HARQ design for high performance wireless backhaul

#Embodiments of the present invention relate to wireless communication systems and, more particularly, to low overhead control signaling of a Non-Line-Of-Sight (NLOS) wireless communication system compatible with a time-division duplex long term evolution (TD-LTE) Radio Access Network (RAN).

#A key answer to the huge data demand increase in cellular networks is the deployment of small cells providing Long Term Evolution (LTE) connectivity to a smaller number of users than the number of users typically served by a macro cell. This allows both providing larger transmission/reception resource opportunities to users as well as offloading the macro network. However, although the technical challenges of the Radio Access Network (RAN) of small cells have been the focus of considerable standardization effort through 3GPP releases 10-12, little attention was given to the backhaul counterpart. It is a difficult technological challenge, especially for outdoor small cell deployment where wired backhaul is usually not available. This is often due to the non-conventional locations of small cell sites such as lamp posts, road signs, bus shelters, etc., in which case wireless backhaul is the most practical solution.

#The LTE wireless access technology, also known as Evolved Universal Terrestrial Radio Access Network (E-UTRAN), was standardized by the 3GPP working groups. OFDMA and SC-FDMA (single carrier FDMA) access schemes were chosen for the DL and UL of E-UTRAN, respectively. User equipments (UEs) are time and frequency multiplexed on a physical uplink shared channel (PUSCH) and a physical uplink control channel (PUCCH), and time and frequency synchronization between UEs guarantees optimal intra-cell orthogonality. The LTE air-interface provides the best spectral-efficiency and cost trade-off of recent cellular networks standards, and as such, has been vastly adopted by operators as the unique 4G technology for the Radio Access Network (RAN), making it a robust and proven technology. As the tendency in the RAN topology is to increase the cell density by adding small cells in the vicinity of a legacy macro cells, the associated backhaul link density increases accordingly and the difference between RAN and backhaul wireless channels also decreases. This also calls for a point-to-multipoint (P2MP) backhaul topology. As a result, conventional wireless backhaul systems typically employing single carrier waveforms with time-domain equalization (TDE) techniques at the receiver become less practical in these environments. This is primarily due to their limitation of operating in point-to-point line-of-sight (LOS) channels in the 6-42 GHz microwave frequency band. On the contrary, the similarities between the small cell backhaul and small cell access topologies (P2MP) and wireless radio channel (NLOS) naturally lead to use a very similar air interface.

#FIG. 1 is a diagram of a wireless communication system with a cellular macro site hosting a backhaul point to multipoint (P2MP) hub unit (HU) serving plural remote units (RUs) which relay communications between small cells and plural user equipment (UE);

#FIG. 2 is a diagram of downlink and uplink subframe configurations according to the present invention;

#FIG. 3 is a diagram of a subset of downlink and uplink subframe configurations of the prior art;

#Some of the following abbreviations are used throughout the instant specification. The following glossary provides an alphabetical explanation of these abbreviations.

#BLER: Block Error Rate

#CQI: Channel Quality Indicator