Apparatus for measuring EVM of PHICH in LTE system
An apparatus for efficiently and simply measuring an error vector magnitude (EVM) of a physical hybrid automatic repeat request (ARQ) indicator channel (PHICH) in a long term evolution (LTE) system. The apparatus includes an overall PHICH group data extraction unit configured to extract all PHICH group data from a received signal in a first subframe, an overall PHICH group analysis unit configured to detect orthogonal sequences and acknowledgement/negative acknowledgement (ACK/NACK) bits used in respective PHICH groups by analyzing all resources of the extracted PHICH group data, an ideal PHICH group sequence generation unit configured to generate an ideal PHICH group sequence using the detected ACK/NACK bits and orthogonal sequences, and an EVM measurement unit configured to measure an EVM of a PHICH using the ideal PHICH group sequence and the received signal.
1. An apparatus for measuring an error vector magnitude (EVM) of a physical hybrid automatic repeat request (ARQ) indicator channel (PHICH) in a long term evolution (LTE) system, the apparatus comprising:
an overall PHICH group data extraction unit, wherein the overall PHICH group data extraction unit extracts all PHICH group data from a received signal in a first subframe;
an overall PHICH group analysis unit, wherein the overall PHICH group analysis unit detects orthogonal sequences and acknowledgement/negative acknowledgement (ACK/NACK) bits used in respective PHICH groups by analyzing all resources of the extracted PHICH group data;
an ideal PHICH group sequence generation unit, wherein the ideal PHICH group sequence generation unit generates an ideal PHICH group sequence using the detected ACK/NACK bits and orthogonal sequences; and
an EVM measurement unit, wherein the EVM measurement unit measures an EVM of a PHICH using the ideal PHICH group sequence and the received signal.
2. The apparatus of claim 1 , wherein the overall PHICH group analysis unit de-precodes, de-layer-maps, and descrambles the extracted PHICH group data, de-spreads the descrambled PHICH group data using a plurality of orthogonal codes according to each group, detects the orthogonal sequences currently in use through correlation values between the de-spread data and the respective orthogonal sequences, and determines the ACK/NACK bits for the detected orthogonal sequences.
3. The apparatus of claim 1 , wherein the ideal PHICH group sequence generation unit generates a plurality of bits by repeating an ACK/NACK bit of each PHICH group a plurality of times, binary phase shift keying (BPSK) modulates the generated bits, multiplies the BPSK-modulated bits by an orthogonal sequence currently in use, scrambles the BPSK-modulated bits, layer-maps and precodes the scrambled PHICH symbol data, and generates the one ideal PHICH group sequence by summing all the precoded PHICH data.
4. The apparatus of claim 1 , further comprising a channel equalization unit, wherein the channel equalization unit removes noise included in the received signal, and wherein the EVM measurement unit measures the PHICH EVM by inserting the received signal processed through the channel equalization unit and the ideal PHICH group sequence into
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where T denotes a symbol set in a subframe, F(t) denotes a subcarrier set in a symbol t, I(f, t) denotes an ideal transmitted signal at a subcarrier f of the generated symbol t, and Z eq (f, t) denotes the received signal.