Broadcast channel reception in NB-IoT devices

A method for improving reliability of a narrowband physical broadcast channel (NPBCH) reception in narrowband internet-of-things (NB-IoT) user equipment (UE) during a cell acquisition phase, whereas the UE receives one group of 64 encoded NPBCH subframes in order to attach itself to the cell, whereas the one group of 64 NPBCH subframes comprises a first master information block (MIB) comprising cell configuration and cell time information and four most significant bits of a system frame number (SFN), and whereas the four most significant bits of the system frame number are incremented every 64 NPBCH subframes, the method is characterized in that the UE receives, descrambles and de-rate-matches at least a first and a second group of 64 NPBCH subframes, whereas using the four most significant bits of the system frame number as a counter and a modifier sequence {m}, which is applied to the first group of 64 NPBCH subframes, before combining the both groups, decoding and extracting the first MIB from the combined NPBCH subframes and whereas the UE attaches to the cell if a match is found;

• wherein the modifier sequence {m} is calculated by performing the following steps:
• feeding a second MIB for pre-calculating the modifier sequence {m} with the bits bi=0 with i=0 . . . 33 except for b3=1 to a CRC calculation and attachment procedure, and
• performing a convolutional encoding procedure, resulting in a sequence {e},
• mapping the sequence {e} to the modifier sequence {m} according to {m}=(1−2*ei) with i =1 . . . 33.