 8 users). First, load balancing across the multiple CCs is analyzed. Several known approaches are studied and the best one is identified. A cross-CC packet scheduler is afterwards proposed. It improves the cell edge user throughput by up to 90% over the independent scheduling with full buffer transmission and 40% with finite buffer transmission, depending primarily on the ratio of LTE-Advanced users. Meanwhile, there is no loss in the average cell throughput.
The channel aware packet scheduling and link adaptation require feedback of Channel Quality Indicator (CQI) and acknowledgement of packet receptions (ACK/NACKs) across the CCs. This gives rise to potentially high uplink overhead. Reduction of the feedback overhead is therefore investigated. A load adaptive CQI reduction scheme is recommended. It reduces the CQI by 94% at low load, and 79∼93% at medium to high load, with reasonable loss in downlink performance. To reduce the ACK/NACK feedback, multiple ACK/NACKs can be bundled, with slightly degraded downlink throughput.
| Originalsprog | Engelsk |
|---|---|
| Udgivelsessted | Aalborg |
| Udgiver | |
| ISBN'er, trykt | 978-87-92328-56-4 |
| Status | Udgivet - 2010 |