Unequal error protection for layered source coding using MIMO technology

Abstract

The use of multiple-input, multiple-output (MIMO) technology is proposed to provide unequal error protection (UEP) for layered source coding. Two priority layers are considered: a base (high priority (HP)) layer and an enhancement (low priority (LP)) layer. The MIMO is composed of two transmit antennas and two receive antennas. The HP bit stream is modulated by using four quadrature amplitude modulation (4-QAM) and the LP bit stream is modulated by using 16-QAM. The HP and the LP symbols are then coded by using a spatial-time block coding and multiplexed before transmission. The performance of the proposed system is compared with an equal error protection (EEP) system of 64-QAM and two transmit and two receive antennas. The EEP system uses spatial diversity in its MIMO to improve the decision reliability at the receiver. Both systems provide a similar capacity. The simulation results show a considerable improvement in performance for the UEP system over the EEP one.Introduction: The demand to increase the data rate of wireless systems to improve the quality of multimedia services is higher than ever. Source coding techniques are essential to reduce the bit stream to a range suitable for transmission. On the other hand, the coded bit stream becomes very sensitive to transmission errors, where a single error can propagate to many parts of the frame(s). Layered source coding can be used to stop the propagation of the errors. The bit stream is organised into several layers with different degrees of importance. Each layer improves the quality of the service gradually, when added to the decoded bit stream.Unequal error protection (UEP) can be combined with layered source coding to enhance the performance of the services and extend the services existence of a wide range of channel signal-to-noise ratio (SNR) [1]. Each source layer is proffered with a protection that suits its importance. The most significant layers will have a better protection than the least significant layers.Multiple-input, multiple-output (MIMO) technology can assist in the UEP process [2-4]. The MIMO system offers a substantial improvement over a single-input, single-output (SISO) system, by exploiting the spatial domain without an increase in the bandwidth. MIMO technology can be used to improve the capacity of the system (spatial multiplexing), where the transmit antennas send different symbols in a single time slot. MIMO can also be used to augment the quality of the services (spatial diversity), where multiple copies of a symbol are transmitted in a single time slot.In this research, we propose to join the modulation modes of different capacity and immunity levels with the spatial multiplexing of the MIMO to offer UEP to the source layers, without any prior knowledge to the channel at the transmitter. For practical consideration, two levels of priority are considered in this Letter; hence, the source coding layer produces a base layer (high priority (HP) layer) for the basic quality, and an enhancement layer (low priority (LP) layer) to enhance...

From source coding to MIMO - a multi-level unequal error protection

“…Unequal error protection (UEP) methods increase the reliability of systems by expanding the service over a wider range of channel signal-to-noise ratio (SNR) when compared to equal error protection (EEP) methods [3]. UEP can be implemented on several levels of the communication systems: on source coding level where many source layers with different importance are produced, on channel coding level using different coding rates for each priority layer, on modulation level with different modulation modes for the priority layers, and on transmission level using MIMO antennas, where better spatial channels are used for the important data.…”