UMTS
Showing posts with label UMTS. Show all posts
Showing posts with label UMTS. Show all posts

3G Optimization Paging Reception

3:04 PM Add Comment

The purpose of the paging procedure is as follows:


 -The core network (CN) originates the paging procedure to inform selected UEs of service requests and to trigger reading of updated UTRAN system information.
-The UTRAN originates the paging procedure to trigger state transitions from URA_PCH to CELL_FACH or idle mode for selected UEs.

1-Paging Types 

Paging UE in Idle, CELL_PCH, URA_PCH State (Type 1)

+When an UE is in idle, CELL_PCH, or URA_PCH state, UTRAN sends a paging message to the UE through the PCCH.

Paging type 1 procedure is used to transmit paging information to the selected UEs in idle mode, CELL_PCH or URA_PCH state using the PCCH. With this feature, upper layers in the network can:

-Trigger UE establishing an RRC signaling connection.
-Trigger CELL UPDATE procedure of UE in CELL_PCH or URA_PCH state.
-Trigger reading of updated system broadcast of UE in idle mode, CELL_PCH or URA_PCH state.
-Trigger releasing signaling connection of UE in CELL_PCH or URA_PCH state.
+When the CN sends data to UEs in CELL_PCH or URA_PCH state, the UTRAN shall repeat the paging process five times in case of a paging failure towards a UE for some reasons (For example, the UE has moved out of the UTRAN and transferred to an inter-RAT network.). If the UTRAN still fails to page the UE, the UTRAN considers that the paging towards the UE fails and releases the RRC connection with the UE.

Paging UE in CELL_FACH, CELL_DCH State (Type 2)

The network can control the UE in CELL_FACH or CELL_DCH state which has DCCH with paging type 2 procedures. In paging type 2, UTRAN sends a paging message to the UE in CELL_FACH or CELL_DCH state through the DCCH or FACH.

 Reception Technology

+To reduce power consumption, the UE can read the information from the PICH only at a particular time. This is known as the Discontinuous Reception (DRX) technology. The interval between two consecutive receiving occasion is called DRX cycle.

+For Frequency Division Duplex (FDD), the DRX cycle length shall be 2k frames, where k is an integer and is determined by the following three parameters:

-CN domain specific DRX cycle length for CS
-CN domain specific DRX cycle length for PS
-UTRAN DRX cycle length coefficient

The description of the parameters is as follows:

-CN domain specific DRX cycle lengths
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-The UE may be attached to different CN domains with different CN domain specific DRX cycle lengths. The UE shall store these lengths for all CN domains where the UE is attached and shall use the shortest one.
-UTRAN DRX cycle length

+For a UE in idle mode, the DRX cycle length equals the shortest value of the stored DRX cycle length for the CN domains where the UE is attached, with no signaling connection established.

+For a UE in CELL_PCH state or URA_PCH state, the DRX cycle length equals the shortest value of the following lengths:

-UTRAN DRX cycle length
-Any of the stored DRX cycle length for the CN domains where the UE is attached, with no signaling connection established
If you set a great DRX cycle length coefficient, the period for UE detect paging information will be long; therefore, the UE can reduce the power consumption, but the delay for responding to a paging will be long.

why we Use Channel Quality Indicator (CQI) in UMTS not only the ECNO??

12:42 PM Add Comment

CQI report 

UE sends a Channel Quality Indicator (CQI) on the uplink (HS-DPCCH)

CQI

-Estimates the number of bits that can be transmitted to the UE using a certain assumed HS-PDSCH -power with a block error rate of 10%
-UE receiver performance
Good UE receiver can report that it can receive more bits than a Bad UE receiver implementation for the same channel conditions.


PCPICH_RX
Received power of the P-CPICH
Г
Measurement Power Offset MPO
Cell level parameter hsMeasurementPowerOffset
∆
Reference power adjustment
Given by Table 7A, 7B, 7C, 7D, 7E, 7F or 7G depending on the UE category.

