A single PRB is considered the smallest unit in a LTE frame. A single PRB is allocated
LTE RADIO
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of sub-carriers and symbols. A single PRB consists of 12 sub-carriers grouped together.
A single PRB has 6 or 7 symbols depending upon the CP length.
Figure 3.5: LTE frame structure
Table 3.1: Resource block configuration in EUTRAN channel bandwidths
Channel bandwidth (MHz)
1.4
3
5
10
15
20
Number of resource blocks
6
15
25
50
75
100
Figure 3.5 shows the LTE frame structure. A single PRB is referred as a slot in the LTE
frame. Two slots make a sub-frame with duration of 1 ms. 20 PRBs form a single frame
and is 10 ms long. The frame structure is same for the downlink (OFDMA) and the up-
link (SC-FDMA). Reference symbols are used for the channel estimation. The reference
symbols are placed with specific pattern in the PRBs for the efficient channel estima-
tion. Table 3.1 shows the standard list of resource block configuration for different al-
lowable bandwidths in LTE. [10]
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