11 Discontinuous UL DPCCH transmission and discontinous reception of F-DPCH and HSPA DL channels in FDD

25.3083GPPHigh Speed Downlink Packet Access (HSDPA)Overall descriptionRelease 17Stage 2TS

In FDD the discontinous transmission and reception is a configuration of CELL_DCH state, when F-DPCH is configured without DCH configured in Downlink or Uplink, where the resources are allocated but discontinuous uplink DPCCH transmission (Uplink DTX) and discontinuous downlink reception (Downlink DRX) are possible during data inactivity. One of the options of the Uplink DTX also allows the Node B to DRX (Uplink DRX), by restricting the starting points of new data transmission after inactivity by the UE. The Node B has a fast mechanism to revert to the continuous DL transmission, and the UE can revert to the continuous UL transmission autonomously and instantaneously based on standardised rules if more data arrives to the transmission buffer.

The discontinuous transmission and reception schemes are always enabled, upon configuration, only after a certain configurable time. This allows synchronisation and power control stabilisation.

From the continuous transmission, the UE and Node B can autonomously and instantaneously revert to discontinuous UL and DL transmission based on standardised rules.

The discontinuous transmission and reception also allows a configuration of a new UL DPCCH slot format with an increased number of TPC bits as defined in [6].

The configuration of Uplink DTX, Downlink DRX is always in the control of the SRNC. In order to allow SHO with Node Bs under the control of another RNC, the SRNC must be aware of the capabilities of all the Node Bs that provide RLs in the UE active set.

11.1 Discontinuous uplink transmission

The discontinuous uplink transmission is a mechanism that defines how the UE will discontinuously transmit the uplink DPCCH, when configured by the RNC. The uplink DPCCH burst pattern and the uplink DPCCH preamble and postamble together define the discontinuous uplink DPCCH operation. The discontinuous uplink transmission is dependent on the E-DCH and HS-DPCCH activity as described in [3] and below. The uplink DTX is mechanism that can be configured without configuring also the uplink DRX (subclause 11.1.1), or Downlink DRX (subclause 11.2). Additionally, the uplink DTX can operate with or without configuring the HS-SCCH-less HS-DSCH transmission mechanisms (clause 12).

There are two patterns that can be defined for discontinuous uplink DPCCH operation, UE_DTX_cycle_1 and UE_DTX_cycle_2. The latter is used whenever there is no uplink data transmission activity, whilst the former is applied depending on the duration of E-DCH inactivity. This allows uplink DPCCH transmission rate to autonomously (based on standardised rules) adapt to the data transmission activity, and data transmission dependent gains: for higher data transmission activity uplink DPCCH can be configured to be transmitted more frequently and operation is more similar to Rel-6, and for lower data transmission activity DPCCH can be configured to be transmitted less often to achieve higher DTX gain.

The DPCCH burst patterns can be offset using UE_DTX_DRX_Offset so that different UEs can have the DPCCH transmission phase in their DTX cycles at different times. This offset is common for the Uplink DRX and Downlink DRX schemes, as specified in subclasues 11.1.1 and 11.2 respectively.

The DPCCH is transmitted whenever E-DCH or HS-DPCCH is transmitted. UE_DTX_cycle_1 and UE_DTX_cycle_2 define only the DPCCH DTX during the E-DCH and HS-DPCCH inactivity, and have no impact on the E-DCH or HS-DPCCH ACK/NACK transmissions as if Uplink DRX is not configured as described in subclause 11.1.1, the E-DCH transmission is performed as defined in Rel6. When Uplink DRX is configured, the start times of E-DCH transmissions for new data transmissions can be restricted, after some configurable inactivity time, to a MAC_DTX_cycle which coincides with the UE_DTX_cycle_1.

When the UE is not transmitting data (on E-DCH) or HS-DPCCH, the UE shall not transmit DPCCH except for a short burst of UE_DPCCH_burst_1 subframes once every UE_DTX_cycle_1 subframes. If the UE has not transmitted E-DCH during the last inactivity_threshold_for_UE_DTX_cycle_2 E-DCH subframes, the UE shall not transmit DPCCH except for a short burst of UE_DPCCH_burst_2 subframes once every UE_DTX_cycle_2 subframes. The UE shall DTX if it does not have any data to transmit and when no DPCCH or HS-DPCCH transmission is defined.

Before the uplink DPCCH transmission the UE has to transmit a 2 slots default preamble uplink DPCCH and afterwards a 1 slot postamble uplink DPCCH. In association with UE_DTX_cycle_2 if UE_DTX_long_preamble is TRUE and if there was no E-DCH transmission for the last Inactivity_Threshold_for_UE_DTX_cycle_2 subframes the UE has to apply a longer preamble of (max.) 15 slots before restarting E-DCH transmission.

Discontinuous uplink DPCCH operation may be configured independently on the primary frequency and secondary frequency.

The CQI on HS-DPCCH is transmitted in the HS-DPCCH sub-frames when the CQI reporting period defined transmission overlaps with the DPCCH transmission. However, the RNC can also configure the discontinuous uplink transmission such that the CQI reporting takes priority over the DTX pattern for a number of subframes after an HS-DSCH reception. If there has been no HS-DSCH reception after a configurable period, the DTX takes priority over the CQI reporting. The RNC can also configure a second (longer) CQI reporting period, which is started after a configured number of HS-SCCH TTIs of no transmission to the UE. The normal CQI reporting period is resumed after HS-SCCH transmission is detected by the UE.

