Interaction Between Adaptive Modulation and Scheduling for High-Rate Downlink Packet Transmission

This paper addresses adaptive modulation for downlink best effort packet data ("Multiuser diversity") in a system employing high-order modulation and Multi-Code (MC) direct-sequence code-division multiple-access formats. In particular, it analyzes the interaction between adaptive modulation and scheduling under the MC constraint that the number of MCs is relatively small (e.g., for relay-based downlink data transmission) and that all MCs to a given user have the same modulation. For this, two scheduling schemes are considered - two-best user and selective relative best user - that provide a balance between throughput and fairness, while accounting for MC and power constraints, high-order modulation, and channel coding for a fine rate granularity.