owa324020 wcdma hsupa ran12 principles issue1.10.pdf

WCDMA HSUPA RAN11 Principle

Confidential Information of Huawei. No Spreading Without Permission

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This introduces an important feature of 3GPP R6, High Speed Uplink Packet Access (HSUPA). As an uplink (UL) high speed data transmission solution, HSUPA provides a theoretical maximum UL rate of 5.76 Mbps on the Uu interface.

It improves user experience with significantly higher data rate, lower delay, and faster connection setup, which allows operators to offer new services and attract new users.



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Data Services are expected to grow significantly within the next few years. Current 2.5G and 3G operators are already reporting that a significant proportion of usage is now devoted to data, implying an increasing demand for high-data-rate, content-rich multimedia services. Although current Release 99 WCDMA systems offer a maximum practical data rate in Uplink of 384 kbps, the 3rd Generation Partnership Project (3GPP) has included in Release 6 of the specifications a new high-speed, low-delay feature called High Speed Uplink Packet Access (HSUPA).

HSUPA provides significant enhancements to the Uplink compared to WCDMA Release 99 in terms of peak data rate, cell throughput, and latency. This is achieved through the implementation of a fast resource control and allocation mechanism that employs such features as Adaptive Coding, fast Hybrid Automatic Repeat Request (HARQ) and Shorter Physical Layer frames. With the addition of HSUPA, a better balance between Downlink HSDPA and Uplink traffic performance is also achieved.

The High Speed Uplink Packet Access (HSUPA) is a 3GPP Release 6 feature, also called Enhanced Uplink (EUL) or Enhanced DCH (E-DCH).



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Mobile network data rate evolution

WCDMA data transmission evolved from GSM/GPRS, inheriting much of the upper layer functionality directly from those systems. The first commercial deployments of WCDMA are based on a version of the standards called Release 99, with HSDPA introduced in Release 5 to offer higher speed Downlink data services.

Enhanced Data rates for GSM Evolution (EDGE) is another system in the GSM/GPRS family that some operators have deployed as an intermediate step before deploying WCDMA.

Release 6 introduces the High Speed Uplink Packet Access (HSUPA) to provide faster data services for the Uplink.

For HSUPA (Uplink) the theoretical maximum achievable peak data rate is 5.76 Mbps, while for HSDPA (Downlink) it is 14.4 Mbps.



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Release 99 Uplink Packet Data

There are two different techniques defined in the Release 99 specification to enable Uplink packet data. Most commonly, data transmission is supported using either the Dedicated Channel (DCH) or the Random Access Channel (RACH).

The DCH is the primary means of supporting packet data services. Each UE uses an Orthogonal Variable Spreading Factor (OVSF) code, dependent on the required data rate. Fast closed loop Power Control is employed to ensure that a target Signal-to-Interference Ratio (SIR) is maintained in order to control the block error rate (BLER). Macro Diversity is supported using soft handover.

Data transfer can also be supported on the RACH. This common channel employs an OVSF code, with a spreading factor between 32 and 256, as negotiated with UTRAN during the Access procedure. Because it needs to be shared among all UEs, higher data rates are generally not supported. Macro Diversity is also not supported and the channel operates with a fixed (or slow changing) power allocation



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Release 99 Uplink Limitations

Among the available options for Uplink data transmissions in Release 99, the Common Channel (RACH) only allows for a small amount of data and a limited duration of the transmission. Thus, from a practical point of view, the Dedicated Channel (DCH) is the way to accommodate packet services in a Release 99 network. However, significant limitations must also be faced when using the Uplink DCH:

Large Scheduling Delay: In Release 99, the scheduling of resources is done in the serving RNC and involves Layer 3 signaling messages to and from the UE, which causes the mechanism to be relatively slow in assigning or reconfiguring the resources assigned to a particular UE.

Large Latency: The transmission time interval can vary from 80 ms down to 10 ms as best case, posing an intrinsic boundary to the latency values. In addition to that, the only available mechanism for retransmissions of erroneous packets is located in RNC, thus significantly contributing to the latency figures

Limited Uplink Data Rate: Though the standard allows for high data rate on the Release 99 Uplink, typical values of maximum data rate observed in deployed networks range from 64 kbps up to 384 kbps, while using a spreading factor of 4. In order to achieve higher peak data rates, lower coding rates and multi-code transmission shaould be used, but these are not available in R99 systems.



