Adaptive Modulation schemes for MIMO HSDPA

ABSTRACT There is a growing interest in the standardisation ofMultiple Input Multiple Output (MIMO) schemes forHigh Speed Downlink Packet Access (HSDPA) forfuture releases of UMTS. The I-METRA project,building on the legacy of METRA, has set up as one ofits priorities to contribute to this standardisation effortby developing and evaluating pertinent transmission andreception schemes for this type of systems. I. INTRODUCTION The concept of HSDPA has been recently standardisedin 3GPP for UMTS [1]. It considers enhancements thatcan be applied to UTRA to provide very high-speeddownlink packet access by means of a high-speeddownlink shared channel (HS-DSCH). Among theseenhancements, the I-METRA project is focused onMIMO antenna processing techniques which arenecessarily also related to the evolution of otherprocedures, such as Adaptive Modulation and Coding(AMC) or Hybrid Automatic Repeat on Request (H-ARQ), in order to include adaptive MIMO techniques inthe HS-DSCH structure.Within the HSDPA concept, it is expected thatmodulation and coding are adapted to channel, trafficand user requirements. In this procedure, the userequipment (UE) should be able to estimate the channelstate information and translate it into a metric, which istransmitted to its serving Node B within the DPCCH-HS channel (an uplink Dedicated Physical Controlchannel associated with HS-DSCH). It is required thatthis metric value can be mapped to the downlinkchannel FER. The Node B is continuously selecting theuser to be served and its data rate based on a schedulingalgorithm and on that feedback information receivedfrom all active users. The uplink DPCCH-HS alsocarries H-ARQ acknowledgements, which are used bythe Node B to update the user traffic queues. The use ofAMC and H-ARQ procedures along with Fast CellSelection and Stand-Alone DSCH [2] will provide up to10.7Mbps of data rate. It is envisioned that the use ofMIMO techniques on top of these other procedures willallow doubling this upper bound [3].In the first stage of I-METRA