Design of diversity-achieving LDPC codes for H-ARQ with cross-packet channel coding

Abstract

Abstract-In wireless scenarios an effective protocol to increase the reliability for time-varying channels is the hybrid automatic repeat request (H-ARQ). The H-ARQ scheme with cross-packet channel coding (CPC) is a recently published extension of H-ARQ with several advantages. No full-diversity low-density paritycheck (LDPC) code design for the whole range of coding rates yielding full-diversity has been published. In this paper the authors provide a new outage behavior analysis and a new structured LDPC code ensemble achieving full-diversity for H-ARQ with CPC by exploiting the rootcheck principle. Simulation results show that the new code design outperforms the previous approaches, providing full-diversity and good coding gain, also at high coding rates.

Precoding for Outage Probability Minimization on Block Fading Channels

“…More sophisticated constellations can also be considered. For example, 16-can be constructed by considering five sets of three constellation points 9 for , and adding a constellation point located on the bisector. To build the actual constellations, a few design parameters have to be specified, such as the distances between the planes perpendicular to the bisector, the radii of the circles containing three points of the constellation in the planes, how many points on the bisector are taken and how many points in groups of three are taken.…”

“…Besides the theoretical relevance, the numerical results suggest a practical relevance because the impact of this optimization on the outage probability 9 The three constellation points are in a plane perpendicular to the bisector. is significant in the case of large coding rates .…”

“…However, more insight can be gained when considering . From (9), it is clear that for a certain fading point, the mutual information of this virtual channel, with input , is the same as the mutual information of the actual channel, with input ,…”

“…Considering , an equivalent channel model can be formulated (9) which yields more insight and will be useful in the proofs of propositions of this paper. This system model represents a Gaussian vector channel with input .…”

“…I N many applications, using techniques such as frequency-hopping (GSM, EDGE), time-interleaving (DVB-T), OFDMA (WiMax and LTE), H-ARQ with cross-packet coding [18], [9], and cooperative communications [31], [32], [22], [8], the channel can be modeled as a flat block fading (BF) channel [3], where the fading gain is piecewise constant over the duration of a transmitted packet. Due to motion of the transmitter, receiver, or objects between the transmitter and receiver, the fading gains vary from one packet to the next and are considered unknown at the transmitter side.…”