In the waterfall below we can see a PHICH transmission. In the extended duration the 3 REGs are distributed over the first 2 or 3 symbols of the subframe. In the normal duration, the 3 REGs are transmitted simultaneously in the first symbol of the subframe. Here we will only look at the normal PHICH duration, which is what is used in the recording. Depending on the configuration of a parameter called PHICH duration, the PHICH can either use the first symbol in each subframe (normal PHICH duration), or the first 2 or 3 symbols in each subframe (extended PHICH duration). This is similar to the PCFICH, which uses 4 equally spaced REGs in the first symbol of the subframe. In symbols 2 and 3 there may not be resource elements allocated to the CRS, so there are 3 REGs per resource block in that case.Ī PHICH transmission uses 3 REGs which are equally spaced over the bandwidth of the cell, in order to give frequency diversity. Therefore, there are 2 REGs per resource block. The other 4 resource elements form a REG. For instance, when 2 or 4 antenna ports are used for the CRS, in the first symbol of the subframe two resource elements in every block of 6 are used for the CRS. Recall that a REG is a set of 4 resource elements which are not used for the transmission of the CRS and which are adjacent in frequency if we ignore the resource elements used for the CRS. As other control channels, the PHICH uses REGs. The PHICH is transmitted in the control region of the subframe, which is formed by the first 1, 2, or 3 symbols of the subframe (according to the CFI value). Repetition encoding is used to increase the chances of correct decoding, and an orthogonal overlay code allows transmitting information for several UEs using the same resource elements. Each PHICH transmission carries a single bit, either ACK (encoded by the bit 1) or NACK (encoded by the bit 0). The PHICH is used to send hybrid-ARQ ACK/NACKs to the UEs. As usual, I will be analysing the recording of a base station that I did in the first post about the LTE downlink. In this post we will look at the PHICH (physical hybrid ARQ indicator channel). In the previous post we looked at the downlink cell-specific reference signals (CRS), transmit diversity equalization, and the demodulation of the PBCH (physical broadcast channel), PCFICH (physical control format indicator channel) and PDSCH (physical downlink shared channel). A licensed downlink station is required to meet strict technical standards with respect to site location, elevation angle, and antenna directivity.This is a continuation of my series of posts about LTE. There are four rules that address the interference problem: site requirements, power limits, minimum elevation angle and antenna directivity. The principal technical rules governing the operation of uplink earth stations have the purpose of minimizing interference to microwave receiving stations operating in the C band, 5925 to 6425 MHz. The chapter focuses on FCC Rules and procedures governing the installation and technical operation of uplink and downlink earth stations. The International Telecommunications Union governs radio services on an international level. The regulation of satellite communications also requires international agreement. Abstract: The Federal Communications Commission (FCC) was established by the Communications Act of 1934, which gave it very broad authority to regulate interstate wired and wireless communications within the United States.
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