Physical layer procedures (FDD)

CQI algorithm indicates 

-Transport block size
-Number of HS-PDSCH codes
-Modulation Type
-HS-PDSCH Power

HSDPA Scheduler algorithm indicates

 -Which UE to transmit to in the TTI, 
-Available HS-PDSCH transmission power, Available number of HS-PDSCH codes. 
-It does not indicate how much data to transmit.
CAT6
CQI Value
Transport Block Size
Number of HS-PDSCH
Modulation
Reference Power Adjustment
1
137
1
QPSK
0
2
173
1
QPSK
0
3
233
1
QPSK
0
4
317
1
QPSK
0
5
377
1
QPSK
0
6
461
1
QPSK
0
7
650
2
QPSK
0
8
792
2
QPSK
0
9
931
2
QPSK
0
10
1262
3
QPSK
0
11
1483
3
QPSK
0
12
1742
3
QPSK
0
13
2279
4
QPSK
0
14
2583
4
QPSK
0
15
3319
5
QPSK
0
16
3565
5
16-QAM
0
17
4189
5
16-QAM
0
18
4664
5
16-QAM
0
19
5287
5
16-QAM
0
20
5887
5
16-QAM
0
21
6554
5
16-QAM
0
22
7168
5
16-QAM
0
23
7168
5
16-QAM
-1
24
7168
5
16-QAM
-2
25
7168
5
16-QAM
-3
26
7168
5
16-QAM
-4
27
7168
5
16-QAM
-5
28
7168
5
16-QAM
-6
29
7168
5
16-QAM
-7
30
7168
5
16-QAM
-8


Why CQI?

Back to  Basics:

PN codes (distinguish each Base Station)

-Not orthogonal
-High cross correlation properties
-PN1 * PN2  ≠ 0 (mini. output)  


Channelization Codes (distinguish data channels Coming from each Base Station)

-Orthogonal Codes
-OC1 * OC2 = 0



-Ec/No for most of us is quality measurement metric. 
-It gives us how good or bad the link quality is.
-However by definition it is confusing
RSCP
-Received signal code power
-Received power level of pilot channel of a one cell (dBm/mW)
-Using RSCP we can compare different cells
-Using RSCP handover and cell reselection decisions can be taken
RSSI
-Signal power over the complete 5MHZ carrier which include all components received 
-Signal from the current cell and neighboring cells on the same frequency
-Theoretically in an isolated cell having only CPICH power with no other channels  
RSSI ≈ CPICH power 
-RSSI will change if the carrier use the DCH or the common channels

CPICH  Ec/No
-Pilot channel quality ,energy per chip over total received power spectral density
Ec/No= RSCP/RSSI
-The Better this value the better the signal can be distinguished from the over all nosie
-Always negative 
-Using Ec/No we can compare different cells
-Using Ec/No handover and cell reselection decisions can be taken

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Noise power spectral density 
-Interfering power  
-Non interfering power 
-Thermal noise
-Test bed being served by single cell
Ec/No of UE is 
Measure of PCPICH =RSCP
Measure of total wide band power =RSSI

Assume that UE is in Test bed being served by single cell`
-Cell MAXTXPOWER  20 watt (43 dBm)
-Assuming that 10 % of the cell power is dedicated for CPICH 2 watt (33 dBm)
-If you have no DCH or HS channels 
-Ec/No= 10 log (CPICH Power/Total transmitted power)
-Ec/No=10 log (2w/2w)= 10 log 1 = 0

Assume that you start HS session
-Ec/No= 10 log (CPICH Power/Total transmitted power)
-Ec/No=10 log (2w/20w)= -10 dB (Poor value)
-Ec/No will always give a false value for an HSDPA user


CQI Adjustment


Deviating CQI reports lead to faulty decisions

-CQI accuracy will continue to vary depend on :
-UE model 
-UE vendor

Deviating CQI

-UE that consistently overestimates the channel quality
+Scheduled too often, at the price of other users. 
+Experience a block error rate that is higher than the target 10%, with more retransmissions and reduced system throughput and increased service delay
-UE instead underestimates the channel quality
 +Scheduled too seldom. 
+Experience a Block error rate will be lower than 10%, which will lead to lower transmitted data rates than possible and hence reduced system throughput.

In both cases, both system throughput and end-user experience of the service is negatively impacted.

To avoid the negative system impact due to inaccurate CQI reports, 
-CQI adjustment algorithm 
+RBS works on the ACKs and NACKs received from the UE to determine if the UE is overestimating or underestimating the channel quality. 
+The algorithm make every effort to achieve a block error rate of 10%

-The output from the adjustment algorithm is CQIadjusted, 
-The CQI adjustment algorithm is an optional feature and can be enabled on cell level through parameter cqiAdjustmentOn

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3G Network Planning- Detailed UMTS planning capacity input analysis (Part 6)

2:37 AM Add Comment

Before you read this part in 3G Network  Planning you should read the below Parts in first

capacity input analysis

it is one of the most important step in any dimensioning process is defining the input data and it  is the second step after coverage dimensioning .

1-calculate traffic model 

traffic model is a means of researching the capacity features of each service type and the QOS expected by the users who are using the service from perspective of data transmission.

