Low delay data transmission over the ATDMA air interface

Among the features proposed for UMTS by the RACE 2084 ATDMA project is the provision for data services from 9.6 to 64 kbits/s with low transmission delay (no more than 30 ms) and high integrity (bit error rate lower than 10/sup -6/). The paper shows how this service class can be transported over the ATDMA air interface. After a brief presentation of the latter, the authors develop an appropriate error control coding scheme based on code concatenation. To protect the data to the required quality while matching varying propagation and interference conditions, they define so-called transport modes. Under link adaptation control, the air interface configuration changes from one mode to another so that the target link quality can be maintained. Design parameters are dimensioned and decoding performances are assessed by means of computer and hardware simulations. The authors use a dedicated two-stage simulation approach based on hidden Markov modelling of the transmission channel. Results confirm the validity of the proposed scheme.