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Received power and

power density

Power

[dBm]

Power

Density

[dBm/Hz

]

Comment

(Power Density=Power/B

with B=3.84MHz)

Received (useful) signalC

(or RSCP)Ec

Ec = Energy per chip=C/B

Thermal Noise -108.1 Nth=-174Nth = k.T0 with k=1.38E-20mW/Hz/K

(Bolztmann constant) and T0=293K (20C)

Thermal Noise at receiver N -N =-108.1dBm+NFreceiver [dB] (=Thermal

noise + Noise generated at receiver)

Interference intra-cellIintra

(Iown)-

interference received from transmitters

located in the same cell as the receiver

Note: C is included in Iintra

Interference extra-cellIextra

(Iother;Iinter)-

interference received from transmitters not

located in the same cell as the receiver

Interference I -I=Iintra+ Iextra

(no Thermal noise at receiver included)

1.2 UMTS RNP notations and principles

Notations (1)

22All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

Received power and

power density

Power

[dBm]

Power

Density

[dBm/Hz]

Comment

Power Density=Power/B with

B=3.84MHz

Total received power

(Total noise)

I+N

(RSSI)Io

I+N= Iintra+ Iextra +N

Note: C is included in (I+N)

Total received power

(Total noise without useful signal)

I+N-CNo

(Nt)

No=( Iintra+ Iextra +N-C)/B

Note: C is not included in No

1.2 UMTS RNP notations and principles

Notations (2)

Note: Io can be measured with a good precision, whereas No is not easy to

measure (but it is useful for theoretical demonstrations)

23All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

Ratio in [dB] Comment

Received

energy per chip

over noise

Ec/Io

Here noise=IoThis ratio can be accurately measured: it is used for physical

channels without real information bits, especially for CPICH (Pilot

channel)

Ec/No

(C/I)*

Here noise=NoThis ratio is difficult to measure, but is useful for theoretical

demonstrations: it is used for physical channels with real

information bits, especially for P-CCPCH and UL/DL dedicated

channels.

Received

energy per bit

over noiseEb/No

Eb/No=Ec/No+PG with PG (Processing Gain) = 10 log [(3.84

Mchips/s) / (service bit rate)]

e.g. for speech 12.2 kbits/s, Processing Gain = 25dB

Required

energy per bit

over noise(Eb/No)req

Fixed value which depends on service bit rate...(see 3.5)

Eb/No shall be equal or greater than the (Eb/No)req

1.2 UMTS RNP notations and principles

Notations (3)

*This ratio is often written with the classical GSM notation C/I (Carrier over Interference ratio): this notation is incorrect, it should be C/(I+N-C)

24All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

Two more

interesting

ratios!

in [dB] Comment

f

(or little i)Iextra / Iintra

In a homogenous network (same traffic and user

distribution in each cell), f is a constant in uplink.

Typical value for macro-cells with omni-directional

antennas: 0.55 (in uplink)

Noise Rise (I+N)/N

Very useful UMTS ratio to characterize the moving

interference level I compare to the fixed Thermal Noise at receiver level N.

1.2 UMTS RNP notations and principles

Notations (4)

25All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

1.2 UMTS RNP notations and principles

Exercise (1/2)

Assumptions:

- n active users in the serving cell with speech service at 12.2kbits/s and

(Eb/No)req =6 dB

- Received power at NodeB: C=-120dBm (for each user)

- homogenous network (f=0.55)

- NFNodeB = 4dB and NFUE =8dB

Node

B

Serving cell

Surrounding cells

26All rights reserved Alcatel - 3FL 11194 ABAA WBZZA Ed.01P04

1.2 UMTS RNP notations and principles

Exercise (2/2)

1. What is the processing gain for speech 12.2kbits/s ?

2. The users in the serving cell are located at different distance from the NodeB: is it

desirable and possible to have the same received power C for each user?

3. What is the value of the Thermal Noise at receiver N?

4. Complete the following table:

n

[users]

I

[dBm]

I +N

[dBm]

Noise

Rise [dB]

Ec/No

[dB]

Eb/No

[dB]Comment

1

10

25

100