The UE only receives the TPC commands on F-DPCH corresponding to actually transmitted UL DPCCH slots.

The serving Node B can command the UE to disable (respectively re-enable) the discontinuous uplink DPCCH transmission and revert back to continuous DPCCH transmission by using a specific HS-SCCH- command.

The Uplink DPCCH burst pattern is illustrated in Figure 11.1-1 for 2ms E-DCH TTI and Figure 11.1-2 for 10ms E-DCH TTI. The uplink DPCCH burst pattern defines the minimum set of slots where the UE shall transmit the UL-DPCCH. Thus the pattern defines the length of the transmission cycle (UE_DTX_cycle_1, UE_DTX_cycle_2), number of slot, and slot position in the transmission cycle that UE shall transmit UL-DPCCH.

Figure 11.1-1: Example for UL DPCCH discontinuous burst pattern for 2ms E-DCH TTI

Figure 11.1-2: Example for UL DPCCH discontinuous burst pattern for 10ms E-DCH TTI

11.1.1 Uplink DRX

The RNC can configure the UE to restrict the start of E-DCH transmissions to the MAC_DTX_cycle pattern, if there has been no E-DCH transmission for a configurable number of TTIs (UE_Inactivity_Threshold). The allowed E-DCH start times can be offset using UE_DTX_DRX_Offset so that different UEs have the allowed E-DCH start time at different time instants.The network should configure MAC_DTX_cycle in such manner that it does not collide with an inactived HARQ process. The uplink DRX cannot be configured without an Uplink DTX configuration as specified in subclause 11.1.

Whenever the UE transmits one E-DCH TTI the UE can use subsequent TTIs for E-DCH transmission as long as its transmission is continued (re-started) within UE_Inactivity_Threshold TTIs, and in addition the pending retransmissions can be done in the corresponding HARQ processes (retransmission times are not impacted by the inactivity threshold).

11.2 Downlink DRX

The downlink DRX is configurable by the RNC and allows the UE to restrict the downlink reception times. The UE may be configured with 1 or 2 DRX cycles of different cycle lengths. When Enhanced Downlink DRX is configured, the parameter Inactivity_Threshold_for_UE_DRX_cycle_2 specifies when the UE shall move from UE_DRX_cycle to UE_DRX_cycle_2. Note that UE is also allowed to receive continuously; discontinuous reception is not required even if it would be configured. Nevertheless, the Downlink DRX cannot be configured without an Uplink DTX configuration as specified in subclause 11.1.

When the discontinuous downlink reception is enabled, the UE is not required to receive physical downlink channels, except if any of the following conditions apply:

1. The UE has received DRX de-activation that was not followed by a DRX activation

2. The UE shall receive E-HICH (sub-)frame corresponding to an E-DCH transmission.

3. The UE shall receive an HS-SCCH subframe due to the HS-SCCH reception pattern.

4. The UE shall receive an HS-PDSCH subframe due to correctly received HS-SCCH

5. The UE has detected an E-AGCH or an E-RGCH subframe transmission from cell(s) in the serving RLS during the required HS-SCCH reception time and the UE still needs to decode the rest of the E-AGCH or E-RGCH frame.

6. The UE has received an HS-SCCH or an HS-PDSCH subframe during the last Inactivity_Threshold_for_UE_DRX_cycle subframes.

7. The UE has sent scheduled E-DCH transmission during Inactivity_Threshold_for_UE_Grant_Monitoring and/or has scheduled data in the buffer for transmission.

The HS-SCCH reception pattern is defined in such a way that the UE must receive one HS-SCCH sub-frame every UE_DRX_cycle or UE_DRX_cycle_2 sub-frames, whichever is in effect. The HS-SCCH reception pattern can be offset using UE_DTX_DRX_Offset so that different UEs have the HS-SCCH reception phase at different times.

The serving Node B can command the UE to disable (respectively re-enable) the discontinuous downlink reception and revert back to continuous downlink reception by using a specific HS-SCCH- command.

The HS-SCCH reception pattern is illustrated by Figure 11.2-1 for a 2 ms TTI E-DCH. The grey subframes correspond to the HS-SCCH reception pattern UE_DRX_cycle=4. The HS-SCCH discontinuous reception radio frame is 10 ms long independently from E-DCH TTI and it is indexed using CFN_DRX. The HS-SCCH discontinuous radio frame is divided to five HS-SCCH subframes are numbered S_DRX=0 to S_DRX=4. S_DRX defines the HS-SCCH reception timing as defined in [4].

Figure 11.2-1: Example for HS-SCCH reception pattern, 2ms E-DCH TTI

The HS-SCCH reception pattern is illustrated by Figure 11.2-2 for a 10 ms TTI E-DCH. The grey subframes correspond to the HS-SCCH reception pattern UE_DRX_cycle=5.

Figure 11.2-2: Example for HS-SCCH reception pattern, 10ms E-DCH TTI

Furthermore, there should be no impact to the UE mobility since the UE cannot DRX if it is required to perform measurements as specified in [5]