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HSUPA is realized by introducing the Enhanced Dedicated Channel (E-DCH)

In HSUPA, the Node B allows several UEs to transmit at a certain power level at the same time. These grants are assigned to users by using a fast scheduling algorithm that allocates the resources on a short-term basis (every 10ms or 2ms).

The rapid scheduling of HSUPA is well suited to the burst feature of packet service. During periods of high activity, a given user may get a larger percentage of the available resources, while getting little or no bandwidth during periods of low activity.



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Enhancement methods in HSUPA

To overcome the Release 99 limitations previously mentioned, HSUPA has been introduced in Release 6

The use of shorter TTI, fast resource scheduling, and fast retransmissions at the physical layer improves uplink data services, while addressing the release 99 limitations in terms of latency, peak data rate, coverage, and capacity. Additionally, improved quality of service support helps to optimize resource utilization and guarantee the promised quality



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Compared to R99 UL DCH, the enhance DCH specified for HSUPA in Release 6 offers the following features:

Shorter TTI of 2ms: which can reduce the latency and can be scheduled faster

Lower SF: which can increase physical channel symbol rate , higher peak data rate is available

Uplink L1 HARQ throughput: improve physical layer performance with fast retransmissions

New transport and physical channels

Fast resource control: with new MAC entities in NodeB, radio resource can be scheduled faster to optimize the total throughput



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This slide lists some important aspects for comparing HSDPA and HSUPA to help understand HSUPA principles and operation.

The HSDPA concept is based on high speed shared channels with fast L1 HARQ retransmission and rate and modulation adaptation to adjust to channel conditions. The fast scheduler is located in the Node B and assigns the available resources (power and codes) to several users. This enables cell power to be directed to a single user (or to a small group of users) for a short period of time, during which other users do not get any data. In this way, one Node B transmitter can be shared among many UE receivers.

For HSUPA, the channel remains a dedicated channel, but with enhanced capabilities such as fast scheduling and L1 HARQ retransmissions. Power control and soft handover are still used to adapt to radio channel conditions. Because each UE has an independent transmitter with its own power and code availability, the HSUPA scheduler can accommodate many users to be received by the same Node B, where the Rise-over-Thermal Noise level indicates the uplink loading of the system.



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The Rise-over-Thermal noise level is a measure of the uplink load at the NodeB receiver.

By increasing the number of UEs transmitting on the uplink and their transmit power, the overall level of interference in the uplink band also increases.

The NodeB receiver perceives this level as noise, and it directly affects the decoding performance of uplink data transmissions.

The NodeB controls the interference level by adjusting the UE grant assignments according to the current interference level.

When the UE receives a new grant, it uses it in combination with available UE transmit power and amount of data in the buffer to determine the data rate and the corresponding transmit power.



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Similar to HSDPA, HSUPA implements fast resource allocation and control with a scheduler in the NodeB. While the HSDPA scheduler accommodates a common resource to several users, the HSUPA scheduler has a different task: it coordinates the reception of data transmitted from several UEs to a single NodeB. This can be regarded as a very fast resource allocation of a dedicated channel (E-DCH), rather than a sharing of a common channel (HS-DSCH).

On one side, each UE will tend to transmit as much as possible based on channel conditions, the amount of data in the buffer, and the power available. On the other side, the scheduler will try to satisfy each connected UE while preventing overloading and maximizing resource utilization and cell throughput.



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This slide illustrates HSUPA operation :

1. The UE asks the NodeB for a grant to transmit data on uplink.

2. If the Node B allows the UE to send data, it indicates the grant in terms of Traffic-to-Pilot (T/P) ratio. The grant is valid until a new grant is provided.

3. After receiving the grant, the UE can transmit data starting at any TTI and may include further requests. Data are transmitted according to the selected transport format, which is also signaled to the NodeB.

4. After the Node B decodes the data, it sends an ACK or NAK back to the UE. If the NodeB sends a NAK, the UE may send the data again with a retransmission.



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This slide illustrates a data transmission request from the UE through scheduling information (SI), by which the UE asks the Node B for a grant to transmit data on Uplink E-DCH.

