2. RSRP
• RSRP :- Reference signal receive power.
•RSRP (dBm) = RSSI (dBm) -10*log (12*N)
where RSSI = Received Signal Strength Indicator
N: number of RBs across the RSSI is measured and depends on the
BW
• Significance : - RSRP is the most basic of the UE physical layer
measurements and is the linear average power (in watts) of the downlink
reference signals (RS) across the channel bandwidth for the Resource elements
that carry cell specific Reference Signals. Knowledge of absolute RSRP provides
the UE with essential information about the strength of cells from which path
loss can be calculated and used in the algorithms for determining the optimum
power settings for operating the network. Reference signal receive power is
used both in idle and connected states
• Range :- -44 to -140 dBm
• RSRP term is used for coverage same as RSCP in 3G.
4. RSRQ
• RSRQ :- Reference signal receive quality.
RSRQ = RSRP / (RSSI / N)
N is the number of resource blocks over which the RSSI is measured
RSSI is wide band power, including intra cell power, interference and
noise.
• Significance :- It provides the Indication of Signal Quality . Measuring RSRQ
becomes particularly important near the cell edge when decisions need to be
made, regardless of absolute RSRP, to perform a handover to the next cell.
Reference signal receive quality is used only during connected states
•Range :- -3 to -19.5 dB
• RSRQ term is used for Quality same as Ec/No in 3G.
6. SINR
• SINR :- Signal to Noise Ratio.
SINR = S / I + N
S -- Average Received Signal Power
I -- Average Interference power
N -- Noise Power
• Significance : Is a way to measure the Quality of LTE Wireless Connections. As the
energy of signal fades with distance i.e Path Loss due to environmental
parameters ( e.g. background noise , interfering strength of other simultaneous
transmission)
Radio Conditions for SINR Measurement
8. RSSI
• RSSI :- Received Signal Strength Indicator.
• RSSI = wideband power = noise + serving cell power + interference power
• RSSI=12*N*RSRP
• RSSI per resource block is measured over 12 resource elements.
N: number of RBs across the RSSI is measured and depends on the BW
Based on the above:
RSRP (dBm) = RSSI (dBm) -10*log (12*N)
• Significance – Is the parameter represents the entire received power including
the wanted power from the serving cell as well as all the co channel power &
other sources of noise
10. CQI
• CQI :- Channel Quality Indicator.
• Range :- 1 to 15
Significance: CQI is a measurement of the communication quality of wireless
channels i.e. it indicates the downlink mobile radio channel quality as experienced
by the UE .CQI can be a value representing a measure of channel quality for a
given channel. Typically, a high value CQI is indicative of a channel with high
quality and vice versa.
• CQI is measured in the Dedicated mode only.
•CQI depends on the RF conditions.
• Better the CQI better the throughput will get and vice versa.
12. PCI
• PCI :- Physical Cell Id
• Range :- 0 to 503
• Significance - PCI used to identify the cell & is used to transmit the data
• PCI = PSS + 3*SSS
PSS is Primary Synchronization Signal ( Identifies Cell Id ).
PSS value can be 0, 1 & 2
SSS is Secondary Synchronization Signal ( identifies Cell Id
group).
SSS value can be 0 to 167.
There is no standard way for planning of PCIs but there are some guidelines.
• Co‐PCI assignment for close sites needs to be avoided
• Sectors on the same eNode B should have the same SSS code but different PSS (assuming three sectored sites).
This is not mandatory but helps synchronization of UEs and improves traceability of the PCI assignment.
• Co‐PCI assignment for the neighbors needs to be avoided. If the neighbors are Co‐PCI, the handover process
may fail. Also, this is the trickiest requirement. (We will be adding an analysis in the LTE toolbox that evaluates
the PCI assignment and detects this condition)
• It is common to allocate a separate set of PCIs for outdoor cells and indoor cells. The reason is again
management of the PCIs and the fact that indoor cells are rarely tri‐sectored. They are usually deployed in
variety of antenna configurations.
14. BLER
• BLER :- Block Error Rate
•Block Error Ratio is defined as the ratio of the number of erroneous blocks
received to the total number of blocks transmitted.
