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Title:  LowPAPR, Lowdelay, HighRate SpaceTime Block Codes From Orthogonal Designs 
Authors:  Das, Smarajit 
Advisors:  Rajan, B Sundar 
Keywords:  Orthogonal Frequency Division Multiplexing Signal Processing Complex Orthogonal Designs (CODs) Real Orthogonal Designs (RODs) Spacetime Block Codes (STBCs) Coding Theory Square Complex Orthogonal Designs (SCOD) Peaktoaverage Power Ratio (PAPR) CayleyDickson Algebra Orthogonal Designs 
Submitted Date:  Mar2009 
Series/Report no.:  G23436 
Abstract:  It is well known that communication systems employing multiple transmit and multiple receive antennas provide high data rates along with increased reliability. Some of the design criteria of the spacetime block codes (STBCs) for multiple input multiple output (MIMO)communication system are that these codes should attain large transmit diversity, high datarate, low decodingcomplexity, low decoding –delay and low peaktoaverage power ratio (PAPR). STBCs based on real orthogonal designs (RODs) and complex orthogonal designs (CODs) achieve full transmit diversity and in addition, these codes are singlesymbol maximumlikelihood (ML) decodable. It has been observed that the datarate (in number of information symbols per channel use) of the square CODs falls exponentially with increase in number of antennas and it has led to the construction of rectangular CODs with high rate.
We have constructed a class of maximalrate CODs for n transmit antennas with rate if n is even and if n is odd. The novelty of the above construction is that they 2n+1 are constructed from square CODs. Though these codes have a high rate, this is achieved at the expense of large decoding delay especially when the number of antennas is 5or more. Moreover the rate also converges to half as the number of transmit antennas increases. We give a construction of rate1/2 CODs with a substantial reduction in decoding delay when compared with the maximal rate codes.
Though there is a significant improvement in the rate of the codes mentioned above when compared with square CODs for the same number of antennas, the decoding delay of these codes is still considerably high. For certain applications, it is desirable to construct codes which are balanced with respect to both rate and decoding delay. To this end, we have constructed high rate and low decodingdelay RODs and CODs from CayleyDickson Algebra.
Apart from the rate and decoding delay of orthogonal designs, peaktoaverage power ratio (PAPR) of STBC is very important from implementation point of view. The standard constructions of square complex orthogonal designs contain a large number of zeros in the matrix result in gin high PAPR. We have given a construction for square complex orthogonal designs with lesser number of zero entries than the known constructions. When a + 1 is a power of 2, we get codes with no zero entries. Further more, we get complex orthogonal designs with no zero entry for any power of 2 antennas by introducing co ordinate interleaved variables in the design matrix. These codes have significant advantage over the existing codes in term of PAPR. The only sacrifice that is made in the construction of these codes is that the signaling complexity (of these codes) is marginally greater than the existing codes (with zero entries) for some of the entries in the matrix consist of coordinate interleaved variables. Also a class of maximalrate CODs
(For mathematical equations pl see the pdf file) 
URI:  http://hdl.handle.net/2005/1046 
Appears in Collections:  Electrical Communication Engineering (ece)

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