HSUPA Technology

Content

• HSUPA Basic Principle
• HSUPA Key Technologies
• HSUPA Performance Analysis
• HSUPA Evolution Strategy

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HSUPA Basic Principle

HSUPA Protocol Architecture

• UE: New MAC entity MAC-es/MAC-e is introduced under MAC-d, in charge of HARQ rapid retransmission, scheduling, data multiplexing and E-TFC (E-DCH TFC) selection. 
• Node B: New MAC entity MAC-e is introduced, in charge of HARQ re-transmission, scheduling, and MAC-e de-multiplexing. 
• SRNC: New MAC entity MAC-es is added to provide re-ordering and macro diversity combination in case of soft handover

HSUPA Technical Features

• In UE, dedicated physical data channels (E-DPDCH, at most 4 for each UE) and a dedicated physical control channel (E-DPCCH) to be added in the uplink. Common physical channels (E-HICH, E-AGCH and E-RGCH) to be added in the downlink. 
• E-DPDCH bears uplink data with SF=2 or 4, QPSK modulation and 2ms TTI, it remains 10 ms TTI. 
• E-DPCCH, E-HICH, E-AGCH and E-RGCH accomplish the HARQ and information exchange (including ACK/NACK, uplink grants, and signaling control related to E-DCH) 
• The maximum rate of each E-DPDCH is 1.92 Mbps (2ms TTI, QPSK, SF=2). The maximum traffic rate of each UE is 5.7Mbps. 

MAC layer Architecture in UE side

• New MAC-es/MAC-e entity is introduced to control E-DCH in UE side. in charge of HARQ rapid retransmission, scheduling, data multiplexing and E-TFC (E-DCH TFC) selection.

Structure of MAC-e/MAC-es entity in UE side

Functions of MAC-e/MAC-es entity in UE side

• HARQ entity: control the re-transmission of MAC-e PDU. The copy of MAC-e PDU is saved in the buffer of HARQ entity. The copy of MAC-e PDU will be re-send when the NACK is received from the peer HARQ entity. HARQ protocol is configured by the MAC-Control SAP of RRC。HARQ provides E-TFC, retransmission serial number (RSN) and the power offset used by L1. 
• Multiplexing and TSN setting entity: in charge of multiplexing multiple MAC-d PDUs into one MAC-es PDU, and multiplexing multiple MAC-es PDUs into one MAC-e PDU. Which is processed under the guide of E-TFC selection. It is also in charge of setting and management of the TSN of logical channel. 
• E-TFC selection entity: select the E-TFC according to the scheduling indication (Relative Grants and Absolute Grants) of Node B, and control the Multiplexing. consequently decide the mapping relationship from different MAC-d to E-DCH. E-TFC is configured by the MAC-Control SAP of RRC.

PDU Processing of MAC layer in UE side

Structure of MAC layer in UTRAN side

• In UTRAN side, MAC-e is located in Node B, MAC-es is located in SRNC. 
• MAC-e of Node B is in charge of HARQ retransmission, scheduling, MAC-e de-multiplexing 
• MAC-es of SRNC is in charge of re-ordering and macro diversity combination. 
• MAC-e controls the access of E-DCH, connecting to MAC-es, connecting from MAC-es to MAC-d. 
• New connection is defined in MAC-e and MAC Control SAP, also in MAC-es and MAC Control SAP.

Function and Structure of MAC-es in UTRAN side

Function entity of MAC-es in SRNC side:

• Re-ordering queue distribution entity: routing MAC-es PDU to the correct re-ordering buffer according to the configuration of SRNC. 
• Re-ordering entity: re-ordering the received MAC-es PDU according to the received TSN and Node B ID. 
• Macro diversity selection entity: selective combining for MAC-es PDU from multiple Node B in case of soft handover. 
• MAC-es PDU disassembling entity: disassemble MAC-es header, transmit MAC-d PDU to MAC-d layer.

