Compared to WCDMA/HSPA UTRAN LTE introduces several relevant technological novelties, the major ones are described in the following:
UTRAN LTE uses new radio access techniques:
The radio access technology for downlink (DL) and uplink (UL) are both based on Orthogonal Frequency Division Multiplexing (OFDM): Orthogonal Frequency Division Multiple Access (OFDMA) for DL and Single Carrier - Frequency Division Multiple Access (SC-FDMA) for UL, The choice of SC-FDMA for the UL part was motivated by its lower Peak To Average Power Ration (PAPR) requirements, more suitable for low power mobile device transmitters.
UTRAN LTE has a simpler network architecture: in order to reduce network signaling and packet latency, the number of different nodes in the network has been reduced compared to HSPA. In LTE all Radio Resource Management (RRM) algorithms are placed at the same node, the evolved NodeB (eNode-B).
Those technological breaks have a significant impact on the Radio Resource Management (RRM) functionalities and motivate therefore intensive research in the field of RRM.
RRM main objective is to maximize the efficiency of the system radio resource usage while providing and controlling "Quality of Service" according to the different traffic QoS requirements. Briefly, for LTE the RRM consists of a set of algorithms including Time and Frequency Domain Packet Scheduling (TD-FDPS), Adaptive Transmission Bandwidth (ATB), Adaptive Modulation and Coding (AMC), Hybrid ARQ (HARQ), Power Control (PC), Handover (HO), Admission Control (AC) which control the resource sharing.
This research project develops RRM algorithms and studies their interaction with the aim of fulfilling the main RRM objective.
A common design philosophy is, to merge, whenever possible, the different functionalities in order to increase the flexibility of the system as well as the overall gain which derives from having a larger domain of optimization.
The ultimate objective is to design algorithms which are self-configurable in the sense that different traffic loads and propagation scenarios don't require specific parameter settings. Following this strategy, several algorithms for UL have been developed, being worth highlighting:
- The FDPS and ATB functionalities are merged into a single algorithm which automatically reacts to different traffic loads and propagation scenarios by selecting the most appropriate frequency band for the different users.
- A Quality of Service (QoS) aware AC is proposed by using the fractional PC to inherently tune itself for different traffic loads that the system may experience.
- A dynamic adjustment of the PC parameters based on the Overload Indicator (OI) is suggested to control the inter-cell interference regardless of the propagation scenario and the user's bandwidth.
In Downlink the following RRM principles are studied:
- QoS aware Time and Frequency Domain Packet Scheduling with the goal to serve the users according to their QoS requirements (delay, GBR and priority, BLER, etc.).
- Admission control algorithms which take into account the resource situation in the cell, the QoS requirements for the new bearers, as well as the priority levels and the currently provided QoS.
|Effektiv start/slut dato||19/05/2010 → …|
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