RSRP :- Reference signal receive power <<>>
RSRQ :Reference signal receive quality <<>>
SINR :-Signal to Noise Ratio <<>>
RSSI :- Received Signal Strength Indicator <<>>
CQI :- Channel Quality Indicator <<>>
PCI :- Physical Cell Id <<>>
BLER :- Block Error Rate <<>>
Downlink Throughput <<>>
Uplink Throughput
|
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
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.
* 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)
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 :– RSRP 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
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 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.
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.
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%
Downlink Throughput
- n 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.
Uplink
Throughput
-I n 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.
Phone-Based Drive
Test for LTE
Phone-based drive
test systems are useful for evaluating basic network performance and are
essential to characterizing the end-user experience while using the network.
Phone-based systems address the need to verify network settings such as cell
selection and re-selection boundaries and to measure the voice and data
application performance in the live network. Most modern mobile phones chipsets
have engineering measurement capabilities built into them, which were used
during the mobile phone’s design process.
These same
parameters are exploited in drive test software to provide new value to the RF
engineers rolling out the final network.
With radio
resource management taking place in the eNB, suitably instrumented phones can
be used to monitor the performance of the physical layer including modulation
schemes, access procedures, synchronization, and power control.
The same types of
parameters are measured for LTE as for other cellular technologies. Beyond the
essential protocol log, which provides visibility of the fundamental
interaction with the network, the initial focus is on RF coverage and quality.
Figure 3 identifies the main measurements that are made. In LTE, these equate
to reference signal received power (RSRP) and reference signal received quality
(RSRQ), which are measures of the strength and quality of reference signals.
These two results are the major components of network-based decisions to keep a
UE on its current cell or hand it over to an adjacent cell.
Additional
measurements used to assess the link quality include call quality index (CQI)
and block error rates (BLER). While RSRQ is the 3rd Generation Partnership
Project (3GPP)-defined measure of signal-to-noise ratio (S/N), which all
mobiles must make and report, many LTE UEs are also making custom
carrier-to-noise ratio (C/N) measurements, which they use internally to assess
channel quality. These additional carrier-to-interference (C/I) measurements
are not reported back to the network, but they are available within the drive
test logs and can be used by RF engineering teams to get extra insight as to
how
the mobiles perceive
the RF environment.
Instrumented
phones can also report the measured channel state information (CQI, pre-matrix
indicator [PMI], and rank indicator [RI]) and hybrid automatic repeat request
(HARQ) statistics. The number of resource blocks assigned to a device at a
particular time, together with the modulation and coding scheme applied, can be
used to evaluate the eNB scheduler performance. These types of tests are of
particular interest during early stages of deployment of a new network but also
must be monitored as network loading increases and true end-user traffic
patterns establish
One of the most
interesting LTE network features to RF optimization engineers is the impact
that multiple input multiple output (MIMO) with spatial multiplexing and antenna
diversity brings to the end-user performance. Drive-test-enabled devices can
log the current rank, number of transmit and receive paths in active use,
together with the reported availability of antennas. They can also individually
report the signal strength and quality from each of the device’s antennas. This
information can be correlated with
the measured data
application performance to establish the impact MIMO has on network
performance.
Because full MIMO
is a feedback system, an instrumented mobile that is part of the active channel
is the only way to evaluate the true impact that this technology can make.
As LTE networks
are deployed alongside existing cellular networks, cellular operators are
particularly interested in the efficient use of each network resource and the
transition between the network technologies. Drive testing is used extensively
to monitor the handover points between LTE and legacy technologies. The signal
strength, quality, cell ID, and neighbor information both before and after a
handover are analyzed and optimized. The length of time it takes to complete an
initiated handover, success rates, and the end-user data-interruption time
(during the actual transition between technologies) are key performance
indicators that are closely monitored.
End-user data
throughput performance and latency are the two key measures of a network’s
optimization. If the network is not achieving the expected data performance, it
is important to be able to analyze the signaling performance and settings at
each signaling layer, including the radio resource control (RRC), radio link
control (RLC), and media access control (MAC). Monitoring the resources
allocated to a UE together with the measured network conditions, available
neighbor cells. and power levels will allow troubleshooting and optimization of
network settings