Function entity of MAC-e in Node B side:

• E-DCH scheduling and control entity: base on the scheduling request SR (Scheduling Request) from UE, allocate resource for UE, and notify UE though downlink resource indication. 
• De-multiplexing entity: de-multiplexing MAC-e PDU, and save the de-multiplexed SI which is referenced by E-DCH scheduling entity. 
• HARQ entity: processing multiple stop-wait :HARQ processes, produce ACK or NACK, indicate if the data transmitted on E-DCH is correct, count the times of re-transmission which is referenced by Scheduling entity.

HSUPA new transmission channel E-DCH

• E-DCH attributes 
• E-DCH and DCH use separated CCTrCHs. 
• Each UE only has one CCTrCH with E-DCH type. 
• Each CCTrCH with E-DCH type only has one corresponding E-DCH. 
• Each TTI only has one transmission block. 
• E-DCH supports 2ms TTI and 10ms TTI, 10ms TTI is mandatory to all UE, 2ms TTI is optional. 
• Adopts Turbo 1/3 coding method. 
• After E-DCH is allocated, the data rate of original uplink DCH will be restricted in 64kbps.

Both uplink logical channel DCCH and DTCH can be mapped to E-DCH

HSUPA new physical channel

• Five physical channels are added in radio interface to support rapid re-transmission, soft combination and Node B distributing scheduling in physical, these five physical channels all support 10ms TTI and 2ms TTI. 
• E-DPDCH: E-DCH Dedicated Physical Data Channel (uplink). 
• E-DPCCH: E-DCH Dedicated Physical Control Channel (uplink). 
• E-HICH: E-DCH HARQ acknowledgement Indicator Channel (downlink). 
• E-AGCH: E-DCH Absolute Grant Channel (downlink). 
• E-RGCH: E-DCH Relevant Grant Channel (downlink).

Uplink dedicated physical channel E-DPDCH and E-DPCCH

E-DPDCH is a uplink dedicated physical data channel to bear the data of E-DCH

• Bear HSUPA uplink data. 
• Alterable SF＝2～256. 
• Adopt QPSK modulation. 
• Support 10ms TTI and 2ms TTI. 
• Each radio link has one or multiple E-DPDCH.

E-DPCCH is a uplink dedicated physical control channel bearing control information of E-DCH

• Bear HSUPA uplink control information. 
• Fixed SF＝256. 
• Adopt QPSK modulation. 
• Support 10ms TTI and 2ms TTI. 
• Each radio link has one E-DPCCH.

Downlink common physical channel E-AGCH

E-AGCH is a downlink common physical channel to bear the absolute grant of E-DCH

• Adopt fixed SF=256, the channel speed is 30kbps. 
• E-AGCH is only existing in serving E-DCH cell. 
• Absolute Grant of E-DCH is only transmitted in serving E-DCH cell. 
• Absolute Grant can be transmitted in one sub-frame (2ms TTI) or one radio frame (10ms TTI). 

Downlink dedicated physical channel E-RGCH

E-RGCH is a Downlink dedicated physical channel to bear the relative grant of E-DCH

• Adopt fixed SF=128. 
• A relative grant can be transmitted in 3, 12 or 15 continuous time slots. 3 and 12 time slots are corresponded to 2ms TTI and 10ms TTI in serving E-DCH cell, 15 time slots is used in non-serving E-DCH cell.

Downlink dedicated physical channel E-HICH

E-HICH is a Downlink dedicated physical channel to bear the HARQ acknowledgement Indicator of E-DCH

• Adopt fixed SF=128. 
• A HARQ acknowledgement Indicator can be transmitted in 3 or 12 continuous time slots, which are corresponded to 2ms TTI and 10ms TTI. 
• E-HICH and E-RGCH have the same SF and radio frame structure, they are differentiated by different signature sequence.

Basic Concept

HSUPA basic principle

HSUPA basic working process

Establishing process of dedicated channel E-DCH

• UE sends service request to network side as the same process of R99/R4. 
• Upon receiving RAB establishment request, the SRNC determines to select uplink E-DCH according to service attributes and sends the RL SETUP message to NodeB. The RL SETUP message indicates which RL is the E-DCH RL and which RL is the serving E-DCH RL. 
• After establishing RL, the NodeB sends RL SETUP response to RNC. The response message contains the E-AGCH/E-RGCH/E-HICH scramble and channelization code, and E-RGCH/E-HICH signature sequence. If the RLs contain the serving RL, the NodeB allocates E-RNTI to the UE. The response message also contains the E-RNTI. 
• The RNC sends UE the RB SETUP message, carrying E-RNTI, mapping relationship between RB and Mac-d Flow, E-TFCS, Mac-d Flow, E-AGCH/E-RGCH/E-HICH code resource and signature information. 

