HSDPA Adaptation Scheme of a MAC-hs PDU Size for Retransmissions

R. Bestak, P. Godlewski, and P. Martins (France)


Wireless Networks, HSDPA in UMTS, Protocol, HybridARQ


The adaptive modulation and coding technique of HSDPA rapidly adapts modulation and coding schemes to radio channels conditions. Each time a new data block (MAC hs PDU) is sent, its size is selected according to currently known radio channel conditions. The selection of a suit able MAC-hs PDU size is important since the size cannot be modified during retransmissions. However, due to in accurate measurements, feedback delays, etc., a MAC-hs PDU size may be selected inadequately. To deal with this issue, we suggest re-evaluating a MAC-hs PDU size be fore its first retransmission. If the first estimation of a MAC-hs PDU size turns out to be a wrong choice (i.e. too optimistic), the MAC-hs PDU size is decreased, if possi ble. Performance of the proposed scheme and the standard scheme is compared.

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