1.1:Grade of service 

The Grade of Service can be measured using different sections of a network. When a call is routed from one end to another, it will pass through several exchanges. If the Grade of Service is calculated based on the number of calls rejected by the final circuit group, then the Grade of Service is determined by the final circuit group blocking criteria. If the Grade of Service is calculated based on the number of rejected calls between exchanges, then the Grade of Service is determined by the exchange-to-exchange blocking criteria. 
The Grade of Service should be calculated using both the access networks and the core networks as it is these networks that allow a user to complete an end-to-end connection.
 Furthermore, the Grade of Service should be calculated from the average of the busy hour traffic intensities of the 30 busiest traffic days of the year. This will cater for most scenarios as the traffic intensity will seldom exceed the reference level.
The grade of service is a measure of the ability of a user to access a trunk system during the busiest hour. 
The busy is based upon customer demand at the busiest hour during a week month or year.
Grade of service=(number of lost calls)/(number of requsted calls)

1.2 user profile

It is about avg call duration and number of requsted calls per day and srvice rate which will use.
It is different according to economical distribution for this city.

1.2.1 services rates 

Service rate Kbps
12.2
64
128
384
Circuit switching
√
√
No
no
Packet switching
No
√
√
√
For  each service rate must identify number of users and user profile as traffic
 Per user in Kb per hour or average  number of calls and average call duration in minute.
Note : 12.2 Kbps circuit switching is voice calls so it have the most number of users .
Erlang=(bit transmitted)/(total capacity)
example: if we have 80 Kb per hour so 
erlang = 80*1000*8/64000*60*60.

1.3 Speed of the user

Speed of the user is very important parameter which affect the signal to noise ratio for each service (Eb/N0)
Speed
Eb\No (circuit switching 12.2kbps)
Eb\No(circuit switching 64kbps)
Eb\No(packet switching 64kbps)
0
5.1
1.7
1.5
3
11.9
9.2
6.2
50
9.4
6.4
6.3
120
7.2
3.8
3.4







Speed
Eb\N0
(circuit switching 12.2kbps)
Eb\N0
(circuit switching 64kbps)
Eb\N0
(packet switching 64kbps)
Eb\N0
(packet switching 128kbps)
Eb\N0
(packet switching 384kbps)
0
5.1
5
4.7
7.9
11.4
3
13.4
7.78
3.9
7.2
10.8
50
10.8
15
11.4
9.7
11.3
120
7.8
10.4
9.7
8.8
12









1.4 area type

It is a parameter which effect on  gama  and ioc_ior values 
Area type
Gama
Ioc_Ior
Dense urban
0.7
2.9
Sub urban
0.5
2.9
Urban
0.6
2.9
Rular
0.4
1.99
Dopen
0.3
1.9







1.5. Loading Factor (ETA)

The loading factor ETA  take values between 0% to 100% .
for example if ETA = 50 % it mean  that there are 150 % increase  of interference  above  the introduced one by home user alone.
The inverse of  the factor (1 +ETA) is sometimes known as the frequency reuse factor .
the frequency reuse factor  is ideally equal to one in the single  in the single cell case .In the multicell case as loading (ETA) increase the frequency reuse factor decrease.

2-Mpole & Npole

M pole is the uplink Pole capacity . which give a theoretical limit for the number of UEs that a cell can support . It is service (RAB) dependent . At this limit the interference level in the system is infinite and thus the coverage reduced to zero 
N pole is similar to Mpole but in  the downlink  as it give a theoretical limit for the number of UEs that a cell can support .
We calculate Mpole and Npole for each service rate separately to calculate needed number of sites  for each service rate.

3-spreading factor

The spreading factor is the concept of CDMA used in UMTS.As after spreading the user data the a single bit is called the chip.The spreading factor is the ratio of chip rate to bit rate
spreading factor=(chip rate)/(bit rate)

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4-activity factor

It is a definition for the time using to send data over a total holding time which I have a channel to send .This parameter has an impact on the air interface dimensioning as well as  the hardware dimensioning . Low activity factor  allows more users to share the same spectrum this however require more allocation  of hardware resources. 
Activity factor for packet switching = 1 as I send data all holding time but,
Activity factor for circuit switching=0.6 as there is time no data sent.
activity factor=(time used to send data)/(holding time)

5-alpha (interference factor)

It is the interference factor  for uplink  calculations .

6-Ior/Ioc

 is the ratio of Cell Power to AWGN it is depend on the area type

7-Gama

It is the interference factor  for downlink calculations 

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