H.2 E-OTD LMU Requirements

05.053GPPRadio transmission and receptionTS

An E-OTD Location Measurement Unit (LMU) is a unit that makes accurate observed time difference measurements of signals from BTSs. Specifically, the LMU shall be capable of measuring the Time-of-Arrival of bursts transmitted from a BTS on a periodic and predictable basis. The measurement results are used by the system for determining location of a MS. This clause defines the requirements to be put on the receiver of an LMU deployed in the GSM System. Requirements are defined for the E-OTD measurement accuracy of the LMU.

H.2.1 LMU Characteristics

In this clause, the requirements are given in terms of power levels at the antenna connector of the E-OTD LMU. Equipment with an integral antenna may be taken into account in a similar manner as described in Chapter 5 of 3GPP TS 05.05.

H.2.1.1 Blocking characteristics

This subclause defines E-OTD LMU receiver blocking requirements. The reference sensitivity performance as specified in table H.2.2 shall be met when the following signals are simultaneously input to the LMU.

  • A neighbour BCCH carrier as described in H.2.2.1 at frequeny fo, 11 dB above the reference sensitivity level as specified in Table H.2.1.
  • A continuous static sine wave signal as described in Section 5.1 of 3GPP TS 05.05. For GSM 400 and GSM 900, the requirements for “other MS” shall be used. For GSM 850, DCS 1800 and PCS 1900, the requirements for “MS” shall be used.

The exceptions listed in Section 5.1 of 3GPP TS 05.05 apply also for the E-OTD LMU requirements.

H.2.1.2 AM suppression characteristics

This subclause defines AM suppression requirements. The reference sensitivity performance as specified in Table H.2.2 shall be met when the following signals are simultaneously input to the LMU.

  • A neighbour BCCH carrier as described in subclause H.2.2.1 at frequency fo, 11 dB above the reference sensitivity level as specified in table H.2.1.
  • A single frequency signal as described in subclause 5.2 of 3GPP TS 05.05. The requirements for “MS” shall be used.

H.2.1.3 Intermodulation characteristics

This subclause defines intermodulation requirements. The reference sensitivity performance as specified in Table H.2.2 shall be met when the following signals are simultaneously input to the LMU.

  • A neighbour BCCH carrier as described in subclause H.2.2.1 at frequency f0, 11 dB above the reference sensitivity level as specified in table H.2.1.
  • A continuous static sine wave signal and any 148-bit subsequence of the 511-bits pseudo-random sequence in CCITT Recommendation O.153, as described in subclause 5.3 of 3GPP TS 05.05.

H.2.2 Sensitivity and Interference Performance

This clause specifies the required E-OTD measurement accuracy of the LMU with and without interference. The requirements are given in terms of E-OTD measurement error (in microseconds), as function of the carrier and interference input power levels, at the antenna connector of the receiver. Equipment with an integral antenna may be taken into account in a similar manner as described in clause 5 of 3GPP TS 05.05.

The power level, under multipath fading condition, is the mean power of the sum of the individual paths.

H.2.2.1 Sensitivity Performance

With the following configuration and propagation conditions, the LMU shall meet the requirements of 90% RMS E-OTD error defined in table H.2.2.

  • The E-OTD LMU receives a reference BCCH carrier with a power level of 28 dB above the reference sensitivity level defined in table H.2.1.
  • The E-OTD measurements (relative to the reference BCCH carrier) are done on a neighbour BCCH carrier at power levels relative to the reference sensitivity level defined in Table H.2.1. The measurement power levels are given in Table H.2.2.
  • The network requests an E-OTD measurement by commanding the LMU to report the E-OTD measurement with shortest possible reporting period (see 3GPP TS 04.71 Annex A).
  • The measurement performance shall also be achieved with the reference BCCH and the neighbour BCCH carriers having 8-PSK modulated bursts. 8-PSK modulation and the 8-PSK normal bursts are defined in 3GPP TS 05.04 clause 3 and 3GPP TS 05.02 subclause 5.2.3, respectively.
  • The measurement accuracy of the LMU is defined as the root-mean-square (RMS) value of 90% of the measurements that result in the least E-OTD error. As an example, if {x1..xN}is a set of the absolute square E-OTD measurement errors for N trials, sorted in ascending order, the RMS of 90% is defined as:

RMS90 = sqrt( sum(x1..xM)/M )

where M is the largest integer such that M < 0,9 N. For the test, N > 250 trials is recommended . The channels shall be static, i.e. at a constant signal level throughout the measurements.

Table H.2.1: Reference Sensitivity Level

Signal strength at antenna connector

GSM 400, GSM850, GSM 900, DCS 1800, PCS 1900

-110 dBm

Table H.2.2: Sensitivity performance
(RMS90 of E-OTD error in microseconds)

Minimum neighbour carrier signal strength relatively to E-OTD LMU reference sensitivity level (Table H.2.1)

Static channel

0 dB

0.3 s

20 dB

0.1 s

H.2.2.2 Interference Performance

This clause defines E-OTD measurement accuracy (in microseconds) for specified carrier-to-interference ratios of the neighbor BCCH carrier. The reference BCCH carrier is as defined in subclause H.2.2.1. The neighbour BCCH carrier shall be as defined in H.2.2.1 and shall be set to a level 28 dB above the reference sensitivity level defined in table H.2.1. The C/I requirements shall be met for an interference signal which is co-channel, adjacent channel (200 kHz offset), and alternate channel (400 kHz offset) to the desired neighbour BCCH carrier as shown in table H.2.3.

  • The interference signal consists of a random, continuous GMSK modulated signal.

Table H.2.3: Interference performance
(RMS90 of E-OTD error in microseconds)

Interference type

Static channel

Minimum carrier to Interference Level (dB)

Co-channel

0.3 s

0 dB

0.1 s

10 dB

Adjacent channel
(200 kHz)

0.5 s

-18 dB

0.2 s

-8 dB

Adjacent channel
(400 kHz)

0.1 s

-41dB

H.2.2.3 Multipath Performance

This clause defines E-OTD measurement accuracy under multipath conditions. The test setup is as under subclause H.2.2.1 (sensitivity performance) with the following changes:

  • Each burst of the neighbour BCCH carrier propagates through the TU multipath channel specified in annex C of 3GPP TS 05.05. The reference carrier remains static.

The performance requirements are specified in table H.2.4.

Table H.2.4: Multipath performance
(RMS90 of E-OTD error in microseconds)

Minimum neighbour carrier signal strength relative to reference sensitivity (Table H.2.1)

TU3
(12 tap setting)

0 dB

1,5 s

Annex I (normative):
E-OTD Mobile Station Requirements