A Presentation on WCDMA -3rd Generation Technology.

A Presentation on WCDMA -3rd Generation Technology.Basics and Architecture and Functionality.History and Access TechnologyThe third generation mobile communication system (3G) was first put forward by ITU in 1985 and named future public land mobile telecommunication system (FPLMTS) at that time.

In 1996, it was renamed international mobile telecommunication -2000 (IMT-2000) . IMT-2000 means that the system works on the 2000 MHz band, supports up to 2000 kbps service rate, and will be put into commercial use in 2000. The main systems include WCDMA, CDMA2000 and TD-SCDMA.

For FDMA system, the frequency separation needs to be enough to avoid mutual interference between different users.

In TDMA when a user wants to send any information, he should first cache the information and waits for his timeslot to come. When the timeslot arrives, the information is transmitted at a burst-oriented transmission.

CDMA is a multiple access mode implemented by Spread Spectrum Modulation. Unlike FDMA and TDMA, both of which separate the user information in terms of time and frequency, CDMA can transmit the information of multiple users on a channel at the same time.

That is to say, mutual interference between users is permitted. The key is that every information before transmission should be modulated by different Spread Spectrum Code-Sequence to broadband signal, then all the signals should be mixed then send. The mixed signal would be demodulated by different Spread Spectrum Code-Sequence at the different receiver. Because all the Spread Spectrum Code-Sequence is orthogonal, only the information that was be demodulated by same Spread Spectrum Code-Sequence can be reverted from the mixed signal.

3Difference between WCDMA and GSM

Frequency division duplex (FDD) : Distinguish the uplink and downlink according to the frequencies. Adopted by the WCDMA, CDMA2000 and GSMAdvantage: It can be easily implemented.Disadvantage: The spectrum utilization is low when the uplink and downlink services (mainly the data services) are asymmetrical.

Time division duplex (TDD) : Distinguish the uplink and downlink according to the timeslots.Adopted by the TD-SCDMAAdvantage: The uplink and downlink can be allocated with different numbers of timeslots when the uplink and downlink services are asymmetrical. Therefore, the spectrum utilization is high. Disadvantage:It cannot be easily implemented and needs precise synchronization. In the CDMA system, GPS synchronization is needed. When it is used with the CDMA technology, it is difficult to control interference between the uplink and the downlink.

4Narrow band VS Wide band

The AMR-WB codec operates on nine speech-coding bit-rates between 6.6 and 23.85 kbps. The term wideband comes from the sampling rate, which has been increased from 8 kHz to 16 kHz. This allows one to cover twice the audio bandwidth compared with the classical telephone voice bandwidth of 4 kHz. While all the previous codecs in mobile communication operate on a narrow audio bandwidth limited to 2003400 Hz, AMR-WB extends the audio bandwidth to 507000 Hz.5Standardization and commercial launch

Types of Services in WCDMA

Network Elements

UMTS Terrestrial Radio Access Network .(UTRAN) Node B (Base Station): Handles/manages the traffic ,between Uu and Iub interfaces. Basic tasks like coding, interleaving, rate adaptation, modulation, spreading etc. Radio Network Controller (RNC): Control radio resources in its operation area. Provide services for Core Network (CN). Load and congestion control, admissions control, code allocation, radio resource management tasks.8Channel Coding in WCDMA

Users who need to send information: UE1, UE2 and UE3UE1 uses c1 for spreading: UE1 c1UE2 uses c2 for spreading: UE2 c2UE3 uses c3 for spreading: UE3 c3c1, c2 and c3 are mutually orthogonal.Information sent: UE1 c1+ UE2 c2+ UE3 c39Symbol and chip stream.

Spreading

Different users adopt different spreading code words, such as x1(t) , x2(t) .Self correlation determines multipath interference. Mutual correlation determines multiple access interference. Self-correlation functionR() =Mutual-correlation functionV() =

Multiple access interference is caused by different code words between users. Therefore, mutual correlation of code words determine multiple access interference. Multipath interference is caused by the correlation between the chip and the shift of the chip itself. Therefore, self correlation determines multipath interference

11Scrambling

Users who need to send information: UE1, UE2 and UE3UE1 uses c1 for spreading: UE1 c1UE2 uses c2 for spreading: UE2 c2UE3 uses c3 for spreading: UE3 c3c1, c2 and c3 are mutually orthogonal.Information sent: UE1 c1+ UE2 c2+ UE3 c3

12Scrambling VS Spreading

Channels in WCDMA

Physical Channel = information container Transport Channel = characteristics of transmission Logical Channel = specification of the information global content

