Active Cell Operating Mode
Last updated: January 15, 2009
Active Cell Overview
The
Active Cell Operating Mode
allows you to make a signalling connection between the test set (emulating a base station (BS) in a network) and a UE (mobile station). The types of connections available are described in
Current Service Type
. When connected (and during the connection process for some measurements), the UE's performance can be measured using the suite of measurements shown when the
Measurement selection
key or
Instrument selection
key is pressed.
The following example selects
Active Cell Operating Mode
via GPIB:
OUTPUT 714;"CALL:OPERating:MODE CALL"
Active Cell Operating Considerations
Many of the settings
used
in active cell mode cannot be
changed
during active cell mode operation. A message is displayed to alert you to this situation if you try to change them. These are settings that must be set before attempting to get the UE connected on a call, or settings that are not normally changed during base station operation in a network. Use the
Cell Off
operating mode to change these settings. See
CALL:OPERating
to select operating modes.
HSDPA in Active Cell Operating Mode
This section is only applicable to the lab application or feature-licensed test application.
HSDPA Activation in Active Cell
In active cell operating mode, HSDPA is active when HS-SCCHs are being generated by the test set (even if
HSDPA Cell 1 Connected HS-SCCH 1 Level
is turned off). HS-SCCHs are created when an RB Setup message is sent to the UE as part of a service setup that includes an HSDPA channel configuration.
In active cell operating mode, you can establish two types of HSDPA connections:
HSDPA Operation in Active Cell
When on an HSDPA RB Test Mode connection, in addition to the 12.2k RMC and common channels, the test set transmits HS-PDSCHs (the number is determined by the
FRC Type
or
User Defined Number of Active HS-PDSCHs
settings). When on an HSDPA Packet Data connection (
lab application only
), in addition to the common channels, the test set transmits HS-PDSCHs (the number is determined by the
PS Data Configuration Type
setting and the
Current UE HS-DSCH Category
).
The test set can transmit up to 4 HS-SCCHs (you directly specify how many HS-SCCHs you want the test set to transmit using the
HSDPA Connected DL Channel Levels
). However, HS-SCCH 1 is the only HS-SCCH ever directed to the UE (see
H-RNTI Parameters
).
When HSDPA is active, the test set also generates a six-channel OCNS as specified by 3GPP TS 34.121 sE.5.2 (codes 122 - 127, spreading factor 128), rather than the OCNS defined in sE.3.6 (see
OCNS in HSDPA/HSPA
).
You can configure the downlink code channel levels and channelization codes that are used when HSDPA is active using the
HSDPA/HSPA DL Channel Codes
and
HSDPA Connected DL Channel Levels
.
You can configure many aspects of the HSDPA functionality using the
HSDPA Parameters
:
The
HSDPA Information
screen displays UE HS-DSCH category information as well as counters to help you monitor the HSDPA connection status.
You can vary the timing between the uplink DPCH and uplink HS-DPCCH using the
Default DPCH Offset (DOFF)
parameter.
HSPA in Active Cell Operating Mode
This section is only applicable to the lab application or feature-licensed test application.
When on an HSPA RB Test Mode connection or HSPA PS Data connection, in addition to the 12.2k RMC and common channels the test set transmits HSDPA channels (HS-PDSCHs and HS-SCCHs) and HSUPA channels (E-HICH, E-AGCH, and E-RGCH). The test set also generates the same six-channel OCNS used for HSDPA connections (3GPP TS 34.121 sE.5.2).
You can configure the downlink code channel levels and channelization codes that are used when HSPA is active using the
HSDPA/HSPA DL Channel Codes
and
HSPA Connected DL Channel Levels
.
You can configure many aspects of the HSPA functionality using the
HSUPA Parameters
:
The
HSUPA Information and HSUPA Happy Bit Information
screen displays UE reported E-DCH category, counters to help you monitor the HSUPA connection status, as well as other HSUPA status indicators.
The test set supports all UE E-DCH categories; however at this time, the test set only support an HSUPA TTI of 10 ms.
