# Mathematics Colloquia and Seminars

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### Discrete geometry, finite groups, and wireless communications

**Algebra & Discrete Mathematics**

Speaker: | Thomas Strohmer, UC Davis |

Location: | 593 Kerr |

Start time: | Fri, Apr 9 2004, 11:00AM |

Code Division Multiple Access (CDMA) is an important transmission scheme in wireless communications (no background in communications is needed for this talk). A crucial step in the design of CDMA systems is the construction of so-called spreading sequences, a set of vectors in C^n that has to satisfy a number of challenging properties. In my talk I will demonstrate that the problem of spreading sequence design is closely related to problems in discrete geometry, sphere packings, and coding theory. Furthermore I will show how one particular spreading sequence design problem can be solved by using deep results by Calderbank et al. on the finite Heisenberg group. (Note: the paper by Calderbank et al. is also related to a fascinating construction of quantum error correcting codes by Calderbank, Eric Rains, et al.).

NOTE THE TIME CHANGE!!!