Discuss forward W-CDMA channel

Forward WCDMA channel can be explained under the following types:

  • Primary Common Control Physical Channel (PCCPCH). This channel continuously broadcasts system identification and access control information.
  • Secondary Common Control Physical Channel (SCCPCH) (downlink) This channel carries the Forward Access Channel (FACH) providing control information, and the Paging Channel (PACH) with messages for UEs (Universal Encoders) that are registered on the network.
  • Physical Random Access Channel (PRACH) (uplink). This channel enables the UE to transmit random access bursts in an attempt to access a network.
  • Dedicated Physical Data Channel (DPDCH) (up and downlink). This channel is used to transfer user data.
  • Dedicated Physical Control Channel (DPCCH) (up and downlink). This channel carries control information to and from the UE. In both directions the channel carries pilot bits and the Transport Format Combination Identifier (TFCI). The downlink channel also includes the Transmit Power Control and FeedBack Information (FBI) bits.
  • Physical Downlink Shared Channel (PDSCH) (downlink). This channel shares control information to UEs within the coverage area of the node B.
  • Physical Common Packet Channel (PCPCH). This channel is specifically intended to carry packet data. In operation the UE monitors the system to check if it is busy, and if not it then transmits a brief access burst. This is retransmitted if no acknowledgement is gained with a slight increase in power each time. Once the node B acknowledges the request, the data is transmitted on the channel.
  • Synchronisation Channel (SCH) The synchronisation channel is used in allowing UEs to synchronise with the network.
  • Common Pilot Channel (CPICH) This channel is transmitted by every node B so that the UEs are able estimate the timing for signal demodulation. Additionally they can be used as a beacon for the UE to determine the best cell with which to communicate.
  • Acquisition Indicator Channel (AICH) The AICH is used to inform a UE about the Data Channel (DCH) it can use to communicate with the node B. This channel assignment occurs as a result of a successful random access service request from the UE.
  • Paging Indication Channel (PICH) This channel provides the information to the UE to be able to operate its sleep mode to conserve its battery when listening on the Paging Channel (PCH). As the UE needs to know when to monitor the PCH, data is provided on the PICH to assign a UE a paging repetition ratio to enable it to determine how often it needs to 'wake up' and listen to the PCH.
  • CPCH Status Indication Channel (CSICH) This channel, which only appears in the downlink carries the status of the CPCH and may also be used to carry some intermittent, or "bursty" data. It works in a similar fashion to PICH.
  • Collision Detection/Channel Assignment Indication Channel (CD/CA-ICH) This channel, present in the downlink is used to indicate whether the channel assignment is active or inactive to the UE.
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