Specification of restricted set of cyclic shifts of root Zadoff-Chu sequences.doc

TSG RAN WG1 Meeting #49 R1-072324 Kobe, Japan, May 7-11, 2007 Agenda Item: Source: Huawei, Panasonic Title: Specification of restricted set of cyclic shifts of root Zadoff-Chu sequences Document for: Discussion and decision 1 Introduction The influence of high Doppler frequency shifts on the performances of RACH preambles have been discussed at several recent RAN1 meetings. The e of these discussions is the agreement to support high mobility scenarios through ms RACH preamble with restricted set of cyclic shifts. The set of RACH preambles x u,v(k) with zero correlation zone (ZCZ) of length N CS -1 are defined from the u -th root Zadoff-Chu (ZC) sequence x u(k) by cyclic shifts of multiples ofN CS according to x u,v(k)=x u,v ((k+ vN CS) mod N ), (1) where v is an integer and N is the length of ZC sequence defined by x u(k )=2/)1(?kukW ,k =0,1, …,N -1,W=Nje /2??, j=1?. (2) Although it is still not specified in the TS , there is understanding based on [1] that the restricted set of cyclic shifts for given root sequence x u(k) should be obtained by defining allowed multiples v=v a which can be used for generating RACH preambles. The allowed multiples v a are related to the cyclic offset c off ofx u(k) that would be produced by the Doppler frequency shift f Dopp =1/ T PRE , where T PRE = ms is the RACH preamble signal duration (without cyclic prefix). The absolute