Krishnan Rajamani

Scalable PLCP header extension within PSDU

Next generation UWB design needs additional header information fields than present in current ECMA-368 specification. However extending the ECMA-368 header beyond the available reserved bits while being compatible with legacy devices is a challenge. In this paper, we propose a scalable Physical Layer Convergence Protocol (PLCP) header extension within the Physical Layer Service Data Unit (PSDU) that allows for header extension beyond the reserved bits. The proposed mechanism also attempts to opportunistically convey the additional header information utilizing the padding bits present in the PSDU.

Compression schemes for the feedback channel in multiband-OFDM UWB systems

In time-varying channels, channel state information (CSI) is often provided via a feedback channel to facilitate dynamic allocation of resources like transmit power and data rates. In OFDM-based ultra wideband (UWB) channels, the signaling overhead for this CSI feedback can be extremely large. In this paper, we propose several compression schemes for the feedback channel that exploit the temporal and spatial correlation properties of the multiband-OFDM UWB channel, viz., fixed and variable spectral binning techniques, hierarchical binary tree-based spectral compression schemes, and Markov state-based differential temporal compression schemes.

MAC performance for second generation UWB

Next generation UWB design needs higher data rates than those proposed by ECMA-368 in order to be competitive. This paper investigates ECMA-368 MAC performance for extended data rates. It is shown that throughput improves at these extended PHY rates, when PHY frame size (L) is increased to 8190 octets under reasonable BER values. This improvement is a function of the transfer size. L=8190 octets exhibits >16% (>100 Mbps) improvement over L=4095 octets, for large transfers (>65 K octets). This is a worthwhile change since doubling PHY frame size imposes minor incremental complexity relative to the overall effort to support the extended PHY rates. It is shown also that scaling L does not improve throughput for bad channels (PER>12% normalized to 4095 octet payload). To maintain higher throughput under bad channel conditions, we need the ability to increase L without increasing PER. This can be achieved by packing multiple MPDUs into a single PSDU, each with its own frame check sum. This reduces PER by making it a function of the MPDU size and not PHY frame size. Complex MAC changes are needed for such a scheme. Fortunately, this scheme is only needed under bad channel conditions which are not suitable for extended data rates to start with.

Extended data rates for next generation UWB

For UWB to be a competitive solution, its next generation design must support higher data rates than those proposed by ECMA 368. The purpose of this paper is to investigate methods to double the UWB current maximum data rate. The options considered are 16-QAM and bandwidth expansion. The potential solutions to double the data rates are compared in terms of system performance. Three metrics are used as figure of merit for such comparison.