Significance - A simple method by which a UE can choose an appropriate CQI
value could be based on a set of Block Error Rate (BLER) thresholds . The UE would
report the CQI value corresponding to the Modulation Coding Schemes that
ensures BLER ≤ 10% based on the measured received signal quality
• BLER is Calculated using Cyclic Redundancy error Checking method
High BLER leads to loss of Peak rates & efficiency
•BLER threshold should be low i.e. ≤ 10%
15. Throughput
Downlink Throughput
-In E-UTRAN may use a maximum of 2 Tx antennas at the ENodeB and
2 Rx antennas at the UE ( MIMO ).
Significance - Target for averaged user throughput per MHz, 3 to 4 times
Release 6 HSDPA i.e Higher user throughput as compared to 3G ( Over
300 Mbps downlink as compared to 14 Mbps in UMTS)
- The supported user throughput should scale with the spectrum
bandwidth.
16. Uplink Throughput
-In E-UTRAN uses a maximum of a single Tx antenna at the UE and 2 Rx
antennas at the E Node B.
- Greater user throughput should be achievable using multiple Tx
antennas at the UE ( MIMO )
.
- Significance- Target for averaged user throughput per MHz, 2 to 3 times
Release 6 Enhanced Uplink i.e Higher user throughput as compared to 3G
(Over 50 Mbps Uplink as compared to 5.76 Mbps in UMTS)
- The user throughput should scale with the spectrum bandwidth
provided that the maximum transmit power is also scaled.
17. Latency
• Reduced transit times for user packets (reduced latency), an order of
magnitude shorter than that can be provided in 3G networks (i.e. the user
plane -data latency will be lower than 10ms and under 100 ms for control
plane -signaling)
• Significance - Low delay/latency due to fewer Nodes , Shorter TTI , Shorter
Messages & quicker node response leads to more efficient use of radio
spectrum & Higher Capacity
• Control plane deals with signaling and control functions, while user plane
deals with actual user data transmission
18. User Plane Latency - U-Plane latency is defined as one-way transmit time
between a packet being available at the IP layer in the UE/E-UTRAN (Evolved UMTS
Terrestrial Radio Access Network) edge node and the availability of this packet at the
IP layer in the EUTRAN/ UE node. U-Plane latency is relevant for the performance of
many applications
Control Plane Latency -C-Plane latency is measured as the time required for
the UE (UserEquipment) to transit from idle state to active state. In idle state,
the UE does not have an RRCconnection. Once the RRC is setup, the UE
transitions to connected state and then to the active state when it enters the
dedicated mode
19. Tracking Area Code
Tracking Area (TA)
It is the successor of location and routing areas from 2G/3G.
When a UE attached is to the network, the MME will know
the UE’s position on tracking area level which is then stored
in the HSS database. In case the UE has to be paged, this
will be done in the full tracking area.
Tracking areas are identified by a Tracking Area Identity
(TAI).
TAI is constructed from the MCC, MNC, and TAC (Tracking
Area Code)
A Tracking Area (TA) includes one or several E-UTRAN cells
20.
21.
22. Timing Advance
The time it takes for the radio signal to travel from the UE to
the eNB’s receiver across the radio interface. Thus, it is equivalent to the
distance between the UE and the cell’s antenna
Significance - When UE wish to establish RRC connection with eNB, it transmits a
Random Access Preamble, eNB estimates the transmission timing of the terminal
based on this. Now eNB transmits a Random Access Response which consists of
timing advance command, based on that UE adjusts the terminal transmit timing.
The timing advance is initiated from E-UTRAN with MAC message that implies and
adjustment of the timing advance.
Why timing advance??
• Because the UL resources are orthogonal and this fact has to be
maintained
• Different UEs in the cell may have different position and therefore
different propagation delay ‐> this may affect synchronization
• Only UL timing advance no DL
• In DL possible to manage synchronized transmission to several UEs
23. TA Requirements
•Timing Advance adjustment delay
The UE shall adjust the timing of its uplink transmission timing at
sub- frame n+6 for a timing advancement command received in
sub- frame n.