E-DCH scheduling process 

• UE has a E-DCH serving cell, the scheduling is processed by the Node B which the E-DCH serving cell belongs to. E-DCH serving cell sends scheduling command to UE by E-AGCH, that is Absolute Grant, AG limits the maximal resource that UE can use, AG includes the E-RNTI of UE, and the maximal transmitting power that UE allows, etc. 
• E-DCH serving cell and E-DCH non-serving cell send Relative Grant though downlink channel E-RGCH, Relative Grant is a offset to Absolute Grant (tiny tuning), its value can be “Up”, “Hold”, or “Down“. Serving E-DCH RLS can sends all these 3 values. Non-Serving E-DCH RLS can only send “HOLD” or “DOWN”. Usually, the reason of sending “DOWN” by non-Serving E-DCH RLS is uplink overload.

E-DCH data transmission and retransmission process

• According to the grant information received, the UE selects E-TFC. It sends data (including data resent) in E-DPDCH, and E-TFC information, HARQ RV information (RSN), and a Happy bit in E-DPCCH. The Happy bit notifies Node B whether the UE is satisfied with the current resources (grant) allocated, that is, whether higher grant is required. 
• Firstly, the E-DCH data received from the different cells under the same Node B of E-DCH Set is combined (MRC Combination), and then the data is sent to Mac-e for processing. Each UE has a Mac-e in each Node B. The Mac-e de-multiplexes the Mac-e PDU to MAC-es PDU and sends it to RNC. The Mac-e also sends E-DCH scheduling information and the ACK/NACK of HARQ. 
• Each UE has a Mac-es entity in SRNC. When receiving MAC-es PDUs from different Node Bs, the Mac-es performs macro diversity combination, re-sorts their order, divides them into Mac-d PDUs, and sends them to Mac-d. 
• HARQ process: The UE sends HARQ RV (retransmission serial number, RSN) through uplink E-DPCCH. The Node B sends the ACH/NACH through downlink E-HICH.

HSUPA physical channel forming process

HSUPA UE Category

HSUPA Key Technologies

• HARQ – Fast Hybrid Automatic Repeat Request 
• HARQ is an error correction technology. The "hybrid" is the combination of forward error correction (FEC) and automatic repeat request (ARQ) 
• HARQ function is located in MAC-e entity of Node B and UE. 
• The fast HARQ of HSUPA is implemented by adding an HARQ functional entity in Node B. If data is not received correctly, the Node B will request the UE to resend the uplink packet data. 
• In uplink, HARQ adopts the N channel Stop And Wait (NSAW) protocol. 
• In HSUPA, 10ms TTI corresponds to 4 HARQ processes, and 2ms TTI to 8 HARQ processes.

HARQ - Reduce transmission delay and improve throughput of UE and system

HARQ re-transmission combination

• The forward error correction of uplink HARQ provides two modes, namely, Chase Combining (CC) and Incremental Redundancy (IR) 
• The information resented by CC mode has the same content as the original information, which is processed with maximal ratio combining before UE decodes it. Thus, the decoding grain is increased. 
• The IR retransmission supports two retransmission modes: 
• The IR enables different redundancy information to be sent in retransmission. Thus, the data cannot be decoded unless the data sent by the first time and that retransmitted are combined. 
• The IR also enables the same redundancy information to be sent in retransmission. However, that information can be self-decoded. With incremental redundancy given in each HARQ retransmission, the forward error correction capability is enhanced.

Node B uses different ways to combine the multiple retransmissions of a single packet, decrease the receive Ec/No of each transmission. With HARQ, HSUPA can effectively increase data transmission rate and shorten transmission delay.

