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LTE network architecture
Radio part of LTE
Radio part of LTE
And radio optimisation ?
Important to know :
What should be observed ?
RSRP : Reference Signal Received Power
(only on reference signal)
and
RSSI : Received Signal Strength Indicator
(mean in overall band)
Why should we optimize ?
To improve network capacity (Mbits),
service delivery (Latency, mobility …) it
depends on operator strategy
1 – RACH ROOT SEQUENCE
RACH ROOTSEQUENCE is assigned to one cell
Prevent generation of same preambles in two
adjacent cells. Prevent false preamble detection.
Depends on Cell Range.
Table of association exists.
RACHROOTSEQUENCE = [0..837]
In this example Cell Range
is set to 15 km
10
20
30
40
40
50
10
ZC sequences that will be reserved : {40,41,42,43,44,45,46,47,48,49}
2 – PCI planification
Equivalent to SC in WCDMA (system point of view).
PCI confusion and collision should be avoided.
PCI = [0..503]
PCI = 3* value from S-SS + value from P-SS.
5
1
3
2
0
10
9
4
11
8
6
7
In case of TDD LTE, operators should prevent to assign the same “value from P-SS” in adjacent cells (Exemple : cells in the same site)
3 – Reduce overlapping zones
Due to the fact that in LTE we use the same
spectrum band “without” scrambling in adjacent
cells.
PUSCH and PUCCH in Uplink.
PDSCH and PDCCH in Downlink.
4 – Tuning nominal power
-Nominal power in PUCCH.
-Nominal power in PUSCH.
Those values can be tuned in each cell.
Those values are used by mobiles phones when
transmitting to the Operator’s antenna.
Higher values mean more interference in adjacent
cells.
Lowest values mean lower SINR -> lower throughput
5 – Cell reselection parameters
Mobile in idle mode.
Reselection is done when the mobile is moving
from one cell to another.
By reading MIB and SIBs
The mobile compares signals from cells with
thresholds and by adding hysteresis and offsets.
MIB and SIB Broadcasting MIB and SIB
Broadcasting
5 – Cell reselection parameters
MIB and SIB Broadcasting MIB and SIB
Broadcasting
6 – Tuning handover parameters
Those parameters are sent in RRC
Reconfiguration messages.
The operator has to tune those parameters to
ensure the mobile is being served by the best
cell.
Specific tuning in case oh high mobility (highway,
train …).
Prioritization per frequency, technology …
Serving Cell
Target Cell
6 – Tuning handover parameters
Parameters that should be tuned are related to
EVENTS = { A1, A2, A3, A4, A5 }
Thresholds, offsets …
Serving Cell
Target Cell
7 – SON Tuning (new)
SON : Self Organized Network
Intelligence to manage and adapt to network
change.
Example :
ANR : Automated Neighbor Relation
It enables to create and remove automatically
neighbor relations.