Motivated by questions in property testing, we search for linear error-correcting codes that have the "single local orbit" property: i.e., they are specified by a single local constraint and its translations under the symmetry group of the code. We show that the dual of every "sparse" binary code whose coordinates are indexed by elements of F_{2^n} for prime n, and whose symmetry group includes the group of non-singular affine transformations of F_{2^n} has the single local orbit property. (A code is said to be "sparse" if it contains polynomially many codewords in its block length.) In particular this class includes the dual-BCH codes for whose duals (i.e., for BCH codes) simple bases were not known. Our result gives the first short (O(n)-bit, as opposed to the natural exp(n)-bit) description of a low-weight basis for BCH codes. The interest in the "single local orbit" property comes from the recent result of Kaufman and Sudan (STOC 2008) that shows that the duals of codes that have the single local orbit property under the affine symmetry group are locally testable. When combined with our main result, this shows that all sparse affine-invariant codes over the coordinates F_{2^n} for prime n are locally testable. If, in addition to n being prime, if 2^n-1 is also prime (i.e., 2^n-1 is a Mersenne prime), then we get that every sparse cyclic code also has the single local orbit. In particular this implies that BCH codes of Mersenne prime length are generated by a single low-weight codeword and its cyclic shifts.
Distributed Hypothesis Testing based on Unequal-Error Protection Codes
提出了噪声网络上二进制假设检验的编码和检验方案，并推导出相应的第二类误差指数。当通信是在一个离散的无记忆信道（DMC），我们的计划相结合的Shimokawa-Han-Amari的假设检验计划与Borade的不等错误保护（UEP）的信道编码。采用单独的源信道编码架构。所得指数对于新引入的\emph{generalized testing against conditional independence}类是最优的。当通信通过MAC或BC时，我们的方案将混合编码与UEP相结合。由此产生的误差指数在MAC是最佳的情况下，广义测试对条件独立性与独立的观察在两个传感器，当MAC分解成两个单独的DMC。在这种情况下，单独的源-信道编码是足够的;当测试是反对独立性时，在任意相关的传感器观测下，这个相同的结论也成立。对于BC，具有UEP的混合编码的误差指数区域在两个决策中心处获得的指数之间表现出折衷。当两个接收机都以最大化不同假设下的误差指数为目标，并且传感器观测值的边际分布在这些假设下不同时，则可以使用以下策略来减轻这种折衷。传感器的假设，提出了一个试探性的猜测，并适用于我们的编码和测试方案的DMC只为决策中心，是不感兴趣的猜测假设下的指数最大化。