UE power availability and UE buffer status are combined to determine the scheduling information.



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This slide illustrates an HSUPA absolute grant assignment upon request from the UE. The grant is determined based on uplink interference situation (Rise-over-Thermal noise) at the NodeB receiver and on the UE transmission requests and level of satisfaction.

The Node B indicates the Traffic-to-Pilot (T/P) grant by downlink grant channel. The grant is valid until a new grant is given or modified.



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This slide illustrates an HSUPA Data Transmission for scheduled grants.

After receiving the grant, the UE can transmit data starting at any TTI and may include additional scheduling information. The transport format is first selected based on the received grant, on the available power and on the data in the buffer.

Data are transmitted on a set of E-DPDCH channels, and transport format Information is signaled to the Node B on the corresponding E-DPCCH. The Happy Bit (Happy Bit indicates the UEs level of satisfaction. ) is also included.



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This slide illustrates the acknowledgment of data at the NodeB and HARQ retransmission.

After the NodeB attempts to decode the data, it sends an ACK or NACK to the UE. If the NodeB sends a NACK, the UE may send the data again with a fast retransmission.



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In a Release 99 PS network, the NAS layer protocols terminate at the SGSN. The RRC, RLC, and MAC protocols terminate at the RNC. The Physical Layer protocol terminates at the NodeB.

The Release 5 specifications define a new sub-layer of MAC for the downlink called MAC-hs, which implements the MAC protocols and procedures for HSDPA. This sub-layer operates at the NodeB and the UE. The location of MAC-hs in the Node B has an important implication for HSDPA operation.

Similarly, the Release 6 specifications define a new sub-layer of MAC for the uplink called MAC-e/es, which implements the MAC protocols and procedures for HSUPA. This sub-layer operates at the NodeB (MAC-e), at the RNC (MAC-es), and the UE (MAC-e/es).

The location of MAC-e in the NodeB has an important implication for HSUPA operation, allowing for fast retransmissions at the physical Layer. The MAC-es, which is responsible for reordering of the data packets, is located in the RNC for HSUPA because a UE may be in soft handover with multiple Node Bs. Transport channel frames are constructed by the MAC sublayer in the UE and sent over the air interface to each NodeB with which the UE is in soft handover. The RNC receives identical transport channel frames from each NodeB over the Iub interfaces and performs reordering.



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HSUPA introduces one new uplink transport channel and two new uplink physical channels.

Enhanced Uplink Dedicated Channel (E-DCH) An uplink transport channel. The E-DCH operates on a 2 or 10 ms Transmission Time Interval (TTI) and carries a single transport block per TTI. The channels is mapped on one or more (up to 4) E-DCH Dedicated Physical Data Channels (E-DPDCHs) and has an associated E-DCH Dedicated Physical Control Channel (E-DPCCH).

E-DCH Dedicated Physical Data Channel (E-DPDCH) An uplink physical channel used to carry uplink data for the E-DCH transport channel. It supports BPSK modulation with I and Q branches and it is allocated every TTI. Up to 4 channels can be used to carry the E-DCH transport channel in a multi-code transmission scheme.

E-DCH Dedicated Physical Control Channel (E-DPCCH) An uplink physical channel for control information associated with E-DPDCH. It carries information about the transport format used on E-DCH and the HARQ retransmission sequence number; it includes one bit to support scheduling decisions at the NodeB.



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HSUPA introduces three new downlink physical channels:

E-DCH Hybrid ARQ Indicator Channel (E-HICH) A downlink physical channel that carries feedback (ACK/NAK) from the Node B on the previous data transmission, to support HARQ retransmission. Since soft handover is supported for HSUPA, each cell belonging to the E-DCH Active Set transmits the E-HICH.

E-DCH Absolute Grant Channel (E-AGCH) A downlink physical channel that carries scheduler grant information from the E-DCH serving cell. The absolute grant indicates directly to the UE the Traffic-to-Pilot ratio that shall be used for scheduled transmissions.

E-DCH Relative Grant Channel (E-RGCH) A downlink physical channel that carries scheduler grant information from cells belonging to the serving NodeB as well as to non-serving cells in the E-DCH active set. The relative grant tells the UE to increase, decrease, or maintain the current Traffic-to-Pilot ratio.