Retransmission comparing between HSUPA HARQ and R99 RLC

• The fast HARQ may cause higher target block error rate (BLER) in the first transmission, because it enables shorter delay in resending the packets that are not correctly received previously compared with RLC retransmission. 
• The higher BLER target can reduce the transmit power that is required by the UE in transferring the data of certain rate. Therefore, for the same cell load, the fast HARQ can increase the cell capacity. 
• When the data rate is fixed, the energy decreasing of each bit can improve the coverage. 

Uplink HARQ Soft Handoff

• In CDMA system, the software handoff gain is generated when a Node B receives packets correctly, while another Node B cannot decode. 
• In the soft handoff of HSUPA HARQ, one Node B sends acknowledgement (ACK) to the UE, while the other one sends negative acknowledgement (NACK). In this case, the network already receives the packet, and the UE should not sent the same packet. Accordingly, the HARQ process of the Node B that receives packet incorrectly can resume from the reception failure. The RNC must ensure the sequence of the packet and send it to the upper layer, and performs selective combination of the packets received from different Node Bs.

• In the process of SHO, UE can perform retransmission only when all Node Bs in the active set can’t decode correctly, otherwise, UE will not perform retransmission if there is one ACK. 
• SHO enables link diversity gain, improves throughput effectively, and reduces retransmission times.

Fast Packet Scheduling

• To R99/R4/R5, packet scheduling is based on RNC. 
• In HSUPA, the scheduling is located in Node B, and the scheduling period can be 2ms, to implement fast scheduling strategy, thus, the uplink air interface capacity can be effectively utilized.

• The packet scheduling controlled by RNC will cause some delay, so the change of current channel can not be reflected quickly, thus, the fast link self-adaptation and fast packet scheduling can not be performed. 
• In HSUPA, the packet scheduling entity of Node B can directly use real-time measurement information of physical layer, inner statistic information and the information reported by UE to perform scheduling, thus, to reduce the system transmission delay by utilizing the situation of channel and fading attribute of different users.

Fast Uplink Packet Scheduling

Uplink and downlink radio packet scheduling have the different complication of resource controlling.

• In downlink: Node B can easily get the information of buffer occupation of each service streaming, and the downlink power is central controlled, so Node B can allocate and free the power resource accurately, thus to control the system load efficiently and ensure the QoS of each service. 
• In Uplink: the time delay and uncertainty are existed in uplink service streaming cause the information of it need to be reported to Node B by radio channel. In uplink, each UE has its own power source, because of the time variability of radio channel and the limitation of code resource, the accurate control of uplink system resource (total uplink power) became more complicated, so as to the uplink packet scheduling.

The function of Node B scheduler:

• As serving Node B, Allocate uplink resource to the UEs under serving E-DCH cell. 
• As non-serving Node B, detect the interference of other cells and send relative grant information to UEs. 
• Notify SRNC while there is short of processing resource.

Uplink Packet Scheduling Model

• In order to confirm the uplink transmission rate and transmitting power, some information of user must be known like the situation of serving streaming and available power, etc. which is named SI (Scheduling Information). 
• SI is periodically reported in HSUPA, and the period of report is integral times of TTI, SI is multiplexed with packet data. 
• Node B allocates uplink resource to user according to the SI information multiplexed from received data, that is, Node B sends resource indication of scheduling Absolute Grant by downlink AGCH channel.

Scheduling Resource Compensation Mechanism

The shortage of SI transmission

• The error of SI transmission is unavoidable and the report is unreliable cause of being transmitted by the radio channel. 
• Node B adopts periodical scheduling, but the SI may be not accurately reflect the UE situation at real time. 
• While the situation of radio channel is bad, the SI will not be received correctly before it has been multiple retransmitted. That causes time delay.

Compensation Mechanism

In HSUPA, Node B performs tiny tuning to the resource allocated to UE by sending Relative Grant through RGCH channel

Scheduling Resource Compensation Process

• UE reports Happy bit to Node B in E-DPCCH, Happy bit has 1 bit to indicate if UE is satisfied with the allocated resource. After UE received the resource indication, it will make a judgment according to the following principle: 
• UE has surplus power for the scheduling resource. 
• The required time for transmitting all the data in buffer will exceed 1 TTI by using the allocated power resource. 
• UE will express its “un-satisfaction” to Node B by Happy bit, and will require more resource to be allocated. 
• If UE report “satisfy”, then Node B will indicate to keep the current allocated resource.

