UMTS channel Element

1. Channel Element (CE) Resource
CE resources are a type of NodeB hardware resource. The number of CEs supported by single NodeB
indicates the channel demodulation capabilities resource of the NodeB. The more CEs a NodeB
supports, the more powerful the channel demodulation and service processing capabilities for serving
the customers. Services at different rates require different numbers of CEs to ensure proper channel
demodulation.
In a RAN, CE resources are managed by both the RNC and NodeB. The NodeB reports its CE capacity to
the RNC. The RNC determines whether to admit a new service based on the number of CEs that need to
be consumed and controls CE resources during CE congestion. This ensures the proper use of CE
resources. The NodeB dynamically manages CE resources and rapidly adjusts the number of CEs that
can be consumed based on the actual service rate. This increases CE resource usage.
A proper use of CE resources increases the number of UEs that can be admitted and improves the
service quality of the admitted UEs.
Basic Channel Element Concepts
CE is a basic unit that measures the channel demodulation capabilities of a NodeB. CEs are classified
into uplink (UL) CEs and downlink (DL) CEs.
 One UL CE needs to be consumed by a UL 12.2 kbit/s voice service (SF = 64) plus 3.4 kbit/s
signaling.
 One DL CE needs to be consumed by a DL 12.2 kbit/s voice service (SF = 128) plus 3.4 kbit/s
signaling.
If only 3.4 kbit/s signaling traffic is carried on a DCH or HSPA channel, one CE still needs to be
consumed. The number of CEs that need to be consumed by services of other types can be calculated
by analogy.
The number of UL and DL CEs supported by a NodeB is determined by the NodeB hardware capabilities
and the licensed CE capacity. The number of UL and DL CEs supported by the NodeB hardware is called
the physical CE capacity. The licensed CE capacity may differ from the physical CE capacity. The
smaller determines the number of CEs that can be used by an operator.
CE is a concept of the NodeB side. On the RNC side, it is called NodeB credit. The RNC performs
admission and congestion control based on the NodeB credit. In the UL, the number of Node credit
resources is twice that of CEs. In the DL, the number of NodeB credit resources equals that of CEs.

2. CE Sharing in a Resource Group
To facilitate baseband resource management, NodeB baseband resources fall into UL and DL resource
groups. The UL and DL resource groups are independent with each other.
 UL Resource Group
UL resource group is a UL resource pool shared on a per-channel basis, more than one cell can be setup
in one UL resource group, One UL resource group can have multiple baseband boards, but one board
can belong to only one UL resource group. CE resources in one UL resource group can be shared by
baseband boards. This means that UEs in a cell in a UL resource group can set up services on any board
in the group. The physical CE capacity of a UL resource group is the total CE capacity of baseband
boards in the group.
 DL Resource Group
Different from a UL resource group, a DL resource group is shared on a per-cell basis. Resources in a DL
resource group are allocated to each baseband board based on cells; one board can be configured to
multiple DL resource groups. DL CE resources for UEs in the same cell can be provided by any baseband
board in the DL resource group. CE resources in one DL resource group can be shared only within a
baseband board.
NodeB CE Capacity Specifications
Typically different baseband boards of a NodeB have their own CE capacity specifications.
For exampled, the detailed CE capacity specifications supported by each type of baseband board, see
the BBU3900 Hardware Description product by Huawei
CE capacity here refers to the number of CEs that can be consumed by UL and DL R99 services and
HSUPA services. It does not include CE resources reserved by the NodeB for common and HSDPA
channels.
Rules for Calculating CE Consumption
The RNC determines the number of CEs required for a service based on the SF that matches the service
rate. When an RAB connection is set up or released for a service, CE resources must be allocated or