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DCCH and DTCH can be mapped to E-DCH.

A UE using HSUPA can also have additional Release 99 DCH and/or HSDPA channels, although the standard specifies restrictions for the possible combinations. Because power control and soft handover are supported for E-DCH, the channel can be seen as an extension of the Release 99 DCH.

The E-DPCCH, E-HICH, E-AGCH, and E-RGCH are physical layer (control) channels. They carry no upper layer information, and therefore have no logical or transport channel mapping.



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When the UE is operating in HSUPA mode, it uses the E-DPDCH to transmit data on the uplink. Scheduling information also can be included as in-band signaling.

MAC-e PDU Header (HD) Indicates the composition of the MAC-e PDU payload in terms of data descriptor and number of MAC-es PDU included.

Payload Includes the uplink data as MAC-es PDU of the data flow multiplexed in the transmitted MAC-e PDU.

Scheduling Information (SI) SI may be included. SI informs the NodeB about UE buffers, data flow priority, and UE power availability, in order to receive a proper transmission grant.

The E-DPCCH tells the NodeB whether the transmitted block is a new transmission or a retransmission, and which transport format is selected for the E-DCH data channel. An additional bit is also included as feedback on the current resource status.

Control Information Includes a sequence number used to identify retransmitted transport blocks and an indicator of the transport format combination used on the EDPDCH.

Resource Status The E-DPCCH also carries one bit (Happy Bit), which the UE uses to tell the NodeB that the granted data rate is not satisfactory.



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E-AGCH: The Serving HSUPA cell uses the absolute grant channel to tell the UE what power level can be used for data transmission on E-DCH. It consists of the following:

Traffic-to-Pilot Grant Indicates the ratio between the E-DPDCH power and the DPCCH power that the UE can use for E-DCH transmissions. The grant is a value ranging from 0 to 31 and coded in 5 bits. For each value, the standard specifies a Traffic-to-Pilot ratio.

HARQ Control An additional bit indicates the scope of the grant, which can be related only to the current HARQ process, implicitly identified by timing, or can affect all running HARQ processes. In case of 10 ms TTI, the scope can only be All Processes.

E-RGCH and E-HICHEach cell belonging to the E-DCH active set can use the relative grant channel to tell the UE to increase, decrease, or keep the current grant. Each of those cells can transmit the hybrid ARQ indicator channel to tell the UE about the success (ACK) or not (NAK) of the previous data transmission. The channel structure is the same for both channels. Up to 40 channels (20 E-RGCH and 20 E-HICH) can be multiplexed on a single downlink code channel.



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Hybrid ARQ The hybrid ARQ for HSUPA consists of an N-Channels stop-and-wait protocol. The number of HARQ processes is 4 for a 10 ms TTI and 8 for a 2 ms TTI configuration. The retransmission is synchronous, with separate feedback provided for each radio link. After requesting and receiving a grant for data transmissions:

The UE transmits the data of the corresponding HARQ process to all NodeBs for which a radio link exists.

Each Node B connected to the UE sends ACK/NAK back to the UE.

The transmission is successfully completed if an acknowledge (ACK) is received.



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The E-DCH Active Set is limited to 4 cells, one of which is the E-DCH serving cell.

The radio links that are in softer handover with the E-DCH serving cell (i.e., connected to the same NodeB) constitute the Serving E-DCH Radio Link Set (RLS).

All other links in the E-DCH active set, which are connected to other NodeBs, are non-serving radio links.



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The following assumptions are needed to achieve the theoretical maximum data rate of 5.76 Mbps:

Lower channel coding gain Using an effective code rate of 1 increases the data rate, but the channel conditions must be very good for the NodeB to correctly decode every data block on the first transmission.

Lower spreading factor UE must use SF 2.

Multi-code transmission Four codes (2 codes with SF2 and 2 codes with SF4) are used by E-DPDCH.

Shorter TTI 2ms TTI is needed. Because the maximum transport block size is 20000 bits with 10ms TTI, the maximum data rate for 10ms TTI is 2Mbps.

In a practical scenario, the practical maximum data rate will be less than 5.76 Mbps, due to less than ideal channel conditions, the need for retransmission, and the need to share the UE power with other channels.



