2. LITERATURE REVIEW
2.4. Dynamic recrystallization
2.4.6. Modelling of dynamic recrystallization
- Uplink power parameters are changed in order to decrease the interference and the service drop and enhance RRC rate.
Adjust UE Transmission to compensate for channel fading.
Reduces cell interference.
Avoid UE from transmitting excessive power.
Maximizes uplink data rate.
eNB radio receive Power maintained for optimum SINR.
Prolongs UE battery life.
There are two type of uplink power control - Open Loop power control
- Closed Loop Power Control
Open Loop Power Control
- The terminal transmits power depending upon estimate of downlink path loss and channel configuration.
- OL-PC is used for - PRACH and initial access
- PUSCH and PUCCH as part of power control.
- 𝐏𝐋(𝐏𝐔𝐒𝐂𝐇) = 𝒎𝒊𝒏{𝑷𝒎𝒂𝒙, 𝟏𝟎𝒍𝒐𝒈𝑴 + 𝑷𝒐𝒏𝒐𝒎𝒊𝒏𝒂𝒍(𝑷𝑼𝑺𝑪𝑯) + 𝜶. 𝑷𝑳 - Where M is number of PRB used by UE
- 𝑷𝒐𝑵𝒐𝒎𝒊𝒏𝒂𝒍 = 𝑻𝒂𝒓𝒈𝒆𝒕 𝑺𝑰𝑵𝑹 + 𝑻𝒐𝒕𝒂𝒍 𝑵𝒐𝒊𝒔𝒆 𝑷𝒐𝒘𝒆𝒓 - 𝑷𝑳= 𝑹𝑺− 𝑹𝑺𝑹𝑷
- As PRB increases, UE power increases.
- α = -8
Closed Loop Power Control
- It controls the terminal transmit power by means of power command in the downlink.
- PUSCH and PUCCH as part of power control of UL.
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48. RSRP, EPRE and Total Power
Some equipment would request you to specify the power in EPRE (power/15 Khz) and some equipment would request you to specify the total power (total power across all the allocated RBs).
Some of the most confusing power concepts are RSRP, EPRE and total power. Definition and Differences among these powers can be illustrated as follows. For the simplicity, I use the structure of only one RB and TM1 (Single Antenna)
Directly or indirectly from this illustrations, you can infer some additional facts as follows :
EPRE indicate power for one resource element (RE). This can be used for any channel (e.g, Reference Signal, PDSCH etc). This value does not vary with system bandwidth or number of RBs.
RSRP is an averaged value for all the Resource Elements for Reference Signal within a symbol. Since this is the averaged value, the value would be similar to EPRE value you set for the Reference Signal.
If there is no noise at all, RSRP would be same as EPRE you set for Reference Signal.
Total Channel Power is summed value of all EPREs within a symbol. This value may vary with different symbols since each symbol may have different channel combination (e.g, Symbol 0 in first slot is made up of multiple component - PCFICH, HICH, RS. Symbol 4 is made up of PDSCH and Reference signal).
For simplicity, if we take the symbol which is made up of only PDSCH (e.g, Symbol 3,5,6) we may come out with the following formula. For different symbols, you may have a little bit different values depending on P-a, P-b configurations. But you can apply this formula for other symbols if you can tolerate around +/- 1dB differences.
Total Power of PDSCH (in linear scale )
= EPRE for PDSCH x Number of PDSCH RE
= EPRE for PDSCH x Number of RB x 12 (assuming for the symbol with no Reference Signal)
Total Power of PDSCH (in dB/dBm scale )
= EPRE for PDSCH (in dBm) + 10 Log(Number of PDSCH RE)
= EPRE for PDSCH + 10 Log(Number of RB x 12)
Total Power is not affected by the system bandwidth, it is affected by number of RBs being used at the specific moment of the calculation.
For example, if you allocated -90 dBm/EPRE for PDSCH and allocated 100 RBs for the PDSCH, the Total Power of PDSCH become as follows.
Total Power of PDSCH (in dB/dBm scale )
= EPRE for PDSCH + 10 Log(Number of RB x 12)
= -90 + 10 Log(100 x 12)
= -90 + 30.8
= - 59.2 dBm
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49. GPRS Tunnelling Protocol
GTP – GPRS Tunnelling Protocol in LTE:
- GTP is a tunnelling protocol based on IP/UDP.
- It is used to encapsulate user data when passing through the core network.
3 types of GTP:
- GTP-C - GTP-U - GTP’
Why GTP is used in LTE?
- It provides mobility
- When UE is mobile, IP address remains same packets are still forwarded since the tunnelling is provided between P-GW and eNB via S-GW.
- Multiple tunnels can be used by same UE to obtain different QoS.
- Main IP is hidden, so it provides more security.
- Creation, establishment, modification and termination of tunnels in case of GTP-C.
50. RRC
- According to the 3GPP functions, the RRC protocol includes the following main functions.
- Broadcast of system information:
- > Including NAS common information
- > Information applicable for UE in RRC_Connected (common channel configuration information) - >Information applicable for UE in RRC_Idle (cell reselection parameters, neighbouring cells) - Including ETWS notification
- RRC Connection Control:
- Paging
- Establishment, modification and release of RRC connection, including assignment, modification of UE, release of SRB1; SRB 2
- Initial Security activation – initial configuration of AS integrity (SRB) and AS ciphering
- RRC connection mobility including intra-frequency and inter-frequency handover, associated security handling, ie… key/algorithm change, specification of RRC context information transferred between network nodes.
- Establishment/ modification and release of RB carrying user data (DRB)
- Radio configuration control, including assignment/ modification of ARQ configuration, HARQ configuration and DRX configuration.
- QoS control including assignment/modification of parameters for UL rate control in the UE. (allocation of priority and Prioritized bit rate PBR)
- Recovery from Radio link failure.
- Inter RAT mobility including security activation, transfer of RRC context information.
- Measurement configuration and Reporting
- Establishment/modification/ release of measurements (Intra frequency, inter frequency and interRAT measurements)
- Setup and release of measurement gaps.
- Measurement reporting
- Other functions like transfer of dedicated NAS and non 3GPP dedicated information, transfer of UE radio access capability information.
- Generic protocol error handling
- Support for self configuration and self optimization.
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