IssueswithZC-basedPSCdesign.docVIP

 PAGE 4/ NUMPAGES 5 3GPP TSG-RAN WG1 #49 R1-072092 May 7th-11th, 2007 Kobe, Japan Agenda item: 7.2 Source: QUALCOMM Europe Title: Issues with ZC-based PSC design Document for: Discussion and Decision 1 Introduction Zadoff-Chu (ZC) based sequence is widely used in LTE. It has been recognized by many companies, e.g.,  REF _Ref165522519 \n \h [1]- REF _Ref165734241 \n \h [4], that high correlation exists between Chu sequences with different lengths in the uplink. During the last RAN1 meeting, the decision was made that primary synchronization codes (PSC) are ZC based. In this contribution, we raise the issue of using ZC sequence in both uplink and downlink. Even with a limited set of results (See Appendix), we show that There exists high correlation values between uplink and downlink ZC sequences with different lengths The high correlation value is an issue for the initial cell search in TDD systems Note that the analyses from  REF _Ref165522519 \n \h [1]-  REF _Ref165734241 \n \h [4] also apply here. 2 Analysis Zadoff-Chu (ZC) based sequence may be used in: Uplink Physical uplink control channel (PUCCH) ACK/NACK user multiplexing (frequency domain CDM using ZC) Each user is assigned a different cyclic shift of a base ZC sequence in each OFDM symbol length 12 sequence is used The sequence is either cyclic extension or truncation of ZC sequence CQI (TBD) ZC sequence is considered as the candidate Uplink reference signal (DM RS) (working assumption) Sequence length is 12*K where K is the number of resource block assigned to an UE and 12*K has the following constraint The sequence is either cyclic extension or truncation of ZC sequence (based on the closest prime number relative to 12*K) Random access channel (working assumption) ZC sequence with length ~800 All root indexes may be needed to increase the reuse factor of RACH Tone spacing : 1.25KHz Broadband sounding signal (BPICH) Sounding bandwidth is TBD Downlink (current