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The examples presented so far have assumed a turbo code rate of 1/3 and BPSK modulation. If we assume a single E-DPDCH and a transport block containing 640 data bits, rate 1/3 turbo coding produces 1920 symbols. BPSK modulation maps one symbol onto one modulation symbol, which is then spread by the OVSF of length 4. This results in 7680 chips sent every 2ms, corresponding to the fundamental WCDMA chip rate of 3.84 Mcps.

If the transport block is not exactly 640 data bits, the rate matching step adjusts the number of symbols after turbo coding to produce 1920 symbols.

By increasing the coding rate, more data bits can be transmitted in a 2 ms TTI, thus increasing the data rate. Using a coding rate of 1, the data rate becomes 960 kbps, because 1920 bits can be transmitted in 1920 modulation symbols. This corresponds to puncturing all the parity bits and transmitting only the systematic bits.



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By changing the spreading factor from 4 to 2, the number of bits that can be transmitted in a single TTI doubles from 640 to 1280, because now 7680/2 = 3840 symbols can be mapped onto 7680 chips. Again, a coding rate of 1 is assumed.



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What determines the maximum data rate supported by different categories of UE? It is a combination of the maximum number of E-DPDCH channels, the spreading factor, and maximum bits in one TTI.

For 10 ms TTI, a maximum of 2 Mbps peak data rate can be achieved, corresponding to a maximum transport block size of 20000 bits. To achieve higher rates, a TTI of 2 ms shall be used.

With a single E-DPDCH channel, a spreading factor from 256 to 4 is allowed. For multi-code transmissions, only SF4 and SF2 are allowed, in the following combinations: (2 x SF4) or (2 x SF2) or (2 x SF4 + 2 x SF2). Note that SF=2 is not permitted on a single code transmission.



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MAC operation for HSUPA can be described as follows:

The NodeB receives scheduling information from the UE. The scheduling information from UE includes status of data buffers at the UE. It also includes an indication of whether the UE thinks it has adequate resources.

The NodeB determines a grant to allocate to the UE based on the uplink interference measurement and scheduling request from the UE.

Based on the allocated grant by the NodeB, the UE generate a transport block. Data from multiple flows can be multiplexed during this step.

The transport block is delivered to the UE HARQ process for transmissions.

The HARQ process at the NodeB may request for retransmission.

Demultiplexing of the transport block takes place on separate flow.

A reordering function is performed in RNC to reorder PDUs received out of order, and data is finally delivered to RLC.



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As part of HSUPA, MAC-e and MAC-es are added to the protocol stack in Release 6:

The MAC-e, terminated in the UE and in the NodeB, to provide fast retransmission by HARQ mechanism

The MAC-es, terminated in the UE and in the serving RNC, for reordering function

On the UE side, MAC-e/MAC-es is implemented in the terminal; however, on the UTRAN side MAC functionality is split between NodeB (MAC-e) and RNC (MAC-es). Such an architecture is necessary because soft handover is allowed for HSUPA.



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HARQ: HARQ is responsible for storing MAC-e and performing retransmission functionality. RRC configures the HARQ profile, which consists of power offset and the number of maximum retransmissions. The HARQ entity provides the E-TFC, the Retransmission Sequence Number (RSN), and the power offset to be used by Layer 1 (L1).

Multiplexing and TSN setting: MAC-e/es architecture allows multiplexing of multiple MAC-d flows into a single MAC-e PDU. This functionality is performed by Multiplexing and the Transmission Sequence Number (TSN) setting entity. Multiple MAC-d PDUs from a single logical channel are concatenated into MAC-es PDUs; one or multiple MAC_es PDUs can be concatenated into a single MAC-e PDU. The MAC-e PDU thus created is transmitted in the next TTI, as instructed by the E-TFC selection function. It is also responsible for managing and setting the TSN per logical channel for each MAC-es PDU.

E-TFC selection: This entity is responsible for E-TFC selection according to the scheduling information (Relative Grants and Absolute Grants) received from UTRAN via L1, and for arbitration among the different flows mapped on the E-DCH. RRC provides the detailed configuration of the E-TFC entity, over the MAC-Control Service Access Point (SAP). The E-TFC selection function controls the multiplexing function.



