Stan Baggen

Union bounds on the performance of product codes

We estimate the weight enumerator of a product code by using an exact expression for its known terms (e.g., the number of low weight words), and a binomial approximation for its unknown terms. We subsequently apply a union bound, using the estimated weight enumerator, to large product codes. The computed union bounds are similar to the simulation results of iterative (turbo) decoding of such codes as reported in literature.

An example of a multi-resolution digital terrestrial TV modem

An example of a modem for two-resolution digital terrestrial transmission, providing two programs in a single 8 MHz channel is described. For each program, it is desired to transmit 5 Mb/s to portable receivers and additionally 5 Mb/s to fixed receivers. In the example, orthogonal frequency division multiplexing (OFDM) is used with guard intervals as in digital audio broadcasting. The two-resolution transmission is achieved by using a two-resolution quadrature amplitude modulation (QAM) signal constellation. Reed-Solomon coding gives burst error correction capability to combat the frequency selective nature of the transmission channel. The two-resolution system can easily be reconfigured into a compatible system, providing high-definition television to fixed receivers.<<ETX>>

Joint illumination and visible-Light Communication systems: Data rates and extra power consumption

Visible Light Communications (VLC) have been promoted as an energy-efficient Gb/s-technology for indoor settings, since VLC can be merged with the illumination functionality. As a result, Joint Illumination and visible-light Communication (JIC) systems are perceived as a green technology and the research on VLC mainly focuses on increasing the data rates. In this paper, we demonstrate that the communication functionality of JIC systems comes always with an extra power consumption compared to illumination-only systems due to fundamental limitations in the LED sources operation. Furthermore, our analysis shows that apart from the LED sources, the extra power consumption of JIC systems depends on the illumination pattern and the JIC drivers. Finally, by examining jointly the maximum transmission rates (communication capacity) of JIC systems and their power consumption, we are able to judge their power efficiency compared to other competing technologies and determine potential application areas.

Doppler Compensation by Using Dual Antenna for Mobile OFDM Systems

The performance of OFDM systems is compromised in mobile environments due to Doppler spreading. In this paper, we investigate how Doppler spreading due to the mobility of the receiver can be mitigated by using dual antenna. In this context, we propose two simple antenna combining schemes, namely, simple beamforming (SB) and beamforming with frequency offset correction (BFOC), and investigate the ICI mitigating capability of these methods. We show that by using appropriate antenna spacing, beamforming coefficients and frequency offset correction, the performance of the OFDM systems can be greatly improved in high mobility scenarios.

Optimum diversity combining techniques for visible light communication systems

Visible Light Communication (VLC) systems often provide wavelength diversity by using white LED sources as transmitters or spatial diversity by simultaneous transmission from multiple LEDs. This paper focuses on optimum diversity combining techniques for VLC systems employing intensity modulation/direct detection (IM/DD) with binary signaling. VLC systems can combine the signals from separate channels with the use of optical filters and special optics either in the optical domain using one photodetector only, or in the electrical domain by allocating a dedicated photodetector per channel. We show that, in the case of optical combining, maximization of the SNR is achieved by a fundamentally different solution compared to the well-known maximal-ratio combining (MRC) in wireless radio. In the case of electrical combining, the classic MRC solution remains optimum. Finally, when photon noise is dominant, it is proven that optimum combining in the electrical domain outperforms combining in the optical domain for the same light input.

Blind Estimation of Maximum Delay Spread in OFDM Systems

We present a new method of estimating the maximum delay spread of a channel in an OFDM system. The method differs from other approaches because it uses all active OFDM subcarriers (pilot and data) and therefore avoids the aliasing problem arising from the exclusive usage of pilot subcarriers. The method considers the transmitted data as a random probe signal for obtaining characteristics of a channel. Although the data content is not known at the receiver, it turns out that useful second order statistics can be extracted, from which the maximum delay spread is estimated. The method is shown to be robust to noise and Doppler spread.

Informed Decoding in an Address Format

When a jump is made while reading from an (optical) disc, prior information about the address on the landing position is known. When the address information is protected by a systematic Reed Solomon error correcting code, this prior information does not give an increased error correction capacity. If, however, informed decoding Reed Solomon encoding is used, the information does give an increased error correction capacity. Only some simple post processing has to be added to the decoding path in that case. One can benefit from this encoding method with a simple check after decoding.

Automatic switch between static and mobile operation modes in DVB-T/H receivers

In wireless communications, the receivers have to work properly both in the mobile and static environments. A proper solution might require the development of two parallel receivers modes. In this paper we propose an automatic switch between these two receiver modes. The automatic switch estimates a decision variable based on the temporal correlation of the channel frequency response. Then, it compares the decision variable with a pre-calculated threshold to decide which is the best receiver mode

An efficient algorithm for estimating the state sequence of a finite state machine given an output sequence

We consider the problem of sequentially estimating the states of non-unifilar finite state machines on the basis of the output symbols of the machine and show that a Fano-type inequality can be effectively used as a stopping criterion. Lower and upper bounds on the decoding error probability are given.