LTE FDD optimization
Abdelaziz Hamzaoui
[email protected]
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]
ZC sequences that will be reserved : {40,41,42,43,44,45,46,47,48,49}
40 20
10
In this example Cell Range is set to 15 km
40 30
10 50
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.
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)
6 7
0
1 8
2 3
4
9 10
5
11
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.