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At the UTRAN, MAC is split into MAC-e (in Node B) and MAC-es (in SRNC) entities. There is a single MAC-e entity per UE in every Node B.

E-DCH Scheduling: This entity manages E-DCH cell resources between UEs. Based on scheduling requests received from UE and QoS for various applications, Scheduling Grants are determined and transmitted. Transmission of grants takes place on E-AGCH/E-RGCH(s).

E-DCH Control: This entity is responsible for reception of scheduling requests and transmission of Scheduling Grants.

De-multiplexing: This entity provides de-multiplexing of MAC-e PDUs, which may have been multiplexed into a single MAC-e PDU in the UE for transmissions. MAC-es PDUs are forwarded to the associated MAC-d flow.

HARQ: One HARQ entity can support multiple instances (HARQ processes) of stop and wait HARQ protocols. Each process is responsible for generating ACKs or NAKs indicating delivery status of E-DCH transmissions. ACK/NAKs are transmitted on EHICH.



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At the UTRAN, MAC is split into MAC-e (in Node B) and MAC-es (in SRNC) entities. There is a single MAC-es entity per UE in RNC.

Reordering Queue Distribution: Multiple logical channels may be multiplexed into a single MAC-d flow. The reordering queue distribution function routes the MAC-es PDUs belonging to a single logical channel to the appropriate reordering buffer.

Reordering/Combining: MAC-es PDUs received at the reordering entity are already separated based on the MAC-d flow and the logical channel using DDI. These received MAC-es PDUs are reordered according to the received TSN. MAC-es PDUs with consecutive TSNs are delivered to the disassembly function upon reception. Mechanisms for reordering MAC-es PDUs received out-of-order are left up to the implementation. There is one Re-ordering Process per logical channel. In the case of soft handover, MAC-es PDUs may arrive from multiple NodeBs, which are part of the E-DCH Active Set. The combining function is performed in the MAC-es.

Disassembly: This function extracts MAC-d PDUs from MAC-es PDU and delivers those PDUs to the MAC-d flow.



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The Hybrid ARQ for HSUPA consists of an N-channel stop-and-wait protocol.

The number of HARQ processes is 4 for 10ms TTI and 8 for 2ms TTI respectively. The number of processes required depends on HARQ round trip time (RTT).

The retransmission is synchronous with separate feedback provided for each radio link.

The procedure is as follows:

The UE transmits the data of the corresponding HARQ process to all NodeB for which a radio link exists.

If an acknowledge (ACK) is received ,the transmission is successful.



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The example above is for 2ms TTI. As mentioned earlier, 2ms TTI means 8 HARQ processes are needed for continuous transmission. In this example, two retransmissions are needed for successful transmission of the transport block as a result of two NACKs. Once the second transmission is successful, UE transmit a new transport block on E-DPDCH. The RSN is set to 0 on E-DPCCH to indicate the new transmission to the NodeB.



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The example above is for 10ms TTI. In this example the number of retransmission exceeds 3. Because RSN in only 2 bits, a mechanism is needed to distinguish between retransmitted PDUs beyond 3 retransmissions. This is achieved by using the connection frame number. Additional CFN information is used to determine the redundancy version (RV). For 2ms TTI, CFN is not enough, so the subframe number is used in addition to the CFN to distinguish retransmissions.



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E-HICH is a dedicated channel. Every cell in the E-DCH active set has an E-CHICH set up. Every cell sends an HARQ ACK/NACK for a decoded transport block (MAC-e PDU). The same indication (ACK/NACK) is sent by cells that belong to the same NodeB. If any one cell in the E-DCH active set sends ACK, the UE considers the transmission is successful and sends next MAC-e PDU on that HARQ process.



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The scheduling mechanism for the uplink needs to control the allocation of the UE transmit power and uplink interference.



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Scheduling information (SI) includes the following information: UPH: UE transmission power headroom, 5 bits

Used to indicate the Node B of the power ratio of maximum allowed UE

transmit power to DPCCH pilot bit transmit power.

Then, Node B scheduler knows how much relative power the UE can use for

its data transmission

TEBS: Total E-DCH buffer status, 5bits

Reveals the total amount of data in the UEs transmission buffer.

