PRB

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One physical resource block (PRB) spans 12 subcarriers, which with the 15-kHz subcarrier spacing correspond to 180 kHz. When full-PRB transmission is used, the smallest time-frequency resource that can be scheduled to a device is one PRB pair mapped over two slots, which for the normal CP length case (with 7 OFDM symbols per slot) corresponds to 12 subcarriers over 14 OFDM symbols as illustrated in Figure below:

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https://www.researchgate.net/profile/Wibowo_Hardjawana/publication/283667343/figure/fig1/AS:300550831788034@1448668310460/LTE-A-uplink-physical-resources.png

A resource block (RB) is the smallest unit of resources that can be allocated to a user. The resource block is 180 kHz
wide in frequency and 1 slot long in time. In frequency,  resource
blocks are either 12 x 15 kHz subcarriers or 24 x 7.5 kHz subcarriers
wide The number of subcarriers used per resource block for most channels
and signals is 12 subcarriers.

For a full LTE overview plaese refer to:

http://rfmw.em.keysight.com/wireless/helpfiles/89600b/webhelp/subsystems/lte/content/lte_overview.htm

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Hi
It is called PRB (Physical Resource Block), at minimum or information element that it can be assigned by the eNB to a mobile terminal. A PRB occupies 180 KHz of band equivalent to 12 subcarriers equi-spaced 15K Hz between them and in it 6 or 7 are transmitted OFDMA symbols, depending on the length of the cyclic prefix. The duration of a PRB is 0.5 ms, that is, the duration of a slot or time slot.
The number ro of subcarriers is 12 times the number of PRBs plus one, since the subp is considered central ortadora (that of DC) that does not used to transmit information.
In a PRB we have 7 symbols with 12 subcarriers associated with each of them, so we have a total of 84 resources where to enter the symbols QPSK, 16-QAM and 64- QAM. Considering the modulation with the highest spectral efficiency, 64-QAM in which transmit 6 bits / symbol, within a PRB we can send a total of 504 bits every 0.5 ms, which gives us a gross peak transmission speed of approximately R b, PRB = 504 bits / 0.5 ms ≈ 1 Mb / s.

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