Fraccionamiento. Concepto general

9.1 RTWP Definition

The RTWP of NodeB is the uplink inband received total power, clearly defined in the protocol:

Table 9-1 Received total wide band power(TS 25.215 v600)

Definition The received wide band power, including noise generated in the receiver, within the bandwidth defined by the receiver pulse shaping filter. The reference point for the measurement shall be the Rx antenna connector. In case of receiver diversity the reported value shall be linear average of the power in the diversity branches. When cell portions are defined in the cell, the total received wideband power shall be measured for each cell portion.

According to Table 9-1, the RTWP is the inband signal strength of NodeB, with the reference point at Rx connector; the RTWP involves the noise from NodeB.

Huawei uses the reference point as shown in Figure 9-1. The reference point is point A without TMAs or point B with TMAs.

Figure 9-1 Structure of uplink Rx channel of V1.3 NodeB

z Antenna in: the input port of antenna, from which the signals S and PN are input.

z MON in: the loading input port, where white Gaussian noise is input.

z ANT frame: including TMA NTTA and feeder. The TMA has a gain of 12 dB. The feeder has an attenuation of 4 dB. The noise figure of ANT frame NF1 <= 2.

z NDDL frame: including NDDL fixed gain amplifier with gain of 38 dB. The range of the adjustable attenuation is 0–12 dB, which counteracts TMA gain and feeder attenuation. The white Gaussian noise for loading is input from the monitoring port.

After attenuation of 35 dB is input, it is combined to uplink Rx channel. The NDDL NF2 <= 2.

z NRFB: the backplane and connection line are combined as a frame, with an attenuation of 8 dB.

z NTRX: its uplink gain is 45 dB. Its noise figure is NF3 = 19. AD sampling is performed on signals after passing AGC. Digital intermediate frequency is processed. Gain processing is performed by DAGC. The AGC and DAGC provide a

2006-06-29 Huawei Confidential. No Spreading Without Permission. Page 48 of 51 dynamic range of 35 dB. The AGC takes effect only when signals are strong. Its gain for weak signals is 1.

The NF of ANT frame, NDDL frame, and NTRX frame mentioned previously is obtained by respective test. The NF after cascading three modules is:

NF = NF1 + (NF2-1)/G1 + (NF3-1)/(G1*G2)

The gain of the class 1 and class 2 is large, so the NF primarily depends on class 1 and class 2. Now the NF of NB is about 3.

The following paragraphs describe the unloaded and loaded conditions.

1) Unloaded condition

The power spectrum density of thermal noise is –174 dBm/Hz. It is –108.16 dBm / 3.84 MHz.

The working point of uplink feeder port (RF) is –108.16 dBm / 3.84 MHz.

The working point of intermediate DAGC is –108.16 + 5 + NF = –30.16 dBm / 3.84 MHz. Wherein, "75" is the entire gain of uplink Rx channel.

2) Assume uplink load is present. The uplink interference margin: 3 dB (50% load) uplink feeder port (RF) working point is –105.16 dBm / 3.84 MHz.

The working point of DAGC (intermediate frequency) is –105.16 + 75 + NF = –27.16 dBm /3.84 MHz.

9.2 Uplink RF Channel Adjustment Principles

Assume:

z The thermal noise at feeder port is –108 dBm.

z The RF amplifier NF is 3.

z The rated gain of RF amplifier is G0. This value is an expected and theoretic gain for the amplifier.

z The actual gain of RF amplifier is G1. This value is an actual gain for the amplifier.

The difference between G1 and G0 is d (= G0 - G1).

The gain of digital intermediate is 0, needless of consideration.

When no signals are input to the feeder port and the combination end connects to the matched load, according to the digital intermediate frequency, the calculated power PI is –108 + 3 + G1. After the software obtains PI, it calculates RTWP: RTWP1 = PI - G0.

Because the rated gain of RF channel is G0, the actual gain of RF channel G1 is unknown. Actually the accurate RTWP0 is P1 - G1. The accuracy of power PI calculated by intermediate is high, and the error can be neglected. RTWP1 = PI - Go = PI - (G1 + d)

= PI - G1 + d = RTWP0 + d. Therefore "d" is the error of RTWP. The adjustment aims to locate "d", consequently to obtain RTWP0. The software finally reports adjusted RTWP = RTWP1 – d = RTWP0.