This information can be used by the scheduler for deciding the data rate the

UE could actually use.

Value range from 0 to 31 to indicate different buffer size ranges

HLID: Highest priority logical channel ID (4bits)

Indicates the highest priority logical channel that has data in the UEs

transmission buffer

HLBS: Highest priority logical channel buffer status (4bits)

Indicate the amount of data in the buffer for the logical channel indicated by

the HLID

The HLID and HLBS can be used by the Node B scheduler for deciding which

UEs should be served first or served with higher data rates

Value range from 0 to 15 to indicate different buffer size ranges

The UE can use Happy Bit to tell the NodeB the resources allocated to the UE is not sufficient and the UE is capable of transmitting at higher data rate.



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From the Happy Bit, the NodeB can know whether the resources allocated to the UE are adequate or not and whether the UE is capable of transmitting at a higher rate.



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The serving E-DCH cell can allocate the traffic-to-pilot ratio grant as an absolute value on E-AGCH.

All the cells in the E-DCH active set can modify the grant value using UP, HOLD or DOWN commands on E-RGCH. UP commands can be sent only by cells belonging to the serving RLS.



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The UE maintains a variable (reference_ETPR) that stores the E-DPDCH to DPCCH power ratio used as reference for relative grant commands. It is set to E-DPDCH to DPCCH power ratio used for the E-TFC selected for previous TTI on this HARQ process. The value is in terms of an index. This index is mapped to the actual value of the grant value (E-DPDCH/DPCCH ratio).

E-RGCH commands may be UP, DOWN, or HOLD. When an up command is received, the increase can be in steps of 1 or 2 or 3. RRC configures two thresholds to determine which step size to use: 2 step index threshold and 3 step index threshold.

If the T/P ratio (E-DPDCH to DPCCH power ratio) used for the E-TFC selected for the previous TTI on this HARQ process is >= 2 step index threshold, the increase is in steps of 1. If the ratio is < (2 step index threshold) but >= (3 step index threshold), then the increase is in steps of 2. If the ratio is < (3 step index threshold), then the increase is in steps of 3. Thus the configuration can be such that if the T/P used for the previous TTI was low, the increase in the T/P grant can be set to a larger step size and the grant allocated to that UE can be increased at faster rate. If the T/P used for previous TTI was high, the increase can be in smaller steps to avoid a sudden increase in UL interference.

When a DOWN command is received, the grant is always reduced in steps of 1.

The slide above shows two examples. In the first example, the serving grant is set to 29 and the UE receives a DOWN command. The grant is then reduced by 1. In the second example, the serving grant is set to 21, the UE receives an UP command, and the 3-step-index-threshold is < current T/P. As a result, the grant is increased by 3.



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For the example above it is assumed that T/P ratio for previous E-TFC is > 2-step-index-threshold. As a result, the increase in the serving grant is by a step of 1.



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A non-serving E-DCH cell can use non-serving grants to control the transmit power of the UEs which are not under its control. A non-serving cell can not increase the serving grant. I can only decrease it (DOWN) or keep the grant same (HOLD). So the non-serving E-DCH cell can control the interference generated by sending DOWN commands.

Consider a scenario where there is only one UE in the serving NodeB and there are several UEs in adjacent cells. The serving NodeB would allow the only UE to increase is uplink transmit power. But this may increase interference caused to the adjacent cell that is already overload. Under such circumstance the non-serving E-DCH cell of the UE will send DOWN commands to reduce uplink interference.



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RTT is round trip time. RTT is 8 HARQ processes for 2ms TTI 4 HARQ processes for 10ms TTI. The example above is for 2ms TTI.



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In the example above the TTI is 10ms.

In the diagram above, the serving grant for HARQ process 4 in not incremented even though the serving E-RGCH command is UP and non-serving E-RGCH is HOLD. This is according to the rule described on previous slide. Once a DOWN command is received from non-serving E-RGCH, it ensures that for one HARQ RTT the serving grant does not exceed the resulting from this DOWN command.



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owa324020 wcdma hsupa ran12 principles issue1.10.pdf

Documents

hsupa uplink

uplink packet data

wcdma release

higher data rate

addition of hsupa

faster data services

wcdma systems

maximum practical data