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Only the UE has accurate knowledge about the buffer situation and power situation in the UE at the time of transmission of the transport block in the UL. Hence the UE is allowed to autonomously select the data rate or E-TFC.

E-TFC is responsible for selecting the TF of the E-DCH and to control MAC-e multiplexing.

NodeB scheduler handles resource allocation between UEs, the E-TFC Selection controls resource allocation between flows within the UE.

E-DCH needs to be coexist with DCHs. Therefore a basic requirement is to serve DCH traffic first and only spend otherwise unused power resources on the E-DCH.
TFC Selection is two step process. First the normal DCH TFC selection is performed then UE estimates the remaining power and TFC Selection step is performed where E-DCH can use the remaining power.

Physical Layer Processing

Channel Structure with HSDPA and HSUPA

E-HICH -> HARQ ACK/NAK information is sent on a new downlink dedicated physical channel, the E-DCH Hybrid ARQ Indicator channel.

E-AGCH -> Scheduling grants sent from the scheduler to the UE, using the shared E-DCH Absolute Grant Channel.

The E-AGCH is sent from the serving cell only as this is the cell having main responsibility for the scheduling operation and is received by all UEs with an E-DCH configured. It is typically used for large changes in the data rates

E-RGCH -> Scheduling grant information can also be conveyed to the UE through and E-DCH Relative Grant Channel. It is typically used for small adjustment during on going data transmission.

E-DPCCH -> In the uplink, control signaling is required to provide the NodeB with the necessary information to be able to demodulate and decode the data transmission.

Even though serving cell has this information but non serving cells in soft handover clearly don't have this information. Also E-DCH also supports non-scheduled transmission. Hence there is a need of out-band signaling in UL.

E-RGCH -> Scheduling grant information can also be conveyed to the UE through and E-DCH Relative Grant Channel. It is typically used for small adjustment during on going data transmission.
E-DPCCH -> In the uplink, control signaling is required to provide the NodeB with the necessary information to be able to demodulate and decode the data transmission. Even though serving cell has this information but non serving cells in soft handover clearly don't have this information. Also E-DCH also supports non-scheduled transmission. Hence there is a need of out-band signaling in UL.

A new transport channel type is introduced Enhanced Dedicated Channel (E-DCH). It can be configured with one or several DCHs.

Introduction of 2ms TTI for efficient packet-data support. It allows for rapid adaptation of transmission parameters and reduction of the end-user delays associated with packet-data transmission.

But for large cells a longer TTI may be beneficial as the payload in a 2ms TTI can become unnecessarily small and the associated relative overhead too large. Hence the E-DCH supports two TTI lengths, 2 and 10ms and the network can configure the appropriate value.

It provide robustness againt occasional transmission errors. A similar scheme as for HSDPA

One main difference compared to HSDPA from the use of soft handover in uplink.
When UE is in soft handover, HARQ is terminated in multiple cells.

It is possible that few NodeB has not received data correctly and some NodeB has received correctly. So If the UE receives an ACK from at least one of the NodeBs, the UE consider the data to be successfully received.

Scheduler at NodeB controls when and at what data rate the UE is allowed to transmit.

-High date rate ≈ High Power transmitted by Ues
-High Power ≈ Higher Interference (due to UL non
orthogonality)
Scheduler needs to manage the UL interference
-If Interference is too high, UL transmission may not received properly.
-If interference is too low, the full system capacity not exploited.

Since the scheduler and transmission buffer are not co-located, there is Request/Grant mechanism is defined. UE sends the Scheduling Request, indicating its buffer occupancy.

Scheduling Grant sent by the UEs to control the UE transmission activity. The Scheduling Grants control the maximum allowed E-DCH-to-pilot power ratio the terminal may use; a large grant means higher data rate but also contributes more to interference level in cell.

As the interference increases in the cell, it affects the neighbor cell also, so inter-cell interference needs to be controlled.

The scheduler has allowed a UE to transmit at a high data rate based on an acceptable intra-cell interference level, this may cause non-acceptable interference to the neighboring cell.

Therefore in soft handover, the serving cell has the main responsibility for the scheduling operation, but UE monitors scheduling information from all cells with which the UE is in soft handover.

Difference Between the HSDPA and HSUPA

High Speed Uplink Packet Access (HSUPA) is also known as Enhanced Uplink.

What it Does ?

Provides the Improvement in WCDMA uplink capabilities and performance in terms of

Higher data rates
Reduced Latency
Improved System Capacity

It is a complement to HSDPA

Enhanced Uplink is specified in 3GPP Release 6 and has been extended with additional transport and control channels, such as the enhanced dedicated channel (E-DCH), and with similar features to HSDPA. Enhanced Uplink will cater for the needs of mobile broadband with increased performance in the uplink: it will provide up to 5.8Mbps in the uplink, reduced delay and 150-200 percent greater system capacity.

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