It has been known that adaptive modulation and coding (AMC) at the physical layer can be combined with a truncated automatic repeat request (ARQ) at the data link layer so as to maximize the spectral efficiency under prescribed delay and error performance constraint. In this paper, we consider the same joint design approach when incremental redundancy-based hybrid ARQ (IR-HARQ) is associated with an AMC design at the physical layer. The extensive simulation studies for predicting the progressive combining gain with each retransmission enables to evaluate the bandwidth efficiency that can be achieved by selecting a more aggressive modulation and coding rate set (MCS) at the expense of packet error rate in earlier transmissions. It has been demonstrated that the aggressive AMC design approach in association with IR-based truncated HARQ can improve bandwidth efficiency by 5.8 and 3.3 dB, as compared to the conservative AMC design approach with truncated HARQ and aggressive AMC design approach with truncated ARQ (i.e., without taking the progressive combining gain in HARQ into account), respectively.

No abstract

SUMMARYThis paper proposes a distributed coordination framework with opportunistic scheduling among multiple users as opposed to the existing works on the multiple-cell cooperative beamforming problem that deals with a single active user in each cell. In this cross-layer design framework that deals with the beamforming in the physical layer and multiuser scheduling in the upper layer, radio resource management and inter-cell coordination issues are jointly considered to improve the cell-edge throughput performance by trading off their individual benefit in an optimal manner. Our simulation results demonstrated that its performance can reach up to 85% of its upper bound at the cell boundary.

No abstract

No abstract