On the Nonexistence of the Ding-Helleseth-Martinsens Constructions of   Almost Difference Set for Cyclotomic Classes of Order 6
  Pseudorandom sequences with optimal three-level autocorrelation have important applications in CDMA communication systems. Constructing the sequences with three-level autocorrelation is equivalent to finding cyclic almost difference sets as their supports. In a paper of Ding, Helleseth, and Martinsen, the authors developed a new method known as the Ding-Helleseth-Martinsens Constructions in literature to construct the almost difference set using product set between GF(2) and union sets of cyclotomic classes of order 4. In this correspondence, we show that there do not exist such constructions for cyclotomic classes of order 6. 
Minglong Qi, Shengwu Xiong, Jinbgling Yuan, Wenbi Rao, Luo Zhong
cs.CR