3. taken back and the number of CEs must be deducted or added accordingly. Different rules for
calculating CE resource consumption apply to channels or services of different types.
 CE resources reserved by the NodeB for common and HSDPA channels are shown in gray.
 CE resources that need to be consumed by R99 and HSUPA services are shown in pink.
Common Channels CE Consumption
CE resources required on the UL and DL common channels are reserved by the NodeB. Therefore, they
do not occupy the licensed CE capacity. These CEs do not need to be considered in the calculation of
CE consumption.
HSDPA Channels CE Consumption
Similarly, the NodeB reserves CE resources for the high-speed downlink shared channel (HS-DSCH) and
the related control channels if HSDPA is used. These CEs also do not need to be considered in the
calculation of CE consumption.
Note that the signaling of an HSDPA UE that is not performing an R99 service occupies one DCH and
needs to consume one DL CE. If the SRB over HSDPA function is enabled, the signaling of an HSDPA
service does not consume additional CE resources. For an HSDPA UE that is performing an R99 service,
its signaling and the R99 service occupy the same DCH. Therefore, only the CEs consumed on R99
traffic channels need to be calculated.
R99 Service CE Consumption
For an R99 service, the RNC determines the number of CEs and NodeB credit resources that need to be
consumed based on the SF that matches the maximum bit rate (MBR) of the service.
Direction Rate
(kbit/s)
SF Number of
CEs
Consumed
Corresponding
Credits
Consumed
UL 3.4 256 1 2
13.6 64 1 2
8 64 1 2
16 64 1 2
32 32 1.5 3
64 16 3 6
128 8 5 10

4. 144 8 5 10
256 4 10 20
384 4 10 20
DL 3.4 256 1 1
13.6 128 1 1
8 128 1 1
16 128 1 1
32 64 1 1
64 32 2 2
128 16 4 4
144 16 4 4
256 8 8 8
384 8 8 8
HSUPA Service CE Consumption
For an HSUPA service, the RNC determines the number of CEs and NodeB credit resources that need to
be consumed based on the SF that matches the service rate. The RNC determines the SF based on a
certain rate in the following ways:
 If the UL enhanced L2 function is disabled and the NodeB indicates in a private information
element (IE) that dynamic CE resource management has been enabled in the cell, the RNC calculates
the SF based on the larger of the bit rate of one RLC PDU and the guaranteed bit rate (GBR).
o If the UL enhanced L2 function is disabled, the RLC PDU size is fixed. The bit rate of
one RLC PDU is determined by the RLC PDU size and transmission time interval (TTI).
 If the UL enhanced L2 function is enabled and the NodeB indicates in a private IE that dynamic
CE resource management has been enabled in the cell, the RNC calculates the SF based on the larger of
the bit rate of the smallest RLC PDU and the GBR.
o If the UL enhanced L2 function is enabled, the RLC PDU size is flexible. The bit rate of
the smallest RLC PDU is determined by the minimum RLC PDU size and the TTI. The minimum RLC PDU
size can be specified by the RlcPduMaxSizeForUlL2Enhance parameter.
 If the NodeB reports that dynamic CE resource management has been disabled, the RNC
calculates the SF based on the MBR.
 If the NodeB does not report whether dynamic CE resource management has been enabled, the
RNC calculates the SF based on the value of the HsupaCeConsumeSelection parameter and whether the
UL enhanced L2 function is enabled.
o If HsupaCeConsumeSelection is set to MBR, the RNC calculates the SF based on the
MBR.
o If HsupaCeConsumeSelection is set to GBR:
 If the UL enhanced L2 function is disabled, the RNC calculates the SF based on
the larger of the bit rate of one RLC PDU and the GBR.
 If the UL enhanced L2 function is enabled, the RNC calculates the SF based on
the larger of the bit rate of the smallest RLC PDU and the GBR.

5. After determining the SF, the RNC searches the CE consumption mapping listed below
Direction Rate
(kbit/s)
SF Number of
CEs
Consumed
Corresponding
Credits
Consumed
UL 8 64 1 2
16 64 1 2
32 32 1 2
64 32 1 2
128 16 2 4
144 16 2 4
256 8 4 8
384 4 8 16
608 4 8 16
1450 2SF4 16 32
2048 2SF2 32 64
2890 2SF2 32 64
5760 2SF2+2SF4 48 96
CE Consumption of 4-Way Receive Diversity
The use of 4-way receive diversity does not affect DL CE consumption but doubles UL CE consumption.
The use of 4-way receive diversity can be configured by resource group. UL CE consumption of a
resource group doubles if the resource group is configured with 4-way receive diversity. CE
consumption of a common resource group remains unchanged.
examples of CE Consumption
 UE A, which performs a UL 64 kbit/s and DL 384 kbit/s service on the DCH, consumes three UL
CEs and eight DL CEs.
 UE B, which performs a UL 64 kbit/s and DL 1024 kbit/s service on the DCH and HS -DSCH
respectively, consumes three UL CEs and one DL CE if the DL signaling radio bearer (SRB) is carried on
the DCH.
 UE C, which performs a UL 608 kbit/s and DL 1024 kbit/s service on the E-DCH and HS-DSCH
respectively and at the same time performs an AMR speech service, consumes nine UL CEs and one DL
CE.