Packet scheduling is not simply adjust the resource of UE according to the situation of UE, it will integrate with the system load, channel state and QoS of different service, etc. it’s a balance between system indices (system throughput, fairness) and service QoS (time delay, packet missing rate).

Packet Scheduling Priority Allocation

• In the process of packet scheduling, the most important thing is how to decide the sequence for the users who are striving for resources, so the system resource can be efficiently utilized, the system throughput will reach its maximum state, and try best to make every user satisfied. 
• In 3GPP, there are two arithmetic that determine the performance boundary. 
• One is base on C/I, it provides maximal system throughput while lost its fairness. 
• Another is RR, it provides equal chance to every user, but the system throughput is bad. 
• The popular scheduling arithmetic include Round Robin, Max C/I and Proportional Fair, they all can be regarded as scheduling base on Priority, but their allocation strategy is different.

Uplink Noise Rising probability

Comparison of Uplink Noise Rising probability between RNC scheduling and Node B scheduling

• The obvious reduction in scheduling period enables the uplink air interface capacity to be better controlled dynamically, and the resource of air interface will be effectively utilized. 
• The potential advantage is that the running target of uplink load can be more approached to the maximal level of load, but it will not improve the probability of overload, thus, the probability of uplink noise rising is lower than that caused RNC scheduling.

Effect of Fast Packet Scheduling on Maximum Expected Load 

• The probability of uplink load target is much more near that of maximum load limit when the marginal load area becomes smaller (The Prx_target is more closer to the Prx_threshold. The Prx_threshold is the overload threshold). 
• The Node B-based scheduling requires the information related to UE uplink transmission demand. The UE should be informed of the current data rate allowed through fast signaling within specified time. 
• To RNC, these operations are implemented through RRC signaling, the response speed of which is restricted obviously.

2ms TTI

• As a option, a shorter 2ms TTI is described in uplink of HSUPA to decrease the HARQ retransmission delay. 
• When each TTI contains the same amount of data, the energy transmitted in 2 ms is less than that in 10 ms possibly, and the interleaving gain decreases. Therefore, to ensure normal operation in cell edge, 10 ms TTI must be used. 
• when there is no other constraint like link coverage, 2ms TTI helps increase system capacity. In favorable radio environment, 2ms TTI can bring higher peak rate. 

HSUPA Performance Analysis

Influence of the Introduced HSUPA on Original Network

Influence of HSUPA on Network includes:

• Occupy downlink code resource. 
• Occupy downlink power resource. 
• increase the uplink interference of network, impact on link budget, capacity and coverage. 
• impact on terrestrial transmission bandwidth.

Influence of the Introduced HSUPA on R99/R4/R5 

• The new function, new physical channel and new MAC entity are added. The data rate in the uplink is enhanced. It is necessary to upgrade the software of Node B and RNC. It also requires the new terminal to support the HSUPA. 
• Higher data rate may require higher baseband capacity and function. It may be necessary to change the hardware in Node B and RNC, but not compulsory.

Influence on Iu* Interface:

• Influence on Iub/Iur Interface: 
• Control plane: Add the IEs that are related to configuring and controlling E-DCH channel and resource, and the Node B scheduling operation and MAC Multiplexing, etc. 
• User plane: Add new frame structure for E-DCH, support 2ms and 10ms TTI. 
• Influence on Iu Interface: there is no influence on Iu interface.

Influence of HSUPA on Network Planning – Coverage and Link Budget

• In consideration of the fact that the HSUPA provides the uploading service for VIP customers in core urban areas, it is advisable to select the dense urban area model to conduct HSUPA link budget. 
• In order to conduct the planning comparison with R99, here we compare the typical uplink service of the independent R99 planning with the link budget of the HSUPA uplink service and analyze them. 
• There is sufficient reservation for the shadow margin and the penetration margin in the table in order to reflect the dense urban area model. The COST231 path loss model is also used in calculating the coverage radius.