The following call processing procedures are supported while on an HSPA RB Test Mode or HSPA PS Data connection.
HSPA Downlink Channel Details
E-AGCH:
While on an HSPA connection the test set transmits an E-AGCH. A real network only transmits on the E-AGCH when it wants to send a new absolute grant to a UE; if it has nothing to send, there is no power in the E-AGCH. To keep OCNS power constant in the test set (as required by many test specifications), the test set continuously transmits the E-AGCH. When it wants to send an absolute grant to the UE, it transmits the E-AGCH using the
Primary E-RNTI (Hex)
. When the test set is not transmitting an absolute grant to the UE, it transmits the E-AGCH using the
Alternate E-RNTI (Hex)
. When transmitting using the
Alternate E-RNTI
, the test set always sends an Absolute Grant Value of 15 and an Absolute Grant Scope of "All HARQ Processes".
E-HICH/E-RGCH:
In a real network, DTX is used on the E-HICH and E-RGCH channels in some circumstances. However to keep OCNS power constant in the test set, DTX is not used. In the following circumstances the network would DTX the entire E-HICH or E-RGCH frame:
-
On the E-HICH when the UE did not transmit during the corresponding uplink frame.
-
On the E-HICH when a cell in the non-serving RLS is trying to communicate a nack.
-
On the E-RGCH when the network wants to communicate a "Hold" command to the UE.
Information is signaled to the UE on the E-RGCH and E-HICH channels using a 40 bit orthogonal signature that can be completely transmitted in a single timeslot. There are 40 different signatures available to the network (see 3GPP TS 25.211 s5.3.2.4 Table 16A) and the two channels use a different signature in any given slot. This way both the E-RGCH and E-HICH can share the same channelization code. Rather than use a single static signature for a channel, the network hops between 3 different signatures. The UE knows which signature to expect for each channel in any given slot from a signature index it is assigned at call setup and its knowledge of the signature hopping pattern defined in 3GPP TS 25.211 s5.3.2.4 Table 16B. The UE is given a different signature index for the E-HICH and E-RGCH to ensure the two channels remain orthogonal. 3GPP TS 25.212 s4.11 & 4.12 define the mapping from logical value (for example ack or nack), to a specific numeric value that is then multiplied with the signature. For instance, on the E-HICH transmitted from a serving cell, an ack is signalled by a 1 and a nack by a -1. These values are then multiplied with the 40 bit orthogonal signature, which means an ack is signaled by the presence of the expected signature and a nack by the presence of the inverse of the expected signature. From the perspective of the UE listening to these channels, DTX is detected by the absence of the 40 bit orthogonal signature that it was expecting (inverted or non-inverted). However, because the signatures are all orthogonal to each other it is possible for the network to transmit a signature that the UE is not expecting and the UE will still detect DTX. This explains why the E-HICH/E-RGCH can utilize the same code channel. As long as the two channels are assigned different signature indices in the UE they remain orthogonal to each other despite occupying the same space in the OVSF code tree. A network also utilizes the orthogonal property of the signatures to multiplex multiple UEs onto the same E-HICH/E-RGCH code, again by assigning different UEs unique signature indices. Therefore in all the whole-frame DTX situations outlined above, the test set communicates DTX by transmitting a signature that the UE is not expecting (Alternate E-HICH Signature Sequence of 2), Alternate E-RGCH Signature Sequence of 3). This keeps the power in the E-HICH and E-RGCH constant, and thus OCNS remains constant, while still giving the test set the ability to signal DTX to the UE. The other situation where a real network will use DTX is in slots 13-15 of the E-HICH and E-RGCH. Both the E-HICH and E-RGCH (if the E-RGCH is being generated from a serving cell), are defined to transmit only during the first 12 slots of the 15-slot frame when 10ms TTIs are used. However, to keep the power in the E-HICH and E-RGCH constant, the test set transmits during slots 13-15 using the signatures defined in 3GPP TS 25.211 s5.3.2.4 Table 16B "E-HICH and E-RGCH signature hopping pattern". The same signature hopping index that is used for slots 1-12 is used for slots 13-15.
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