Please use this identifier to cite or link to this item: `https://hdl.handle.net/10356/89385`
 Title: How long can optimal locally repairable codes be? Authors: Guruswami, VenkatesanXing, ChaopingYuan, Chen Keywords: DRNTU::Science::MathematicsLocally Repairable CodeSingleton Bound Issue Date: 2018 Source: Guruswami, V., Xing, C., & Yuan, C. (2018). How long can optimal locally repairable codes be?. Leibniz International Proceedings in Informatics, 116, 41-. doi:10.4230/LIPIcs.APPROX-RANDOM.2018.41 Series/Report no.: Leibniz International Proceedings in Informatics Abstract: A locally repairable code (LRC) with locality r allows for the recovery of any erased codeword symbol using only r other codeword symbols. A Singleton-type bound dictates the best possible trade-off between the dimension and distance of LRCs - an LRC attaining this trade-off is deemed optimal. Such optimal LRCs have been constructed over alphabets growing linearly in the block length. Unlike the classical Singleton bound, however, it was not known if such a linear growth in the alphabet size is necessary, or for that matter even if the alphabet needs to grow at all with the block length. Indeed, for small code distances 3,4, arbitrarily long optimal LRCs were known over fixed alphabets. Here, we prove that for distances d >=slant 5, the code length n of an optimal LRC over an alphabet of size q must be at most roughly O(d q^3). For the case d=5, our upper bound is O(q^2). We complement these bounds by showing the existence of optimal LRCs of length Omega_{d,r}(q^{1+1/floor[(d-3)/2]}) when d <=slant r+2. Our bounds match when d=5, pinning down n=Theta(q^2) as the asymptotically largest length of an optimal LRC for this case. URI: https://hdl.handle.net/10356/89385http://hdl.handle.net/10220/46213 DOI: http://dx.doi.org/10.4230/LIPIcs.APPROX-RANDOM.2018.41 Rights: © 2018 Venkatesan Guruswami, Chaoping Xing, and Chen Yuan; licensed under Creative Commons License CC-BY. Fulltext Permission: open Fulltext Availability: With Fulltext Appears in Collections: SPMS Journal Articles

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