| 1. |
- Jaldén, Joakim, 1976-, et al.
(författare)
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On the limits of sphere decoding
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory (ISIT), Vols 1 and 2. - NEW YORK : IEEE. - 0780391500 ; , s. 1691-1695
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Konferensbidrag (refereegranskat)abstract
- The sphere decoder has emerged as one of the most promising techniques for maximum likelihood detection of symbols transmitted over a general MIMO channel. Although efficient for problems of moderate size it is known that the original sphere decoder is of exponential (expected) complexity which limits its usage for large scale problems. However, at this stage, many alterations and improvements over the original algorithm have appeared in the literature. Herein we study a generic sphere decoder for the i.i.d. Rayleigh fading MIMO channel. The detection ordering and search radius (parameters of the algorithm) are allowed to be arbitrary functions of the decoder input, the only restriction being that the search radius is chosen such that the detection problem is solved. It is shown that the set of problem instances solvable by the sphere decoder in less than exponential time will tend to zero with increasing problem size. This extends previous results by providing a statement which is stronger than exponential expected complexity while relaxing the assumptions regarding the specific decoder implementation.
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| 2. |
- Lindell, Göran
(författare)
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Some exact union bound results for maximum likelihood detection in MIMO systems
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory (ISIT). - 0780391500 ; , s. 2223-2227
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Konferensbidrag (refereegranskat)abstract
- In this paper we investigate some properties of the union bound for a basic MIMO system, assuming uncoded QAM transmission, uncorrelated Rayleigh fading, and maximum likelihood detection. The presented union bound results cover several choices of the number of transmitting and receiving antennas (up to 16). It is also illustrated how the pair-wise error probability approaches the Q( )-function as the number of receiving antennas increases
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| 3. |
- Loncar, Maja, et al.
(författare)
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Estimating the list size for BEAST-APP decoding
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory (ISIT). - 0780391500 ; , s. 1126-1130
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Konferensbidrag (refereegranskat)abstract
- The BEAST-APP decoding algorithm is a low-complexity bidirectional algorithm that searches code trees to find the list of the most likely codewords, which are used to compute approximate a posteriori probabilities (APPs) of the transmitted symbols. It can be applied to APP-decoding of any linear block code, as well as in iterative structures for decoding concatenated block codes. Previous work has shown that the list size sufficient to achieve the performance of true-APP decoding is very small. This paper aims at providing a theoretical justification for this result. The sufficient list size is estimated first via the minimum list distance - a parameter that is defined and analyzed as a key factor that governs the performance of list-based algorithms. Additionally, statistical properties of the codeword likelihoods are investigated and the typical list structure is presented. Preliminary simulation results for iterative BEAST decoding confirm the list-size estimates obtained from both approaches
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| 4. |
- Massey, James L., et al.
(författare)
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Conservation of mutual and directed information
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory (ISIT). - 0780391500 ; , s. 157-158
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Konferensbidrag (refereegranskat)abstract
- Two conservation laws for mutual information in terms of directed informations between two synchronized sequences of random variables are derived, the first for the case of no conditioning and the second for the case of causal conditioning on a third synchronized sequence. As a byproduct of the derivation of the first conservation law, the directed information specifying the feedback flowing from the second sequence to the first sequence is identified, which leads to a simple proof that a previously known sufficient condition for equality of mutual and directed information is also a necessary condition
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| 5. |
- Pavlushkov, Victor, et al.
(författare)
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Unequal error protection explained by state-transition graphs
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory (ISIT). - 0780391500 ; , s. 2236-2240
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Konferensbidrag (refereegranskat)abstract
- In this paper unequal error-correcting capabilities of convolutional codes are studied. State-transition graphs are used for investigating the error-correcting capabilities for specific inputs or outputs of given convolutional encoding matrices. Active burst input- and output-distances are defined and shown to be generalizations of the active burst distance. These new distances provide better estimates of the error-correction capability, especially when we communicate close to or above the channel capacity and they are connected to the corresponding free input- and output-distances via lower bounds
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| 6. |
- Rusek, Fredrik, et al.
(författare)
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Near BER optimal partial response codes
- 2005
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Ingår i: 2005 IEEE International Symposium on Information Theory, Adelaide. - 0780391500 ; , s. 538-542
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Konferensbidrag (refereegranskat)abstract
- Partial response signaling (PRS) codes with maximal minimum Euclidean distance have previously been found by linear programming. These perform very well in the narrowband-high energy region, but they were not optimized for minimal bit error rate (BER), so they are only optimal in the limit of infinite signal to noise ratio. Here we search for codes that perform better for more practical signal to noise ratios. The BER objective function is no longer linear, but it is still convex
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| 7. |
- Rusek, Fredrik, et al.
(författare)
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The two dimensional Mazo limit
- 2005
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Ingår i: Proc., 2005 IEEE International Symposium on Information Theory, Adelaide. - 0780391500 ; , s. 970-974
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Konferensbidrag (refereegranskat)abstract
- Faster than Nyquist (FTN) signaling is extended. We send FTN pulse trains that overlap in both time and frequency; this is called two dimensional Mazo signaling. The minimum time and frequency separation that achieves square minimum distance 2 for root raised cosine pulses is found. Two dimensional signaling is more bandwidth efficient than one dimensional. A simple decoder is tested and it verifies the distance results
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