Modified maximal ratio combining HARQ scheme for HSDPA

One of the main evolutions of the WCDMA standard is the high-speed downlink packet access (HSDPA) concept, which offers peak data rates exceeding 10 Mbps. A hybrid automatic repeat request (HARQ) plays an important role in HSDPA. In this paper the impact of the combining scheme in HARQ to the system performance is considered. A conventional maximal ratio combining (MRC) is not an optimal method of combining (re)transmissions for the HARQ under the condition of the imperfect channel estimation. A modified MRC method is proposed, which allows decreasing the impact of the errors in the channel estimates to the performance of HSDPA.