4 modes are set by HSUPA, the detail information of HUSPA of each mode is:

Uplink Link Budget Comparison between HSUPA and R99

Uplink Link Budget Comparison and Analysis between HSUPA and R99

The interference margin of R99 link budget that the prior table corresponds to is 3dB, and that of HSUPA is 6dB (HSUPA can more effectively control system overload probability under the same average interference margin requirement).

• As shown in the prior table, the 12.2k, 64k service of R99 almost have the same coverage, the radius of dense urban is about 450m, the distance between two sites is about 780m. The low speed HSUPA service (mode1) can have the same coverage as 12.2k. 
• In mode2, it is very hard to bear 480kbps, because there is only one SF code. And the radius of coverage is shrunk to about 240m. 
• In mode3, for the bearing speed is improved and the SF code is increased to 2, the radius of coverage can be kept in about 240m. 
• For the high speed uplink service (mode4), the bearing speed is improved to 2Mbps with 2 SF codes, And the radius of coverage is shrunk to about 190m.

Link Budget Comparison of HSUPA/R99 in Co-frequency Networking Mode 

• According to link budget, under the co-frequency situations, the introduction of the relatively high interference margin threshold causes R99 service coverage radius shrinkage. The 12.2k service radius shrinks by 10% ~ 20%. In this network planning, HSUPA 64k service, or service whose rate is slightly higher than 64k can reach the whole network coverage. The peak 1,920 kbps service coverage radius can reach 50% of the planned cell radius, that is, it can cover about 25% of the area of the whole cell. 
• Through the above analysis, it can be known that the low speed HSUPA service (Mode 1) can basically guarantee to maintain the same coverage relation with planned R99 coverage range when HSUPA and R99 jointly conduct the uplink planning. When HSUPA user rate rises, its service coverage shrinks. At the same time, as the HSUPA is introduced, in co-frequency construction, planned R99 range will somewhat shrink.

Summary of HSUPA impacting on Network Planning and Analysis 

HSUPA impacting on Network Planning and Analysis includes:

• HSUPA network construction strategy: Cover the whole network with relatively low rate. Focus on the coverage of dense urban areas, to ensure the high rate of uplink transmission in hotspot areas. It is recommended that for the planning the initial stage, it is advisable to refer to HSDPA coverage range, conduct key coverage in hotspot areas, and just conduct the low speed coverage in the edge areas of common cell. 
• In HSUPA planning, under the conditions that the same overload probability is ensured, and RRM control algorithm is further optimized, in order to enhance uplink throughput, in setting uplink interference margin, it is recommended not to use the common R99 uplink 3dB as the noise raise threshold, and the value 5 ~ 6dB is recommended. 
• In the co-frequency planning of HSUPA and R99, if the interference margin threshold is raised, it will cause the previous R99 uplink planned budget radius to shrink. As to how much it will shrink specifically, it is necessary to conduct subsequent and further study. From link budget analysis, it shrinks by about 10 ~ 20%. In inter-frequency networking, there is basically no influence on R99 uplink planning. 
• Via the link budget, it can be known that HSUPA 64k service budget radius is slightly smaller than R99 12.2k and 64k service radiuses under the inter-frequency HSUPA networking conditions; HSUPA 64k service budget radius is slightly bigger than R99 12.2k and 64k service radiuses under the co-frequency networking conditions. Analyzed in a comprehensive manner, the low speed HSUPA service can implement the same coverage with the planned R99 range.

HSUPA theoretic data rate

HSUPA Enhanced Uplink Dedicated Physical Channel E-DPDCH supports SF=2～256, and multiple channels. Adopts QPSK modulation and coding rate 1/3 (turbo). If the coding rate is 1, then the maximal transmission capacity of Enhanced Uplink Dedicated Physical Channel is up to 5.76Mbit/s by data rate matching arithmetic。