•Timing Advance adjustment accuracy
The UE shall adjust the timing of its transmissions with a relative
accuracy better than or equal to ±4* TS seconds to the signaled
timing advance value compared to the timing of preceding uplink
transmission. The timing advance command is expressed in
multiples of 16* TS and is relative to the current uplink timing.
24.
25. Timing Advance
• How often ‐> what is the frequency of Timing Advance?
– Granularity of 0,52us corresponding to 78 m
– Dependent on the UE speed:
– 1. E.g. 72 km/h = 20 m/s
– ‐> 78 m in approx 4 s
– ‐> an update every 4 seconds
– 2. E.g. 500 km/h = 130 m/s
– 78 m approx 2 times per second
– ‐> Maximum of 2 updates per second
• How is the Node‐B measuring the TA?
• Based on received PUSCH on TTI basis
• CQI reports on PUCCH
• How is the timing advance signaled to the UE??
• At MAC layer (peer to peer signaling)
26. Tx Power
The power (dBm) used by the UE to send the physical UL signal toward the eNB( As
per UE power Classes).
In LTE , The eNB is in charge of control of the UL TX power of the UE .i.e. power control
of UE.
The only measurement sent by the UE using a RRC measurement report is the UE Tx
power.
UE utilizes its Tx power as per the Power control Commands given by eNB for better
capacity & power Consumption .
Two Types of Power Control Schemes are Implemented
- Open Loop Power control
- Closed Loop Power control
27. CS Fallback
Basically LTE is a Packet only technology. It is well designed for data traffic. Then
what about Voice call ? This has normally done via CS call in existing technology
(WCDMA, GSM, C2K etc). There can be a couple of options to achieve voice call
in LTE. One of the option is just to use packet based voice call (e.g, VoIP or IMS).
Another option is to use multiple technology. For example, if UE wants to have
packet communication, the network redirect it to the normal LTE core network
and if UE wants to do voice call the network redirect the call to one of the
existing technology like WCDMA, GSM or C2K. This technology that enables to
redirect connection to other technology (e.g, WCDMA, GSM, C2K) is called 'CS
Fallback'.
28. • It may sound very simple and usefull... but it is not that simple as you
think. First, UE should support multiple technologies and network side
would be even more complicated. One of the simplest representation on
network side would be as follows. As you may guess, there should be
some link point between LTE network and 2G/3G network to make this CS
fallback happen. In this case, the connection point is between MSC and
MME and the interface connecting these two entities are called 'SG'
interface.
• Is this everything make CS Fallback happen ? Definately not. There is some
difference in terms of signaling protocol between LTE and 2G/3G. To make
these two different protocol work together would not be that simple. To
make this happen, LTE network should have a certain level of
understanding (compatibility) with 2G/3G protocol and 2G/3G network
shouldhave a certain level of understanding LTE protocol.
• It is not the scope of this short section to describe the whole details of 'CS
Fallback' protocol side. So just keep it mind that it would be pretty
complicated process and try to google some of articles.
•
29. • Triggers of CSFB (When to perform CSFB)
•
• Followings are the list of situation where UE initiate CSFB. These are not the full list
of those situations, but can be most common situations (triggers) for CSCF.
• i) UE is not capable of VoLTE and is registered (or in communication) with LTE
network. User make voice call (MO Call)
• ii) UE is not capable of VoLTE and is registered (or in communication) with LTE
network. UE recieves a Paging message for voice call (MT Call)
• iii) UE is capable of VoLTE, but ims PDN is not established (UE is not registered in
CSCF). User make voice call (MO Call)
• iv) UE is capable of VoLTE, but ims PDN is not established (UE is not registered in
CSCF). UE recieves a Paging message for voice call (MT Call)
• v) UE is capable of VoLTE, ims PDN is established and UE is registered in CSCF, but
Network notifies 'VoLTE not supported' in NAS message.
• vi) UE is capable of VoLTE, ims PDN is established but UE failed to register in CSCF.
User make voice call (MO Call)
• vii) UE is capable of VoLTE, ims PDN is established but UE failed to register in CSCF.
UE recieves a Paging message for voice call (MT Call)
• viii) UE is capable of VoLTE, ims PDN is established and UE is registered in CSCF but
SIP INVITE for VoLTE failed to go through (e.g, getting some error or reject code
right after SIP INVITE)