If the opposite end is to match the load, an unadjusted RTWP = –105 dBm, different from expected –106 dBm. This shows that the RF gain increases by 1 dB. Namely, d is 1, so an adjustment of –1 is input. The software reports –105 dBm – 1 = –106 dBm to system before reporting. The formula remains the same whatever signals are input. RTWP1 = PI - Go = PI - (G1 + d) = PI - G1 + d = RTWP0 + d. After adjustment, the system will report correct RTWP value if ambient temperature remains the same.

The adjustment for different versions of NodeB is different. The V12 NodeB and previous versions of NodeB involve the RF channel gain of actual adjustment, which enables RTWP to restore to the rated value. The V13 NodeB has no gain adjustment components of RF channel, and instead it adjusts the RTWP value before the software reporting and the actual RF gain remains the same. The slight change (+/- 4 dB) of RF gain has neglectable impact on system performance. The RF channel gain is high, so the receiver

2006-06-29 Huawei Confidential. No Spreading Without Permission. Page 49 of 51 NF is approximately fixed under this gain variation. The RTWP compensation of V15 NodeB or higher versions of NodeB have it added before data reporting.

9.3 RTWP Error and Accuracy

Table 9-2 lists the requirements. The NodeB will perform better than this.

Table 9-2 Absolute accuracy requirement

Conditions

Parameter Unit Accuracy [dB]

Range

Io dBm ± 4 –103<= Io <= –74 dBm

Relative accuracy requirement

The relative accuracy is defined as the Received total wideband power measured at one frequency compared to the Received total wideband power measured from the same frequency at a different time.

Table 9-3 Relative accuracy requirement

Conditions

Parameter Unit Accuracy [dB]

Range

Io dBm ± [0.5] For changes <= ±5.0dB and

–103 <= Io <= –74dBm Received total wideband power measurement report mapping

The reporting range for Received total wideband power (RTWP) is from -112 ... -50 dBm.

In following table the mapping of measured quantity is defined. The range in the signaling may be larger than the guaranteed accuracy range.

Table 9-4 Received total wideband power measurement report mapping

Reported value Measured quantity value Unit

RTWP_LEV _000 RTWP < -112.0 dBm

When the actual RTWP is smaller than the value –112 prescribed by protocol, the NodeB O&M system will not record its RTWP upon RTWP tracing.

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9.4 RTWP Effect

The protocol defines the requirements on measurement accuracy of RTWP. The relative accuracy is +/- 0.5 dB. The absolute accuracy is +/- 4 dB. The protocol recommends using RTWP as admission control algorithm. Initially the RNC uses RTWP as admission control algorithm, so the NodeB must perform corresponding adjustment to conform the accuracy requirements on admission control. Actually the RTWP is affected by both accuracy of RF channel gain and external interference, which is frequent, especially on the operator S. Therefore Using RTWP as admission control algorithm is irrational. The RNC must use other admission control algorithm, so the RTWP should have less effect.

Actually it is in this way.

The prior admission algorithm for RNC is not RTWP-based, which is a candidate algorithm. RTWP helps to judge whether the NodeB is affected by uplink interference and the location effect upon uplink interference.

The following paragraphs list the standard RTWP value of Huawei serials of NodeB with or without TMAs.

1) If all NodeBs are not equipped with TMAs, the antenna matches NodeBs, the system is adjusted, and no external signals interfere with the system, the RTWP is about –105.5 dBm. If the RTWP is beyond –105.5 dBm +/- 2 dB, the causes might be:

z The system adjustment is problematic, so the set gain of system is different from the actual gain.

z The connection of antenna and feeder is problematic.

z External signals interferes the system.

2) If all NodeBs are equipped with TMAs, the antenna matches NodeBs, the system is adjusted, and no external signals interfere with the system, the RTWP is about –105.5 dBm. If the RTWP is beyond –105.5 dBm +/- 2 dB, the causes might be:

z The system adjustment is problematic, so the set gain of system is different from the actual gain.

z The connection of antenna and feeder is problematic.

z External signals interferes the system.

z The attenuation of RF front end is problematic after adding TMAs.

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List of Reference

[1] 3GPP, 25.215 3GPP 2001/06 protocol

[2] 3GPP, 25.133 3GPP 2001/06 protocol