14Logical Channels

Dedicated Traffic CHannel (DTCH): a point-to-point bi-directional channel, that transmits dedicated user information between a UE and the network. That information can be speech, circuit switched data or packet switched data. The payload bits on this channel come from a higher layer application (the AMR codec for example). Control bits can be added by the RLC (protocol information) in case of a non transparent transfer. The MAC sublayer will also add a header to the RLC PDU. Common Traffic CHannel (CTCH): a point-to-multipoint downlink channel for transfer of dedicated user information for all or a group of specified UEs. This channel is used to broadcast BMC messages. These messages can either be cell broadcast data from higher layers or schedule messages for support of Discontinuous Reception (DRX) of cell broadcast data at the UE. Cell broadcast messages are services offered by the operator, like indication of weather, traffic, location or rate information.The control channels are:Broadcast Control CHannel (BCCH): a downlink channel that broadcasts all system information types (except type 14 that is only used in TDD). For example, system information type 3 gives the cell identity. UEs decode system information on the BCH except when in Cell_DCH mode. In that case, they can decode system information type 10 on the FACH and other important signaling is sent on a DCCH.Paging Control CHannel (PCCH): a downlink channel that transfers paging information. It is used to reach a UE (or several UEs) in idle mode or in connected mode (Cell_PCH or URA_PCH state). The paging type 1 message is sent on the PCCH. When a UE receives a page on the PCCH in connected mode, it shall enter Cell_FACH state and make a cell update procedure.Dedicated Control CHannel (DCCH): a point-to-point bi-directional channel that transmits dedicated control information between a UE and the network. This channel is used for dedicated signaling after a RRC connection has been done. For example, it is used for inter-frequency handover procedure, for dedicated paging, for the active set update procedure and for the control and report of measurements.Common Control CHannel (CCCH): a bi-directional channel for transmitting control information between network and UEs. It is used to send messages related to RRC connection, cell update and URA update. This channel is a bit like the DCCH, but will be used when the UE has not yet been identified by the network (or by the new cell). For example, it is used to send the RRC connection request message, which is the first message sent by the UE to get into connected mode. The network will respond on the same channel, and will send him its temporary identities (cell and UTRAN identities). After these initial messages, the DCCH will be used.

15Physical Channels

In order to carry logical channels, several transport channels are defined. They are:Broadcast CHannel (BCH): a downlink channel used for broadcast of system information into the entire cell.Paging CHannel (PCH): a downlink channel used for broadcast of control information into the entire cell, such as paging.Random Access CHannel (RACH): a contention based uplink channel used for initial access or for transmission of relatively small amounts of data (non real-time dedicated control or traffic data). Forward Access CHannel (FACH): a common downlink channel used for dedicated signaling (answer to a RACH typically), or for transmission of relatively small amounts of data. Dedicated CHannel (DCH): a channel dedicated to one UE used in uplink or downlink.

16Physical Channel

DL Physical Channels

The different physical channels are: Synchronization CHannel (SCH): used for cell search procedure. There is the primary and the secondary SCHs. Downlink. Common Control Physical CHannel (CCPCH): used to carry common control information such as the scrambling code used in DL (there is a primary CCPCH and additional secondary CCPCH). Downlink.Common Pilot CHannels (P-CPICH and S-CPICH): used for coherent detection of common channels. They indicate the phase reference. Downlink.Dedicated Physical Data CHannel (DPDCH): used to carry dedicated data coming from layer 2 and above (coming from DCH). Uplink and Downlink.Dedicated Physical Control CHannel (DPCCH): used to carry dedicated control information generated in layer 1 (such as pilot, TPC and TFCI bits). Uplink and Downlink.Page Indicator CHannel (PICH): carries indication to inform the UE that paging information is available on the S-CCPCH. Downlink.Acquisition Indicator CHannel (AICH): it is used to inform a UE that the network has received its access request. Downlink. High Speed Packet Downlink Shared CHannel (HS-PDSCH): it is used to carry subscribers BE service data (mapping on HSDPA) coming from layer 2. Downlink. High Speed Shared Control Channel (HS-SCCH): it is used to carry control message to HS-PDSCH such as modulation scheme, UE ID etc. Downlink18UL Physical Channel

The different physical channels are: Dedicated Physical Data CHannel (DPDCH): used to carry dedicated data coming from layer 2 and above (coming from DCH). Uplink and Downlink.Dedicated Physical Control CHannel (DPCCH): used to carry dedicated control information generated in layer 1 (such as pilot, TPC and TFCI bits). Uplink and Downlink.Physical Random Access CHannel (PRACH): used to carry random access information when a UE wants to access the network. Uplink.High Speed Dedicated Physical Control CHannel (HS-DPCCH): it is used to carry feedback message to HS-PDSCH such CQI,ACK/NACK. Uplink.

19HO in WCDMA

SHO Description

Softer Hand over Description

Hard Hand over

During hard handover, the UE in the hard handover area disconnects with the original service cell and then establishes connection with a new cell.During handover, the system first establish the link between the RNC and NodeB2, then releases the connection between the UE and NodeB1 (the link between NodeB1 and the RNC remains), and then establishes the connection between NodeB2 and the UE. After that, the link between NodeB1 and RNC is disconnected.During hard handover, there is only one connection between the UE and cell at one time23RRC Connection Set Up

RAB Set UP procedure

RF Analysis approach

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