Remark：Coding rate=NINF/ NBIN
NBIN=3840 / SF x TTI sum for all channels

HSUPA data rate transmission efficiency 

HARQ Influence

• HSUPA complies with the HARQ protocol, generating performance gain for EDCH via link level retransmission and retransmission times. As the fast feedback retransmission of the physical layer reduces the RLC retransmission and the corresponding delay, it is possible to effectively improve the service experience of end users. It can enable HSUPA physical channel to work in the channel whose bit error ratio is relatively high, thus improving the system capacity. 
• When the uplink uses the inner loop power control, the retransmission ratio of the initial transmission can reach 10-30% to maintain the given quality grade. A large quantity of retransmission will lead to the decline of the throughput of end users, while excessively low retransmission ratio will not generate any gain of any relatively previous version for the HARQ controlled by Node B. Soft combination can further improve the system performance of HARQ mechanism controlled by Node B. 
• The HSUPA adopts the synchronous HARQ, and there are strict timing relations for the operations of different HARQ processes. The synchronous HARQ effectively lowers the signaling overhead caused by HARQ operation, thereby improves system capacity. 
• HARQ is mainly used in interactive, background and streaming services. Therefore, to adopt HARQ in HSUPA, attention should be focused on the following: 
• Delay reduction 
• More users and improvement of system throughput

• In the HARQ protocol, it is necessary to retransmit the data that can not be correctly received. And it is possible to generate the gain in throughput for the UE whose transmission power is limited by using Soft Combining, and the retransmission times can be effectively reduced. 
• The algorithm which adopts the soft combining brings much more gain than that which does not adopt the soft combining. This is because that the soft combing fully utilizes the bit information of the previous transmission. Therefore, the gain is more remarkable when the Ec/No is relatively low.

• When macro diversity technology is adopted, the UE will conduct the retransmission only when no Node B in all the activated sets can correctly decode the data. Otherwise, the UE will not execute the retransmission as long as there is one ACK. 
• Adopting macro diversity brings remarkable performance gain, effectively improves throughput, and reduces the retransmission times.

HSUPA cell performance analysis 

HSUPA cell performance analysis is evaluated in the following aspects: The average throughput of cell, average throughput of a single user, UE scheduling fairness, service delay and RoT overload rate

• HSUPA cell throughput demonstrates the function relationship between the average RoT of the cell and the system throughput. Besides being influenced by such factors as the UE quantity, the geographical position where the UE is located and the wireless propagation condition, UE data transmission request, and the uplink interferences of the cells around it, it is also influenced by different wireless and packet scheduling polices and scheduling algorithm. 
• The fairness curve refers to the density accumulation distribution function of the normalization of user throughput by the average throughput of each user, and it reflects the scheduling fairness. 
• The service delay includes the packet call delay and packet delay. The packet call delay refers to the time period between two consecutive packet transmission requests. For the FTP user, the packet call delay refers to the time the FTP uploads the file. The packet delay refers to the time necessary for the reception of the packet message at Node B. 
• RoT overload ratio reflects the ratio of RoT when it exceeds a certain designated RoT threshold value

Influence of 2 ms TTI on system performance

Influence of HARQ on system performance

We conduct the simulated analysis on the influence of HARQ on the average throughput of the cell when HARQ is on and when it is off. It can be seen that due to the adoption of HARQ and the soft combining technology, the link spectrum efficiency is improved, and the cell throughput is improved by at least 200kpbs. This corresponds to the improvement of HARQ to link performance.

Influence of Soft Handover on System Performance

We analyze, via simulation, the influence on the average throughput of the cell in the system when there has soft handover (includes softer handover) and when there is no soft handover. It can be seen that due to the adoption of soft handover technology, the link diversity gain is generated, and the cell throughput is improved by at least 120 kpbs.

HSUPA Evolution Strategy

Radio Communication Technology Development Overview

• The radio communication development process from 2G, 3G to 3.9G, is that of developing from mobile voice service to high speed data service. 
• Nowadays the radio communication technology is evolved to 3.5G, to WCDMA, it can provide commercial R5 version and trial R6 version. 
• The R7/HSPA+ and R8/LTE standards are being consummated by 3GPP, it is forecasted that the R7 will be frozen in 2007, R8 will be frozen in 2008. 
• To the development of radio communication technology, more attention should be paid to the requirement of operators – the development target of system from NGMN group

Radio Communication Technology Evolution

UMTS Technology Evolution Roadmap

End of Course