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RSCP (Received Signal Code Power)

The Received Signal Code Power (RSCP) is the collected RF energy after the correlation / descrambling

process, usually given in dBm. Because this process already filters out the signal with the correct code (the

code meant for the specific UE), the RSCP can not be calculated back to the total received RF power that a

normal monitoring receiver or spectrum analyzer measures. Instead, a correlation receiver has to be used and the

RSCP has to be measured for the specific code only, in the code domain. Only this code power is of interest for

the following receiver stages when judging on the quality of the reception.

A commercial UMTS receiver has to know the code that is transmitted for it in order to perform the correlation

process. With monitoring equipment, however, we want to measure UMTS emissions with any code. Therefore,

special measurement receivers and equipment are necessary for UMTS measurements. These receivers have to

try and correlate the received pseudo-noise-like signal with every possible code. This process is called PN

scanning. Only after the receiver has found a match, the descrambling can take place, followed by measurement

of the RSCP in the code domain.

Ec/I0

This is the ratio of the received energy per chip (= code bit) and the interference level, usually given in dB. In

case no true interference is present, the interference level is equal to the noise level. However, in a UMTS

network the UE normally receives signals from multiple base stations, all transmitting on the same frequency.

Therefore it is possible that even at a location close to a base station, with a high RSCP, no logon is possible, due

to high interference levels from a second nearby base station. This effect is called pilot pollution and network

planners try to avoid too close spacing of base stations to minimize regions where it can occur.

RSSI

In UMTS that's the signal power over the complete 5 MHz carrier which includes allcomponents received, including the signals from the current and neighboring cells on the

same frequency.

The total received signal power (Received Signal Strength IndicatorRSSI) is never

considered in a WCDMA system as an indication of coverage. It is mainly due to theinability to estimate the quality by this value: 10 weak cells would result in a strong

RSSI, but the lack of any dominant server would yield poor system performance. This

concept is sometime called pilot pollution, where multiple servers contribute to a highRSSI, but where the signal cannot be used due to lack of strong dominant server.

What is Cell Breathing in UMTS and its limitations?

In WCDMA, the coverage and capacity requirement cannot be considered independently,but should be planned at the same time with proper guidelines. This relation between

coverage and capacity is often referred to as the breathing effect of WCDMA.

Comparing with TDMA/FDMA technologies, such as GSM, the coverage of a WCDMAnetwork cannot be planned independently of the load on the network. The load on the

network will impact the coverage in mainly two different ways, depending on which

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link (Uplink or Downlink) is considered. On the uplink, as more users are added to the

network, higher noise would be detected at the node Bs. This increase in noise, called riseover thermal, requires each of the phones or data cards (UE) to increase its transmit

power to overcome this noise increase: effectively the uplink coverage is reduced by this

required increase in transmit power.

On the downlink, the breathing effect cannot be quantified so easily as coverage is

impacted by the maximum transmit power assigned to traffic channels and the current

load on the network rather than by a quantifiable formula.

When the loading of the system increases the Ec/No degrades but the RSCP stays

constant. Degrading Ec/No is an indication of increased other cell interference which will

also increase the need for downlink traffic power (DPCH Ec/Ior, when expressed inrelative terms). Power being a limited resource, the higher required transmit power may

not be available, thus the coverage not being met in loaded condition: this represent the

coverage and capacity trade-off for the downlink in a WCDMA systems.

From Ericsson paper the threshold of RSCP and Ec/No are:

HSDPA does not make use of soft-handover; it is of the utmost importance that a single

dominant server be available in the majority of the network. So, according to Qualcommfollowing is the KPI which we should focus on:

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