LTE Innovation Mining: Down Link Reference Signals Essential Patent (1)

Patent application publication US20060285484,entitled Pilot Design and Channel Estimation, is a candidate for LTE DL RSs essential patent.

BACKGROUND

In an OFDM (Orthogonal Frequency Division Multiplexing) based communication system, pilot symbols are transmitted in addition to data symbols to provide a reference for the receiver to estimate the channel medium and accordingly demodulate the received signal. OFDM systems periodically insert reference (or pilot) symbols that are known a priori, into the transmission signal. The receiver can thus estimate the channel response based on the received pilot symbols and the known transmitted pilot symbols. A pilot signal also referred to as reference signal is composed of the pilot symbols.

The DL pilot signal should provide effective performance for the following functions: Channel estimation at all possible operating carrier frequencies for all physical channels for all channel multi-path delay spreads (frequency selectivity) encountered in practice and for all UE speeds of interest; CQI measurement for link adaptation and channel-dependent scheduling; Sector identification of sector within the same cell; Measurements for cell search and handover.

PRIOR ART

Channel estimation is based on time and frequency interpolation among pilot sub-carriers in order to obtain the channel estimates at the position corresponding to data sub-carriers. In order to be able to perform frequency interpolation, the pilot sub-carrier spacing in the frequency domain should be smaller than the 50% correlation coherence bandwidth of the channel for all channels of interest. Similarly, in order to be able to perform time interpolation, the pilot sub-carrier spacing in the time domain should be smaller than the 50% coherence time of the channel at the operating carrier frequency for all UE speeds of interest.

There is a need for an improved pilot structure design in the prior arts in order to achieve accurate channel estimates for high user equipment (UE) speeds in mobile operations while also achieve the ability to use substantial pilot energy from succeeding TTI (Transmission Time Interval) with minimum latency.

INVENTION

Embodiments of the invention provide method and apparatus for generating a structure in a OFDM communication system having a transmitter with a least one transmitting antenna to achieve accurate channel estimates for high UE speeds and high channel frequency selectivity in mobile operations.

CLAIM

2. The method of claim 1 wherein the transmission time interval comprises of seven orthogonal frequency division multiplexing symbols and wherein the pilot signal from at least one transmitting antenna is located in the first and fifth OFDM symbols of a transmission time interval:

DL RSs specification for single antenna port in 3GPP TS36.211, V890, Section 6.10.12 & Figs 6.101.2-1

3. The method of claim 2, wherein the transmitter has at least two antennas, said method further comprising: locating a pilot signal from a second antenna into two orthogonal frequency division multiplexing symbols of said frame such that the pilot power of the pilot signal from the second antenna is in the first and fifth orthogonal frequency division multiplexing symbols of the transmission time interval:

DL RSs specification for two antenna ports in 3GPP TS36.211, V890, Section 6.10.12 & Figs 6.101.2-1

6. The method of claim 3, wherein the transmitter has at least four antennas, said method further comprising: locating a pilot signal from a third antenna into two orthogonal frequency division multiplexing symbols of said frame such that the pilot power of the pilot signal from the third antenna is in the second and sixth orthogonal frequency division multiplexing symbols of the transmission time interval; and locating a pilot signal from a fourth antenna into two orthogonal frequency division multiplexing symbols of said frame such that the pilot power of the pilot signal from the fourth antenna is in the second and sixth orthogonal frequency division multiplexing symbols of the transmission time interval:

DL RSs specification for four antenna ports in 3GPP TS36.211, V890, Section 6.10.12 & Figs 6.101.2-1


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