Valery P. Ipatov

On the Karystinos-Pados bounds and optimal binary DS-CDMA signature ensembles

Tightness of the Karystinos-Pados bounds was originally proved with four exceptions. In this letter, we modify the algorithm of constructing signatures removing three of these exceptions. For the fourth one the tighter bounds are derived.

The Performance Analysis of MPE-FEC Decoding Methods at the DVB-H Link Layer for Efficient IP Packet Retrieval

DVB-H is a new broadcasting standard, which offers reliable high data rate reception of IP packets for mobile handheld battery-powered devices. A link layer with multiprotocol encapsulation (MPE), including Reed-Solomon forward error correction (FEC) combined with a cyclic redundancy check (CRC), is defined in the standard to work on top of the DVB-T physical layer. For error correction in the receiver the DVB-H standard suggests to use erasure decoding based on the CRC information. Yet, the decoding method is not strictly determined in the standard. This paper investigates the performance of five different Reed-Solomon decoding schemes for the DVB-H link layer forward error correction called MPE-FEC. They differ on utilization strategy of existing erasure information. The performance of different decoding methods are evaluated analytically in an binary symmetric channel (BSC) and with simulations in the additive white Gaussian noise (AWGN) and a mobile fading channel. For the simulations in the fading channel a packet channel model based on actual measurements is designed. It is shown that more sophisticated decoding methods than the one suggested in the standard are required for efficient retrieval of IP packets

Performance Analysis of Different Reed-Solomon Erasure Decoding Strategies at the DVB-H Link Layer

DVB-H is a new broadcasting standard, which offers reliable high data rate reception for mobile handheld and battery-powered devices. A link layer, including Reed-Solomon error correction combined with cyclic redundancy check (CRC), is defined in the standard to work on top of the DVB-T physical layer. The DVB-H suggests to use an erasure decoding method based on CRC information. Yet, the decoding method is not strictly determined in the standard. This paper investigates the performance of four different Reed-Solomon erasure decoding schemes for DVB-H link layer forward error correction

Oversaturating synchronous CDMA systems using collaborative coding

Oversaturated synchronous CDMA system is proposed based on collaborative coding, where data bits of group of L + s users are jointly one-to-one mapped onto 2/sup L+s/ L-dimensional signal vectors. Instead of the unique signature per each user, the L-dimensional signature subspace is used to transmit bits of L + s users (s > 0). All signature subspaces are orthogonal to each other which simplifies the optimal receiver structure. With signal space dimension N, the number of users is K = N(1 + s/L). Preferable collaborative codes are found using the sphere packing theory for L = 2...5, s = 1, 2. Trade-off between oversaturation efficiency and energy loss/gain is evaluated against the conventional non-oversaturated orthogonal CDMA.

Eliminating odd correlations in asynchronous DS CDMA employing cyclic prefix

In an asynchronous DS CDMA system performance of a single-user receiver suffers from the presence of odd cross-correlations of user signatures due to information modulation and variable delays between user signals. To neutralize this effect, employing a cyclic prefix is recommended. Both analytical and simulation results demonstrate that scenarios exist where such a measure brings about a substantial gain in performance with no compromising of spectral efficiency

Asymptotic optimality of random PSK signature ensembles

Selection of a proper signature ensemble is the point of a special care in designing code division multiple access (DS CDMA) systems. When the receiver complexity beyond that of a single user algorithm is not affordable, Welch-bound ensembles minimizing intensity of the multiple access interference (MAI) are optimal. In this paper we show that for random signature sets the mean square deviation of MM power from the Welch bound drops in nearly inverse proportion with growth of K/N, where K is number of users and N is the spreading factor. Thereby, the fact of asymptotic (K/spl Gt/N) convergence in probability of random sets to the Welch-bound ones is demonstrated.